In insula are hippocampus major {horn of Ammon} and hippocampus minor {hippocampus}| [Freund and Buzsáki, 1996] [Parra et al., 1998].
functions
Hippocampus is for long-term and short-term memory. It is necessary to store new memories, but conscious associative fact and event memory also requires other brain regions. Hippocampus is for motivation, reward, rehearsal, and space. It controls ergotropic behavior through sympathetic nervous system. It detects movement direction, head attitude with respect to body, and movement sequence. Neurons can find relations among facts and experiences. Neurons can find fact and experience conjunctions, while neocortex builds learning structures.
damage
Hippocampus damage blocks habituation to repeated stimulation. Hippocampal formation and parahippocampal cortex loss causes inability to consciously remember facts or events, such as new category members or unique examples. Damage does not affect perceptual-motor skills with no conscious internal representations, such as mastering task over several sessions or retrieving previously acquired factual knowledge. Hippocampus damage does not affect perception, consciousness, habits, skills, language, classical conditioning, instrumental conditioning, or motor control.
damage: Alzheimer's
In Alzheimer's disease, basal-forebrain cholinergic-neuron degeneration causes low hippocampal choline acetyltransferase activity.
input
Parahippocampal gyrus and hippocampus have multisensory cells.
output
Hippocampus sends through septum and nucleus accumbens to hypothalamus. It sends to cholinergic neurons at forebrain base, nucleus basalis magnocellularis, medial septal nucleus, and nucleus of diagonal band of Broca. It connects to medial temporal lobe.
process: memory
Brain stores memory only if cerebral neocortex sends information to three different areas close to hippocampus and then into hippocampus itself. Hippocampus then passes message back through medial temporal lobe to originating site in cerebral neocortex.
process: place
Spatial information travels from thalamus to neocortex to hippocampus. Hippocampus has non-topographic cognitive space map, stored in pyramidal place cells. Place-cell fields are stable and form in minutes [Brown et al., 1998]. Place cells increase firing when body is at that location [Ekstrom et al., 2003] [Frank et al., 2000] [Nadel and Eichenbaum, 1999] [O'Keefe and Nadel, 1978] [Rolls, 1999] [Scalaidhe et al., 1997] [Wilson and McNaughton, 1993] [Zhang et al., 1998]. Place cells also recognize textures, objects, and contexts. For example, they fire only when animal sees face (face cell), hairbrush, or hand.
waves
Hippocampus has 4-Hz to 10-Hz theta rhythm during active movement and alert immobility, synchronized between hemispheres in 8-mm region along hippocampus longitudinal axis. Other behaviors have local and bilaterally synchronous 40-Hz rhythm. A 200-Hz wave associates with alert immobility. Awake brain has synchrony, which increases with attention and preparation for motor acts. When neocortex desynchronizes with low-voltage rapid potentials, hippocampus synchronizes with theta waves. When neocortex synchronizes, hippocampus desynchronizes.
Frontal lobe has hippocampus major, hippocampus minor, and subiculum {hippocampal formation}.
Spatial information travels from thalamus to neocortex to hippocampus. Hippocampus has non-topographic cognitive space map, stored in pyramidal place cells. Some hippocampus neurons {place cell, hippocampus} increase firing when body is at that location [Ekstrom et al., 2003] [Frank et al., 2000] [Nadel and Eichenbaum, 1999] [O'Keefe and Nadel, 1978] [Rolls, 1999] [Scalaidhe et al., 1997] [Wilson and McNaughton, 1993] [Zhang et al., 1998]. Place-cell fields are stable and form in minutes [Brown et al., 1998]. Place cells also recognize textures, objects, and contexts. For example, they fire only when animal sees face (face cell), hairbrush, or hand.
Primate hippocampus has some neurons {spatial view cell} that fire only when viewing or recalling a location (with 30 degrees), no matter what head orientation or body location.
4-Zoology-Organ-Nerve-Brain-Cerebrum-Frontal Lobe
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Date Modified: 2022.0225