Forward suppression in the auditory cortex is frequency-specific.
Bottom Line: The temporal order and frequency proximity of sounds influence both their perception and neuronal responses.These effects are larger when the two sounds are spectrally similar.These data are consistent with the idea that cortical neurons receive convergent inputs with a wide range of tuning properties that can adapt independently.
Affiliation: MRC Institute of Hearing Research, University Park, Nottingham NG7 2RD, UK.Show MeSH
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Mentions: To examine the effect of matched and mismatched conditioner and probe frequencies, we computed a SI that has been used previously to examine the frequency specificity of adaptation (Ulanovsky et al., 2003, 2004; Malmierca et al., 2009; Anderson et al., 2009; see Materials and methods). Figure 8A, in a plot analogous to those in previous studies, shows the SIs calculated for all probe pairs in which there was a significant response to both probes (at the ISIs indicated). An SI value of greater than zero indicates that the probe was more suppressed by a conditioner at the same matched frequency than by a conditioner at the frequency of the other probe. As there are two probes, there are two SIs. Points lying above the diagonal indicate some bias in favour of matching probes and conditioners. At all delays the population showed a significant number of pairs that were frequency specific (sign test for points lying above the diagonal: P < 0.01 at all ISIs). Note also that there are more conditions for which SIP1> SIP2 (68% overall; sign tests: P < 0.05 for 0-ms and 100-ms ISIs, P = 0.13 at 200-ms ISI). Because probes were often not symmetrically placed around the unit CF, P1 was always assigned to the probe tone frequency nearest CF. Thus, the bias towards positive values of SIP1 indicates that the differential suppression is biased towards probes near to CF. This suggests that although suppression is frequency specific, there is still an effect of CF. Figure 8B shows the summary SI values calculated for each unit, obtained by considering all pair combinations in a unit (see Materials and methods) at a given ISI. Positive values indicate that a unit was on average frequency specific. It shows that the majority of units were frequency specific (sign test: P < 0.01 at all delays).
Affiliation: MRC Institute of Hearing Research, University Park, Nottingham NG7 2RD, UK.