Lec 1 Functional Areas of Cerebral Cortex

7/31/2019 Lec 1 Functional Areas of Cerebral Cortex

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Brodmann numbered different areas of

cerebral cortex. Based on function,

2 types of areas:

1) Sensory areas (located in post central gyrus,

superior temporal gyrus & part of hippocampal

gyrus & contain granular cortex)

2) Motor areas (located in pre central gyrus & in

other parts of frontal lobe & contain mainly

agranular / pyramidal cortex)


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1) ELECTRICAL STIMULATION OF DIFFERENT

PARTS OF MOTOR AREAS : & movement of

different parts of body is noted.2)ABLATION METHOD: A part of motor cortex is

damaged & motor loss is noted.

3) CLINICO-PATHOLOGICAL STUDY OF

DISEASE: Post-mortem findings co-related toclinical loss of motor activity.


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1) PRIMARY MOTOR AREA

2) PRE MOTOR AREA

3) SUPPLEMENTARY MOTOR AREA

4) SPECIAL MOTOR AREAS


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MOTOR AREAS Brodmanns no:

Primary motor area 4

Pre motor area 6

Supplemental motor area 8, 9, 10

Brocas area / Motor

speech area

44, 45

Frontal eye field 8


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LOCATION: Lies in first convolution of frontal

lobes anterior to central sulcus. It begins

laterally in the sylvian fissure, spreads

superiorly to uppermost portion of brain & then

dips deep into the longitudinal fissure. It is

brodmanns area 4.

It consists ofagranular type of cerebral cortex.In this area in layer no: 5, there are giant

pyramidal cells called Betz cells


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There is topographical (parts by parts)

representation of body & contralateral as well

as upside down representation. By joining

these parts, a figure of the body is formed:

MOTOR HOMUNCULUS. It is a mirror image

ofSENSORY HOMUNCULUS.

Parts of body concerned with precise, fine &skilled movements, are represented by

much larger area.


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Coordinated movement of contra-lateral

parts of body.

Blood flow to motor cortex varies withmotor activity of different parts of body,

e.g, if right hand is moved, blood flow to

hand representation area in left motorcortex is increased (because ofcontra-

lateral control)


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AFFERENT CONNECTIONS:

Receives afferents from primary motor area ofopposite side &

Afferents from premotor & supplementarymotor areas &

Afferents from somatic sensory, auditory &

visual areas & Afferents from thalamus, basal ganglia &

cerebellum.


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EFFERENT CONNECTIONS:

Efferents to spinal cord as corticospinal tract.

Efferents to cranial nerve nuclei (corticobulbarfibers).

Efferents to thalamus.

Efferents to basal ganglia.

Efferents to cerebellum as cortico-ponto-

cerebellar fibers.


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LOCATION:Anterior to primary motor

area. It extends 1-3 cm anteriorly.

It is broad at top & narrow below.

At the top it extends upto longitudinal

fissure & below upto sylvian fissure /

lateral fissure.

It consists of superior, middle & inferior

frontal gyri. It is brodmanns area 6.


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In this area there is also topographical representation of

different parts of body & pattern is similar to that inprimary motor area.

When pre motor area is stimulated there aremovements involving contraction of groups of muscle.

This area is connected with primary motor area, directlyor indirectly through basal ganglia & then throughthalamus.

This area programs the activity of primary motor areawith the help of patterns already stored in brain.


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LOCATION: Lies mainly in the longitudinal fissure but

extends a few centimeters onto superior

frontal cortex. It contains medial frontal gyrus.

In this area different parts of body are

also represented. Face is anterior, legs are posterior, back

is in superior wall of singulate sulcus.


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When this area is stimulated, movement oflimbs or other parts on both sides (bilateral

movement).

Bilateral grasping movement.

This area controls the attitudinal, positional orfixation movements, e.g, background posturerequired for climbing up.

It supplements finer motor control areas (premotor & primary motor) by positionalmovements of head, eyes etc.


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LOCATION: In inferior frontal gyrus, justanterior to face representation area in primary

motor cortex.

It is brodmanns area 44, 45.

It is just above latral sulcus / sylvian fissure.

In this area detailed motor pattern for

contraction of muscles of phonation &

articulation is formed

.


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Then impulses are sent from this area toprimary motor area to initiate these

contractions. This area recieves impulses from

Wernickes area through arcuatefasiculus.

Spoken speech parts:

1) Phonation (to initiate vocal cord

vibration, these must be adducted)

2)Articulation

3) Resonance


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MOTOR APHASIA: Difficulty in utteringwords & speech is limited to only few

words.

Also called NON-FLUENT APHASIA. Damage does not prevent vocalizing.

May utter a simple word such as no or

yes. Impossible to speak whole words.


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LOCATION: In the pre motor area immediately aboveBrocas area is a locus for controlling voluntary eyemovements.

It is brodmanns area 8.

When this area is electrically stimulated, there is

conjugate deviation of eyes towards opposite side.

Similar area is also present in occipital lobe.

Frontal eye field also controls eye-lid movements likeblinking. When this area is damaged, person cannotmove eyes from one object to other.


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3) HEAD ROTATION AREA:

Near frontal eye field, slightly higher in motorassociation area.

Controls rotation of head. Electrical stimulation elicits head rotation

It directs the head towards different objects.

4)AREA FOR HAND SKILLS: In the premotor area, immediately anterior to primary

motor cortex for hands & fingers.

Controls hand skills.

When this area is damaged by tumors or otherlesionsMOTOR APRAXIA. Hand movementsbecome uncoordinated & non-purposeful.


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BROCAS

AREA

PRIMARY MOTOR

W. Area

CORTEX

ADDUCTORS

OF

VOCAL

CORDS

PHONATION

Pattern impulses

Allows to contract

ARCUATE

FASICULUS

Lec 1 Functional Areas of Cerebral Cortex

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