OPTICAL MICROSCOPY .3. TRACKING FLUORESCENTLY LABELED NEURONS IN DEVELOPING BRAIN

For decades, time-lapse microscopy has been used to track dynamic even ts associated with biological phenomena. Time-lapse studies of the dev eloping nervous system have been restricted to analysis of dissociated cell cultures or of a series of static images from living organisms. The advent of new fluorescent dyes and video imaging technology has pr oduced novel views of the behavior of neurons in the context of the de veloping nervous tissue, such as migrations within and away from proli ferative zones and navigation of axonal processes to synaptic targets, After fixation of the tissue preparation, time-lapse monitoring can b e followed by other analytical techniques and forms of microscopy, e.g ., immunocytochemistry or electron microscopy, producing information o n the interactions of individual cells whose behavioral histories are known. The power of video time-lapse microscopy of living brain tissue lies in the firsthand documentation of developmental patterning, whic h in turn can serve as an experimental assay.