# A New Hypothesis for Sleep: Tuning for Criticality

**Source**: https://www.maths.tcd.ie/report_series/abstracts/tcdm0603.html
**Parent**: https://www.maths.tcd.ie/research/papers/

**A New Hypothesis for Sleep: Tuning for Criticality**

We propose that the critical function of sleep is to prevent
uncontrolled neuronal feedback while allowing rapid responses and
prolonged retention of short-term memories.
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The goal of learning is optimal behavior, and this sometimes requires
the integration of sensory stimuli that are widely separated in
time.
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At a neuronal level, this corresponds to persistent activity in local
networks.
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Unfortunately, when a network exhibits persistent activity, small
changes in the parameters or conditions can lead to runaway
oscillations.
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Thus, the very changes that improve the processing performance of
the network can put it at risk of runaway oscillation.
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To prevent this, stimulus-dependent plasticity should only be
permitted when there is a margin of safety around the current network
parameters.
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We propose that a critical role of sleep is to establish a margin of
safety by exposing the network to a variety of conditions and inputs,
observing for erratic behavior, and -adjusting the parameters
accordingly.
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During wakefulness this margin of safety is gradually consumed,
ultimately requiring refreshment by another period of sleep.
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When sleep is not possible, an emergency mechanism comes into play to
prevent runaway oscillations;
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this is done at the expense of processing efficiency, and constitutes
tiredness.
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We contend that this theory matches the phenomenology of sleep and
tiredness.
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It also makes a number of novel testable predictions.
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