Being awake is the opposite of being asleep, in which most external inputs to the brain are excluded from neural processing.
[1][2][3][4] The longer the brain has been awake, the greater the synchronous firing rates of cerebral cortex neurons.
[6] Wakefulness is produced by a complex interaction between multiple neurotransmitter systems arising in the brainstem and ascending through the midbrain, hypothalamus, thalamus and basal forebrain.
[7] The posterior hypothalamus plays a key role in the maintenance of the cortical activation that underlies wakefulness.
[11] It has been suggested the fetus is not awake, with wakefulness occurring in the newborn due to the stress of being born and the associated activation of the locus coeruleus.