Limbic System Flashcards
- links a group of functionally related structures that are interposed between the cerebral cortex and the underlying diencephalon
- hippocampal formation, septal area, and amygdala
- prefrontal cortex and cingulate gyrus as components within this system
limbic system
- either directly or indirectly communicate with the hypothalamus or midbrain periaqueductal gray (PAG)
- modulate the functions normally attributed to the hypothalamus and/or midbrain
limbic structures
limbic structures receive inputs from at least two sources
- one or more sensory systems, either directly or indirectly through interneurons in the cerebral cortex
- brainstem monoaminergic fiber system
The hippocampal formation consists of the ___, ___, and __-
hippocampus; dentate gyrus; subicular cortex
The primary cell type within the hippocampus is the ___, which has both basal and apical dendrites
pyramidal cell
extend laterally and slightly in the direction of the ventricular surface
basal dendrites
extend away from the ventricular surface toward the dentate gyrus
apical dendrites
- superficial layer of the hippocampus
- fiber layer adjacent to the inferior horn of the lateral ventricle
alveus
situated adjacent to the inferior horn of the lateral ventricle, which contains axons of pyramidal cells that project out- side the hippocampus as well as hippocampal afferent fibers from the entorhinal cortex
external plexiform layer
contains basal dendrites and basket cells
stratum oriens
contains the pyramidal cells of the hippocampus
pyramidal cell layer
two layers that contain the apical dendrites of the pyramidal cells and hippocampal afferents from the entorhinal cortex
stratum radiatum and stratum lacunosum-moleculare
pyramidal cells of the hippocampus are arranged in a ___
C-shaped fashion
the pyramidal cells situated closest to the subiculum are referred to as the
CA1 field
pyramidal cells located within the hilus of the dentate gyrus
CA4 field
located between the CA1 and CA4 fields
CA2 & CA3 fields
- Collaterals of axons arising from CA3 pyramidal cells project back to the CA1 field
recurrent or schaffer collaterals
CA1 field, the pyramidal cells are highly susceptible to anoxia, especially during periods of temporal lobe epilepsy. This region is referred to as ___
Sommerβs sector
The dentate gyrus can also be thought of as a primitive three-layered cortical structure. It is multilayered, and the principal cell type is the ___
granule cell
axon of the granule cell, called a ___, makes synaptic contact with pyramidal cells in the CA3 region
mossy fiber
passes from the lateral entorhinal cortex into the molecular layer of the hippocampus
lateral perforant pathway
- medial pathway
- enters the alveus of the hippocampus after passing through the white matter adjoining the subiculum
medial perforant pathway
- passes rostral to the anterior commissure and supplies the septal area
- topographically organized in that fibers situated near the anterior pole of the hippocampal formation project to the lateral aspect of the lateral septal nucleus, whereas neurons situated more posteriorly in the hippocampal formation project to progressively more medial aspects of this nucleus
- arises from the hippocampus and subicular cortex
precommissural fornix
- innervates the anterior thalamic nucleus, mammillary bodies, and adjoining regions of the medial hypothalamus
- arises solely from the subicular cortex
postcommissural fornix
enable the hippocampal formation to communicate with widespread regions of neocortex, including areas that receive different modalities of sensory information
subicular and entorhinal cortex
- provides connections between the hippocampus on each side of the brain
- provide the structural basis by which seizures spread from the hippocampus on one side of the brain to the hippocampus on the other side, allowing for the formation of secondary epileptogenic foci on the side of the temporal lobe contralateral to the site where the primary focus is present
commissural component
hippocampal formation plays an important role in the control of ___ behavior
aggression and rage
activation of the part of the hippocampal formation closest to the amygdala facilitates ___, whereas activation of the portion closest to the septal pole ___ this form of aggression
predatory attack behavior; suppresses
- arises from the subiculum near the temporal pole of hippocampus and projects directly to the ventromedial region of the hypothalamus
- terminates in the region between suprachiasmatic and arcuate nuclei, which contain hypophysiotrophic hormones that control anterior pituitary function
medial corticohypothalamic tract
slow wave of 4β7 Hz
theta rhythm
Normally, a rat can learn to enter the correct arm of a Y-maze or the correct series of arms in a more com- plicated maze such as an eight-armed radial maze. Animals sustaining hippocampal lesions consistently fail to approach the correct arm of the maze and consistently make the same or similar kinds of errors
spatial learning (spatial memory)
individual hippocampal cells change their discharge patterns as the animal moves to different parts of the cage or when it is placed in differ- ent arms of a radial maze
cognitive map
- earliest reported disorders
- memory disorder in which the patient displays amnesia (memory loss) of both anterograde and retrograde memory
- patient experiences a great deal of difficulty in recalling events in the recent past and handling and retaining new information as well as remembering those events that took place in the distant past
- associated with the toxic effects of alcohol or from a vitamin B1 (thiamine) deficiency
Korsakoffβs syndrome
memory loss that occurs after hippocampal damage
Anterograde memory
refers to loss of memory that occurs before damage to the hippocampus
retrograde memory loss
pathway linking the hippocampal formation
Papez circuit
- Patients sustaining hippocampal lobectomies display perseveration of response tendencies and further display
- patient displays anterograde amnesia, but retrograde amnesia is less severe
- Such a patient may also have difficulty in reading, in that he is unable to remember a previously read line
short-term memory disorder
- hippocampal mechanism that has been proposed as a model for memory consolidation
- represents a change in synaptic strength as a manifestation of synaptic plasticity. LTP can be produced by stimulating fibers that make excitatory connections with hippocampal pyramidal cells
long-term potentiation (LTP)
- receives sensory afferent fibers from the medial olfactory stria, monoaminergic systems of the brainstem, hippocampal formation, amygdala, and feed- back signals from the lateral hypothalamus
- serves principally as a relay of the hippocampal formation to the hypothalamus
septal area
serve to modulate septal neuronal activity, as do the olfactory inputs
monoaminergic inputs
- The nuclei of the ___ have wide- spread projections that make synaptic connections with other parts of the limbic system
- project to olfactory, prefrontal, and anterior cingulate cortices as well as to the amygdala, mammillary bodies, habenular complex, and mediodorsal thalamic nucleus
diagonal band of Broca
feedback system to the hippocampal formation
septal area
- implicated in the control of functions normally attributable to the hypothalamus, such as aggression, rage, autonomic functions, self-stimulation, and drinking behavior
- lesions of the septal area in rats cause them to be highly irritable, aggressive, easily startled, and very difficult to handle
septal rage
stimulation of the septal area suppresses ___ secretion and adrenal activity in the rat
ACTH
lesions of the septal area facilitate ___ release
ACTH