Disorders of attention

Question 1

Why is studying brain damaged individuals valuable

Answer 1

We can learn much about attentional processes by studying brain damaged individuals as it gives us insight into how different brain regions contribute to attention and what happens when these systems are disrupted

Question 2

What are the three disorders of visual attention

Answer 2

Neglect

Extinction

Balint syndrome

Question 3

Neglect

Answer 3

Unilateral neglect typically follows brain damage to the right hemisphere

The brain is not processing anything to the left hand side

Question 4

Why is neglect different to being blind?

Answer 4

The eyes are functioning normally and patients can still see but there’s an attentional deficit - patients fail to acknowledge objects/people/own body parts on the left side of space

Question 5

Example of how neglect can manifest in spatial navigation

Answer 5

Brain (1941) - patients systematically ignored the left side and always made a right hand turn

Right Parieto-occipital damage

Question 6

Symptoms of neglect from case studies

Answer 6

Patients would only acknowledge that the right side exists in space and for themselves:
- wouldn’t shave the left side of their face
- miss food on left side of plate

Question 7

What is neglect most commonly caused by

Answer 7

Stroke

Blood supply to part of the brain is cut off - the blockage of blood supply occurs in the middle cerebral artery, this is going to supply blood to critical brain regions involved in attention

This blockage of blood supply in the middle cerebral artery area leads to attentional deficits

Question 8

Why are deficits in attention often to the left side of space

Answer 8

The right hemisphere is dominant for spatial attention and it processes both left and right visual fields

Question 9

What brain areas play important roles in neglect

Answer 9

Posterior parietal cortex - important role - damages here are strongly linked to deficits in spatial awareness and attention

Brodman’s areas 39 and 40 heavily implicated in neglect - this pathway processes spatial location and movement - any damage to these areas explains why neglect patients often bump into objects or fail to respond to stimuli on the left hand side

Question 10

Why does left parietal damage rarely produce right sided neglect

Answer 10

Because the right hemisphere plays a more of a dominant role in spatial attention and space related behaviours

Question 11

What can other cases of neglect be caused by, that isn’t damage to the cortex

Answer 11

Sub-cortical damage:

• Thalamus - most likely to see neglect
• Basal ganglia
• White matter

Question 12

What cortex appears to play a dominant role in spatial cognition in humans

Answer 12

The right parietal cortex

Most commonly the right inferior parietal lobe

This region is important for its role in how we process space and how we direct our attention to that space

Question 13

Which hemisphere are the main areas damaged in?

Answer 13

Right hemisphere

Question 14

Vallar & Perani, 1986
- study aim

Answer 14

Wanted to understand where the actual damage of neglect occurs in the brain.

Question 15

Vallar & Perani, 1986
Study method

Answer 15

They had 8 patients with neglect and they got everyone’s brain together and looked at where the damage occurred in each of these patients

They then superimposed everyone’s brain onto each other

Question 16

Vallar & Perani, 1986
Findings

Answer 16

Inferior posterior parietal region is a key hotspot for neglect for most patients - overlap in this region - typically this region that is damaged

Question 17

Functions of the Posterior Parietal Cortex (PPC)

Answer 17

Visuo-mortor control of behaviour (how we use vision to guide our actions)

Lesions to the PPC lead to neglect (ignoring the left side of space)

Also leads to optic ataxia (mis-reaching for things) and constructional apraxia (difficulty putting things together)

Question 18

Types of neglect

Answer 18

Spatial neglect

Egocentric (subject-centred) neglect

Allocentric (object-centred) neglect

Question 19

Spatial neglect study

Answer 19

Karnath, 1994

Patients failed to scan the left side of a scene (failed to even look at the left side)

Question 20

Egocentric neglect study

Answer 20

All about patients own spatial perspective

They were given a piece of paper with a line and ask to dissect it in the middle. The patient’s middle is far to right - as they didn’t acknowledge the left half of the line

Question 21

Allocentric neglect

Answer 21

This involves a lack of awareness of the left side of objects rather than simply the left side of the visual field

Question 22

Extinction

Answer 22

Milder form of neglect

They can see or detect stimuli on the left but only when nothing else is competing for their attention

A task they can do is tapping on the shoulder - when both taps are done for the patient they can only see one side and fail to acknowledge the left
If there’s only one side tapping, they can say right or left, but there’s two they can only acknowledge one at a time

If something is competing for their attention they can only acknowledge one side at a time

Question 23

What is Balint’s Syndrome caused by

Answer 23

It is caused by bilateral damage to the parietal cortex

Question 24

Three key symptoms of Balint’s syndrome

Answer 24

Simultagnosia

Optic Ataxia

Oculomotor apraxia

Question 25

Simultagnosia

Answer 25

Inability to attend and/or perceive more than one object at a time

Question 26

Optic Ataxia

Answer 26

Hand-eye coordination disrupted

Question 27

Oculomotor apraxia

Answer 27

Trouble moving eyes in a smooth way

Question 28

What is Balint syndrome

Answer 28

A rare disorder involving deficits in spatial attention and visual processing.

Question 29

Theoretical implications of Disorders of attention

Answer 29

Both disorders support the dorsal-ventral stream distinction: Neglect linked with ventral attention deficits. Balint’s more with dorsal stream dysfunction.

Question 30

Clinical relevance of neglect and Balint - early detection

Answer 30

Both neglect and Balint syndrome often emerge after stroke, traumatic brain injury (TBI), or neurodegenerative disease. Recognising these syndromes early can significantly influence treatment planning.

Question 31

Clinical relevance -assessment and screening

Answer 31

Clinical tools help detect these disorders: Neglect: Line bisection and clock drawing Balint: reaching tasks for optic ataxia

Question 32

Neglect

Answer 32

involves a lack of awareness of stimuli presented to the side of space on the oppo- site side to the brain damage (the contralesional side).

Question 33

Limitations of research into neglect - variability

Answer 33

It is hard to produce theoretical accounts applicable to all neglect or extinction patients because the precise symptoms and regions of brain damage vary considerably across patients.

Question 34

Limitations of research into neglect - Toba et al

Answer 34

Neglect patients vary in their precise processing deficits (e.g., Toba et al., 2018b), but this has been de-emphasised in most theories.

Question 35

Limitations of research into neglect - limited explanation

Answer 35

The precise relationship between neglect and extinction remains unclear. The dorsal and ventral networks generally interact but the extent of their interactions remains to be determined.

Question 36

How is neglect linked to the Ventral Attention Network

Answer 36

The ventral network helps detect salient, unexpected stimuli Neglect arrises when this system is damaged - the brain fails to refocus its attention to stimulus on the left side because of impaired bottom-up attention shifting

Question 37

How is Balint's syndrome linked to the Dorsal stream

Answer 37

Dorsal stream supports spatial awareness, eye movements and visually guided actions Balint’s reflects a disruption in top-down spatial processing and spatial attention, tied to the dorsal attention network.