Temporal Integration of Tactile Inputs from Multiple Sites
We investigated the perceived frequency elicited by two vibrating probes on the skin. Participants (n = 11) compared two probes vibrating in counter-phase (25 Hz), with comparison stimuli of in-phase vibration (18–54 Hz). They indicated which had the high
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MARCS Institute, Western Sydney University, Sydney, Australia [email protected] 2 Neuroscience Research Australia, Sydney, Australia 3 School of Medical Sciences, Faculty of Medicine, UNSW Australia, Sydney, Australia 4 The Faculty of Medicine and Health Sciences, Linköping University, Linköping, Sweden
Abstract. We investigated the perceived frequency elicited by two vibrating probes on the skin. Participants (n = 11) compared two probes vibrating in counter-phase (25 Hz), with comparison stimuli of in-phase vibration (18–54 Hz). They indicated which had the higher perceived frequency. Skin sites on the palm (glabrous) and arm (hairy) were tested with a range of probe separations (1–16 cm) and amplitudes (10–120 µm). Perceived frequency increased with decreasing separation of the probes (F1,10 = 182.8, p < 0.001). The two skin sites did not significantly differ (F1,10 = 3.6, p = 0.087). Perceived frequency was only minimally affected by amplitude changes between 40 and 120 μm (F2,20 = 6.4, p = 0.007, g2G ¼ 0:06). Both phase and spatial separation strongly influence vibrotactile interaction between two skin locations in a manner largely independent of changes in amplitude, and of skin type. Keywords: Touch
Vibration Frequency Psychophysics Human
1 Introduction Fast adapting mechanoreceptors in the skin are uniquely adapted to respond to mechanical vibration. Recordings of FA1 and FA2 primary afferents show that their responses are precisely phase-locked to each cycle of sinusoidal vibration, providing highly reliable temporal information [1, 2]. In this study, we investigated how temporal features of vibrotactile stimulation are processed for perception of frequency for inputs that are spatially separated. It is not obvious to what extent the precise temporal information available in primary afferent trains is processed in later neural pathways, nor are the perceptual consequences of any such processing understood. During vibrotactile stimulation, some afferents with receptive fields furthest from the center of stimulation will be poorly activated and fail to respond on some cycles [2]. This does not give rise to a lower apparent frequency in that zone, however [3], and frequency perception appears to rely on an integrated population response. Units with receptive fields close to the center of stimulation that respond on every cycle of © Springer International Publishing Switzerland 2016 F. Bello et al. (Eds.): EuroHaptics 2016, Part I, LNCS 9774, pp. 204–213, 2016. DOI: 10.1007/978-3-319-42321-0_19
Temporal Integration of Tactile Inputs from Multiple Sites
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vibration may effectively ‘fill-in’ the missing spikes from poorly activated units that respond intermittently, resulting in integrating inputs from multiple units [1]. If no one afferent is adequately stimulated, multiple weakly responding afferents might fill-in for each other, preserving the stimulus frequency in the population response. A challenge for central nervous system (CNS) neurons to preserve the precise timing present in
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