Abstract
Our visual system is adaptive and plastic in response to stimuli or environment we experience. Although visual adaptation and plasticity have been extensively studied while participants are awake, little is known while participants are asleep. However, it is vital to understand visual adaptation and plasticity throughout wakefulness and sleep, as visual processing during wakefulness and sleep interacts with each other. It has been well documented that the quality of sleep degrades due to exposure to a new sleep environment, known as the first night effect (FNE). FNE is significantly reduced after the first night because of adaptation to the new environment. It has been suggested that slow-wave activity (SWA) is modified in the first night. SWA is commonly investigated in the frontal or central regions of the scalp, and not in the occipital region. Is the visual system involved in the FNE and adaptation process? To address this question, we measured the strength of SWA (1-4 Hz) originated in the visual cortex during sleep and compared the strength of SWA between the first and second experimental sleep using magnetoencephalography (MEG), polysomnography, and a magnetic resonance imaging (MRI). Young and healthy participants (n = 8) underwent 3-4 nightly MEG sessions during sleep, and one MRI session. Wavelet-transformed MEG during the NREM sleep in the first sleep cycle was combined with high-resolution structural MRI to constrain the sources of SWA to the cortical mantle individually. The results showed that the strength of SWA in the visual cortex was reduced in the first night in comparison to the second night. Thus, the visual system is involved in the adaptation process associated with the FNE, through modification of SWA. These results suggest that the visual system does not cease adapting to a new environment and continues to be plastic even during sleep.
Meeting abstract presented at VSS 2013