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Functional
Localization of the
Cerebral Cortex
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Auditory area
Angular
gyrus
Visual
area
Somatic sensoryVoluntary
motor
Motor speech,
grammar & phonology
Voluntary eye
movements
Brodmanns Classification System
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: Areas of the Cerebral CortexOverview
A. Sensoryareas.
B. Associationareas.
C. Motorareas.
D. Other corticalareas of functionalsignificance.
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Sensorimotor hierarchy
1ry sensory
area(Perception)
2ry sensory area(association area)
(Meaning of the
stimulus)Main Association
(Wernikesarea) &prefrontal cortex (PFC)
(Integration)
Premotor area
(area 6)
(Plan of movement)
1ry motor area(area 4)
(Execution of
movement)
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Right vs. Left Hemispheres
Lateralization:asymmetrical distribution of function; emerges during fetal life.
Ex: Hand preferences (handedness).
- > 90% of population is right handed; so, has left dominant hemisphere.
- Dominance become fixed only after the 1stdecade.
- Corpus callosumtransports information received in one hemisphere to
the other half.
General distribution of function:
Right hemisphere:
Non-verbal perceptual tasks, visual and spatial perception, e.g.,
recognition of faces, & musical and artistic tasks.
Left hemisphere:
Language, speech, writing & analytical functions.
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Right vs. Left Hemispheres
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1. Occipital lobe
2ry visual area(visual Association area)
(areas 18,19)
1ry visual area
(visual Sensory area)
(area 17)
Lateralview
Medial view
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Hemianopia
Effect of lesion of the Rt.visual cortex
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Area Site Funct io n Effect of lesion
1ry.visual area
(v isual s ensory
area)
(area 17)
On each side of
the calcarine
S.& extends
slightly laterally.
- Perception of pictures.
- Input from thalamus
(Lateral Geniculate
Body = L.G.B.).
- Project to the visualassociation area.
Homonymous
hemianopia.
2ry.visual area
(visual
associat ion
area)
(area 18,19)
Around area 17
& rest of the
occipital lobe.
- Understanding the
meaning & importance
of the pictures seen.
- Color & movementvision.
- Stereoscopic depths.
Inability to know
the meaning of
the pictures seen(word bl indness, =
visu al agnosia).
Functional Areas of the Occipi talLobe
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2. Temporal lobe
2ry auditory area(Auditory Association area)
(areas 22)
1ry auditory area(Auditory Sensory area)
(areas 41,42)
Lateral view
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Temporal lobe (cont.)
Facial recognition area
Medial view
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3. Parietal lobe
1ry somesthetic area(area 3,1,2)
Somesthetic
Association area(area 5,7)
Wernikes areaSensory speech
center(area 39,40)
Lateral view
39
40
5, 7
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Sensory
cortex
Sensory Leg arealies on the medial surface
(paracentral lobule)
MedialLateral
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Area Site Funct io n Effect of lesion
1ry.audito ry area
(audi tory sensory
area)
(area 41,42)
Middle of the sup.
temporal g.
(Heschls g.).
- Perception of sounds.
- Input from thalamus
(Medial Geniculate
Body =M.G.B.)
Incomp lete (s l ight)
bilateral deafness .
2ry.audi tory
area (audi tory
assoc iat ion area
(area 22)
The rest of the sup.
temporal g.
Understanding the
meaning & importanceof sounds.
Inability to know the
meaning of sounds(word d eafness, =
audito ry agn osia).
Facial
recogn it ion area
Parahippocampal g. Recognizing people by
faces.
Difficulty in recognizing
faces (prospagnosia).
Part of
Wernikesarea(sensory speech
center)
(area 39,40)
See parietal lobe
Functional Areas of the TemporalLobe
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1ry somesthetic area (area 3, 1, 2)
Representation:
The opposite half of body is
represented upside-down
(below for head & neck, then
U.L. and trunk).
Taste areal ies in the lowerend of the postcentra l g. &
insula.
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Area Site Func t ion Effect of lesion
Primarysomaethet ic
area
(area 3,1,2)
Postcentral g. +paracentral lobule
(sensory leg area)
- Proprioceptive sensations.- Cutaneous sensations.
- Vestibular sensation.
(from opposite of body)
Contralateralhemiansthesia.
(pain is slightly
affected)
Somethet ic
associat ionarea
(area 5,7)
Superior parietal
lobule.
- Understanding and
integrating various
sensory information.
- Center of Steriognosis.
- Difficulty in
understanding of the
meaning of various
sensory information
(= agnos ia).
- Aster iognosis.
Wernikes
area(sensoryspeech center)
(area 39,40)
- Inf. parietal lobule.
- Post. parts ofmiddle & inf.
temporal gyri.
(Only in the
dominant
hemisphere).
- Understanding of spoken
(auditory)& written
(visual) language.
- Integrationof different
senses that allows for
understanding a single
concept. Brocas area.
Receptive (sensory
aphasia).
Functional Areas of the Parietallobe
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1. Precentral area
2.
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4. Frontal lobe
Prefrontal Cortex(PFC)
1ry motor area(area 4)
Premotor area (area 6) &
supplementary motor areaFrontal eye field
Brocas areaMotor speech center
(area 44,45)
- Area 8- Part of area 6
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MedialLateral
Motor Leg area
lies on the medial surface
(paracentral lobule)
It is a map of body
movementsNot
muscles
Supplementarymotor cortex(area 6)
(area 4)
Motor Homunculus
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Representation:- The opposite half of body is
represented upside-down
(below for movements of head &
neck, then U.L. and trunk)
Movements of knees, legs, toes,anal & visc eral sphinc ters are in
theparacentral lob ule (= leg
area).
- The movement, NOTthe
muscles, are represented.- Highly skilled movements
occupy wider areas.
1. 1ry motor cortex (area 4)
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Area Site Funct io n Effect of lesion
1ry mo tor area(area 4)
Precentral g. +paracentral
lobule (leg area).
Initiate voluntary skillfulmovements (pyramidal tract),
except eye.
Contralateralhemiplegia
(excep t eye).
Premo tor area
(area 6)
In front of area 4. - Planning of movement
design area 4.
- Main extra-pyramidal
area for posture & muscletone.
- Increased muscle tone &
reflexes.
- Disturbed skillful movements.
- Reappearance of grasp reflex.
Supplementary
motor c or tex
Medial surface,
of area 6
Planning complex sequence
of movements & their
coordination in both hands.
Impaired selection of a particular
movement sequence.
Frontal eye
field
(area 8)
In front of area 6 Initiate voluntary eye
movementsto the oppositeside (conjugate lateral
movements).
- Inability to direct eye to
the opposite side.- Deviation of both eyes to
the affected side.
Brocasarea
(motor speech
center)
(area 44,45)
Triangular part of
inf. frontal g.
(dominant
hemisphere)
Speech production by
projection to area 4 (larynx,
tongue, lips (vocalization).
Expressive (motor aphasia)
Inability to express language.
Functional Areas of the FrontalLobe
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Anatomy of Speech
11
23
4
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Speech
Speech areas normally in the dominant hemisphere.
Wernikes area: sensory speech center.
Brocas area: Motor speech center.
Aphasia:absent or defective speech or language comprehension.
Wernikes aphasia:= (sensory, receptive aphasia) no comprehension & failureto convey meaning.
Brocas aphasia:= expressive or motor aphasia.
1- Words are seen in the visual cortex,or heard in the auditory cortex.2- Information concerning the word is interpreted in Wernikes area.
3- Information from Wernikes areais transferred to Brocas area.
4- Information is transferred from the Brocas areato the 1ry motor area
for vocalization.
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It is also called Frontal association area.
Prefrontal Cortex (pfc)
Reminder of the frontal lobe in the lateral surface.
Most of the medial frontal g.
Orbital part of theinferior surface.
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Function: HIGHER MENTAL FUNCTIONS- Intellectual functions, thinking, solving problems,judgment & foresight & framing of personality.
- Control of social behavior.
- Short-term memory.- Controls our emotions, mood & behavior.- Inhibitsimpulsive actions of the basal ganglia.- Control of autonomic (visceral) activities.
Lesion: (traumatic, tumors, lobectomy & ADD)
- short attention span & loss of recent memory.- becomes careless of his appearance (behavior).- mood changes (emotionally labile).- loss of social inhibition & impulsive responses.
Prefrontal Cortex (pfc)
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Other Cortical Areas
Area Site Funct io nTaste area - Lower end of the postcentral g.
- Insula.
Taste (gustatory sensation).
Vestib ular area - Postcentral g. Sensation of position &movements of the head in
space.
Insula In the floor of the lateral s. - Coordination of themovements for speech.
- Taste sensation.
Olfact ion - 1ry olfactory area (periamygdaloid
& prepiriform areas).
- 2ry olfactory area.
Smell sensation.
L imbic lobe
(cortical part of the
limbic system).
- Cingulate g.
- Isthmus of limbic lobe.
- Parahippocampal gyrus.
- Uncus.
- Short-term memory.
- Control of endocrine system.
- Reactions of fear, anger&
emotions associated with
sexual behaviors.
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Insula
Olfactory area
Taste area
Vestibular area
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1. Cingulate g.
2. Isthmus oflimbic lobe
3. Parahippocampal g.4. Uncus
Limbic lobe