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Functional cortical areas

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					                                                                      CORTEX

Functional cortical areas

-      parts of brain cortex defined by specific function
-      specific morphology (connections, cytoarchitectonics…)


PRIMARY CORTICAL AREAS

1.     general sensory and special sensory areas
-      get afferents from specific thalamic nuclei
-      respond to only one kind of stimulus
-      in these areas we realize what we see, hear, touch

2.     motoric area
-      that part of cortex involved in initiation and control of voluntary movements
       through the pyramidal tract – cortical beginning of pyramidal pathway


Map of cortical functions

Functional cortical areas – areas with specific functions

PRIMARY CORTICAL AREAS
-   they respond to specific stimuli
-   lesion results in characteristic neurological symptomatology

ASSOCIATION AREAS
-   all cortical areas other than primary ones
-   functionally superior to primary areas
-   their areas are larger than extent of primary areas, most of the neocortex is made of association areas
-      respond to more kinds of stimuli
-      get afferents from primary or other association areas
-      lesion results in more complex disorder (changes of behavior, emotions, memory), assessment of these less remarkable changes is more difficult
       (wrong term „clinically silent areas“)
-      secondary cortical areas possess characteristics of association areas

Functional map of the neocortex has not been completed as yet.

Investigation of cortical functions – modern imaging methods – PET positron emission tomography) – mapping of blood flow through brain cortex,
intensity of signal depends on functional involvement of separate cortical areas, somatotopic pattern

PRIMARY MOTOR CORTEX
-   Brodmann´s area 4, precentral gyrus (Penfield´s homunuculus), executes voluntary movement through the pyramidal pathway

MOTOR AREAS SUPERIOR TO PRIMARY MOTORIC CORTEX (ASSOCIATION AREAS)

-     premotoric area – area 6, outer surface of hemisphere, is „author“ of temporo-spatial plan of nexly learnt movements
-     supplementary motoric area (SMA) – area 6 , medial surface of hemisphere, activated before actual execution of learnt movements
PET activity is different for two former activities – learning versus execution of learnt movements

FRONTAL EYE FIELD (FEF)

area 8, prefrontal cortex, controls voluntary conjugated horizontal eye movements through fasciculus longitudinal medialis (FLM)


PRIMARY GENERAL SENSORIC AND SPECIAL SENSORIC CORTICAL AREAS

primary somatosensoric area
area 3, 1, 2 (postcentral gyrus, parietal lobe)
-       somatotopic pattern – Penfieldˇs homunculus „standing on the head“
-       realization of cutaneous epicritic and protopathic sensibility, proprioception
-       lesion results in contralateral hypesthesia or anesthesia
primary visual area
-      area 17 (around calcarine sulcus, occipital lobe)
-      retinotopic pattern (into the given hemisphere are projected ipsilateral halves of retina – contralateral halves of visual fields, above sulcus
       calcarinus – upper half of retina – lower half of visual field
-      realization of seen objects
-      bilateral lesion – cortical blindness, unilateral lesion – contralateral homonymous hemianopia

primary acoustic area
-      area 41 and sometimes 42 (Heschel´s gyri, temporal lobe)
-      tonotopic pattern
-      realization of heard sounds
-      bilateral lesion – cortical dumbness, unilateral lesion – serious contralateral disorder of hearing (not complete – bilateral connections with
       CGM)

gustatory cortical area
-      area 43 (parietal lobe)
-      realization of tasted informations
-      unilateral lesion – contralateral disorder of taste

olfactory cortical area
-       area 51, paleocortex, base of the hemisphere
-       realization of smelt informations
-       lesion – hyposmia, anosmia, irritation – olfactory hallucinations


Speech (phatic) functions

specific human activitie
functions connected with:
-       ability to speak
-       ability to understand a spoken speech
-      ability to repeat heard speech
-      reading
-      writing
-      in wider sense also counting


Speech centers

localization in the left hemisphere (normal dominance)

abilities – seat of large speech vocabulary but without syntactic function

1)     Broca´s center of spoken speech (anterior speech center), for programming of vocalization, area 44, 45 (inferior frontal gyrus)
2)     Wernicke´s center for understanding the spoken speech (posterior speech center), long discussions about its exact localization,
       Wernicke´s center in narrow sense: association acoustic cortex – posterior part of area 22 (superior temporal gyrus)
       Wernicke´s center in broader sense: besides area 22 also areas 39 and 40, parieto-occipital association cortex
both centres are interconnected – fasciculus arcuatus
connections with some other cortical area in both hemispheres

Cortical speech centers are not isolated nuclei – they are functional nodes of large neuronal nets (computer modelling but human brain is more
effective than any computer).


SECONDARY OR ASSOCIATION CORTICAL AREAS

-      each primary cortical area has its secondary area
-      secondary area is superior to corresponding primary area
-      larger extent, most of the neocortex

1.     general sensoric and special sensoric areas
-      react to 2 or more kinds of stimuli
-      get afferents from 2 or more areas (primary or association ones)
2.   motoric areas
-    are activated earlier than primary motoric cortex
-    not involved directly in execution of movements, they make temporo-spatial plan of movements
-    efferents to primary motoric cortex

				
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posted:7/8/2010
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