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
