Cortical circuit processing of FM tones during auditory learning

The primary auditory cortex (AI) plays a fundamental role in auditory processing, perception and learning. During auditory learning, the spectrotemporal complexity of the acoustic stimuli determines the degree to which learning depends on the auditory cortex. Frequency-modulated (FM) components are essential for animal communication and, in contrast to pure tone detection, it has been shown that their discrimination is cortex-dependent. Therefore, we investigated the role of AI in the discrimination of FM-tones during a two-way avoidance shuttle-box training in Mongolian gerbils (Meriones unguiculatus). Our experimental design consisted of five different phases, in which the contingency (Go/NoGo) of FM sweeps in lower 1-2 kHz and higher 2-4kHz frequency bands is varied multiple times. During this period, the choice-outcome variations force the animals to change their behavioral strategy several times. Simultaneously, we performed local field potential (LFP) recordings across all cortical layers of the AI with a chronically implanted multichannel electrode. We used this data to analyze synaptic spatiotemporal activation patterns by current-source-density (CSD) distributions during all training phases. We hypothesize that layer-specific cortical circuit mechanisms correlate with the auditory-guided choice behavior and the strategy adaptation of the animals