selective attention and awareness

Question 1

damage to V1 causes loss of visual awareness

Answer 1

cortical blindness: retinal inputs intact (lateralisation occurs after optic chasim)
- Lesion to V1 in humans: stroke in the posterior cerbral artery

Question 2

blindsight-

Answer 2

• visual orienting in the absence of awareness
  occurs following unilateral damage resticted to the PVC
  Patient may show persevation of :
  
  • Pupillary reflexes
  • Manual and saccadic localisation
  • Wavelength (colour) and motion discrimination
  • Orientation and shape discrimination

Question 3

using perimetry to identify where vision is based on blindsight

Answer 3

• Patient db= right occipital lesion optic disc= chance elsewhere in blind region= above chanve.

Question 4

how does visual information support unconscious perception in blindsight

Answer 4

• Evolutionary older pathways: superior colliculus, pulniver nucleus
  
  • The only visual pathway for some animals, supports basic visuallyu guided response

Question 5

how much of the real world are we aware of

Answer 5

• Evidence of blindness shows we can process visual info without consciouss awareness.
  
  • It also provides a good reason to ask how much of the activity in visual cortex is associagted with coscious experience.
  • Perceptual demonstrations show that attention limits our awareness.

Question 6

why are we aware of only a small part of the visual world- why is awareness limited

Answer 6

• Neural limitations: bottleneck of the optic nerve
  
  • Metabolic limitations: neural activity consumes a lot of energy and requires a lot of blood oxygenation
  • Computational efficiency: assign the most neural machinery to processing important objects
    Computational complexity: awareness integrates experience

Question 7

the concept of attention

Answer 7

• William James: idea that there is withdrawal from one thing in order to deal effectively eith others, the cost of dealing with something is that we have less processing of the other things which are happening.

Question 8

single brain process that corresponds to attention

Answer 8

• selectivity (spatial, temporal, motoric), capacity limitation, vigilance, perceptual set (sustained attention), switching

Question 9

covert selective attention

Answer 9

• reveals prioritizing by the brain
  Hermann studied effects of covert allocation of attention on visual perception; one can concentrate on the sensation from a particular part of out peripheral nervous system and at the same time exclude attention from all other parts.
• car accident

Question 10

spatial attention alters neural processing speed

Answer 10

task, theres an arrow that points to the right and the left
- We are much faster when we have a target then a que pointing away from the target.
- Slower response for invalid trials
- Enhanced processing in attended locations and less processing in places we are not attending to.,

Question 11

neurons in parietal cortex are modulated by attention

Answer 11

• Change in repsonse to neuron if we flash the stimuls. If stimulus appears in visual field,
  
  • To get the task right, they need to focus their attention on a specific point
  • Used monkeys, much bigger response from the neuron,

Question 12

attention increases spatial selectivity in V2 and V4 neurons

Answer 12

• Monkeys were trained to attend to one of two locations In the receptive field 1, 2 or 4
  
  • Effective and ineffective stimuli were shown at both locations
  • Stimuli were shown sequentially (one object in the RF) or simultanedously (two objects in the cells RF\
  • Looked for evidence of spatial selectivity in the simultaneous condition.
  • Attention to stimulus increases cells response
    the difference is greatest when there are 2 stimuli in the receptive field, and they have one to focus on. Attention boosts response to asingle object.

Question 13

attention enhances responses relative to competing objects inRF

Answer 13

• attention to a stimulus increases a cell’s response regardless of condition
• effect of attention is greatest for two stimuli in RF
• attention helps bias response to attended stimulus in RF

Question 14

attention modulates early and mid-level visual processing in humans

Answer 14

• Watanabe
  
  • fMRI 1.5 t
  • Randomly arranged moving dots
  • Translation component: v1 and MSt sensitive
  • Expansion component: MST sensitive
  • V1 not sensitive.

Question 15

Effects of attention on early and mid level visual processing

Answer 15

• Passively viewing moving dots with expansion and translation does not alter the fMRI signal
  
  • Attending to the expanding component increrases the fmri signal in MT/ MSt
  • Attending to the translation component increases the fmri signal in both v1 and MT/MST where neurons are responsive to translation

Question 16

Brain regions that have shown neural correlations of visual attention:

Answer 16

subcortical regions:
- The superior colliculus
- the pulvinar nucleus
visually responsive cortical regions:
- Intraparietal sulcus (IPS)
- prefrontal cortex

Question 17

unilateral spatial neglect: a failure of spatial awareness

Answer 17

• occurs after damage to one side of the brain (usually the right)
• patients behave as if the affected side of space 9the contralesional side) has ceased to exist
• ignore food one one side of plate

Question 18

representational neglect

Answer 18

• Neglect in the absence of visual input
  
  • Often in conjuring with regular neglect
  • Implicates parietal areas in processes that support mental imagery.

Question 19

neuropathology of neglect

Answer 19

• Lesions in the frontal iris have resulted in neglect, temporal lobe through frontal areaS a legion here may disrupt information input aswell.

Question 20

unconscious perception of spatial neglect

Answer 20

Cant tell why they would prefer to live in the second house, but know there is something wrong with the first houses.

Question 21

two types of blindness from attention

Answer 21

change
inattention-= observer fails to see unexpected stim in plain site