Transcranial magnetic theta-burst stimulation of the human cerebellum distinguishes absolute, duration-based from relative, beat-based perception of subsecond time intervals

Abstract

CEREBELLAR FUNCTIONS IN TWO TYPES OF PERCEPTUAL TIMING WERE ASSESSED: the absolute (duration-based) timing of single intervals and the relative (beat-based) timing of rhythmic sequences. Continuous transcranial magnetic theta-burst stimulation (cTBS) was applied over the medial cerebellum and performance was measured adaptively before and after stimulation. A large and significant effect was found in the TBS (n = 12) compared to the SHAM (n = 12) group for single-interval timing but not for the detection of a regular beat or a deviation from it. The data support the existence of distinct perceptual timing mechanisms and an obligatory role of the cerebellum in absolute interval timing with a functional dissociation from relative timing of interval within rhythmic sequences based on a regular beat.

Keywords: absolute; beat; cerebellum; duration; perception; relative; timing; transcranial magnetic theta-burst stimulation.

Figure 1

Auditory timing tests: stimuli. (A) Single-interval duration discrimination (Dur); (B) regularity detection with a mean irregularity of 30% as a reference; (C) isochrony-deviation detection (Iso). Horizontal lines, tones (200 Hz; 100 ms); dotted lines, intervals that differ between target and reference.

Figure 2

Individual pre- and post-stimulation thresholds for the three timing tasks in the TBS and SHAM group. (A) Single-interval duration discrimination (Dur), (B) regularity detection (Reg), (C) isochrony-deviation detection (Iso). There was a significant effect of TBS on duration discrimination thresholds (p < 0.05; paired t-test) (A) but no significant effect on those for the other tasks; SHAM stimulation had no significant effect on any of the tasks.

Figure 3

Threshold ratios for the three timing tasks in the TBS (gray) vs. SHAM (black) group. (A) Duration discrimination for single intervals (Dur), (B) regularity detection (Reg), (C) detection of a deviation from isochrony (Iso). Plots show mean ± SEM. Note the significant difference between TBS and SHAM exclusive to single-interval duration discrimination (A).