New paper published

Recurrent cortical processing describes the mechanism in the cortical microcircuits that amplifies cortical input to allows its further propagation within the cortical circuits (within and between cortical areas). Given that forward cortical connectivity comprises only ca.10% of all cortical synapses (including the inhibitory ones), recurrent processing is key for preserving the activity in highly divergent cortical networks.

The connections between supragranular and infragranular layers further allow the integration of bottom-up and top-down streams of information. The aim of these is the embeeding of sensory input into the internal model of environment and previous experiences made.

In the recent study we quantified connectivity within cortical microcircuits of the auditory cortex using “spike-field” coherence of neuronal activity in hearing and congenitally deaf cats recorded with multielectrode arrays. Cochlear implants were used to probe this connectivity. We found an extensive functional connectivity deficit in deep (infragranular) layers and between superficial (supragranular) and deep layers. As in a previous study (Yusuf et al., 2021), interareal cortical connectivty was additionally compromised.

These data explain why therapy of inborn deafness needs to take place within an early critical period, since this deficits compromises the propagation of cortical activity to other areas and prevents an integration of top-down and bottom-up signal streams and thus the embedding of the sensory input into previous experiences, i.e. sensory priors. These allow the brain to cope with degraded sensory inputs (as in noisy environment or with cochlear implants).

The paper is a result of a collaboration with the labs of

Prof. Martin Vinck, E. Strüngmann Institute for Neuroscience, Frankfurt am Main

Dr. Prasandhya A. Yusuf, University of Indonesia at Jakarta

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Download a related 2021 paper on deficits in interareal top-down connectivity in deafness