It’s no secret that brief naps leave us feeling mentally as well as physically refreshed, but it has not been entirely clear why. New research from Weill Cornell Medicine neurosurgery resident Natasha Kharas, MD, PhD, and colleagues at Rice University, Houston Methodist, and Stanford School of Medicine identifies the neural mechanisms behind the boost in post-nap cognitive performance.
The research team measured activity in three brain areas associated with task performance, recording measurements before, during, and after short (30-minute) naps. Recording thousands of neurons in visual and dorsolateral prefrontal cortices, researchers examined the neuronal activity and changes in information coding that influenced how well macaque monkeys performed on a visual discrimination task after naps as compared with a control group that did not nap. Researchers documented increases in neuron firing rates and desynchronization among neuronal populations in monkeys that had napped. They were further able to replicate the behavioral improvements in animals that had not napped by applying low frequency (4 Hz) electrical stimulation to the mid-level visual cortex (V4).
“In this study, we found that non-rapid eye movement (NREM) sleep improves behavioral performance by desynchronizing neuronal circuits.” says Dr. Kharas, who worked on the study during her tenure in the laboratory of senior study author Valentin Dragoi, PhD, a professor at Houston Methodist Research Institute and Rice University. “While the animals were asleep, we observed synchronized firing among neurons across the three brain regions. After NREM sleep, the neurons became desynchronized, and we observed improvements in information coding and task performance. We further used temporal interference to electrically stimulate neurons at 4 Hz, which replicated the beneficial effects of NREM sleep. This lays the groundwork for future neuromodulation in humans with sleep disorders.”
The study’s focus on short periods of sleep, before the brain enters the rapid-eye movement (REM) stage of deep sleep, provides insight into why humans get a cognitive boost after NREM sleep (a short nap). The paper, “NREM sleep improves behavioral performance by desynchronizing cortical circuits,” was published in the November 22 issue of the journal Science.
In addition to senior author Valentin Dragoi, Dr. Kharas’s co-authors include Mircea Chelaru and Arun Parajuli of Houston Methodist, who were previously at the McGovern Medical School of the University of Texas in Houston, and Sarah Eagleman of Stanford School of Medicine in Palo Alto. No monkeys were harmed in the study.
