Attention I Flashcards
selective attention
covert process that allows individuals to select and focus on a particular input while simultaneously suppressing irrelevant or distracting information
2 forms: voluntary + involuntary
overt attention
attention same location as the eyes
covert attention
attention different location than th eyes
Endogenous attention
top-down, intentional, goal-oriented
Exogenous
bottom - up, reflex
Limited attention
can’t pay attention to everything
Inattentional blindness
can’t see shit when concentrated on something
Change blindness
can’t see an obvious change
reticular nucleus
sheet around the thalamus, Can gate information = high arousal (excitement) or block information = low arousal (drowsiness, sleep)
Reticular fomration
in the brainstem regulates excitability of the reticular nucleus perméability
Different theories
early selection theory
late selection theory
attenuation theory
conclusion: flexible theory
Early selection theory
we select what we want to attend to very early on and ignore unattended info
no higher-level semantic processing.
This implies that the effects of attention should occur early in the visual/auditory
system and non-attended stimuli should not reach higher brain region
Effects of attention should occur
early in the visual/auditory system and non-
attended stimuli should not reach higher
brain regions.
proof: dichotic listening tasks
problem: cocktail party effect
dichotic listening task
two different sound stimuli are presented to each ear, the subject is instructed to only attend to one ear
- Can identifiy: change of gender, whether human or robot in the unattended ear
Can’t identify: change of language, if the same word is repeated over and over
cocktail party effect
people are able to pick out their names in from the unattended stimuli = implying higher level processing of some unattended stimuli
Late selection theory
selection occurs after some higher-level semantic processing
Effects of attention occur late in
the visual/auditory system and non-attended
stimuli can reach higher brain regions.
Attenuation theory
combination fo both theories
Some non-attended information can reach higher levels, but is attenuated. Only salient information (one’s own name) is fully selected.
early or late selection depends on the amount of attention given to a stimulus
So a lot of attention = early selection
§ Difficile tasks
§ When you know to what to attend to such as specific colour
§ Weaker neural responses??
○ Low attention: late selection
§ Stronger neural responses
§ Easy tasks
§ When you don’t know what to attend to = don’t know the colour your friend is wearing so you gotta attend to everything
Auditive attention
effects of attention can be seen P20-50 : 20-50 milliseconds after stimulus = 20-50 ms on EEG
see on fMRI: we see that attention modulates primary auditory cortex activity, but not subcortical structure
Visual attention
effects of attention can be seen P100 : 100milliseconds after stimulus = reaction time is 100ms on EEG
on fMRI: attention modular’s primary visual cortex activity and even subcortical structures LGN
Posner cueing task (endogenous variant)
= allows to study attention behaviourally , with a spatial task
2 variants: exogenous and endogenous variants
Endogenous variant
- 3 conditions : valid cue, invalid cue, neutral cue
Important facts:
- participants can choose to use the cue or not
- vue validity matters: if the arrow is not predictive of where the target will appear, people stop using the arrow
It takes time before attention can be moved: people need at least 200ms to move attention to the left or the right. If there is less between cue and target: no cueing effect
Behavioural results:
- Valid cue : RT is faster accuracy is higher (compared to the neutral condition
- Invalid cue: RT is slower, less accurate compared to neutral condition
- effects only present if there is AT LEAST 200ms between cue and target presentation
- effects are only present if cue validity is high enough, at least 70% of the time.
Posner curling task (exogenous variant)
2 conditions:
- valid cue: flash of light appears at location where target is going to appear
- invalid cue: flash of light appears at the other, non-target location
3 important facts:
- participants have NO choice to choose the cue or not: cue forces attention involuntarily to move ether left or right
- cue validity does not matter: even if cue is not predictive of target location, attention is still pulled tot he location of the cue
- cue target timing determines attentional effects: works best when less than 200ms, then it’s the opposite?: the valid cue effect changes from a benefit performance decrement if there is more than 200 ms between cue and target = inhibition of return
Results
Valid cue: RT faster, accuracy higher
Invalid cue: RT slower, accuracy lower
cue <200ms: fast, ventral stimulus driven attention network for those first 200 ms
if not: inhibition of return: after 200ms: slow, dorsal, top-down attention network
Inhibition of return
suppression of processing of stimuli that had recently been the focus of attention: if more than 200 ms between cue and target
Attentional blink test
Letters are shown in a rapid succession with two targets, and must detect when the targets appear: T1= first target, T2= second target
Results:
T1 is accurately reported
T2 is accurately reportes if directly following T1, or more than 350ms between T1 and T2
Low accuracy for T2 id it is presented between 250-350 ms after T1 = attentional blink
(T2 is dropped only if T1 is asked. If T1 is ignored, than T1 blue line becomes T2)
Attentional Stream Paradigm (dichotic listening)
Using EEG, even the earliest subcortical signals can be studied ( brainstem evoked potentials, BERs) can be studied
As we can see, attention has no influence on auditory processing in subcortical structures : attention references to whether there is a difference in the evoked potentials depending on the ear that is attended to
Subjects must detect tones that deviate :
- very first moment information arrives in primary cortex: first effects of attention: p20-50:
- 100ms: N1 effects of attention in which the entire auditory cortex is engaged
but no difference between normal and deviant tones in these early ERP
Early selection: p20-50 and N1 same for all stimuli
Late selection: P300: amplified for deviants compared to standard dev
so P300 enhanced only for deviants IN THE ATTENDED EAR, indicting that deviants in the unattended ear are filtered out (evidence of early selection)
MMN
MMN
MMN peaks frontally within 150–200 ms poststimulus in auditory stream paradigm
present in the attended and unattended ear : late selection
But AMPLIFIED in attended ear : early selection
P300
Late components of attention, amplified for deviants
Covert Spatial attention measured by EEG
- if spatial attention is at the correct location when target hits: larger P1 ( 100ms after stimulus onset) and larger N1 (180ms after stimulus onset)
What do P1 and N1 reflect in visual attention
P1: reflects V1, V2, V3, V4 activation
P1; reflections visual and parietal regions
Covert spatial attention measured by fMRI
fMRI can measure all visual regions
Attention towards a location enhances neural activity, also apparent when attention is directed to two locations at the same time
Attentional effects even in LGN(. but why is it different from the auditory system?)
There is biased competition within the receptive fields
Refs become larger when going up the visual hierarchy
Multiple objects can fall within the RF of a reunon, this may produce competition for representation among objects: effective stimulus vs ineffective stimulus
If both effective and ineffective stimulus fall within the RF of the neuron= there is competition
Activity is therefore the average response to effect and ineffective stimuli
If attention is porté towards the effective stimuli: the firing rate is high, neurons act as if only the effective stimulus was in the RF
same goes with ineffective stimuli, the firing rate is low, neurons act as tho only the ineffective stimuli was in RF
THEREFORE attention resolves competition within RFs
Effective stimulus for a neuron
the preferred stimulus, producing strong activation
Ineffective stimulus for a neuron
the non-preferred stimulus for a neuron, producing weak activation
V4
colour-sensitive visual cortical area
V5
motion-sensitive visual cortical area
Difference between easy task and difficult task seen on EEG
while asked to perform an easy task, the irrelevant information about motion (activated by V5) shows activity : taking in irrelevant info : late selection
while asked to perform a difficult task the irrelevant info about motion does not show activity : early selection
MMN, when , what, where, evidence for which theory
150–200 ms after occurrence of stimuli
related to perceptual discriminability
Attention amplifies the magnitude of the MMN: evidence for late selection
•at least some meaning is processed in the unattended ear
