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Caitlin Tozios, Keisuke Fukuda; Up-regulatory nature of voluntary control for visual long-term memory encoding and its down-regulatory side effects. Journal of Vision 2018;18(10):1300. doi: https://doi.org/10.1167/18.10.1300.
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The capacity for visual long-term memory (VLTM) to store detailed and accurate representations of images is quite remarkable (e.g., Brady et al., 2008). However, the nature and the extent of voluntary control over the quality of VLTM encoding is unclear. To test this, we sequentially presented a pair of random objects for participants to remember. Critically in some trials, one of the paired objects was cued to be up-regulated (i.e., try harder to remember) or to be down-regulated (i.e., try not to remember) either before (Experiment 1; pre-cue) or after (Experiment 2; post-cue) the onset of the objects. Here we found that participants successfully up-regulated the quality of memory encoding regardless of the cue-to-object stimulus onset asynchrony (SOA). However, they failed to down-regulate the quality of memory encoding regardless of cue-to-object SOA. Interestingly, we also observed reliable down-regulation of memory encoding quality for objects that accompanied up-regulated objects, only when the cue was provided prior to the onset of the objects. To further investigate the underlying neural mechanisms of voluntary control of memory encoding, we repeated the pre-cue experiment while measuring participants' electroencephalograms (EEG). Our results showed that participants reduced the posterior alpha (8-14Hz) power contralateral to the up-regulation cue following the cue onset, thus reflecting the exertion of selective attention to the to-be-up-regulated object. Taken together, these results suggest that our ability to voluntarily control the memory encoding quality is up-regulatory in nature, but it can be used to indirectly down-regulate the memory encoding quality of accompanying stimuli only if the cue is provided before the stimuli onset in order to attentionaly bias the perceptual encoding of the stimulus.
Meeting abstract presented at VSS 2018
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