EEG alpha power predicts the temporal sensitivity of multisensory perception.

Pre-stimulus electroencephalogram (EEG) oscillations, especially in the alpha range (8-13 Hz), can affect the sensitivity to temporal lags between modalities in multisensory perception. The effects of alpha power are often explained in terms of alpha's inhibitory functions, whereas effects of alpha frequency have bolstered theories of discrete perceptual cycles, where the length of a cycle, or window of integration, is determined by alpha frequency. Such studies typically employ visual detection paradigms with near-threshold or even illusory stimuli. It is unclear whether such results generalize to above-threshold stimuli. Here, we recorded EEG, while measuring temporal discrimination sensitivity in a temporal-order judgement task using above-threshold auditory and visual stimuli. We tested whether the power and instantaneous frequency of pre-stimulus oscillations predict audiovisual temporal discrimination sensitivity on a trial-by-trial basis. By applying a jackknife procedure to link single-trial pre-stimulus oscillatory power and instantaneous frequency to psychometric measures, we identified a posterior cluster where lower alpha power was associated with higher temporal sensitivity of audiovisual discrimination. No statistically significant relationship between instantaneous alpha frequency and temporal sensitivity was found. These results suggest that temporal sensitivity for above-threshold multisensory stimuli fluctuates from moment to moment and is indexed by modulations in alpha power.

Mindfulness Meditation Biases Visual Temporal Order Discrimination but Not Under Conditions of Temporal Ventriloquism.

This study examined how cognitive plasticity acquired from a long (8 weeks) course of mindfulness training can modulate the perceptual processing of temporal order judgment (TOJ) on a sub-second scale. Observers carried out a TOJ on two visual disks, with or without concurrent paired beeps. A temporal ventriloquism paradigm was used in which the sound beeps either were synchronized with the two disks or bracketed the visual stimuli by leading the first disk by 50 ms and lagging the other by 50 ms. A left-to-right bias in TOJ was found under the visual-only condition after mindfulness training. This bias was positively correlated with "acting with awareness," a factor in the Five Facet Mindfulness Questionnaire, showing that awareness of every moment and enhanced attention focus magnify the left-to-right bias. However, the effect of mindfulness training may be short-lived and was not present when attention was diverted by auditory events in the cross-modal temporal ventriloquism illusion.

Temporal order of musical keys and subjective estimates of time.

The aim of this study was to observe the influence of the temporal order of musical keys involved in sudden modulations, which implies compositional developments in clockwise and counterclockwise directions of the circle of fifths, on subjective time estimations. Seventy-five undergraduate students from Universidade de Ribeirão Preto participated in this experiment, which consisted of listening to a modulating musical stimulus and retrospectively reproducing the duration with the aid of a stopwatch. The results showed that reverse sudden tonal modulation in the counterclockwise direction or, for instance, the temporal order from the original key of A-major to the arrival at the destination key of C-major, elicited shorter time estimations than the clockwise direction or, for instance, the temporal order from original key of C-major to the arrival at the destination key of A-major. These data were interpreted using the Expected Development Fraction model that describes the development of expectations when an inter-key distance is traversed during a certain time interval. This expected development is longer than the perceived duration, leading to the underestimation of time.

Temporal boundary of auditory event formation: An electrophysiological marker.

The formation of auditory events requires integration between successive sounds. There is a temporal limit below which a single sound event is perceived while above which a second perceptual event is formed. Behavioral studies applying the Temporal Order Judgment paradigm showed that this boundary is between 20 and 70 ms. Here we provide event-related potential (ERP) evidence from two experiments showing a qualitative change in the processing of tone pairs between 25 and 75 ms within-pair inter-stimulus intervals (ISI). We also show that this temporal boundary can be influenced by the immediate acoustical context, the statistical distribution of the ISIs within the sequence of tone-pairs.

Neural correlates of audiovisual temporal processing--comparison of temporal order and simultaneity judgments.

Multisensory integration is one of the essential features of perception. Though the processing of spatial information is an important clue to understand its mechanisms, a complete knowledge cannot be achieved without taking into account the processing of temporal information. Simultaneity judgments (SJs) and temporal order judgments (TOJs) are the two most widely used procedures for explicit estimation of temporal relations between sensory stimuli. Behavioral studies suggest that both tasks recruit different sets of cognitive operations. On the other hand, empirical evidence related to their neuronal underpinnings is still scarce, especially with regard to multisensory stimulation. The aim of the current fMRI study was to explore neural correlates of both tasks using paradigm with audiovisual stimuli. Fifteen subjects performed TOJ and SJ tasks grouped in 18-second blocks. Subjects were asked to estimate onset synchrony or temporal order of onsets of non-semantic auditory and visual stimuli. Common areas of activation elicited by both tasks were found in the bilateral fronto-parietal network, including regions whose activity can be also observed in tasks involving spatial selective attention. This can be regarded as an evidence for the hypothesis that tasks involving selection based on temporal information engage the similar regions as the attentional tasks based on spatial information. The direct contrast between the SJ task and the TOJ task did not reveal any regions showing stronger activity for SJ task than in TOJ task. The reverse contrast revealed a number of left hemisphere regions which were more active during the TOJ task than the SJ task. They were found in the prefrontal cortex, the parietal lobules (superior and inferior) and in the occipito-temporal regions. These results suggest that the TOJ task requires recruitment of additional cognitive operations in comparison to SJ task. They are probably associated with forming representations of stimuli as separate and temporally ordered sensory events.

No evidence for impaired multisensory integration of low-level audiovisual stimuli in adolescents and young adults with autism spectrum disorders.

Abrupt click sounds can improve the visual processing of flashes in several ways. Here, we examined this in high functioning adolescents with Autism Spectrum Disorders (ASD) using three tasks: (1) a task where clicks improve sensitivity for visual temporal order (temporal ventriloquism); (2) a task where a click improves visual search (pip-and-pop), and (3) a task where a click speeds up the visual orienting to a peripheral target (clock reading). Adolescents with ASD were, compared to adolescents with typical development (TD), impaired in judgments of visual temporal order, but they were unimpaired in visual search and orienting. Importantly, in all tasks visual performance of the ASD group improved by the presence of clicks by at least equal amounts as in the TD group. This suggests that adolescents and young adults with ASD show no generalized deficit in the multisensory integration of low-level audiovisual stimuli and/or the phasic alerting by abrupt sounds.