--- module: 029-01 language: en chapter: 29 title: "Higher Function, Sleep, Consciousness, and Autonomic Control" module_title: "Foundations" source_sha256: 5a13838993d7133a86bb7cc4811da0a8af5edde03dd522b0ed5f2e83a65ff25b --- # Higher function, sleep, consciousness, autonomic control ## Cortical organisation ### Association regions integrate modalities and time ### Function depends on connectivity as much as tissue #### Strategic lesion disconnects, disproportionate disability ### Hemispheres specialised but cooperative #### Language left-dominant in most people #### Right: spatial attention, prosody, global context #### Dominance probabilistic, so examine, do not assume ## Attention and executive control ### Frontoparietal networks with thalamus and brainstem ### Attention failure degrades every cognitive test #### Poor recall may be failed encoding, not storage ### Prefrontal: working memory, inhibition, rule switching ### Orbitofrontal injury: disinhibition, poor judgement ### Medial frontal injury: apathy, reduced initiation ### Dorsolateral injury: planning, flexibility impaired ### Neglect: failure to attend to one side #### Usually right hemisphere injury, left-sided #### Not explained by primary sensory loss #### Extinction on bilateral stimulation ## Language and symbolic functions ### Non-fluent: effortful output, better comprehension ### Fluent receptive: empty speech, poor comprehension ### Conduction: repetition disproportionately impaired ### Dysarthria: motor execution, language intact ### Apraxia of speech: articulatory planning ### Apraxia: skilled action, not weakness or sensory loss ### Agnosia: failed recognition despite sensation ## Memory systems ### Working, episodic, semantic, procedural memory ### Hippocampal circuits consolidate new declarative memory #### Not a permanent warehouse for all detail ### Retrieval reconstructs, so memory is fallible #### Repeated retrieval strengthens and updates ### Anterograde versus retrograde amnesia ### Frontal: strategies and source monitoring ### Confabulation without deliberate deception ## Emotion, motivation, and stress ### Amygdala detects salience and learns threat ### Dopamine encodes expected versus obtained outcome ### Psychiatric symptoms from many causes #### Brain and mind not competing explanations ## Sleep architecture ### Circadian timing plus homeostatic pressure ### Suprachiasmatic nucleus aligns to light via retina ### Melatonin signals night, not an off switch ### Slow-wave sleep with reduced sympathetic activity ### REM: dreaming, cortical activation, atonia #### Diaphragm and selected muscles spared ### Slow-wave earlier, REM later in the night ### Deprivation impairs vigilance, judgement, glucose #### Subjective adaptation exceeds objective recovery ## Sleep disorders ### Insomnia despite opportunity with daytime effect #### Conditioned arousal outlasts the trigger #### Cognitive behavioural therapy targets arousal, timing #### Sedatives: dependence, falls, respiratory worsening ### Obstructive apnoea: recurrent upper-airway collapse #### Absent sleepiness does not exclude it #### Positive airway pressure, weight, devices, surgery ### Narcolepsy: REM intrusion, cataplexy ### Parasomnias: incomplete state transitions ### Restless legs: urge to move, iron, drugs ## Consciousness and arousal ### Arousal from brainstem, hypothalamus, thalamus ### Coma needs bilateral or arousal-network injury ### First: airway, glucose, toxins, seizures, infection ### Structural focal versus metabolic symmetric signs ### Delirium: acute fluctuating attention failure #### Hypoactive delirium easily missed ### Dementia: chronic decline, may coexist ### Minimally conscious versus unresponsive wakefulness ### Locked-in: conscious, motor output lost ## Autonomic organisation ### Preganglionic neurons use acetylcholine ### Most sympathetic postganglionic use noradrenaline #### Sweat fibres the exception ### Sympathetic and parasympathetic not simple opposites ### Baroreceptors adjust sympathetic and vagal output ### Standing: vasoconstriction, heart rate, muscle pump ### Orthostatic hypotension: volume, drugs, neuropathy ## Autonomic failure and emergencies ### Lying and standing pressure and pulse ### Autonomic dysreflexia after high cord injury #### Bladder or bowel distension triggers it #### Severe hypertension, headache, bradycardia #### Sit upright, remove trigger, monitor #### Missed: stroke, seizure, cardiac injury