Forward suppression in the auditory cortex is frequency-specific

Abstract

We investigated how physiologically observed forward suppression interacts with stimulus frequency in neuronal responses in the guinea pig auditory cortex. The temporal order and frequency proximity of sounds influence both their perception and neuronal responses. Psychophysically, preceding sounds (conditioners) can make successive sounds (probes) harder to hear. These effects are larger when the two sounds are spectrally similar. Physiological forward suppression is usually maximal for conditioner tones near to a unit's characteristic frequency (CF), the frequency to which a neuron is most sensitive. However, in most physiological studies, the frequency of the probe tone and CF are identical, so the role of unit CF and probe frequency cannot be distinguished. Here, we systemically varied the frequency of the probe tone, and found that the tuning of suppression was often more closely related to the frequency of the probe tone than to the unit's CF, i.e. suppressed tuning was specific to probe frequency. This relationship was maintained for all measured gaps between the conditioner and the probe tones. However, when the probe frequency and CF were similar, CF tended to determine suppressed tuning. In addition, the bandwidth of suppression was slightly wider for off-CF probes. Changes in tuning were also reflected in the firing rate in response to probe tones, which was maximally reduced when probe and conditioner tones were matched in frequency. These data are consistent with the idea that cortical neurons receive convergent inputs with a wide range of tuning properties that can adapt independently.

Vocal sequences suppress spiking in the bat auditory cortex while evoking concomitant steady-state local field potentials

“…The finding that the spike activity of most cortical neurons does not keep up with the temporal flow of information is consistent with results from experiments conducted in other vertebrate species34415556. Of course, that suppression occurs at the cortical level does not necessarily imply that distress information is not being processed in auditory stations outside of the AC.…”

Comodulation Enhances Signal Detection via Priming of Auditory Cortical Circuits

“…This latter observation suggests that slow adaptation to temporal coherence across-frequency is necessary to implement this form of CMR. The nature of such adaptation is not known but could include cortical synaptic depression (Carandini et al, 2002; Chung et al, 2002; Freeman et al, 2002), forward suppression (Wehr and Zador, 2005; Alves-Pinto et al, 2010; Scholes et al, 2011), and/or modulation at subcortical processing stations via cortical feedback (Bajo et al, 2007; Malmierca and Ryugo, 2011). …”

“…Raw FRAs were initially smoothed using a 3 × 3 pyramidal window; iso-response curves (FRA edges) were then determined by finding a 30% change from baseline firing rate (Sutter and Schreiner, 1991; Scholes et al, 2011). Both excitatory (positive criterion) and inhibitory (negative criterion) curves were defined but processed separately.…”

Searching for the Mismatch Negativity in Primary Auditory Cortex of the Awake Monkey: Deviance Detection or Stimulus Specific Adaptation?

“…There are several reasons to remain cautious in drawing this conclusion. First, long-range spectral interactions in A1, such as forward suppression (Brosch and Schreiner, 1997; Bartlett and Wang, 2005; Scholes et al, 2011), were not considered in these theoretical models, and the potential influence of these interactions in the many standards condition remains unclear. Second, responses to deviants presented within the oddball context were generally smaller than responses to deviants when presented alone at similar inter-stimulus intervals and were not qualitatively different from those elicited by the same tones in the many standards condition.…”