Short-latency discriminative unit response: Engram or bias?

Abstract

Recent studies have shown changes during conditioning in CS-related neuronal activity. The changes were associative in character, similar to behavioral changes which result from conditioning. However, unlike behavioral conditioned responses, the neuronal responses had very short latencies (5-35 msec). In the present paper, two hypotheses accounting for the short-latency associative activity are examined. One hypothesis assumes acquisition of a neuronal modification (engram) in the vicinity of the recording electrode. The second hypothesis postulates a tonic flow of impulses originating from a distant neural locus, which biases the activity of the recorded neurons to produce the associative response. Implications of each viewpoint are examined and the greater appeal of the bias hypothesis is asserted, based upon certain implausible implications of the engram hypothesis. Recently obtained data are presented which favor the bias hypothesis over the engram hypothesis for one CNS locality. © 1976, Psychonomic Society, Inc.. All rights reserved.