Frequency Distribution of the Time Interval between Quick Phase Nystagmic Eye Movements

Abstract

We measured the frequency distribution of the time interval between quick phases of nystagmic eye movements in 8 patients with congenital nystagmus. For each patient we recorded a 3- to 4-second long electro-oculographic (EOG) signal, repeating each session 22 times. The period of the nystagmic cycles was computed for each record, by evaluating the peak frequency of the nystagmic oscillations via spectral analysis of the EOGs. This period is a measure of the time interval between quick phases. Its distribution ranged between 100 and 600 ms and peaked at about 240 ± 50 ms, with a gaussian shape for values less than about 300 ms. Our measurements were considered as providing the distribution of intersaccadic latencies in normal humans.

Quick Phases of Infantile Nystagmus Show the Saccadic Inhibition Effect

“…38,42,43 We suggest, therefore, that this provides further evidence that the quick phases of IN are fundamentally saccadic in nature. This idea is consistent with the observation that quick phases and saccades have similar main sequences and intersaccadic intervals, 30,31 and that saccadic accuracy and latency can be altered by quick phase activity. 33,57 Moreover, it lends support to those who claim that the oculomotor system in people with IN is functionally intact but uses a different viewing strategy.…”

“…15,16,29 The quick phases of IN therefore appear to be similar to saccadic eye movements: they show the same relationship between amplitude and peak velocity (the main sequence) 30 and exhibit the same peak intersaccadic interval. 31 Moreover, both quick phases and saccades show dynamic overshoots. 32 Yet despite these similarities, quick phases are normally considered to be involuntary 33 and made without the individual being aware of them.…”

A “beat-to-beat” interval generator for optokinetic nystagmus

“…The neural control of nystagmus SP velocity has been characterized extensively in both experimental animals and humans (e.g., Raphan et al 1977;Robinson 1977;Furman et al 1989). However, with the exception of data reported by Cheng and Outerbridge (1974a, b); Honrubia et al (1971a-c); and Bosone et al (1990), the issues of the control of the duration of SPs and FP amplitudes have received little attention. The major objective of this study is to derive a quantitative description of the timing of the alternation between FPs and SPs.…”

Distribution of Quick-Phase Intervals in Optokinetic Nystagmus

“…In a recent paper, Bosone et al [1] mea sured the frequency distribution of the time interval between quick phases in human sub jects suffering from congenital nystagmus. When plotted as a histogram, the resultant distribution had the skewed form characteris tic of measurements of saccadic latency to visual targets.…”

“…Finally, figure 1 also plots the quick-phase time intervals of Bosone et al [1] for congeni tal nystagmus in the same way, for the single subject whose histogram was published (squares) and for the pooled data from all 8 subjects (small circles). The scatter is inevita bly larger because of the small size of the data sets (only 24 observations in the former case), but the general agreement of the distribution for the single subject with normal optokinetic nystagmus and visually evoked saccades is good.…”