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FNS 7: Cerebrum

Neuro Lecture 7: Cerebral Cortex 1a

QuestionAnswer
By ____ of embryonic development, all 5 major brain subdivisions are identifiable. 5th week
Name the 5 major subdivisions of the brain telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon
Which subdivision of the brain contains the cerebral hemispheres and basal ganglia? telencephalon
The cerebral cortex accounts for about ___ of the volume of the adult brain 45%
Which cerebral hemisphere is larger than the other? right
How much is the overall loss of cortical volume by age 75? ~4%
How much is the loss of frontal cortical volume by age 75? ~12%
Do all cortical areas decrease in size the same amount? no different areas are differentially affected
Does each person’s cerebral cortex decrease the same amount? no- there is substantial individual variability
How big is the total flattened area of the cerebral cortex? ~200 cm2
How much of the cerebrum is visible on the external surface? 1/3
How thick is the cortex? ~1.5 - 4.5 mm
What’s the thickest part of the cortex? primary motor cortex
What’s the thinnest part of the cortex? primary visual cortex
How many neurons are contained in the mature cerebrum? about 20 billion
How many glial cells are contained in the mature cerebrum (compared to neurons)? 2-10x more
What are the 2 major groups of cortical neurons? spiny neurons and aspiny (spine-sparse) neurons
What percentage of cortical neurons are spiny neurons? about 75%
Are spiny neurons excitatory or inhibitory? excitatory
Which NT do spiny neurons use? glutamate
Which specific neurons are included in the group “spiny neurons”? pyramidal neurons and stellate neurons
Which type of neurons make up the majority of spiny neurons? pyramidal neurons
Which type of neuron is the major “output” neuron of the cortex? pyramidal neurons
What are the single long projections of the pyramidal neurons called? apical dendrites
What are the many smaller projections of the pyramidal neurons called? basilar dendrites
Due to the large density of spines on the spiny neurons, how many other neurons can contribute input to a single neuron? thousands
What types of conditions have shown reduction in cortical pyramidal spine density? dementias, chronic alcoholism, schizophrenia, and trisomy 21
Do aspiny neurons have spines? few, if any
What percentage of cortical neurons are aspiny neurons? about 25%
Are aspiny neurons excitatory or inhibitory? inhibitory
Which NT do aspiny neurons use? GABA- gamma aminobutyric acid
Are aspiny neurons presynaptic, postsynaptic, or interneurons? (not actually a technically sound question) interneurons
As interneurons, what is the (very general) function of aspiny neurons? make synaptic connections with nearby pyramidal cells- conductors/ traffic cops
Loss of which type of neurons have been reported in epileptic patients? chandelier cells (aspiny neurons)
What is the term for “superficial-to-deep” variations in histological features in the cerebral cortex? laminar organization
What is the term for “superficial-to-deep” commonalities in functional properties in the cerebral cortex? columnar organization
About 95% of the cortical area is termed _______, which has __ layers and is also known as _______ isocortex (“same cortex”), 6, neocortex
The other 5% of the cortical area is termed ______, which has __ layers and is also known as _______ or _______. allocortex, 3-5, archicortex or paleocortex
Name the 6 layers of the isocortex? 1. Molecular, 2. External Granular, 3. External Pyramidal, 4. Internal Granular, 5. Internal Pyramidal, 6. Multiform
What is the description of the first isocortex layer? rich in fibers, but few neurons
What is the description of the second isocortex layer? densely-packed small cells
What is the description of the third isocortex layer? medium-sized pyramidal cells
What is the description of the fourth isocortex layer? small pyramidal & stellate cells
What is the description of the fifth isocortex layer? many large pyramidal cells
What is the description of the sixth isocortex layer? mixture of pyramidal cells and irregularly-shaped cells
What are possible differences in cytoarchitecture between cortical layers? overall thickness, relative thickness/density of different layers, size/shape of neurons
(Brodmann’s map)- electrical stimulation studies have shown high correlation between ______ boundaries and ________ boundaries cytoarchitectonic and functional
Which cortical layer(s) are the origin of commissural and association fibers that connect different cortical regions? 2 and 3
Which types of cortical regions do commissural fibers connect? homologous regions between hemispheres (eg primary motor cortex)
Where do commissural fibers run? corpus callosum and anterior commissure
Which types of cortical regions do association fibers connect? heterologous regions within the same hemisphere
Where do association fibers run? in large fiber bundles (like superior longitudinal fasciculus)
Which cortical layer receives most afferent input from the thalamus? 4
Which cortical layer is best developed in primary sensory cortices? 4
Which cortical layer is the origin of projection fibers to subcortical regions (striatum, thalamus, SC)? 5, 6
Which cortical layer is particularly well-developed in the primary motor cortex? 5
What is the main cortical region receiving dopamine input? frontal cortex
Which cortical layers receive input from the basal forebrain/brainstem neuromodulatory systems? all 6
How wide are the columns of columnar organization in the cortex? 200-500 micrometers
Who discovered columnar organiztion? How? Mountcastle (1950s) inserted electrodes vertically and obliquely
All regions of cortex may be placed into one of 3 categories primary sensory areas (primary receptive cortex), primary motor areas (primary projection cortex), association areas
Which cortex has the lowest threshold for eliciting movement by electrical stimulation? primary motor cortex
Which cortex(ices) are the first regions to receive modality-specific information? primary sensory cortices
What is Brodmann’s area 3,1,2? primary somatosensory cortex
What is Brodmann’s area 4? primary motor cortex
What is Brodmann’s area 41? primary auditory cortex
What is Brodmann’s area 17? primary visual cortex
What are the 2 categories of association cortices? sensory association areas and motor association areas
Which cortex areas are areas of parietal, occipital, and temporal cortex that receive input from primary sensory areas? sensory association areas
Which cortex areas integrate information from different modalities? sensory association areas
Where are motor association areas located? frontal lobe
Which cortex areas project to the primary motor cortex? motor association areas
Which cortex areas provide dense input to subcortical regions involved with movement generation (eg basal ganglia)? motor association areas
What is cerebral lateralization? Many complex brain functions are more dependent on one hemisphere than the other
Which hemisphere controls language skills for a large majority of people (of either handedness)? left hemisphere (95% of righties & 75% of lefties)
What are some examples of cerebral lateralization? language, musical ability, attention, math
What is aphasia? without speech
What is affected (more specifically) with aphasia? loss of language expression and/or comprehension
What is agnosia? without knowledge
What is affected (more specifically) with agnosia? difficulty recognizing the meaning or sensory stimuli, while primary sensory function is intact
What is apraxia? without capability
What is affected (specifically) with apraxia? inability to carry out skilled or purposeful movement- no frank paralysis
Created by: mbyess