The cerebral cortex consists of two hemispheres covered in convoluted gyri and sulci. It is the largest part of the human brain. The hemispheres are separated by a fissure and connected by the corpus callosum. The neocortex, or association cortex, is the phylogenetically newest part responsible for higher functions like language, memory, and intelligence. It is divided into four lobes - frontal, parietal, temporal, and occipital - each with distinct functions. The left hemisphere is typically dominant for language and logical thinking.

1. Cerebral cortex
Dr Anu Priya J

2. • The adult human brain weighs
on average about 1.5 kg with a
volume of around 1200cm3
• The cerebral hemispheres form
the largest part of the human
brain
• The hemispheres are covered
with a cortical layer with a
convoluted topography, sulci and
gyri

3. • Separated from each
other in the upper part
by a median longitudinal
fissure
• In the lower part, the
hemispheres are
connected by the corpus
callosum

4. • Neocortex (Association cortex)
• Cerebral dominance (Cerebral asymmetry)
• Lobes of cerebral cortex

5. Neocortex (Association cortex)

6. Neocortex (Association cortex)
• Phylogenetically newest part of the cortex
• The seat of all higher functions (not only
sensori-motor association but also intellect,
language, speech, personality, learning &
memory)

7. Functional organization
• Frontal or Prefrontal association cortex
• Parietal-occipital-temporal association cortex
• Temporal association cortex
• Limbic association cortex

8. Functions of neocortex
• Language function – dominant hemisphere
(categorical hemisphere)
• Fn of the association cortex located in the temporal
region & language areas (mostly left side –
Wernicke’s area, Angular gyrus, Frontal motor
speech areas)
– Understand the spoken and written words
– Express ideas in speech and writing

9. • Recognition of faces – non-dominant hemisphere
(representational hemisphere)
• Right inferior temporal lobe – integrate & store
information regarding recognition of faces – receive
visual input from objects, particularly the visual
impression of faces
Lesion
• Prosopagnosia – inability to recognize faces (recognize
known people by their voice, but not by seeing their
faces)
Functions of neocortex

10. • Calculation
– Inferior part of left frontal lobe – actual
calculation
– Areas around the intraparietal sulci – memorizing
numbers & finger counting
• Lesion
– Acalculia – impairment of mathematical ability
Functions of neocortex

11. Navigation
• Sense of direction-findings
– Right side hippocampus
– Right side caudate nucleus
Functions of neocortex

12. Histology of neocortex
• The neocortex is composed
of 6 layers I to VI from
outside to inside
Three types of cells can be
identified
• Pyramidal cells
• Stellate or granule cells
• Fusiform cells

13. Cerebral asymmetry
(Cerebral dominance)

14. Cerebral asymmetry
• Dominant – categorical – language, calculation
• Nondominant – representational – recognise
faces, navigation
• Mostly left hemisphere dominant
• Not associated with handedness
• Explain the functions : Refer Neocortex

15. Lobes of the cerebral cortex

16. Lobes
• Each hemisphere is
divided into 4 lobes

18. Frontal lobe
Subdivided into
• Precentral cortex
• Prefrontal cortex

19. Areas of precentral cortex
• Primary motor area –
Brodmann’s area 44 and 45
• Premotor area –
Brodmann’s area 6, 8, 4
and 45
• Supplementary motor area

20. Prefrontal cortex
• Also known as
orbitofrontal cortex
• Lies anterior to area 8
and 44

21. Functions
• Centre for planned actions –
plans complex patterns and
sequence of motor movements
• Centre for higher functions –
centre for learning, emotions,
memory, social behaviour
• Seat of intelligence - short term
memories are stored and
recalled.
• “Organ of mind”

22. Control of intellectual activities
• To prognosticate
• To plan for the future
• To concentrate on a theme of thought, elaboration of thought
• Delays actions in response to incoming signal to obtain best
response
• Consideration of consequences of motor action
• Solution of complicated mathematical and philosophical problems

23. Frontal lobe syndrome
• Bilateral prefrontal lobectomy
• Phineas case – rod pierced brain
• Flight of ideas – difficulty in planning
• Emotional instability – lack of restraint –
hostile,aggressive,restless
• Impairment of recent memory alone; remote memories intact
• Loss of moral and social sense
• Lack of attention & concentration power
• Lack of initiative – reducing mental drive
• Functional abnormalities – hyperphagia, loss of control over
urinary or rectal sphincters, orientation disturbance, slight
tremors

24. Parietal lobe
• Primary sensory area –
Brodmann’s areas 3, 1
and 2  S1
• Secondary sensory area
 S2
• Sensory association
area – Brodmann’s area
5 and 7

25. Lesion in primary sensory area S1
• When lesion is confined
to sensory cortex,
sensations are perceived
but discriminating
functions are lost
• When thalamus is also
involved, there is loss of
sensations

26. Secondary sensory area
• Lesion causes deficits in
discrimination power
• Sensory processing in
S1 is preserved

27. Sensory association area
• Lesion in area 40
produces tactile
agnosia- astereognosis
and tactile aphasia

28. Temporal lobe
• Primary auditory cortex (41,42)
• Auditory association area (20,21,22)

29. Unilateral removal of temporal lobe
• Does not cause deafness as each ear is bilaterally
represented
• Removal of one auditory cortex has only a slight
effect on auditory acuity i.e. sharpness of hearing

30. Temporal lobe syndrome
• Also known as Kluver-Bucy syndrome
• Produced experimentally in animals after removal
of bilateral temporal lobe along with amygdala and
uncus
• Hyperphagia, omniphagia, increased oral activity,
hypersexuality

31. Features of temporal lobe syndrome
• Aphasia – disturbance in speech
• Auditory disturbances – tinnitus, auditory
hallucinations with sounds like buzzing,
ringing or humming

32. Wernicke’s aphasia
• Comprehension for spoken and
written language is impaired
• Language output is fluent but
highly paraphasic and
circumlocutious
• Jargon aphasia – string of
neologism
• Language contains few
substantive nouns  speech is
voluminous but uninformative
22

33. Occipital lobe
• Primary visual cortex - area 17 –
perception of visual impulses
• Visual association area – Area 18
and 19 – recognition and
identification of objects with
past experience
• Occipital eyefield – Area 19 –
movements of eyeball

34. Modified nomenclature of visual
areas
• V1 – first visual area – Area 17
• V2 – second visual area – greater
part of Area 18
• V3 – third visual area – narrow
strip of Area 18
• V4 – fourth visual area – Area 19
• V5 – fifth visual area – posterior
end of temporal gyrus

35. Lesion in visual cortex
• Loss of perception of visual
impulses
• Loss of recognition and
identification of known
objects

36. Thank you