Sleep and Visual Discrimination Learning

Abstract:
Evidence from both human and animal studies suggests that sleep is important for the consolidation of memories. In animals, "REM sleep windows," occurring hours to days after training, have been identified. During these windows, REM sleep is elevated, and if REM sleep is blocked during the window learning is diminished or eliminated. A role for NREM sleep in consolidation of declarative memories has also been reported. We now report that both REM and NREM sleep are critical to improvement on a human visual discrimination task.

Subjects came into the sleep laboratory for one night. Experimental subjects were trained on the visual discrimination task (VDT) before retiring for the night. All subjects were wired for polysomnography, had their sleep recorded overnight, and were tested on the VDT in the morning. Learning was defined as the decrease in recognition threshold.

Learning was highly correlated with SWS ₁ , the amount of deep sleep in the first quarter of the night, (r=0.70) and with REM ₄ , the amount of REM sleep in the last quarter (r=0.78). Correlation was highest with the product, SWS ₁ x REM ₄ (r = 0.89), suggesting a two-step process of sleep-dependent memory consolidation.