ИСТИНА

Though memories are hypothesized to be encoded by sparse neuronal populations, little is known about consistency of activation of such cell assemblies during memory encoding, retrieval and reconsolidation. An essential question is how similar are these activations during memory encoding and subsequent episodes of retrieval. The present experiments investigated neuronal activity in the mouse associative cortex during auditory fear conditioning and following memory recall to conditioned sound. We used transgenic mice in which the expression of enhanced green fluorescent protein (EGFP) was under the control of c-fos immediate early gene promoter for two-photon visualization of activated neurons in the cortex of awake mouse. We compared populations of activated neurons before learning, after learning and after memory retrieval in the same area of parietal associative cortex. The biggest proportion of identified neurons was activated during all three conditions (65%). Most neurons, which were not active before learning, but were activated during learning, were also activated during memory retrieval (16% of all identified neurons). The small parts of identified neurons were activated only during learning or memory recall (7% or 5%). Thus our results indicate that the main part of neuronal population in the mouse parietal associative cortex that was transcriptionally activated, as imaged by c-fos induction during fear memory encoding, is then reactivated during cue-induced memory retrieval. Supported by RSCF #14-15-00685