Epilepsy and state specific memory

The concept of state specific memory the idea that events experienced in a particular state of mind or brain are best remembered in that state has been a topic of lasting interest in psychology. Much of this interest has stemmed from the belief, shared by many investigators throughout this century, that the concept may figure prominently in a variety of clinical or pathological forms of memory failure. For instance, Breuer & Freud (l), in their pioneering work ”Studies on hysteria”, proposed that hysteric patients have no conscious recollection of the traumatic incident that triggered the onset of their illness. Whereas Freud hypothesised that traumatic amnesia occurs because the hysteric does not want to remember the precipitating trauma, Breuer argued that the patient cannot remember it, because the incident ”emerged and was endowed with affect in states in respect of which there is amnesia in waking consciousness” (p 214). An argument analogous to Breuer’s has recently been advanced by Reus and co-workers (2) in connection with severe depression. By their account, the difficulty many depressed patients have in remembering past periods of well being may be due not to a dynamic process of denial, but rather, to a profound alteration of affective state. Within recent years, the concept of state specific memory has also been implicated in such diverse disorders as alcoholism (3), hyperactivity (4) and multiple personality (5). Epilepsy is, without doubt, a disorder of great clinical significance, and it may be one in which the concept of state specific memory plays a particularly important part. To clarify, consider the fact that in North America, children who have even a single seizure routinely receive drug therapy for two or three years, so that they acquire important items of information in a state very different from the one that existed before epilepsy struck, and before anticonvulsant medication was started (6). If the disease takes a benign course, so that it becomes possible to discontinue drug therapy, then we are confronted with a classic state specificity paradigm, in addition to a host of hard questions. For example, does epilepsy interfere with the expression of knowledge that had been acquired prior to the onset of the disease, and does the withdrawal of drug therapy impair the retrieval of events that had been encoded in the drug state? Also, do anticonvulsant drugs differ in their propensity for producing state specific effects, and are these effects more likely to emerge with certain types of memory materials or tasks than with certain other types? And what, if anything, can be done to promote the transfer of information from one state to another? These are the kinds of questions I want to address in this article. In order to do so, I will start by summarising some recent developments in basic research on state specific memory, with a view to identifying four of its chief characteristics or properties. Although I will focus my review on the state specific effects of drugs on human memory, allied research involving animals will also be considered, as will certain nonpharmacological manifestations of state specificity that may have clinical significance in the context of epilepsy.