Effects of stimulus duration on the response properties of Pacinian corpuscles: implications for the neural code.
Based on physiological and psychophysical data, it has been suggested that the neural code for threshold detection in the P channel, mediated by Pacinian corpuscles (PCs), may be 2-4 neural impulses/stimulus (Bolanowski et al., 1988). To further test the efficacy of this code, responses from PCs were measured at different vibratory burst durations. Since it is known that the P channel has the capacity to summate vibratory stimuli temporally within the central nervous system, the effect should also be present in the physiological results. Temporal summation predicts a decrease in threshold at a rate of -3 dB/doubling of stimulus duration. Responses from single PCs were integrated by counting neural spikes over the entire burst duration. Furthermore, real-time responses were integrated with a low-pass filter, more accurately modeling the central process. For the spike-counting scheme, a criterion of 4 impulses/stimulus showed a decrease in stimulus amplitude for increases in duration similar to that obtained psychophysically. The amplitude-duration function obtained with the low-pass filter, however, resulted in a function which did not follow that obtained psychophysically, regardless of the number of impulses/stimulus. Since the P channel is known to have a central integrator, it has been concluded that activity of a single PC afferent probably is not sufficient to signal threshold in the P channel.
Checkosky
C M
CM
Interdepartmental Neuroscience Program, University of Rochester School of Medicine, New York 14642.
Bolanowski
S J
SJ
D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D005071:Evoked Potentials / Q000502:physiology; D008643:Mesentery / Q000294:innervation; D008959:Models, Neurological; D009412:Nerve Fibers / Q000502:physiology; D010141:Pacinian Corpuscles / Q000502:physiology*; D011601:Psychophysics; D011817:Rabbits; D011930:Reaction Time / Q000502:physiology*; D012684:Sensory Thresholds / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology*; D014110:Touch / Q000502:physiology*