The effect of negative emotional context on neural and behavioural responses to oesophageal stimulation

The effect of negative emotional context on neuraland behavioural responses to oesophagealstimulation

Mary L. Phillips,1 Lloyd J. Gregory,2,4 Sarah Cullen,1 Steven Cohen,2,4 Virginia Ng,2

Christopher Andrew,2 Vincent Giampietro,2 Edward Bullmore,3 Fernando Zelaya,2 Edson Amaro,2

David G. Thompson,4 Anthony R. Hobson,4 Steven C. R. Williams,2 Michael Brammer2 andQasim Aziz2,4

1Division of Psychological Medicine, Guy's, St Thomas'

and King's College School of Clinical Medicine and

Institute of Psychiatry, 2Neuroimaging Research Group,

Institute of Psychiatry, London, 3Department of Psychiatry,

University of Cambridge, Addenbrooke's Hospital,

Cambridge and 4Section of Gastrointestinal Science,

University of Manchester, Hope Hospital, Salford, UK

Correspondence to: Dr Lloyd J. Gregory, GI Sciences,

Clinical Sciences Building, Hope Hospital, Stott Lane,

Salford M6 8HD, UK

E-mail: [email protected]

SummarySensory experience is in¯uenced by emotional context.Although perception of emotion and unpleasant visceralsensation are associated with activation within theinsula and dorsal and ventral anterior cingulate gyri(ACG), regions important for attention to and percep-tion of sensory and emotional information, the neuralmechanisms underlying the effect of emotional contextupon visceral sensation remain unexplored. Using func-tional MRI, we examined neural responses to phasic,non-painful oesophageal sensation (OS) in eight healthysubjects (seven male; age range 27±36 years) either dur-ing neutral or negative emotional contexts produced,respectively, by presentation of neutral or fearful facialexpressions. Activation within right insular and bilat-eral dorsal ACG was signi®cantly greater (P < 0.01)during OS with fearful than with neutral faces. In asecond experiment, we measured anxiety, discomfort

and neural responses in eight healthy male subjects (agerange 22±41 years) to phasic, non-painful OS duringpresentation of faces depicting either low, moderate orhigh intensities of fear. Signi®cantly greater (P < 0.01)discomfort, anxiety and activation predominantly withinthe left dorsal ACG and bilateral anterior insulaeoccurred with high-intensity compared with low-inten-sity expressions. Clusters of voxels were also detected inthis region, which exhibited a positive correlationbetween subjective behaviour and blood oxygenationlevel-dependent effect (P < 0.05). We report the ®rstevidence for a modulation of neural responses, and per-ceived discomfort during, non-painful visceral stimula-tion by the intensity of the negative emotional contextin which the stimulation occurs, and suggest a mechan-ism for the effect of negative context on symptoms infunctional pain disorders.

Keywords: oesophagus; faces; fear; mood; emotion

Abbreviations: ACG = anterior cingulate gyri; BA = Brodmann area; BOLD = blood oxygenation level-dependent;

EPI = echoplanar imaging; fMRI = functional MRI; FPQ = fundamental power quotient; GBAM = generic brain activation

map; GI = gastrointestinal; OS = oesophageal sensation; PCC = posterior cingulate cortex

IntroductionNegative mood states, such as fear or sadness, are often

associated with abnormal sensory perception such as abdom-

inal pain (Chen et al., 1989; Weisenberg et al., 1998).

Beaumont (1833) and Pavlov (1910) demonstrated that

external sensory events eliciting strong emotional reactions

may alter gastrointestinal (GI) function. A close relationship

between emotional state and GI function is repeatedly

reported in patients with functional GI disorders, including

irritable bowel syndrome and non-cardiac chest pain

(Whitehead et al., 1988; Ho et al., 1998).

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DOI: 10.1093/brain/awg065 Brain (2003), 126, 669±684

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There is increasing experimental evidence to suggest an

interaction between emotional context, cognition and sensory

processing. Previous studies have demonstrated that sensory

re¯exes, including the acoustic startle (Kumari et al., 1996;

Kaviani et al., 1999) and eye-blink (Vrana and Lang, 1990)

re¯ex, are modulated by the emotional context in which they

occur. Furthermore, the amplitude of cortical evoked

responses to GI stimulation has been shown to be modulated

by attentional processes (Hollerbach et al., 1997; Hobson

et al., 1998, 2000).

Advances in functional neuroimaging have provided

information about the brain neural networks for emotional,

cognitive and sensory processing. For instance, it has been

demonstrated that human facial expressions (considered to be

the primary source for conveying the emotional valence

regarding a particular situation) depicting different emotions

activate different brain neuronal networks. Fearful facial

expressions activate the amygdala, (Breiter et al., 1996;

Morris et al., 1996; Phillips et al., 1997), while facial

expressions of disgust activate the insular cortex and ventral

striatum (Phillips et al., 1997; Sprengelmeyer et al., 1998).

Functional neuroimaging studies have also demonstrated

activation of the anterior-mid insula and anterior cingulate

gyrus (ACG) during perception of somatic pain (Coghill et al.,

1994; Davis et al., 1997; Derbyshire et al., 1997; Derbyshire

and Jones, 1998; Oshiro et al., 1998; Casey, 1999) and

unpleasant oesophageal sensation (Aziz et al., 1997).

The ventral ACG (including the perigenual and subgenual

regions of the ACG, Brodmann areas 32, rostral 24 and 25) is

considered to be involved in affective processing and is

activated during the assessment of emotional and motiv-

ational information and, with the anterior insula, during

recognition of negative emotions and during depressed states

(Drevets and Raichle, 1998; Phillips et al., 1997, 1998;

Mayberg et al., 1999). The dorsal ACG, including Brodmann

areas (BAs) 24 and 32, is considered to be the cognitive

division, and is activated during cognitively demanding tasks

involving modulation of attention and executive functions

(Bush et al., 2000). The dorsal and ventral ACG, together

with the anterior-mid insulae, are therefore important

components of a neural system mediating attention to and

perception of sensory and emotional information. However,

to date, no study has examined the extent to which an

emotional context modulates the central processing of

visceral sensation.

We wished to examine the effect of presentation of a

negative emotional context upon the intensity of activation

within neural regions important for attention to and percep-

tion of sensory and emotional information, dorsal and ventral

ACG, and anterior insular cortices, during visceral stimula-

tion which would not be perceived as salient in a non-

emotional context: non-painful oesophageal stimulation

(OS). We predicted that altering the emotional context in

which the non-painful OS occurred from neutral to negative

would then be associated with increased attentional and

emotional processing demands, and increased activation in

these neural regions.

In two functional MRI (fMRI) experiments, we employed

fearful and neutral facial expressions from a standardized

series (Ekman and Friesen, 1975) to provide negative and

neutral emotional contexts, respectively, whilst healthy

subjects experienced phasic, non-painful OS. The facial

stimuli have been employed in many previous functional

neuroimaging studies examining neural responses to emo-

tional stimuli (e.g. Morris et al., 1996; Phillips et al., 1997).

In the ®rst experiment, we examined the effect of a negative

emotional compared with a neutral context upon ventral and

dorsal ACG, and insular responses to phasic, non-painful OS.

In a second experiment, we examined the effect of altering

the intensity of the negative emotional context during non-

painful OS upon the level of reported anxiety and discomfort,

and the intensity of activation within these neural regions.

Experiment 1

Material and methodsSubjectsEight healthy volunteers (seven male; mean age: 32 years;

range: 27±36 years; mean number of years of education:

16 years) participated in the study. Subjects reported no

history of neurological, gastrointestinal or psychiatric

disorder and were on no medications at the time of study.

Informed, written consent was obtained after the nature and

possible consequences of the study were explained. Approval

for the study was obtained from the Ethical Committee

(Research) of the Institute of Psychiatry.

Experimental designA traditional box-car design comprising alternating 30 s

blocks of experimental and control stimuli for a duration of

5 min was employed. Either 10 prototypically fearful or 10

neutral facial expressions displayed by eight different iden-

tities (®ve female and three male) from a standardized series

(Ekman and Friesen, 1975) were presented for 2 s each with a

1 s interstimulus interval per 30 s block. The facial stimuli

were presented on a screen placed in front of the subjects in

the scanner by a back projection technique, and subtended

~10° of visual angle vertically and 8° horizontally.

The experiment was a simple 2 3 2 design: with

oesophageal stimulation either on or off, and emotional

context either fearful or neutral. The experiment was divided

into four experimental conditions:

(A) Presentation of fearful faces with phasic, non-painful OS

versus presentation of fearful faces alone thereby generating a

continuous context of fear throughout the condition.

(B) Presentation of fearful faces versus presentation of neutral

faces.

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(C) Presentation of neutral faces with phasic, non-painful

OS versus presentation of neutral faces alone thereby

generating a continuous context of neutrality throughout

the condition.

(D) Presentation of fearful faces with phasic, non-painful OS

versus presentation of neutral faces with phasic, non-painful

OS.

A schematic representation of the experimental design is

shown in Fig. 1.

With this design, subjects participated in two experimental

conditions in which the emotional context was similar but

with additional sensory stimulation in one condition and not

in the other, i.e. presentation of alternating blocks of fearful

and neutral faces with either no OS or phasic OS throughout

the condition (conditions B and D, respectively), and two

experimental conditions in which there were similar amounts

of sensory stimulation but with different emotional contexts,

i.e. periodic, phasic OS with continual presentation of fearful

faces or periodic, phasic OS with continual presentation of

neutral faces (conditions A and C, respectively). The order of

experimental conditions was counterbalanced across subjects

to avoid effects of order.

Fig. 1 The design of the four 5 min experimental conditions in the ®rst experiment: each comprised alternating 30 s blocks of:(A) presentation of 10 fearful faces with phasic, non-painful OS and presentation of 10 fearful faces without OS; (B) presentation of10 fearful faces and presentation of 10 neutral faces without any OS in either block; (C) presentation of 10 neutral faces with phasic,non-painful OS and presentation of 10 neutral faces alone; and (D) presentation of 10 fearful faces with phasic, non-painful OS andpresentation of 10 neutral faces with phasic, non-painful OS. Each facial expression was presented for 2 s. During alternate blocks ofconditions A and C, and both blocks of condition D, a single phasic non-painful balloon distension was delivered to the distal oesophagus1.5 s into the presentation of each facial expression.

Emotions and gut sensation 671


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Oesophageal stimulation was performed by phasic disten-

sion of a 2 cm long silicone balloon with air. The balloon was

mounted 15 mm from the tip of a 4 mm diameter multilumen

polyvinyl catheter (Wilson Cook, Letchworth, UK). Prior to

scanning, the balloon catheter was passed perorally into the

oesophagus, and the balloon positioned 30 cm from the

incisors in the distal oesophagus. The balloon was connected

to a specially constructed pump (Medical Physics

Department, Hope Hospital, Salford, UK), which was capable

of rapid phasic distension. The maximum ¯ow rate produced

by the pump was 200 ml/s and the rise time to maximum

balloon in¯ation remained constant (165 ms) for any given

volume. The balloon volume was controlled using a dial on

the front of the pump, which allowed the pressure in the

system to be regulated [pressure range 0±25 psi (pound force

per square inch)]. Increasing the pressure in the system

increased the ¯ow rate in the airlines and, therefore, a greater

volume was delivered during the in¯ation cycle. In vitro, the

pump was capable of delivering a maximum balloon volume

of 30 ml. The balloon was completely de¯ated immediately

after maximum in¯ation.

To determine sensory and pain thresholds for each

individual, the catheter was connected to the pump and the

balloon was phasically in¯ated, whilst the volume was

increased in a stepwise manner in 1 psi increments. A value,

in psi, representing 50% of the difference between the sensory

and pain threshold was calculated as the volume necessary to

produce a clearly perceptible, but non-painful sensation, in

each subject (Hobson et al., 1998, 2000). In alternate 30 s

blocks in experimental conditions A and C, and for both 30 s

blocks in experimental condition D, a single phasic non-

painful balloon distension was delivered to the distal

oesophagus 1.5 s into each 2 s face presentation, so that

subjects received 10 OS per 30 s block.

Subjects were requested to view the faces carefully in each

experimental condition. At the end of each experimental

condition, subjects were asked to identify the emotion

depicted by the faces.

Image acquisition and analysisGradient echo echoplanar imaging (EPI) data were acquired

on a Neuro-optimized 1.5 T MR system (General Electric,

Milwaukee, WI, USA) at the Maudsley Hospital, London,

UK. A quadrature birdcage headcoil was used for radio

frequency (RF) transmission and reception. A hundred T2*-

weighted images depicting blood oxygenation level-depend-

ent (BOLD) contrast (Ogawa et al., 1990) were acquired over

5 min (for each task) at each of 14 near-axial non-contiguous

7 mm thick planes parallel to the intercommissural (AC±PC)

line: TE (echo time) = 40 ms; TR (repetition time) = 3 s;

matrix size = 64 3 64; FOV (®eld of view) = 240 3 240;

in-plane resolution = 7 mm; interslice gap = 0.7 mm.

This EPI dataset provided almost complete brain coverage.

In the same scanning session, an inversion recovery EPI

dataset was acquired at 43 near-axial 3 mm thick planes

parallel to the AC±PC (anterior±posterior commissure) line:

TE = 80 ms; TI (inversion time) = 180 ms; TR = 16 s; in-plane

resolution = 1.5 mm; interslice gap = 0.3 mm; number of

signal averages = 8. This higher resolution EPI dataset

provided whole brain coverage, and was later used to register

the fMRI datasets acquired from each individual into standard

stereotactic space.

The statistical inferential procedure used in this paper does

not utilize any underlying assumptions about the distribution

of the test statistic (the fundamental power quotient, FPQ),

but instead calculates it from the data itself by previously

described randomization techniques (Ogawa et al., 1990;

Bullmore et al., 1996; Brammer et al., 1997). The data were

®rst realigned (Bullmore et al., 1999a) to minimize motion

related artefacts. Responses to the experimental paradigms

were then detected by time series analysis using a truncated

Fourier series consisting of pairs of sine and cosine terms at

the alternation frequency of the block periodic (A/B)

experimental paradigm and its ®rst two harmonics. Using

this approach, the power and phase of the BOLD responses to

the block periodic (A/B) experimental paradigm (Bullmore

et al., 1996) could be computed. In addition to the sine and

cosine terms, the mathematical model for the response

incorporated an intercept term (image intensity at time

zero) and an estimate of time-dependent signal drift. If the

amplitudes of the sine and cosine components at the stimulus

frequency that gave the best ®t to the observed data at a given

voxel are represented by g and d, the power of periodic

response to the input function is given by {g2+d2}. Dividing

the power by its standard error yields the standardized power

(FPQ) of the response at each voxel. The FPQ is therefore a

measurement of the magnitude or strength of the BOLD

effect at each intracerebral voxel. Parametric maps repre-

senting FPQ observed at each intracerebral voxel were

constructed.

In order to sample the distribution of FPQ under the null

hypothesis that observed values of FPQ were not determined

by experimental design (with minimal assumptions), the time

series at each voxel was permuted randomly and FPQ

estimated exactly as above but using this permuted time

series. This process was repeated 10 times at each voxel and

then over all voxels, resulting in 10 permuted parametric

maps of FPQ at each plane for each subject. Combining this

data yields the distribution of FPQ under the null hypothesis.

Voxels activated any desired level of type 1 error can then be

determined obtaining the appropriate critical value of FPQ

from the null distribution. For example, FPQ values in the

observed data lying above the 99th percentile of the null

distribution have a probability under the null hypothesis of

<0.01. In order to extend inference to the group level, the

observed and randomized FPQ maps were transformed into

standard space and smoothed by a 2D Gaussian ®lter with full

width half maximum = 11 mm. This ®lter size was chosen in

order to accommodate regional differences in brain anatomy

between subjects (Clark et al., 1996).



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Generic brain activation maps (GBAMs)A generic brain activation map (GBAM) was produced for

each experimental condition by testing the median observed

FPQ (median values were used to minimize outlier effects) at

each intracerebral voxel in standard space (Talairach and

Tournoux, 1988) against a critical value of the permutation

distribution for median FPQ ascertained from the spatially

transformed permuted data (Brammer et al., 1997). The

generic neural response of all participating subjects during

each experimental condition was therefore represented by the

corresponding GBAM, with activated regions identi®ed by

reference to the Talairach Atlas (Talairach and Tournoux,

1988). The threshold of P < 0.004 for activation at each

intracerebral voxel was chosen, since this represented a total

number of false positive (Type 1) errors (false positive

activated voxels) of 50 per brain volume (~14 000 voxels),

i.e. two false-positive activated voxels per each of the 25

brain slices comprising the total brain volume following the

transformation of the fMRI data into standardized space. This

threshold therefore ensured a relatively low number not only

of false positive, but also of false negative activated voxels

per total brain volume.

In order to examine the effect of the two factors (OS and

negative emotional context upon ventral and dorsal ACG and

insular responses), average values of the statistic maps were

produced for each subject for both conditions in which OS

was contrasted with no OS (conditions A and C), and for both

conditions in which fearful faces were contrasted with neutral

faces (conditions B and D). Two group images were then

computed from these averaged maps.

Comparison of experimental conditionsIn order to examine the effect of presentation of a negative

emotional context upon neural responses to OS and the effect

of OS upon neural responses to fearful facial expressions, we

estimated the differences in mean FPQ between conditions A

and C, and between conditions D and B, respectively, by

®tting a repeated measures analysis of variance (ANOVA)

model at each voxel of the observed FPQ maps in standard

space: FPQi,j = b0 + bjE + ei,j. Here, FPQi,j denotes

standardized power in the ith individual under the jth

condition, b0 is the overall mean FPQ, b0 + bj is the mean

FPQ under the jth condition, E is a dummy variable coding

condition, and ei,j is a residual quantity unique to the ith

individual. The null hypothesis of zero difference in mean

FPQ between conditions was tested by comparing the

coef®cient bj to critical values of its non-parametrically

ascertained null distribution. To do this, the elements of E

were randomly permuted 10 times at each voxel, bj was

estimated at each voxel after each permutation, and these

estimates were pooled over all intracerebral voxels to sample

the permutation distribution of bj (Bullmore et al., 1999b).

For a two-tailed test of size P = 0.05, the critical values were

the 100 3 p/2th and 100 3 (1 ± p/2)th percentile values of the

permutation distribution. Differences in mean FPQ between

conditions were tested for signi®cance only at those voxels,

which were generically activated by one or both of the

conditions considered independently, thereby substantially

reducing the search volume or number of tests conducted.

ResultsAll subjects tolerated the study well. Oesophageal sensation

was perceived as a pulsatile sensation over the sternum. The

mean (6SD) value for balloon intensity was 18 psi 6 5.75.

After scanning, all subjects were able to identify correctly

facial expressions viewed during the experimental conditions

as either fearful or neutral.

Generic brain activation maps of neuralresponses to OS and fearful facial expressionsThe mean GBAMs of conditions A and C, and of conditions B

and D, demonstrating neural responses to OS compared with

no OS, and to fearful compared with neutral faces are shown

in Fig. 2A and Fig. 2C, respectively. The comparison of

GBAMs for conditions A and C, demonstrating neural

regions activated to a signi®cantly greater extent when

fearful than when neutral faces were presented during OS, is

shown in Fig. 2B. The comparison of GBAMs for conditions

B and D, demonstrating neural regions activated to a

signi®cantly greater extent when fearful faces were presented

without OS than when OS occurred during presentation of

fearful faces, is shown in Fig. 2D.

Conditions A and C: overall effect of OS versusno OSActivation was demonstrated within bilateral dorsal and

ventral ACG, and bilateral mid-insulae, in addition to the

right hippocampus, bilateral cerebellum, occipitotemporal

cortical regions, and dorsolateral and ventral prefrontal

cortices (Table 1A and Fig. 2A).

Conditions B and D: presentation of fearfulfaces versus presentation of neutral facesActivation was demonstrated within bilateral ventral and left

dorsal ACG, and the left hippocampus, in addition to bilateral

cerebellum, occipitotemporal cortical regions, bilateral thal-

amus, left dorsolateral and right ventral prefrontal cortices

(Table 1B and Fig. 2C).

Comparison of conditions A and C: the effect ofpresentation of fearful faces upon neuralresponses to OSSigni®cantly greater activation was demonstrated within the

dorsal region of the left ACG during condition A than during



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condition C (x = ±3, y = ±8, z = 42; number of activated

voxels = 31 in this region; Table 1C). No regions were

activated to a signi®cantly greater extent during condition C

than condition A (P = 0.01; overall search

volume = 3530 voxels; expected number of false positive

activated voxels over the whole brain = 35; number of

observed activated voxels = 62; Table 1C and Fig. 2B).

Comparison of conditions D and B: the effectof OS upon neural responses to fearful facialexpressionsSigni®cantly greater activation was demonstrated within the

right hippocampus during condition B than during condition

D (x = 17, y = ±33, z = ±7; number of activated voxels = 14;

Table 1C). No regions were activated to a signi®cantly

greater extent during condition D than condition B (P = 0.01;

overall search volume = 1120 voxels; expected number of

false positive activated voxels over the whole brain = 11;

number of observed activated voxels = 43; Table 1C and

Fig. 2D).

These ®ndings allowed us to design a second experiment to

test the hypothesis that increasing the intensity of negative

emotional context in which OS occurred would be associated

with increased activation predominantly within dorsal ACG.

Experiment 2

MethodsSubjectsEight healthy, right-handed male volunteers (median age:

22 years; age range: 22±41 years; mean number of years in

education: 16 years) participated in the study. Subject

exclusion criteria and the method for obtaining informed

consent were as described in Experiment 1.

Experimental designA modi®ed box-car design was employed in this experiment,

comprising alternating 20 s `active' blocks of presentation of

fearful faces and non-painful OS versus fearful faces without

OS, with each of these 20 s blocks preceded by a 16 s period

of silence (see below). In order to modulate the emotional

context during this study, prototypical expressions of fear

from a standardized series (Ekman and Friesen, 1975) were

morphed with prototypically neutral expressions from the

same series to create facial expressions depicting two lower

intensities of fear in addition to prototypical or high intensity

fear: moderate intensity fear (50% fear and 50% neutral) and

mild intensity fear (25% fear and 75% neutral; Young et al.,

2002). In each of three conditions, therefore, either ten 100%

Fig. 2 Generic brain activations are shown for the eight subjects participating in the ®rst experiment representing: (A) the mean neuralresponse to conditions A and C; (B) the mean neural response to conditions B and D; (C) the comparison of neural responses duringconditions A and C, demonstrating regions activated to a signi®cantly greater extent when fearful than when neutral faces were presentedduring non-painful OS; and (D) the comparison of neural responses during conditions B and D, demonstrating regions activated to asigni®cantly greater extent when fearful faces were presented without OS than when non-painful OS occurred during presentation offearful faces. Brian slices are shown at 4 mm and 37/42 mm above the transcallosal plane. The right side of the brain is shown on the leftside of the picture for each brain slice, and vice versa. In A, major regions of activation are demonstrated in the insula and, in A and B,within a dorsal region of the anterior cingulate gyrus. In C, major regions of activation are demonstrated predominantly within bilateraloccipitotemporal regions (BA 18 and 31) and, in C and D, within the hippocampus.



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fearful, ten 50% intensity fearful, or ten 25% intensity fearful

facial expressions were displayed by eight different identities

(®ve female and three male), each presented for 2 s, in each of

the 20 s blocks. During the 20 s active blocks, facial stimuli

were presented and distal oesophageal non-painful stimula-

tion was performed as described in Experiment 1.

Table 1A Major brain regions activated by non-painful OS (conditions A and C)

Cerebral region Side x* y* z* BA FPQ Size

Cerebellum R 7 ±50 ±2 2.1 167L ±17 ±67 ±7 2.1 225

Occipitotemporal regions:Precuneus R 4 ±56 42 7 1.9 137Cuneus R 4 ±73 9 17 1.9 101

L ±11 ±76 15 18 1.8 38Superior temporal gyrus R 36 ±4 ±7 38 1.9 71

L ±50 ±7 9 22 1.9 93Middle temporal gyrus R 53 ±39 4 21 1.8 16

L ±43 ±60 26 39 1.8 73Posterior cingulate gyrus R 7 ±46 15 31 1.9 57Insula (middle) R 40 ±7 ±2 1.8 78

L ±43 0 4 2.0 73Anterior cingulate gyrus (ventral) R/L 0 39 ±7 32 2.7 63Anterior cingulate gyrus (dorsal) R/L 0 33 31 32 1.8 19

L ±4 33 26 32 1.8 42±4 26 37 32 1.6 11

Hippocampus R 36 ±4 ±13 1.7 48Dorsolateral prefrontal cortex L ±43 7 20 44 1.8 33Ventromedial prefrontal (orbitofrontal) cortex R 11 43 ±13 11 2.1 19

*Talairach co-ordinates refer to the voxel with the maximum FPQ in each cluster. All such voxels were identi®ed by a one-tailed test ofthe null hypothesis that median FPQ is not determined by experimental design. The probability threshold for activation was P < 0.004.L = left; R = right.

Table 1B Major brain regions activated during presentation of fearful faces (conditions B and D)


Cerebellum R 25 ±46 ±13 1.8 37L ±36 ±63 ±13 2.4 109

Thalamus R 4 ±26 4 1.8 57L ±4 ±17 9 1.6 10

Occipitotemporal regions:Posterior cingulate gyrus R 7 ±46 42 31 1.7 44

L ±32 ±17 42 18 1.6 62Fusiform gyrus R 21 ±46 ±7 37 1.8 37Precuneus L ±4 ±67 37 7 1.6 21Superior temporal gyrus L ±50 ±30 15 42 1.7 16Lingual gyrus R 4 ±60 4 18 1.6 14Middle temporal gyrus R 43 0 ±18 21 1.6 11Anterior cingulate gyrus (dorsal) L ±4 26 31 32 1.6 18Anterior cingulate gyrus (ventral) R 7 43 9 32 1.6 10

L ±7 46 4 32 1.6 15Dorsolateral prefrontal cortex L ±40 7 31 44 1.6 16Ventromedial prefrontal cortex R 11 46 ±7 10 1.6 9Hippocampus L ±25 ±43 ±2 1.5 8

*Footnote as for Table 1A.

Table 1C Major brain regions activated signi®cantly more by condition A than C, and by B than D

Cerebral region Side x* y* z* BA FPQ Size Comparison

Anterior cingulate gyrus (dorsal) L ±3 ±8 42 24 2.0 31 A>CHippocampus R 17 ±33 ±7 1.1 14 B>D

*Talairach co-ordinates refer to the voxel with the maximum FPQ in each cluster. Regions activated signi®cantly more in A comparedwith C, and B than D are demonstrated (P = 0.01). L = left; R = right.



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During the 16 s periods preceding the 20 s active blocks,

subjects were asked to rate on a visual analogue scale

(ranging from 1±8) the following:

(i) Oesophageal discomfort experienced during the preceding

20 s block (1 = slight, 8 = severe).

(ii) Anxiety experienced in the preceding 20 s block (1 = little

and 8 = much).

(iii) The intensity of fear in the facial expressions displayed in

the previous 20 s block (1 = very mild; 8 = very intense).

These three questions were presented on the screen in front

of subjects, and the selection was made using an analogue

button box underneath the subject's right hand. Two buttons

were employed to move a cursor in each direction of the scale

in order to prevent too much movement.

Subjects therefore participated in three experimental

conditions, each having a duration of 6 min and 30 s:

(1) Presentation of facial expressions of high intensity (100%)

fear with phasic, OS versus presentation of the fearful faces

alone.

(2) Presentation of facial expressions of fear of moderate

(50%) intensity, with phasic, OS versus presentation of the

fearful faces alone.

(3) Presentation of facial expressions of fear of mild (25%)

intensity, with phasic, OS versus presentation of the fearful

faces alone.

A schematic representation of the experimental design is

shown in Fig. 3.

With this design, subjects participated in three experimen-

tal conditions in which the degree of sensory stimulation was

the same over all conditions, but the intensity of the

emotional was increased from mild (condition 3) to moderate

(condition 2) to high intensity of fear (condition 1).The order

Fig. 3 The design of the three 6.5 min experimental conditions in the second experiment. Each comprised alternating 36 s blocks: 16 s ofsilence, followed by a 20 s active block in which subjects viewed 10 facial expressions, each for 2 s. In all but the ®rst 16 s silent period,subjective ratings (SR) of anxiety, perceived discomfort and intensity of fear in the facial expressions viewed in the preceding 20 s blockwere obtained. In the three conditions, subjects viewed either (1) facial expressions of high intensity (100%) fear with phasic, non-painfulOS versus presentation of the fearful faces alone; (2) facial expressions of fear of moderate (50%) intensity, with phasic, non-painful OSversus presentation of the fearful faces alone; or (3) facial expressions of fear of mild (25%) intensity, with phasic, non-painful OS versuspresentation of the fearful faces alone. Phasic non-painful balloon distension was delivered to the distal oesophagus in the same manner asin the ®rst experiment during alternate blocks in all three conditions.



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of experimental conditions was counterbalanced across

subjects to avoid effects of order

AcquisitionParameters for fMRI data acquisition were as described for

Experiment 1. During the active 20 s blocks, 10 whole brain

image volumes were collected with TR = 2 s. During the 16 s

of silence preceding the 20 s active blocks, brain water

magnetization was maintained in equilibrium (steady state)

by delivering spatially selective RF pulses at the same rate as

that with which the images were collected (every 2 s). To

minimize the background acoustic noise, these RF pulses

were delivered whilst the frequency encoding gradient (read

gradient) was turned off. This was performed because the

`read gradient' is the one that is primarily responsible for the

scanner noise, as it is played almost at full amplitude during

acquisition. The ®rst 4 s of each 16 + 20 s period was a period

of total silence during which the scanner operation was

interrupted. Sixteen near-axial images were collected for each

brain volume (thickness = 7 mm, inter-slice gap = 0.7 mm, in-

plane resolution = 3.75 mm). A hundred brain volumes were

collected in total, and the acquisition time of the entire

paradigm was 6 min 30 s.

AnalysisSubjective ratingsA Friedman test and post hoc Wilcoxon signed ranks tests

were performed in order to determine the effect of experi-

mental condition upon subjective ratings of perceived

anxiety, discomfort and the intensity of fear in the facial

expressions displayed in each of the ten 20 s blocks for each

of the three experimental conditions.

fMRI data analysesIn order to determine the overall effect of OS and fearful

context, we obtained individual GBAMs for each of the three

conditions (as described for Experiment 1) and then com-

puted average values of the three statistic maps for each

subject. A group image from these averaged maps was used to

create a mean GBAM to demonstrate neural responses to OS

compared with no OS during presentation of fearful facial

expressions for all three conditions. We then examined the

relationship between subjective ratings and generic power of

response (mean FPQ) at each voxel by calculating the

Pearson product moment correlation coef®cients between

these parameters. Observed correlation coef®cients were

tested against the null distribution obtained by randomizing

subjective ratings 10 times at each voxel and recalculating the

above correlation coef®cients. Combining these data across

all voxels yields an estimate of the distribution of the

correlation coef®cient under the null hypothesis. Using

critical values of the correlation coef®cient calculated from

this distribution, voxels exhibiting correlation coef®cients

with a cluster-wise probability under the null hypothesis of

<0.05 were identi®ed and reported here (Bullmore et al.,

1999b).

To determine the effect of increasing the intensity of fear

upon generic neural responses to presentation of fearful faces

and OS, we ®tted an analysis of covariance model at each

intracerebral voxel of the individual standardized power maps

after their co-registration in standard (Talairach) space, as

described in Experiment 1, for the following contrasts:

condition 1 versus condition 2; condition 1 versus condition 3;

and condition 2 versus condition 3.

ResultsSubjective ratings of anxiety and discomfortDuring presentation of expressions of mild, moderate and

high intensity fear, mean ratings (and standard deviations)

across all subjects were: anxiety 1.5 (60.78), 1.7 (60.9) and

2.5 (61.2), respectively; perceived discomfort 2.6 (61.8),

2.7 (62.0) and 3.9 (62.0), respectively; and intensity of fear

displayed in the facial expressions 1.7 (61.0), 2.9 (61.4) and

5.3 (62.3), respectively. There was a signi®cant effect

overall of experimental condition upon subjective ratings of

anxiety (P < 0.0001), discomfort (P < 0.028) and the intensity

of fear displayed in the preceding facial expressions

(P < 0.0001), with:

(i) anxiety being signi®cantly higher during presentation of

high compared with either moderate (P < 0.0001) or mild

(P < 0.0001) intensity fearful facial expressions;

(ii) perceived discomfort being signi®cantly higher during

presentation of high compared with either moderate

(P = 0.002) or mild (P < 0.036) intensity fearful facial

expressions; and

(iii) ratings of fear intensity signi®cantly higher for high

compared with either moderate (P < 0.0001) or mild

(P < 0.0001) intensity fearful facial expressions.

Generic brain activation maps of neuralresponses to OS occurring during presentationof facial expressions of mild, moderate and highintensities of fearThe mean GBAM for all three conditions, demonstrating

neural responses to OS compared with no OS during

presentation of fearful facial expressions is shown in

Fig. 4A. Correlational analyses between mean FPQ and

subjective ratings are described below. The comparisons of

GBAMs for conditions 1 and 3, 1 and 2, and 2 and 3

(demonstrating neural regions activated to a signi®cantly

greater extent in response to high compared with mild-

intensity, high compared with moderate intensity, and

moderate compared with mild intensity fearful expressions,

respectively) are shown in Fig. 4B±D.



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Overall effect of non-painful OS versus no OSin a fearful contextActivation was demonstrated within the right dorsal ACG,

and bilateral insulae, in addition to bilateral cerebellum and

occipitotemporal cortical regions (Table 2A and Fig. 4A).

Correlational analysesMean FPQ correlated positively (P < 0.05) with subjective

anxiety ratings within three clusters within right dorsal

cingulate gyrus (x = 8, y = ±14, z = 39, number of voxels = 59)

and bilateral posterior cingulate gyri (x = ±10, y = ±29, z = 36;

x = 17, y = ±33, z = 20; number of voxels = 20 and 18,

respectively), with subjective discomfort ratings in two

clusters within right lingual gyrus (x = 19, y = ±59, z = ±1,

number of voxels = 96) and right posterior cingulate gyrus

(x = 13, y = ±40, z = 42; number of activated voxels = 14), and

with subjective ratings of fear intensity in right lingual gyrus

(x = 26, y = ±76, z = ±1).

Comparison of GBAMs for the three conditionsMajor regions activated to a signi®cantly greater extent

during presentation of facial expressions of high compared

with mild intensity fear were demonstrated within the dorsal

region of the left ACG and bilateral anterior insulae, in

addition to bilateral dorsolateral prefrontal cortices. Few

regions activated to a signi®cantly greater extent in response

to expressions of mild compared with high intensity fear.

These included the left cerebellum and right posterior but not

anterior insula (P = 0.01; overall search volume = 2222

voxels; expected number of false positive activated

voxels = 22; number of observed activated voxels = 9;

Table 2B and Fig. 4B).

Major regions activated to a signi®cantly greater extent

during presentation of expressions of high compared with

moderate intensity fear were demonstrated within the left

dorsal and right ventral ACG and right anterior insula, in

addition to bilateral dorsolateral and ventromedial prefrontal

cortices. Regions activated to a signi®cantly greater extent in

response to facial expressions of moderate compared with

high intensity fear included bilateral cerebellum, left

hippocampus and left posterior but not anterior insula

(P = 0.01; overall search volume = 4145 voxels; expected

number of false positive activated voxels = 41; number of

observed activated voxels = 219; Table 2C and Fig. 4C).

Major regions activated to a signi®cantly greater extent

during presentation of expressions of moderate compared

Fig. 4 Generic brain activations are shown for the eight subjects participating in the second experiment representing: (A) the mean neuralresponse to all three conditions; (B) the comparison of neural responses during conditions 1 and 3; (C) during conditions 1 and 2; and(D) during conditions 2 and 3, demonstrating, respectively, regions activated to a signi®cantly greater extent in response to high comparedwith mild intensity, high compared with moderate intensity, and moderate compared with mild intensity fearful expressions. Brain slicesare shown at 31 and 37 mm above the transcallosal plane in A, and at 37 and 42 mm above the transcallosal plane in B±D. The rightside of the brain is shown on the left side of the picture for each brain slice, and vice versa. In A±C, major regions of activation areshown in the dorsal anterior cingulate gyrus. This region was not activated to a signi®cantly greater extent in the comparison of conditions2 and 3 (D).



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with mild intensity fear were demonstrated bilaterally within

posterior but not anterior insula, middle temporal gyrus,

cerebellum and the left hippocampus. Only the left cerebel-

lum was activated to a signi®cantly greater extent in response

to expressions of mild compared with moderate intensity fear

(P = 0.01; overall search volume = 3985 voxels; expected

number of false positive activated voxels = 39; number of

observed activated voxels = 199; Table 2D and Fig. 4D).

Table 2A Major brain regions activated by non-painful OS in a fearful context (conditions 1, 2 and 3)


Cerebellum R 21 ±63 ±18 2.0 402L ±25 ±56 ±29 1.8 32

Occipitotemporal regions:Superior temporal gyrus R 47 ±7 4 22 2.0 103

L ±53 ±4 9 22 2.1 120Middle temporal gyrus R 53 ±13 ±7 21 1.9 69

L ±53 ±17 ±7 21 1.9 85Lingual gyrus L ±4 ±76 4 18 1.8 70Precuneus L ±7 ±69 42 18 1.8 47Cuneus R 7 ±73 31 19 1.7 33

L ±4 ±73 9 17 1.7 30Posterior cingulate gyrus R 4 ±50 9 30 1.6 14

L ±17 ±60 15 31 1.6 26Fusiform gyrus L ±50 ±13 ±24 20 1.7 26Inferior temporal gyrus L ±43 ±17 ±29 20 1.8 25Insula R 40 ±7 9 2.1 90

L ±43 ±4 ±2 2.1 76Anterior cingulate gyrus (dorsal) R 4 10 31 24 1.5 11

*Footnote as for Table 1A.

Table 2B Major brain regions activated by OS with facial expressions of high compared with mild intensity fear


High>mild:Anterior cingulate gyrus (dorsal) L ±3 22 42 32 1.4 12Dorsolateral prefrontal cortex R 29 25 15 45 1.4 6

L ±32 22 15 45 1.2 4Anterior insula R 29 25 9 1.5 6

L ±29 22 9 1.2 6Mild>high:

Cerebellum L ±23 ±44 ±35 1.4 7Posterior insula R 38 ±8 15 1.2 5

*Talairach co-ordinates refer to the voxel with the maximum FPQ in each cluster. P < 0.01 for comparison of generic activation in thetwo conditions. L = left; R = right.

Table 2C Major brain regions activated by OS with facial expressions of high compared with moderate intensity fear


High>moderate:Dorsal prefrontal cortex R 29 28 15 45 1.6 10Anterior cingulate gyrus (ventral) R 3 36 ±2 24 1.5 9Anterior cingulate gyrus (dorsal) L ±3 22 42 32 1.3 7Anterior insula R 29 25 9 1.4 9Ventromedial prefrontal cortex R/L 0 36 ±13 11 1.2 6

Moderate>high:Cerebellum R 6 ±36 ±18 1.1 18

L ±3 ±58 ±13 1.1 7Posterior insula L ±43 ±3 ±7 1.1 14Hippocampus L ±29 ±17 ±7 1.1 5

*Footnote as for Table 2B.



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DiscussionWe report the ®rst demonstration of a signi®cant effect of a

negative emotional context upon subjective and neural

responses to phasic, periodic non-painful OS. In the ®rst

experiment, we demonstrated that whilst the two factors, OS

and presentation of fearful facial expressions were each

associated with activation within dorsal and ventral ACG,

there was a signi®cant interaction between these factors.

Speci®cally, there was a signi®cant effect of negative

emotional context upon neural responses during OS, with

the dorsal region of the left ACG activated to a signi®cantly

greater extent during OS in a negative emotional context

(condition A) than during OS in a neutral context

(condition C). In contrast, there was no signi®cant effect of

the addition of OS upon neural responses to a negative

emotional context (fearful facial expressions) i.e. the contrast

of conditions D and B).

In the second experiment, we investigated the effect of

altering the intensity of fearful facial expressions upon neural

responses to phasic, periodic non-painful OS. We demon-

strated that, whilst OS occurring in a negative emotional

context per se was associated with activation within the

dorsal ACG and bilateral insulae, signi®cantly greater

activation was demonstrated within the dorsal ACG and the

anterior insula during a high intensity than during either a

mild or moderate intensity negative context. However, there

was no signi®cant difference in activation within these

regions during the moderate and mild intensity negative

contexts. In this experiment, we were also able to demonstrate

increased subjective ratings of anxiety and perceived dis-

comfort with increased intensity of the negative emotional

context, and a positive correlation between subjective ratings

of anxiety and the intensity of dorsal cingulate gyral

activation.

We also observed a positive correlation between both

anxiety and discomfort ratings with activation of the posterior

cingulate cortex (PCC). Activation of PCC has been reported

in several previous studies of somatic pain; its role, however,

remains uncertain. It is clear that it is more reproducible

activated when using a phasic rather than tonic stimulus

(Derbyshire, 2000). Gelnar and colleagues reported activation

of PCC in response to thermal pain and suggested that this

region, lying between the mid-cingulate motor area and

caudal visuospatial region, is a somatosensory area that

receives direct nociceptive projections from the spinothala-

mic tract (Gelnar et al., 1999).

The consistent ®nding from both experiments was a

signi®cant increase in activation within dorsal ACG with

increasing intensity of the negative emotional context in

which constant intensity, non-salient (non-painful) visceral

stimulation occurred, whereas the ®ndings from the ®rst

experiment indicate no signi®cant effect of the addition of OS

upon neural responses to a constant intensity negative

emotional context (condition D). Together, these ®ndings

suggest a modulatory effect of emotional context upon the

dorsal ACG response to OS rather than a simple additive

effect of emotional context and OS upon the response in this

region.

Whilst the role of the dorsal region of the ACG in

the modulation of attention and executive functions has

been highlighted previously (Bush et al., 2000), there is

also increasing evidence for the role of this region in the

processing of emotionally salient information. Cingulotomy,

involving lesions to this region, has been demonstrated to be a

successful treatment for patients with major affective and

anxiety disorders (Ballantine et al., 1967; Cosgrove and

Rauch, 1995) and chronic pain disorders (Devinsky et al.,

1995). Increased regional cerebral blood ¯ow to rostral and

dorsal regions of the ACG has been reported during attention

to subjective emotional states and experiences (Lane et al.,

1997, 1998; Gusnard et al., 2001). These ®ndings indicate

that the dorsal anterior cingulate gyrus is important for the

direction of attention to internal emotional and sensory states.

In the second experiment, the anterior insula was activated

to a signi®cantly greater extent during presentation of high

compared with either moderate or mild intensity fearful facial

expressions. Functional brain imaging studies have also

highlighted the importance of the anterior insula in mediating

Table 2D Major brain regions activated by OS with facial expressions of moderate compared with mild intensity fear


Moderate>mild:Posterior insula R 40 ±3 ±7 1.0 7

L ±43 ±11 ±2 1.0 19Middle temporal gyrus R 38 ±6 ±24 21 1.0 11

L ±46 ±11 ±13 21 1.0 5Cerebellum R 12 ±39 ±18 1.0 9

L ±26 ±47 ±35 1.4 11Hippocampus L ±29 ±17 ±7 1.1 9

Mild>moderate:Cerebellum L ±26 ±47 ±35 1.4 11

*Footnote as for Table 2B.



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negative emotions (Phillips et al., 1997, 1998; Drevets and

Raichle, 1998; Mayberg et al., 1999) and, with the dorsal

ACG, in the response to painful and non painful visceral

(Silverman et al., 1997; Aziz et al., 2000; Mertz et al., 2000)

and painful somatic sensation (Coghill et al., 1994; Vogt

et al., 1996; Davis et al., 1997; Derbyshire et al., 1997;

Derbyshire and Jones, 1998; Casey, 1999).

The insular cortex is also an important area for coordinat-

ing visceral sensory and motor information and is involved in

autonomic regulation (Augustine, 1996). It has a crude

viscerotopic representation for the gastrointestinal and

cardiovascular afferents (Cechetto and Saper, 1987, 1990).

Functional mapping studies of the insula cortex using

intracortical electrodes in patients with temporal lobe

epilepsy have shown that the posterior/mid insula region is

part of a somesthetic network involved in processing painful

and non-painful somatic sensation (Ostrowsky et al., 2000).

In contrast, stimulation of the anterior insula in the same

subjects elicited viscerosensory and visceromotor responses

indicating that the anterior insulaÐwith its dense projections

to the piriform cortex, orbitofrontal cortex, hippocampus and

amygdalaÐis part of a visceral network (Ostrowsky et al.,

2000). Activation of the insular cortex is observed routinely

in functional brain imaging studies of visceral sensation, with

the anterior insula being activated more intensely in response

to noxious visceral stimulation in comparison to non-noxious

stimulation (Aziz et al., 1997, 2000; Aziz and Thompson,

1998). Activation of the anterior insular cortex is also noted in

studies of somatic pain especially when accompanied by a

strong emotional response (Hsieh et al., 1995; Rainville et al.,

2001) and lesions of the anterior insula have been shown to

reduce the affective response to pain (Berthier et al., 1988). In

addition, animal studies have shown afferents from the

anterior insula project to ventral and dorsal regions of the

anterior cingulate cortex (Augustine, 1996). These data

support our ®ndings that anterior insula and dorsal cingulate

play an important role in processing and modulating visceral

sensation and that these regions may belong to a more

extensive cortical network involved in integrating emotional

and visceral information.

Our ®ndings from both experiments indicate that presen-

tation of a negative emotional context during experience of

otherwise non-painful visceral stimulation is associated with

activation within neural regions important for performance of

attentional tasks, and for attention to internal emotional and

sensory states. This activation increases with greater intensity

of the negative context. We have further demonstrated in the

second experiment that subjective experiences of anxiety and

discomfort during non-painful OS also increase with greater

intensity of the negative context. Taken together, these

®ndings indicate that when non-painful visceral stimulation,

otherwise associated with low attentional and emotional

processing demands, occurs in an increasingly negative

context, attentional and emotional processing demands

increase, with corresponding increases in subjective anxiety

and perceived discomfort, and activation within neural

regions important for attentional and emotional processing.

In the ®rst experiment, there was no signi®cant increase in

activation within the dorsal ACG and anterior insula when

continual phasic, non-painful OS occurred during presenta-

tion of alternating blocks of fearful and neutral faces

(condition D) than when presentation of the faces occurred

in the absence of OS (condition B). One possibility is that

attenuation of response may have occurred within regions

important for visceral sensory perception during condition D,

so that signi®cant increases in activation with the dorsal ACG

and anterior insula were not demonstrated in this condition

compared with condition B. Indeed, in condition D, subjects

experienced phasic, non-painful OS on 100 occasions

throughout the 5 min period. Previous studies have indicated

that attenuation of the cortical evoked response to oesopha-

geal stimulation occurs during continuous stimulation runs

consisting of greater than 50 stimuli at a time. (Hobson et al.,

1998). Alternatively, continual rather than episodic presen-

tation of fearful faces throughout the experimental condition

may be required to increase attentional and sensory pro-

cessing demands during otherwise non-salient visceral

stimulation.

We demonstrated a signi®cant effect of experimental

condition upon activation within ventral ACG in the second

experiment during OS occurring in high versus moderate

intensity fearful expressions, but not during OS occurring in

high versus mild intensity fearful expressions. In contrast, we

did not demonstrate a signi®cant effect of experimental

condition upon activation within ventral ACG in the ®rst

experiment. Ventral (perigenual and subgenual) regions of

the ACG have been associated with the experience of

negative emotional states (Drevets and Raichle, 1998;

Mayberg et al., 1999) and emotion perception (Bush et al.,

2000). In the second experiment, we were able to demonstrate

that increasing the intensity of fear displayed by facial

expressions viewed by subjects during OS resulted in

signi®cant increases in the experience of oesophageal

discomfort and anxiety. However, viewing faces depicting

negative emotional expressions has not been considered to be

an adequate method of inducing emotional states in previous

functional neuroimaging studies. Instead, other methods, for

example, recollection of autobiographical memories, have

been employed (Mayberg et al., 1999). It is possible,

therefore, that a more persistent change in emotional state

resulting from the use of mood induction paradigms may

further modulate the intensity of subjective anxiety and

would lead to the induction of negative mood and more robust

activation within ventral ACG.

Other regions activated in response to periodic, OS and to

presentation of fearful faces per se in the ®rst experiment

included dorsolateral and ventral prefrontal cortices, regions

associated, respectively, with performance of cognitively-

demanding and decision-making tasks (e.g. Bechara et al.,

1998). In both experiments, activation within occipitotem-

poral cortical regions was demonstrated in response to



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periodic, OS occurring in fearful contexts, and, in the ®rst

experiment, in response to presentation of fearful faces. In the

second experiment, we also observed a positive correlation

between subjective rating of fear intensity and right lingual

gyrus activation. In previous studies, greater activation within

occipitotemporal cortex has been demonstrated in response to

emotionally salient than to neutral visual stimuli (e.g. Lang

et al., 1998; Taylor et al., 2000). Our ®ndings therefore

suggest that the combination of non-painful OS and presen-

tation of fearful faces was perceived as more salient than

fearful faces alone, whilst fearful faces per se were perceived

as more salient than neutral faces. There was, however, no

consistent increase in activation within either prefrontal or

occipitotemporal cortical regions in response to increasing

the intensity of the negative emotional context in which

periodic, OS occurred in the second experiment.

In the ®rst experiment, periodic, OS and presentation of

fearful faces per se were both associated with activation

within the hippocampus. These ®ndings are consistent with

those of previous studies in which activation within the

hippocampus has been reported in response to negative

emotional visual and auditory stimuli (e.g. Phillips et al.,

1998) and with the postulated role of this region as a

comparator to match or compare novel, including emotion-

ally-salient, stimuli (e.g. fearful faces or OS) with a stored

template of previously-processed, familiar stimuli (e.g.

neutral faces or no OS; Gray, 1982). The hippocampus was

also activated to a signi®cantly greater extent in response to

presentations of fearful contrasted with neutral faces

(condition B) alone than to presentation of these facial

expressions with continuous OS (condition D). This ®nding is

suggestive of an attenuated neural response to novelty during

condition D, as discussed previously.

In this study, we were interested in examining the effect of

presentation of a negative emotional context upon neural

responses to visceral stimulation. Another possibility for

future studies is to examine the effect of increasing arousal

per se upon neural responses to visceral stimulation by

presentation of a novel rather than speci®cally negative

context upon responses to visceral stimulation, using facial

expressions depicting other negative and positive emotions.

ConclusionsTo date, there has been little investigation of the relationship

between the type of emotional context in which sensory

stimulation occurs and the extent of activation in brain

regions such as the dorsal ACG and anterior insula that

mediate attention, sensory perception and emotions. We

report the ®rst evidence for a modulatory effect of emotional

context upon the extent of activation within these regions and

subjective reports of anxiety and discomfort during phasic,

non-painful visceral stimulation. The ®ndings of this study

may provide some insight into the potential importance of

emotional context in the management and treatment of

functional gastrointestinal disorders such as irritable bowel

syndrome and non-cardiac chest pain.

AcknowledgementsQ.A., S.C. and funding for this project were supported by the

Medical Research Council (UK). A.H. is funded by the Lord

Dowding Fund for Humane Research.

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Received June 25, 2002. Revised September 19, 2002.

Accepted September 21, 2002



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The effect of negative emotional context on neural and behavioural responses to oesophageal stimulation

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