Figure 2.

Phasic firing during the sensory learning period depends on sex and experience. A, Diagram of FR paradigm. The family is placed in acoustic isolation and the father removed 1–5 d after the first egg hatches. The mother is removed ∼P40 and the male and female chicks are separated. Male chicks raised in this condition produce abnormal (isolate) song. B, Examples of responses to step currents obtained from FR chicks (P20 and P32), as shown in Figure 1, C and D. Scale bars, 500 ms and 40 mV. C, Average response duration as a function of age in FR (yellow) and CR (black) animals. The format of the plot is as in Figure 1E. For visual clarity, data points for individual neurons are only shown for female-reared birds. Numerals indicate the number of FR birds. Between P30–P35, response duration is lower (more phasic) in CR versus FR birds (p < 0.001). Among FR birds, average response duration at P18–P20 is greater (less phasic) than at P65–P70 (p = 0.04) and in adults (p = 0.002). D, Estimated proportion of phasic neurons. Phasic neurons are more prevalent in CR versus FR animals at P30–P35 (p < 0.001), and among FR animals, more prevalent in adults than at P18–P20 (p = 0.026). E, Average response duration as a function of age and sex in CR animals. Responses are more phasic in males compared with females between P30–P35 (p = 0.004). F, Proportion of phasic neurons as a function of age and sex. The apparent difference between males and females at P30–P35 is not statistically significant (p = 0.16).