Blink reflex to supraorbital nerve stimulation in the cat

Abstract

Neurophysiological studies of the blink reflex to supraorbital nerve stimulation were conducted in eight alert, adult male cats. The cat, like other mammals, shows both short-latency (R1) and long-latency (R2) orbicularis oculi electromyographic (OOemg) components. Measures of OOemg latency, duration, integrated area, and maximum amplitude (MA) were obtained at a stimulus magnitude of 1.5xR2 threshold. The mean (+/-SE) minimal latencies for R1 and R2 were 8.26+/-0.85 and 22.97+/-1.53 ms, respectively. On average, R1 MA was larger than R2 MA. R1 and R2 area measures were similar. Three stimulus paradigms were tested. In a paired-stimulus paradigm, the interstimulus interval (ISI) was randomly varied from 100 to 1200 ms. Ratios were constructed for the OOemg area and MA by dividing the test response by the conditioning response. In this paradigm, although a significant linear relationship was observed only between ISI and R2 MA, conditioning effects were noted on both R1 and R2 area and MA test responses at several ISIs. In a habituation paradigm, both R2 and R1 showed habituation at stimulus frequencies from 0.5 to 2 Hz. In a stimulus-response paradigm, stimulus magnitude was randomly varied between threshold and 2xthreshold. In this paradigm, OOemg area and MA of both R1 and R2 were linearly related to stimulus magnitude. Neither the systemically administered centrally acting alpha2-adrenergic antagonist yohimbine nor agonist clonidine had significant effects on blink reflex parameters, habituation, or the paired-stimulus paradigm. Overall, these results suggest that there are important similarities in the control and modulation of the R1 and R2 components of the blink reflex to supraorbital nerve stimulation in cats.

Experiential Modification of the Trigeminal Reflex Blink Circuit

“…1 A) in the lid closing OO muscle. Like SO-evoked blinks in other nonprimate species, R1 was the dominant component of the rat blink and contributed significantly to lid closure (Pellegrini et al, 1995;LeDoux et al, 1997). In our rats, SO and IO stimuli evoked R1 responses with mean latencies of 4.2 Ϯ 0.03 and 4.6 Ϯ 0.07 ms, respectively.…”

Macaque monkey trigeminal blink reflex circuits targeting orbicularis oculi motoneurons

“…Neurons in sVc would be activated at around 17.5 ms after supraorbital stimulation, leading to activity in ObOc motoneurons around 20.5 ms and EMG activity around 22.5 ms. This is similar to the 23 ms latency observed for the cat R 2 (LeDoux et al, 1997). However, it leaves unexplained how R 2 activation could be evoked in guinea pigs using electrical stimulation amplitudes that did not activate Aδ fibers (Pellegrini et al, 1995).…”

Blink-related sensorimotor anatomy in the rat

“…In humans, the R1 component of the blink reflex to supraorbital nerve stimulation is usually only ipsilateral, whereas the R2 component is bilateral (Kugelberg 1952;Shahani 1970). In rats (Basso et al 1993), cats (Tokunaga et al 1958;Hiraoka and Shimamura 1977;LeDoux et al 1997) and guinea pigs (Pellegrini et al 1995), both R1 and R2 are unilateral with stimulus thresholds for unilateral blinks. Both R1 and R2 can be bilateral in rats and guinea pigs at stimulus magnitudes greater than twice threshold.…”