Association Cortices Flashcards
what is the function of the heteromodal association cortex?
puts together information provided by various unimodal association areas to accomplish more complex functions
what makes up most of the cerebral surface of the brain?
heteromodal association cortices
what are the heteromodal association cortices responsible for?
complex processing that goes on between the arrival of input to the primary sensory cortices and the generation of behaviour
what components can cognition be divided into?
- attending to complex stimuli (parietal cortex)
- identifying complex stimuli (temporal cortex)
- responding to complex stimuli (frontal cortex)
what is cognition?
process by which we come to know the world
if we have a lesion to the right parietal cortex what do we typically see?
unilateral neglect
if we have lesion to the left parietal cortex what do we typically see?
apraxia
what is apraxia?
(difficulty with small coordinated movements)
if we have damage to the right temporal cortex what do we typically see?
visual agnosias
if we have damage to the left temporal cortex what do we typically see?
difficulties with language
what do some people say is the one thing that makes us human?
the frontal cortex
what is the neocortex?
described most of the cortex covering the cerebral hemispheres
how many layers does the neocortex have?
6 cellular layers with distinct cell populations:
-density
-size
-shape
each cortical region of the neocortex has distinct connections, what are they?
- primary source of inputs and outputs
- vertical and horizontal axis connections
- radial alignment
- inter-neurons connect functional similar groups
what are the 3 main inputs of the heteromodal cortex?
- thalamus
- other cortical areas
- brainstem modulatory systems
what areas of the thalamus receive information from the cortex (down from the brain)?
mediodorsal nucleus of the thalamus
pulvinar nucleus of the thalamus
where does the mediodorsal nucleus of the thalamus send information out to?
frontal association cortex
where does the pulvinar nucleus of the thalamus send information out to?
parietal association cortex
are the nuclei used for primary, sensory, and motor functions involved in higher level processing?
no
wata re the main sources of input to association cortices?
- ipsilateral connections
- inter-hemispheric connections
what are ipsilateral connections?
from primary to secondary sensory and motor cortices on same side of brain
what are inter-hemispheric connections?
from corresponding and non-corresponding regions of cortex on the other side of the brain (via corpus callous and anterior commissure)
what is an example of a corresponding cortical area?
the right temporal association cortex is sending information to the left temporal association cortex
what is an example of a non-corresponding cortical area?
the left temporal association talking to the right parietal association cortex
what are the brainstem modulatory centres like?
dimmer switches
what do the brainstem modulatory centres do?
they emit neurotransmitters
they turn the overall activity in the brain either up or down
where are the brainstem modulatory centres?
- upper brainstem
- upper brainstem +reticular formation
- basal forebrain
what are the 4 main outputs to the heteromodal association cortices?
- other cortical areas (ipsilateral)
- other cortical areas (contralateral)
- subcortical structures
- thalamus
does each layer of the neocortex have vertical or horizontal connections?
both!
in the neocortex, cells with similar functions are wired together into what?
columns arranged radially
what is the content of consciousness?
things like what makes us unique individuals:
memory, emotions, motor/sensory functions
ex. little voice in your head that makes you you
what is the level of consciousness divided into?
alertness
attention
awareness
what is level of consciousness sustained by?
consciousness system networks
what are the 4 key brain areas that sustain the consciousness system networks?
- upper brainstem (midbrain)
- thalamus (diencephalon)
- hypothalamus (diencephalon)
4.basal forebrain (bottom of the front of the brain)
in order to be alert what do we need?
consciousness system network
some activity in the cortex in general
in order to be attending, what do we need?
same circuits as alertness
fronto-parietal association cortex
what is awareness?
the ability to perceive, to feel, to be conscious of events, objects, or sensory patterns
what are the bran areas involved in alertness?
brainstem
diencephalon
basal forebrain
cortex
what are the determinants of alertness?
- neuromodulatory systems in the brainstem
- the cortical regions to which these neuromodulatory systems project
what are neuromodulatory stems sometimes called?
subcortical arousal system
what does each brainstem neuromodulaotry system impact?
either alertness or cognitive processes
what are the 3 main ways alertness is increased?
- ascending sensory inputs (eg. anterolateral pathway)
ex. pain can increase alertness such as getting a vaccine
- frontoparietal association and limbic cortices
ex. cognitive and emotional processed can modulate alertness (having relationships issues)
- hypothalamus
ex. fight or flight (hearing something at nighttime)
what happens when we damage these systems?
overall lack of alertness/consciousness
what are the 3 distinct levels of lack of consciousness?
coma
vegetative state
minimally conscious state
if someone is dead how much function is there in their brain?
none, absent
what do we see a lack of in terms of consciousness in a coma?
lack of purposeful responses (anything that requires the cortex to process and plan)
what may a person in a coma show?
reflexive eye movements
respiratory movements
posturing
what is the lowest level of a lack of consciousness?
coma
what are the 2 main types of posturing?
decorticate (damage to corticospinal tract)
decerebrate (damage to the rubrospinal tract)
is decorticate or decerebrate posturing worse?
decerebrate
what will we not see in someone in a vegetative state?
no meaningful responses, speech or gestures
what may we see in someone in a vegetative state?
open eyes and arouse in response to stimulation (pain input may cause this briefly)
may turn eyes and head toward auditory and tactile stimulation
may make unintelligible sounds
does the minimally conscious state have to occur after the vegetative state?
it can occur after or as a primary state
what may be one of the earliest signs in minimally conscious state?
visual tracking
in a minimally conscious state, do people have a reliable yes/no?
No
how can be measure consciousness?
Glasgow coma scale
what area of the brain is severely depressed when someone has locked in syndrome?
upper brainstem (pyramidal decussation)
what does acetylcholine do?
allows us to be really alert and remember things
without what neurotransmitter and we not very likely to be alert?
acetylcholine
what part of the brain does acetylcholine go too?
very broad projections, all over the brain
what does dopamine do?
movement and initiative
alertness and attention
what brain structure is very important for attention?
prefrontal cortex
what brain area sends dopamine to the prefrontal cortex?
ventral tegmental area
what is crucial for sustained attention and concentration?
dopamine
