Attention 1 Flashcards
Describe the perception-action cycle
Processing goes from low to high level sensory cortex (hierarchical processing) to extract ever more meaningful features from the environment. These are then translated to motor outputs in a reverse hierarchy, going from abstract motor commands to the activation of –eventually -muscles (that in turn will influence the environment).
What problem is posed by this perception-action cycle?
You cannot translate every sensory input into a motor output-which sensory inputs are selected for action?
In what experiment is this problem highlighted? Describe this
A simple Dichotic Listening experiment with shadowing shows the limits of the perception action cycle. Subjects hear two different auditory streams in the two ears. They can only reproduce (and remember etc) one stream at a time: the stream they attend to.
What does this then suggest that the main function of attention is?
There is limited capacity in going from perception to action (or memory etc). The core function of attention is therefore selection.
What two types of attention are presented in the visual domain?
Overt and Covert attention
Overt orienting and attending- Moving your eyes, body, ears, nose etc in the direction of a relevant stimulus (superior colliculus)
Covert attention- shifting your attention towards something, without any external , overt signs i.e while maintaining fixation.
What is significant about the mechanism of covert attention?
This mechanism has evolved particularly in social animals, in which direction of gaze often has strong meaning (threat, aggression, sexual attraction)
How can covert attention also exist in the auditory domain?
One may pretend to listen to someone in front of you, while actually focusing on what is said in another conversation. (cocktail party effect)
If, while talking to someone you suddenly hear your name in a conversation you weren’t listening to, what do you call this?
BEEF
Nah, attentional capture; while listening to the person in front of you, your attention may be suddenly captured by someone saying your name in another conversation
What four different types of attention are described in the lecture?
=> Top-down attention/ Voluntary attention
=> Capture attention/ Bottom-up attention
=> Object based attention
=> Feature based attention
How is top down attention often studied?
subjects are instructed to focus their attention on some location of the visual field (such as in the Posner cueing task).
What behavioural effect is often observed during these Posner Cueing tasks?
The behavioral effect typically is that reaction times to presented targets are faster at the attended location.
How is bottom up attention often studied?
A suddenly appearing stimulus will automatically ‘capture’ attention. A prime is usually given before and reaction time is recorded in reporting where the cue was located
What are often the results of these experiments on bottom up processes?
Shorter reaction time to primed location. This is true even when subjects are told that the prime will have no bearing on where the actual target cue will be or that it will be mostly invalid. (this shows that it is automatic and not ‘top-down’
What subsequent addition effect can this initial attention capture have during these studies and when does it occur?
Attentional capture transforms into ‘inhibition of return’ when the temporal interval between prime and target > 300 ms. Now, reaction time is longer for the cued location. The subject starts to actively suppress attention to the location of the (mostly invalid) cue.
Describe two examples which demonstrate object based attention
When two parallel rectangles are shown and stimulus C is primed at the end of one, this leads to faster detection of S at the other end of the rectangle than D at the same side of the opposite rectangle despite them being the same distance. This is true even when another perpendicular rectangle is place across both, in between C and S.
Also attention can be directed towards objects that overlap in space (e.g the opaque house and moving face in front)
How could it be argued that these overlapping images do not inhabit the same ‘space’?
Is spatial attention simply spreading faster along objects, and can spatial attention also work in 3-D?
What other clever experiment using disparity was used to study object based attention?
Critical manipulation was used to have white lines either appear (in 3D against a correlated dot background) as two separate lines in front of random dots, or as one white background visible behind slits in the dots.
one of two white lines was cued, and then targets where shown on either the same location (valid), on the same white line (invalid within) or the other white line (invalid between).
What were the results of this experiment on object based attention using disparity?
A difference in reaction time between invalid targets on the two lines was only observed when they were percieved as different objects, not when perceived as a single background surface, proving the existence of object based attention.
What example demonstrates feature based attention?
Shorter reaction times to (objects with) features attended (green circle among green squares and red both)
What is observed about top-down attention from electrophysiological recordings?
The effect is an enhanced response to a stimuli that appears at the attended location. The Posner cueing task increases the amplitude of visual evoked potentials recorded from the human scalp.
What is significant about the location of the stimulus and the areas of the brain which shows activation?
This enhanced response is specific for the attended location (so it is not a general or overall increase in neural responsiveness). The P1 attention effect is topographically distributed over the visual cortex in accordance with the location of the visual field where attention is directed at. (see docs)
How does EEG relate to attentional capture?
Attentional capture has a similar effect on neural processing: an increased response for stimuli at the cued (or rather captured) location. Inhibition of return results in a decreased response at the cued location, in accordance with the now decreased attention at that site.
These effect of capture (and inhibition of return) again show spatial specificity, in that they occur only at the cortical locations where the attention is directed to (drawn away from)
What is observed in monkey area V4 during attentional capture?
In monkey area V4, there is an increased response when attention is directed towards the preferred stimulus (Desimone). Spatial attention causes increased signals.
How are these electrophysiological responses different to that of attention to a feature?
Attention to a feature(direction of motion) enhances responses to that feature all over the visual field (Treueet al., 1999): Feature based attention causes increased signals of attended features.
