In vitro reconstruction of visual information-processing system using co-cultured retina and superior colliculus
Retinotectal projection, together with the well-known retinogeniculocortical pathways, plays important roles in visual information processing. In this study, we try in vitro reconstruction of retina-superior-colliculus (SC) pathways on micro- electrode arrays (MEAs). First, retinal tissue and SC slices were prepared from newborn rats and individually cultured on MEA substrates. Spontaneous electrical activity was recorded in both retina and SC cultures. Continuous firing was observed in cultured retina, where the frequency increased from a few Hz to more than 10 Hz with culture duration. Evoked responses were also recorded from cultured retinal tissue. A single biphasic pulse successfully elicited spike trains. Spontaneous activity of SC was observed in the 6 days in vitro (DIV) cultures. Finally, retina and SC were co-cultured under the conditions established for SC-slice cultures. Within a few days, we could observe neurite outgrowth from both tissue and connections were established morphologically. Spontaneous activity was recorded from both retina and SC areas in 11 DIV cultures. The next step will be spatio-temporal analysis of signal-propagation patterns of spontaneous activity as well as SC responses to retinal stimulation.