Neural Mechanisms of attention Flashcards
(43 cards)
1
Q
Bottom -up Attention
A
- Stimulus driven control
- PaVlov= automatically orienting towards salient stimuli
- e-g.loud bang of balloon
- involuntary
- Reflexive attention
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
3
Q
overt visual attention
A
- physically directing eyes to stimulus
4
Q
covert visual attention
A
- mental shift of attention without physical Movement
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
6
Q
Neglect Syndrome + studies
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
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
8
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
9
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
10
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
11
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
12
Q
Evidence from neuroimaging - covert attention
A
- ppts complete Posner’s cueing task
- Results show increased BOLD activity in brain regions during covert shifts of attention
13
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
14
Q
Early models of attention
A
- Bottleneck filters irrelevant info before complete perceptual analysis ( Broadbent)
15
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
16
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
17
Q
Evidence for early models of attention - neglect
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
18
Q
Evidence for late models of attention - bottleneck + degraded info
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
19
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
20
Q
Evidence for early models of attention - EEG
A
- Hillyard et al
- Task attend us unattend stimulus evoked ERP measured by EEG
- ## Attention acts relatively early in visual processing
21
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
22
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
23
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
24
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
25
subcortical attention effects
- Attention might influence lateral geniculate nucleus in monkeys
- vanduffel et al
26
limited perception
- 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
27
Adaptive perception?
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
28
Binding problem limiting perception
- Brain has to bind the info processed in different areas back together to create accurate perceptions
- Limits of perception are a binding problem
29
solving the binding problem - Biased comp model
- 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
30
Single Unit recording
- 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
31
Evidence for biased comp model
- Moran + Desimone
- Neural activity recorded from visual cortex during visual spatial Attention task
- stimulus compete to control neuron activity
32
Explaining Biased CoMP Model
- When 2 competing stimuli, non-preferred stimulus is effectively filtered out Of the response
33
Evidence in humans for biased comp model
- 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
34
Attention works at different scales
- 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
35
Feature based attention
- 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
36
changes in neural activity + excitability with sustained attention
- 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
37
ECOG
- 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
38
Top-Down control - Barcelo et al
- 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
39
Microstimulation
- 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
40
linking frontoparietal attention control to attentional changes in visual cortex
- 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
41
ToP down attentional modulation is task specific
- 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
42
Attention: The standard Model
- 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
43
Visual search Attention
- 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
