What is the difference between an impulsive and a timed anticipatory movement ?
(2025) Scientific Reports — Vol. 0322-25.2025, n° 0322-25.2025, p. 0322-0325 (2025)
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- Imagine yourself in a car race waiting for the traffic light to go green. Impulsivity could push you to accelerate when the light is still red. In contrast, temporally guided anticipation could lead you to accelerate at the time the light goes green. Whether these two types of early responses rely on the same or different neural processes is an open question. This question was investigated using an oculomotor task where the delay between a warning and an imperative visual stimuli was predictable. The spatial uncertainty of the 'go' signal was also varied. On average, 10% of experimental trials were associated with a response before the 'go' signal ('early saccade'). After the offset of the warning stimulus, the latency distribution of early saccades was bimodal, with a first mode peaking after 200 ms (1 mode saccades) and a second one starting to build-up after 375 ms (2 mode saccades). With increasing delay duration: the number of 1 mode responses decreased whereas the number of 2 mode responses remained approximately constant; the latency and variance of 2 mode saccades increased; the maximum velocity of 2 mode responses decreased. In general, the amplitude of 2 mode responses was larger. These results show that there are probably two independent processes taking place before an expected event: an unintentional release of inhibition evoking an impulsive 1 mode saccade and an anticipatory process leading to a 2 mode saccade. Before an expected event, early motor responses are often observed. The cause of these responses during stimulus expectation is largely unknown. Two competing hypotheses have been suggested: lack of inhibition or anticipation. We studied early responses in an oculomotor task where temporal and spatial expectations were experimentally altered. Saccades during the expectation before the visual target could be categorized into two groups based on latency. The first group was composed of saccades that were not temporally guided, in contrast with saccades in the second group. Amplitude and maximum velocity of saccades in the second group were larger. Therefore, we show that two independent processes could be distinguished during the expectation of a visual stimulus: inhibitory control followed by temporal anticipation.
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Drążyk, D., Rida, A., & Missal, M. (2025). What is the difference between an impulsive and a timed anticipatory movement ? Scientific Reports, 0322-25.2025(0322-25.2025), 0322-0325. https://doi.org/10.1523/ENEURO.0322-25.2025 (Original work published 2025)