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Poster De Conférence Année : 2011

Neural control of saccades to a moving target : contribution of the Fastigial Oculomotor Region

Résumé

The neural representation of a moving target undergoes a spatiotemporal expansion while its associated retinal activity propagates toward the brain motor areas for recruiting the appropriate muscles. Indeed, the divergent projections within the visual system and the transmissions of signals through multiple relays with diverse conduction velocities and integration times lead to activities that are spatially and temporally distributed across several brain regions. In spite of this neural “blurring”, saccades toward such a target are astonishingly accurate. It has been proposed that their generation involves two parallel pathways to the saccade generator (Keller et al. 1996). One pathway would carry a primary drive based on a snapshot of initial target eccentricity. Another pathway would compute the complementary drive required to compensate for the subsequent target motion. These two commands would converge on saccade-related burst neurons in the contralateral reticular formation. According to this “dual-drive” hypothesis, the primary drive would originate from the deep Superior Colliculus and the compensatory drive from the cerebellum, possibly from the Fastigial Oculomotor Region (FOR). We tested this hypothesis by studying in the monkey, the consequences of inactivating the FOR on the accuracy of saccades toward a moving target. The task was to foveate and track a central visual target which moved toward the periphery along 8 possible directions with 4 different velocities. In addition to its effects on the accuracy of saccades toward static targets (ipsilesional hypermetria, contralesional hypometria and ipsipulsion of vertical saccades), FOR inactivation also impaired the gain of pursuit: it was increased for ipsilesional target motions and decreased for contralesional ones. During contralesional target motions, the amplitude of catch-up saccades was diminished. The reduced pursuit gain and the hypometria prevented the animal to foveate the target: gaze always lagged behind the target position. During ipsilesional target motions, because of the saccade hypermetria and increased pursuit gain; gaze often led the target position. Interestingly irrespective of the target motion direction, the amplitude of the first catchup saccades increased with target velocity. These results indicate that target velocity signals can reach the saccade generator even when the FOR is inactivated.
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hal-04190288 , version 1 (29-08-2023)

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Paternité - Pas d'utilisation commerciale - Pas de modification

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  • HAL Id : hal-04190288 , version 1

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Laurent Goffart, Akao Teppei, Kurkin Sergey, Fukushima Junko, Fukushima Kikuro. Neural control of saccades to a moving target : contribution of the Fastigial Oculomotor Region. Society for Neuroscience Meeting, 2011, Washington DC, United States. ⟨hal-04190288⟩

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