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Doug Crawford, Steven Prime; Cortical Mechanisms for Trans-Saccadic Memory of Multiple Objects. Journal of Vision 2009;9(8):18. doi: https://doi.org/10.1167/9.8.18.
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© ARVO (1962-2015); The Authors (2016-present)
Humans can retain the location and appearance of 3–4 objects in visual working memory, independent of whether a saccade occurs during the memory interval. Psychophysical experiments show that, in the absence of retinal cues, extra-retinal signals are sufficient to update trans-saccadic memory, but where and how do these signals enter the visual system? It is know that ‘dorsal stream’ areas like the parietal eye fields update motor plans by remapping them in gaze-centered coordinates, but the equivalent neural mechanisms for updating object features across saccades are less understood. We investigated the possible role of extra-retinal signals from the cortical gaze control system by applying trans-cranial magnetic stimulation (TMS) to either the human parietal eye fields or the frontal eye fields, during the interval between viewing several objects and testing their remembered orientation and location. Parietal TMS had a baseline effect on memory of one feature and reduced memory capacity from approximately three down to one feature, but only when applied to the right hemisphere near the time of a saccade. The effects of frontal cortex TMS on trans-saccadic memory capacity were similar, but were more symmetric, and did not affect baseline feature memory. In our task, the latter would occur if spatial memory were disrupted without affecting feature memory. These experiments show that cortical gaze control centers usually associated with the ‘dorsal’ stream of vision are also involved in visual processing and memory of object features during saccades, possibly influencing ‘ventral stream’ processing through re-entrant pathways.
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