Visual space generated by saccade motor plans

Abstract

How the perception of space is generated from the multiple maps in the brain is still an unsolved mystery in neuroscience. We investigated whether space perception in general is constituted by information contained in efference copy signals. A neural pathway ascending from the superior colliculus through the medio-dorsal (MD) nucleus of thalamus to the frontal eye field has been identified in monkeys to convey efference copy information about the metrics of upcoming eye movements. Information sent through this pathway stabilizes vision across saccades. We wondered whether this motor plan information might also shape spatial perception even when no saccades are performed. We studied patients with lesions in different parts of the thalamus. Patients performed a double-step task testing motor updating, a trans-saccadic localization task testing visual updating and a localization task during fixation testing a general role of motor signals for visual space in the absence of eye movements. Single patients with medial and lateral thalamic lesions (affecting the MD and VL nuclei) showed deficits in the double-step task, reflecting insufficient transfer of efference copy. However, a patient with an MD lesions was impaired in transsaccadic localization, suggesting that different types of efference copies contribute to motor and visual updating. Interestingly, the MD patient also mislocalized objects during fixation. The size and the spatial location of the deficit was consistent with the under-representation of the saccade vectors in first two experiments. These data suggest that motor plans are not consulted only as the final output stage for generating actions but play a primary role in constituting the perceptual experience that leads to the generation of behavior.

Acknowledgement: ERC grant moreSense (757184)