To verify that cue responsiveness did not result
from conditioned oro-motor responses, we performed multiple Roxadustat mw control analyses. First, we computed the power spectrum of the firing of cue-responsive neurons. Somatosensory neurons driven by oro-motor behaviors were identified on the basis of a known spectral signature (Katz et al., 2001): a characteristic peak in the 6–9 Hz band (the frequency of licking) in their firing frequency (Figure 3A, insets). Only 25.6% (20 of 78) of cue-responsive neurons were rhythmically modulated by oro-motor behaviors (black rectangles in the “Som”-labeled strip plot in right portion of Figure 3A). These neurons responded to the tone with a significantly (p < 0.05) longer latency (90 ± 15 ms, n = 16) than those without the somatosensory selleck screening library spectral signature
(50 ± 5 ms, n = 56). Because this method does not allow for the identification of potential somatosensory neurons that would not show rhythmic responses, a second analysis was performed on high-speed video recordings of the oro-facial region. To determine whether cue responses in neurons without somatosensory rhythmic signature preceded, or followed, mouth movements, the latency of the earliest detectable movement was determined with visual and automated methods in random subsets of sessions (Figures S3 and S7). The average latency of the earliest minimal mouth movements was significantly longer than that of tone-responsive neurons that did not have the rhythmic signature (automated methods: 187 ± 27 ms, p < 0.01, n = 10; blind visual inspection: 248 ± 29 ms, p < 0.01, n = 5). A session-by-session comparison of neural response and mouth movement latencies triggered by the cue confirmed that responses to cues systematically precede oral movements (Figure S3). This result is further confirmed by the inspection of population PSTHs in response to the earliest mouth movements (Figure S3), which shows a premovement ramp in firing
rates. Thus, a relatively large percentage of recorded GC neurons (19.6%, 58 of 298) produce responses to auditory tones that are not secondary to conditioned oral movements. Figures 3B and 3C show population PSTHs and representative examples of cue responses in nonrhythmic neurons. To determine 4-Aminobutyrate aminotransferase whether cue responses depended on learning, we quantified the number of neurons activated by the tone in six naive rats. In the first session in which the tone was introduced, only 1 out of 36 neurons recorded produced a nonsomatosensory tone response (2.8% versus 19.5% after training; p < 0.05) with a long latency (99 ms), suggesting that a high incidence of short latency cue-evoked activity could depend on learning and relate to the anticipatory value of the tone (Kerfoot et al., 2007). If the responses described above are truly anticipatory, they should result from top-down influences.