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Anatomy 2 Unit 3 > 8 - Cerebral Cortex > Flashcards

8 - Cerebral Cortex Flashcards

1
Q

A 63 year old male had a stroke while traveling

Deficits:

A

Left sided weakness
Stopped noticing things on his left
Not visual, he could see items on the left since he would not bump into furniture if it was on his left
More precisely, he did not consciously notice things on his left
E.g. If he had a pile of pens on the left side of his desk he would still ask for a pen if one wasn’t on the right side and he needed one

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2
Q

76 year old male has a stroke

A

Left side weakness/ paralysis, wheelchair bound, slurred speech
Refused to resign from work
Believed there was nothing wrong
Told people, “he merely stumbled and it wasn’t a stroke”
Claimed stories of him being paralyzed were false rumors and he invited naysayers to go hiking with him
Told them he was kicking 40 yard field goals with his left leg that very morning and some suggested that he try out for the local NFL team

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3
Q

Cerebral cortex

A 
Sheet of neurons 2 ft2 area; 2- 5 mm thick
Half the brain’s weight
25-50 billion neurons
100,000 km of axons
Receives 1014 synapses
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4
Q

Cerebral cortex most

A

highly developed in humans: roles in language, abstract thinking, adapt to environment, etc

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5
Q

Neocortex makes up most of

A

cortex, 6-layers; 95% of total cortex in humans

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6
Q

Paleocortex 3-layers:

A

uncus, olfaction

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7
Q

Archicortex 3-layers: most of

A

hippocampus

Allocortex or heterogenetic cortex

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8
Q

Pyramidal cells:
Pyramidal cells:
Apical dendrite:

A

one/ cell; extend to top layer of cortex

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9
Q

Pyramidal cells:

Basal dendrites:

A

sever/ cell; extend horizontally in respective layer

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10
Q

Pyramidal cells:

Axons have

A

recurrent branches, excite neighboring pyramidal cells

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11
Q

Most prevalent type of neuron:

A

Pyramidal cell

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12
Q

Cortical neuron structure - pyramidal cell

A

Apical (to top of cortex) & basal dendrites (horizontal)

Long axons to other cortical areas and subcortical sites

Excitatory (glutamate) synapses

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13
Q

pyramidal cell Principle

A

projection neurons of cortex

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14
Q

Pyramidal cell: Dendritic spines:

A

preferential site of excitatory synapses

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15
Q

Pyramidal cell: ;Suggested to be sites of

A

synapses that are selectively modified as a result of learning
Small changes in spine configuration lead to electrical properties and in turn synapse efficacy

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16
Q

Pyramidal cell: Some forms of intellectual disability may be associated with

A

poor spine development

Autism, Fragile X syndrome, etc

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17
Q

Cortical neuron structure: Nonpyramidal cell: All cortical neurons that are not

A

pyramidal cells

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18
Q

Cortical neuron structure: Nonpyramidal cell: Tend to have short axons that remain in the

A

cortex

diverse*

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19
Q

Cortical neuron structure: Nonpyramidal cell: Most make

A

inhibitory (GABA) synapses

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20
Q

Cortical neuron structure: Nonpyramidal cell: Principal

A

interneurons of cortex

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21
Q

Nonpyramidal cell types: Smooth stellate cells:

A

non-spiny dendrites, receive recurrent collateral branches from pyramidal cells, inhibitory (GABAergic synapses with pyramidal cells)
Silence weakly active cell columns in the cortex (similar to focusing action noted in cerebellar cortex by Golgi cells)

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22
Q

Nonpyramidal cell types: Bipolar cells: Located mainly in

A

outer layers, contain peptides co-released with GABA

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23
Q

Nonpyramidal cell types: Spiny stellate cells:

A

Spiny dendrites, generally excitatory, glutaminergic synapses with pyramidal cells
Receive most of the afferent input from thalamus, other cortical areas

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24
Q

Cortex has a laminar organization I

A

I. Molecular: ends of pyramidal cell apical dendrites distal ends of some thalamocortical (intralaminar nuclei) axons

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25
Q

Cortex has a laminar organization : II

A

II. Outer granular: small pyramidal and stellate cells

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26
Q

Cortex has a laminar organization: III

A

III. Outer pyramidal: medium-sized pyramidal and stellate cells

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27
Q

Cortex has a laminar organization: IV

A

IV. Inner granular: stellate cells receiving thalamocortical axons (relay nuclei)

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28
Q

Cortex has a laminar organization: V.

A

Inner pyramidal: large pyramidal cells to striatum & spinal cord

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29
Q

Cortex has a laminar organization: VI

A

VI. Fusiform: modified pyramidal cells projecting to thalamus

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30
Q

Afferents to cortex five sources: Association fibers (long and short): from

A

small & medium sized pyramidal cells in other parts of ipsilateral cortex

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31
Q

Afferents to cortex five sources: Commissural fibers: from

A

medium sized pyramidal cells via corpus callosum or anterior commissure from corresponding contralateral cortex

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32
Q

Afferents to cortex five sources: Thalamocortical fibers:

A

From relay or association nuclei

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33
Q

Afferents to cortex five sources: Non-specific thalamocortical fibers: From

A

intralaminar nuclei

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34
Q

Afferents to cortex five sources: Cholinergic & aminergic: from

A

basal forebrain, hypothalamus (tuberoinfundibulum), brainstem (midbrain raphe, LC)

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35
Q

Efferents from cortex

A

All efferents are pyramidal cell axons and all are excitatory
Short association
-e.g. sensory cortex  motor cortex

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36
Q

Efferents from cortex: Long association

A

e.g. prefrontal cortex  motor cortex

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37
Q

Efferents from cortex: Commissural fibers: from

A

contralateral cerebrum via corpus callosum and anterior commissure

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38
Q

Efferents from cortex: Fibers from

A

primary sensory and motor cortex make up largest input to basal ganglia

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39
Q

Efferents from cortex: Thalamus receives input from

A

all of the cortex

Corticopontine, corticospinal, corticobulbar

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40
Q

Commissures: Interconnect the

A

cerebral hemispheres

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41
Q

Corpus callosum

A

Predominant interconnection between hemispheres

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42
Q

Anterior commissure

A

Interconnects temporal lobes (inferior), anterior olfactory nuclei

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43
Q

Corpus callosum: All parts of the brain receive

A

commissural fibers except hand area of somatosensory & motor cortex and parts of primary visual cortex

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44
Q

Disconnection syndromes: Can result from

A

white matter damage

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45
Q

Alexia without agraphia

Can write but

A

unable to read
Cannot read words even they wrote
Also have right homonymous hemianopia
Rare, stokes are a frequent cause

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46
Q

Alexia without agraphia: Language areas on left isolated from

A

all visual input

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47
Q

Alexia without agraphia: Left visual cortex damaged by

A

stroke

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48
Q

Alexia without agraphia: Right visual cortex intact but

A

corpus callosum damaged

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49
Q

Alexia without agraphia: Language areas intact, so

A

speech is unaffected

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50
Q

Association bundles

A

Interconnect areas of one hemisphere
Short: U-fibers
Long: travel to different lobes

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51
Q

Association bundles

A

Longer fibers in distinct bundles

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52
Q

Areas that send off long axons have more

A

pyramidal cells

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53
Q

Primary sensory areas project to

A

nearby cortex, no need for long axons so fewer pyramidal cells

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54
Q

Granular and agranular cortex is

A

irregularly distributed

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55
Q

Brodmann characterized

A

44 areas, with imprecise boundaries

56
Q

Total cortical volume rather constant, but large variation in

A

Brodmann area sizes among individuals

57
Q

Types of cortical regions

A

Primary motor areas- areas that give rise to much of the corticospinal tract
Primary sensory areas- receive information from thalamic sensory relay nuclei
Association areas
Limbic areas

58
Q

Primary motor areas- areas that

A

give rise to much of the corticospinal tract

59
Q

Primary sensory areas- receive

A

information from thalamic sensory relay nuclei

60
Q

Sensory areas: Have a

A

topographical organization where the body surface, range of frequencies, visual world are mapped on cortical surface

61
Q

Sensory areas: Map is distorted so that highly sensitive areas (fingers, fovea) have disproportionately

A

large cortical representations

62
Q

Primary somatosensory cortex: postcentral gyrus (3, 1, 2)
Initial processing of

Parietal lobe

A

tactile and proprioceptive information

63
Q

Inferior parietal lobule of one hemisphere (typically left) involved with

A

language comprehension

64
Q

Rest of parietal cortex: complex aspects of

A

spatial orientation and directing attention

65
Q

Occipital lobe functions: Primary visual cortex (striate cortex; 17) in banks of

A

calcarine sulcus

66
Q

Occipital lobe functions: Visual association cortex, involved in

A

higher order visual processing
Bilateral injury to:
Inferior occipital lobe: color blindness
Occipital-temporal junction: motion blindness

67
Q

Occipital lobe: Line of Gennari: thin stripe of

A

myelin in primary visual cortex, aka striate cortex

68
Q

Striate cortex parallels calcarine sulcus and extends a bit onto

A

posterior surface

69
Q

Visual fields: Fibers from nasal half of retina cross to

A

contralateral optic tract

70
Q

Visual fields: Fibers from temporal half of retina enter

A

ipsilateral optic tract

71
Q

LGN: Structure

A

6-layered, precise retinotopic arrangement
Pattern in the same in each layer so any given point in the visual field is represented as a column in all 6 layers
Each layer gets input from one eye
1, 4 & 6 contralateral eye
2, 3 &5 ipsilateral eye

72
Q

Parvocellular layers

A

3- 6 (color & form)

73
Q

Magnocellular layers

A

1- 2 (movement & contrast)

74
Q

Fibers representing inferior visual fields most superior in

A

radiations

75
Q

Those representing superior visual fields, most inferior in

A

radiations

76
Q

Optic radiations end retinotopically in

A

occipital cortex, above and below the calcarine sulcus (area 17)

Inferior visual fields above calcarine sulcus
Superior visual fields below calcarine sulcus

77
Q

Macula is represented most

A

posteriorly, peripheral fields more anteriorly

78
Q

Primary visual cortex

Breaks visual information down into

A

component parts: orientation, color, depth, motion, brightness, etc

79
Q

Distributes this info to

A

specialized parts of extrastriate cortex

Example of simultaneous, parallel processing
Common in nervous system accounts for speed we can assess a visual field even thou our neurons are slow

80
Q

Cortex also has a columnar organization: Neurons are functionally arranged in columns that extend

A

radially thru all 6 horizontal layers

81
Q

Cortex also has a columnar organization: All of the neurons in each column (several hundred) are sensitive to one

A

modality, i.e. modality-specific

82
Q

Cortex also has a columnar organization: One column may respond to movement of a

A

particular joint, another a patch of skin, the orientation of an object in the visual field

83
Q

Cortex also has a columnar organization: Striate (primary visual) cortex has an array of

A

repeated, modular collections of neurons arranged in columns

84
Q

Columns in one cortical module analyze

A

all aspects of visual information arriving from discrete areas of visual field

85
Q

Modules in foveal part analyze

A

small areas of visual field, so fova has many more modules and therefore better resolution

86
Q 
Process starts in LGN
Parvocellular layers (color, form)-
A

ventral striate cortex

Ventral stream

87
Q

Magnocellular layers (location, movement)-

A

dorsal striate cortex

Dorsal stream

88
Q

Selective damage to extrastriate cortex can lead to

A

strange visual deficits: selective deficit in distinguishing colors, motion, faces

89
Q

Primary auditory cortex (41, 42): transverse temporal gyri superior surface of

Temporal lobe functions

A

superior temporal gyrus

90
Q

Temporal lobe functions

A

Auditory association cortex

91
Q

Temporal lobe functions: Language comprehension,

A

Wernicke’s area- posterior aspect of one hemisphere (usually left)

92
Q

Temporal lobe functions: Higher order

A

visual processing

93
Q

Gustatory:

A

frontal lobe (operculum) & insula

94
Q

Vestibular:

A

superior temporal gyrus and posterior insula

95
Q

Primary olfactory cortex is

A

paleocortical, not neocortical

96
Q

Olfactory Cortex consists of

A

Cortex near lateral olfactory tract, a.k.a. piriform cortex

Cortex covering amygdala, periamygdaloid cortex

Small part of parahippocampal gyrus

97
Q

Frontal lobe: Broca’s area:

A

inferior frontal gyrus of one hemisphere (usually left), production of spoken and written language

98
Q

Frontal lobe: Prefrontal cortex: rest of

A

frontal lobe, executive functions (personality, foresight, insight)

99
Q

Primary motor cortex in

A

precentral gyrus, premotor & supplemental motor areas: part of precentral, nearby portions of superior and middle frontal gyri
Origin of descending corticospinal tract, initiate voluntary movements

100
Q

Association areas

A

Mediate higher mental functions
Language, art, music, etc
Very little is known about these functions and most of our knowledge stems from case reports of patients with naturally occurring lesions
Advent of functional imaging scans are advancing our understanding

101
Q

Association Areas: two types: Unimodal association cortex-

A

adjacent to primary area
Devoted to elaborating on business of primary area
Example: 18, 19 around 17 in occipital lobe

102
Q

Association areas: two types: Multimodal association cortex-

A

high level intellectual functions

Inferior parietal lobule, much of frontal and temporal lobes

103
Q

Dominant hemisphere: Hemisphere that

A

produces and comprehends language

104
Q

Left hemisphere is

A

dominant hemisphere in most people, even those who are left handed

105
Q

Nonfluent aphasia

A

Make few written or spoken words, get by with phrases (“OK”, “And how”)
Very difficult to produce words
All detail & meaning in sentences is lost
Can comprehend language
Often due to damage in Broca’s area
Broca’s aphasia

106
Q

Fluent aphasia: Can write and speak, but words used and

A

sequences of words used in sentences is incorrect

Really little or no linguistic content
Substitute one letter or word for another (paraphasia)
Make up new words (neologisms)
Difficulty in language comprehension
Often due to damage in Wernicke’s area
Wernicke’s aphasia
107
Q

Damage Broca’s

A

Deprive motor areas of ability to generate language
Muscle function normally for other activities
Comprehension of language unaffected

108
Q

Damage Wernicke’s

A

Broca’s area is unchecked

Words are generated but no meaning

109
Q

Cortical language areas near

A

lateral sulcus

110
Q

Left lateral sulcus extends further posteriorly than the

A

right as planum temporale is larger on the left

111
Q

Planum temporale: part of

A

superior temporal gyrus posterior to primary auditory cortex (transverse temporal gyri)

112
Q

Language areas border (left) lateral sulcus: Stimulate motor cortex near mouth produce

A

involuntary grunts, vocalization

113
Q

Language areas border (left) lateral sulcus: Stimulate other areas on

A

dominant side:
Subject ceases to speak, but can still move mouth
Yet other areas subject makes linguistic errors, fails “to find” appropriate words

114
Q

Perisylvian language areas: Broca’s area in

A

inferior frontal gyrus (opercular and triangular parts)

115
Q

Perisylvian language areas: Wernicke’s area in

A

posterior part of superior temporal gyrus, continuing into planum temporale and inferior parietal lobule

116
Q

Aphasia: Inability to use

A

language, lose the use of or access to symbols humans use as concepts, i.e. words

117
Q

Aphasia: Broca’s and Wernicke’s areas provide

A

framework for two broad types of aphasia classified depending on how easily words are produced:
Nonfluent
Fluent

118
Q

Language in the right hemisphere: Language more than selecting

A

correct word and using grammatical rules to put it in the correct part of a sentence

119
Q

Language in the right hemisphere: Language has

A

emotional content and some linguistic elements are conveyed rhythmically

120
Q

Language in the right hemisphere: So-called musical aspects of speech called

A

prosody; produced in right hemisphere

121
Q

Language in the right hemisphere: Right inferior frontal gyrus produces

A

prosody

122
Q

Language in the right hemisphere: Motor aprosody: can’t convey

A

authority, anger, etc. in speech

123
Q

Right posterior temporoparietal region comprehends

A

prosody

124
Q

Sensory aprosody difficulty comprehending

A

the emotional content of speech from others

125
Q

Parietal cortex: Association areas posterior to

A

primary somatosensory cortex

126
Q

Parietal cortex: Unimodal areas:

A

Visual association cortex, auditory association areas, somatosensory

127
Q

Parietal cortex: Damage to these areas can cause

A

sensory specific agnosias

128
Q

Parietal cortex: Inability to recognize

A

faces, perceive movement (visual agnosias)

129
Q

Parietal cortex

A

Multimodal areas:
Centered on intraparietal sulcus
Monitor relationships of body with outside world

130
Q

Right parietal lobe damage

A

Patient has trouble with left half of body
May deny something is wrong with (left) limb and can be convinced the (left) limb is someone else’s
Ignore left half of body, called contralateral neglect

131
Q

Left parietal lobe damage

A

Important for taking sensory information needed to plan a movement accurately
Apraxias (“lack of action”)
Patients unable to perform some actions, many different types
Ask patient to imitate examiner who touches finger to face and they can’t do it,
But they can scratch an itch on their face

132
Q

Prefrontal cortex

A

Frontal lobe anterior to primary motor (4) and supplemental motor (6) cortices

133
Q

Prefrontal cortex: Controls activities of

A

other cortical areas; underlies executive functions

Interconnected with dorsomedial nucleus of thalamus

134
Q

Prefrontal cortex: two broad types: Dorsolateral, over

A

lateral convexity
Interconnected with parietal association areas
Important role in working memory “keep in mind”, problems planning, solving problems, maintaining attention

135
Q

Prefrontal cortex: two broad types: Ventromedial, extends to

A

orbitofrontal and anterior cingulate areas

Damage makes people impulsive, can’t suppress inappropriate responses/ emotions

Anatomy 2 Unit 3 (14 decks)

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