functional localization of the cerebral cortex

8/14/2019 Functional Localization of the Cerebral Cortex

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Functional

Localization of the

Cerebral Cortex


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Auditory area

Angular

gyrus

Visual

area

Somatic sensoryVoluntary

motor

Motor speech,

grammar & phonology

Voluntary eye

movements

Brodmanns Classification System


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: Areas of the Cerebral CortexOverview

A. Sensoryareas.

B. Associationareas.

C. Motorareas.

D. Other corticalareas of functionalsignificance.


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Sensorimotor hierarchy

1ry sensory

area(Perception)

2ry sensory area(association area)

(Meaning of the

stimulus)Main Association

(Wernikesarea) &prefrontal cortex (PFC)

(Integration)

Premotor area

(area 6)

(Plan of movement)

1ry motor area(area 4)

(Execution of

movement)


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Right vs. Left Hemispheres

Lateralization:asymmetrical distribution of function; emerges during fetal life.

Ex: Hand preferences (handedness).

- > 90% of population is right handed; so, has left dominant hemisphere.

- Dominance become fixed only after the 1stdecade.

- Corpus callosumtransports information received in one hemisphere to

the other half.

General distribution of function:

Right hemisphere:

Non-verbal perceptual tasks, visual and spatial perception, e.g.,

recognition of faces, & musical and artistic tasks.

Left hemisphere:

Language, speech, writing & analytical functions.


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Right vs. Left Hemispheres


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1. Occipital lobe

2ry visual area(visual Association area)

(areas 18,19)

1ry visual area

(visual Sensory area)

(area 17)

Lateralview

Medial view


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Hemianopia

Effect of lesion of the Rt.visual cortex


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Area Site Funct io n Effect of lesion

1ry.visual area

(v isual s ensory

area)

(area 17)

On each side of

the calcarine

S.& extends

slightly laterally.

- Perception of pictures.

- Input from thalamus

(Lateral Geniculate

Body = L.G.B.).

- Project to the visualassociation area.

Homonymous

hemianopia.

2ry.visual area

(visual

associat ion

area)

(area 18,19)

Around area 17

& rest of the

occipital lobe.

- Understanding the

meaning & importance

of the pictures seen.

- Color & movementvision.

- Stereoscopic depths.

Inability to know

the meaning of

the pictures seen(word bl indness, =

visu al agnosia).

Functional Areas of the Occipi talLobe


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2. Temporal lobe

2ry auditory area(Auditory Association area)

(areas 22)

1ry auditory area(Auditory Sensory area)

(areas 41,42)

Lateral view


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Temporal lobe (cont.)

Facial recognition area

Medial view


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3. Parietal lobe

1ry somesthetic area(area 3,1,2)

Somesthetic

Association area(area 5,7)

Wernikes areaSensory speech

center(area 39,40)

Lateral view

39

40

5, 7


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Sensory

cortex

Sensory Leg arealies on the medial surface

(paracentral lobule)

MedialLateral


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1ry.audito ry area

(audi tory sensory

area)

(area 41,42)

Middle of the sup.

temporal g.

(Heschls g.).

- Perception of sounds.

- Input from thalamus

(Medial Geniculate

Body =M.G.B.)

Incomp lete (s l ight)

bilateral deafness .

2ry.audi tory

area (audi tory

assoc iat ion area

(area 22)

The rest of the sup.

temporal g.

Understanding the

meaning & importanceof sounds.

Inability to know the

meaning of sounds(word d eafness, =

audito ry agn osia).

Facial

recogn it ion area

Parahippocampal g. Recognizing people by

faces.

Difficulty in recognizing

faces (prospagnosia).

Part of

Wernikesarea(sensory speech

center)

(area 39,40)

See parietal lobe

Functional Areas of the TemporalLobe


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1ry somesthetic area (area 3, 1, 2)

Representation:

The opposite half of body is

represented upside-down

(below for head & neck, then

U.L. and trunk).

Taste areal ies in the lowerend of the postcentra l g. &

insula.


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Area Site Func t ion Effect of lesion

Primarysomaethet ic

area

(area 3,1,2)

Postcentral g. +paracentral lobule

(sensory leg area)

- Proprioceptive sensations.- Cutaneous sensations.

- Vestibular sensation.

(from opposite of body)

Contralateralhemiansthesia.

(pain is slightly

affected)

Somethet ic

associat ionarea

(area 5,7)

Superior parietal

lobule.

- Understanding and

integrating various

sensory information.

- Center of Steriognosis.

- Difficulty in

understanding of the

meaning of various

sensory information

(= agnos ia).

- Aster iognosis.

Wernikes

area(sensoryspeech center)

(area 39,40)

- Inf. parietal lobule.

- Post. parts ofmiddle & inf.

temporal gyri.

(Only in the

dominant

hemisphere).

- Understanding of spoken

(auditory)& written

(visual) language.

- Integrationof different

senses that allows for

understanding a single

concept. Brocas area.

Receptive (sensory

aphasia).

Functional Areas of the Parietallobe


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1. Precentral area

2.


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4. Frontal lobe

Prefrontal Cortex(PFC)

1ry motor area(area 4)

Premotor area (area 6) &

supplementary motor areaFrontal eye field

Brocas areaMotor speech center

(area 44,45)

- Area 8- Part of area 6


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MedialLateral

Motor Leg area

lies on the medial surface

(paracentral lobule)

It is a map of body

movementsNot

muscles

Supplementarymotor cortex(area 6)

(area 4)

Motor Homunculus


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Representation:- The opposite half of body is

represented upside-down

(below for movements of head &

neck, then U.L. and trunk)

Movements of knees, legs, toes,anal & visc eral sphinc ters are in

theparacentral lob ule (= leg

area).

- The movement, NOTthe

muscles, are represented.- Highly skilled movements

occupy wider areas.

1. 1ry motor cortex (area 4)


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1ry mo tor area(area 4)

Precentral g. +paracentral

lobule (leg area).

Initiate voluntary skillfulmovements (pyramidal tract),

except eye.

Contralateralhemiplegia

(excep t eye).

Premo tor area

(area 6)

In front of area 4. - Planning of movement

design area 4.

- Main extra-pyramidal

area for posture & muscletone.

- Increased muscle tone &

reflexes.

- Disturbed skillful movements.

- Reappearance of grasp reflex.

Supplementary

motor c or tex

Medial surface,

of area 6

Planning complex sequence

of movements & their

coordination in both hands.

Impaired selection of a particular

movement sequence.

Frontal eye

field

(area 8)

In front of area 6 Initiate voluntary eye

movementsto the oppositeside (conjugate lateral

movements).

- Inability to direct eye to

the opposite side.- Deviation of both eyes to

the affected side.

Brocasarea

(motor speech

center)

(area 44,45)

Triangular part of

inf. frontal g.

(dominant

hemisphere)

Speech production by

projection to area 4 (larynx,

tongue, lips (vocalization).

Expressive (motor aphasia)

Inability to express language.

Functional Areas of the FrontalLobe


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Anatomy of Speech

11

23

4


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Speech

Speech areas normally in the dominant hemisphere.

Wernikes area: sensory speech center.

Brocas area: Motor speech center.

Aphasia:absent or defective speech or language comprehension.

Wernikes aphasia:= (sensory, receptive aphasia) no comprehension & failureto convey meaning.

Brocas aphasia:= expressive or motor aphasia.

1- Words are seen in the visual cortex,or heard in the auditory cortex.2- Information concerning the word is interpreted in Wernikes area.

3- Information from Wernikes areais transferred to Brocas area.

4- Information is transferred from the Brocas areato the 1ry motor area

for vocalization.


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It is also called Frontal association area.

Prefrontal Cortex (pfc)

Reminder of the frontal lobe in the lateral surface.

Most of the medial frontal g.

Orbital part of theinferior surface.


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Function: HIGHER MENTAL FUNCTIONS- Intellectual functions, thinking, solving problems,judgment & foresight & framing of personality.

- Control of social behavior.

- Short-term memory.- Controls our emotions, mood & behavior.- Inhibitsimpulsive actions of the basal ganglia.- Control of autonomic (visceral) activities.

Lesion: (traumatic, tumors, lobectomy & ADD)

- short attention span & loss of recent memory.- becomes careless of his appearance (behavior).- mood changes (emotionally labile).- loss of social inhibition & impulsive responses.

Prefrontal Cortex (pfc)


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Other Cortical Areas

Area Site Funct io nTaste area - Lower end of the postcentral g.

- Insula.

Taste (gustatory sensation).

Vestib ular area - Postcentral g. Sensation of position &movements of the head in

space.

Insula In the floor of the lateral s. - Coordination of themovements for speech.

- Taste sensation.

Olfact ion - 1ry olfactory area (periamygdaloid

& prepiriform areas).

- 2ry olfactory area.

Smell sensation.

L imbic lobe

(cortical part of the

limbic system).

- Cingulate g.

- Isthmus of limbic lobe.

- Parahippocampal gyrus.

- Uncus.

- Short-term memory.

- Control of endocrine system.

- Reactions of fear, anger&

emotions associated with

sexual behaviors.


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Insula

Olfactory area

Taste area

Vestibular area


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1. Cingulate g.

2. Isthmus oflimbic lobe

3. Parahippocampal g.4. Uncus

Limbic lobe

functional localization of the cerebral cortex

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