Attention Flashcards
What is attention?
Mechanism of selection
- selects external sensory items of interest
- to receive further processing AND internal thoughts and memories
(“trains of thought” - William James)
What is the consequence of pathological alterations in attentional selection?
> Attention shapes conscious processing
> Anxiety or depression
- consciously attending more readily towards negative stimuli
- your conscious environment is more negatively valent than those without those biases
- > negative repercussions in daily life
What is automatically selected by attention?
Attention-grabbing items
- automatic allocation of attention towards sudden or salient items
= adaptive mechanism
What is the effect of novelty or change on attention?
> New information -> we want to process it in greater detail
> Visual changes cause transient (short-time) motion when occurring
-> automatically reallocates attentional ressources to the position of that change
What does the “spotlight” metaphor refer to?
Selective attention process “lights up” part of the sensory input
- enhanced processing of the selected visual input
What are the two methods of attention selection according to Posner (1980)?
- Exogenous (bottom-up) attention
- auto-allocation based on properties of stimuli - Endogenous (top-down) attention
- not automatic, you consciously choose to pay attention
- relevant and interesting items though not necessarily salient
What are Posner’s paradigms (1980)?
Exogenous/endogenous spatial cueing paradigms
- widely used across huge number of permutations, and in different clinical groups
When using Posner’s cueing paradigms, what are the results observed in valid and invalid trials? Why?
> Valid trials:
- over numerous trials, lower reaction times
- because their attention bias has been correctly cued to target position
- > enhances performance
> Invalid trials:
- over numerous trials, higher reaction times and more errors
- because attention cued to opposite direction of target
What is the difference of performance between endogenous and exogenous attention paradigms when there are many invalid trials (e.g. 40% valid, 60% invalid)?
> Endogenous paradigm:
- cue appears at the center
- > invalid trials are harder to ignore
> Exogenous paradigm:
- attention grabbed by cue appearing on the side
- > invalid trials harder to ignore
What are the two types of searches in the visual search paradigm?
> ‘Parallel’ or ‘pop out’ search (or “preattentive”)
- looking for unique target (shape, letter, faces)
> Serial search
- taret differs from a conjunction of 2 or more features from distractors
What is the “set size” in the visual search paradigm?
Number of distractors
Why does the set size not matter in a parallel search condition (visual search paradigm)?
Target pops out from distractors
- because the distractors differ from target in one fundamental dimension (orientation, colour)
- you don’t need many cognitive resources and don’t have to search through all distractors
Why is the set size positively correlated to the participant’s reaction time in a serial search condition (visual search paradigm)?
2 or more differing features between targets and distractors
- to find a unique target, you have to search through all items
- it requires more attentional resources
- if target is similar to distractors, or if participants have been selected to find a particular target, search slope will be steeper
- as reaction time rises quickly with number of distractors
What happens to items we do not pay attention to?
They are filtered out
How did Rees and colleagues (1999) demonstrate how attention enables us to filter out information even if it’s presented right in front of your eyes?
> When attending real words (green letter stream)
- brain activity in left hemisphere (language)
- minimal activity in right hemisphere
> Measure of BOLD signal
- when letter stream not attended (participants focus on pictures) -> no word-related processing
- no differences of activity between real words and meaningless letter strings
-> even though the words are presented at fixation, if they’re not attended, we don’t process them
Which phenomenon did the study of Rees, Russel, Frith and Driver (1999) underline?
Inattentional Blindness
- when we don’t pay attention, we can be effectively blind even to salient visual stimuli
What does inattentional and change blindness demonstrate?
> If your attention is manipulated/distracted, you remain effectively blind to visible key salient stimuli
-> link between attention and awareness: to see something you need to actively focus your attention to it
> Studies have revealed that people often fixate the relevant parts of images (i.e. item arrives in V1)
BUT by not paying attention to it, you’re unaware of it
What is sustained attention?
Paying attention to the same item for a sustained period of time
What are the neural effects of sustaining attention over time (Pardo, Fox and Raichle, 1991)?
Using PET to examine blood glucose use in the brain in relation to particular tasks
> Parietal cortex involved for all tasks whether tactile or visual
> Involvement of right and left hemisphere was not equal: for lateralised stimuli (toes):
- left toe -> right parietal activity
- right toe -> few left parietal activity BUT also right parietal
=> Right parietal cortex crucial in sustaining attention across time
- true of selective attention too
What is the network of attention in the brain?
Right hemisphere:
- Dorsal and more ventral parietal regions
- Some areas in frontal cortex
What happens in cases of damage to right parietal regions?
Visuo-spatial neglect
- patients neglect the left (contralesional) side of visual field
- they are blind to items they can’t select (neglected items)
- > attention-awareness link
What happens to the visuo-spatial neglect of patients who had a stroke on the left hemisphere?
Evidence shows their neglect resolves very quickly
- because these areas are not crucial for attention (vs. right parietal regions)
What does the ipsilesional side refer to?
Side of visual field that is on the same side of damaged hemisphere
Which tasks are used to measure the patients with visuo-spatial neglect?
> Line bissection task
- mark the middle of a horizontal line
> Cancellation task
- cancel out all of one type of stimuli
> Drawing
What is observed in the drawing task for patients with visuo-spatial neglect?
> Ipsilesional side is completed very well but contralesional side is not completed at all
> Patients aren’t aware of there being any missing elements on the left (contralesional) hand side
What did the representational neglect task show?
Mentally shifting so different sides were on the ipsilesional side
- participants had not forgotten what was in the square (mental image of city)
- BUT they were unable to be aware of it when those part of the mental image fell into impaired contralesional side of space
How did Marshal and Halligan (1995) demonstrate an unconscious processing in patients with visuo-spatial neglect?
“Which of these houses would you live in?”
- patients unaware of the flames coming out fo left window of burning house
- yet, they always chose the house without the flames coming out of the (not burning) house
-> some residual, unconscious processing in these patients
= implicit detection of threat
What is the implicit contralesional processing for emotional stimuli?
Body of evidence suggesting that when emotionally threatening stimuli are presented on the neglected side, there is some residual processing
(cf. implicit detection of fear, Marshall and Halligan, 1995)
How did Vuilleumier and Schwartz (2001) demonstrate the implicit contralesional processing for emotional stimuli?
> When patients with neglect are presented with bilateral stimuli
- if sides are on the left they were detected much more frequently then if flowers were on the left
-> emotional intensity (threatening nature of stimuli) enabled preserved processing -> stimuli consciously detected
> Similar processing on the left side demonstrated for faces with emotional expressions
