Neural Mechanisms of attention Flashcards

1
Q

Bottom -up Attention

A
  • Stimulus driven control
  • PaVlov= automatically orienting towards salient stimuli
  • e-g.loud bang of balloon
  • involuntary
  • Reflexive attention
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2
Q

Top- Down Attention

A

goal-driven control
- voluntary/ endogenous
- Ability to intentionally attend to something
- Bottom up + Top down attention systems are in balance

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3
Q

overt visual attention

A
  • physically directing eyes to stimulus
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4
Q

covert visual attention

A
  • mental shift of attention without physical Movement
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5
Q

Helmholtz + Covert Attention

A
  • screen of letters hung in dark room + light flashes on screen
  • keep eyes fixed centre
  • During brief illumination could perceive letters located within focus of attention better than those out even when eyes remained fixed on the centre
  • shows we can concentrate attention without eegecvements
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6
Q

Neglect Syndrome

A
  • Indivs with lesions affecting right hemisphere fail to attend to the left side of the world controlesional)
  • Pelligrino - copy clock drawing but squeeze all numbers on the right side
    -Line cancellation test- asked to bisect lines in middle results show they bisect to right + completely miss lines on the left
  • Damage to right parietal cortex
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7
Q

Description of neglect

A
  • stimuli on one side of world is ignored
  • Action less frequently directed to 1 side
  • unilateral spatial neglect results when brains attention network is damaged in 1 hemisphere
  • right hemisphere lesion biases attention towards he right, neglecting the left
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8
Q

Bailints syndrome

A
  • difficulty perceiving visual field as a whole
  • deficit in eye movement to scan visual field
  • Bilateral occipital parietal lesions
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9
Q

Extinction

A
  • Damage to right parietal cortex doesn’t always cause neglect
  • Failure to attend to contralesional hemifield when stimuli appear in ipsilateral hemifield ( side of lesion)
  • ## can attend to left t right sides vision but when themes competition they struggle to attend to the left
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10
Q

Extinction evidence - Posner et al

A
  • cueing task : Cues validly or invalidly indicating location of target
  • Results = fail to reorient attention from invalidly cued locations in good hemisphere to target in bad hemisphere
  • Attentional spotlight (cue ) affects reaction times by influencing sensory + perceptual processing
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11
Q

large-scale network of attention

A
  • neglect is result of damage to brains large scale attention network rather than a single structure
  • Network includes Cortical + subcortical regions that are mono synaptically connected
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12
Q

FMRI scans

A
  • show which areas of the brain are most active
  • strengths = good spatial resolution , non-invasive
  • weaknesses = correlational not causal , expensive, doesn’t directly measure neuronal activity
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13
Q

Evidence from neuroimaging

A
  • ppts complete Posner’s cueing task
  • Results show increased BOLD activity in brain regions during covert shifts of attention
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14
Q

Limited capacity + bottlenecks in attention

A
  • Brain has limited perceptual capacity
  • Bottleneck sensory processing that filters TaSK relevant + irrelevant info
  • Cockail party effect - cherry ( hear name from across party room)
  • selective auditory attention allows you to ppt in a ConVO in a busy room while ignoring other sounds around you
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15
Q

Early models of attention

A
  • Bottleneck filters irrelevant info before complete perceptual analysis ( Broadbent)
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16
Q

late models of attention

A
  • Bottleneck filters irrelevant info after semantic info has been extracted
  • Process all inputs equally + selection occurs at higher stages of processing determining whether the stimuli gains awareness or not
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17
Q

Dichotic Listening studies

A
  • 2 convos, 1 in each ear
  • Attend to only 1 convo
  • Asked if any recollection of the other convo
  • provides evidence for + against both early + late models
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18
Q

Evidence for early models of attention

A
  • Pelligrino
  • people with brain damage suffering with neglect
  • Being unable to attend the left side of space is evidence there is no awareness of stimuus on left
19
Q

Evidence for late models of attention

A
  • Bottleneck filters irrelevant info after semantic info being extracted
  • unattended info isn’t completely lost but is instead degraded (Triesman)
  • Halligan + Marshall presented pprs with picture of 2 houses, 1 was burning
  • found ppts believed the pictures where the same + when asked to choose which they preferred 9/11 chose non-burning
20
Q

EEG/ MEG

A
  • EEG measures neuronal activity over entire brain by electrodes
  • MEG measures magnetic fields associated with electrical fields
  • strengths : high temporal resolution + non invasive, EEG: cheap, MEG: good spatial res
    -Weakness: poor spatial resolution + MEG is expensive
21
Q

Evidence for early models of attention

A
  • Hillyard et al
  • Task attend us unattend stimulus evoked ERP measured by EEG
  • ## Attention acts relatively early in visual processing
22
Q

TMS

A
  • Transcranial magnetic stimulation
  • uses short pulsed magnetic fields to stimulate the brain
  • used to artificially induce brain activity mimicing normal activity or disrupt normal activity (like lesions)
  • Strengths = non-invasive , good spatial resolution + temporal
  • weaknesses = only lateral surfaces on the brain can be studied, effects short- lasting
23
Q

Voluntary visuospatial attention

A
  • visuospatial attention = selecting stimuus un basis of its spatial location
  • can be voluntary or reflexive
  • cortical attention affects:
  • ERP recordings of ppts when asked to covertly attend to stimuli at 1 location + ignore other stimuli
  • Attention modulates amplitudes of sensory - evoked ERP if stimulus is in attended location amplitude is larger
  • Moran Desimone investigated how selective visuospatial attention affected firing rate of neurons in monkeys + when preferred red stimulus was attended = elicited a stronger response
  • spatial attention modulates activity of v4 neurons
24
Q

Biased competition Model

A
  • Desimone + Duncan
  • when different stimuli fall within the Field of a visual neuron the bottom-up signals compete
  • Attention resolves this comp by favouring 1 stimulus
25
Q

investigating Biased CoMp Model- k Sather et al

A
  • fMRI
  • absence of focused spatial attention means nearby stimuli can interfere
  • ## when presenting 2 stimuli simultaneously , neural response evoked by each is reduced compared to 1 stimulus
26
Q

subcortical attention effects

A
  • Attention might influence lateral geniculate nucleus in monkeys
  • vanduffel et al
27
Q

limited perception

A
  • representation of mental experience is constrained by our limited perceptual system
  • can have serious real world consequences
  • Monkey Business illusion video
  • spot difference s eyes flick between them
  • excessive load overwhelms cog processing
  • perception is difficult as need to combine info processed in different areas
28
Q

Adaptive perception?

A

When everything works it is suited to guide adaptive ben
- do not process all stimui in a scene we are quickly able to identify + recognise info according to goals

29
Q

Binding problem limiting perception

A
  • Brain has to bind the info processed in different areas back together to create accurate perceptions
  • Limits of perception are a binding problem
30
Q

solving the binding problem - Biased comp model

A
  • Desimone + Duncan
  • Biased comp model suggests objects compete to drive neuronal responses
    -comp can be biased through bottom-up + top-down mechanisms
  • Attention integrated objects to overcome binding problem
  • Treisman + Gelade-> integration model is solution to binding problem
  • attentional mechanisms biasing neurons activity to a preferred stimulus solves binding problem
31
Q

Single Unit recording

A
  • Method to directly record rate + time of AP
  • strengths : excellent spatial resolution + temporal measures of activity
    weaknesses correlational / can’t capture collective info from a group of neurons. invasive, expensive + time consuming
32
Q

Evidence for biased comp model

A
  • Moran + Desimone
  • Neural activity recorded from visual cortex during visual spatial Attention task
  • stimulus compete to control neuron activity
33
Q

Explaining Biased CoMP Model

A
  • When 2 competing stimuli, non-preferred stimulus is effectively filtered out Of the response
34
Q

Evidence in humans for biased comp model

A
  • Kastner et al
  • stimuli shown sequentially (no comp) or simultaneously (comp)
  • when there’s comp there’s less BOLD activity
  • when told to pay attention to specific stimulus activity is boosted
35
Q

Attention works at different scales

A
  • Attention can adjust its influence on processing depending on the scale of movement
  • Hopf et al
  • When PPts told to attend to small scale movement, VA area was activated but large scale movements s how atention in Lateral Occipital Cortex
36
Q

Feature based attention

A
  • Schoenfield et al
  • when subjects cued to attend to motion activity is enhanced in MT
  • when subjects cued to attend to colour, activity enhanced in V4
  • occurs early in visual processing
37
Q

changes in neural activity + excitability with sustained attention

A
  • Chelazzi et al
  • showed Monkey a cue at begging of trial + asked to pay attention to triangle
  • Across delay neurons show increased in baseline firing
  • poor baseline activity when square present
38
Q

ECOG

A
  • Electrocorticogram
  • Typically performed in patients prior to surgery to treat epilepsy
  • strengths: high spatial + temporal resolution
  • weaknesses: invasive, correlational, limited sampling time, small sample sizes
39
Q

Top-Down control - Barcelo et al

A
  • Damage to PFC alters visual processing
  • PFC lesion patients + controls Attended to targets
  • PFC patients showed reduced visual evoked responses to attended stimuli in visual cortex
40
Q

Microstimulation

A
  • used to induce surrogate neural activity to study how animal ben is affected in stimulated areas
  • strengths : good spatial temporal resolution
  • weaknesses : causal interference method + invasive
41
Q

linking frontoparietal attention control to attentional changes in visual cortex

A
  • Moore + Farrah
  • monkeys perform attention task
  • microstimulation of FED + single Unit recording from V4
  • microstim means better detection of target
  • stim caused in eases in neural activity in v 4 for preferred stimuli
42
Q

ToP down attentional modulation is task specific

A
  • Morishima et al
  • subjects cred to discriminate motion direction or face gender
  • low intensity TMS pulse + EEG recording signals
  • TMS caused increased activity in MT on motion cued trials
  • TMS caused increased activity in FFA on face cued trials
  • Top down attention signals alter activity based on specific task goals
43
Q

Attention: The standard Model

A
  • Attention = prioritisation + selection of info to guide adaptive beh based on goals
  • Top -down signals come from lots of attributes (location, objects, time)
  • sensation -> feature analysis -> object recognition- > contextual integration -> STM-> LTM
44
Q

Visual search Attention

A
  • Triesman
  • Target item can be located more quickly among distractor stimuli if it can be identified by a single stimulus (colour)
    -18 target shares features with distracter the time to determine the target increases