Hippocampus

Cross references:    Dictionary    Figure Labels   Amygdala    
Amygdaloid Hippocampal Convergence   
Basal Ganglia    Fornix    Subiculum    

Kolb and Whishaw discuss the hippocampus on numerous pages, some with pictures: [K&W: 58-59, 180-186, 418, 427 & 502-505]. 

Hippocampus (Wiki) 
    "The hippocampus (named after its resemblance to the seahorse, from the Greek ἱππόκαμπος, "seahorse" from ἵππος hippos, "horse" and κάμπος kampos, "sea monster") is a major component of the brains of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory and spatial navigation. The hippocampus is located under the cerebral cortex;[1] and in primates it is located in the medial temporal lobe, underneath the cortical surface. It contains two main interlocking parts: the hippocampus proper (also called Ammon's horn)[2] and the dentate gyrus.  


https://upload.wikimedia.org/wikipedia/commons/2/2e/Gray739-emphasizing-hippocampus.png


In Alzheimer's disease, the hippocampus is one of the first regions of the brain to suffer damage; memory loss and disorientation are included among the early symptoms. Damage to the hippocampus can also result from oxygen starvation (hypoxia), encephalitis, or medial temporal lobe epilepsy. People with extensive, bilateral hippocampal damage may experience anterograde amnesia—the inability to form and retain new memories.

In rodents, the hippocampus has been studied extensively as part of a brain system responsible for spatial memory and navigation. Many neurons in the rat and mouse hippocampus respond as place cells: that is, they fire bursts of action potentials when the animal passes through a specific part of its environment. Hippocampal place cells interact extensively with head direction cells, whose activity acts as an inertial compass, and conjecturally with grid cells in the neighboring entorhinal cortex.

Since different neuronal cell types are neatly organized into layers in the hippocampus, it has frequently been used as a model system for studying neurophysiology. The form of neural plasticity known as long-term potentiation (LTP) was first discovered to occur in the hippocampus and has often been studied in this structure. LTP is widely believed to be one of the main neural mechanisms by which memory is stored in the brain.

Contents



1975    517<518 
Fimbria input to the nucleus accumbens septi.  

No Abstract, but:  

The picture, below, is from: 
Subiculum - Wikipedia   
https://en.wikipedia.org/wiki/Subiculum   



https://upload.wikimedia.org/wikipedia/commons/3/39/Hippocampus_%28brain%29.jpg






1985    490<518  
Inhibition from locus coeruleus of nucleus accumbens neurons activated by hippocampal stimulation.   

    "
Electrophysiological studies using rats were performed to examine the influence of locus coeruleus (LC) on nucleus accumbens (Acc) neurons. Spike generation by hippocampal stimulation was inhibited by both LC conditioning stimulation and iontophoretic application of noradrenaline, but spikes elicited by stimulation of parafascicular nucleus of thalamus were rarely affected by LC conditioning stimulation or noradrenaline. The LC-induced inhibition was antagonized by iontophoretic sotalol, but not by phentolamine, suggesting that noradrenaline derived from the LC inhibits the Acc neurons receiving input from the hippocampus, probably acting on a beta-adrenergic receptor."  


1989    459<518 
Convergence of hippocampal and dopaminergic input onto identified neurons in the nucleus accumbens of the rat.  

    "
The hippocampal input to the nucleus accumbens was interrupted by an electrolytic lesion of the fimbria-fornix. Boutons degenerating as a result of this lesion were found in asymmetric synaptic contact with dendritic spines and shafts in the medial part of the nucleus accumbens. Dopaminergic fibres and terminals in this area, identified using an antibody to tyrosine hydroxylase, established symmetrical synaptic contacts with dendritic shafts, spines and somata. In material where neurons in the nucleus accumbens had been Golgi-impregnated, it was found that the hippocampal and dopaminergic inputs converge onto the same neurons, and that the post-synaptic targets could be either spiny or aspiny neurons. It has been suggested that hippocampal dysfunction is involved in schizophrenia and this convergence of input from the hippocampus onto the same neurons that are post-synaptic to the dopaminergic input, which presumably originates from neurons in the ventral tegmental area, may provide an anatomical basis for the therapeutic effects of neuroleptic drugs which are dopamine antagonists."  


1990    450<518  
Hippocampal fibers make synaptic contacts with glutamate decarboxylase-immunoreactive neurons in the rat nucleus accumbens.  
    "A
xons arising in the hippocampal formation form asymmetric synapses with glutamate decarboxylase-immunoreactive neurons in nucleus accumbens. The postsynaptic targets included many spines, and less frequently dendritic shafts and perikarya. Some immunolabelled neurons resemble medium-sized, spiny projection neurons which suggests that the input from the hippocampal formation exerts a strong and direct influence on output pathways of nucleus accumbens."    


1991    438<518 
The contribution of basal forebrain to limbic-motor integration and the mediation of motivation to action.   
    "
The contribution of hippocampal glutamatergic and VTA dopaminergic inputs to the nucleus accumbens and the role of accumbens--ventral and subpallidal GABAergic pathway in integrating the limbic signals into motor responses via pedunculopontine nucleus were examined with electrophysiological and behavioural techniques.  
    Stimulation of hippocampal input to the accumbens activates GABAergic output to the subpallidal area which leads to suppression of spontaneous firing of subpallidal neurons, while activation of dopamine receptors in the accumbens suppresses GABAergic output to subpallidal area and thus increases the firing of picrotoxin-sensitive ventral pallidal neurons.  
    However, both treatments induced hypermotility suggesting the functional heterogeneity of the ventral and subpallidal areas in "limbic-motor integration". Furthermore, both hippocampal output signals and dopaminergic input to the accumbens descend via ventral and subpallidal areas serially to the pedunculopontine nucleus, the region of the mesencephalic locomotor region. In addition, a parallel ascending pathway from the subpallidal area to the mediodorsal nucleus, and subsequently to the medial prefrontal cortex, probably mediates behaviour, e.g. food hoarding, that requires higher cognitive processing."  



2002   
107<170    Free Article
Receptors with different affinities mediate phasic and tonic GABA(A) conductances in hippocampal neurons.  


2002   
103<170 
Ectopic expression of the GABA(A) receptor alpha6 subunit in hippocampal pyramidal neurons produces extrasynaptic receptors and an increased tonic inhibition.











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