Date of Graduation


Document Type


Degree Type



School of Medicine


Physiology, Pharmacology & Neuroscience

Committee Chair

Paul B. Brown.


The encoding of vibrotactile pitch by neurons of the somatosensory system has been investigated at many levels of the neuraxis. These studies, however, have not extended to the spinal dorsal horn, which is known to process low threshold mechanoreceptive input. The studies presented here were designed to assess the possible role of the dorsal horn in the encoding of vibrotactile pitch. To accomplish this task, dorsal horn single unit extracellular recordings were obtained during periodic electrical and sinusoidal mechanical stimulation of their receptive fields. Techniques used in classifying vibrotactile pitch encoding were similar to those used in other somatosensory nuclei, including analyses of firing rate and periodicity. Firing rate profiles, phase vectors, histograms and power spectra were used to quantify the responses. The analyses indicate that for most cells, firing rate is adequate to encode stimuli at 50 Hz and below, but insufficient at 100 and 200Hz. A small number of neurons were able to encode stimulus frequencies of 50Hz and higher in their firing rates. Periodicity is present in most cell discharges at all frequencies. This leads to the conclusion that at least some dorsal horn neurons are able to encode vibrotactile pitch in a way similar to that found in other somatosensory areas, at least with regard to periodicity and firing rate.