Figure 2.

A microdrive for sharp intracellular recording in the singing bird. a, The intracellular microdrive incorporates a motor that rotates a threaded rod and advances a shuttle that holds the electrode. b, A schematic of the zebra finch brain, highlighting three cell types in HVC defined by their projections: local circuit interneurons (in black), neurons that project to RA (in red), and neurons that project to basal ganglia-homologue area X (in blue). c, Examples of intracellular records from a putative local circuit interneuron, d, a putative X-projecting neuron, and e, an antidromically-identified RA-projecting neuron. Asterisk indicates the region magnified in the panels at right.