Sleep deprivation in humans can lead to connectivity changes in the brain, according to a study published online in Nature Communications. Sleep is thought to regulate the connective strength between neurons, which in turn is important for learning and memory. This theory has been difficult to test in humans, but the new study uses indirect measurements to measure changes in connectivity.
Christoph Nissen and colleagues compared the brain activity of 20 participants after one night of sleep and after one night of sleep deprivation. Targeting the motor cortex, the area of the brain responsible for controlling movement, the team applied magnetic pulses to activate neurons in the participants’ brains. They found that the strength of the pulse needed to produce a muscle response in the left hand was much lower for the sleep deprived participants, suggesting brain excitability was higher after lack of sleep. In addition, the authors found that activity-dependent connectivity changes in neurons were weaker in sleep-deprived participants. Sleep-deprived individuals also performed poorly on a word-pair memory task and their blood samples had reduced levels of BDNF, a signalling molecule known to regulate synaptic plasticity.
Together, these results may help elucidate the mechanisms through which loss of sleep leads to connectivity changes in the brain and poor memory performance.