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
Related in: MedlinePlus
Mentions: Spearman's Rho correlation coefficients were calculated for each probe tone condition, from all conditioner–probe combinations in a given probe condition. Probe conditions were then grouped as before depending on the distance from CF or the level of the probe tone. The majority (80%; filled bars) of probe conditions showed a significant effect of discharge history although the range of values was large, consistent with previous reports (Zhang et al., 2005). Figure 9A shows differences in the correlation coefficients when the probe conditions are grouped depending on the distance of the probe from CF. Correlation coefficients were slightly lower for probes that were over 0.5 octaves from the CF (mean: −0.41) than for probe tone frequencies that were within 0.5 octaves of CF (mean: −0.51), and a slightly larger percentage of probe conditions resulted in significant correlations (85%; filled bars) when the probe is close to CF compared with away from it (75%). This trend was consistent with the dependence of tuning on probe frequency, because as probes move away from CF the difference between RF tuning and SRF tuning increases. A larger difference in correlation coefficients is observed when the probe conditions are grouped based on probe level. Figure 9B shows that correlation coefficients are generally larger when the probe level is above the 0.4 criterion threshold (mean: −0.55) than when it is below (mean: −0.29). Also, there are a larger percentage of probe conditions that result in significant correlations when the probe level is above (95%) than when it is below the 0.4 criterion threshold (70%). Thus, the responses to lower level probe tones are overall less related to response history than those that are well within the RF. This is consistent with lower level probes being suppressed by a wider range of stimuli, outside of the unit RF.
Affiliation: MRC Institute of Hearing Research, University Park, Nottingham NG7 2RD, UK.