6 HEMISPHERIC SPECIALIZATION Language and other fcns 2011v2

8/7/2019 6 HEMISPHERIC SPECIALIZATION Language and other fcns 2011v2

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Language and other Higher Functions; Hemispheric

Specialization 2011**Lecturer: Dante G. Simbulan, Jr. PhD, Dept of Physiology, with Grps 10a, 10b, 11a, 11b

I. The Cerebral Cortex

Overview of the Cerebral Cortex: Basic Neural Circuitry of the 6-layered CortexHow the Various Cortical Regions are Interconnected: Association, Commisural and Projection Fibers

Overview of Localization of Cerebral Functions: Sensory, Motor, and Integrative Higher FunctionsII. Hemispheric Specialization and the Categorical Hemisphere

III. Hemispheric Specialization and the Representational Hemisphere

IV. Summary Table : Hemispheric specialization and complementation

V. Cognitive Functions of Cerebrocerebellum and Basal Ganglia

VI. Annex; Functional Areas of the Cerebral Cortex

(** Other higher mental functions, such as Learning and Memory, are taken up in detail in a separate Lecture/ Handout).

I. The Cerebral CortexA. Overview of the Cerebral Cortex: Basic Neural Circuitry of the 6-layered Neocortex

Cortical Layers Characteristics/ Function

(note: there are many interneurons in different layers )

Layers I – III (Molecular,

External Granular, External

Pyramidal)

Layer I also contains Horizontal

cells of Cajal; Pyramidal cells invarious layers

Numerous stellate cells, which indicate that these three layers areimportant for association and higher functions such as memory,

interpretation of sensory input, and certain discriminative

functions.. Receives association and commissural fiber inputs;

Pyramidal cells from these layers also send efferents to othercortical areas as association and commissural fibers. Layers I – IV

also receive non-specific afferents (reticular afferents and afferent

inputs from midline/intralaminar thalamic nuclei).

Layer IV

(Internal Granular Layer)

Mainly a RECEPTIVE LAYER (thalamocortical ascending fibers

end here).Mainly specific afferents from sensory pathways

Layer V

and VI (Internal Pyramidal and

Multiform/ Fusiform Layer)

Primarily efferent layers that contain nerve cell bodies whose axons

enter the corticospinal tract (descending fibers).. Martinotti cells in

Layer VI sends afferents to superficial layers. Main Projectionneurons to subcortical structures are pyramidal, plus fusiform cells.

In motor cortex, Betz cells are the large pyramidal cells located here

here.

I

II

III

IV

V

VI

Thalamo-

Cortical connections

Cortico-Thalamic connections,

corticospinal, corticobulbar

Efferent layers

(Layer V, VI)

Specific Afferent inputs

(Layer IV)

Association/ commisural

inputs; Inter-hemispheric

Information sharing

(Layers I – III)

Nonspecific afferent inputs

(Layers I – IV)



2B. How the Various Cortical Regions are Interconnected with each other, and

with subcortical regions: Through Association, Commisural and ProjectionFibers

Association fibers are nerve fibers that interconnect cortical regions of the samecerebral hemisphere.

Commisural fibers cross the midline and interconnect similar cortical regions in thetwo cerebral hemispheres.

Projection fibers connect cortical areas of the cerebrum with subcortical regions.Below are major association and commissural fibers of the cerebrum.

Association fibers on the lateral aspect of the cerebral hemispheresA. Uncinate fasciculus (uncinate means hook-shaped) interconnects the cortex of the uncus (of hippocampal

gyrus) and temporal pole with the inferior frontal region.

B. Inferior occipitofrontal fasciculus is located along the inferior portion of the extreme capsule, dorsal to the

uncinate fasciculus. It interconnects the cortex of the lateral or inferolateral portion of the frontal lobe and cortex of the occipital lobe, with connections along the way, including the inferior temporal and fusiform gyri of the temporal

lobe.

C. Superior Longitudinal Fasciculus is located along the dorsolateral border of the putamen, lateral to the

internal capsule. It underlies and interconnects the cortices of the frontal, parietal, and occipital lobes and arches

inferiorly and anteriorly with connections in the temporal lobe cortex.

D. Arcuate Fasciculus curves over and around the posterior part of the insula to pass into the temporal lobe. It

is a continuation of the superior longitudinal fasciculus (synonym for superior longitudinal fasciculus).E. Lateral Occipital Fasciculus (also known as vertial or perpendicular occipital fasciculus and as the

fasciculus of Wernicke) passes vertically through the occipital lobe and interconnects the fusiform gyrus of the

temporal lobe and the posterior part of the parietal lobe.

F. INFERIOR LONGITUDINAL FASCICLUS interconnects occipital lobe cortex and temporal lobe

cortex in the inferior and lateral portion of the hemisphere.

Association fibers on the medial aspect of the cerebral hemispheresA. Stratum Calcarium refers to a well-developed sheet of fibers curving around the bottom of the calcarine

fissure from the cuneus above to the lingual gyrus.

B. Cingulum (means girdle) is an association bundle of the cerebrum located within the cingulate gyrus. It

has connections all along its course with adjacent frontal, parietal and temporal lobe cortex.Superior Occipitofrontal Fasciculus – is located along the caudate nucleus medial to the interdigitating

fibers of the internal capsule and corpus callosum. Its fibers interconnect the cortex of the occipital

and temporal lobes with those of the frontal lobe and insula (synonym for subcallosal fasciculus).

Association and commisural fibers in coronal section of cerebral hemispheresA. Corpus Callosum (means hard body) is the thick band of commisural fibers interconnecting areas

of the neopallium (cerebral cortex and underlying white matter).B. Cingulum E. Arcuate FasciculusC. Superior and Inferior Occipitofrontal fasciculi F. Uncinate fasciculusD. Superior Longitudinal Fasciculus G. Anterior Commissure

FRON

TAL

LOBE

PARIETAL

LOBE

OCCIPITAL

LOBE



3C. Overview of Localization of Cerebral Functions (Sensory, Motor, and

Integrative, Higher Functions) Below is a partial listing of effects of lesions.

Structure Function Effects of Lesion/AblationFrontal Lobe Reasoning, Motivation,

modulation of emotions,parts of speech andmovement (motorcortex) , and problemsolving…..

What would happen if lesions were made ?

Effects of lesions in orbitofrontal cortex or Prefrontallobotomy – inability to solve complex problems; unable tostring together sequential tasks to reach a specific goal;decreased aggressiveness; loss of ambition andmotivation; lack of social inhibition; comprehend languagebut unable to carry through a conversation; mood swings;purposeless activities; lack of general concern.

Parietal Lobe Concerned withperception of stimulirelated to touch,pressure, temperatureand pain

See also other effects in tables below and above this(Especially with regards to visuo-spatial processing; notethat there is a dorsal (parietal) pathway from the occipitallobe in visual signal processing extending into the parietallobe)

Occipital Lobe Concerned with manyaspects of vision

What happens if striate (primary visual ) cortex is damaged?

TemporalLobe

Concerned withperception andrecognition of auditorystimuli (hearing),memory(hippocampus), as wellas emotions (amygdalaand periamygdaloidstructures)

See also other effects in tables below and above this.Note too that there is a ventral (temporal) pathway fromthe occipital lobe in visual signal processing extending intothe temporal lobe.

(Learning and memory functions, which involve thehippocampus, and various cortical areas, as well as thebasal ganglia and cerebellum, are considered in detail in aseparate handout and lecture.)

CorpusCallosum

Connecting bridgebetween twohemispheres

What is the effect of cutting this structure on the inter-hemispheric transfer of information, (the surgical procedurewas often done in treating epilepsy patients), especially iffibers of optic chiasm were also severed ?

What are the functions of the three major association areas ? [There are other models showingmore elaborate subdivisions of the different sensory, motor, and association cortices. For more, seesection VI. ANNEX, Major Functional Areas of the Cerebral Cortex.

a) Prefrontal association area (also known as the frontal lobe association area, anteriorassociation area or prefrontal cortex)– rostral to the premotor area; concerned with motorplanning, language production, judgement (including control of emotions). Also known as acentral executive for working memory and other coordinating functions, including receivinginputs from the rest of the cerebral cortex.

b) Parietal-occipital-temporal association area– (also known as the posterior associationarea) between the somesthetic and visual cortices, extending into posterior portion oftemporal lobe; links several sensory modalities for visuo-spatial perception (representational hemisphere mainly) and language (categorical hemisphere mainly).

c) Limbic association area (sometimes called also as the temporal association area) also

known as the “limbic cortex” – along the medial edge of the cerebral hemisphere, from thelower portion of the temporal lobe to the limbic system; concerned with emotions andmemory formation. This area is associated with the limbic system (see Neurobiology of Instincts and Emotions, previous topic.)

A.Prefrontal

Association

Area

B.Parieto-Occipito-

Temporal

Association

Area

C. Limbic

Association

Area

Supplementary

And Premotor

Areas

Primary

Motor

Primary

Somesthetic

Pr imar y auditor y

Pr imar y V isual

A.Prefrontal

Association

Area

B.Parieto-Occipito-

Temporal

Association

Area

C. Limbic

Association

Area

Supplementary

And Premotor

Areas

Primary

Motor

Primary

Somesthetic

Pr imar y auditor y

Pr imar y V isual

A.Prefrontal

Association

Area

B.Parieto-Occipito-

Temporal

Association

Area

C. Limbic

Association

Area

Supplementary

And Premotor

Areas

Primary

Motor

Primary

Somesthetic

Pr imar y auditor y

Pr imar y V isual



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II. Hemispheric Specialization and the Categorical

Hemisphere : Cognitive Aspects of Language; Math,

Logic (Neural Circuitry of Language)

A. Language is one major fundamental process in which man differs

biologically from animals.

Since no experimental animal has highly developed language skills, the study of language isdifficult. There are no simple anatomic differences between the brains of man and other animals toaccount for language, yet subtle differences between the two hemispheres of man’s brain do existand are related to the fact that, in adults, language functions occur predominantly in the leftdominant hemisphere

B. Language is separable into two components: conceptualization and

expression. These two components have neuroanatomical bases. See neural circuitry of

language below.

Neural pathway of

impulses from seeinga word to saying it.

(see similardescription in Chapt.

16 in Ganong)

(1). From retina to lateralgeniculate nucleus; fromlateral geniculate nucleus toprimary visual cortex (Area17)(2.) From primary visualcortex to higher order visualareas (Area 18).(3.) to angular gyrus (Area39).(4. ) to Wernicke’s area(Area 22).

(5) via association fibersknown as arcuatefasciculus(6) Broca’s area (Area 44) (7) to Facial area of motorcortex (Area 4) for activationof vocal apparatus

1

2

3

4

5

6

7

Broca’s

Area (44 &

45)

Wernicke-Geschwind model of language circuitry

1st

com onent: for conce tualization

2nd

component:

For Expression

PerisylvianLanguage



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C. Description of Language-related Areas in the Categorical

Hemisphere (in majority, the Left hemisphere)GENERALLY, the Left hemisphere is involved in : cognitive aspects of LANGUAGE, MATH,LOGIC.

Language-related Structures and Functions (Left hemisphere); Language

Disorders arising from Lesions : [APHASIAs – abnormalities of language functions (not

due to defects of vision, hearing nor motor paralysis); Lesions commonly due to embolism or bloodclot in a cerebral blood vessel. The neurological literature is rich in information about other effects(note that effects on other primary motor-sensory functions are not included for lack of space andfocus)].

Other authors may have slightly different locations for some lesion effects.

Structure Function Effects of Lesion/AblationAngular Gyrus(Area 39)

Processes and interpretsvisual information prior totransmission to Wernicke’sarea

ANOMIC APHASIA – difficulty in understanding writtenlanguage (dyslexia or word blindness) or pictures,because visual information is not processed andtransmitted to Wernicke’s area.

Wernicke‟s Area

(Area 22, leftsuperior posteriortemporal lobe)

comprehension of visual and

auditory information

FLUENT APHASIA (ALSO Known as receptive or sensory

aphasia) . What are characteristics ?

Arcuatefasciculus

connects Wernicke’s areawith Broca’s area

Conduction aphasia (also a type of FLUENT or receptive or sensory APHASIA). What are characteristics ?

Broca’s Area (Area 44,45 in left

frontal cortex)

Expressive area for speech NONFLUENT APHASIA (also called expressive ormotor aphasia ) . What are characteristics ?

Planumtemporale (left);(Left superiortemporal gyrus)

This is bigger in lefthemisphere than in right-handed individuals; involvedin language-related auditoryprocessing.

The asymmetry is even largerin musicians and others withperfect pitch.

Left temporallobeArea 38 (L)

Areas 18, 20, 21(L)

Part of a ventral (inferiortemporal) pathway

- Lesions: Inability to retrieve names of places andpersons . (but preserves ability to retrieve common nouns,verbs and adjectives)- Lesions: Object agnosia –especially on left hemisphere.

Two Lefthemisphere areasfound associatedwith mathematicalability

Left frontal lobe – concerned with number factsand exact calculations.

Bilateral Intraparietal sulci(parietal lobe) – concernedwith visuospatialrepresentations of numbersand finger counting.

Forms of Acalculia (impairment of mathematical ability)arising from lesions in left (or right) hemisphere:

(1) Left frontal lobe lesions results in a selectiveimpairment of mathematical ability .

(2) Bilateral lesions of intraparietal sulci: Anotherimpairment of mathematical ability also results .

* Note:Stereognosis functions also exist in the left posterior parietal cortex (somatosensory association area) for the

contralateral side of body, with corresponding deficits (astereognosis) after lesions.

Which structures concerned withEXPRESSIVE FUNCTIONS ofLanguage ?

Which structures concerned withRECEPTIVE FUNCTIONS ofLanguage

LESIONS

WHAT IS

GLOBAL

APHASIA ?



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WRITING IS ABNORMAL IN ALL APHASIAS IN WHICH SPEECH IS ABNORMAL. Below isanother model of a neural circuit of language processing (Petersen‟s model, 1988) . (Deaf -mutes trained in sign language who suffer damage to their language-related left hemisherealso have an impairment of their sign language abilites. )

TAKE NOTE that the Right (representational) hemisphere is concerned with the affectivecomponent of language, called prosody (see next section) . What is prosody ? What isexpressive aprosodia ? See Section III, below. What is receptive aprosodia ?

Other known “:higher” functions of the Categorical hemisphere. Left / categorical hemisphere – also involved in processing mathematical operation; effects

of lesions on the angular gyrus- also produces Acalculia

Left /Categorical Hemisphere - helps processes attentional focus on details of an image (localshifts in attention); lesions will result in loss of this ability. (Compare with the visuo-spatialprocessing functions of right hemisphere).

III. Hemispheric Specialization and the

Representational Hemisphere : Visuo-

spatial Processing , Affective Components

of Language, and other Functions

GENERALLY, the RIGHT HEMPISPHERE is involved in spatial abilities, face recognition, visualimagery, music (although recent researchers say that musical functions shared by bothhemispheres.), as well as the affective components (prosody) of language (prosody- elements ofstress, pitch and rhythm).

Representational Hemisphere: “Non-dominant” (in majority, the Right hemisphere). Noted below

are major functions as far as higher cortical association visuo-spatial processing (object

recognition) is concerned , as well as some affective components / emotional comprehension of

language. In general, though not discussed here in detail, the right hemisphere seem to exercise

dominance over emotions and all aspects of social-emotional intelligence . This is due to its

stronger connections to the limbic system.The neurological literature is rich in information aboutother effects (note that effects on other primary motor-sensory functions are not included). Other

authors may have slightly different locations for the lesions.

Broca’s

area is apremotor

area for

Anteriorinferior frontal

cortex (Left H)

SIGN LANGUAGE



7Below is a table showing a number of observed lesion effects of some right hemisphere cortical

association areas showing some resulting agnosias, as well as effects on affective components(prosody) of language (right hemisphere). Fore brevity, only a few agnosias affecting some of the

sensory association areas are shown. A listing of various apraxias (inability to voluntarily carry outactions upon command, with intact primary sensory and motor pathways) have not been included in

the table. [Agnosia - inability/ difficulty recognizing certain features of a sensory stimuli, despiteintact primary sensory cortex and specific ascending pathways. ]

Structure Function Effects of Lesion/Ablation/ OthersTemporal lobePortion of theposterior associationarea (some ex:) )

Areas 20, 21 (R > L ?)

Areas 18, 37 (R)

Areas 18, 20, 21 (L)*

Areas 18, 20, 21 (R )

Note: Part of visual inferiortemporal or ventralpathway for recognitionof form and color (the“what pathway”)

Face recognition (medialtemporal lobe)

Naming colors

(Naming, using, recognizingreal objects)

Recognition for drawnobjects

-

Lesions in right inferior temporal (temporo-occipital)cortex produces prosopagnosia (inability to recognizefaces); this is a form of visual agnosia. [Some datasuggests bilateral lesions produce this, while othersstate that right hemispheric lesions’ effects arestronger.]

Lesions: object agnosia – especially on lefthemisphere.Lesions: agnosia for drawings

Lesions: agnosia for drawings.

Parietal lobe

(Left and rightposterior parietallobe, parts of areas5, 7 – the

somatosensoryassociation area)

Mainly rightposterior, inferiorparietal lobule

(More below forright posteriorparietal cortex *)

Stereognosis – ability toidentify objects by feelingthem with contralateralhands, while blindfolded.

Attention to left and righthemispace, including one’sbody and extracorporealspace. (Note that there is adorsal (parietal) pathwayof the visual system fordiscerning motion, depth,and spatial information =the “where pathway”.) After

right hemisphere lesions,only left hemisphere functions focusing dominate.

Lesions (Areas 5, 7): Astereognosis/ tactile agnosia arise from lesions of the somesthetic association area.Different forms of apraxia also result due todisconnections of the somatosensory association area

from the motor association areas of the frontal lobe(especially with premotor and supplementary motorareas).

Lesions :Hemineglect – inattention to contralateral(left) part of the body (also specifically known ashemiasomatognosia or hemisomatagnosia),inattention to stimuli on contralateral (left) side, andneglect of contralateral hemi-space (spatial neglect). Ifthe patient is hemiplegic arising from lesions of rightfrontal lobe areas, and additional lesions to rightposterior parietal (inferior) areas, anosognosia (failureto recognize own hemiplegia) may result.

Right SMA (supplementarymotor area)

Concerned with laughter Stimulation – results in laughter

Right frontal cortex(approximatelymirroring Broca’sarea on the

contralateral side)

Gives emotional qualityof voice/ gestures (prosody)

Expressive aprosodia/ or dysprosody – flat tone orof one’s own voice and gestures; no emotional feelingsin speech or gestures

Right posteriorparietal cortex*(approximatelymirroring Wernicke’sarea on thecontralateral side)

Comprehend prosody ofother people’s voice/gestures

Inability to comprehend prosody (emotional tone ) ofother people’s voice or gestures (Receptive orsensory aprosodia/ dysprosody)



8Representational or right hemisphere – also involved in processing mathematical

operation; effects of lesions on the angular gyrus- also produces Acalculia.

Representational or right hemisphere - helps processes attentional focus on over-allpattern of an image (global shifts in attention); lesions will result in loss of this ability. Comparewith the visuo-spatial function of left hemisphere focusing on details of object/ image.

(Stuttering – associated with right cerebral dominance, and widespread activity in cerebralcortex and cerebellum.)

IV. SUMMARY OF Major Aspects of HEMISPHERIC SPECIALIZATION(LATERALIZATION) and COMPLEMENTATION

This is as far as language and visuo-spatial processing functions are concerned;some aspects of emotions are also noted. (Note that there are other differences notnoted here, but abundant in the neurological literature. Other authors may indicateslightly different location of lesions depending on source of scientific papers, but within

the affected cortical association area.)

CATEGORICAL (LEFT ) HEMISPHERE forcognitive aspects of language; details of visuo-spatial processing

REPRESENTATIONAL (RIGHT) HEMISPHERE foraffective components of language; global aspectsof visuo-spatial processing

1.Associated with right-handedness

2.Majority OF ADULT population– lefthemisphere is the categorical (language) hemisphere

Majority of adult population use -right hemisphere as therepresentational hemisphere..

3. Concerned with cognitive aspects of Language and

Speech capabilities (review aphasias arising from lesionsof various language-related areas of left hemisphere) .Compare with right hemisphere the following:a) Lesions in left frontal cortex (Broca‟s) result inexpressive or motor aphasia (nonfluent aphasia)b) Lesions in Wernicke‟s area result in receptive orsensory aphasia (fluent aphasia )

Concerned with prosody of Language; laughter and

affective components of language (expressive andreceptive prosody)

Compare effects with left hemisphere lesions.a) Lesions in right frontal cortex expressive ormotor aprosodiab) Lesions in right posterior parietal cortex receptiveor sensory aprosodia

FLAT TONE

ORVOICE

RIGHTFRONTAL

CORTICALLESION

RIGHT

POSTERIORPARIETALLESIONS

(others: temporal-parietalAreas)

INABILITYTO

UNDERSTANDEMOTIONAL

TONE OFSPEECH

FLAT TONE

ORVOICE

RIGHTFRONTAL

CORTICALLESION

FLAT TONE

ORVOICE

RIGHTFRONTAL

CORTICALLESION

RIGHT



INABILITYTO

UNDERSTANDEMOTIONAL

TONE OFSPEECH

RIGHT



INABILITYTO

UNDERSTANDEMOTIONAL

TONE OFSPEECH

RIGHT HEMISHPERE LESIONS

AND AFFECTIVE COMPONENTSThere is said to be RIGHTCEREBRAL “DOMINANCE”over EMOTIONS and SOCIAL-EMOTIONAL INTELLIGENCE.This is reflected in emotionalexpressive aspects of speechand emotional comprehensionof language dependent on the

right hemisphere.

Inability tocomprehend

jokes



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CATEGORICAL (LEFT ) HEMISPHERE forcognitive aspects of language; details of visuo-spatial processing

REPRESENTATIONAL (RIGHT) HEMISPHERE foraffective components of language; global aspectsof visuo-spatial processing

4. Categorize spatial relations (above, below, left, right):focused on one attribute of a stimulus at a time, whichalso mobilizes the representational hemisphere; when

intact, attention to only right hemispace.

Object identification in contralateral side of body in generalusing various sensory modalities; it is the neural substratefor stereognosis. For example, tactile perception.

Both L and R: Posterior parietal lesion (somatosensoryassociation cortex) astereognosis/ tactile agnosia tocontralateral side.

Visual agnosias arising from lesions1. Both or right side lesions (inferior temporal lobe)

stronger than left: lesions prosopagnosia(prosophenosia) , which is the inability to recognize faces.

2. Specific: some form of visual agnosia unique for theleft hemisphere arises from lesions of the angular gyrus,which results in pure word blindness (alexia/ dyslexia)found in anomic aphasia (inability to understand writtenlanguage or pictures).

3. Specific: Lesions (areas 18, 20, 21) objectagnosia, which is the inability to recognize real objectsreported in left hemisphere.

Concerned with attention on more than one attribute of astimulus (e.g. color and size) ; attention on one attributemobilizes both hemispheres. When intact, attention to

both left and right hemispace.

Object identification (gnosia) in general using varioussensory modalities; neural substrate for stereognosis – ability to identify objects by feeling them (parietal lobe).

Both L and R: Posterior parietal lesion (somatosensoryassociation cortex) astereognosis/ tactile agnosia tocontralateral side.

Visual agnosias arising from lesions1. Both or right side lesions (inferior temporal lobe)

stronger than left: lesions prosopagnosia (prosophenosia) , which is the inability to recognize faces.

2. Specific: Lesion (right posterior parietal lobe) Hemineglect or inattention to contralateral (left) side)results ; also manifested as hemiasomatognosia, spatialneglect, and/ or anosognosia (see previous table).

3. Specific: Lesions (areas 18, 20, 21, temporal lobe)

agnosia for drawings.

5.a. Normal fcn: Encodes high-spatial frequencies –the“details” of Image” --- local shifts

b. Effects of lesion below:

a. Normal fcn: Encodes low-spatial frequencies – the“global view;” overall pattern of image.

b. Effects of lesion below:

Left hemisphere functions dominate after right hemisphere

lesions.6. a. Normal (intact) : Concerned with moodcontrol (“Internal” feedback). The left hemisphere isan “optimist”.

b. ExtensiveLesions result in: depression (as patients disturbedabout their disability). [ Right hermisphere functionsdominate with extensive left hemispheric lesions, which“realistically” / pessimistically assesses disability.]

a. Normal: Concerned with feedback from the environment(“external feedback”); the right hemisphere is a realist ,or „pessimist‟.

b. Extensive lesions result in: apathy, patients unconcerned

about their disability, and even euphoric. [Left hemisphere

functions dominate with right hemispheric lesions].

Concerned with face recognition;

Lesion (inferior temporal lobe of right hemisphere)

prosopagnosia (inability to recognize faces)

Note: In the intact, normal mental state, there is a “check -and-balancing” actions of both the left and right hemispheres as theyreceive, process, and send response signals . Lesions, neurotransmitter imbalances, conduction failure or disconnections, arising fromvarious causes, can lead to derailment of hemispheric complementation and specializations. General principle of lesion studies:

example, when lesions occur in right hemisphere, the functions of the left hemisphere becomes more apparent, while the functions of the lesioned hemisphere diminishes. This is true for the reverse. Sometimes both hemispheres contribute equally to a certain highermental function. Degree of structural damage is manifested in the magnitude or degree of mental functional dysfunction.



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V. Cognitive Functions of Cerebrocerebellums and

Basal Ganglia

Basal Ganglia: The caudate nucleus, possibly because of its frontal cortical connections, havesome cognitive roles. Lesions of the caudate nucleus disrupt performance on tests involvingobject reversal and delayed alternation. The right caudate nucleus seem to be involved inlanguage processing, as shown by evidence where lesions produce a dysarthric form of aphasiathat resembles but different from Wernicke’s aphasia.` Cerebrocerebellum (neocerebellum): involved in planning and programming movements,together with the motor cortex and associated frontal areas.

The cerebellum seem to be also involved with pure cognitive tasks independent ofmotor functions: a patient damaged in the right cerebellum (due to a blocked posterior inferiorcerebellar artery) could not learn a word association task. Also, it was observed in other subjectsusing magnetic resonance brain imaging technique that the dentate nucleus increased itsactivity when subjects were required to evaluate sensory information consciously.

VI. ANNEX: MAJOR FUNCTIONAL AREAS OF THE

CEREBAL CORTEX (see also Section I C).

Functional designation Lobe Specific LocationPrimary Sensory Cortex

1. Somatosensory2. Visual3. Auditory4. Olfactory

5. Gustatory/ Taste

ParietalOccipitalTemporalWhere is olfactory cortex ?orbitofrontal cortex ?

Anterior part of insularcortex; also, face area ofthe parietal lobe

Postcentral gyrus (Areas 3,1,2)Banks of calcarine fissureHeschl’s gyrus

Unimodal sensory associationareas

1. Somato-sensory assoc.Visual assoc.

2. Auditory assoc.

ParietalOccipitemporal

Temporal

Posterior parietalInferolateral surface of occipital

and temporal lobesSuperior Temporal Gyrus

Multimodal sensory associationareas

1.Posterior association area(parieto-temporo-occipital)

2.Anterior (prefrontal) associationarea

3.Limbic association area

Parieto-temporal/ occipital

Frontal

Temporal, parietal, frontal

Junction between lobes

Prefrontal cortex, rostal topremotor areas on dorsal andlateral surfaces.

Cingulate gyrus, hippocampalformation, parahippocampalgyrus, amygdala

Motor association cortex

1. Premotor (motor preparationand programs)

Frontal Rostral to primary motor cortex

Primary Motor cortex Frontal Precentral gyrusWhich association area in the categorical hemisphere is Wernicke’s area located / Broca’s area ?Which association areas in the representational hemisphere are specialized for visuo-spatialperception ?Which association area functions as a central executive ?

6 HEMISPHERIC SPECIALIZATION Language and other fcns 2011v2

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