Investigations into Human Vibrotactile Perception: Psychophysical Experiments and Bayesian Modelling

Abstract

<p>A considerable amount of our everyday tactile experience requires interactions between textured surfaces and our fingertips. Such interactions elicit complex vibrations on our skin surface, which are encoded by the mechanosensitive afferents and conveyed to the brain where the perception of the textures emerges seemingly effortlessly. Intuitively, a fundamental question that may be asked is: “what features of the vibration stimuli are behaviourally relevant and what are the neural signatures of these features?” The goal of this thesis is to investigate these questions, which we have done using a combination of theoretical and experimental approaches.</p> <p>Our theoretical approach (in Chapter 2) has been to create an ideal Bayesian perceptual observer that utilizes all the information available in a spike-rate based neural code and makes optimal inferences regarding the amplitude and the frequency of vibration stimuli. Our experimental approach has been to estimate the performance of human participants in vibrotactile detection (in Chapter 3), and in amplitude and frequency discrimination (in Chapter 4) tasks by using psychophysical procedures.</p> <p>The results of these approaches suggest that the human perceptual observer, i.e. the human nervous system, probably uses a rate code to represent vibrotactile amplitude, but a non-rate code, such as a spike timing code, to represent vibrotactile frequency. Additionally, we conclude that humans are capable of inferring and separately perceiving the amplitude and frequency of vibrotactile stimuli; however, depending on experimental tasks, humans might also rely on a feature that combines the amplitude and frequency of vibrotactile stimuli.</p>