Pre-attentive, context-specific representation of fear memory in the auditory cortex of rat

PLoS One. 2013 May 6;8(5):e63655. doi: 10.1371/journal.pone.0063655. Print 2013.

Abstract

Neural representation in the auditory cortex is rapidly modulated by both top-down attention and bottom-up stimulus properties, in order to improve perception in a given context. Learning-induced, pre-attentive, map plasticity has been also studied in the anesthetized cortex; however, little attention has been paid to rapid, context-dependent modulation. We hypothesize that context-specific learning leads to pre-attentively modulated, multiplex representation in the auditory cortex. Here, we investigate map plasticity in the auditory cortices of anesthetized rats conditioned in a context-dependent manner, such that a conditioned stimulus (CS) of a 20-kHz tone and an unconditioned stimulus (US) of a mild electrical shock were associated only under a noisy auditory context, but not in silence. After the conditioning, although no distinct plasticity was found in the tonotopic map, tone-evoked responses were more noise-resistive than pre-conditioning. Yet, the conditioned group showed a reduced spread of activation to each tone with noise, but not with silence, associated with a sharpening of frequency tuning. The encoding accuracy index of neurons showed that conditioning deteriorated the accuracy of tone-frequency representations in noisy condition at off-CS regions, but not at CS regions, suggesting that arbitrary tones around the frequency of the CS were more likely perceived as the CS in a specific context, where CS was associated with US. These results together demonstrate that learning-induced plasticity in the auditory cortex occurs in a context-dependent manner.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acoustic Stimulation
  • Animals
  • Attention*
  • Auditory Cortex / cytology
  • Auditory Cortex / physiology*
  • Brain Mapping
  • Conditioning, Psychological
  • Fear / physiology*
  • Male
  • Memory / physiology*
  • Neural Conduction
  • Neuronal Plasticity
  • Rats
  • Rats, Wistar
  • Sensory Receptor Cells / physiology

Grants and funding

This work was partially supported by KAKENHI (23135507) and SCOPE (121803022). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.