Functional areas of the brain

FUNCTIONAL AREAS OF THE HUMAN CEREBRAL CORTEX.

1. FUNCTIONAL AREAS OF CEREBRAL CORTEX PRESENTED BY :- HARSHEKA KAR MOT(NEUROLOGY) I YEAR ISIC INSTITUTE OF REHAB SCIENCES

2. CEREBRAL CORTEX . IT IS A SHEET OF NEURAL TISSUE WHICH FORMS A COMPLETE COVERING OF THE CEREBRAL HEMISPHARE. . OUTTER MOST LAYER OF THE CEREBRAL. . It represents the highest d egree of evolutionary development of the human brain as compare to other parts.

3. ANANTOMY OF CEREBRAL CORTEX IT IS MADE UP OF GRAY MATTER AND CONTAINS APPROXIMATELY 10 BILLION DIFFERENT NEURONS. THE THICKNESS OF THE CORTEX VARIES FROM 1.5 TO 4.4 mm. THICKEST OVER CREST OF A GYRUS. THINNEST OVER DEPTH OF SULUS.

4. CELLUAR COMPOSITION DIFFERENT TYPES OF NERVE CELLS THAT ARE PRESENT IN THE CEREBRAL CORTEX- 1. PYRAMIDAL CELLS 2. STELLATE CELLS 3. FUSIFORM CELLS 4. HORIZONTAL CELLS OF CAJAL. 5. CELLS OF MARTINOTTI

5. TYPES OF CERBRAL CORTEX ACCORDING TO THE STRUCTURAL DEVELOPMENT. 2 TYPES- (i) ALLOCORTEX (ii) ISOCORTEX / NEOCORTEX (i) ALLOCORTEX STRUCTURAL SIMPLE MADE UP OF 3 LAYERS. ASSOCICATED WITH OLFACTORY CORTEX AND HIPPPOCAMPUS.

6. (ii) NEOCORTEX STRUCTURALLY COMPLEX – HAS 6 LAYERS FORMS THE MAJOR PART OF CEREBRAL CORTEX. SUBDIVIDED INTO 2 CORTEX- GRANULAR COTEX (sensory cortex) (ii) AGRANULAR CORTEX (motor cortex)

7. LAYERS OF CEREBRAL CORTEX ( neocortex) IT IS DIVIDED INTO 6 LAYERS THAT COULD BE DISTINGUISHED BY TYPE,DENSITY AND ARRANGEMENT OF THE CELLS- I. MOLECULAR LAYER ( Plexiform layer ) II. EXTERNAL GRANULAR LAYER III. EXTERNAL PYRAMIDAL LAYER IV. INTERNAL GRANULAR LAYER V. INTERNAL PYRAMIDAL LAYER VI. MULTIFORM LAYER

8. FUNCTIONAL AREAS OF CEREBRAL CORTEX DIFFERENT AREAS OF THE CEREBRAL CORTEX ARE FUNCTIONAL SPECIALIZED. ANATOMICALY - 3 BASIC FUNCTIONAL AREAS MOTOR AREA SENSORY AREA ASSOCIATION AREA HISTOLOGICALLY - PRECISE DIVISION OF THE CEREBRAL CORTEX INTO DIFFERENT AREAS OF SPECIALIZATION- KNOWN AS BRODMANN AREAS . THERE ARE APPROXIMATELY 52 MAJOR AREAS DESCRIBED BY BRODMANN.   In addition, these Brodmann areas have been widely redefined, discussed, debated, and refined exhaustively based on cytoarchitecture, cortical functions, and  brain  plasticity.

9. MOTOR AREAS AREA ON THE CEREBRAL CORTEX THAT INVOLVES WITH PLANNING, CONTROL AND EXECUTION OF VOLUNTARY MOVEMENTS. THESE HAVE BEEN IDENTIFIED ON THE BASIS OF ELICITATION OF MOTOR RESPONSE AT LOW THRESHOLD OF ELECTRIC STIMULATION WHICH GIVES RISE TO CONTRACTION OF SKELETAL MUSCULATURE. THESE AREAS GIVE RISE TO COTICOSPINAL AND CORTICONUCLEAR FIBERS.

10. I. PRIMARY MOTOR AREA LOCATION :- FRONTAL LOBE (the precentral gyrus and precentral lobe). BRODMANN AREAS : - 4 FUNCTION :- CONTROLS VOLUNTARY MOVEMENTS ACTIVITIES OF THE OPPOSITE HALF OF BODY. EFFECTS OF LESION :- (i)CONTRALATERAL PARALYSIS (ii) Jackonian seizures (type of a focal seizure)

11. II. PREMOTOR AREA LOCATION :- FRONTAL LOBE ( posterior part of superior, middle and inferior frontal gyri ) BRODMANN AREAS: – 6 FUNCTION : - CONTROLS EXTRAPYRAMIDAL SYSTEM EFFECTS OF LESION :- MOTOR APRAXIA (inability to perform skilled movement that what once learned)

12. FRONTAL EYE FIELD

13. IV. MOTOR SPEECH AREA (BROCA’S AREA) LOCATION : - FRONTAL LOBE (inferior part of frontal gyrus) - i t is present on the left hemisphere in 98% of right handed population and 70% in left handers . BRODMANN AREAS: - 44, 45 FUNCTIONS:- CONTROL THE SPOKEN SPEECH EFFECTS OF LESION :- BROCA’S APHASIA [ Non- fluent, impaired repetition but good comprehension]

14. BROCA’S AREA

15. V. PREFONTAL CORTEX LOCATION :- FRONTAL LOBE (anterior large part of frontal lobe) BRODMANN AREAS : 9, 10, 11, 12 FUNCTIONS:- CONTROLS CONCENTRATION, EMOTIONS,ATTENTION AND JUDGEMENT. EFFECTS OF LESION :- (i) LOSS OF ORINENTATION (ii) FRONTAL LOBE SYNDROME

16. SENSORY AREAS CORTICAL AREAS LINKED WITH SENSORY FUNCTION. PRINCIPALLY THE THALAMUS RELAY A LARGE PART OF THE SENSORY SIGNALS TO THE SENSORY CORTEX FOR ANALYSIS. MAINLY INVOLVES IN – (i) SPATIAL RECOGNITION (ii)RECOGNITION OF INTENSITY OF SENSORY STIMULUS (iii) RECOGNITION OF SIMILARITY & DIFFERENCE OF SENSORY STIMULUS

17. I . SOMATOSENSORY AREAS LOCATION :- PARIETAL LOBE ( Posterior of central sulcus ) BRODMANN AREAS: - 1, 2, 3 FUNCTIONS:- (i) PERCEPTION OF EXTEROCEPTIVE IMPULSES LIKE – TOUCH , PAIN , TEMPERATURE. (ii) PROPRIOCEPTION EFFECTS OF LESION :- (i) POOR LOCALIZATION OF STIMULUS (ii) LOSS OR ABNORMAL OF DISCRIMINATIVE SENSATIONS. (iii) PROPRIOCEPTION IMPAIRMENT

18. SOMATOSENSORY AREAS 1 2 3

19. CORTICAL HOMUNCULUS PICTORIAL REPRESENTATION OF MOTOR & SENSORY CORTEX. SURFACE AREA OF THE CORTEX IS DEDICATTED TO A PARTICULAR BODY PART.

20. IN THE SENSORY CORTEX RECEIVED SENSATION FROM A PARTICULAR PART OF A BODY IS NOT PROPORTIONAL TO THE SIZE OF THAT PART OF THE BODY BUT RATHER TO INTRICACY OF SENSATORY INPUT RECEIVED FROM IT . THUS , THE THUMB, FINGER, LIPS AND TONGUE HAVE A DISPROPROTIONATELY LARGE REPRESENATION .

21. ASSOCIATION AREAS IN THESE REGIONS, DIRECT SENSORY OR MOTOR REPONSE ARE NOT ELICITED. FUNTIONS OVERLAP IN SAME REGION OF CORTEX. IT THE MOTOR FUNCTION IS PREDOMINANT IT IS KNOWN AS MOTOR SENSORY (MS) DOMINANT SENSORY FUNCTION AREA IS KNOWN AS SENSORIMOTOR AREA (SM)

22. I. SENSORY ASSOCIATION AREA LOCATION :- PARIETAL LOBE ( between sensory & visual areas ) BRODMANN AREAS: - 5, 7 FUNCTIONS :- mainly STEROGNOSIS EFFECTS OF LESION :- ASTEROGNOSIS

23. SENSORY ASSOCIATION AREAS

24. II. RECEPTIVE SPEECH ASSOCIATION AREA WERNIKE’S AREA LOCATION :- inferior part of PARIETAL LOBE BRODMANN AREAS : mainly 22 , also 38,42,21 FUNCTIONS:- SENSORY SPEECH EFFECTS OF LESION :- WERNIKE’S APHASIA [ fluent speech but poor comprehension]

25. WERNIKE’S AREA

26. AREAS OF SPECIAL SENSATIONS VISION I . VISUAL SENSORY AREA LOCATION :- OCCIPITAL LOBE BRODMANN AREAS : 17 FUNCTIONS :- RECEPTION AND PERCEPTION OF VISUAL IMPRESSIONS OF – COLOUR,SIZE, FORM, MOTION, ILLUMATION & TRANSPARENCY. EFFECTS OF LESION : - HOMONYMOUS HEMIANOPIA.

27. VISUAL SENSORY AREA

28. II. VISUAL PSYCHIC AREA LOCATION :- OCCIPITAL LOBE BRODMANN AREAS : - 18, 19 FUNCTIONS:- COMPLEX ASPECTS OF VISION- CORRELATION OF VISUAL IMPULSES WITH PAST MEMORY AND RECOGNITION OF OBJECT SEEN. EFFECTS OF LESION :- VISUAL AGNOSIA ( inability to recognize visually present object) Example:- PROSOPAGNOSIA (Face blindness)

29. VISUAL PSYCHIC AREA

30. HEARING I. AUDITORY SENSORY AREA LOCATION :- TEMPORAL LOBE BRODMANN AREAS :- 41, 42 FUNCTIONS : - RECEPTION AND PERCEPTION OF AUDITORY IMPRESSIONS OF – LOUDNESS , QUALITY & PITCH. EFFECTS OF LESION :- IMPAIRED HEARING (CORTICAL DEAFNESS) (usually the loss is greater in one ear then another)

31. AUDITORY SENSORY AREA

32. II . AUDITORY PSYCHIC AREA LOCATION :- TEMPORAL LOBE BRODMANN AREAS :- 22 FUNCTIONS :- CORRELATION OF AUDITORY IMPULSES WITH PAST MEMORY AND IDENTIFICATION OF SOUNDS HEARD. EFFECTS OF LESION :- AUDITORY AGNOSIA ( inability to recognize or differentiate between sounds even with intact hearing)

33. AUDITORY PSYCHIC AREA

34. REFRENCES:- GRAY’S ANATOMY , 38 TH EDITION RICHARD S. SNELL, CLINICAL NEUROANTOMY , 6 TH EDITION LESLIE P. GARTNER, TEXTBOOK OF NEUROANATOMY, 2 ND EDITION. INDERBIR SINGH, TEXTBOOK OF HUMAN NEUROANATOMY. BD CHAURASIA’S 4 TH VOLUME. VISHRAM SINGH, 3 RD VOLUME. PICTURE CREDITS:- KENHUB.COM