2.2 Measuring Brain Function RT, MT, TRT

2.2 Measuring Brain FunctionReaction Time & Movement Time

Vickers Chapter 3Carter pp. 116-121

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Objectives Historically, understand how reaction time (RT),

movement time (MT) and total response time (TRT) have been measured (1860 to today)

Know thresholds for visual, auditory and haptic RT Understand Hicks Law (1952) Understand relationship between neural impulse >

action potential (AP) > event related potential (ERP) > and reaction time (RT)

Understand how movement time is measured in the clinical setting (eg. multiple sclerosis)

Understand how the RT and MT function at the Carter neural level

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1880-1990The Frac.onated Reac.on Time

Paradigm(Mental Chronometry)

Precise measurement of reac/on /me (RT), movement /me (MT) and total

response /me (TRT)

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Reaction time (RT), movement time (MT) and total response time (TRT)

Defined: The amount of time (measured in ms) to plan, initiate and carry out a movement.

One of the oldest findings in psychology & neurophysiology

Which do you think is fastest?Visual RTAuditory RTTouch (haptic) RT

Average reaction time

Woodward (1911). Time relations of mental phenomena.Elements of Physiological Psychology (Chapter 6).

OpticalStimulusms

AcousticStimulusms

TouchStimulusms

Conclusion: Visual RT is slower than eitherAuditory RT or Touch RT

Hirsch 200 149 182Hankel 225 151 155Donders 188 180 154Von Wittich 194 182 130Wundt 175 128 188Exner 150 136 128Auerbach 191 122 146Von Kries 193 120 117

Mean RT 189.5 146 150 ( now ~ 120 ms)

Mean RT Differs for Vision, Hearing and Touch (Nave Subjects)

The Fractionated RT ParadigmAll research studies include 4 events (1-4)

1. A warning/ready signal is given (eg. in sprints, the starter says "On your marks" and "Set" (see p. 49 Vickers). In psychology or neural monitor based studies: look at the centre dot.

2. Stimulus is presented. ( sprints - gun fires; in psych/neural studies - stimulus appears (letter, color, word, etc)

3. Initiation of observeable response and movement time. In sprints,

6. Response ends

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False Start in 100 m SprintUsain Bolt

2011 World Championships, Daegu, S. Korea

h>ps://www.youtube.com/watch?v=cgVJP0RmR-Y

The Fractionated RT ParadigmReaction time defined (RT) - neural/perceptual/cognitive time from the onset of a stimulus to the observable action

1.There is a cognitive delay (or latency) prior to all movements.

2.Time needed to prepare, select and initiate the movement.

2. Movement time (MT) -

The Fractionated RT Paradigm EMG (electromyography)

electrical current from muscles

Electrodes pick up electrical signals from activated muscles Muscles begin to fire prior

to observable action (premotor versus motor time)

EMG is not measured/or reported in most psychology/neuroscience studies. Why?

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Why Do Most Research Studies Rarely Report MT?

n Most research tasks require simple motor responses (eg. key press, move a lever)

n MT is usually very shortn Participants are first trained so the motor learning

phase is completen

Motor Learning (skill acquisi/on)

Dened: a set of internal processes associated with prac/ce or experience leading to rela/vely permanent changes in the capability for motor skill (Schmidt & Lee, 2011)

Dis/nct from motor development, which looks at the process of change over the lifespan - from birth to death. Occurs naturally - without prac/ce

Motor Control (motor performance)

Dened: Basics of the motor skill have been learned; the goal is one of control and mastery under all condi/ons.

Outcome is dened in terms of measurable performance - speed, accuracy, technical perfec/on (dance, gymnas/cs), consistency, # errors, etc

During research experiments it is assumed the person has learned the basics movements required in the task, entered a state of motor control.

In Kinesiology (and quiet eye studies)

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Reaction Time (RT)Hicks Law (1952)

Reaction Time Defined: The amount of neural processing time needed to plan, select and initiate a movement

Hicks Law - The Reaction Time LawThere is a stable relationship between the number of stimulus-response (S-R) options and choice reaction time.

As the number of S-R pairs increases, choice reaction time increases in a linear fashion

Hicks Law (1952)Enduring Reaction Time Law

As the number of stimulusresponse (S-R) alternatives increases, RT increases linearly.Y axis - RT measured in

milliseconds (1000 ms = 1 s)X axisS - a cue in the environment/

signal to start or respondR - a muscle group - finger,

fingers, hands, foot, body, etcWith practice, RT can be reduced

to 100-120 ms for many tasks; but no lower (eg. 100 m start)Hardwired neural characteristic

of humans

Regression line showing

linear relationship

Number of S-R alternatives

Reaction Time ExerciseIt is important to feel the effects

of Hicks Law

D F J KComputer Keys

Draw your own - 4 RT KEYS

On Screen

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Simple Reaction Time

n One stimulus and one response n (1 Stimulus and 1 Motor Response)

n Task: Place your finger on any key and as soon as you see the red bar push the correct key down

n Very simple movementn READY

Simple RT - 1 stimuli & 1 response - Place 1 finger on any key

Push key as soon as you see the stimulus

Hicks Law - 1952 RT Law

n Threshold of visual RT = 180-200 ms (without practice)

n MT to press the key does not change - takes about 50-70 ms

n Majority of the time is neural processing time

Regression line showing linear

relationship

Human RT cannot be faster than 100 ms - hardwired

Number of S-R alternatives

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Choice Reaction Time

The interval of time between the presentation of one of several stimuli and the beginning of one of several responses

Key understanding is that there is more than one visual stimulus and more than one set of muscles you have to organize

Choice RT - 2 hands Left finger on D or F and Right finger on J or K

Push key that is a match for location of light

D F J KComputer Keys

2 Choice RT - 2 hands/fingers Left finder on D or F and Right finger on J or K

Push key that is a match for location of light

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Hicks Law - Choice RT

n RT doubles - increases to 320-400 ms

n MT to press the key does not change that much - still takes about 70-80 ms

n Change due to cost of decision making

Regression line showing linear

relationship

Number of S-R alternatives

D F J KComputer Keys

4 Choice RT - 2 hands & 4 fingers 2 Left fingers on D or F and 2 Right fingers on J or K

Push key that is a match for location of light

4 Choice RT - 2 hands & 4 fingers 2 Left fingers on D or F and 2 Right fingers on J or K

Push key that is a match for location of light

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Hicks Law - Choice RT

n RT = 400-500 msn With 4 possible MTs

time to press the key increase 70-90 ms

n But most of the time is taken by the decision making/RT phase

n Now cross your hands

Regression line showing linear

relationship

Stimulus Incompatibility - Cross Your Hands 2 Left fingers on D or F and 2 Right fingers on J or K

Push key that is a match for location of light

D F J KComputer Keys

S-R Compatibility - RT is faster for compatible S-R pairs. Some S-R pairs are awkward; naturally in conflict

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Hicks Law - Choice RT

n RT = 700 +n Errors very highn MT to press the the

key increases to 70-100 ms

n Reaches a plateau or asymptote

n RT is a mental phenomenon, not a motor one

Regression line showing linear

relationship

Reaction time can be improved and depends on:

n Amount of practicen Amount of optimal training/deliberate practicen Age - easier to learn new skills when young, but

not impossible n Anticipation -

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Recent Study of Reaction Time

n Childrens RT?n Lower than adults

n Fastest RT?n Ages 20-29

n RT typically declines at age?n 50+ but modestly

n Slowing down is due mostly to changes in RT or MT?n Can be delayed with exercise

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But What Exactly Is Reaction Time (RT?)

Test your Reaction Time On-Line

http://getyourwebsitehere.com/jswb/rttest01.html

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Measuring MT In the Clinical Setting

The Nerve Conduction Test

https://www.youtube.com/watch?v=k0uSpYd_Ics

Nerve Conduction MeasurementMeasuring the speed of movement time (MT)

The nerve conduction velocity (NVC) test is performed to evaluate nerve function.It tests the speed impulses travel through a nerve.

F-Wave measured - average speed of transmission between two points

The minimal F wave speed of motor nerves is Used to Diagnose:

Carpal tunnel syndromeMultiple sclerosis

DiabetesMany other diseases

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Nerve Conduction MeasurementMeasuring the speed of Neural Transmission

Movement time (MT) is about double the above values (50-64 for upper limbs - additional times due to motor cortex to spinal nerve)

90-112 ms for lower. Difficult to lower this value - considered a constant ~ 70-80 ms

For ex. If response time is 300 ms (RT + MT = response time), then gains must be achieved via the RT component (better perception, attention, decision making)

In adults, aged 15 and above, F latency (speed) in simple motor tasks does not differ due to gender or age.

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Neural RT and MT (Carter pp 120-121)

NEXT4.0 Movement and

Control

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