Quantifying spatial acuity of frequency resolved midair ultrasound vibrotactile stimuli

Spatial acuity is a fundamental property of any sensory system. In the case of the somatosensory system, the two-point discrimination (2PD) test has long been used to investigate tactile spatial resolution. However, the somatosensory system comprises three main mechanoreceptive channels: the slowly adapting channel (SA) responds to steady pressure, the rapidly adapting channel (RA) responds to low-frequency vibration, and the Pacinian channel (PC) responds to high-frequency vibration. The use of mechanical stimuli in the classical 2PD test means that previous studies on tactile acuity have primarily focussed on the pressure-sensitive channel alone, while neglecting other submodalities. Here, we used a novel ultrasound stimulation to systematically investigate the spatial resolution of the two main vibrotactile channels. Contrary to the textbook view of poor spatial resolution for PC-like stimuli, across four experiments we found that high-frequency vibration produced surprisingly good spatial acuity. This effect remained after controlling for interchannel differences in stimulus detectability and perceived intensity. Laser doppler vibrometry experiments confirmed that the acuity of the PC channel was not simply an artifact of the skin's resonance to high-frequency mechanical stimulation. Thus, PC receptors may transmit substantial spatial information, despite their sparse distribution, deep location, and large receptive fields

Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task

Tactile Haptics: A Study of Roughness Perception in Virtual Environments

This thesis presents the design of a tactile device that can be used to display varying magnitudes of roughness. The device is designed to be attached to an existing force feedback device in order to create a package that is able to display both macro-level (force feedback) and micro-level (tactile feedback) information to the users. This device allows the users to feel a simulated texture by placing an index finger on an aperture. The stimulus is created with a spiral brush made of nylon bristles. The brush is attached to a DC motor and the speed and direction of rotation of the brush are used to generate textures at the fingertip through the aperture. Three psychophysical experiments are conducted to study the effects of speed and direction on the roughness perception. The first experiment is designed to investigate the sensitivity to a change in the speed of the brush. This experiment is conducted for two levels of base speed and it is found that as the base speed increases, the just noticeable difference (JND) with respect to speed decreases. In the second experiment, it is found that this tactile device is able to represent textures of rough nature, such as sandpaper. It is also found that the human roughness perception cannot be described in a unique manner. Two opposite definitions of rough textures are identified in this experiment. While some users relate an increase in the speed of the brush to increasing roughness, others relate it to decreasing roughness. Further, the results show that the effects of direction are insignificant on the roughness perception for both groups of users. In the third experiment, the effects of direction are studied more closely by presenting the two directions successively with a time gap of $0.5s$. It is found that with this small time gap, the users are able to discriminate between directions, unlike in the previous experiment. The roughness perception is affected by the change in direction when the time gap is small. These findings open further areas that need to be investigated before a robust tactile device can be designed

Engineering data compendium. Human perception and performance. User's guide

The concept underlying the Engineering Data Compendium was the product of a research and development program (Integrated Perceptual Information for Designers project) aimed at facilitating the application of basic research findings in human performance to the design and military crew systems. The principal objective was to develop a workable strategy for: (1) identifying and distilling information of potential value to system design from the existing research literature, and (2) presenting this technical information in a way that would aid its accessibility, interpretability, and applicability by systems designers. The present four volumes of the Engineering Data Compendium represent the first implementation of this strategy. This is the first volume, the User's Guide, containing a description of the program and instructions for its use

Sensory Communication

Contains table of contents on Section 2, an introduction, reports on eleven research projects and a list of publications.National Institutes of Health Grant 5 R01 DC00117National Institutes of Health Grant 5 R01 DC00270National Institutes of Health Contract 2 P01 DC00361National Institutes of Health Grant 5 R01 DC00100National Institutes of Health Contract 7 R29 DC00428National Institutes of Health Grant 2 R01 DC00126U.S. Air Force - Office of Scientific Research Grant AFOSR 90-0200U.S. Navy - Office of Naval Research Grant N00014-90-J-1935National Institutes of Health Grant 5 R29 DC00625U.S. Navy - Office of Naval Research Grant N00014-91-J-1454U.S. Navy - Office of Naval Research Grant N00014-92-J-181