Congenital auditory deprivation reduces synaptic activity within the auditory cortex in a layer-specific manner

The present study investigates the functional deficits of naive auditory co rtices in adult congenitally deaf cats. For this purpose, their auditory sy stem was stimulated electrically using cochlear implants. Synaptic currents in cortical layers were revealed using current source density analyses. Th ey were compared with synaptic currents found in electrically stimulated he aring cats. The naive auditory cortex showed significant deficits in synapt ic activity in infragranular cortical layers. Furthermore, there was also a deficit of synaptic activities at longer latencies (>30 ms). The 'cortical column' was not activated in the well-defined sequence found in normal hea ring cats. These results demonstrate functional deficits as a consequence o f congenital auditory deprivation. Similar deficits are likely in congenita lly deaf children.