Cortical activity associated with the detection of temporal gaps in tones: a magnetoencephalography study

Abstract

We used magnetoencephalogram (MEG) in two experiments to investigate spatio-temporal profiles of brain responses to gaps in tones. Stimuli consisted of leading and trailing markers with gaps between the two markers of 0, 30, or 80 ms. Leading and trailing markers were 300 ms pure tones at 800 or 3200 Hz.Two conditions were examined: the within-frequency (WF) condition in which the leading and trailing markers had identical frequencies, and the between-frequency (BF) condition in which they had different frequencies. Using minimum norm estimates (MNE), we localized the source activations at the time of the peak response to the trailing markers. Results showed that MEG signals in response to 800 and 3200 Hz tones were localized in different regions within the auditory cortex, indicating that the frequency pathways activated by the two markers were spatially represented.The time course of regional activity (RA) was extracted from each localized region for each condition. In Experiment 1, which used a continuous tone for the WF 0-ms stimulus, the N1m amplitude for the trailing marker in the WF condition differed depending on gap duration but not tonal frequency. In contrast, N1m amplitude in BF conditions differed depending on the frequency of the trailing marker. In Experiment 2, in which the 0-ms gap stimulus in the WF condition was made from two markers and included an amplitude reduction in the middle, the amplitude in WF and BF conditions changed depending on frequency, but not gap duration.The difference in temporal characteristics betweenWF and BF conditions could be observed in the RA.

Spatiotemporal brain dynamics of auditory temporal assimilation

“…We first monitored activity in the frontal and parietal regions, as well as in the AC. Estimation was performed according to the methods used in our previous works 41 , 42 . To avoid double dipping 43 , we marked iROIs on the AC, IFG, and TPJ of both hemispheres by referencing previous studies and using the anatomical information provided by FreeSurfer software (l(r)h.aparc.annot based on Desikan-Killiany Atlas 44 ).…”

Auditory brainstem responses to silent gaps in across-channel conditions

“…As far as we know, Grose et al [6] was the only study that measured ABRs in the context of across-channel gap detection, although they used a two-tone complex marker which is not typical in gap detection research. In the present study, we used narrowband noise markers of center frequencies similar to the frequencies of pure tone markers used in studies of the first author's lab [8].…”

“…Second, ABR data should be useful for identifying, along the auditory pathway, the site responsible for differences between within-channel and across-channel gap detection. Neurophysiological studies of gap detection, particularly with human participants, have indicated that neural activities differ between the two types of gap detection at the auditory cortex or higher brain regions [4,8,9]. However, it is conceivable that differences may exist at lower stages of the auditory pathway.…”

Advances in modern mental chronometry

“…There are also studies focusing on the auditory system, including the work of Nakajima et al that investigates the foundations of time perception using a time illusion based on an overestimation of a second time interval preceded by a first time interval or time-shrinking effect (Nakajima et al, 2014 ). Mitsudo et al present recorded magnetoencephalogram signals in tasks that require to judge temporal gaps in tones and have discussed their implications in the organization of the auditory cortex (Mitsudo et al, 2014 ). Within the same time perception paradigm, Mioni et al show a detailed review on temporal dysfunctions in traumatic brain injury patients (Mioni et al, 2014 ).…”