Frontal Lobes and Hippocampus Flashcards
executive function
describes the prefrontal cortex (PFC) function, it directly enhances and inhibits certain neural networks for motor planning, selective attention related to current goals. It also enhances and inhibits interoceptive stimuli for emotional control
subdivisions of the PFC
dorsolateral prefrontal cortex (DLPFC)
venteromedial prefrontal cortex (VMPFC)
anterior cingulate cortex (ACC)
DLPFC inputs
somatosensory, visual, and auditory association areas in the parietal, occipital, and temporal lobes. Also some re-entrant basal ganglia-thalamocortical circuits
DLPFC modulation
by cholinergic and monoaminergic inputs from basal forebrain and brainstem (which have input from the venteromedial PFC)
DLPFC outputs
to the premotor cortex, somatosensory association cortices, and some to the brainstem specifically the sup. colliculus, midbrain tegmentum, and PAG
DLPFC lesions
inability to employ intention (goals) to modulate attention (task at hand), fail to switch attention appropriately = perseveration, lack of internally generated goal and need to environmental cues = environmental dependency
VMPFC inputs
somatosensory, visual, and auditory association cortices but less so that the DLPFC. More from olfactory, gustatory, and visceral inputs. Also basal amygdaloid complex and parahippocampal cortices. and re-entrant basal ganglia thalamocortical circuits
VMPFC outputs
reciprocal relationship with cholinergic cells in the basal forebrain and monoaminergic cells in the brainstem and hypothalamus. also projections to the lateral and posterior hypothalamus where it connects with stress and ANS control centers. also direct brainstem projections to the PAG, nucleus tractus solitarius, and dorsal motor nucleus of the vagus.
VMPFC lesions
on the Iowa Gambling Task, continue to draw from the bad deck even when they know theyre losing, never develop a stress response to impending punishment. Don’t have adequate inhibition of aggression, sexual behavior, anxiety, appetitive functions. Impairment of the risk/reward association.
Iowa Gambling Task
presents people with 4 card decks, some cards you win money some you lose. some decks are bad and have more losses in them than the good decks. usually healthy participants after some trials will prefer the good decks and will show a stress response when choosing from bad decks even before being consciously aware that they are bad decks.
ACC lesions
ACC is linked to focus mental effort, so when lesioned, they have abulia or lack of will to do things.
PFC function generally
guidance of flow along task relevant pathways, mapping of things as origins and destinations. With a lesion, they don’t do tasks in the appropriate order
hippocampus function
holds declarative/episodic and spatial memories, but transfers long term memories to the neocortex for storing, the hippocampus is the search engine for finding memories within the neocortex (important for planning the future and generating creative ideas), also the GPS of the brain
place cells
encode space through firing patterns of the hippocampus. Single hippocampal neurons increase their firing rate when in a particular spot
grid cells
neurons not in the hippocampus but in the entorhinal cortex (principle input into the hippocampus) have an arrangement of spatial firing fields at equal distances from their neighbors, they encode a cognitive representation of euclidean space allowing for dynamic computation of self-position based on continuously updated info about space and direction
the hippocampal formation
dentate gyrus
hippocampus
subiculum (transition zone between the three layered hippocampus and 6 layered entorhinal complex
trisynaptic circuit
entorhinal cortex neurons go to the dentate gyrus
granule cells there send mossy fibers to the CA3 field of the hippocampus
some form autoassociations and other pyramid cells/schaffer collaterals from there go to CA1
info from CA1 goes to the subiculum
info then is sent back to the entorhinal cortex to the cortical association areas
perforant path
major projection from the entorhinal cortex to the dentate gyrus and hippocampus (crosses/perforates the hippocampal fissure to reach the dentate)
schaffer collaterals
axon collaterals from CA3 to CA1
autoassociation memory
neural networks that allow you to retrieve entire memories from a tiny sample of it.
modular organization of grid cell networks
there is a stepwise increase in grid spacing at successive dorsoventral levels of the medial entorhinal cortex
standard model of memory consolidation
the hippocampus rapidly and automatically acquires info
it has limited capacity and is subject to rapid forgetting
info from the hippocampus is permanantly stored in the cortex
the hippocampus plays a critical role in genesis of cortical memories.
memory is retained in the hippocampus for about a week after initial learning
