Higher Cognition Flashcards
selective attention
how efficiently can we select relevant information and ignore irrelevant information
attention good for
influencing perception and awareness
limited attentional capacity
shadowing task + cocktail effect
endogenous
top down attention – actively choose to attend to something
exogenous
bottom-up attention – attention is stimuli driven
Posner experiments
influence of covert attention on processing efficiency
spatial spotlight
conjuction of features need to be analysed by a moving spotlight
- Different attributes of a single object – perceptual synthesis
- Scan array for presence of a single feature – RT varies little with number of elements present in the array- feature pops out – parallel search
- If conjunction of feature has to be analysed – RT increases linearly with the number of items in the array – serial search implicating a spatial spotlight which analyses objects one-by-one
neglect
-Brain damage affecting the inferior parietal cortex within the right posterior parietal lobes
benefits of attention
detection benefits ( Posner cueing paradigm )
spatial spotlight - parallel vs serial search
neglect not a sensori deficit
- Olfactory processing
- orienting attention
- Representational neglect.
Representation Neglect
Bisiach and Luzzatti asked patients to imagine all the landmarks of the Piazza del Duomo in Milan from a particular vantage point (north or south). In patients with neglect, errors were related to their neglected side as determined from their vantage point. This suggests that neglect patients may have difficulties in scanning memory representations, as well as the actual hemi- space, contralateral to the side of the lesion (Bisiach and Luzzatti, 1978).
orienting attention - neglect patient failure
- Patients with damage in visual areas of the brain may exhibit blind spots (scotoma) when their fields of spatial vision are tested while they are fixating. Such deficits can be hard to pick up if the subject is allowed to move their eyes. But this is not true of neglect; in this case the patient will not use eye movements to explore contralateral space, even though their eye movements per se are intact.
Olfactory - neglect
Olfactory neglect occurs even though the olfactory pathways, unlike auditory, tactile, or visual pathways, are uncrossed
extinction
extinction which occurs when the subject is simultaneously presented with stimuli in both fields, but only the ipsilateral stimulus is detected.
due to attentional competition between stimuli in different regions of space.
Posner Paradigm neglect patients + extinction patient
when the cue is invalid, slowe RT when the cue on the right hemi- space.
have difficulty disengaging attention from the invalid cue.
In the case of extinction, then, the suggestion is that neglect patients cannot release attention from the right hemi-space to enable them to detect the stimulus on the left.
Posner to study attentional deficits
distinction between different attentional orienting
deficits can be related to three components of exogenous orienting: ‘disengage’, ‘move’, and ‘re-engage’ attention.
unilateral thalamic damage can be slow to detect targets opposite to the side of the lesion regardless of the side on which the pre-cue occurs (problem with re- engagement)
parietal lobe
attention modulation
right parietal
orienting attention
evidence for orienting attention right parietal
In one such study (Corbetta et al., 1993), subjects were instructed to keep attention at a central location or move it in one visual field between a number of boxes to detect targets, without moving the eyes. Subtraction between the two conditions revealed residual activation in the right parietal lobe when targets were on the left and in both right and left parietal lobes when the targets were on the right
changes in regional cerebral blood flow while participants searched visual displays for targets defined by either motion or colour, or both.
- attention orienting
‘colour’ condition all four windows displayed moving dots but only one window had the target coloured dots which subjects had to report.
‘motion’ condition some of the dots in only one window moved at target speed.
In the ‘conjunction’ condition subjects had to report targets only when the correct coloured dots moved at the target speed.
Passive conditions served as control (subtraction) tasks.
The theoretically expected RT functions were flat in the separate conditions and graded for the conjunction condition.
The anatomical focus for the conjunction condition was posterior parietal cortex, just as in the spatial shifting experiment mentioned above.
This suggests that subjects are indeed shifting spatially between different locations to find the conjunction targets.
cellular studies of visual attention
Cellular studies of visual attention have suggested that selective attention involves either enhanced firing of cells that respond to the object of interest or attenuated firing of cells that respond to objects that are being ignored.
monkey experiment covert and overt attention
that cells in the superior colliculus and in V1 responded more intensely when the animal made a saccade to the stimulus, but not when they didn’t.
- do not code selective attention per se but only code overt attention, enhancement was due to changes in the general level of arousal and from the neural mechanisms involved in the eye movement.
In contrast, cells in the posterior parietal cortex, the pulvinar and the dorsolateral PFC showed enhanced responding to the stimulus regardless of whether they made the saccade or not (i.e. in both the overt and covert condition), thus these cells have the properties of visual attention units.
spatial attention altering activty in v4
(a) When the animal attended to the red bar, the V4 neuron gave a good response. (b) When the animal attended to the green bar, a poor response was generated.
brain areas in selective attention
posterior parietal cortex.
In addition, damage to several other brain structures has been reported to cause neglect, including the thalamus (the pulvinar), and the dorsolateral prefrontal
cortex, and more importantly the white matter tracts linking these structures. Thus the general view is that attention does not result from the activity of single brain areas but rather from the interaction of large-scale networks that include prefrontal regions (cingulate and dorsolateral prefrontal), parietal cortex, visual association cortices, the thalamus (pulvinar) and frontal eye fields.
