PSYC 301 MT2 - Attention

visuospatial attention

selectively focus on a location in space while ignoring others

*different from attention in attention-deficit/hyperactivity disorder → executive function (planning, monitoring performance, concentrating)

classic test of visuospatial attention: posner cueing task

measures reaction time differences

two trial types:

1. congruent: cue predicts target location

2. incongruent: cue misleads

posner cueing task - results

early after cue presented → faster responses (facilitation)

later after cue presented → slower responses (inhibition of return, attention suppresses going back to the same spot)

posner cueing task - purpose

allows researchers to study visuospatial attention independent of gaze

posner cueing task - elements

can change elements of task depending on research question

- amount of time cue is up

- location of cue

- appearance of cues

contralateral neglect/hemispatial or unilateral neglect

failure to notice or respond to objects on the side opposite the brain lesion

spatial bias: eyes and movements are drawn toward the same side as the lesion (ipsilesional side)

neglect - causes

not caused by basic vision or motor problems—rather, attention to the opposite side (contralesional space) is reduced

causes: most often stroke, but also trauma or alzheimer's disease

neglect - features

typical pattern: right hemisphere damage → left-side neglect

affects 25-30% of stroke patients, 3-5 million a year worldwide

even body parts on neglected (contralesional) side can be ignored

neglect - tests

1. clock drawing

2. line cancellation: given a piece of paper with black lines and asked to cross out all lines

3. drawing: may only draw on right side

4. eye movements: eyes movements mostly on right side

5. imagination: neglects left side of space, only described all landmarks on the right

6. visual judgement: fail to notice abnormalities occurring on the neglected (usually left) side. when asked which image they prefer, they often choose the "normal" one and more likely to notice dramatic oddities, even though they can't identify what's wrong with the other

7. line bisection: asked to mark middle of the line; if neglect is severe might mark very far right

neglect - brain structures

all in right hemisphere, 3 major cortical areas

1. inferior parietal lobe and temporo-parietal junction

2. superior temporal gyrus

3. ventral frontal cortex

*damage to white-matter tracts connecting the 3 areas can also lead to neglect

neglect - brain structures - function

spatial orienting, transforms signals from eyes and body into spatial representations

why is neglect so lateralized?

right parietal cortex monitors both sides of space while left parietal cortex monitors only right

pseudoneglect

asymmetry in brain lateralization can be seen in healthy adults too

tested via line bisection → non-brain damaged individuals show slight bias to the left (pseudoneglect) because the right hemisphere is so dominant in processing space (i.e. perceiving left side to be bigger than it is)

when do subcortical injuries lead to neglect?

DWI (diffusion-weighted imaging) show cortical injury

PWI (perfusion-weighted imaging) show areas of delayed blood flow

subcortical injuries lead to neglect only if there’s right-hemisphere cortical hypoperfusion (reduced blood flow to cortex), not subcortical damage alone

neglect - types

1. egocentric: neglects the left side of space relative to their own body

2. object-centred: neglects the left side of individual objects, no matter where the object is in space

neglect - recovery signs

1. allesthesia: mislocating stimuli from neglected side to non-neglected side

2. simultaneous extinction: detects stimulus on neglected side alone, but not when stimulated ipsilaterally (both sides together) because easily detected stimulus “cancels out” detection of other stimulus

neglect - spectrum of recovery

recovery ranges from temporary mild neglect → permanent denial of contralateral space

neglect - treatment

1. prismatic adaptation: shifting visual field can temporarily correct bias

2. VR reaching training: improves visual scanning and cancellation tasks

3. rTMS (inhibitory, low-freq) over left PPC: can lessen neglect for 15 days

balint’s syndrome

severe disruption of attention and explicit spatial awareness based on large region of brain damage

characterized by:

1. oculomotor apraxia

2. optic ataxia

3. simultanagnosia

e.g. cannot locate items they see and can’t tell when item is moved toward or away from them

oculomotor apraxia

can’t shift gaze (“sticky fixation” or “psychic paralysis of gaze”)

due to damage to saccade-planning areas in parietal cortex

optic ataxia

misreaching under visual guidance (especially with contralesional hand)

damage to superior parietal lobe

simultanagnosia

can only perceive one object at a time (can't see simultaneous objects/events)

balint's syndrome - functions that are impaired

sensory + language intact, but spatial attention severely impaired

balint's syndrome - causes

bilateral parieto-occipital damage (stroke, dementia, trauma)

balint's syndrome - recovery

only small case studies, no standard treatment program

coping strategies can help (e.g. practice dialing a phone) but neurological change is almost impossible because of the distribution of brain damage

peripersonal space (PPS) and other traits

attention system prioritizes space near the body

inside PPS → bisection performance left bias; outside → bisection performance right bias

large PPS: correlated to anxiety and claustrophobia

small PPS: correlated to autism and schizophrenia