This document summarizes the anatomy and functions of different areas of the cerebral cortex. It describes the allocortex which makes up 10% of the cortex, and the neocortex which is the remaining 90%. It then discusses the six layers of the neocortex and different cell types. It provides details on agranular and granular cortices and their characteristics. Specific areas of the cortex are then described in more detail such as the frontal, parietal, and polar cortices. The document outlines different classification schemes for cortical areas and focuses on the 52 areas described by Brodmann. It provides in-depth descriptions of the primary motor, premotor, frontal eye field, supplementary motor, and prefrontal cortical areas.

1. DR PRATIK MISTRY

4.  Allocortex – 10 % (also called Limbic Cortex)
i. Archipallium – hippocampus & Dentate gyrus.
ii. Paleopallium – Uncus & part of Parahippocampal
gyrus.
iii. Mesocortex. – transitional zone.
 Neocortex (Isocortex) -Rest of 90% of cerebral cortex.

5.  Six layers
1. Molecular
2. Outer granular
3. Outer pyramidal
4. Inner granular
5. Inner pyramidal
6. Pleomorphic
 Cells:
1. Pyramidal cells of betz
2. Granule (stelate) cells
3. Cells of martinoti
4. Horizontal cells of cajal

6.  AGRANULAR CORTEX
 Pyramidal cells – large,
Betz cells
 Granule cells absent or
less in number
 Seen in Motor cortex (4)
& Boca's motor speech
area (44)
 GRANULAR CORTEX
 Excess granule cells
 Few pyramidal cells
 Seen in sensory cortex &
visual area, auditory area

7.  FRONTAL CORTEX
 Small and medium
pyramidal cells
 Few stellate cells
 Pre-frontal cortex of
frontal lobe
 PARIETAL CORTEX
 More stellate cells
 Seen in most of parietal lobe &
junction of parietal, temporal &
occipital lobes
 POLAR CORTEX
 Thinnest of all
 All layers reduced depth.
 Seen in frontal & occipital pole

8.  For functional analysis, cerebral
cortex is divided into number
areas,
20 areas of Campbell
109 areas of Economo
200 areas of Vogt
52 areas of brodmann- frequently
used
 Subdivided into motor, sensory
and association areas

11.  Subdivided into
 Primary motor area (area 4)
 Pre-motor area (area 6)
 Frontal eye field (area 8)
 Supplementary motor area
 Pre-frontal area (areas 9 to 12)

12. Location:
 Precentral gyrus (area 4)
 Extends to the ant. part of
paracentral lobule
 Agranular cortex
Afferents :
 Premotor area (Area 6)
 Somesthetic or
somatosensory cortex
 Ant. Part ventral nucleus of
thalamus(which receives
info. from cerebellum
 Basal ganglia

13. Efferents :
 Fibres from area 4 and
area 6 forming…
1. Corticospinal
2. Corticonuclear
3. Corticobulbar tracts.
 Regulate the voluntary
movements of opposite
side of body
 Fronto-pontine fibres
 Corpus striatum, red
nucleus

14.  Control movements of
voluntary muscles of opposite
side
 Movements represented with
head end below and leg end up
(INVERTED MOTOR
HOMUNCULUS)
 Centres from below are: lips,
tongue, larynx, pharynx, face,
head & neck, upper limb with
large area for fingers and hand,
trunk, lower limb above knee.
 Ant. Part of paracentral lobule
 Extent of area depend on skill of
movement and not on the bulk
of muscle

15.  Somewhat sensory. Receive some sensations like
tingling and numbness
 Known as MSI
 Muscles of forehead, tongue, mastication, larynx,
pharynx, extra ocular bilaterally represented
 Only movements not muscles
 LESION: initially flaccid paralysis

16. Location (area 6):
 In front of area 4, include
post. Part of sup., middle
and inf. Frontal gyri
 On medial side, continue
with supplementary motor
area
 Agranular & motor

17.  Integrates voluntary movements to perform skilful act.
 Writing centre
 Concerned with programming which is executed by
area 4
LESION:
 Produce difficulty in the performance of skilled
movements.
 Apraxia: loss of the ability to do simple or routine acts
in the absence of paralysis.
 Agraphia: when writing is also involved.

18. PRIMARY SOMATOMOTOR
AREA (MSI)
=
PRIMARY MOTOR AREA
PREMOTOR AREA

19.  Lie in front of area 6
 Involve posterior part of middle
frontal gyrus
 Agranular cortex
 Regulate voluntary conjugate
movements of eye. Deviation of
eyes to the opposite side
 Controls voluntary scanning
movements of the eyes and is
independent of the visual
stimuli.
 Connected to the visual area of
occipital cortex by association
fibres.
 Lesion of the area cause two eye
to deviate to the side of lesion

20.  Located on medial surface
of cerebrum in the post.
part of medial frontal gyrus
anterior to the paracentral
lobule
 Afferents from VA and VL of
thalamus
 Efferents to area 4
 Function is to control
complex movements.
Produce sensation of “URGE
TO MOVE’
 Receive some senses (MSII)
 Lesion of area produce
AKINESIA

21.  Rest of frontal lobe ant. to pre-motor
area which include orbital surface also
 Fibres from thalamus, hypothalamus,
limbic system, all areas of cortex
 Concerned with individual’s
personality
 Regulate depth of feeling, thinking,
mature judgement, orientation,
concentration, pleasure and
displeasure, right or wrong.
 Bilateral damage due to trauma or
tumour: change in personality, loss of
concentration, judgement,
inappropriate social behaviour like
vulgarity of speech, improper clothing

22. Primary Secondary Sensory Association
Somesthetic (sensory) Visual Auditory

23.  Primary somesthetic
areas (areas 3,1,2)
 Secondary somesthetic
area
 Somesthetic association
are (areas 5,7)

24.  Located in the post-central
gyrus and extends into the
posterior part of the
paracentral lobule on the
medial surface.
 Granular cortex
 Afferents from VPL and
VPM of thalamus and other
areas of cortex

25.  Localise, analyse, discriminate
all modalities of sensations
 Sensations represented with
head end below (INVERTED
SENSORY HOMUNCULUS)
 Paracentral lobule receive
sense of distension from
bladder and rectum
 Hand, face, tongue, lips having
larger representation in cortex
 Lower part act as taste centre
(area 43)
 Modulate sensory input
 Secondarily motor (SMI)

26.  Located on the posterior part of posterior ramus of
lateral sulcus
 Involve lower part of pre and post-central gyri
 Receive mainly pain sensation
 Somewhat motor in function (SMII)

27.  Located in the superior
parietal lobule
 Connected with higher
association area in supra-
marginal gyrus (area 40)
 Concerned with the
perception of shape, size,
roughness, and texture of
the objects
 Stereognosis- ability to
identify known objects in
hand with closed eyes
 Astereognosis or Tactile
agnosia

28.  Primary visual area
(area 17)
 Visual association
area (area 18 & 19)
 Higher visual
association area
(area 39)

29.  Located in the lips and walls
of posterior part of calcarine
sulcus which include cuneus
and lingual gyrus
 Thinner and granular cortex
 Stria of gennari
 Afferents from optic radiation
 Temporal half of same retina
and nasal half of opposite
retina
 Register opposite field of
vision

30. Macular area-
 occupying approximately
posterior one-third of the
visual cortex.
 is the central area of retina
and responsible for maximum
visual acuity (keenest vision)
has extensive cortical
representation
 Connected to area 18, 19 of
both sides
 Concerned with reception and
perception of simple visual
impressions like colour, size,
form, transparency etc.

31.  Unilateral lesion due to
thrombosis, trauma
produce partial blindness
(hemianopia) with
macular vision retained
 Macular sparing because
it is supplied by both
MCA and PCA

32.  Occupy rest of occipital
lobe and calcarine sulcus
 Afferents from area 17
 Occipital eye field-
produce involuntary
deviation of eyes reflexly

33.  Located in the angular gyrus
of inferior parietal lobule
 It relate visual information
to the past experience, thus
enabling person to
recognize and identify the
object by vision
 Lesion of this area- visual
agnosia- inability to
recognize known objects by
vision
 Sensory aphasia (word
blindness)- inability to
recognize written word

34.  Primary auditory
area (area 41)
 Auditory association
area (area 42)
 Higher auditory
association area
(Wernicke's area)
(area 22)

35.  Involve anterior transverse
temporal gyrus (of
Heschl), on the upper part
of sup. temporal gyrus
 Granular cortex
 Afferents from MGB as
auditory radiation
 Detect the changes in
frequency and direction
from where sound
originates
 Unilateral lesion no
deafness due to bilateral
presentation

36.  Lie behind area 41
 Involve posterior
transverse temporal
gyrus of superior
temporal gyrus
 Granular cortex
 Same function

37.  Wernicke’s area
 Rest of the area
 Afferents from area 41 &
42
 Interpretation of sounds
and comprehension of
spoken language from
past auditory experiences
 Lesion produce sensory
aphasia (word deafness)-
unable to interpret the
spoken words.

38.  Taste area (area 43)-
lower part of inf. parietal
lobule
 Vestibular area- lower
part post-central gyrus
near face area
 Olfactory area (area 28)-
anterior part of
parahippocampus gyrus
and uncus

39.  Speech- highly complex function
 Speech function performed by dominant hemisphere
 In 90%, left one, DOMINANT (TALKING BRAIN) &
right one, NON DOMINANT (MUTE BRAIN)
 FOUR SPEECH CENTRES: 3 sensory & 1 motor
 Sensory speech areas:
1. Area 22 (Wernicke's area)
2. Area 39
3. Area 40
 Broca’s motor speech area (area 44 & 45)

40.  Area 22 (Wernicke’s area)
 Interpret spoken language &
recognize familiar words
 Congenital deaf child-
dumb
 Area 39 of angular gyrus-
store visual images and
recognize them by sight
 Area 40 of supramarginal
gyrus- recognize familiar
objects by touch and
proprioception
 All these 3 areas receive
input from hearing,
vision, touch and process
it in the area 22 &
 Then project it to Broca’s
area through ARCUATE
FASCICULUS

41.  Located in the pars
triangularis and pars
posterior of inferior
frontal gyrus
 Afferents from area 22
 Efferents to the muscles
of tongue, lips, larynx,
pharynx, palate, face for
production of speech

42.  Area 22- word deafness- unable to interpret spoken
words. Speak fluently with incorrect and useless words
 Area 39- word blindness- inability to recognize
written words even written by self
 Alexia, Agraphia
 Area 40- Astereognosis
 Area 44 & 45- motor aphasia- cannot speak properly
although he understand everything. Slow speech with
many grammatical mistakes
 Conduction aphasia- arcuate fasciculus damage