Trace Pavlovian

Author Information

  • Title: Nucleus accumbens dopamine encodes the trace period during appetitive Pavlovian conditioning

  • Authors: Matthew J. Wanat, Erika T. Camacho, Paul E.M. Phillips

  • Affiliations:

    • Department of Neuroscience and Developmental Biology, University of Texas at San Antonio, TX, USA

    • Department of Mathematics, University of Texas at San Antonio, TX, USA

    • Department of Psychiatry & Behavioral Sciences, Department of Pharmacology, Center for Neurobiology of Addiction, Pain & Emotion, University of Washington, Seattle, WA, USA

  • Corresponding Author: Matthew J. Wanat, mbmatthew.wanat@utsa.edu

  • Contributions:

    • Experiment design: MJW & PEMP

    • Data collection: MJW

    • Data analysis: MJW and ETC

    • Manuscript writing assistance: All authors

  • Funding:

    • Supported by National Institutes of Health grants DA033386, DA042362, MH127466, and DA027858.

  • Disclosure: No conflicts of interest.

Abstract

  • Pavlovian Conditioning: Used to identify neural systems for learning cue-outcome relationships.

    • Delay Conditioning: CS overlaps with US delivery.

    • Dopamine in NAc: Regulates behavior during delay conditioning, with responses reflecting reward value.

    • Trace Conditioning: Involves a trace period between CS termination and US delivery; understudied dopamine response in these tasks.

  • Study Findings:

    • Trace Conditioning Task:

      • Employs distinct CS for short (5s) and long (55s) trace periods.

      • Rats showed greater conditioned responding and shorter latency for Short Trace CS.

    • Dopamine Response:

      • Increases on Short Trace trials, decreases on Long Trace trials.

      • US-evoked responses were greater for Long Trace.

      • The relationship between CS dopamine and latency best explained by an exponential function.

      • Overall, indicates a bidirectional NAc dopamine response related to trace periods in conditioning.

Significance Statement

  • Key Concept: Cue-outcome learning is crucial for reward-seeking behavior, driven by striatal dopamine.

  • Study Focus: Investigated dopamine response to cues during trace conditioning.

    • Findings indicate bidirectional changes in dopamine levels signal trace periods and correlate with response latency.

Introduction

  • Associative Learning: Fundamental for reward and aversive learning in Pavlovian conditioning.

  • Conditioned Stimulus (CS) predicts Unconditioned Stimulus (US).

  • Delay Conditioning: CS overlaps with US delivery; dopamine signaling aids in learning.

  • Trace Conditioning: Involves a gap between CS and US delivery; could use rewards or aversive stimuli.

  • Dopamine’s Role: Regulates behavioral responses in appetitive and aversive conditions, but unstudied in appetitive trace conditioning.

  • Experimental Design: Trained rats on trace conditioning with audio cues signaling Short and Long Trace periods before rewards.

Methods

Subjects and Surgery

  • Rats: Male Sprague-Dawley (P60-65, 300-350g), pair-housed, water and chow ad libitum, 12-hour light/dark cycle.

  • Surgery: Voltammetry electrodes implanted in NAc core (coordinates relative to bregma).

Behavioral Procedures

  • 1-week recovery post-surgery; mild food restriction (~15 g/day).

  • Training: Familiarization through non-contingent food pellet delivery; 30 trace conditioning sessions with Short and Long Trace trials in pseudorandom order.

    • Short Trace: 5s audio CS + 5s trace + food;

    • Long Trace: 5s audio CS + 55s trace + food.

Voltammetry Recordings

  • Method: Fast-scan cyclic voltammetry; electrodes monitored dopamine levels in trained rats.

  • Data Analysis: Quantified CS-evoked dopamine response & US-evoked response; included sessions meeting criteria.

Results

Behavioral Findings

  • Short Trace trials resulted in:

    • Higher conditioned responding.

    • Faster head entry latency compared to Long Trace trials.

Dopamine Response Data

  • Short Trace CS: Increased dopamine levels;

  • Long Trace CS: Decreased dopamine levels.

  • CS-evoked response varies inversely with trace period.

  • Lack of correlation between CS dopamine levels and conditioned responding.

Discussion

  • CS Dopamine Encoding: Signals trace periods; notable difference from delay conditioning where dopamine increases with reward immediacy.

  • Possible implications for how dopamine responds to delayed cues; reinforces idea of both positive and negative encoding in conditions.

  • Behavioral Outcomes: Suggest distinct conditioned responses can develop independently.

  • Limitations: Study solely on male rats; future research needed on sex differences.

  • Implications of Findings: Highlights the role of dopamine in timing-related calculations over varied timescales.