AUDITORY CORTICAL-NEURONS IN-VITRO - CELL-CULTURE AND MULTICHANNEL EXTRACELLULAR RECORDING

Self organization, pattern generation, and pattern processing in local cortical circuits are difficult to study in vivo. The complexities of cortical circuits require simplified systems for study. We have devel oped a simplified model of auditory cortical neurons growing as monola yer networks in culture. Neurons dissociated from auditory cortex of 1 4-day mouse embryos were grown on photoetched microelectrode array con taining 64 transparent indium-tin oxide electrodes. Cultures were main tained in incubators for up To 113 days. Neurons developed processes a nd made synaptic connections. All cultures were spontaneously active a nd exhibited complex temporal burst patterns. In a data set of 12 cult ures, the number of active channels varied from culture to culture and ranged from 6-17. Signal/noise ratios ranged from 3:1 to a maximum of 16:1. No significant correlations were found between age of the cultu re and number of active channels, or signal/noise ratios. Spontaneous firing patterns recorded from various channels showed complex bursting patterns in ail cultures. Within a culture, coordinated synchronous b ursting were found among some channels, and independent bursting on ot hers. Preliminary histological analysis of cultures using the Loots-mo dified Bodian stain showed neurons with axonal and dendritic profiles growing extensively on top of the glial carpet. Neuronal processes cro ssing the electrodes singly or in small groups were also observed. Pyr amidal and non-pyramidal cells could be identified. In a pool of 2,093 neurons ina 49-day-old culture, the average size of the somata was fo und to be 16 mu m, with a mode of 12 mu m.