Disorders of Attention and What is Attention Selecting?

Spatial Shifts of Attention and Posner's Cuing Task

Spatial shifts of attention are examined using Posner's Cuing Task.
This task helps to understand how attention can be directed to specific locations in space.

Damage to the right parietal lobe, typically from a stroke, can lead to unilateral neglect.
Patients with unilateral neglect do not pay attention to the contralateral side of space, usually the left side following a right hemisphere lesion.
Patients may recover over weeks or months but can be left with lasting extinction.
Extinction: Patients will respond to a single event on the contralateral side but fail to notice a contralateral stimulus when an ipsilateral stimulus is simultaneously presented.

Line cancellation task: Patients are asked to cross out lines on a page, and those with neglect may only cross out lines on one side.
Copying task: Patients are asked to copy a drawing, and they may only draw one side of the object.

Patients neglect the side of space contralateral to the lesion even for mental images.
This suggests that neglect is an attentional rather than a perceptual deficit.

Patients neglect the side of objects contralateral to the lesion (left side of objects for right hemisphere lesion).

Higher accuracy when reporting two features from the same object, even if both objects are in the same spatial location.

Participants are faster to respond to an (invalid) target when it appears on the same object compared to a different object, even if they are the same distance from the validly cued location.

Change blindness: The phenomenon where changes in the visual field are not noticed if not attended to.
Attention is required for awareness.
You notice changes that you attend to.

When encoding the visual world into memory, you only encode things you attend to and that are relevant.
Subtle changes may go unnoticed if attention is not directed to them.

The entire visual field enters the retina, but only the parts of the world that are being attended to receive deeper processing.

Attention appears required for awareness, and we can attend to features like color.

Participants attend to a side of the screen and one of two colors, pressing a button when a luminance change occurs.
"Probe" stimuli appear on the opposite side, matching either the attended or unattended color.
ERP (event-related potential) responses are elicited more strongly by task-irrelevant probes presented in the attended color.

Participants attend to an RSVP (rapid serial visual presentation) stream for a letter in an attended color (e.g., red) and report it.
Distractor stimuli appear right before the target letter at varying distances from the center.
Color-matching distractors "capture" attention, and this effect scales with distance.

Participants fixate on a central point.
A cue appears, indicating where the target might appear (valid, invalid, or neutral).
A target appears, and participants respond as quickly as possible.

Peripheral, exogenous cues: Appear away from fixation, "external" cue. Can be unpredictive (e.g., 75% valid, 25% invalid).
Central, endogenous cues: Appear at fixation, "internal" cue. Can also be unpredictive (e.g., 50% valid, 50% invalid).

Intraparietal sulcus (IPS) and the temporoparietal junction (TPJ) are key brain regions involved.
IPS is related to attention.
TPJ is related to perception.

Attention = the focusing of the brain's "processing power" on particular regions of the visual input.

Attention is the focusing of the brain’s "processing power" at subsets of the sensory input.
It can be directed to spatial locations, objects, and/or features.
Attention involves brain regions like the IPS/LIP.
Brain damage to these areas can cause unilateral neglect and eventually extinction.
Unattended sensory input does not reach the level of awareness.