Fig. 2.

Fezf2 mutant neurons exhibit the electrophysiological characteristics of callosal projection neurons. (a) Responses to depolarizing current injection of layer 5 neurons in brain slices from Fezf2^+/− mice at P17–P24. (b) Responses to depolarizing current injection of layer 5 neurons in slices from Fezf2^−/− mice at P17–P24. (c) Histogram plotting the number of layer 5 neurons exhibiting a given adaptation ratio. Layer 5 neurons in slices from Fezf2^+/− mice exhibit a bimodal distribution of neurons with high adaptation ratios (≥0.75) and those with low adaptation ratios (<0.75). Layer 5 neurons recorded in Fezf2^−/− mice showed a unimodal distribution, all exhibiting low adaptation ratios. (d) Representative biocytin-filled layer 5 neurons in cortical slices. Arrows point to neurons in Fezf2^+/− mice that showed spike frequency adaptation. The unmarked neurons in the Fezf2^+/− mice showed no adaptation. (Scale bar, 200 μm.)