Journal of Neuroscience, Vol 7, 2192-2202, Copyright © 1987 by Society for Neuroscience
Sinusoidal movement of a grating across the monkey's fingerpad: effect of contact angle and force of the grating on afferent fiber responses
AW Goodwin and JW Morley
Responses were recorded from cutaneous afferents innervating
mechanoreceptors in the monkey's fingerpad. When gratings of alternating
grooves and ridges were moved sinusoidally back and forth across the
receptive field, the responses of the afferent were often not equal for the
2 directions of movement. To investigate this phenomenon, the position of
the center of the afferent's receptive field, relative to the contact area
between the grating and the finger, was varied systematically. For some
afferents, regardless of these relative positions, the response was always
greater for a particular direction of movement. For other afferents,
regardless of these relative positions, the responses for the 2 directions
of movement were always equal. For a minority of afferents, the response
was greater for movement in one particular direction for some relative
positions and greater for movement in the opposite direction for other
relative positions. Slowly adapting afferents (SAs), rapidly adapting
afferents (RAs), and Pacinian afferents (PCs) exhibited all 3 types of
response patterns. We could not relate these patterns to the afferent type
or to the positions, in the fingerpad, of the receptive field center. The
contact force between the grating and the finger was varied by varying the
contact displacement (indentation). Two grating spatial periods were used.
For SAs and PCs the response increased with increasing indentation for both
gratings. For RAs the response to the finer grating increased with
increasing indentation, but the response to the coarser grating did not.