Sex differences in the vocal motor pathway of the zebra finch revealed by real-time optical imaging technique.

Abstract

Male zebra finches sing, whereas female zebra finches do not. To elucidate the neural mechanisms underlying sexual dimorphism in song behavior, the spatio-temporal properties of neural activity in the vocal motor pathway of the zebra finch were examined in sliced brain preparations using a real-time optical recording technique. Electrical stimulation to higher vocal center (HVC) fibers induced within 20 ms neural activities in the robust nucleus of the archistriatum (RA) of both male and female finches, although the amplitude was smaller and the latency was greater in females than in males. Bicuculline, a GABA(A) receptor antagonist, induced a robust activity in female RA, but had little effect in males. This suggests that neural connections from HVC to RA in female zebra finches are inhibited by GABAergic inputs. The results provide first evidence that an inhibitory neurotransmitter is involved in the sex difference in the motor vocal pathway of song birds.