Fig. 4.

Photomicrographs of Nissl-stained coronal sections of primary auditory area (A1) in the Risso's dolphin (A), striped dolphin (B), and bottlenose dolphin (C). Scale bar indicates 300µm (A–C). Schematic drawings represent Golgi-impregnated neurons of layers II, III, and V in A1 of the Risso's dolphin (D), striped dolphin (E) and bottlenose dolphin (F). Scale bar indicates 100µm (D–F). I: layer I; II: layer II; III: layer III consisted of the three discrete sublayers IIIa, IIIb and IIIc; V: layer V; VI: layer VI; WM: white matter.