Tactor Localization at the Wrist

Mechanical and Psychophysical Studies of Surface Wave Propagation during Vibrotactile Stimulation

“…Using fewer motors may be beneficial in general since the IT results indicate that only two locations could be accurately identified on the forearm and thigh, and that only five out of nine locations could be identified on the palm. This is consistent with previous research performed on the wrist by Chen et al (2008) in which IT analyses revealed that in a three-by-three array with 25 mm inter-motor spacing only two locations could be accurately identified by two out of three subjects, whereas the third subject could locate four motors. Our finding that the column of activation was more often identified than the row, is also consistent with previous studies which have found the tactile localization is best across the medial-lateral axis as opposed to the proximal-distal axis (Chen et Collins, which might be attributed to the higher frequency of activation of their motors which may cause surface waves to propagate further along the skin.…”

“…The calculation 2 IT gives the maximum number of locations that can be correctly identified (Chen et al, 2008). Given this, the IT values for the palm at 8 and 16 mm were 2.34 bits (5 locations) and 2.46 bits (5.5 locations).…”

“…For example, patterns that move across the forearm are more easily identified than ones that vary along the longitudinal (proximal-distal) axis of the arm (Jones et al, 2009). In addition, motors are more easily identified by their medial-lateral placement (column of activation) than their proximal-distal location (row of activation) (Chen et al, 2008). Another important design consideration that may lead to improved localization accuracy is placement of the motors on or around anatomical "landmarks."…”

“…When a three-by-three array of motors with 25 mm intermotor spacing was placed on the forearm above the wrist and activated at 150 Hz, subjects were asked to identify the location of individual motors as they were activated. The results of this absolute identification test showed that the location of only five out of the nine motors could be identified with more than 50% accuracy, and that the location of only two motors could be absolutely identified as defined by information transfer values (Chen et al, 2008). Results of this test revealed that subjects were more able to identify the position of a motor along the medial-lateral axis (across the limb) as opposed to the proximal-distal axis (along the length of the limb), as indicated by the better identification of the activated column as opposed to the activated row.…”

“…Tactile displays can be used in many applications and come in varying forms. While some displays use static stimuli such as the stationary patterns of bumps used in Braille, others use dynamic stimuli such as vibrating motors contained within a wearable device such as a belt, vest, or glove (Chen et al, 2008;Jones & Held, 2008;Jones et al, 2009;Salzer et al, 2010). The latter is known as a vibrotactile display, since this method uses vibration to communicate.…”