Between-session memory degradation accounts for within-session changes in fixed-interval performance

Carter W. Daniels, Paula F. Overby, Federico Sanabria

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


A common assumption in the study of fixed-interval (FI) timing is that FI performance is largely stable within sessions, once it is stable between sessions. Within-session changes in FI performance were examined in published data (Daniels and Sanabria, 2017), wherein some rats were trained on a FI 30-s schedule of food reinforcement (FI30) and others on a FI 90-s schedule (FI90). Following stability, FI90 rats were pre-fed for five sessions. Response rates declined as a function of trial, due more to latency lengthening than to run-rate reduction. Latencies were best described by a dynamic gamma-exponential mixture distribution, in which latency lengthening was driven by the growth of the criterion pulse count for a response and not by a reduction in the speed of an endogenous clock. The speed of the clock was selectively sensitive to the length of the FI; the prevalence and length of exponentially-distributed latencies were selectively sensitive to pre-feeding. These findings reveal (a) that parameters governing FI latencies are selectively sensitive to a range of manipulations, (b) a potential degradation of the criterion pulse count between consecutive sessions, and (c) a subsequent recovery of the criterion pulse count within sessions.

Original languageEnglish (US)
Pages (from-to)31-39
Number of pages9
JournalBehavioural processes
StatePublished - Aug 2018


  • Computational modeling
  • Fixed-interval schedule of reinforcement
  • Interval timing
  • Rats
  • Response threshold
  • Within-session

ASJC Scopus subject areas

  • Animal Science and Zoology
  • Behavioral Neuroscience


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