Stimulus Phase Locking of Cortical Oscillation for Auditory Stream Segregation in Rats

Abstract

The phase of cortical oscillations contains rich information and is valuable for encoding sound stimuli. Here we hypothesized that oscillatory phase modulation, instead of amplitude modulation, is a neural correlate of auditory streaming. Our behavioral evaluation provided compelling evidences for the first time that rats are able to organize auditory stream. Local field potentials (LFPs) were investigated in the cortical layer IV or deeper in the primary auditory cortex of anesthetized rats. In response to ABA- sequences with different inter-tone intervals and frequency differences, neurometric functions were characterized with phase locking as well as the band-specific amplitude evoked by test tones. Our results demonstrated that under large frequency differences and short inter-tone intervals, the neurometric function based on stimulus phase locking in higher frequency bands, particularly the gamma band, could better describe van Noorden’s perceptual boundary than the LFP amplitude. Furthermore, the gamma-band neurometric function showed a build-up-like effect within around 3 seconds from sequence onset. These findings suggest that phase locking and amplitude have different roles in neural computation, and support our hypothesis that temporal modulation of cortical oscillations should be considered to be neurophysiological mechanisms of auditory streaming, in addition to forward suppression, tonotopic separation, and multi-second adaptation.

High-gamma band fronto-temporal coherence as a measure of functional connectivity in speech motor control

“…Our phase analysis indicates that phase-shifts are random between both frontal and temporal areas. Phase-alignment can promote communication between brain regions or facilitate stimulus-related events (Noda et al 2013; Mercier et al 2015). In the present study, we do not observe consistent, significant phase relationships between areas.…”

Animal models for auditory streaming

“…Strong adaptation that can provide the basis for build-up was also observed in the tonotopic pattern of membrane potentials recorded using voltage sensitive dye imaging in the primary auditory cortex of the anaesthetized guinea pig [57]. Noda et al [37,62] reported rstb.royalsocietypublishing.org Phil. Trans.…”

“…These state differences between inattentive animal and attentive human subjects make comparisons difficult. Finally, human electrophysiological studies apply non-invasive techniques reflecting the response of large populations of neurons [3] whereas the animal studies rarely look at simultaneously recorded populations of neurons a time [37,57,62], nor have done so at the level of individual neurons. This so far precluded direct observation of anti-correlated neuronal response patterns as are predicted by the temporal coherence hypothesis for the formation of auditory streams [15].…”

“…Tonotopic patterns of cortical membrane potentials in the anaesthetized guinea pig also reflected the spatially separated representation of the two tone signals in ABAB and ABAtriplet paradigms showing a suppression of the response to the off-BF tones [57]. Noda et al [37] recorded local field potential (LFP) in the primary auditory cortex of anaesthetized rats and suggest that the amplitude and phase of cortical oscillatory activity, especially in the gamma band, carries important information regarding stream segregation. Already rstb.royalsocietypublishing.org Phil.…”

Speech‐in‐noise understanding in older age: The role of inhibitory cortical responses

“…The roles of gamma oscillations for precise neural timing (Buzśaki & Wang, ; Cardin et al., ; Li, Morita, Robinson, & Small, ; Nikolić, Fries, & Singer, ) and perceptual binding (Engel & Singer, ; Ross & Fujioka, ) have been discussed in recent years. Beyond sensory encoding, the auditory evoked gamma response is involved central processes of extracting the meaning of sound, such as in perceptual organization of an auditory stream (Noda, Kanzaki, & Takahashi, ). The gamma response is generated in thalamocortical networks (Llinás, Leznik, & Urbano, ; Steriade, Contreras, Amzica, & Timofeev, ), and its amplitude depends on the balance between inhibition and excitation in cortical interneurons.…”