Functional areas of the brain

FUNCTIONAL AREAS OF
CEREBRAL CORTEX
PRESENTED BY:- HARSHEKA KAR
MOT(NEUROLOGY) I YEAR
ISIC INSTITUTE OF REHAB SCIENCES

CEREBRAL CORTEX
. IT IS A SHEET OF NEURAL TISSUE WHICH
FORMS A COMPLETE COVERING OF THE
CEREBRAL HEMISPHARE.
. OUTTER MOST LAYER OF THE
CEREBRAL.
. It represents the highest degree of
evolutionary development of the human brain
as compare to other parts.

ANANTOMY OF
CEREBRAL CORTEX
• IT IS MADE UP OF GRAY MATTER AND CONTAINS
APPROXIMATELY 10 BILLION DIFFERENT NEURONS.
• THE THICKNESS OF THE CORTEX VARIES FROM
1.5 TO 4.4 mm.
• THICKEST OVER CREST OF A GYRUS.
• THINNEST OVER DEPTH OF SULUS.

CELLUAR
COMPOSITION
 DIFFERENT TYPES OF NERVE CELLS THAT ARE
PRESENT IN THE CEREBRAL CORTEX-
• 1. PYRAMIDAL CELLS
• 2. STELLATE CELLS
• 3. FUSIFORM CELLS
• 4. HORIZONTAL CELLS OF CAJAL.
• 5. CELLS OF MARTINOTTI

TYPES OF CERBRAL
CORTEX
• ACCORDING TO THE STRUCTURAL DEVELOPMENT.
• 2 TYPES- (i) ALLOCORTEX
(ii) ISOCORTEX / NEOCORTEX
(i) ALLOCORTEX
• STRUCTURAL SIMPLE MADE UP OF 3 LAYERS.
• ASSOCICATED WITH OLFACTORY CORTEX AND
HIPPPOCAMPUS.

(ii) NEOCORTEX
• STRUCTURALLY COMPLEX – HAS 6 LAYERS
• FORMS THE MAJOR PART OF CEREBRAL CORTEX.
• SUBDIVIDED INTO 2 CORTEX-
(i) GRANULAR COTEX (sensory cortex)
(ii) AGRANULAR CORTEX (motor cortex)

LAYERS OF CEREBRAL CORTEX
( neocortex)
• IT IS DIVIDED INTO 6 LAYERS THAT COULD BE
DISTINGUISHED BY TYPE,DENSITY AND
ARRANGEMENT OF THE CELLS-
• I. MOLECULAR LAYER ( Plexiform layer )
• II. EXTERNAL GRANULAR LAYER
• III. EXTERNAL PYRAMIDAL LAYER
• IV. INTERNAL GRANULAR LAYER
• V. INTERNAL PYRAMIDAL LAYER
• VI. MULTIFORM LAYER

FUNCTIONAL AREAS
OF CEREBRAL CORTEX
 DIFFERENT AREAS OF THE CEREBRAL CORTEX ARE
FUNCTIONAL SPECIALIZED.
• ANATOMICALY- 3 BASIC FUNCTIONAL AREAS
1. MOTOR AREA
2. SENSORY AREA
3. ASSOCIATION AREA
• HISTOLOGICALLY-
• PRECISE DIVISION OF THE CEREBRAL CORTEX INTO DIFFERENT
AREAS OF SPECIALIZATION- KNOWN AS BRODMANN AREAS.
• THERE ARE APPROXIMATELY 52 MAJOR AREAS DESCRIBED BY
BRODMANN.
• In addition, these Brodmann areas have been widely redefined,
discussed, debated, and refined exhaustively based on
cytoarchitecture, cortical functions, and brain plasticity.

MOTOR AREAS
• AREA ON THE CEREBRAL CORTEX THAT INVOLVES
WITH PLANNING, CONTROL AND EXECUTION OF
VOLUNTARY MOVEMENTS.
• THESE HAVE BEEN IDENTIFIED ON THE BASIS OF
ELICITATION OF MOTOR RESPONSE AT LOW
THRESHOLD OF ELECTRIC STIMULATION WHICH
GIVES RISE TO CONTRACTION OF SKELETAL
MUSCULATURE.
• THESE AREAS GIVE RISE TO COTICOSPINAL AND
CORTICONUCLEAR FIBERS.

I. PRIMARY MOTOR AREA
• LOCATION:- FRONTAL LOBE (the precentral gyrus and
precentral lobe).
• BRODMANN AREAS :- 4
• FUNCTION:- CONTROLS VOLUNTARY MOVEMENTS ACTIVITIES
OF
THE OPPOSITE HALF OF BODY.
• EFFECTS OF LESION :- (i)CONTRALATERAL PARALYSIS
(ii) Jackonian seizures (type of a focal seizure)

II. PREMOTOR AREA
• LOCATION :- FRONTAL LOBE (posterior part of
superior, middle and inferior frontal gyri)
• BRODMANN AREAS: – 6
• FUNCTION :- CONTROLS EXTRAPYRAMIDAL
SYSTEM
• EFFECTS OF LESION:- MOTOR APRAXIA
(inability to perform skilled movement that what once learned)

IV. MOTOR SPEECH AREA
(BROCA’S AREA)
• LOCATION :- FRONTAL LOBE (inferior part of frontal
gyrus)
- it is present on the left hemisphere in 98% of
right handed population and 70% in left handers.
• BRODMANN AREAS: - 44, 45
• FUNCTIONS:- CONTROL THE SPOKEN SPEECH
• EFFECTS OF LESION:- BROCA’S APHASIA
[ Non- fluent, impaired repetition but good comprehension]

V. PREFONTAL CORTEX
• LOCATION :- FRONTAL LOBE (anterior large part of
frontal lobe)
• BRODMANN AREAS: 9, 10, 11, 12
• FUNCTIONS:- CONTROLS CONCENTRATION,
EMOTIONS,ATTENTION AND JUDGEMENT.
• EFFECTS OF LESION:- (i) LOSS OF ORINENTATION
(ii) FRONTAL LOBE SYNDROME

SENSORY AREAS
• CORTICAL AREAS LINKED WITH SENSORY
FUNCTION.
• PRINCIPALLY THE THALAMUS RELAY A LARGE PART
OF THE SENSORY SIGNALS TO THE SENSORY
CORTEX FOR ANALYSIS.
• MAINLY INVOLVES IN –
(i) SPATIAL RECOGNITION
(ii)RECOGNITION OF INTENSITY OF SENSORY
STIMULUS
(iii) RECOGNITION OF SIMILARITY & DIFFERENCE OF
SENSORY STIMULUS

I. SOMATOSENSORY
AREAS
• LOCATION :- PARIETAL LOBE ( Posterior of central
sulcus )
• BRODMANN AREAS: - 1, 2, 3
• FUNCTIONS:- (i) PERCEPTION OF EXTEROCEPTIVE
IMPULSES LIKE – TOUCH , PAIN , TEMPERATURE.
(ii) PROPRIOCEPTION
• EFFECTS OF LESION:- (i) POOR LOCALIZATION OF
STIMULUS
(ii) LOSS OR ABNORMAL OF DISCRIMINATIVE
SENSATIONS.
(iii) PROPRIOCEPTION IMPAIRMENT

CORTICAL
HOMUNCULUS
• PICTORIAL REPRESENTATION OF MOTOR &
SENSORY CORTEX. SURFACE AREA OF THE
CORTEX IS DEDICATTED TO A PARTICULAR BODY
PART.

• IN THE SENSORY CORTEX RECEIVED SENSATION FROM A
PARTICULAR PART OF A BODY IS NOT PROPORTIONAL TO
THE SIZE OF THAT PART OF THE BODY BUT RATHER TO
INTRICACY OF SENSATORY INPUT RECEIVED FROM IT.
• THUS, THE THUMB, FINGER, LIPS AND TONGUE HAVE A
DISPROPROTIONATELY LARGE REPRESENATION.

ASSOCIATION AREAS
• IN THESE REGIONS, DIRECT SENSORY OR MOTOR
REPONSE ARE NOT ELICITED.
• FUNTIONS OVERLAP IN SAME REGION OF CORTEX.
• IT THE MOTOR FUNCTION IS PREDOMINANT IT IS
KNOWN AS MOTOR SENSORY (MS)
• DOMINANT SENSORY FUNCTION AREA IS KNOWN
AS SENSORIMOTOR AREA (SM)

I. SENSORY ASSOCIATION
AREA
• LOCATION :- PARIETAL LOBE ( between sensory &
visual areas )
• BRODMANN AREAS: - 5, 7
• FUNCTIONS:- mainly STEROGNOSIS
• EFFECTS OF LESION:- ASTEROGNOSIS

II. RECEPTIVE SPEECH
ASSOCIATION AREA
WERNIKE’S AREA
• LOCATION :- inferior part of PARIETAL LOBE
• BRODMANN AREAS: mainly 22, also 38,42,21
• FUNCTIONS:- SENSORY SPEECH
• EFFECTS OF LESION:- WERNIKE’S APHASIA
[ fluent speech but poor comprehension]

AREAS OF SPECIAL
SENSATIONS
 VISION
I. VISUAL SENSORY AREA
• LOCATION :- OCCIPITAL LOBE
• BRODMANN AREAS: 17
• FUNCTIONS:- RECEPTION AND PERCEPTION OF
VISUAL IMPRESSIONS OF – COLOUR,SIZE, FORM,
MOTION, ILLUMATION & TRANSPARENCY.
• EFFECTS OF LESION:- HOMONYMOUS
HEMIANOPIA.

II. VISUAL PSYCHIC AREA
• LOCATION :- OCCIPITAL LOBE
• BRODMANN AREAS:- 18, 19
• FUNCTIONS:- COMPLEX ASPECTS OF VISION-
CORRELATION OF VISUAL IMPULSES WITH PAST
MEMORY AND RECOGNITION OF OBJECT SEEN.
• EFFECTS OF LESION:- VISUAL AGNOSIA
( inability to recognize visually present object)
Example:- PROSOPAGNOSIA (Face blindness)

 HEARING
I. AUDITORY SENSORY AREA
• LOCATION :- TEMPORAL LOBE
• BRODMANN AREAS :- 41, 42
• FUNCTIONS:- RECEPTION AND PERCEPTION OF
AUDITORY IMPRESSIONS OF – LOUDNESS ,
QUALITY & PITCH.
• EFFECTS OF LESION:- IMPAIRED HEARING
(CORTICAL DEAFNESS) (usually the loss is greater in
one ear then another)

II. AUDITORY PSYCHIC AREA
• LOCATION :- TEMPORAL LOBE
• BRODMANN AREAS :- 22
• FUNCTIONS:- CORRELATION OF AUDITORY
IMPULSES WITH PAST MEMORY AND
IDENTIFICATION OF SOUNDS HEARD.
• EFFECTS OF LESION:- AUDITORY AGNOSIA
( inability to recognize or differentiate between sounds even
with intact hearing)

REFRENCES:-
• GRAY’S ANATOMY , 38TH EDITION
• RICHARD S. SNELL, CLINICAL NEUROANTOMY , 6TH
EDITION
• LESLIE P. GARTNER, TEXTBOOK OF
NEUROANATOMY, 2ND EDITION.
• INDERBIR SINGH, TEXTBOOK OF HUMAN
NEUROANATOMY.
• BD CHAURASIA’S 4TH VOLUME.
• VISHRAM SINGH, 3RD VOLUME.
• PICTURE CREDITS:- KENHUB.COM

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