Hippocampus memory retrieval

Hall J, Thomas KL, Everitt BJ (2001a) Cellular imaging of zif268 expression in the hippocampus and amygdala during contextual and cued fear memory retrieval selective activation of hippocampal CAl neurons during the recall of contextual memories. J Neurosci 21 2186-2193... 

Manahan-Vaughan D, Braunewell KH (1999) Novelty acquisition is associated with induction of hippocampal long-term depression. Proc Natl Acad Sci U S A 96 8739-8744 Maren S (2001) Neurobiology of Pavlovian fear conditioning. Annu Rev Neimosci 24 897-931 Maren S, Holt W (2000) The hippocampus and contextual memory retrieval in Pavlovian conditioning. Behav Brain Res 110 97-108... 

This initial finding of abnormal hippocampal function during memory retrieval in schizophrenia has been clarified by several subsequent studies. First, patients with schizophrenia rely less on the recruitment of the hippocampus and show more widespread activation of the prefrontal cortex during the retrieval of previously learned information (Weiss et al., 2003). Second, the ability to classify new items as previously not experienced is impaired in schizophrenia and is associated with decreased activation and smaller volume of the hippocampus (Weiss et al., 2004). Third, hippocampal recruitment in schizophrenia is impaired specifically during a relational, but not during a nonrelational memory task (Ongur et al., 2006). 

Abnormal recruitment of the hippocampus during memory retrieval in schizophrenia. The right hippocampal region indicated in red in (a) showed increased relative cerebral blood flow (rCBF) during high accuracy recall when compared with both lexical retrieval at baseline and low accuracy recall in healthy control subjects ("controls" in (b)). This normal pattern was absent in the schizophrenia group and all three recall conditions were associated with higher rCBF in the hippocampus ("schizophrenics" in (b))... 

Scientists are only now beginning to discover why ketamine works the way it does. NDM A receptors in the human brain are densely localized in the cerebral cortex and hippocampus, areas that are important for higher functions like memory creation and retrieval. Ketamine, by blocking NDMA receptors, effectively disables the normal functioning of the hippocampus, accounting for short-term disorientation and memory loss. 

Lepage M, Habib R, Tulving E. 1998. Hippocampal PET activations of memory encoding and retrieval The HIPER model. Hippocampus 8 313-322. 

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