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Bhavin Sheth, Murtuza Khan; Sleep affects adaptation. Journal of Vision 2007;7(9):857. doi: 10.1167/7.9.857.
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Emerging evidence shows sleep plays a key role in the processes of learning and memory, which involve change at synaptic and cellular levels in the brain. Of importance, learning on the tasks used in sleep studies is guided by volitional, reward-driven, attentional and goal-directed behavioral processes. Is the role of sleep in synaptic plasticity confined to active, goal-directed processes alone or does sleep impact passive, more automatic forms of synaptic plasticity such as adaptation as well?
Adaptation is an alteration of synaptic strength resulting from sustained exposure to a sensory stimulus. Sustained association of two independent sensory features leads to a durable change in synaptic strength: visual inspection of a red horizontal grating for several minutes causes a post-inspection, achromatic horizontal grating to appear green for several days. Does sleep affect adaptation, a supposedly passive alteration in synaptic strength?
To address this, ten observers monocularly viewed an alternating sequence of red horizontal and green vertical gratings for a total of 5 min, and repeated the experiment a week later but on the previously closed eye. Published reports and our experiments find negligible interocular transfer of the afteraffect. Each observer was adapted twice: at 8 pm (re-tested at 8 am) following a night of sleep, and at 8 am (re-tested at 8 pm) with no sleep intervening. Condition and eye order were counterbalanced across observers. We compared the level of adaptation in the two conditions. Compared with the 8 am–8 pm condition, the re-tested aftereffect in the 8 pm–8am condition was significantly stronger (p [[lt]] 0.05), indicating that overnight sleep caused more retention of the adaptation. Overnight sleep also had a modest effect on the initial acquisition of the aftereffect. Ongoing experiments are testing the impact of circadian rhythm and visual exposure.
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