An analysis of current source density profiles activated by local stimulation in the mouse auditory cortex in vitro

Abstract

To examine microcircuit properties of the mouse auditory cortex (AC) in vitro, we extracellularly recorded spatiotemporal laminar profiles driven by short electric microstimulation on a planar multielectrode array (MEA) substrate. The recorded local field potentials (LFPs) were subsequently evaluated using current source density (CSD) analysis to identify sources and sinks. Current sinks are thought to be an indicator of net synaptic current in a small volume of cortex surrounding the recording site. Thus, CSD analysis combined with MEAs enabled us to compare mean synaptic activity in response to current stimuli on a layer-bylayer basis. Here, we used senescence-accelerated mice (SAM), some strains of which show age-related hearing loss, to examine characteristic spatiotemporal CSD patterns stimulated by electrodes in specific cortical layers. Thus, the CSD patterns were classified into several clusters based on the stimulation sites in the cortical layers. We also found, in a reduced space obtained by principle component analysis, some CSD pattern differences between the two SAM strains in terms of aging and stimulation layers. Finally, on the basis of these results, we discuss the effects of aging on AC microcircuit properties.