brodmann’s areas 3, 1, 2

BRODMANN’S AREAS

GUIDE- DR. L. S. PATILPRESENTER-DR. DEEPAK CHINAGI

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

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.

KORBINIAN BRODMANN 1. German neurologist2. 1868-19183. 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

BROADMANN AREA 1,2,3

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.

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

PARTS OF PRIMARY SOMATOSENSORY CORTEX

1. Brodmann area (BA) 3 is subdivided intoareas 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 sensation4. 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

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.

CYTOARCHITECTURE OF SOMATOSENSORY CORTEX

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

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

SENSORY HOMUNCULUS

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)

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.


• Astereognosis (bilateral) / tactile agnosia (unilateral) – inability to identify objects by handling them blindfolded.

• Basic shapes – pyramids , spheres etc• Advanced shapes – tuning fork ,


• 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


• Loss of vibration , proprioception and fine touch - because third order neuron of medial lemniscal pathway cannot synapse in the 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.


• Hemispatial neglect - two types– Motor hemineglect– Sensory hemineglect

• Theories of hemineglect– Spatial attention– Spatial representation


• 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.

Thank You

brodmann’s areas 3, 1, 2

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