title: Pre-attentive, context-specific representation of fear memory in the auditory cortex of rat.
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.
authors.affiliation: Neural Computation Unit, Okinawa Institute of Science and Technology, Kunigami, Okinawa, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Funamizu
authors.forename: Ryohei
authors.initials: R
authors.lastname: Kanzaki
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Takahashi
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D001288:Attention; D001303:Auditory Cortex / Q000166:cytology / Q000502:physiology*; D001931:Brain Mapping; D003213:Conditioning, Psychological; D005239:Fear / Q000502:physiology*; D008297:Male; D008568:Memory / Q000502:physiology*; D009431:Neural Conduction; D009473:Neuronal Plasticity; D051381:Rats; D017208:Rats, Wistar; D011984:Sensory Receptor Cells / Q000502:physiology