The Journal of Neuroscience, July 15, 2001, 21(14):5289-5296
Temporal Cues Contribute to Tactile Perception of Roughness
Carissa J.
Cascio and
K.
Sathian
Department of Neurology, Emory University School of Medicine,
Atlanta, Georgia 30322
Optimal perception of surface roughness requires lateral movement
between skin and surface, suggesting the importance of temporal cues.
The roughness of periodic gratings is affected by changing either
inter-element spacing (groove width, G) or element width (ridge width, R). Peripheral neural responses to
gratings depend quantitatively on a spatial variable, G,
and a temporal variable, grating temporal frequency
(Ft), with changes in
R acting indirectly through concomitant changes in
Ft. We investigated, psychophysically, the
contribution of temporal cues to human tactile perception of roughness,
using gratings varying in either R or G.
Gratings were scanned across the immobile fingerpad with controlled
movement speed (S) and contact force. In one experiment,
we found that roughness magnitude estimates depended on both
G and Ft. In a second
experiment, discrimination of the roughness of gratings varying in
either R or G was affected by
manipulating Ft. Overall, the effect of
G on roughness judgments was much stronger than that of
Ft, probably explaining why many
previous studies using surfaces that varied only in inter-element
spacing led to the conclusion that temporal factors play no role in
roughness perception. However, the perceived roughness of
R-varying gratings was determined by
Ft and not spatial variables. Roughness
judgments were influenced by G and
Ft in a manner entirely consistent with
predicted afferent response rates. Thus perceived roughness, like
peripheral afferent responses, depends in part on temporal variables.
Key words:
human; perception; somatosensory; touch; finger; texture; gratings; roughness; temporal frequency; psychophysics; discrimination; magnitude estimation
Copyright © 2001 Society for Neuroscience 0270-6474/01/21145289-08$05.00/0