![mouse hippocampus anatomy slm mouse hippocampus anatomy slm](https://media.springernature.com/original/springer-static/image/chp%3A10.1007%2F978-3-030-19898-5_11/MediaObjects/459632_1_En_11_Fig1_HTML.jpg)
In rodents as model organisms, the hippocampus has been studied extensively as part of a brain system responsible for spatial memory and navigation. LTP is widely believed to be one of the main neural mechanisms by which memories are stored in the brain.
![mouse hippocampus anatomy slm mouse hippocampus anatomy slm](https://ars.els-cdn.com/content/image/1-s2.0-S0896627318305816-fx1.jpg)
The form of neural plasticity known as long-term potentiation (LTP) was initially discovered to occur in the hippocampus and has often been studied in this structure. 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. People with extensive, bilateral hippocampal damage may experience anterograde amnesia: the inability to form and retain new memories. Damage to the hippocampus can also result from oxygen starvation ( hypoxia), encephalitis, or medial temporal lobe epilepsy. In Alzheimer's disease (and other forms of dementia), the hippocampus is one of the first regions of the brain to suffer damage short-term memory loss and disorientation are included among the early symptoms.
![mouse hippocampus anatomy slm mouse hippocampus anatomy slm](https://media.springernature.com/lw685/springer-static/image/art%3A10.1038%2Fncomms2318/MediaObjects/41467_2012_Article_BFncomms2318_Fig1_HTML.jpg)
In humans, it contains two main interlocking parts: the hippocampus proper (also called Ammon's horn), and the dentate gyrus. The hippocampus, as the medial pallium, is a structure found in all vertebrates. The hippocampus is located in the allocortex, with neural projections into the neocortex in humans, as well as primates. The hippocampus is part of the limbic system, and plays important roles in the consolidation of information from short-term memory to long-term memory, and in spatial memory that enables navigation. Humans and other mammals have two hippocampi, one in each side of the brain. However, in Ts65Dn, Bonferroni post-hoc analysis indicates that at each frequency SLM stimuli produced a significantly greater GABA B/GABA A ratio than SR stimuli (*p<0.05 ***p<0.001).The hippocampus (via Latin from Greek ἱππόκαμπος, ' seahorse') is a major component of the brain of humans and other vertebrates.
![mouse hippocampus anatomy slm mouse hippocampus anatomy slm](https://www.jneurosci.org/content/jneuro/31/30/10948/F1.large.jpg)
Bonferroni post-hoc analysis showed no significant differences between diploid SR and SLM for any single frequency. The inset shows the ratios for each frequency delivered. There is no difference between diploid and Ts65Dn for SR stimuli, however, Ts65Dn SLM shows significantly higher charge ratios than diploid SLM (two-way ANOVA, *****p<0.0005). (B) The charge transfer ratio of GABA B and GABA A receptor mediated currents (the ratio of total area under the GABA B or GABA A current curve for the entire train of five synaptic stimuli) is significantly greater for SLM (hatched bars) than SR (solid bars) stimuli in both diploid (white bars two-way ANOVA: SR n=13-14, SLM n=15, ***p<0.001) and Ts65Dn neurons (red bars two-way ANOVA: SR n=12, SLM n=11, ****p<0.0001). (A) Examples of GABA B (blue) and GABA A (red, digitally subtracted) responses to SR and SLM stimuli at 20Hz for Ts65Dn mouse. These results indicate that GIRK overexpression in Ts65Dn has functional consequences which affect the balance between GABA(B) and GABA(A) inhibition of CA1 pyramidal neurons, most likely in a pathway specific manner, and may contribute to cognitive deficits reported in these mice. However, the GABA(B)/GABA(A) ratios evoked by stimulation within the SLM of Ts65Dn hippocampus were significantly larger in magnitude, consistent with increased GABA(B)/GIRK currents after SLM stimulation. Synaptic GABA(B) and GABA(A) mediated currents evoked by SR stimulation were generally unaffected in Ts65Dn CA1 neurons. After confirming that GABA(B)/GIRK current density is significantly elevated in Ts65Dn CA1 pyramidal neurons, we compared monosynaptic inhibitory inputs in CA1 pyramidal neurons in response to proximal (stratum radiatum SR) and distal (stratum lacunosum moleculare SLM) stimulation of diploid and Ts65Dn acute hippocampal slices. Since Ts65Dn mice overexpress G-protein coupled inward-rectifying potassium (GIRK2) containing channels, we sought to evaluate whether increased GABAergic function disrupts the functioning of hippocampal circuitry. GABAergic dysfunction is implicated in hippocampal deficits of the Ts65Dn mouse model of Down syndrome (DS).