Higher Cortical Functions.pptx

Higher Cortical Functions

1. Higher Cortical Functions Dr. RUTAYISIRE François Xavier PGY2 Basic Neurosciences module University of Rwanda Supervisor: Dr. MUNYEMANA Paulin

2. Higher Cortical Functions

3. The higher cortical functions { COGNITIVE FUNCTIONS} include language, vision, recognizing objects in space (visuospatial recognition), and awareness… The admittedly vague descriptor for the brain regions that carry out these functions is the association cortex ( or cortices )

4. Association cortex Lateral and medial views of the human brain show the association cortices in blue. The primary sensory and motor regions of the neocortex are shown in yellow. Notice that the primary cortices occupy a relatively small fraction of the total area of the cortical mantle. The remainder of the neocortex—defined by exclusion as the association cortices—is the seat of human cognitive ability.

5. Neocortex Most of the cortex that covers the cerebral hemispheres is neocortex , defined as cortex that has six cellular layers, or laminae . Each layer comprises more or less distinctive populations of cells based on their different densities, sizes, shapes, inputs, and outputs.

6. Based on variations in the thickness, cell density, and other histological features of the six neocortical laminae, the human brain can be divided into some 50 cytoarchitectonic areas, typically those recognized by the neuroanatomist Korbinian Brodmann in his seminal 1909 monograph

7. 4 Cortical motor areas Primary motor area Premotor area Motor eye field area Broca’s area For each cortical area, let’s consider the: Site Arterial supply Function Effect of a lesion

8. Primary motor area Site: Precentral Gyrus & anterior part of paracentral gyrus Arterial supply: upper 1/4 th and PCL= ACA Lower 3/4 th = MCA Representation: Opposite half of the body is upside down Lower third: Head region Leg and foot: Paracentral lobule Function: Origin to corticospinal and corticobulbar tracts Initiation of fine of the highly skilled fine movements Lesion: Contralateral hemiplegia with five known signs of UMNLs

9. Premotor area Site: Anterior to area 4 Arterial supply: upper 1/4 th = ACA Lower 3/4 th = MCA Function: Stereotyped movements of muscles through connection with basal ganglia. Planning and execution of learned motor activity by storing the programs of motor activity learned by experience such as walking or dancing Lesion: Apraxia: difficult performing learned motor activity without paralysis

10. Motor eye field area Site: Posterior part of middle frontal gyrus Arterial supply: MCA Function: Horizontal movement of the 2 eyes to the opposite sides Lesion: Ipsilateral deviation of the 2 eyes due to unopposed action of intact area 8

11. Broca’s area #44, 45 Site: Dominant hemisphere , In the posterior part of IFG Opercular gyrus: area 44 Triangular gyrus: area 45 Arterial supply: MCA Function: Coordinates the muscles used for speech (Lips, tongue and larynx) for speech production Lesion : Lesion in Broca's area will cause Motor aphasia ; Patients can not form words and is unable to express himself. Th patient can understand and point at object Lesion in the nondominant hemisphere, has no effect

12. Prefrontal cortex: Area 9, 10, 11, 12 Personality center Site: Frontal pole Arterial supply: ACA, MCA Function: Make up of the person’s personality Regulations the depth of the person’s feelings and emotional behaviors Higher intellectual function such as production of ideas and judgment. Lesion: Loss of personality and patient has no appreciation to any social behavior.

13. SENSORY areas General sensory area (3, 1, 2) Sensory association area (5, 7, 40) Primary auditory area (41, 42) Auditory association area (22) Primary visual area (17) Visual association area (18, 19) Others: Taste, Olfactory , vestibular

14. General sensory area(3,2,1) Site: Postcentral gyrus & posterior part of paracentral lobule Arterial supply: Upper 1/4 & PCL: ACA Lower 3/4: MCA Representation: similar to area 4 Opposite half of the body is upside down Lower third head region Leg and foot paracentral lobule Function: Receives general sensations from the opposite side of the body & face. Lesion: Contralateral hemianesthesia

15. Somatic sensory association area(5,7,40) Site: Superior parietal lobule: # 5 & 7 Supramarginal gyrus: # 40 Arterial supply: ACA & MCA Function: Stereognosis, Interpretation of senses perceived in the general sensory area Lesion: Astereognosis: inability to recognize objects by the sense of touch with the eyes closed. Unliteral neglect: lesion in area 40 with inability to recognize left from right 4 5&7

16. Primary auditory area 41,42 Site: Middle of the upper surface of the superior temporal gyrus Arterial supply: MCA Function: Hearing from the 2 ears. mainly from the opposite ear Lesion: Bilateral diminution of hearing mainly on the opposite side. Auditory Association Area: Wernicke's Area #22 Site: posterior part of the superior temporal gyrus Arterial supply: MCA Function: recognition of sounds Lesion: auditory agnosia & sensory aphasia, Inability to understand the spoken languages.

17. Primary visual area( Area 17) Site: Above and below the calcarine sulcus Arterial supply: PCA Function: receives optic radiations from LGB for perception of light Representation of the retina: Temporal fibers of the same eye and nasal fibers of the opposite eye Macula: posterior 1/3 rd of the calcarine sulcus Upper retinal fibers: Above calcarine sulcus(Cuneus) Lower retinal fibers: Below calcarine sulcus(Lingual Gyrus) Lesion: Contralateral homonymous hemianopsia with macular sparing.

18. Visual association area(18,19,39) Site: Area 18 and 19: Above and below area 17 Area 39: Angular gyrus Arterial supply: Area 18 and 19: PCA Area 39: MCA Function: Recognition of what we see Color vision: Inferior association area Angular gyrus: Comprehension of written languages Lesion: Visual agnosia: Inability to recognize what we see Loss of color vision: Inferior association area Alexia and agraphia: lesion in angular gyrus

19. Primary olfactory area(Area 34) Site: Uncus Irritative lesion will cause olfactory hallucinations Olfactory association area(Area 28) Site: Anterior part of hippocampal gyrus Function: discrimination of odors Face recognition area(Area 37) Site: posterior part of fusiform gyrus Function: similar to area 19 and 39 Face and body recognition Words recognition Numbers recognition Lesion: Prosopagnosia(Face blindness) Inability to recognize familiar faces They can rely on sounds

20. Language areas We have 4 language areas 1 Motor speech area ( Broca's area 44 and 45) Lesion: Expressive(Motor) aphasia 3 Sensory speech area (22,39,40) Wernicke's area 22: understand the spoken languages Lesion: sensory aphasia( Inability to understand the spoken /written languages) Angular gyrus: Area 39; understand the written languages Lesion: Agraphia, alexia Supramarginal gyrus( area 40): Understand shape, size & texture and recognition of the body parts and left side from the right side.

21. Processing of written languages E.g : Reading from a book

22. Processing of spoken language Answering a question like: What is your name?

23. MMSE

24. References Dale Purves book of neuroscience 6 th edition K.S. Saladin anatomy & physiology: the unity of form and function, 9 th edition JAHANGIR MOINI FUNCTIONAL AND CLINICAL NEUROANATOMY A Guide for Health Care Professionals Dejong’s T he neurologic examination 7th e d i t i o n