Lecture 01 - Cerebral Cortex Flashcards
Cerebral Cortex Features
4 lobes:
-frontal, parietal, occipital, temporal
gyri - “ridges” winding around brain
sulci - small grooves that divide the gyri (increase SA)
fissures - deep grooves dividing large regions/lobes
-longitudinal (divide two cerebral hemispheres)
-transverse (separates cerebrum from cerebellum)
-sylvian/lateral (divides temporal from frontal and parietal, deep is the insula)
Cerebral gray matter
90% 6 layered neocortex, but layers differ between areas
-pyramidals and stellates are excitatory (glutamate)
-interneurons are inhibitory or use GABA
-there are some more primitive areas not 6 layered
3 layers (paleocortex - olfaction)
4 layers (archicortex - hippocampus)
Brodmann’s areas:
17 - primary visual cortex
3,1,2 - primary somatosensory
41,42 - primary auditory
various ways to figure out cortical function
- lesion –> what is the deficit? (dangerous, can affect many different functions)
- stimulate –> what is the action? (can stimulate multiple locations)
- Record, what is the activity
- fMRI –> what/where is activity (increased blood supply)?
4 main types of functional regions
- primary sensory
- primary motor
- associate areas
- limbic (emotional) areas
***many higher order processes no confined to single cortical area (distributed network)
Primary sensory cortex
Inputs:
- visual (occipital)
- auditory (temporal)
- vestibular (temporal region deep to auditory and insula)
- somatosensory (parietal)
- gustatory (taste - deep to lateral fissure on insula)
- olfaction (smell) some of this info gets to insula (flavor)
* **all go to primary cortex via the primary thalamus (except olfactory - majority goes direct to cortex, piriform cortex )
Primary motor cortex
Inputs: 1. LMNs 2. UMNs 3. prefrontal 4. secondary motor 5. posterior parietal cortex *** plan and execute movement Layer 5 UMN output to activate LMNs
Association cortex
Process raw sensory signals into concepts that can be:
- remembered
- used to create new ideas
- formulated into action via motor outputs
(allows you to attend to ext. stimuli and int. motivation, identify stimulus and its significance, make responses)
Unimodal sensory
Part of association cortex
- next to/surrounds primary area (2ndary sensory)
- still focused on that sense
- primary input from primary cortex –> lose primary, lose 2ndary responses (some inpute from thalamus)
- responds best to more complex stimuli
Unimodal motor
part of association cortex
Supplementary Motor Cortex (SMA)
-projects to brainstem/spinal cord and acts on LMS and primary motor cortex
-higher threshold and makes more complex motor patterns
-inputs from other cortical areas, including BG and cerebellum via the thalamus
-internally generated selected movement (I think I’ll twerk!)
Lateral pre-motor cortex (PMC)
- all the same except receive innervation from posterior parietal cortex
- externally generated movements (reaching/grasping)
Multimodal
part of association cortex - the rest
“higher order” - highly developed in humans
-much of thalamic input is pre-processed info
-most inputs from other cortical areas also pre-processed
-subcortical inputs from modulators
***distributed networks for higher cortical function
-what we know derived from effects of lesions, but lots of variability
Axon pathways
locally - corticocortical
across to other lobe - via corpus callosum or commissural
down to lower structures - corticofugally
Sup. longitudinal fasciculus - connects cortex of 4 lobes
Inf. longitudinal fasciculus - connects temporal and occipital
uncinate fasciculus - deep to sylvian fissure to connect frontal lobe with rostral temporal lobe
cinglulum - runs with cingulate and parahippocampal gyri
Network function
massive inputs to and outputs from each cortical lobe
- many options for one part of cortex to talk to another part
- tons of connections between hemispheres too
- some functions predominate on one side of the brain
- lesion may affect cortical function but many other areas are involved in that function thru interconnections (lesion may cause a loss but is not necessarily where the function is located, due to connections)
Speech language pathway
starts in cochlea –> auditory nerve –> cochlear nucleus –> superior olive –> inferior colliculus –> medial geniculate –> primary auditory cortex –> secondary auditory cortical areas –> Wernickes –> Brocas
Also:
1. connections from 2ndary auditory cortical areas to ventral pathway (understanding) along lateral temporal
2. dorsal pathway to articulation centers in frontal cortex
***left side dominant
Two streams
Dorsal stream - “where/how”
Ventral stream - “what”
-ventral connected with medial temporal and limbic (long-term memory and emotion)
-influenced by extraretinal factors (attention, working memory, stimulus salience)
-ventral stream provides description but also plays role in judging significance
-disruption of connection between dorsal and ventral may lead to spatial neglect –> TPO junction lesion
spatial neglect
patient ignores things in contralateral space, including their own bodies
- primarily occurs with right hemisphere lesions
- right parietal love attending to both left and right hemispace, while left side only attends to right
