Figure 2

Phase contrast micrographs of central area of cortical cultures. Photographs are of three typical cultures of different densities, at 1, 15, and 32 days in vitro. Note that even our 'sparse' cultures are considerably denser than those commonly used for investigating synaptic plasticity with intracellular electrodes (see, e.g., [32]). Scale: electrode spacing is 200 μm center to center.