ИСТИНА

Natural learning involves complex stimuli comprising several sensory modalities. Elemental learn-ing theories suggest that each component of a compound signal is encoded and associated sepa-rately. Configural theories predict the formation of the entire complex signal representation. We developed a mouse model of fear conditioning to a compound tone-light cue and used it to test these alternative theories. We studied the dynamics of memories for compound cue and its sepa-rate components and found that they mature over different times after conditioning. We showed that memory about components matures over different periods after training: memory about the auditory stimulus and the CCS is behaviorally manifested immediately after training, while memory about the light stimulus and the light and sound components of CCS matures within three days. We found a similar dissociation in extinction experiments. When the extinction procedure was started one day after training, the extinction of one CCS component had no effect on memory about the other CCS component. When the extinction procedure was started seven days after train-ing, the memory extinction of one component of CCS also resulted in the memory extinction of the other component. Next, we performed c-Fos imaging of cellular activity in several brain regions after conditioning to the entire compound cue or its components. We found that compound-cue and single-cue condi-tioning produced distinct patterns of cortical activation - prelimbic and frontal associative cortices were activated by conditioning to compound cue but not to single cues. We showed that only memory retrieval by the entire compound cue but not by single cues activated parietal association, primary visual, mediolateral secondary visual cortices, and hippocampal CA1. Then, we used fiber photometry for the in vivo calcium activity recording in the parietal association cortex during CCS memory formation and retrieval. We demonstrated a rapid photometry signal increase in response to CCS components, the entire compound cue, and during aversive (freezing) and exploratory (rear) behaviors. Finally, we performed in vivo two-photon imaging of retrieval-induced c-Fos ex-pression in the parietal cortex of fos-EGFP transgenic mice. We found at least three neuronal pop-ulations with different response specificity to the compound signal and its components. Our data suggest complex signals can establish integral and elemental neuronal representations. These rep-resentations have different neuronal substrates and can be used separately in behavior. This work was supported by the Non-Commercial Foundation for Support of Science and Education "INTELLECT" and RSF project # 23-78-00010.