1
Q
attention
A
= prioritised processing of some inputs from larger set of selectable items
- people cannot perceive everything
- ability to make selections allows for flexibility and control
2
Q
attention mechanisms
A
= determine which items are selected
3
Q
attention phenomena
A
demonstrate limitations, constraints, failures of attentional mechanism
4
Q
attention phenomena
- inattention blindness
A
= perceptual blindness = people can miss obvious changes in their situation simply because they paid attention to something else
- criteria for inattentional blindness:
1. failure to notice a visual object or event
2. object or event was fully visible (in field of view)
3. object or event was easily identified under circumstances in which it is consciously perceived
5
Q
attention phenomena
- change blindness
A
= occurs when a change in visual stimulus is not noticed by the observer. - 2 types:
- presented with (1) image, (2) brief blank screen, (3) image almost the same as the first except for a small difference
- presented with an image that slowly changes
6
Q
attention phenomena
- attentional blink
A
= occurs when second of two targets is not detected when it appears close in time after the first
- once the first letter grabs attention, attentional system does not work for a small period (like a blink)
7
Q
attentional blink
- experimental paradigm
A
- presenting a series of letters rapidly one after the other (rapid serial visual presentation)
- asking participants to report letters that appear in red
- T2 reportability depends on inter-target interval (= stimulus onset asynchrony; SOA) between both targets
- only 100ms between the two letters: report both letters correctly
- 200-400ms between two letters: do not report the second letter
- -> first letter grabs attention, attentional system does not work for a small period
8
Q
attention phenomena
- cocktail party effect
A
= ability to voluntarily focus on what we choose to perceive and process
- filter out competing, distracting, surrounding conversations
9
Q
attention phenomena
- lunch-line effect
A
= pronunciation of your name in another conversation manages to pull your attention away from whatever you were currently paying attention to
- perceptual systems track auditory inputs in environment for some salient input
10
Q
forms of attention
- endogenous attention
A
= top-down attention = voluntary focus of attention
- actively select the inputs to prioritise and process
- higher brain regions (frontal and parietal cortex) are involved
- makes reaction times shorter
- cock-tail party effect
- can be overt or covert
11
Q
forms of attention
- exogenous attention
A
= bottom-up attention = involuntary focus of attention
- attention shifts not by choice but by salience of stimuli in our environment
- can be overt or covert
12
Q
Posner task
A
- participants fixating on a central cross
- close to fixation point a symbolic cue appears (arrow pointing left or right), telling participant which side a visual target is about to appear.
2a. valid cue = target appears in location cue was pointing towards
2b. invalid cue = target appears on other side, which was not pointed to
- cue is most often valid, allocate attention to the cued visual location –> 25% of the time, cue is invalid
- valid cueing = benefits
- invalid cueing = costs
13
Q
endogenous Posner task
A
- since a visual cue is an automatic exogenous attention grabber (provided it is salient), the centrally presented symbolic cue will also draw attention to the central location
- -> causes timing difference between both task
- endogenous cueing: target follows cue much later (500ms) –> gives subjects time to recover from the central exogenous cue and then voluntarily allocate attention to the location
- more valid cue trials (75%) than invalid cue trials (25%)
- -> if endogenous cueing tasks were to have valid cues only 50% of the time, would render the cue meaningless (non-informative)
14
Q
exogenous Posner task
A
- cue automatically draws attention to whichever visual field location the cue is presented in
- -> valid cue is a salient stimulus presented at location where the visual target appears
- -> invalid cue is a stimulus presented at the location different from the one where a visual target appears
- exogenous cueing: target follows cue after only 100ms
- valid cue trials (50%) are presented as much as invalid cue trials (50%)
15
Q
forms of attention
- divided attention
A
= ability to focus on multiple things at the same time (multi-tasking)
- as soon as you perform two tasks at the same time, you perform both less adequately than you would if you performed them one by one
- difficulty in dividing attention depends on:
1. how constantly your attention is required for both tasks
2. relation + similarities between tasks: easier to divide attention between a visual and auditory task but more difficult to divide attention between two auditory tasks
16
Q
forms of attention
- overt attention
A
= allocation of attention accompanied by a shift in eye movement
17
Q
forms of attention
- covert attention
A
= allocation of attention without making eye movements
18
Q
forms of attention
- spatial (space-based) attention
A
= selectively process visual information through prioritisation of an area within the visual field (attention to spatial location)
- feature-based attention = ability to pay attention to particular features of stimulus
- -> visual features: (1) colour, (2) orientation, (3) intensity (brightness) of visual inputs
19
Q
spatial attention
- visual search task
A
- asked to quickly locate a visual target in an array of distractors
- certain features of a stimulus can “pop out”
20
Q
forms of attention
- object attention
A
= attention to one object rather than another
- two images might be superimposed (house and face) and subjects will be asked to selectively focus attention on either the house or the face
21
Q
object attention
- object attention experiment
A
- 4 possible cue + target locations are positioned in a square formation
- difference in reaction times between D and E (D has shorter reaction times), even though visual target is equally far from cue in both conditions
- when varying horizontal and vertical rectangles, participants have significantly shorter reaction times if cue and target are part of same object
- -> object attention + it independently of spatial attention affects reaction time
22
Q
forms of attention
- temporal attention
A
= directing attention to a specific instant in time
23
Q
forms of attention
- selective attention
A
= ability to prioritise and attend to some things while ignoring others
- optimal strategy: attend to stimuli that are relevant to current behaviour and goals (top-down control)
- if you are interrupted by a loud sound, you will reflexively shift your attention (bottom-up control)
- not a global brain state
24
Q
theories of attention
1. filter model
A
= attended messages are filtered out
- attended and unattended messages enter sensory store
- selective filter selects inputs based on physical properties; at the same time unattended messages are completely blocked
- -> forming bottleneck effect: only some inputs pass through - inputs that make it through bottleneck go through higher level processing in order to reach working memory
- selective filter occurs early on in the process (2)
- disadvantages: (1) cannot account for lunch-line effect (only attended auditory streams pass the selective filter); (2) it is thought that filters operate at a later processing stage (after level of semantic processing)
25
1. filter model
| - dichotic listening task
- present different spoken stories to left and right ear
- found that participants could only attend to one of auditory streams (second stream was filtered out and not reportable)
26
theories of attention
| 2. spotlight theory
= attention operates as a spotlight
- useful for understanding spatial attention and visual search tasks
- can control size of spotlight
- disadvantages: difficult depending on image, especially in conditions of crowding
27
theories of attention
| 3. feature-integration theory
= when perceiving a stimulus, features are registered early while objects are identified separately
- early selection filter (attenuation version)
1. pre-attentive stage: certain features are analysed (automatic and parallel processing)
2. focused attention stage: processed features are combined into objects (attention required for binding of features)
- iIllusory conjunction: connecting factor is the spatial location of objects in the scene which determines which features go together
- -> what goes wrong here is that participants combine features of two objects into one object
28
theories of attention
| 4. resource theory
= focuses on the allocation of attention in multiple tasks
- likely intermediate form between these 2 is the answer:
1) single resource theory: one common pool of attention to be distributed amongst multiple tasks (limited --> explains degradation of performance while multi-tasking)
2) multiple resource theory: several resources of attention (explains how some tasks combine better than others depending on parameters like sensory modality)
29
neurophysiology of attention
- (1) subcortical and (2) cortical networks interact to enable us to selectively process information
1. sub-cortical structures: (1) superior colliculus (midbrain), (2) pulvinar (thalamus).
- damage: deficits in ability to orient (1) overt and (2) covert attention
2. cortical structures: (1) portions of frontal cortex, (2) posterior parietal cortex, (3) posterior superior temporal cortex, (4) medial brain structures like anterior cingulate cortex (ACC), posterior cingulate cortex (PCC), and insula
30
attentional control
- goal-directed (top-down) and stimulus-directed (bottom-up)
- spatial attention controlled by a mixture of stimulus-driven and goal-directed mechanism
- attention controlled by 3 interacting networks
1. goal-directed DAS (control of spatial attention and saliency of objects)
2. stimulus-driven VAS (disengaging + re-orienting attention, detecting unexpected/changing stimuli)
3. sub-cortical network (arousal, eye movements, filtering input, shifting and orienting of attention).
31
attentional control
| - goal-directed
= top-down
- neurones from executive attentional control systems alter excitability of neurones in sensory-specific cortical areas
- -> stimulus given high priority: response to stimulus in sensory areas is enhanced
- -> stimulus given low priority: response to stimulus in sensory areas is attenuated
32
attentional control
| - stimulus-directed
= bottom-up
- circuits from sensory system interact with circuits that orient and engage attention, since the stimulus itself captures attention
- excitability of visual cortex is mediated through selective attention network involving the posterior parietal cortex (PPC), dorsolateral and superior prefrontal cortex, and pulvinar nucleus (thalamus)
33
attentional control
| 1. dorsal attention system
= goal-directed attention
- concerned with spatial attention
- modulates sensory processing: attentional priming of sensory cortex to particular location, provides preferential processing to some target inputs; spatially specific
(1) frontal eye fields (FEF), (2) supplementary eye fields (SEF), (3) intraparietal sulcus (IPS), (4) superior parietal lobule (SPL), (5) precuneus (PC)
- FEF: exerts control over attention (coordinate eye movement and gaze shifts); participate in goal-directed attention control over V4 activity; spatially specific; task specific signals
- dorsal frontoparietal attention network: active when participants attended and responded to stimulus
- posterior partieral cortex: dorsal areas along IPS, SPL
- -> lateral intraparietal (LIP) area: subregion within IPS; concerned with location and saliency of objects
34
attentional control
| 2. ventral attention system
= stimulus-driven attentional control
- concerned with non-spatial aspects of attention (no topographic maps found)
- strongly lateralised to right hemisphere
(1) temporoparietal junction (TPJ) in posterior parietal cortex, (2) inferior and middle frontal gyri in ventral frontal cortex, (3) ventral areas of intraparietal sulcus (IPS)
- TPJ: engaged strongly during target detection; acts like a circuit breaker (= interrupting current attentional focus established by dorsal network)
- -> right TPJ responds equally to novel stimuli in right and left visual field
- dorsal and ventral systems interact and cooperate to produce normal behaviour
35
attentional control
| 3. subcortical brain network
1. superior colliculi (SC): eye movements (attention, visual search)
- inputs from the retina + other sensory systems, basal ganglia, cerebral cortex
- outputs to thalamus and motor system.
- SC neurons have several characteristics:
1) do not participate in voluntary visual selective attention
2) play a role in overt attention
3) sensitive to saliency of stimulus, including (1) detecting salient item, (2) guiding eye movement towards salient item
2. pulvinar of thalamus: visually responsive neurones that exhibit selectivity for colour, motion, and orientation; certain areas also contain retinotopic maps; involved in both voluntary and reflexive attention
- input from superior colliculus + has connections to many parts of the brain
- neurones show enhanced activity when:
1. stimulus is target of saccadic eye movement
2. stimulus is attended without eye movements to the target
36
brain damage and attentional deficits
| - progressive supra nuclear palsy (PSP)
= difficulty in shifting attention --> slow to respond to cued targets
- degeneration of SC + basal ganglia which
37
brain damage and attentional deficits
| - pulvinar lesion
- difficulty orienting attention covertly to targets in contralateral visual field; difficulty filtering distracting information (covert spatial attention and filtering of stimuli)
- attentional orienting deficits, specifically a problem in engaging attention at cued location
- increased reaction times for validly and invalidly cued targets that appear in contralesional space
38
brain damage and attentional deficits
| - (unilateral spatial) neglect
= (1) reduced arousal and processing speeds and (2) attention bias in the direction of their lesion e.g. right hemisphere lesion results in right attentional bias and a neglect of the left side of the visual field (ipsilesional)
- -> deficits in attending to + acting in direction that is opposite the unilateral brain damage is present, despite normal vision
- affect imagination and memory
- symptoms do not result from blindness
- looking at the patterns of eye movements: method to observe this involves --> show pattern of eye movements that are biased in the direction of the right visual field while those without neglect search the entire visual field (move equally to left and right)
- attention network is only damaged in one hemisphere (due to stroke); not damage to specific brain area
- -> particularly, interaction between DAS + VAS is disrupted
- -> right hemisphere: more severe form of disorder
- -> shows that a network of cortical and subcortical areas (right hemisphere) result in spatial attention disturbances
39
neglect (neurophysiological tests)
| - line cancellation test
- patients given sheet of paper containing many horizontal lines; asked to bisect lines precisely in the middle by drawing vertical line
- lesions in right hemisphere:
a) neglect at level of object representation: bisect individual lines to the right of midline
b) neglect at level of visual scene: completely miss lines on the left side of the paper
40
neglect (neurophysiological tests)
| - copying objects or scenes
- patients have difficulty copying a simple line drawing such as a flower or clock (neglects left side)
41
neglect (neurophysiological tests)
| - imagination task
- patients neglected things on side contralateral to lesion in both conditions describing (1) view from the cathedral and (2) view toward the cathedral
- in both conditions: patients reported items from visual memory that they had previously neglected in other condition
- -> neglect cannot be attributed to lacking memories and rather indicates attentional neglect
42
neglect (neurophysiological tests)
| - visual field testing
- neglect patients detect stimuli normally when those stimuli are salient and presented in isolation
- simple flashes of light can be seen, even when placed in contralateral (neglected) visual field
- extinction: occurs when competing stimulus in the ipsilateral field prevents the patient from detecting the contralateral stimulus; when patient is presented with two stimuli simultaneously (one in each side of the visual field)
- biases against the contralesional sides of space and objects can be overcome if patient’s attention is directed to the neglected location
43
brain damage and attentional deficits
| - Balint's syndrome
= severe disturbance of visual attention and awareness; see one or a small subset of available objects while failing to (1) see them all together and (2) localising them in space with respect to each other
- 3 main deficits:
1. simultanagnosia: difficultly perceiving visual field as a whole scene
2. ocular apraxia: deficit in making eye movements (saccades) to scan visual field; inability to guide eye movements voluntarily
3. optic ataxia: problem in making visually guided hand movements
- bilateral damage to regions of posterior parietal and occipital cortex
- -> shows that posterior parietal and occipital damage leads to an inability to perceive multiple objects in space, which is necessary to create a scene
CONSCIOUSNESS
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