Perception and Attention

Question 1

Covert attention

Answer 1

• Sighted people can pay attention to a part of space that they aren’t directly looking at

Question 2

The Typical Results of The Posner Cueing Paradigm - Endogenous Attention

Answer 2

Choosing to pay attention to a particular part of space makes you react faster to things that happen in that part of space

Question 3

The Typical Results of The Posner Cueing Paradigm - Exogenous Attention

Answer 3

If your attention is drawn to that part of space without you intending to, but only if the something happens in that part of space very quickly

Question 4

Posner’s Attentional Systems - Endogenous

Answer 4

• Controlled by individual intentions and expectations
• Involved when central cues are presented
• Top-down

Question 5

Posner’s Attentional Systems - Exogenous

Answer 5

• Automatically shifts attention
• Involved when uninformative peripheral cues are presented
• Stimuli that are salient / differ from other stimuli are most likely to be attended
• Bottom up

Question 6

Attention as a spotlight - Posner (1980)

Answer 6

Endogenous attention is a limited resource that we distribute

Question 7

Hemispatial Neglect - How much id neglected? (Di Russo et al, 2008)

Answer 7

• ERPs elicited by visual stimuli in the left visual field (i.e. the neglected side)
• Early processing relatively preserved up to 130ms post stimulus
• ERPs generated within visual cortices
• Followed by large differences in later ERP components generated in dorsal parietal lobe

Basic perceptual processing happens to things in the neglected field

Question 8

Hemispatial Neglect - How much is processed? (McGlinchey-Berroth et al, 1993)

Answer 8

Patients with neglect can’t accurately identify objects presented to neglected field
- No conscious access of what they saw

An object presented to the neglected field can change patient’s behaviour
- will be faster to respond to semantically related word to stimuli so meaning must be processed?

Question 9

Lesions underlying neglect - Fierro et al, 2000 + Hilgetag et al, 2000

Answer 9

• Right inferior parietal lobe (temporoparietal junction + angular gyrus)
• TMS on the same regions produces neglect and extinction-like symptoms in control pps

Question 10

How to explain neglect/extinction - Corbetta + Shulman, 2002

Answer 10

• Both deficits of attention not perception
• Argue that neglect is mainly due to impairment of the stimulus-driven system

Question 11

What is impaired in Neglect - Smania et al, 1998

Answer 11

Neglect patients benefit from valid endogenous cues in both visual fields

• Suggests that endogenous orienting system is relatively intact

Question 12

What is impaired in Neglect - Bartolomeo et al. (2001)

Answer 12

• Experiment in which cue on the right (intact) field predicted stimulus on the left
• Patients benefit as much as healthy controls from valid cue
• Suggests that endogenous orienting system is relatively intact

Question 13

Disengagement of Attention - Losier and Klein (2001)

Answer 13

• Neglect patients most impaired when trying to disengage attention from intact side
• Attended hemisphere exerts a “hold” signal
• The invalid target should engage the exogenous system, but it doesn’t - it is impaired

Question 14

Neglect/Extinction - Summary

Answer 14

• Prevalence following right brain damage
• Particularly related to disengagement of the attentional spotlight from the ipsilesional side of space
• Evidence suggests problems with exogenous attention disproportionately more than with endogenous attention