Objectives: 

The availability of analytical tools and of advanced electrophysiological techniques, susceptible of being applied in behaving animals during the acquisition of different learning paradigms, have largely facilitated the study of learning and decisions as functional states of cerebral cortical circuits. The aim was to revisit the hypothesis that each synapse in those cortical circuits contributes in a specific and precise way to the acquisition and storage of different types of associative learning tasks.

Materials: 

In this study, we have recorded activity-dependent changes in synaptic strength in different synapses at the hippocampal and prefrontal circuits during the acquisition and storage of associative learning tasks in alert behaving animals (mostly in mice, but also in rats and rabbits during classical and instrumental conditioning paradigms). In this regard, we have developed mathematical tools allowing the formulation of the multisynaptic state functions underlying every stage of acquisition and storage processes across learning.

Results: 

The exhaustive analysis of the collected data indicates that many synaptic sites within cortical circuits modulate their synaptic strength across the successive stages of acquisition of associative learning tasks. The main output of this study is that learning is the result of the activity of wide cortical and subcortical circuits activating particular functional properties of involved synaptic nodes, and that we can quantify that activation pattern by means of state and weight functions.

Conclusions: 

We expect that a map of state functions relating the acquisition of new motor and cognitive abilities and the underlying synaptic plastic changes will be offered in the near future for different types of learning tasks. This optimized approach could also be applied to the selective stimulation of relevant synaptic nodes across the involved circuits.