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PSCY2020 2019 > Week 9 > Flashcards

Week 9 Flashcards

1
Q

Arousal

A

First - Attention is NOT 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
Transection of the cat brainstem at midbrain level (between
SC and IC) – continuous sleep-like state; transect mid pons
or lower – no effect
• Structures in rostral pons and caudal midbrain for arousal
• Damage to reticular formation in cats – loss of wakefulness
• Stimulated reticular formation – sleeping EEG immediately
transforms to awake EEG
• Ascending arousal system (not reticular activating system –
RAS - since additional structures important eg locus
coeruleus)
• Project to virtually every
part of the CNS
• Dorsal pathway
– thalamus to cortex
• Ventral pathway
– hypothalamus and basal
forebrain to cortex

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2
Q

Attention

A

Attention is NOT Arousal – The What is it?
• Processing resources of the brain are limited
• 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

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3
Q

Attention- William James

A

‘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…’

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4
Q

Visual Spatial Attention - Helmhotz

A 
• 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
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5
Q

Cocktail Party Effect

A 
• 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
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6
Q

Attention – Important Concepts

A

• 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)
• 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)
• 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)

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7
Q

Attention – Important Concepts

Three components of shifting attention

A

• 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

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8
Q

Selective Attention

A

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?

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9
Q

What Determines the Priority?

A

• 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
• The interface between external environment and
internal states (goals, expectations).
• Always an interaction between the two states

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10
Q

Posner Cueing Paradigm

A

• 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)

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11
Q

Posner Cueing Paradigm-

Typical Result

A 
Benefit - enhanced
processing in the
attended area
Cost - the
unattended area
receives less
processing
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12
Q

Posner Cueing - Predictiveness

A

• 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

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13
Q

Posner Cueing - Timing

A 
• 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
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14
Q

Sensory Processing

A 
• 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
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15
Q

Spotlight of Visual Attention

A

• 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
More interference
slower response times
reduced accuracy to targets
Less interference
faster response times
increased accuracy to targets

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16
Q

Zoom Lens of Visual Attention

A

• Attention is loosely likened to a zoom lens on a
camera that has variable spatial scope (Eriksen & St
James, Klein)
• However, the wider the field, the coarser the detail
• Local/global tasks support the zoom lens metaphor

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17
Q

Filter - Cocktail Party Effect

A 
• Dichotic listening task (Cherry, 1953)
• Can’t report any detail of unattended ear
• Proposed attention
results in better
encoding of attended
stimulus / loss of
unattended stimulus
• Processing
bottlenecks
• High-priority
(selected) inputs get
the resources
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18
Q

Filtering

A

• Filtering - early vs late selection models
• Select early
• Why process a bunch of information that will only be
ignored?
• But, how do you know what to select without some
processing?
• Select late
• Without sufficient early processing don’t know what to
select
• But, why bother selecting at all if going to do all the
processing anyway?

19
Q

Selection

A

• Broadbent – information processing system with
limited capacity stages
• But – some information gets through – early not
blocked, only attenuated (Treisman)

20
Q

Evidence for Early Selection

A

• Auditory pathway – two way all the way to cochlear
– attentional gating could be very early
• Hillyard et al (1973)
• Streams of sounds into headphones (dichotic)
• 10% deviant tone – attend to and count deviants in
one ear while ignoring the other ear
• Then reverse ears
Auditory sensory ERPs larger amplitude for attended
ear
Early selection of covert attention
Physiological basis
for the cocktail
party effect
Auditory sensory ERPs larger amplitude for attended
ear
Early selection of covert attention
Physiological basis
for the cocktail
party effect
• Visual spatial attention
• Typical ERPs - P1 (100ms), N1 (180ms) – both larger
in contralateral occipital cortex – early modulation
of sensory processing

21
Q

Evidence for Late Selection

A

• Cocktail party effect – unattended information gets
through
• Endogenous attention can be interrupted by stimuli
• Distractor interference
• Early selection – irrelevant information should have
little influence on perceptual processing
• Late selection - increased interference from irrelevant
information since early processing resources divided

22
Q

Distractor Interference

A 
Two central
targets (H or E)
H – right hand
E – left hand
Irrelevant information slows
responses to the target
Particularly when the
opposite response needs
to be inhibited
• Reaching errors -
changes in trajectory
• Distractor is not a
physical obstacle
• Non-targets evoke
competing
responses
• Inhibitory
mechanisms resolve
this competition
23
Q

Evidence for Late Selection

A

• Distractor interference
• Early selection – irrelevant information should have
little influence on perceptual processing
• Late selection - increased interference from irrelevant
information since early processing resources divided
• Slowed reaction times to targets
• Reduced accuracy to targets
• Changes to trajectories in movements to targets

24
Q

Early or Late Selection

A

• Timing of filter is task-dependent
• Can be early or late
• Filter is a metaphor!!
• Boosting and attenuation of processing of different
stimuli likely occurs throughout the various
pathways/stages leading to conscious awareness
• Salience is important
• Stimulus intensity influences
• Different types of information likely have different
thresholds for activation (e.g. names or motion in the
periphery)

25
Q

Visual Search

A

• How is attention deployed and how do voluntary and
reflexive attention interact when we are looking for
something?
• Distributed vs focused attention
• Distributed attention
• involves parallel processing and visual “pop out”
• visual processing occurs simultaneously over the whole
visual field.
• Focused attention
• involves serial processing.
• selecting a bit of the environment at a time
• visual processing is a series of attentional “fixations” each
covering a different region of the visual field.

26
Q

Visual Search – Distributed Attention

A

Single distinguishing stimulus feature

“pop out” search

27
Q

Single distinguishing stimulus feature

“pop out” search

A

Single distinguishing stimulus feature

“pop out” search

28
Q

Distributed Attention - Distractors

A

Distributed Attention - Distractors

29
Q

Focused Attention - Distractors

A

More than one distinguishing stimulus feature -

conjunction

30
Q

Distributed vs Focused Attention

A 
• Single stimulus feature - independent of number of
distractors (pop out search)
• If not single feature - distractor dependent
(conjunctive search)
• Elementary features
analysed pre-attentively in
parallel
• Focused spatial attention to
integrate features into an
object – deployed
sequential around the field
31
Q

Control Mechanisms

A

• Sensory processing considered the sites of influence of
attention
• Consider now how the focus of attention is controlled
• Anatomy- interacting subcortical and cortical networks
• Superior colliculus and pulvinar (thalamus)
• Frontal, posterior parietal, posterior superior temporal,
anterior cingulate, posterior cingulate, and insula
cortex
• As is common with many systems – information comes
from patients with brain damage that influences the
behaviour of interest
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

32
Q

Three components of shifting attention

A

• 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

33
Q

Control Mechanisms

Three components of shifting attention- DAMAGE

A

• Disengagement - damage to the parietal lobe
(especially the right) results in impaired disengagement
• Movement - damage to the superior colliculus impedes
movement (eye movements are also compromised)
• Engagement - damage to regions in the thalamus
compromises engagement at a cued location

34
Q

• Disengagement - damage to the parietal lobe
(especially the right) results in impaired disengagement
• Movement - damage to the superior colliculus impedes
movement (eye movements are also compromised)
• Engagement - damage to regions in the thalamus
compromises engagement at a cued location

A

• 2 separate frontoparietal cortical systems for
controlling attention – dorsal (spatial attention)
and ventral (non-spatial aspects of attention)
• Systems interact and cooperate
• Parietal central to both
systems
• Dorsal – intraparietal sulcus
and superior parietal lobule
• Ventral – temporoparietal
junction
• Ventral network - stimulus driven attention,
detection of salient targets, reorientation of
attention
• Selectively attending to a region of space and
stimulus appears elsewhere – ventral system
engages
• Alert – interrupt the current attentional focus
established by goal directed dorsal network
• Lesions to TPJ – deficits in disengaging spatial
attention

35
Q

Superior Colliculus

A 
• SC important in orienting
– head and eye
movements
• Reflexive orienting (overt)
to unisensory and
multisensory stimuli
• Certain neurons activated
when attend to location of
stimulus and prepare to
move eyes to the target
• Detect and guide orienting 
• Progressive supranuclear palsy (degeneration of SC
and basal ganglia)
• Difficulty shifting attention
• Slow to respond to cued targets
• Unilateral SC damage
• Reduced IOR for inputs to damaged SC
• Impaired visual search
• Problems with moving attention
36
Q

Pulvinar

A 
• Thalamic nucleus
• Inputs from SC and all over
cortex
• Visual neurons selective to
colour, motion, orientation
• Retinotopic maps of visual
world
• Enhanced activity when
stimulus is target of a
saccade or attended without
eye movement
• Voluntary and reflexive
• Chemically deactivate in monkeys using muscimol
(GABA agonist)
• Difficulty orienting covertly to visual targets in
contralateral visual field
• Impaired at filtering distractions
• Normal subjects – as number of distractors
increases, activity in pulvinar increases
• Pulvinar lesions – problems engaging attention at a
cued location
37
Q

Parietal Cortex

A

• Parietal (frontoparietal networks) involved in much
more than simply disengagement
• Unilateral parietal damage and spatial neglect
• Impaired:
• Disengagement (from ipsilesional stimuli)
• Shifting (to contralesional stimuli)
• Engagement (with contralesional stimuli)
• Capacity limits
• Distributed attention

38
Q

Spatial Neglect

A

• Unilateral (contralateral) - both sides possible but
more persistent and severe with right damage
• Patients do not acknowledge stimuli on the left
• Left regions of space
• Left part of objects
• Left side of body ignored
• Bias rather than complete loss of attention to
neglected field – can direct attention there – like
concentration – if work hard, can attend, but
slightest distraction and gone
• Not visual – map full visual field using single stimuli
• Occurs after damage to one side of the brain (usually the
right hemisphere)
• Patients behave as if the affected side of space (the
contralesional side) has ceased to exist
• ignore food on one side of their plate
• fail to shave/make-up one side of their face
• bump into objects on one side
• fail to read text from one side of the page – or one side of word
• Most common and severe after damage to the parietal lobe
(but can arise from cortical and subcortical damage
elsewhere)
Frequently following stroke
involving the middle cerebral
artery (MCA)
MCA patients with (a) and
without (b) neglect
Critical regions – angular gyrus,
parahippocampal gyrus

39
Q

Spatial Neglect- examples

A 
Image copy
Spontaneous drawing
Line bisection
Gaze bias – eye
tracking
At rest (light grey)
Searching for a
target letter (dark
grey)
40
Q

Unconscious processing

A

Are the houses the same or
different?
In which house would you
prefer to live?

41
Q

Mental Imagery

A 
Neglect not
restricted to the
physical
environment
Internal
representations
also impaired –
but NOT memory
42
Q

Visual Extinction

A
  • Preserved detection of single contralesional left-sided stimuli
  • Better detection of left events when allowed to ignore right events
  • Better detection of left events when they are presented earlier than right events
  • Not visual
43
Q

Right Dominance

A 
Attention vector
deployed mostly from
right hemisphere to left
hemispace, but some
deployed within same
(right) hemispace
Attention vector from
left hemisphere
deployed to right
hemispace

PSCY2020 2019 (18 decks)

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