BROADMANN AREA 1,2,3 Grouped as primary somatosensory cortex. Location – Post-Central gyrus on lateral surface of brain. Tactile representation is orderly arranged (in an inverted fashion) from the toe (at the top of the cerebral hemisphere) to mouth (at the bottom)

1. BRODMANN’S AREAS
GUIDE- DR. L. S. PATIL
PRESENTER-DR. DEEPAK CHINAGI

2. At the end of this presentation, you
will be able to know. . .
• Historical aspect of brodmann’s areas.
• Discussion about brodmann’s areas 3 , 1 , 2.
• Primary somatosensory cortex and its
relations
• Cytoarchitecture and its interconnections
• Sensory Homonculus
• Clinical significance of lesions at
somatosensory cortex

3. KORBINIAN BRODMANN
• Korbinian Brodmann (17 November 1868 – 22
August 1918) .
• German neurologist who became famous for
his definition of the cerebral cortex into 52
distinct regions from their cytoarchitectonic
(histological)characteristics.

4. KORBINIAN BRODMANN
1. German neurologist
2. 1868-1918
3. Born in Liggersdorf, province of Hohenzollern
4. Received his studies from places like Munich,
Berlin, University of Laussane, University of Jena,
Frankfurt mental asylum
5. He met Alois Alzheimer in 1901, who influenced his
decision to pursue neuroscience.
6. He was accompanied in his work with Cecile and
Vogt
7. He published his original research on cortical
cytoarchitectonics in 1909. he divided the brain
regions into 52 areas based on anatomy and
histology of cortical projections

5. BROADMANN AREA 1,2,3

6. BROADMANN AREA 1,2,3
• Grouped as primary somatosensory cortex.
• Location – Post-Central gyrus on lateral
surface of brain.
• Tactile representation is orderly arranged (in
an inverted fashion) from the toe (at the top
of the cerebral hemisphere) to mouth (at the
bottom) Refer figure of slide number 9.

7. RELATIONS
• Post central gyrus is bounded by
– Medially – medial longitudinal fissure
– Inferiorly – lateral sulcus
– In the front – central sulcus
– In the back – post central sulcus

8. PARTS OF PRIMARY SOMATOSENSORY CORTEX
1. Brodmann area (BA) 3 is subdivided into
areas 3a and 3b.
2. Whereas BA 1 occupies the apex of the
postcentral gyrus, the rostral border of BA 3a
is in the nadir of the Central sulcus, and is
caudally followed by BA 3b, then BA 1, with
BA 2 following and ending in the nadir of the
postcentral sulcus.
3. BA 3b is now conceived as the primary
somatosensory cortex because
1. it receives dense inputs from the NP
nucleus of the thalamus
2. its neurons are highly responsive to
somatosensory stimuli, but not other
stimuli
3. lesions here impair somatic sensation
4. electrical stimulation evokes somatic
sensory experience.
4. BA 3a also receives dense input
from the thalamus,however, this
area is concerned with
proprioception.
Anterior Posterior

9. INTERCONNECTIONS OF AREAS OF
SOMATOSENSORY CORTEX
• BA 3a receives dense inputs from thalamus =
concerned with proprioception
• BA 3b projects outputs to BA1 and BA2
– BA3b to BA1 = texture information.
– BA3b to BA2 = size and shape of the object.
• Clinical significance-??
– Lesions at these areas cause impairment of
concerned sensations.

10. CYTOARCHITECTURE OF
SOMATOSENSORY CORTEX

11. CYTOARCHITECTURE OF
SOMATOSENSORY CORTEX
• Somatosensory cortex is arranged in layers.
• The thalamic inputs project into layer IV,
which in turn project into other layers.
• As in other sensory cortices, S1 neurons are
grouped together with similar inputs and
responses into vertical columns that extend
across cortical layers

12. SENSORY HOMUNCULUS
• Homonculus = “little man” (Latin)
• A cortical homunculus is a physical
representation of the human body, located
within the brain.
• Two types of cortical homonculus:
– Motor homonculus – pre central gyrus
– Sensory homonculus – post central gyrus

13. SENSORY HOMUNCULUS

14. SOMATOTOPIC ORGANISATION
• Proposed by Wilder Penfield
• Legs and trunk – over midline
• Arms and hands – over middle part of
homonculus
• Face – bottom of homonculus
• Lips and hands are represented largeron the
homonculus (shows that more informayion
processed from these areas)

15. CLINICAL SIGNIFICANCE OF
SOMATOSENSORY CORTEX
• Agraphaesthesia – inability to identify written
letter of number traced on skin(parietal
damage/thalamic damage/damage to secondary
somatosensory cortex)
• A significant association is found in other diseases
like Alzheimer’s disease and schizophrenia.
• Palm writing test – X or O
• Forearm or abdomen can also be tested for
graphaesthesia.

16. CLINICAL SIGNIFICANCE OF
SOMATOSENSORY CORTEX
• Astereognosis (bilateral) / tactile agnosia
(unilateral) – inability to identify objects by
handling them blindfolded.
• Basic shapes – pyramids , spheres etc
• Advanced shapes – tuning fork ,

17. CLINICAL SIGNIFICANCE OF
SOMATOSENSORY CORTEX
• Hemihypesthesia – decreased sensitivity of
one side of the body.
• Due to damage to thalamocortical fibres in the
posterior limb of internal capsule.
• Blood supply – Anterior choroidal atery

18. CLINICAL SIGNIFICANCE OF
SOMATOSENSORY CORTEX
• Loss of vibration , proprioception and fine
touch - because third order neuron of medial
lemniscal pathway cannot synapse in the
cortex.

19. CLINICAL SIGNIFICANCE OF
SOMATOSENSORY CORTEX
• Hemispatial neglect ( also called
hemiagnosia/hemineglect) – inability of the
person to process and perceive the stimuli on the
one side of the body.
• Contralateral hemineglect is more common than
ipsilateral.
• Right side hemineglect is less common than left
side.
• Monothematic delusion – person denies
ownership of limb or affected side of the body.

20. CLINICAL SIGNIFICANCE OF
SOMATOSENSORY CORTEX
• Hemispatial neglect - two types
– Motor hemineglect
– Sensory hemineglect
• Theories of hemineglect
– Spatial attention
– Spatial representation

21. CLINICAL SIGNIFICANCE OF
SOMATOSENSORY CORTEX
• Loss of nociception , thermoception and crude
touch – these can occur but these are rare
because these are interpret by other areas of
brain also like insular cortex and cingulate
gyrus.

22. Thank You