--- module: 029-02 language: en chapter: 29 title: "Higher Function, Sleep, Consciousness, and Autonomic Control" module_title: "Network cognition, sleep-state control, and disorders of consciousness" source_sha256: 83c07eb7c23002e190def0afe2b4c7b9899ff114aaea2aec47c5acbb0d011840 --- # Network cognition, sleep-state control, consciousness ## Network approach and attention ### Poor memory: attention, consolidation, retrieval, output #### Identify failed operation, time course, network ### Alerting, orienting, executive attention systems ### Dorsal frontoparietal: goal-driven attention ### Ventral salience: interrupts for important stimuli ### Thalamus regulates access and synchronisation ### Right parietal lesion: profound left neglect ### Test arousal and attention first #### Digit span, months backward, consistency ## Executive control ### Prefrontal cortex coordinates a wider network ### Perseveration, impulsivity, poor sequencing ### Can describe steps yet fail to organise them ### Shaped by fatigue, medication, mood, environment #### Quiet examination underestimates daily disability ## Declarative memory ### Hippocampus binds elements of an episode #### Gradual integration into cortical representations ### Bilateral medial temporal injury: severe amnesia #### Immediate span and motor skills relatively spared ### Frontal disease: organisation and free recall #### Cueing or recognition improves performance ### Depression, pain, sleep loss, delirium imitate ## Language assessment ### Fluent speech is not necessarily meaningful ### Test comprehension without contextual clues ### Repetition vulnerable to several network lesions ### Naming failure: semantic, word form, or motor ### Acute aphasia is a stroke warning ### Reliable yes-or-no channel prevents misclassification ## Arousal and the sleep-wake switch ### Multiple ascending transmitter systems #### No single transmitter is a switch ### Wakefulness is a stabilised network state ### Cortical failure removes awareness, brainstem arousal ### Ventrolateral preoptic neurons inhibit arousal ### Orexin stabilises wakefulness #### Loss underlies narcolepsy type one #### Sleep attacks, cataplexy, sleep paralysis ### Adenosine builds sleep pressure #### Caffeine antagonises adenosine receptors ### Circadian alerting opposes pressure: second wind ## Sleep states and sleep disorders ### REM: pontine suppression of motor output #### Failed atonia permits dream enactment #### May precede synuclein neurodegeneration ### Sedation is not physiological sleep ### Obstructive apnoea: collapse, hypoxaemia, surges #### Fragmented sleep, rising cardiovascular load #### Severity beyond event count #### Airway pressure success needs fit and follow-up ### Insomnia maintained by more than low sedation #### Bed conditioned as a cue for vigilance #### Excess time in bed reduces sleep pressure #### Abrupt sedative withdrawal needs planned taper ## Disorders of consciousness ### Stabilise and localise in parallel #### Correct hypoxaemia, glucose, pressure, opioids ### Pupils, eye movements, corneal reflex, breathing ### Unilateral dilated pupil: third-nerve compression ### Glasgow Coma Scale is not a full examination #### Components and trend beat an isolated total ### Non-convulsive status needs electroencephalography ### Reassess with same stimulus and same scale ### Locked-in: seek eye movement or blink channel ## Delirium and dementia ### Acute change, fluctuating attention and arousal ### Hypoactive delirium mistaken for cooperation ### Treat causes, protect orientation and sleep ### Antipsychotics do not cure delirium ### Dementia increases vulnerability ### Family accounts of usual state are central ### Restraint and catheters reinforce the cycle ## Autonomic control and orthostasis ### Symptoms when cerebral perfusion falls ### Volume depletion: heart rate rises ### Neurogenic: small heart-rate rise #### Sympathetic efferent failure ### Measure after supine rest, continue standing ### Treat by mechanism: drugs, volume, counter-pressure #### Salt and fluid unsuitable in heart or kidney failure #### Volume or tone drugs: supine hypertension ### Goal is function, not a perfect pressure ## Safety and final assessment ### Driving, machinery, bathing, heights ### Share warning changes and emergency criteria ### Diary links symptoms to time, posture, medicines ### Name the unstable state transition or loop