Perceived time and temporal structure: Neural entrainment to isochronous stimulation increases duration estimates

Ninja K Horr,Maria Wimber,Massimiliano Di Luca

doi:10.1016/j.neuroimage.2016.02.011

Abstract

Distortions of perceived duration can give crucial insights into the mechanisms that underlie the processing and representation of stimulus timing. One factor that affects duration estimates is the temporal structure of stimuli that fill an interval. For example, regular filling (isochronous interval) leads to an overestimation of perceived duration as compared to irregular filling (anisochronous interval). In the present article, we use electroencephalography (EEG) to investigate the neural basis of this subjective lengthening of perceived duration with isochrony. In a two-interval forced choice task, participants judged which of two intervals lasts longer – one always being isochronous, the other one anisochronous. Response proportions confirm the subjective overestimation of isochronous intervals. At the neural level, isochronous sequences are associated with enhanced pairwise phase consistency (PPC) at the stimulation frequency, reflecting the brain's entrainment to the regular stimulation. The PPC over the entrainment channels is further enhanced for isochronous intervals that are reported to be longer, and the magnitude of this PCC effect correlates with the amount of perceptual bias. Neural entrainment has been proposed as a mechanism of attentional selection, enabling increased neural responsiveness toward stimuli that arrive at an expected point in time. The present results support the proposed relationship between neural response magnitudes and temporal estimates: An increase in neural responsiveness leads to a more pronounced representation of the individual stimuli filling the interval and in turn to a subjective increase in duration.

Highlights

An interesting distortion in the subjective estimate of duration for intervals in the millisecond-to-second range is the filled duration illusion: intervals that are filled with either a sequence of short stimuli (e.g., Adams, 1977; Buffardi, 1971; Horr and Di Luca, 2015a; Thomas and Brown, 1974) or with one continuous stimulus (e.g., Hasuo et al, 2014; Horr and Di Luca, 2015a; Rammsayer and Lima, 1991) are perceived to last longer than empty intervals that only consist of a beginning and an end marker
We tested whether neural entrainment toward stimuli that appear at regular points in time may mediate duration distortions driven by isochrony
This hypothesis arises from the proposal that perceived duration is linked to the magnitude of neural responses concurrent with the stimulation in the relevant interval (e.g., Eagleman and Pariyadath, 2009; Matthews et al, 2014)

Summary

Introduction

An interesting distortion in the subjective estimate of duration for intervals in the millisecond-to-second range is the filled duration illusion: intervals that are filled with either a sequence of short stimuli (e.g., Adams, 1977; Buffardi, 1971; Horr and Di Luca, 2015a; Thomas and Brown, 1974) or with one continuous stimulus (e.g., Hasuo et al, 2014; Horr and Di Luca, 2015a; Rammsayer and Lima, 1991) are perceived to last longer than empty intervals that only consist of a beginning and an end marker. The fundamental assumption of a magnitude approach is that the degree of neural activity concurrent with the stimulation during an interval is directly related to the interval's perceived duration (e.g., Eagleman and Pariyadath, 2009; Matthews et al, 2014). If the proposed entrainment mechanism is responsible for the overestimation of duration with isochronous intervals, we should be able to directly relate the amount of neural entrainment to the magnitude of overestimation in perceived duration To test this hypothesis, we used electroencephalography (EEG) to record neural responses during a simple two-interval forced choice task in which each trial consisted of a pair of one isochronous and one anisochronous interval. We correlated the PPC effect of perceived duration with participants' general tendency to overestimate isochronous sequences

Participants

Procedure and EEG recording

Results

Discussion