Journal of Neuroscience, Vol 7, 2168-2180, Copyright © 1987 by Society for Neuroscience
Sinusoidal movement of a grating across the monkey's fingerpad: representation of grating and movement features in afferent fiber responses
AW Goodwin and JW Morley
Gratings of alternating grooves and ridges were moved sinusoidally back and
forth across the monkey's fingerpad. Each grating was completely specified
by its spatial period and the movement by its peak speed: together these
determined the peak temporal frequency at which grating ridges passed over
the skin. Responses of cutaneous, mechanoreceptive afferents innervating
the fingerpad were characterized in terms of these 3 parameters. Slowly
adapting afferents (SAs), rapidly adapting afferents (RAs), and Pacinian
afferents (PCs) had different characteristics. The responses (mean cyclic
discharge rates) of the SAs increased when the spatial period of the
grating increased (and peak speed of movement remained constant) but did
not change with changes in the peak speed of the movement (while the
spatial period of the grating remained constant). Conversely, the responses
of the PCs increased when the peak speed of movement increased (and the
spatial period remained constant) but were relatively insensitive to
changes in the spatial period of the grating (while the peak speed remained
constant). The responses of the RAs increased as the spatial period of the
grating increased (and peak speed remained constant) and also increased as
the peak speed of movement increased (and the grating spatial period
remained constant). When the peak temporal frequency of the grating ridges
was held constant, the responses of all 3 afferent groups changed with
changes in the grating spatial period or in the peak speed of movement.
Information about the spatial features of the grating, independent of the
peak speed of movement, was present in the SA population response and in
the ratios of the RA and PC population responses. Information about the
peak speed of movement, independent of the spatial period of the grating,
was present in the PC population response and could be extracted from the
RA population response.
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