N: Cerebral Cortex Flashcards
The cerebral cortex is a sheet of ___ matter
gray
Cerebral cortex is a sheet of ___
neurons
What is the area of the cerebral cortex?
2 feet squared = area
How thick is the cerebral cortex?
2-5mm thick
How many neurons are found in the cerebral cortex?
25-50 billion neurons
How many km of axons are found in the cerebral cortex?
100,000 km of axons
The cerebral cortex receives ___ synapses
10^14
The cerebral cortex is highly developed in ___
humans
What are 3 distinct roles that the cerebral cortex plays in humasn?
language
abstract thinking
adapting to environment
The cerebral cortex can be broken down into 2 subcategories. What are they?
- neocortex
2. allocortex
Neocortex aka ___ aka ___
neocortex = isocortex = homogenetic cortex
Why is neocortex (isocortex / homogenetic cortex) called “neo” cortex?
it developed later in evolution
Neocortex makes up ___ % of cortex
95
How many layers is the neocortex?
6
In the neocortex, where are layers I and VI relative to the leptomeninges and white matter?
layer 1 is just beneath the leptomeninges
layer 6 is just on top of white matter
Allocortex aka ___
homogenetic cortex
Allocortex (homogenetic) makes up ___% of cortex
5
What are the 2 types of allocortex?
- paleocortex
2. archicortex
Paleocortex is ___ layers.
It overlies the ___
It plays a large role in ____
3 layers
overlies uncus
plays large role in olfaction
Archicortex is __ layers
It overlies the ___
3 layers
overlies most of the hippocampus
What are the 2 main types of neocortical neurons?
- pyramidal cells
2. non-pyramidal cells
Which neocortical neuron is most prevalent type in humans?
pyramidal cells
Describe the apical dendrites of pyramidal cells
1 apical dendrite per cell
extend to the top layer of the cortex (layer I)
talks to other neurons along way to layer I
Describe the basal dendrites of pyramidal cells
several basal dendrites per cell
extend horizontally in respective layers (may go up or down 1 layer, but projects out laterally)
Describe the axons of pyramidal cells
Axons have recurrent branches to excite neighboring pyramidal cells
These axons extend from the base of the cell
Long axons of pyramidal cells go towards ___
other cortical areas and subcortical areas
Pyramidal cells are ___ synapses
excitatory (glutamatic) synapses
Describe the dendritic spines of pyramidal cells
preferential site for excitatory synapse
suggested to be site of synapse that are selectively modified as a result of learning
small changes in spine configuration lead to electrical properties leads to SYNAPSE EFFICACY
Some forms of intellectual disability may be associated with ______ (of pyramidal cells)
What are 2 examples of intellectual disabilities associated with this?
poor spine development of dendritic spines (selectively modified for learning)
examples: autism , fragile X syndrome
All cortical neurons that are not pyramidal cells are ___
non-pyramidal cells
Describe the axons and dendrites of non-pyramidal cells
Short and remain in cortical area
Most non-pyramidal cells are ___ synapse
inhibitory (gaba) synapse
The principle interneurons of the cortex are ___
non-pyramidal cells
Is there only 1 type of non-pyramidal cell?
no.
they are diverse in nature (spiny stellate cell, smooth stellate cell, bipolar cell, basket cell, candle cell)
Spiny stellate cells are a type of ____ with spiny dendrites.
These are generally ____ synapse with ____.
receive most afferent input from ____
type of non-pyramidal cell with spiny dendrites
generally excitatory (glutaminergic) synapse w/ pyramidal cell
receive most afferent input from thalamus or other cortical areas
____ are the preferential site for excitatory synapses
dendritic spines
If most non-pyramidal cells are inhibitory (gaba) synapses, why are spiny stellate cells excitatory (glutamanergic)?
DENDRITIC SPINES ARE THE PREFERENTIAL SITE FOR EXCITATORY SYNAPSES
so SPINY stellate cells (non-pyramidal) = excitatory (glutaminergic)
Smooth stellate cells are a type of ____ with non-spiny dendrites.
receives _____ from pyramidal cells
silences weakly active ___ in cortex
type of non-pyramidal cells with non-spiny dendrites
receives recurrent collateral branches from pyramidal cells
silences weakly active cell columns in cortex
Bipolar cells are a type of ____
located mainly in ____
bipolar cells - type of non-pyramidal cell
located mainly in outer layers
Bipolar cells are inhibitory in nature (because non-pyramidal).
They release gaba (inhibitory) w/ co-released ___
peptides
“The cortex = laminar organization”
What does this mean?
Neocortex - 6 layers horizontally
but with vertical function
Cortical layer I: aka ______
What is found here?
molecular layer
ends of pyramidal cell apical dendrites
distal end of thalamocortical (intralaminar nuclei) axons
Cortical layer II: aka ____
What is found here?
outer granular layer
small pyramidal and stellate cells
Cortical layer III: aka ____
What is found here?
Outer pyramidal layer
medium sized pyramidal and stellate cells
Cortical layer IV: aka ___
What is found here?
inner granular layer
stellate cells receiving thalamocortical axons (relay nuclei)
Cortical layer V: aka ___
What is found here?
Inner pyramidal layer
large pyramidal cells to striatum and spinal cord
Cortical layer VI: aka ____
What is found here?
Fusiform layer
Modified pyramidal cells projecting to thalamus
Describe the differences between layer V of the pre-central cortex and the post-central cortex
layer V - inner pyramidal layer. this is where large pyramidal cells to striatum and spinal cord are found.
Post-central (sensory) does not need large pyramidal cells. Therefore layer V is small.
Pre-central (motor) needs large pyramidal cells so that their long axons reach the muscular output. Therefore layer V is thick.
What are the 5 sources of afferents to the cortex?
- association fibers (long and short)
- commissural fibers
- thalamocortical fibers
- non-specific thalamocortical fibers
- cholinergic and aminergic fibers
Association fiber afferents come from ____
Are they long or short?
small and medium sized pyramidal cells
from other parts of IPSILATERAL cortex
short association fibers = from pre-central to post-central
long association fibers = from frontal lobe to occipita llobe
Commissural fiber afferents are from ____
From medium sized pyramidal cells via corpus callosum or anterior commisure
from corresponding CONTRALATERAL cortex
Thalamocortical fiber afferents are from ___
From relay nuclei or association nuclei
Non-specific thalamocortical fiber afferents are from ___
from intralaminar nuclei
Cholinergic and aminergic fibers are from ____
These afferent fibers regulate ____
basal forebrain, hypothalamus (tuberoinfundibulum), brainstem (midbrain, raphe, LC)
regulate attention and arousal
All efferents from the cortex are ___ cells and ___ synapses
pyramidal cells
all excitatory (glutaminergic) synapses
What are the 2 fiber types of efferents from cortex?
association fibers
commisural fibers
Efferent fibers from primary sensory cortex and primary motor cortex make up the larges part of the ___
basal ganglia
The ___ receives input from all of the cortex
thalamus
What are the main 3 efferent pathways from the cortex?
corticopontine
corticospinal
corticobulbar
A ___ interconnects the cerebral hemispherse
commisure
What is the predominant interconnection between the 2 hemispheres?
corpus callosum
All parts of the brain receive commissural fibers from corpus callosum except for ____
hand area of somatosensiry and motor cortex
and parts of primary visual cortex
The anterior commissure interconnects ______
anterior commissure interconnects the temporal lobes inferiorly
interconnects anterior olfactory nuclei
Disconnection syndromes as a result of white matter damage are rare. They are frequently caused by ____
strokes
Alexia without agraphia - disconnection syndrome via white matter damage
What are hte symptoms?
alexia = can't read agraphia = can't write
alexia w/o agraphia = can’t read but can write
can’t read things even they wrote
also experience RIGHT HOMONYMOUS HEMIANOPIA
Association bundles interconnect ____
Different areas of the same hemisphere (different IPSILATERAL cortical areas)
Describe the difference between short and long association bundles
Short = u-shaped to adjacent gyri
Long = travel to different lobes
The longest association bundles are distinct (5). Name them.
- superior longitudinal (arcuate) fasciculus
- superior occipitofrontal fascicuclus
- inferior occipitofrontal fasciculus
- cingulu
- uncinate fasciculus
The superior longitudinal (arcuate) fasciculus is a long association bundle that connects ____
frontal, occipital, parietal, temporal lobes
Superior and inferior occipitofrontal fasciculi are 2 long association bundles that connect ___
occipital and frontal lobes
Cingulum is a long association bundle that connects ____
frontal and parietal lobes to parahippocampus gyrus and adjacent temporal gyri
Uncinate fasciculus is a long association bundle that connects ____
frontal lobe to tempora lobe
Describe the difference between granular area and agranular areas of cortex
Granular area - THIN, in somatosensory (post central) gyrus
Agranular area - THICK, in motor (pre central) gyrus
Areas that send off long axons have more ___
pyramidal cells
Phineas gage = injury to frontal lobe which caused major ____ changes
personality
Primary motor cortex areas give rise to the ____ tract
corticospinal tract
Primary sensory cortex areas receive info from ____
thalamic sensory relay nuclei
Describe the topography of cortical sensory areas
topographical organization where body surface, range of frequencies, visual world are mapped on cortical surface
this map is distorted so that highly sensitive areas (fingers, fovea) have disproportionately large cortical representation
Primary somatosensory cortex aka post-central gyrus on the PARIETAL LOBE is site for _____
initial processing of tactile and proprioceptive info
Inferior parietal lobule is found on _______
1 hemisphere of PARIETAL LOBE
usually the left hemisphere
there is also a superior parietal lobule which is separated via intraparietal sulcus
Most of the parietal lobe cortex is involved in what function?
spatial orientation and directing attention
Primary visual cortex (striate cortex) is found ____
in the banks of the calcarine sulcus in OCCIPITAL LOBE
Visual association cortex of occipital lobe is involved in ____
higher order visual processing
bilateral injury of inferior occipital lobe leads to ____
bilateral injury of occipital-temporal junction leads to ___
inferior occipital lobe –> color blindness
occipital-temporal junction –> motion bindness
What is the line of gennari? Where is it?
Aka striate cortex
Thin strip of myelin in primary visual cortex
parallels calcarine sulcus and extends a little onto the posterior surface
Describe the visual field:
Fibers from nasal retina vs. temporal retina project to which optic tract?
This is so each ____ “sees” the contralateral visual field
nasal retina fibers –> contralateral optic tract
temporal retina fibers –> ipsilateral optic tract
this is so each optic tract sees the contralateral visual field
We need to be able to examine comparable areas of both retinas in order to obtain ____
This is accomplished by the ____
In order to obtain DEPTH PERCEPTION
this is accomplished by OPTIC CHIASM
Describe the pattern of the lateral geniculate nucleus
6 layered precise retinotopic arrangement
pattern is the same in each layer so any given point of visual field is represented as a column in all 6 layers
In the LGN of the occipital lobe, which layers are contralateral and which are ipsilateral?
layers 1, 4, 6 = contralateral eye
layers 2, 3, 5 = ipsiltaeral eye
In the LGN of the occipital lobe, define the parvocellular vs magnocellular layers.
Parvocellular layers = color and form (layers 3-6)
Magnocellular layers = movement and contrast (layers 1-2)
The LGN projects to ____
How are inferior/superior visual fields perceived once there? Relative to what?
How is the macula vs peripheral field represented?
LGN projects to primary visual cortex
optic radiations end retinotopically in occipital cortex above/below calcarine sulcus
inferior visual field = superior radiations = above calcarine sulcus
superior visual field = inferior radiations = below calcarine sulcus
macula = most POSTERIORLY
peripheral vision = most ANTERIORLY
The primary visual cortex breaks down visual info into components such as ___
orientation, color, depth, motion, brightness
Once the primary visual cortex breaks down visual info into components, it distributes this info to ____
extrastriate cortex
this is an example of SIMULTANEOUS, PARALLEL PROCESSING
“cortex = columnar organization”
describe this
Neurons functionally are arranged in columns that extend radially through all 6 horizontal layers
All neurons in each column are sensitive to _____
This is called ____
1 modality
called modality-specific
example: all neurons in 1 column respond to the movement of 1 specific joint
Describe the cortical modules in the foveal part of cortex
Modules here analyze small areas of visual field, so fovea has many more modules than other visual cortex
therefore it has better resolution
The process of dorsal/ventral streams starts in the ___
LGN
Which layers of the LGN go to ventral stream? Which go to dorsal stream?
What is the path there?
LGN –>
Parvocellular layers (3-6; color/form) –> ventral striate cortex –> ventral stream
Magnocellular layers (1-2; movement/location) –> dorsal striate cortex –> dorsal stream
Selective damage to extrastriate cortex can lead to _____
strange visual deficits (selective deficit in distinguishing colors, motion, faces)
Primary auditory cortex of temporal lobe is found where?
transverse temporal gyri superior surface of superior temporal gyri
Where is wernicke’s area located?
What is it’s function?
located on posterior aspect of 1 hemisphere of temporal lobe (usually left hemisphere)
this is for LANGUAGE COMPREHENSION
Ventral stream is located on which lobe?
What is this function?
located on ventral surface of temporal lobe
function: higher order visual processing
Where is Broca’s area located?
What is it’s function?
located on inferior frontal gyrus of 1 hemisphere (usually left)
production of spoken and written language
Besides broca’s area, the rest of the frontal lobe is composed of ____
Responsible for ____
pre-frontal cortex
responsible for EXECUTIVE FUNCTION (personality, foresight, insight)
What are the motor function areas of the frontal lobe?
this is the site of origin for ___ tract
primary motor cortex
premotor area
supplemental motor area
these are the origin of CORTICOSPINAL TRACT (voluntary movement)
Association areas mediate _____? (function)
higher mental functions (language, arts, music)
Very little is known about association area functions… Most information that we do know stems from ___
case reports of patients with naturally occurring lesions
____ has advanced our understanding of association areas
advent of functional imaging scans
What are the 2 broad types of association areas?
unimodal
multiomodal
Where is unimodal association cortex found?
Adjacent to the primary area that it’s associated with
Unimodal association cortex is devoted to ____
elaborating on business of primary area it’s associated with
Multimodal association cortex is responsible for ____ (function)
higher level INTELLECTUAL functions
Multimodal association cortex is found _____
inferior parietal lobule
much of frontal lobe
much of temporal lobe
Describe the dominant hemisphere vs. non-dominant hemispheres of the brain.
How does this relate to someone’s dominant vs. non-dominant hand?
dominant hemisphere: hemisphere that produces/comprehends language (often left)
non-dominant hemisphere: usually right
THIS IS REGARDLESS OF RIGHT/LEFT HANDED
Cortical language areas are located near what major cortical landmark?
the lateral sulcus
Describe the lateral sulcus on right vs left.
Asymmetry – which is longer? Why?
Lateral sulcus extends further posterior on LEFT than RIGHT.
Because left planum temporale is bigger on the right
(planum temporale = part of superior temporal gyrus posterior to primary auditory cortex)
What is the planum temporale? How does it relate to asymmetry of hemispheres?
planum temporale is part of superior temporal gyrus posterior to primary auditory cortex (it is bigger on the right than on the left)
which leads to the left lateral sulcus being longer posterior than the right.
Learning areas border _____ (major cortical landmark)
lateral sulcus
usually left
Learning areas near the lateral (left) sulcus can stimulate ____ which results in what?
can stimulate motor cortex near mouth to produce involuntary grunts/vocalization
What are the Perisylvian language areas?
Brocas area
Wernicke’s area
Broca’s are and Wernicke’s area are called ____ language areas
perisylvian
Broca’s area is located in the _____
inferior frontal gyrus (opercular/triangular part)
Wernicke’s area is located in ____
posteiror part of superior temporal gyrus
continuing into planum temporlae and inferior parietal lobe
Damage to perisylvian language areas can result in ___
aphasia
Describe aphasia (generally)
inability to use language
loss of use/access to words (symbols we use as concepts)
Cause by damage in wrenickes area or broca’s area
What are the 2 main types of aphasia (and what causes them?)
nonfluent aphasia - broca’s area damage
fluent aphasia - wrenicke’s area damage
Describe nonfluent aphasia (aka ___)
broca’s aphasia
make few written/spoken words, gets by with phases “ok”
very difficult to pronounce words
all detail and meaning in sentence is lost
CAN COMPREHEND LANGUAGE
Describe fluent aphasia (aka ___)
Wrenicke’s aphasia
can write and speak but words/sequence of words is incorrect
little to no linguistic content
can have paraphiasia (replace 1 letter/word for another) or neoglosim (make up new words)
DIFFICULTY COMPHRENDING LANGUAGE
Define paraphasia.
What type of aphasia is this associated with?
paraphasia - replace 1 letter/word with another
symptom of fluent aphasia
Define neologisms.
What type of aphasia is this associated with?
neologism - making up new words
symptom of fluent aphasia
Often, perisylvian areas are found in the left hemisphere.
Does the right hemisphere play a role in language? Describe.
Yes.
Emotional and rythmic language is produced and comprehended in diff parts of right hemisphere
Define prosody
musical elements of speech
produced/comprehended by right hemisphere
Prosody is produced by ____
damage = ____
right inferior frontal gyrus
damage = motor aprosody = can’t convey anger/authority/etc in language
Prosody is comprehended by ____
damage = ____
right posterior temporoparietal region
damage = sensory aprosody = can’t comprehend emotional content of others’ speech
Association areas are found ____
in parietal cortex
posterior to primary somatosensory cortex
What are the main unimodal association areas in parietal lobe?
visual, auditory, somatosensory association areas
Damage to parietal lobe unimodal association areas leads to _____ 3 things.
All associated with visual
remember unimodal association areas = visual, auditory, somatosensory association areas
agnosias.
agnosia = inability to interpret things/objects prosopagnosia = inability to recognize familiar faces akinetopsia = can't perceive motion
Multimodal areas of parietal lobe are centered on the ____ (cortical landmark)
main function is to ____
intraparietal sulcus
main function = monitor relationships of body with outside world
Left parietal lobe damage leads to _____
L parietal lobe = taking info needed to plan movement accurately
damage = APRAXIA = patient unable to perform certain planned actions.
can’t REPEAT certain gestures, but can do them naturally if needs to scratch
Right parietal lobe damage leads to ____
CONTRALATERAL NEGLECT patient has trouble w/ left half of body some deny that something is wrong with left limb or convinced left limb belongs to someone else ignore left half of body trouble copy image seen on left side
Prefrontal cortex is in the frontal lobe anterior to ___
primary motor areas and supplemental motor areas
Prefrontal cortex controls ____
activities of other cortical areas (underlies executive function)
Prefrontal cortex is heavily interconnected with ____
dorsomedial nucleus of thalamus
There are 2 broad types of prefrontal cortex. What are they?
- dorsolateral
2. ventromedial
Describe the dorsolateral prefrontal cortex
what does it lie over?
what is it interconnected with?
what is it’s function?
over lateral convexity
interconnected with parietal association areas
important role in WORKING MEMORY, problem planning, solving problems, maintaining attention
Describe the ventromedial prefrontal cortex
where is it?
what does damage lead to?
extends to orbitofrontal and anterior cingulate areas
damage = makes people impulsive and can’t suppress innapropriate responses/emotions
PHINIUS GAGE
