Chapter 5 - Behavioural Research Methods

Behavioural Paradigm

Single set of procedures developed for the investigation of a particular behavioural phenomenon

Modern Approach to Neuropsychological Testing

1. Single-Test approach

2. Standardized-test-battery approach

3. Customized-test-battery approach

Single-Test Approach

-Older method (before 1950s)

-Goal was to discriminate between patients with psychological problems due to structural brain damage and psychological problems due to functional changes to the brain

-Largely unsuccessful, no single test could differentiate the varied/complex symptoms in patients

Standardized-Test-Battery Approach

-Newer method (1960s)

-Similar objective to single-test approach (identify brain-damaged patients) but testing involved standardized batteries of tests rather than a single test

Halstead-Reitan Neuropsychological Test Battery - Set of tests that tend to be performed poorly by brain-damaged patients, scores on each test are added to form an aggregate score

-If aggregate score is below the cutoff, leads to diagnosis of brain damage

-Not very successful at discriminating between neurological and psychiatric patients

Customized-Test-Battery Approach

Most modern test approach

-Objective is to characterize the nature of psychological deficits of each brain-damaged patient

-Common battery of tests selected, then based on those results another series of tests customized to the patient are assigned

Customized Tests vs Older Methods

1. Newer tests are designed to measure aspects of psychological function (intelligence, memory, etc)

2. Interpretation of tests does not rest entirely on how well the patient performs, but requires an assessment of the cognitive strategy used by the patient in the test

3. Requires more skill/knowledge on the neuropsychologist to select the correct battery of tests to expose particular deficits

Tests of Common Neuropsychological Test Battery

1. Intelligence

2. Memory

3. Language

4. Language Lateralization

Intelligence

Test of general intelligence to score an IQ (intelligence quotient)

-Wechscler Adult Intelligence Scale (WAIS), composed of subtests and results in an IQ score being provided

-Fails to detect memory deficits (particularly in short-term memory)

Memory

Uses tests like the digit span subtest (widely used test for short-term memory) which identifies longest sequence of random digits that a patient can repeat correctly 50% of the time

-Most people have a digit span of 7

Language

Token Test - Test for language-related deficits that involves following verbal instructions to touch or move tokens of different shapes, sizes, and colours

Language Lateralization

Usual for people to use one hemisphere more in language-related activities (left hemisphere is usually more dominant for most)

Sodium Amytal Test - Injects sodium amytal into the left or right carotid artery to anesthetize the ipsilateral (same-side hemisphere) while leaving the contralateral (opposite-side hemisphere) un affected, tests of language function are provided

Left carotid artery = left side anesthetized, and vice-versa

-When injection is on side dominant for language, patients are mute. When on the nondominant side, they usually experience a few minor speech problems

-Given before surgery to determine what side is dominant as a precaution

Dichotic Listening Test - sequences of spoken digits are presented through stereo headphones, three digits presented to one ear at the same time three other digits are presented to the other ear

-Patients report as many of the six digits as possible; patients remember more of the digits head by the contralateral ear to the dominant hemisphere as determined by the sodium amytal test

Ex; left ear numbers recalled better = dominant hemisphere is the right side

Specific Neuropsychological Function

1. Memory - Four fundamental questions: does memory impairment affect short or long term memory? Are any deficits in long-term memory anterograde (retention of things prior to damage) or retrograde (retention of things after damage)? Does it involve semantic (factual) memory or episodic (personal) memories? Are deficits in long-term memory explicit or implicit?

• Repetition Priming Tests - Tests of implicit memory, list of words presented, then fragments of original words presented, subject asked to complete them

2. Language - Looks at problems of phonology (rules governing language sounds), syntax (grammar), or semantics (meaning of words)

Assumptions of Cognitive Neuroscience

1. Each complex cognition process results from combined activities of simple cognitive processes called Constituent Cognitive Processes

Ex; Language is made up of smaller, simpler cognitive processes which come together to constitute the larger process

-Sound of language + meaning of language + structure of language = language

2. Each constituent cognitive process is mediated by neural activity within a particular brain region or across a set of brain regions

Paired-Image Subtraction Technique

Uses PET or fMRI to locate constituent cognitive processes in the brain by producing an image of the difference in brain activity associated with two cognitive tasks that differ in terms of a single constituent cognitive process

Example of Paired-Image Subtraction Technique

In the word-association task, participants spent a minute reading aloud printed nouns as they appeared on a screen (such as truck), this acts as a control session

-In another task, they observed the same nouns on the screen but responded by saying an associated verb (e.g, truck → drive)

-Subtracted the activity in the images during the two tasks to obtain a difference image illustrating areas of the brain specifically involved in constituent cognitive processes of word association

Default Mode Network

Pattern of brain activity present when humans sit quietly and minds wander

-Brain structures active in default mode but less active during cognitive tasks are the default mode network

1. Media parietal cortex

2. Lateral parietal cortex

3. medial prefrontal cortex

4. lateral temporal cortex

-Makes interpreting differences images complicated

Mean Difference Images

Another difficulty in using PET or fMRI to locate constituent cognitive processes is noises associated with random cerebral events

-By averaging the difference images obtained from repetitions of the same test, signal-to-noise ratio can be increased (signal averaging)

-Resulting mean (average) difference image emphasizes areas of activity common to volunteers and de-emphasizes areas of activity unique to volunteers

Functional Connectivity

Approach used by cognitive neuroscientists that examines which brain regions have parallel activation patterns over time

-Intrinsic FC - when the FC is present during the R-fMRI

-Extrinsic FC - studies changes in FC with the presentation of a stimulus/task

Functional Connectome - Catalogue of functional connectivity associated with each behaviour and cognitive process

Species Common Behaviours

Displayed by virtually all members of a species, or at least those of same age/sex

-Includes grooming, swimming, eating, drinking, fighting, copulating and nest building

Open-Field Test

Subject placed in large, barren chamber and activity is recorded

-Low activity and high bolus counts (pieces of excrement) indicates fear

Thigmotaxic - rarely venture away from walls of test chamber (another indicator of fear in rats)

Tests of Aggressive and Defensive Behaviour

Colony-Intruder Paradigm - paradigm for study of aggressive and defensive behaviours in male rats, small male intruder rat is placed in an established colony in order to study aggressive responses of the colony’s alpha male and defensive responses of the intruder

Elevated-Plus Maze - Records defensiveness/anxiety in rats by assessing their tendncy to avoid two open arms of a plus sign-shaped maze mounted some distance above the floor

Tests of Sexual Behaviour

Lordosis - Sexual cues

Intromission, ejaculates

Pavlovian Conditioning Paradigm

Experimenter pairs initially neutral stimulus (conditional stimulus, tone) with an unconditional stimulus (food) that elicits an unconditional (reflexive) response

-Conditional stimulus eventually acquires capacity to elicit the conditional response often (not always) similar to unconditioned response

Operant Conditioning Paradigm

Rate at which particular voluntary response is emitted by increased reinforcement or decreased punishment

-Self-Stimulation paradigm; animal presses lever to deliver electrical stimulation in particular sites in their own brains, those structures in the brain that support self-stimulation are “pleasure centers”

Conditioned Taste Aversion

Avoidance response that develops to tastes of food whose consumption has been followed by illness

-Standard aersion experiment; rats receive a nausea-inducing drug (emetic) and consume a food with an unfamiliar taste, rats learn to then avoid the taste

-Rats and other animals are neophobic (afraid of new things), only eat small quantities of new food and readily develop conditioned aversions

Consequence of Conditioned Taste Aversion

Challenged three principles of learning

1. Animal conditioning is always a gradual step-by-step process, but taste aversions can be established in a single trial

2. Temporal Contiguity is not essential in conditioning (can acquire taste aversions even after hours between illness and food presentation)

3. Principle of Equipotentiality - view that conditioning proceeds in the same manner (Rats have evolved readily learned associations between taste and illness)

• Colour of food and taste are readily associated

Radial Arm Maze

Maze in which several arms radiate out from a central starting chamber, commonly used to study spatial learning in rats

-Rats are placed each day in a maze, after a few days of experience rats rarely visit unbaited arms (arms with no food), rats must learn orientation size all arms are identical

-Performance can be disrupted by the rtation of the maze or changes in appearance of the rooms

Morris Water Maze

Pool of milky water that has a goal platform invisible just beneath its surface, and is used to study the ability of rats to learn spatial locations

-Water maze tests is used to test spatial memory, in which rats must learn to swim directly to a platform hidden beneath the surface of a pool of murky water

Conditioned Defensive Burying

Burial of a source of aversive stimulation by rats

-Rats receive a single aversive stimulus from an objected mounted on the wall

-After a single trial, almost every rat learns that the test object is a threat, responds by flinging material at the object to cover it

-Antianxiety drugs reduce amount of conditioned defensive burying

Golgi Stain

Performed by exposing neural tissue to Potassium Dichromate and Silver Nitrate

-Results in Silver Chromate being uptaken by neurons, staining them black

-Displays neural structure/shape within a neural tissue

Nissl Stain

Performed by exposing neural tissues to Nissl Dyes (like Cresyl Violet), penetrates the neurons and binds molecules in the cell bodies (only)

-Allows for the number of cell bodies to be counted

Electron Microscopy

Provides detailed 3D neural structure images (high spatial resolution)

-Obtained by coating neural tissue with a substance that absorbs electrons

-Different parts of the neuron will absorb the substance to differing degrees

-Slice is placed into the microscope, beam of electrons pass through neural tissue, yields image based on the electrons passing through structures (not absorbed)

Anterograde and Retrograde Tracing

Anterograde Tracing Technique - Traces path of axons extending away from the cell body

-A tracer is injected at the cell body, taken up by the cell body and moves along the axon towards the terminal end

-Neural tissue is then treated to reveal location of the tracers

Retrograde Tracing Technique - Traces path of axons extending towards a particular area

-A tracer is injected at the site of synapses (the area), taken up by synaptic terminals and moves along the axon towards the cell body

-Neural tissue is then treated to reveal location of tracer

Token Test

Involves twenty tokens differing in shape, colour and size (2 different sizes, 2 different shapes, 5 different colours)

-Instructions start simple then increase in complexity

-Tests language by our ability to understand instructions

-Simple instructions are followed by difficult instructions

-Participant also reads an instruction and perform it to test comprehension

Ex; Touch red square → Touch red square then touch the white circle

Wisconsin Card Sorting Task

Assesses function of the prefrontal cortex

-Patient has four cards (stimulus cards) + deck of cards

-Cards vary in three ways; shape, colour and number of shapes on the card (1,2,3 or 4)

-Patient must sort the card to one of the 4 stimulus cards, but the sorting rule is unknown to the patient (only the examiner knows), patient must determine the sorting rule

-Sorting rule is changed midway (without telling the patient), must be re-determined again

If an individual has no front-lobe damage, they should be able to relearn the new sorting rule

-If someone does have frontal-lobe damage, they can learn the first sorting rule but has difficulty relearning the new sorting rule