Spatiotemporal brain dynamics of auditory temporal assimilation

Abstract

Time is a fundamental dimension, but millisecond-level judgments sometimes lead to perceptual illusions. We previously introduced a “time-shrinking illusion” using a psychological paradigm that induces auditory temporal assimilation (ATA). In ATA, the duration of two successive intervals (T1 and T2), marked by three auditory stimuli, can be perceived as equal when they are not. Here, we investigate the spatiotemporal profile of human temporal judgments using magnetoencephalography (MEG). Behavioural results showed typical ATA: participants judged T1 and T2 as equal when T2 − T1 ≤ +80 ms. MEG source-localisation analysis demonstrated that regional activity differences between judgment and no-judgment conditions emerged in the temporoparietal junction (TPJ) during T2. This observation in the TPJ may indicate its involvement in the encoding process when T1 ≠ T2. Activation in the inferior frontal gyrus (IFG) was enhanced irrespective of the stimulus patterns when participants engaged in temporal judgment. Furthermore, just after the final marker, activity in the IFG was enhanced specifically for the time-shrinking pattern. This indicates that activity in the IFG is also related to the illusory perception of time-interval equality. Based on these observations, we propose neural signatures for judgments of temporal equality in the human brain.

Audio-visual combination of syllables involves time-sensitive dynamics following from fusion failure

“…Interestingly, this sensitivity did not translate into a misalignment sensation, confirming that this range of AV asynchrony is perceptually well tolerated 4 . These findings are consistent with previous studies 23,24,62 showing that the IFG is involved in implicit timing 22 , a sensitivity that allows listeners to predict word order from syntactic information 63 . Even though our brain is not aware of precise event temporality, the latter is essential to monitor e.g., articulatory and syntactic correctness, and to prepare for correct production.…”

“…Yet, the detection of shorter temporal AV asynchronies is possible and takes place in other brain regions, in particular in the dorsal premotor area and the inferior frontal gyrus [22][23][24][25] .…”

“…Although the LSTS responds better when auditory and visual speech are perfectly synchronous 18,19 , its activity can cope with large temporal discrepancies, reflecting a broad temporal window of integration in the order of the syllable length (up to ~260 ms) 20 . This large window of integration can even be pathologically stretched to about 1s in subjects suffering from autism spectrum disorder 21 .Yet, the detection of shorter temporal AV asynchronies is possible and takes place in other brain regions, in particular in the dorsal premotor area and the inferior frontal gyrus [22][23][24][25] .considering the temporal patterns in a 2 nd acoustic formant/lip aperture two-dimensional (2D) feature space is sufficient to qualitatively reproduce participants' behaviour for fused 13,29 but also combined responses 28 . Simulations indicated that fusion is possible, and even expected, when the physical features of the A and V stimulus, represented by the 2 nd formant and lip in the model, are located in the neighbourhood of an existing 2D syllable representation.…”

Motor Reproduction of Time Interval Depends on Internal Temporal Cues in the Brain: Sensorimotor Imagery in Rhythm

“…Nevertheless, the perception of time is constantly required for the everyday decisions we make, and for recognition of intervals and motion as well as auditory structured information such as speech and music ( Wittmann, 2009 ). Neurophysiological studies have revealed that there exist neural areas that contribute to the perception of time intervals although the temporal function is not the primary process of those brain regions ( Matell and Meck, 2000 ; Kagerer et al, 2002 ; Mauk and Buonomano, 2004 ; Buhusi and Meck, 2005 ; Mita et al, 2009 ; Hironaga et al, 2017 ). Previous studies have proposed hierarchical neural models of temporal processing based on distinct time scales.…”

Audio-visual combination of syllables involves time-sensitive dynamics following from fusion failure

“…This large integration window can even be pathologically stretched to about 1 s in subjects suffering from autism spectrum disorder 27 . Yet, the detection of shorter temporal AV asynchronies is possible and takes place in other brain regions, in particular in the dorsal premotor area and the inferior frontal gyrus [28][29][30][31] . The STS and the IFG regions hence exhibit different functions in AV speech integration 32,33 , owing to their different temporal integration properties 34 .…”