Cerebral cortex 18 april 2016pdf

Cerebral cortex: functional areas
Dr. Madanmohan. MD, DSc, FIAY
Professor & Head
Department of Physiology

Learning objectives
1. Give the similarities and differences between
brain and computer.
2. State the differences between allocortex and
neocortex.
3. Name the functional areas of different lobes of
brain.
4. Name the components and functions of
prefrontal cortex.
5. Briefly describe the functions of cortical
association areas.
6. List the differences between categorical and
representational hemispheres.

Scheme of talk
• Introduction
• Functional areas of brain
• Association areas of brain
• Complementary specialization
• Methods of study

Introduction
• Highest level of functioning:
intelligence, behavior, perceives,
interprets, stores, responds, regulates.
• 100 billion (1011) neurons
Each neurone has 103 synapses
1011 neurons have 1014 synapses
• Extensive connections, functional overlap

Brain and computer
Common terms: input/output, processing,memory
Computer:
• Faster, more accurate, memory is permanent
• Follows program blindly, no creativity or
abstract thought
• Modern computers have artificial intelligence

Cerebral cortex
Frontal, parietal, temporal, occipital
Limbic system
Hypothalamus
Functional coupling
endo ANS somatic
Pituitary Brain stem
Int. responses (Hs) Ext. responses
Contd…

… Contd
Internal responses: External responses:
Metabolism. Behaviour:
Cardiovascular …. Eating, drinking
adjustments.

1. Allocortex / archipallium: 3 cell layers
8%. primitive, heterotypical, limbic
2. Neocortex / neopallium / ioscortex:
6 layers, highly developed in humans
3. Juxtallocortex: transitional cortex,
cingulate, insula

Frontal lobe
1. Primary motor area. 4. Pre-rolandic gyrus
Topographical map, upside down.
Stimulation: movement in opposite half
Lesion: contralateral paralysis
Double lesion: severe paralysis
Movement, execution, behavior

2. Supplementary motor area:
Medial frontal gyrus,
medial surface of hemisphere.
Higher order motor control
Stimulation: threshold is higher
Lesion: temporary paralysis

3. Pre motor area: 6, 8
Stimulus: intricate movements
Lesion: less severe paralysis
Skilled movement lost
Destruction of 4, 6, 8:
severe contralateral paralysis

4. Frontal eye field: 6, 8, 9
Connected to visual cortex.
Voluntary scanning movements
Stimulus: conjugate movements of eyes
to opposite side
5. Broca’s motor speech area: 44, 45
Lesion in categorical hemisphere:
expressive aphasia
can understand written or spoken words
6. Micturition center: medial frontal lobe

7. Prefrontal cortex: 9,10,11,12,24,32
Frontal, orbital, medial frontal gyrus.
Extensive area, numerous connections.
Associates somatic and visceral functions.
Functions:
i) Discrimination & judgement
ii) Emotions
iii) Personality
iv) Behavior
Frontal leukotomy /lobectomy:
for intractable pain and stress.

Parietal lobe
Perception, integration
1. Primary sensory (somesthetic) area (SI) 3,1,2
Post central gyrus, upside down.
Orderly representation of opposite ½
Stimulation: sensory experiences.
Lesion: sensory disturbances/loss
more in distal parts
Bilateral lesion: severe loss

2. Secondary somesthetic area: S II
Superior lip of posterior limb of lat. fissure
Body completely represented: face ant.
3. Somesthetic association area: 5, 7
Sup. parietal lobe, supramarginal gyrus
Receives & integrates sensory modalities
Sensory discrimination, i.e., warm from warmer
Lesion: astereognosis. Neglects opp ½ of body
4. Taste: 43 postcentral gyrus
5. Visceral: insula, buried in lateral sulcus

Occipital lobe
1. Primary visual area: 17
2. Secondary visual area: 18
Visual association/psychovisual area.
3. Occipital eye field: 18,19
Sti: conjugate deviation to opposite side

Temporal lobe
1. Primary auditory area: 41, 42
Inferior wall of lateral sulcus
Receives sound from both sides
2. Secondary auditory area: 22
Intepretation of sound.
Lesion:
unable to intepret sound (word deafness).

3. Olfactory area: Limbic system.
Olfactory cortex, ant olfactory nucleus,
pyriform cortex, olfactory tubercle.
4. Taste: 43
Taste area I: near area for tongue
Taste area II: deep in insular cortex
5. Vestibular area: posterior parietal cortex
Afferents: i) vestibular system
ii) visual association area
iii) auditory association area

Bilateral temporal lobectomy
(Kluver – Bucy monkey)
1. Change in emotional state and behavior
2. Change in dietary habits and sexual behavior
3. Docile, distractable
4. Loss of recent memory

• Primary sensory & motor areas: <10 %
• Association areas >90 %
• Immense growth in humans
• Large areas, multiple connections,
complex functions
• Store, integrate, associate, interpret

• Primary motor & sensory aareas: <10%
4 3,1,2 17 41
• Unimodel association areas:
6,8 5,7 18 22

Heteromodel association areas:
Parietal-occipto-temporal: 30, 40……
Language: Computes somatosensory, visual and
auditory information
Pre-frontal (frontal): 9, 10, 45, 46, 47……
Complex, high order functions

Complementary specialisation
Categorical (dominant ?)
Language, sequential analysis
Occipital lobe wider
Lesion: language disorder,
depressed
Representational
Visuospatial, spatio-
temporal, recognize faces,
musical themes
Frontal lobe thicker
Lesion: astereognosis,
euphoric,
unconcerned

Cell layers: 3 in allocortex, 6 in neocortex
1. Molecular (plexiform) layer: outer
2. External granular layer
3. Pyramidal cell layer
4. Internal granular layer
5. Internal pyramidal / ganglionic layer
6. Fusiform cell layer

1.Electrophysiology: normal volunteers
neurosurgery, EEG, EP, stimulation, NC, EMG.
2.Imaging: plain x-ray, CAT, MRI, PET, SPECT,
fMRI.
3.Biochem / molecular: blood, urine, CSF (LP).
4.Clinico-pathological: biopsy, autopsy, denervation,
degeneration.
5.Ablation: animals, patients, stereotaxy.
6.Pharmacological: drugs, neurotransmitters.
7.Embryo transplant.
Methods of study

Cerebral cortex 18 april 2016pdf

Cerebral cortex 18 april 2016pdf

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Cerebral cortex 18 april 2016pdf