The relationship between episodic memory and context: clues from memory errors made while under stress.

In a series of studies in the late 1950s and early 1960s, Jan Bures introduced cortical spreading depression to the field of behavioral neuroscience (eg. Bures 1960). This technique offered a unique way to study the role of cortex in learning and memory, and attracted the attention of many who began their graduate studies at that time, including one of us (LN, cf. Nadel 1966). An NIH postdoctoral fellowship to study with the master himself brought LN to Prague in September 1967. Thus began a relationship that included science, politics, and personal life, and has lasted over 30 years. The first scientific exchange began with Jan pulling a piece of paper from his desk with a long list of possible experiments written on it -“pick one”, he said. This led to a series of studies on interhemispheric transfer of learning under conditions of monocular input, demonstrating, amongst other things, that such transfer is not a uniform process. Depending on the kind of trials given with both hemispheres intact, and the eye which remained open to input, transfer can either be nonspecific, likely involving some kind of procedural knowledge, or highly specific, likely involving knowledge about the trained discrimination itself (Nadel and Buresova, 1970). These studies anticipated LN’s future work on multiple memory systems, a research enterprise pursued in the following decades by many labs (including LN’s: e.g. Nadel and O’Keefe 1974, O’Keefe et al. 1975). In this paper we focus on several scientific issues that Jan has been thinking about for the past 25 years. In particular, we consider spatial learning, the hippocampus, and memory. To this mix we add stress, something well known to anyone living in Prague in 1968. LN left Prague after the 1968 invasion and stayed in London for seven months, during which time arrangements were made for an eventual return to the Medical Research Council Cerebral Functions Research Group in 1970. Thus it was that LN happened to be down the hall when John O’Keefe and Jonathan Dostrovsky discovered place cells (O’Keefe and Dostrovsky 1971) and began the program of research leading to the cognitive map theory of hippocampal function (O’Keefe and Nadel 1978).