Attention
or selective attention—is the process of selecting or focusing on one or more stimuli for enhanced processing and analysis.
Arousal
is the global level of alertness in an individual. This would enhance processing and analysis of ALL stimuli, without preferences.
Forms of attention
- Overt attention= the focus coincides with the sensory orientation.
- covert attention= focus is independent of sensory orientation
Cocktail party affect
selectively enhanced attention to filter out distracting stimuli. (And this effect is made worse by alcohol consumption!)
if two stimuli in each ear, cannot recall any in nonattended ear
Dichotic presentation
simultaneous delivery of different stimuli to both ears at the same time.
Shadowing
In dichotic presentation, shadowing is the task requiring the participant to focus and repeat the stimulus from one ear
Innattentional blindness
Inability to perceive stimuli when focused on one set of stimuli
gorilla in a passing game
Divided attention tasks
subjects are asked to process two or more simultaneous stimuli.
These tasks show that attention is a limited resource.
Attentional spotlight
part of environment highlighted for enhanced processing of stimuli, constatly shifting
Models of attentional bottleneck
Early-selection model
- higher-order cognitive processes can exclude nonattented stimuli before processing
- stimuli -> sensory registration -> Attentional Bottelneck -> perceptual analysis -> awareness
- some unattendted stimuli can be processed (name)
late-selection model
- bottleneck occurs later after some processing has occured
- stimuli -> sensory registration -> perceptual analysis -> Attentional Bottelneck -> awareness
- supported by Stroop task
combo models
Stroop task
- read a written color with a font of a different color, very hard
- information as it comes in has some meaning even before filtering
- irrelevant information interferes with target stimuli at a semantic level
- accurate attention must involve late attentional selection
Perceptual load
- immediate processing challenge presented by a stimulus.
- attention creates balance between early and late selection according to task difficulty
Endogeneous v. Exogeneous attention
Endogeneous attention
- voluntary
- from within
- top-down
- slower, but maintained
Exogeneous attention
- reflexive
- stimuli grabs attention
- bottom-up
- rapid, fades quickly
both work together and coordinate to analyze surroundings
Symbolic cuing task
- An endogenous attention task in which each trial is pre-ceeded by a symbol that cues the location where the stimulus will appear.
- may be valid or invalid cues
- reaction time averaged and compared with neutral cues (no location information)
- Subjects quickly learn to use the cues to predict stimulus location, shifting their attention in the cued direction, without shifting their gaze, in anticipation of the appearance of the target stimulus.
- INVALID > NEUTRAL > VALID for reaction time
Peripheral spatial cuing task
- precedes target stimulus with irrelevant stimulus in same location as one of traget stimulus options with a delay
- measures latency to detect visual stimulus
- valid exogeneous cues decrease reaction timeif short delay
- valid exogeneous cues increase reaction time if long delay
- reaction time=stimuli processing
Inhibition of return
reluctance of attention to move to a location it has just visited, especially after a delay
causes a valid exogeneous cue to actually increase reaction time on a peripheral spatial cuing task when a long delay has occured
Types of visual search
- feature search= search in which target pops out right away due to unique attribute
- conjunction search= search based on two or more features which distinguish the target
feauture search reaction time unaffected by number of other items, but conjunction search reaction time directly proportional to number of other items
Feature integration theory
conjunction searches use attentional shifts to coordinate feature maps (overlapping maps of the searched array, with each map focused on one particular stimulus attribute like color, shape, etc.).
ERPs on attention
Auditory
- Comparison of the representation of sounds on each ear with whether the subject attended to them or not
- peaks that appear are due to attention, or else would average out
- 5 peaks: P1,P2,P3,N1,N2
- N1 effect
- 20-50: quick, subconscious component
- P3 (300ms): reflect higher processing, impaired in schizopjrenia
Visual
- cued visual attention test
- valid or invalid
- for valid, change in uV greater in occipital input
- P1 effect= positive deflection at 70-100ms; enhanced for attended visual, spatial input
ERPs on peripheral spatial cuing task
scalp electrode on contralateral visual cortex
- short delay=P1 enhanced for valid trials
- long delay= P1 reduced/inverts for valid trials, actually greater in invalid trials
Attention on cells
- enhance/suppress reponse (height of tuning curve)
- sharpen tuning of cortical nerves to specific stimuli (width of tuning curve)
- tuning shifts to favor different stimulus (shift of tuning curve)
orientation selective depends on attention, great attention means greater response
increase in neural activity in contralateral visual cortex when attention
Attention and receptive fields
Can see affects of shift in attention on a single (V1/V4?) cell
- monkey stares at fixation point, can see in addition an ineffective and an effective stimulus for the V4 neuron within the V4 neuron’s receptive field for a period of time,
- when attention shifts to ineffective stimulus neuron’s response suppressed
evidence for attention neurons
- monitored signle neuron in posterior parietal cortex
- increased firing when attended target
- more juice -> more attention and more firing
attention can tune the receptive field of extrastriate visual neurons
- can shift peak sensitivity within a receptive field (change where sensitive)
- can cause size of receptive field to shrink (decrease width to sharpen)
Superior colliculus
- in dorsal midbrain
- guides attentional eye movements
Pulvinar
- in posterior thalamus
- involved in visual processing, orienting/shifting attention, and attentional filtering of stimuli
