Dysfunction Affecting Perception & Attention

Question 1

Consciousness

Answer 1

• subjective experiences and feelings

- essential function is visual awareness

Question 2

Body ownership

Answer 2

the perception of one’s own body

Question 3

Body schema

Answer 3

• representation of the position of the body and its parts within a space
• includes length of limbs, their arrangement in pace, shape of the body surface, etc.

Question 4

parietal lobe

Answer 4

• important for spatial processing, spatial orientation, and sptatial attention
• • right hemispheric dominance in spatial attention
• lateral area is connected with frontal eye field and other areas of visual cortex
• • involved in saccades

Question 5

previously proposed mechanisms of contralateral neglect syndrome

Answer 5

• disrupted attention processing: patients unable to direct attention away from right side; disruption in balancing attention between left and right -> hyperattention to right side
• altered neural representations of space in the horizontal dimension (parietal and occipital cortexes)

Question 6

Jerath & Crawford’s proposed mechanisms of neglect in contralateral neglect syndrome

Answer 6

• if right parietal lobe (spatial orientation) is damaged, it’s not able to spatially map left side of visual field or body (damaged spatial map is then integrated into 3D default space by thalamus)
• if thalamus is damaged, it’s not able to integrrate and reimage the processed info from parietal lobe within 3D default space
• both will result in neglect
• similar mechanisms for motion sickness and claustrophobia

Question 7

Jerath & Crawford’s views on conciousness

Answer 7

• thalamus is central to consciousness
• thalamus uses corticothalamic feedback loops to integrate multisensory info from cortex to create a reimagining of 3D space that becomes conscious (“3D Default”; what we “see” in our mind)
• • allows us to attend to our bodies (ineffective in people with agnosia)

Question 8

Posterior cortical atrophy (PCA)

Answer 8

• characterized by progressive deterioration of visuospatial and visuoperceptual abilities, as well as numeracy and literacy skills
• commonly related to Alzheimers (same tau/plaques in visual association cortex)
• initially have normal memory, but have visual blurriness/glare, reading difficulties
• may be due to simultanagnosia, optic apraxia, optic ataxia
• MR scans usually show bilateral occipital and parietal lobe atrophy

Question 9

simultanagnosia

Answer 9

• inability to synthesize overall meaning of a visual scene despite being able to recognize its individual elements (ie. seeing the trees but not the forest) -> can perceive only 1 object at a time (“Local capture”)
• Due to lesions affecting parieto-occipital junctions (esp. Brodmann’s area)

Question 10

optic apraxia

Answer 10

• inability to initiate saccades

Question 11

optic ataxia

Answer 11

• impairment of goal-directed, visually guided reaching and grasping of targets in the periphery
• Due to lesions affecting intraparietal sulcus

Question 12

treatment for PCA

Answer 12

• No specific treatment
• • Anticholinesterase meds may help
• • Learning coping & compensatory strategies
• • Support centres

Question 13

cTBS and visuo-spatial neglect

Answer 13

• Continuous theta burst stimulation (cTBS) (non-invasive procedure) applied over left posterior parietal cortex induced clinical improvement of visuo-spatial neglect in a patient with TBI
• • Decreased excitability of left hemisphere, increase of connectivity in frontal-parietal network
• Improvement persisted for at least 2 weeks