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

MALE zebra finches sing, whereas female zebra finches do not. To elucidate the neural mechanisms underlying sexual dimorphism in song behavior, the sp atio-temporal properties of neural activity in the vocal motor pathway of t he 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 20ms neural activities in the robust nucleus o f the archistriatum (RA) of both male and female finches, although the ampl itude was smaller and the latency was greater in females than in males. Bic uculline, a GABAA receptor antagonist, induced a robust activity in female RA, but had little effect in males. This suggests that neural connections f rom HVC to RA in female zebra finches are inhibited by GABAergic inputs. Th e results provide first evidence that an inhibitory neurotransmitter is inv olved in the sex difference in the motor vocal pathway of song birds. Neuro Report 10:2487-2491 (C) 1999 Lippincott Williams & Wilkins.