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Discharge patterns of first and second order vestibular neurons responding to angular acceleration in the plane of the lateral canals were studied in gerbil. The resting discharge activity of each cell was used to characterize the neuron by measureing the coefficient of variation and coefficient of skewness of the interspike interval distributions. Sinusoidal angular oscillations ranging in frequency from 0.0125 to 5.0 Hz were delivered by a velocity controlled rate-table. A PDP-12 minicomputer system was used on-line to display period and post-stimulus histograms of discriminated single unit activity. Off-line Fourier analysis of the period histograms was used to determine the phase of cell response to sinusoidal accelerations, while the average level and amplitude were determined by a least squares fitting algorithm applied over the fraction of the stimulus period where the cell discharged. First order neurons were found to have high discharge rates (average = 61.7 imp./sec) and bidirectional responses to rotation, and were of two groups called regular and irregular according to their resting discharge patterns. Second order neurons, located mainly in the medial and lateral vestibular nuclei, had low or even zero resting discharge rates (average = 17.8) resulting in more uni-directional responses and were of a single population. For frequencies less than 10 Hz, the Bode plots of the regular first order neurons are similar to that of a first order system with a time constant of about 2 sec as predicted by the torsion pendulum theory for cupula movement. The irregular first order neurons show an increasing gain above 0.5 Hz and a large phase lead relative to angular velocity above 1.0 Hz suggestive of a fractional power transfer function. The second order neurons show the phase and gain characteristics of the regular first order neurons being in phase with angular velocity above 1.0 Hz.

Variable Frequency Photo-stimulation (VFP) goggles are a form of portable stroboscope, using red Light Emitting Diodes to alternately illuminate the right and left eyes, with the eyelids closed, at a rate of 0.5 to 50 Hz. VFP goggles were used in the treatment of 7 patients with migraine headache. Of 50 migraine headaches recorded, 49 were rated by the patient as being helped and 36 as being stopped by using the VFP goggles. Treatment reduced the median duration of headache in all patients. The interval between migraine headaches appeared to be increased in the two cases with a follow up of more than 18 months. We conclude in this preliminary study that VFP appears to be effective in the treatment of migraine.