Forward masking in the superior paraolivary nucleus of the rat

Abstract

In natural acoustic environments, perception of acoustic stimuli depends on the recent contextual history. Forward masking describes a phenomenon whereby the detection threshold of a probe stimulus is markedly increased when it is preceded by a masking stimulus. The aim of this study was to characterize the offset response of single units in the superior paraolivary nucleus (SPON) to a forward masking paradigm. We observed two distinct response types to forward masked stimuli, namely inhibited and facilitated responses. In the presence of a default masking stimulus, inhibited responses to probe stimuli were characterized by elevated thresholds and/or diminished spike counts, whereas facilitated responses were characterized by reduced thresholds and increased spike counts. In units with inhibited responses to the probe stimuli, probe thresholds increased and spike counts decreased as masker intensity was raised or the masker-to-probe delay was shortened. Conversely, in units with facilitated responses to the probe stimuli, probe thresholds decreased and spike counts increased as masker intensity was raised or the masker-to-probe delay was shortened. Neither inhibited nor facilitated responses to the forward masking paradigm were significantly dependent on masker frequency. These findings suggest that SPON responses are not themselves consistently subject to the same forward masking properties observed in other nuclei along the ascending auditory pathway. The potential neural mechanisms of the forward masking responses observed in the SPON are discussed.

Nonuniform impacts of forward suppression on neural responses to preferred stimuli and nonpreferred stimuli in the rat auditory cortex

“…The inhibitory conductance could contribute to the short lasting (<100 ms after the masker onset) suppressive effect. Moreover, the forward suppression lasted less than 100 ms could also be inherited from subcortical nuclei, such as brainstem (Gao & Berrebi, ; Gao et al., ) and inferior colliculus (Nelson et al., ; Wehr & Zador, ). For the long‐lasting (>100 ms) forward suppressive effect shown in the present study, the forward suppression could also be generated by presynaptic depression at thalamocortical or intracortical synapses (Wehr & Zador, ).…”

“…This forward masking effect has been demonstrated in auditory brainstem (Gao & Berrebi, ; Gao, Kadner, Felix, Chen, & Berrebi, ), inferior colliculus (Nelson, Smith, & Young, ) and auditory cortex (Brosch & Schreiner, ; Calford & Semple, ; Peng, Sun, & Zhang, ; Peng, Xing, He, Sun, & Zhang, ; Reale & Brugge, ; Zhang, Nakamoto, & Kitzes, ; Zhang et al., ). The impacts of a forward masker on the neural responses to a probe depend on the level, frequency and duration of the masker (Brosch & Schreiner, ; Furukawa & Middlebrooks, ; Nelson et al., ; Reale & Brugge, ; Zhang et al., , ; Zhou & Wang, ) as well as the time interval between masker and probe (Brosch & Schreiner, ; Gao & Berrebi, ; Gao et al., ; Jiang, Xu, Yu, Xu, & Zhang, ; Nakamoto, Zhang, & Kitzes, ; Peng et al., , ; Zhao, Xu, He, Xu, & Zhang, ). A precedence effect was also evident in the neural responses in the inferior colliculus (Litovsky & Yin, ) and auditory cortex (Mickey & Middlebrooks, ) when two separated sounds were presented with a brief delay.…”

Auditory Forward Masking Explained by a Subcortical Model with Efferent Control of Cochlear Gain

“…Several studies have considered the possibility that probe suppression in the IC arises from the brainstem’s superior paraolivary nucleus (SPON; Nelson et al, 2009; Felix et al, 2015; Gai, 2016; Gao and Berrebi, 2016; Gao et al, 2017; Salimi et al, 2017). However, chemical inactivation of the SPON does not remove suppression of probe responses for onset neurons, which demonstrate GOM similar to that in psychophysics (Felix et al, 2015, their Fig.…”

Processing of Paired Click-Tone Stimulation in the Mice Inferior Colliculus

“…Temporal separation of two sounds in a pair could affect the perceptual grouping causing the auditory stream segregation (Bregman, 1990) as well as determine the response to the second sound, i.e., forward masking/suppression (Calford and Semple, 1995; Moore, 1995; Brosch and Schreiner, 1997; Wehr and Zador, 2005). Forward masking has been widely studied in the neuronal auditory pathway including the auditory nerve (Delgutte, 1980), the medial nucleus of the trapezoid body (Gao and Berrebi, 2016), the superior paraolivary nucleus (Gao et al, 2017), the inferior colliculus (IC) (Nelson et al, 2009) and the auditory cortex (Wehr and Zador, 2005). The suppression of neuronal response to the second sound in a pair increases as the temporal sound separation (from the offset of the first sound to the onset of the second one) decreases (Wehr and Zador, 2005; Gao and Berrebi, 2016).…”

“…Although forward masking is found in many nuclei (Delgutte, 1980; Wehr and Zador, 2005; Nelson et al, 2009; Gao and Berrebi, 2016; Gao et al, 2017), we focused on the IC in this study considering its integrative function as a synaptic relay station for acoustic information in the neuronal auditory pathway (Malmierca and Hackett, 2010). Paired stimuli comprising of identical sounds are not suitable for identifying the sound processing, especially when they are applied closely, because of the superimposition and/or distortion.…”