26 - C. Brain activity

C. Brain activity

© SPMM Course  Reduced recall of dreams if awaken. (Sleep terror is an NREM disorder. When awake after sleep terror episodes, children appear confused and do not recall what terrified them). REM sleep o 25% of adult sleep is REM. Darting eye movements are noted in REM despite other muscles being paralysed. REM sleep is characterized by a high level of brain activity and physiological activity similar to those in wakefulness. o In REM sleep behavioural disorder, muscular paralysis does not occur resulting in violent movements coinciding with brain activity. o EEG shows low-voltage, mixed-frequency (theta and slow alpha) activity similar to an awake state. Sawtooth waves are also seen. o In a typical night, a person cycles through five episodes of non-REM/REM activity. The REM episodes increase in length as the night unfolds. o Features of REM sleep:  Increased sympathetic activity (increased heart rate, systolic blood pressure, respiratory rate, cerebral blood flow)  Autonomic functions are active with penile erection or increased vaginal blood flow  Increased protein synthesis  Maximal loss of muscle tone with occasional myoclonic jerks  Vivid recall of dream if awaken. (Nightmares occur in REM sleep – hence they are well recollected). C. Brain activity Apart from various oscillatory patterns, some specific patterns of electrical activity are also noted during sleep.  Sleep spindles  Waves with upper alpha or lower beta frequency, seen in many stages but especially in stage 2. The waveform resembles a spindle with an initial increase in amplitude that decreases slowly  Duration usually <1second.  They usually are symmetric and are most obvious in the parasagittal regions.  K complex:  K complex waves are large-amplitude delta frequency waves, sometimes with a sharp apex.  They can occur throughout the brain but more prominent in the bifrontal regions.  These may be mediated by thalamocortical circuitry.  Usually symmetric, they occur each time the patient is aroused partially from sleep.  Semiarousal often follows brief noises; with longer sounds, repeated K complexes can occur.  Runs of generalized rhythmic theta waves sometimes follow K-complexes; this pattern is termed an arousal burst.  V waves:  V waves are sharp waves that occur during sleep. They are largest and most evident at the vertex bilaterally and are usually symmetrical.  Multiple V waves tend to occur especially during stage 2 sleep.