Week 9 Flashcards
Arousal
Global physiological and psychological state
• Asleep or awake but degrees – light sleep or low
arousal
• Also coma, locked-in syndrome, persistent
vegetative state
• Nervous system has to be receptive to stimulation
• Low arousal - poor extraction of information from
environment
Arousal
Transection of the cat brainstem at midbrain level (between
SC and IC) – continuous sleep-like state; transect mid pons
or lower – no effect
• Damage to reticular formation in cats – loss of wakefulness
• Stimulated reticular formation – sleeping EEG immediately
transforms to awake EEG
• Structures in rostral pons and caudal midbrain for arousal
• Ascending arousal system (not reticular activating system –
RAS - since additional structures important eg locus
coeruleus)
Arousal
• Project to virtually every part of the CNS • Dorsal pathway – thalamus to cortex • Ventral pathway – hypothalamus and basal forebrain to cortex
Attention
Attention is NOT Arousal – The What is it?
• Processing resources of the brain are finite
• Not all sensory information is equally important
• Not all thoughts are equally important
Prioritise to make best use of the available
processing resources
Attention
‘Everyone knows what attention is. It is the
taking possession by the mind … of one out of
what seem several simultaneously possible
objects or trains of thought. Focalization,
concentration, of consciousness are of its
essence. It implies withdrawal from some
things in order to deal effectively with others…’
William James
Visual Spatial Attention - Helmhotz
• Screen with letters – dark with brief flash to illuminate • Screen to big to view all without moving eyes • Could decide in advance where to pay attention – even with eyes fixed at centre – and identify letters at centre of attention better than anywhere else
Cocktail Party Effect
• Conversation at a party - selective auditory attention – perceive signal of interest in considerable noise • Dichotic listening task (Cherry, 1953) • Can’t report any detail of unattended ear – best they could report was gender of unattended voice
Attention – Important Concepts
• Selectivity - at any given moment the fixed
perceptual resources can be allocated to different
subsets of information in a flexible way (selective
attention)
• Capacity - the amount of perceptual resources
available for a task or process (varies with the task
and individual)
Attention – Important Concepts
• Overt attention – physically orient toward the
target of attention – head, eyes
• Covert attention – mentally direct attention
without orienting (e.g listen in on a conversation
behind you)
Attention – Important Concepts
• Voluntary attention – intentionally attend to
something – goal driven – internally driven –
endogenous - top-down (e.g. direct your attention
to reading this slide)
• Reflexive attention – external stimulus captures
attention – stimulus driven – externally driven –
exogenous - bottom-up (loud bang; flash of light;
movement in the periphery – recall MSI lecture and
SC)
Attention – Important Concepts
Three components of shifting attention
• Disengagement - attention is normally focused on
some target so to move, must first disengage from the
current target
• Movement - once disengaged, attention is free to move
and must be directed to the new target
• Engagement - after reaching the target, attention must
be re-engaged on the new object or feature
Selective Attention
Prioritise and attend to some things while ignoring
others – allocate resources
How is the brain able to select some information at
the expense of other information?
1. What determines the priority?
2. How does attention influence processing?
3. How is attention allocated?
What Determines the Priority?
• Many things – internal or external • Attend to stimuli relevant to current behaviour and goals • Goal driven; top-down • Endogenous • Top-down shaped by learned priorities from experience and evolution • Attend to salient stimuli • Stimulus driven; bottom-up • Exogenous • Warnings
What Determines the Priority?
• The interface between external environment and internal states (goals, expectations). • Always an interaction between the two states
Posner Cueing Paradigm
• Reaction time task to visual stimuli presented in either
the left or right visual field
• Just before the stimulus appears an attentional cue
appears to direct visual spatial attention either left or
right
• Exogenous cues – flash or similar presented left or right
• Endogenous cues – arrow presented centrally but
pointing left or right
• Combination of valid and invalid trials and usually no
cue trials for control
• Can be covert (keep focus central and respond) or overt
(make a saccade to the target)
Posner Cueing Paradigm
Typical Result Benefit - enhanced processing in the attended area Cost - the unattended area receives less processing
Posner Cueing - Predictiveness
• Endogenous cues must be predictive (say 80% valid
trials)
• In order to use the cue, must anticipate (after
presentation) that it is of value
• Exogenous cues can be non-predictive (i.e. random)
• Involuntary capture of attention regardless of value
• McCormick (1997) found that exogenous cues that
were reliably wrong provided a benefit with the cue
first involuntary capturing attention (to the wrong
place) but then subsequently being used to
strategically redirect attention to the correct place
Posner Cueing - Timing
• Exogenous cuing responses faster to subsequent stimuli at cued location • But only for 50-200ms after cue • After 300ms – pattern of effects reverses – inhibition of return (IOR) • Reflexive – quick but short lived • Voluntary – slower but sustained
Sensory Processing
• Think back to perception being constructed – how does attention influence the construction process? • Metaphors for attention • Spotlight • Zoom • Filter Each has merits Helps with conceptualising But They are all METAPHORS
Spotlight of Visual Attention
• William James (1880s), and Michael Posner (1980s)
• Attention is like a spotlight, it has a focus, a fringe
and a margin
• Illuminating the object in its focus region
• Interference data support this analogy
