Table 1.

Quantification of the degree of neural and behavioral variation

MeasureMean ± SD
CV
    Spike number, single units0.46 ± 0.23 (across recording sites and syllables)
    Spike number, multiunits0.60 ± 0.21
    Pitch0.053 ± 0.052 (across syllables)
    Amplitude0.056 ± 0.026
    Entropy0.22 ± 0.14
Fano factor
    Spike number, single units0.66 ± 0.55
    Spike number, multiunits0.98 ± 0.41
  • Measures of spiking variation were calculated from the distribution of spike counts in the 40 ms premotor window. A separate CV (SD/mean) and Fano factor (variance/mean) were computed for each case in which a unit was active (mean rate, ≥25 Hz) (see Materials and Methods) before a syllable (n = 705 cases, mean ± SD of each distribution is reported). Measures of behavioral variation were calculated by pooling measurements of pitch, amplitude, or entropy from all recorded renditions of each syllable (n = 83 syllables).