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We all sleep – some of us less than others – and yet the exact role sleeping plays on our bodies and minds has largely remained elusive.
By focusing on the effects of sleep deprivation on the brain, scientists now believe sleep is needed in order to ensure brain function stays on track, and to prevent connectivity changes.
Christoph Nissen and his team from the University Medical Center Freiburg, in Germany, compared the brain activity of 20 participants. The first study was done after a full night's sleep while the second study was carried out after a night of sleep deprivation, a total of 24 hours without any sleep.
During both experiments, the scientists applied magnetic pulses to the motor cortex, the area of the brain responsible for controlling movement, in order to activate neurons in the participants' brains.
From this, the team discovered that sleep deprivation causes significant, so-called 'connectivity changes' to occur. In particular, it was found that in sleep-deprived applicants 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.
Brain excitability refers to the strength of reactions of the brain to a given stimulus or irritation. It is believed that brain excitability reflects the overall strength of connectivity in the area of the brain it is targeting, therefore when it is affected by something like sleep deprivation, excitability changes meaning in a way that causes the strength of synapses in the brain to change.
This explains why people feel less alert and unable to complete simple tasks when they're sleep deprived. Although this sounds obvious, it is the first time a direct link between the two has been visualised in this way.