Cerebral Cortex

Front 1

Cerebral Cortex is

Back 1

the thin gray covering on both hemispheres
- 90% neocortex
- 10% allocortex

motor cortex thickest; 4.5mm while visula thinest @ 1.5mm

Front 2

Cerebral Cortex Blood Supply

Back 2

A, M, P cerebral aa.

Front 3

How many layers in the cerebral cortex?
- neocortex

Back 3

6
1. Molecular layer
2. External granular
3. External pyramidal (association & commissural fibres) & major source of corticocortical fibres
4. Internal granular. Reives thalamocortical fibres
5. Internal Pyramidal; corticobulbur, corticospinal and corticostriatal fibres. Contains giant pyramidal cells of Betz only @ motor cortex (BA 4)
6. Multiform layer. source of corticothalamic fibres

Front 4

Brodmanns Distinct areas

Back 4

47
17= primary visual cortex
- BASED ON ANATOMY

Front 5

Wilder Penfield

Back 5

Homunculus

Front 6

(1) Primary Cortical Areas (BA: 4)

Back 6

(Motor, Somatosensory, Visual, Auditory, Gustatory)
1o deal with "raw" information and specific thalamus areas
- usually topographically organised
-In essence, a primary area receives information from the thalamus and passes it on to other cortical areas for further processing.

Front 7

(2) SECONDARY CORTICAL AREAS (BA: 6)

Back 7

(Motor, Somatosensory, Visual, Auditory, Gustatory)
Each primary cortical area has a group of secondary areas that lie nearby. These secondary
areas receive inputs mainly from their primary area, but some receive directly from the
thalamus. Secondary cortical regions process the information from primary areas and add a
layer of complexity to the information, i.e. they offer a more detailed analysis of a sensation
or programme and plan a movement.

Front 8

(3) HIGHER-ORDER ASSOCIATION CORTICAL AREAS

Back 8

3 major regions of higher-order cortex: prefrontal, parietal, limbic
- receive information from multiple sensory cortical regions
- damage to cortices result in complex changes such as alterations in personality or the awareness of self.

Front 9

Central Sulcus

Back 9

- the frontal sulcus run anterior to posterir and there are 3 (superior, m, inferior)
- the first sulcus to run horizontially is the precentral sulcus

Front 10

1o Motor Cortex

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- The primary motor cortex (MI) encompasses the precentral gyrus and gives rise to most of the fibres in the corticospinal tracts (40%). It is involved in voluntary fine motor control.
- Stimulation of the medial aspect of the precentral gyrus will produce leg movements whereas stimulation of the most lateral aspect of M1 will result in face and tongue movements.
- destruction causes contralateral spastic paresis

Front 11

2o Motor Cortex

Back 11

The secondary motor cortex (MII) is not organized into movements. It receives information from association cortices and cerebellum and participates in movement planning. It has a dense projection to M1 and also sends projections directly to the spinal cord via the
corticospinal tract. Stimulation of M2 results in gross movements that require coordination among many muscles (turning head, trunk/limb movements).

Front 12

1o & 2o Motor Cortex

Back 12

Front 13

1o Visual Cortex

Back 13

BA 17
- encompasses the upper and lower banks of the calcarine sulcus and receives visual input from the lateral geniculate nucleus (LGN) of the thalamus.
- retinototopic organisation
- superior banks of calcarine sulcus is contralateral inferior field vision

Front 14

2o Visual Cortex (V2) (BA 18, 19)

Back 14

not organised retinotopically
- multiple regions v2-v5
-these regions add features such as motion, form and object recognition. Stimulation of secondary visual regions may cause complex visual changes such as the hallucination of formed images.

Front 15

V1 & V2

Back 15

Front 16

1o Auditory Cortex (BA 41)

Back 16

temporal lobe within the lateral sulcus on the transverse gyrus of Heschl's. It receives auditory information from the medial geniculate nucleus (MGN) of the thalamus.
- tonotopic organisation (differing in Fq of sound)
- Low frequency sounds are represented anterior and lateral, whereas high frequency sounds are represented posterior and medially.

Front 17

Secondary Auditory Cortex (BA 42)

Back 17

The secondary auditory cortex is located immediately posterior to A1 in a region known as the plenum temporale

Front 18

A1 & A2

Back 18

Front 19

Primary Gustatory Cortex (insula)

Back 19

located in the frontal operculum and the adjacent insula
cortex. These regions receive taste information via the ventroposterior medial (VPM) nucleus of the thalamus.

Front 20

Higher-Order Association Cortical Areas

Back 20

These primary and secondary regions then send projections to the higher-association cortical regions where various sensory modalities converge.

Front 21

Prefrontal Association Cortex

Back 21

L: The prefrontal association cortex encompasses a large region of the fontal lobe immediately anterior to the secondary motor regions.
A: social and cognitive processing and may be responsible for higher order functions such as personality and cognition
D: in the loss of ability to alter response when input changes – decision maker for appropriate movement. It may also result in:
• difficulty going for the big picture; attention only to details.
• They laugh or cry inappropriately
• trouble with working memory – temporary data storage
- deficits in concentration
- problem solving
- inappropriate social behaviour

Front 22

Phineas Gage

Back 22

Before the accident he was a most
capable and efficient foreman, one with a well-balanced mind, and who was looked on as a
shrewd smart business man. Following the prefrontal cortex damage he was said to be
"irreverent, grossly profane, showing little deference for his fellows". He was also impatient
and obstinate and unable to settle on any of the plans he devised for future action

Front 23

Parietal Association Cortex

Back 23

L: large region between the primary
somatosensory and secondary visual cortices and extends to include much of the temporal
lobe.
A: Given that this region lies in between most of the sensory cortical regions it is in a great position to receive multiple sensory modality information. As a result it is involved in complex multisensory perception including functions such as visuospatial localization, language, attention
D:
• finger agnosia (inability to recognize different fingers)
• agraphia (inability to write)
• alexia (inability to read)
• dyscalculia ( decreased ability to calculate or use numbers)
• left-right confusion
• disturbances in the awareness of body image

Front 24

Stimulation of Parietal Association cortex

Back 24

Front 25

Contralateral Neglect Syndrome

Back 25

- due to extensive parietal association damage
- not blind
- common in stroke
Patients bump into objects on contralateral side of lesion
May not groom contralateral body
May not eat food on side opposite to lesion
The patients receive sensory information from the contralateral side of the body but they simply neglect it.

Front 26

Limbic Association Cortex

Back 26

L: encompasses the cingulate gyrus and extends around the corpus callosum to include the parahippocampul gyrus.
A: Although it is most commonly associated with emotional state changes, it is involved in other functions such as motivation and attention.
D: changes in emotional processing. For example, cingulate cortex damage has been reported to result in a patient being able to “feel” and accurately localize painful stimuli but they pain does not bother them. That is, the negative emotion associated with pain is lost

Front 27

Cerebral BS

Back 27

- red= anterior cerebral aa.
- blue= post.

Front 28

SPEECH AND LANGUAGE REGIONS

Back 28

- mostly left side of brain in most people
- There is a special area of cortex that deals with formulation of speech (motor) and one that deals with understanding speech (sensory): a major tract - arcuate tract - connects the two and is important for normal speech production and comprehension.

Front 29

Speech Lesions

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- Cortical: speech formulation and/or comprehension
Subcortical (eg brainstem); may result in disturbance in speech articulation ([eg, whisper, explosive, strangled, slurring])

Front 30

Broca’s area (BA 44, 45)

Back 30

L: Posterior part of inferior frontal gyrus in dominant hemispherelies in the inferior frontal cortex in the regions known as the pars opercularis and pars triangularis. It lies immediately anterior to the region of M1 which
controls the muscle of the upper airway and so in some respects Broca's area acts as a premotor region.
D: "expressive aphasia" - a lack of ability to produce coherent language, including spoken, written and signed forms.
Patients suffering from Broca's aphasia can physically produce sounds and single words, but they cannot
produce sentences or express thoughts. They will often use a single word or a short string of
words and repeat them over and over; however they will not be able to grammatically express themselves. Similarly they can draw, but are not capable of writing coherent speech. They can understand speech, and often can form ideas to communicate, but they cannot put words together to communicate those ideas.
- Output can be restricted to noun-verb combinations, with short sentence length and speech is usually laboured and slow. Broca's patient when asked what his favourite food was, replied: "Uh...uh...uh...choc...like...chocolate".
+ normally assoc. with contralateral facial & arm weakness due to motor strip involvement

Front 31

Wernicke’s area (BA 22,39,40)

Back 31

L: Post part of superior temporal gyrus
lies at the posterior extent of the lateral sulcus in the parietal and superior temporal regions.
A: It is critical for language comprehension and damage to it results in "fluent aphasia" - the patient is unable to understand the content words while listening.
D: They are unable to produce meaningful sentences; their speech has grammatical structure but no meaning - word salad. They have a similar disorder in writing, and impaired understanding of oral speech and reading. They can speak fluently, but their strings of words often lack coherent meaning. Thus unlike
Broca's aphasia, Wernicke's damage does not result in difficulty with speech production, but with language production.

Front 32

Primary Somatosensory Cortex (BA,1,2,3)

Back 32

L: postcentral gyrus
A: receives direct sensory input from the body and head. It receives information from somatic sensations
such as touch, proprioception and pain from the contralateral face and body via the VPL and VPM thalamic nuclei. It is thought to be involved in the conscious perception of general sensation and in the accurate localization of these sensations.
- Somatotopic fashion
- Sensory homunculus based on greater nerves or 2 point discrimination can be detected
- destruction results in contralateral hemihypesthesia & astereognosis

Front 33

SII

Back 33

L: lies in the parietal operculum
A:has a gross somatotopic organization. It is thought that SII may be important in object recognition by touch and position sense

Front 34

Functional Areas;frontal lobe

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1. Motor cortex
2. frontal eye field (BA 8)
3. Broca's Speech area
4. Prefrontal cortex

Front 35

Frontal Eye Field

Back 35

BA 8
- destruction causes deviation of the eyes to ipisilateral side

Front 36

Cortex Overview

Back 36

Front 37

Functional Areas; Parietal Lobe

Back 37

1. Sensory Cortex
2. Superior parietal lobule
3. Inferior parietal lobule of dominant hemisphere
4. Inferior parietal lobule of non-dominant hemisphere

Front 38

Superior Parietal Lobule

Back 38

BA 5 & 7
- destruction= contralateral astereognosis & sensory neglect

Front 39

Inferior Parietal Lobule of Dominant Hemisphere

Back 39

- Gerstmann's Syndrome
a. right & left confusion
b. finger agnosia
c. dysgraphia & dyslexia
d. dyscalculia
e. contralateral hemianopia or lower quadrantanopia

Front 40

Inferior Parietal Lobule of nondominant Hemisphere

Back 40

destruction=
a. topographic memory loss
b. anosognosia
c. construction apraxia
d. dressing apraxia
e. contralateral sensory neglect
f. contralateral hemianopia or lower quadrantanopia

Front 41

Language Production

Back 41

Front 42

Functional Areas: Temporal Lobe

Back 42

1. 1o auditory cortex
2. Wernickes speech area (dominant hemisphere)
3. Meyer's loop
4. Olfactory bulb, tract & primary cortex
5. Hippocampal cortex
6. Anterior temporal lobe
7. Inferomedial occipitotemporal cortex

Front 43

Construction apraxia Testing

Back 43

Front 44

Meyer's Loop

Back 44

- consist of visual radiations that project to the inferior bank of calcarine sulcus. Interruption causes contralateral upper quadrantanopia (pie in the sky)

Front 45

Olfactory Bulb, tract & 1o cortex

Back 45

- ipsilateral anosmia
- irritative lesion causes olfactory hallucinations
a. olfactory groove meningiomas
b. Esthesioneuroblastomas; arise from bipolar sensory cells of olfactory mucousa, can extended past the cribiform plate into the anterior cranial fossa

Front 46

Hippocampal cortex

Back 46

- bilateral lesion causes inability to consolidate short term memory into long term memory

Front 47

Anterior Temporal Lobe

Back 47

- amygdala
- bilateral damage= Kluver Bucy syndrome

Front 48

Inferomedial Occipitotemporal cortex

Back 48

bilateral lesion= inability to recognise once-familiar faces (prosopagnosia)

Front 49

Functional Areas: Occipital Lobe

Back 49

bilateral lesions cause cortical blindness.
unilateral lesions cause contralateral hemianopia or quadrantanopia

Front 50

Focal Destructive Hemisphereic Lesions & Sx

Back 50

Front 51

Cerebral Dominance

Back 51

- determined by Wada Test
- Amytal is injected into ICA, if the patient becomes aphasic, the anestheic was adminstered to the dominant hemisphere

Front 52

Dominant Hemisphere

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responsible for (usually left)
- propositional language, speech & calculation

Front 53

Nondominant Hemisphere

Back 53

responsible for 3D or spatial perception & non-verbal ideation
- allows superior recognition of faces

Front 54

Split Brain Syndrome

Back 54

transection of corpus callosum
a. dominat better at vocal naming
b. non-dominat (or mute) better at pointing. A blindfolded person cannot name objects that are presented to the nondominat sensory cortex through touch
c. test (face test)
d. Patient with alexia in left visual field the verbal symbols seen in the right eye cant access the language centers of the left

Front 55

Other Corpus callosum Injuries

Back 55

- anterior corpus callosum lesion may result in akinetic mutism or tactile anomia
- post. cc lesion= alexia without agraphia
- callostomy has been used to treat "drop attack" (colloid Cyst of 3rd ventricel)