Reversible activation of GABA and L-glutamate uptake into synaptosomes isolated from the rat brain in response to a single carbacholine injection into hippocampus

Memory dissociation: the approach to the study of retrieval processes

The phenomenon of dissociated memory retrieval is observed when some influences (for example, pharmacological) on the brain result in specific changes of long-term memory. The purpose of present paper is to reveal possibilities of the phenomenon for study of long-term memory retrieval. Pharmacologically-induced dissociated states could be identified when the retrieval of responses learned before treatment is temporarily blocked by the drug influence, but the ability of the animals to learn new tasks is intact. Furthermore, memory traces that were formed in drugged state are not accessible for the retrieval in normal state and only the same drug treatment allows retrieving them. In the present work, dissociated learning of food-motivated tasks was carried out in Wistar rats with cholinesterase inhibitor physostigmine (0.5 mg/kg, intraperitonealy) or general anaesthetic sodium pentobarbital (15 mg/kg, intraperitonealy.). The retrieval of dissociated responses was studied under the influence of various doses of the same drugs. The results revealed the asymmetry of memory dissociation with physostigmine in contrast to pentobarbital-induced memory dissociation. Gradual access for the retrieval of dissociated memory traces after pharmacological modulation of cholinergic and GABA-ergic brain systems was shown. It was suggested an important role of hippocampus in memory dissociation, as a structure-performing match-mismatch operations between different retrieved memory traces.

Retrieval of attention-dependent long-term memory traces

The stage of retrieving long-term memory traces is discussed; studies of this stage can be performed using the phenomenon of dissociated brain states. These states arise in response to various external influences and are accompanied by selective, reversible derangements of retrieval processes without alteration of the mechanisms involved in perceiving and fixing information. Analysis of the appearance of dissociated states induced by pharmacological treatments leads to several conclusion: a) reversible derangements affecting the retrieval function are typical of types of memory which depend on attention; b) the hippocampus plays a key role in selecting engrams for extraction from long-term memory; c) the brain's cholinergic and GABAergic mediator systems are involved in regulating the retrieval of long-term memory traces; d) stable derangements of the retrieval of long-term memory traces are accompanied by deep molecular-cellular changes in the hippocampus, including alterations in genetic elements and phosphorylation of synaptic proteins.