Effects of passive and active movement on vibrotactile detection thresholds of the Pacinian channel and forward masking

Abstract

We investigated the gating effect of passive and active movement on the vibrotactile detection thresholds of the Pacinian (P) psychophysical channel and forward masking. Previous work on gating mostly used electrocutaneous stimulation and did not allow focusing on tactile submodalities. Ten healthy adults participated in our study. Passive movement was achieved by swinging a platform, on which the participant’s stimulated hand was attached, manually by a trained operator. The root-mean-square value of the movement speed was kept in a narrow range (slow: 10–20 cm/s, fast: 50–60 cm/s). Active movement was performed by the participant him-/herself using the same apparatus. The tactile stimuli consisted of 250-Hz sinusoidal mechanical vibrations, which were generated by a shaker mounted on the movement platform and applied to the middle fingertip. In the forward-masking experiments, a high-level masking stimulus preceded the test stimulus. Each movement condition was tested separately in a two-interval forced-choice detection task. Both passive and active movement caused a robust gating effect, that is, elevation of thresholds, in the fast speed range. Statistically significant change of thresholds was not found in slow movement conditions. Passive movement yielded higher thresholds than those measured during active movement, but this could not be confirmed statistically. On the other hand, the effect of forward masking was approximately constant as the movement condition varied. These results imply that gating depends on both peripheral and central factors in the P channel. Active movement may have some facilitatory role and produce less gating. Additionally, the results support the hypothesis regarding a critical speed for gating, which may be relevant for daily situations involving vibrations transmitted through grasped objects and for manual exploration.

• Active touch
• gating
• movement
• psychophysics
• somatosensory
• touch

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Acknowledgements

This study was supported by Boğaziçi University Research Fund (BAP) no. 13XP8 and Ministry of Development DPT project no. 09K120520 to Burak Güçlü, and by Sakarya University Research Fund (BAP) no. 2014-01-00-001 to Mustafa Z. Yıldız. The authors thank Professor Ehud Ahissar (Weizmann Institute of Science) for motivation and suggestions in the initial design of the experiments, and for critical comments on the paper. Deniz Kılınç worked as the operator in the passive movement experiments; the authors are grateful for her contribution. The authors also thank Associate Professors Albert Güveniş and M. Burçin Ünlü (Boğaziçi University) for helpful discussions.

Declaration of interest

The authors report no conflicts of interest.