Brodmann’s areas 3, 1, 2

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  German neurologist 1868-1918 Born in Liggersdorf , province of Hohenzollern Received his studies from places like Munich, Berlin, University of Laussane , University of Jena, Frankfurt mental asylum He met Alois Alzheimer in 1901, who influenced his decision to pursue neuroscience. He was accompanied in his work with Cecile and Vogt 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 Brodmann area (BA) 3 is subdivided into areas 3a and 3b. 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 . BA 3b is now conceived as the primary somatosensory cortex because it receives dense inputs from the NP nucleus of the thalamus its neurons are highly responsive to somatosensory stimuli, but not other stimuli lesions here impair somatic sensation 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. T he 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