neuropsychology study of the relationship between brain and behavior often analyzing the deficits in...

Neuropsychology

Study of the relationship between brain and behavior

Often analyzing the deficits in human function following brain injury or pathology; ablation or lesion approach

Single-case studies

Provides powerful diagnostic tool to determine sites of brain lesions

May provide insights into normal brain function

Major advances are developing in areas of imaging technology

Unit Objectives

• To review function of some major brain regions

• To understand differences in findings using brain damaged and intact individuals

• To gain an overview of the types of tasks that allow predictions of brain-behavior relationships

• To familiarize self with diagnostic tests used to assess function

Tests and Assessment

Some examples:

Intelligence tests

• Binet: IQ = MA / CA * 100 (ave = 100, sd = 15)

• Wechsler IQ (WAIS): verbal and performance subtests

Personality tests

• inventories: MMPI, many different dimensions

• projective tests: Rorschach, Thematic apperception test (TAT)

Basic idea is to allow individual to project her/his personality through descriptions, generating stories, etc.

To assess function, tests, or batteries of tests are administered

Cognitive tests• Mini mental state exam (MMSE): One of the most widely used tests for assessing cognitive mental status.

WHY? Quick and comprehensive test of multiple functions

• Memory tests:

•Wechsler Memory Scale: Prose passage (declarative), paired associates (verbal assoc), priming task (“implicit”)

• Working memory: backward digit, listening (verbal), arithmetic (calculation)

• Famous face

• Procedural tasks: Tower of Hanoi, serial response task

• Executive function: Wisconsin Card Sort Test

• Attention: visual-spatial (line bisecting, embedded figures drawing), cognitive (stroop)

Tests and Assessment

• Visual – spatial Mental rotation / rod and frame: V-S manipulationRey-Osterrieth Figure: drawing Block designEmbedded figure

• Language: fluency, comprehension, naming, repetition, grammar,

• Calculation: arithmetic

• Sensory-motor: tracking, finger tapping

• Recognition tests:Objects, faces, places

• Laterality and function of corpus callosum: L-R: Block design, R-O figure, emotion detection, Chimeric stimuli, dichotic listening, dichaptic presentation

Tests and Assessment

Different approaches to define

Overview of Brain Areas

Gross Anatomy: 4 lobes

FrontalExecutive MotorSequences, starting and stoppingAppropriate emotional

responses

ParietalMultimodal assocSpatial processingObject recognitionS-M coordination

OccipitalVision

TemporalObject recognitionMemoryAuditionemotions

Overview of Brain Areas

Gyri and sulci

Cytoarchitectonic

Maps of the Cerebral Cortex

Some subcortical structures

Some subcortical structures

Structure – Function relationships

Cortex has Topographic Organization

somatosensory

motor

This map is very PLASTIC and DYNAMIC!

Hemispheric Specializations

Function:• Verbal L, Visuospatial R• component (L) vs global identification (R) • spatial processing (R)• face, object recognition (R)• emotion detection (R)• temporal processing (L) • language (L)

Structure:

While damage to each hemisphere can result in specific deficits, actions = unified processing of single brain

Left vs Right

Split-Brain Procedure

Evidence from Split-Brain Patients

LH regulates language output

RH superior at face and object recognition, spatial processing

Accuracy low Accuracy high

Evidence from Lateralized Lesioned and Intact Individuals

Tasks:

•Wada technique

•divided visual field (tachistoscopic), dichaptic presentation, dichotic listening

Findings:

•RH processes nonverbal info, nonverbal sounds, global aspects, emotion detection

•LH processes verbal info (95% right handers), local aspects, details,

Emotion detection: which looks happier?

Neuropsychological bases of specific mental functions

Object recognition

Spatial processing

Attention

Language

Memory

Executive function

DementiaVisual processing pathways:

• dorsal stream --“where”

• ventral stream -- “what”

Object Recognition

Inability to perceive or to identify stimulus through specific sensory modality = AGNOSIA

Visual agnosias:

Apperceptive visual agnosia: can’t form “percept” of parts; can’t recognize objects

Associative visual agnosia: can’t draw from knowledge; don’t know what looking for

Prosopagnosia: inability to recognize or differentiate faces

Rule out memory disorders or primary sensory problems

Examples of visual agnosias

Apperceptive agnosias: inability to form perceptual categorization

Associative agnosia: able to group, but unable to do so from memory

Apperceptive agnosia

Associative agnosia

A Special Agnosia: Problems with Face Recognition

Configural information important for recognizing faces

Evidence: Intact participants exhibit more difficulty remembering inverted stimuli than up-right stimuli

This inversion effect is greater for faces than for other objects, such as houses

Damage to ventro-medial areas of RH impair face recognition

What’s wrong with this picture?

Spatial Processing

Perception involves a multitude of basic skills

localization of points in space

depth perception

orientation of lines

geometric relations

motion

rotation

Construction

Route Finding

Processing can involve extrapersonal or intrapersonal space.

Damage to parietal, occipital, and temporal cortex disrupts spatial processing; worse with RH damage

Dorsal visual stream

Construction deficits

Block design test shows evidence of

B. RH damage

C. LH damage

Rey-Osterrieth figure: Shows evidence of damage to posterior regions of RH (temporo-parietal)

HemineglectInattention to space contralateral to lesion

Language disorders: Aphasias

Memory and Amnesia

Anterograde (e.g. Leonard Shelby in Memento):

• impairment in LTM, not WM

• global in modality

• impairment in memory for new info, but not skills

• inflexibility of learned material

Retrograde: • varies in length of time

• has a temporal gradient

• never ALL memory

• skilled performance tends to be spared

Differences between Anterograde and Retrograde

Multiple memory systemsCase study: H.M.

Many taxonomies have been derived: explicit v implicit, declarative (relational) v procedural, episodic v semantic, working v reference

Not all forms of learning and memory are affected in amnesics

Brain Correlates

Medial temporal lobes / Hippocampus

Midline Diencephalon

Neocortex

Frontal lobes

Basal Ganglia / Caudate nucleus

Memory for information and events is processed in a distributed fashion, with different attributes handled by different cortical and subcortical systems

Memory Disorders

Retrograde vs anterograde amnesia

Frontal Lobe and Executive Function

Mini Mental State Exam

QUICK AND EASY: Simple 30 point scaleOrientation (10 pts): what (yr, season, date, day month?) and where (state, county, town/city, bldg, floor?)

Registration / Memory (3 pts): 3 objects, “pen, ball, ring”

Attention / calculation (5 pts): serial 7’s backward from 100

Recall (3 pts): Ask for all 3 objects

Language (8 pts): Naming (2 pts): point to pencil, watchReading (1 pt): “No ifs, ands, or buts.”Listen and do (3 pts) : “Take paper in your right hand. Fold paper in

half. Put paper on floor.”Read and do (1 pt): “CLOSE YOUR EYES.”Writing (1 pt): Ask to write a sentence of choice.

Visual-spatial construction (1 pt): copy design:

27-30 = Normal23-26 = Borderline < 22 = Abnormal

MMSE Ratings

Alzheimer’s ratings20-26 Mild AD10-19 Moderate AD < 10 Severe AD

Performance on MMSE varies with age and educationRemember the MMSE is not a true dementia diagnostic

It is a useful tool for a quick memory screening and to chart change with time

Dementia

Neuropathology of Alzheimer’s Disease

Progression of AD

Deficits Associated with Chronic Alcohol Use

Visuospatial problems

Learning and memory deficits

Mid-line diencephalic pathology

Thiamin (B1) deficiency

Deficits in oxidative metabolism?

Assessment Issues

Validity: does a test measure what it sets out to measure?

predictive: test can predict future performance (e.g. MCATs predict performance in med school)

construct: performance fits well with scheme about what test attempts to measure

(e.g. MCATs measure ability to retain loads of material and to endure long, exams)

Reliability: consistency of a test

Test-retest: repeated tests yield same results

Split-half: performance on similar portions yield same results

Summary

Brain damage can produce specific and reliable deficits in behaviors, providing a powerful diagnostic tool.

Findings suggest that the brain is lateralized and specialized in function across different neural systems.

Functional consequences of brain damage may lend insights into normal brain function in intact individuals.

Improvements in functional imaging technology will allow researchers and clinicians to explore the workings of the intact brain and to provide treatment with minimal invasion.