Martha Bridge Denckla, MD. May 4, 2012. Colloquial: more than one task accomplished simultaneously Cognitive science: more than one task between or.

Martha Bridge Denckla, MD.Martha Bridge Denckla, MD.

May 4, 2012May 4, 2012

Colloquial:Colloquial: more than one task more than one task accomplished simultaneouslyaccomplished simultaneously

Cognitive science: Cognitive science: more than one task more than one task between or among which there is rapid between or among which there is rapid shifting or sequential interleavingshifting or sequential interleaving

In a sequence of stimulus-response tasks, In a sequence of stimulus-response tasks, response to stimulus #1 overlaps response to stimulus #1 overlaps evaluation of stimulus #2evaluation of stimulus #2

Reading (most obviously when aloud) Reading (most obviously when aloud) involves saying a word while involves saying a word while “processing” the next word to the right“processing” the next word to the right

Thus fluent reading involves multitasking Thus fluent reading involves multitasking in the sense of interleavingin the sense of interleaving

Dual task performance does refer to Dual task performance does refer to simultaneous accomplishment of two simultaneous accomplishment of two taskstasks

DTP is an experimental probe into R/L DTP is an experimental probe into R/L hemispheric “shared processing space”hemispheric “shared processing space”

Example: Recite the alphabet while Example: Recite the alphabet while balancing a dowel on R hand’s index balancing a dowel on R hand’s index finger vs. L hand’s index fingerfinger vs. L hand’s index finger

Left hemisphere motor and language Left hemisphere motor and language “shared processing space” results in greater “shared processing space” results in greater slow-down of alphabet when R hand’s slow-down of alphabet when R hand’s challenge is to balance the dowel than when challenge is to balance the dowel than when LeftLeft

Note one “habitual/automatized” (alphabet) Note one “habitual/automatized” (alphabet) and one “novel” (balance dowel) taskand one “novel” (balance dowel) task

Each task is established Each task is established “habitual/automatized” (proverbial “walk “habitual/automatized” (proverbial “walk and chew gum”)and chew gum”)

One task is automatized, the other(s) One task is automatized, the other(s) require online processing, with relative require online processing, with relative degrees of noveltydegrees of novelty

Experienced driver, very familiar route, Experienced driver, very familiar route, listens to engrossing book on tapelistens to engrossing book on tape

Experienced driver, new route, misses an Experienced driver, new route, misses an exit while listening to routine newscastexit while listening to routine newscast

Now substitute for just listening the Now substitute for just listening the responses in conversation with passengerresponses in conversation with passenger

Now conversation is on cell phoneNow conversation is on cell phone

Motor habit, familiar visual environment, Motor habit, familiar visual environment, attention-grabbing audio-linguistic. MUST attention-grabbing audio-linguistic. MUST STILL REACT TO ALWAYS NOVEL TRAFFIC!STILL REACT TO ALWAYS NOVEL TRAFFIC!

Adding novel response formulations in Adding novel response formulations in conversation, worse if passenger (or cell conversation, worse if passenger (or cell phone partner) doesn’t adjust to trafficphone partner) doesn’t adjust to traffic

Texting while driving adds overt shift of Texting while driving adds overt shift of visual attention plus spelling response visual attention plus spelling response

Executive Function involves “I-S-I-S” and Executive Function involves “I-S-I-S” and the last 2, “Inhibit” and “Shift” are the last 2, “Inhibit” and “Shift” are explicitly challengedexplicitly challenged

Color-Word Subtest of Delis-Kaplan Color-Word Subtest of Delis-Kaplan Executive Function SystemExecutive Function System

Continuous Performance Tests, including Continuous Performance Tests, including Go/No-GoGo/No-Go

Diagnosis of ADHD is often associated Diagnosis of ADHD is often associated with cognitive control deficit (synonym with cognitive control deficit (synonym for executive dysfunction (EDF)for executive dysfunction (EDF)

EDF features of inhibitory insufficiency EDF features of inhibitory insufficiency and inefficient (slow/variable) response and inefficient (slow/variable) response preparation are prominent if ADHDpreparation are prominent if ADHD

Shifting more dysfunctional with Autistic Shifting more dysfunctional with Autistic Spectrum Disorder than with ADHDSpectrum Disorder than with ADHD

Lack of efficient response preparation Lack of efficient response preparation impairs automaticity of one of dual tasksimpairs automaticity of one of dual tasks

Insufficient inhibition impairs allocation of Insufficient inhibition impairs allocation of attention to novel processing demandsattention to novel processing demands

Despite good/adequate acquisition of Despite good/adequate acquisition of basic skills (use of phonics, memory for basic skills (use of phonics, memory for sight words with ADHD)sight words with ADHD)

Reading comprehension unexpectedly Reading comprehension unexpectedly lags in many with ADHD by 4lags in many with ADHD by 4thth grade grade

Suspect “processing speed” issue Suspect “processing speed” issue complicated by working memory deficitcomplicated by working memory deficit

Analysis of Processing Speed and Analysis of Processing Speed and Working Memory in Experimental tasksWorking Memory in Experimental tasks

fMRI of Working MemoryfMRI of Working Memory aMRI/DTI of relevant brain connectivityaMRI/DTI of relevant brain connectivity Electrophysiology of MultitaskingElectrophysiology of Multitasking

Joshua Ewen, MDKennedy Krieger Institute/JHUSOM

Spectrum 2012

[email protected]

KKI CSRD

Martha DencklaMark MahoneMatthew RyanLisa FerencPriya Xavier

JHU Psychological and Brain Sciences

Howard EgethJeff Moher

KKI Clinical Neurophysiology Laboratory• Balaji Lakshmanan

Reading Fluency

Conversation

Sports, Video Games

Driving

S R

S R“Cognitive Processing”

S Visual Proc

Stimulus Eval Response SelResponse

Exec R

RTRT

Well described Reaction time (RT) tasks

Wodka et al, JCEN 2007

Oculomotor tasks Thaler et al, J Atten Disord 2011 Nielsen & Wiig, Int J Psychiatry Clin Pract 2011. Mahone et al, JAACAP 2009 Hynd et al, J Learn Disabil 1989

Clinical Measures WISC-IV PSI (Coding and Symbol Search)

Mayes & Calhoun, J Atten Disord 2006

Reading Fluency Ghelani et al, Dyslexia 2004 Willcutt et al, Am J Med Gen B 2007

Response Execution (i.e., motor) Doesn’t explain silent reading fluency

Stimulus Evaluation vs. Response Selection “input-side” vs. “output side”

S Visual Proc

Stimulus Eval Response SelResponse

Exec R

RTRT

S Visual Proc

Stimulus Eval Response SelResponse

Exec R

RTRT

??

Stimulus Onset Asynchrony (SOA)

T1 T2

Response Sel

Visual Proc

Stimulus Eval Response Sel RE

Visual Proc

Stimulus Eval Response Sel RE

Visual Proc

Stimulus Eval Response Sel RE

Visual Proc

Stimulus Eval RE

Response Sel

Visual Proc

Stimulus Eval Response Sel RE

Visual Proc

Stimulus Eval RE

Long SOA

Short SOA

Marois & Ivanoff, Trends in Cog Sci 2005

“Central processing bottleneck”

Amodal

Some evidence for subcortical contribution

Ivry et al, J Exp Psychol: Hum Percept Perform 1998

Pashler er al, Neuroreport 1994

Multiple frontal areas Marti et al, NeuroImage 2012 Marois et al, Psychol Res 2006

Frontal-Parietal Networks Hesselmann et al, NeuroImage

2011

Response Sel

Visual Proc

Stimulus Eval Response Sel RE

Visual Proc

Stimulus Eval RE

Response Sel

Visual Proc

Stimulus Eval Response Sel RE

Visual Proc

Stimulus Eval RE

44 children (19 ADHD, 25 control), grades 4-8

Evaluated PRP effect

Ewen et al, Dev Neuropsychol 2012F(1,34) = 3.97, p = 0.05; ηp² = 0.11

Conclusions:1. Kids with ADHD have a higher

cost for multi-tasking2. This cost manifests in

processing speed3. This cost represents slowed

response selection

S Visual Proc

Stimulus Eval Response SelResponse

Exec R

RTRT

??

Parietal association cortex Picton, J Clinical Neurophysiol 1992

Combined in PRP-inducing paradigm, inferior parietal—pre-central regions activate

Hesselmann et al, NeuroImage 2011

Luck, Psychol Bulletin 1998

1. No significant effect of diagnosis on P3 latency

2. P3 and PRP reasonably independent: P3 latency predicted only 6% of PRP results

3. PRP (plus P3) predict reading fluency ΔR2 = 0.27 Majority of the effect from PRP ADHD showed stronger PRP-fluency effect than

controls

1. Children with ADHD have slowed processing speed

2. Motor slowing is not a confound in some measures

3. Response Selection is slowed in ADHD Increased costs for multi-tasking Relationship to fluency

4. Stimulus Evaluation may be slowed, but perhaps not a key contributor

P50 HD052121 (MBD; EMM)

K12 NS001696 (H. Singer)

K23 NS073626 (JBE)

Johns Hopkins ICTR

KKI IDDRC

Multitasking involved in reading Multitasking involved in reading comprehension is inefficient with ADHDcomprehension is inefficient with ADHD

RecapitulationRecapitulation: Fluency facilitates : Fluency facilitates comprehension and itself depends on comprehension and itself depends on interleaving sequential response interleaving sequential response preparation with overlapping stimulus preparation with overlapping stimulus evaluationevaluation

On scale of hours, switching and On scale of hours, switching and interleaving several strands of lifeinterleaving several strands of life

School (4-5 subjects)/Extracurricular/HomeSchool (4-5 subjects)/Extracurricular/Home Work (might be subdivided)/FamilyWork (might be subdivided)/Family ““Covert” multitasking from middle school Covert” multitasking from middle school

through life involves “cold” and “hot” through life involves “cold” and “hot” cognition (skills/duties vs. social relations)cognition (skills/duties vs. social relations)

Holding/bouncing baby, stirring pot of Holding/bouncing baby, stirring pot of soup, talking on phone to patientsoup, talking on phone to patient

Dictating patients’ reports while sitting in Dictating patients’ reports while sitting in car during sons’ soccer practicescar during sons’ soccer practices

Switching between patient reports and Switching between patient reports and portions of research papers to meet portions of research papers to meet deadlines of others to whom “owe” workdeadlines of others to whom “owe” work

Note necessity of Working Memory to a Note necessity of Working Memory to a multitasking agendamultitasking agenda