Effects of sleep on human reflexes with a double component.

Since Kugelberg in 1952 originally described two components of the blink reflex, the initial component was considered to be a proprioceptive or a myotatic reflex because it was briefer in duration and more These reflexes were recorded from the orbicularis oculi muscle and were elicited by tapping the glabella or stimulating the supraorbital nerve percutaneously. During a detailed study of human flexor reflexes, Shahani and Young (1968a, b) noticed a similarity between the two components of the flexor reflex and those of the blink reflex. This similarity pertained to the size, shape, and relative latencies of the two components. In addition, it was possible to evoke homolateral blink reflexes consisting of both components by single brief electrical shocks to the skin of any part of the face supplied by the first division of the trigeminal nerve. It was therefore suggested that the two components of both the blink reflex and the flexor reflex were analogous and that both were cutaneous reflexes. During extensive studies on human flexor reflexes and the blink reflexes it was noted that, although the first component of these reflexes was relatively constant when the subject was relaxed, apprehension resulted in marked increase in the amplitude of the second component. This phenomenon suggested the possibility that there was differential central control of the two components of these reflexes. The present studies on the effect of sleep on these two human reflexes with a double component have confirmed that impression. In addition to similarities pertaining to size, shape, and relative latencies, the central mechanism responsible for the differential control of the two components of the blink reflex and the flexor reflex is also similar. METHODS Nine normal healthy subjects, six males and three females, ranging from 20 to 64 years of age, were studied. Two male patients with Parkinson's disease, aged 62 and 64 years, were also studied. The subjects lay supine on a comfortable couch in a warm room. For eliciting flexor reflexes, electrical shocks were delivered through two insulated steel needles bared at the tips, which were inserted intradermally approximately 0-5 to 2 cm apart in the medial sole of the foot. The stimuli were fed through an isolation transformer from a DISA Multistim and were 20 msec long trains of 0-1 msec square wave pulses at 500 c/s. Stimulus intensity ranged from 5 to 50 V. Electromyographic activity was recorded via small clip electrodes with …