lecture 2- noradrenaline, acetylcholine and alertness

Question 1

the brain stem and thalamus

Answer 1

• basic behavioural functions: sleep/wake cycle, reflexive response to sensory input

Question 2

ascending reticular activating system (ARAS)

Answer 2

• axons of ARAS project from brain stem to higher cortical regions (incl via thalamus)
• source of major excitatory neurotransmitters: noradrenaline (NA) and acetylcholine (ACh)
• regulates general levels of cortical arousal, alertness and consciousness
• Eysenck (1967) suggested a link between ARAS and extraversion: extraverts have low ‘resting’ ARAS activity (so they seek out more stimulation); introverts have high ‘resting’ ARAS activity (so they avoid overstimulation)

Question 3

anterior and posterior attention systems

Answer 3

• two attention systems in the cortex
• anterior (frontal) system= ‘top down’ (cognitive), voluntary, controlled, task-or goal driven attention, ‘executive functions’
• posterior (parietal) system= ‘bottom up’ (sensory), involuntary, automatic, stimulus driven attention, ‘orienting reflex’

Question 3

rough definition of alertness

Answer 3

• generalised readiness to process stimuli and respond. measured by subjective feelings or simple psychomotor tasks

Question 4

rough definition of attention

Answer 4

• enhanced processing of specific/selected stimuli. measured by behavioural performance - eg RT/accuracy

Question 5

rough definition of arousal

Answer 5

• physiological activation in autonomic nervous system (eg skin conductance) or central nervous system (using EEG, fMRI, ect); sleep/wake cycle

Question 6

what is Vigilance (or continous performance) tasks and what can be measured

Answer 6

• respond only to pre-specified target stimulus/sequence (eg “only respond to X” only respond if same letter is presented twice in succession”.)
• targets are rare (eg. 5% of trials); presentation is rapid
• requires sustained attention (=vigilance) and is more cognitively demanding than simple RT task (eg additional demands on working memory and response inhibition); involves anterior system

measures: average RT to targets, errors of omission (missed targets) and errors of commission (false alarm; responding to non-targets)

Question 7

how is one way alertness and attention measured?

Answer 7

simple detection / reaction time tasks

eg “press when you see the X”
- mean RT depends on average alertness during task (tonic alertness)

eg “press when you see the X; the dot will warn you that its about to appear”
- mean RT depends on temporary increase in alertness following warning cues (phasic alertness)

Question 8

psychopharmacology of alertness

Answer 8

• drugs that increase alertness/ arousal are called stimulants- examples include caffeine, nicotine, amphetamines and methylphenidate (Ritalin)
• these drugs mimic or enhance the effects of noradrenaline and /or acetylcholine in the brain- ie they are noradrenergic or cholinergic agonists
• drugs that reduce alertness/ arousal are sedatives- examples include GABA agonists , noradrenergic beta-blockers & cholinergic antagonists

Question 9

Noradrenaline