The Lesioned Brain, Lecture 2

Question 1

What are some examples of brain damage?

Answer 1

-> Cerebrovascular accident (CVA/stroke)
–> Neurosurgery (split brain)
—> Viral infections (HSE, HIV)
—-> Tumour (glioma)
—–> Head injury
——> Neurodegenerative diseases

Question 2

What is a stroke?

Answer 2

A loss of brain function as a result of disturbance to blood supply

Question 3

What is neurophysical testing?

Answer 3

Intelligence, memory, visuospatial, executive functions, sensations.

Question 4

Classical single dissociation

Answer 4

Classical single dissociation is a neuropsychological method that involves studying individuals with brain damage to investigate the functional organization of the brain.
It involves comparing the performance of individuals on different tasks to identify the presence or absence of impairments in specific cognitive domains.

Question 5

Patient CF

Answer 5

Patient CF is a 43-year-old, right-handed engineer who suffered an ischemic stroke to the left parietal area (angular gyrus – AG).
At the time of examination, CF was unable to speak but communicated through gestures.
CF wrote with his left hand due to right hemiplegia.

Question 6

CF’s writing performance

Answer 6

When CF wrote words, he systematically omitted vowels only.
The selective omission of vowels indicates a dissociation between the cognitive processes responsible for the recognition and production of vowels and consonants.
This suggests that the neural resources for processing vowels and consonants are independent of each other.

Question 7

Kay and Hanley’s patient

Answer 7

Kay and Hanley reported another patient who made spelling errors selectively on consonants.
The selective errors on consonants provide further evidence for the dissociation between the cognitive processes responsible for the recognition and production of vowels and consonants.
The findings suggest that different neural resources are involved in the processing of vowels and consonants, supporting the modular organization of the brain.

Question 8

Double dissociation

Answer 8

Double dissociation is a neuropsychological method used to investigate the functional organization of the brain.
It involves studying two or more cognitive processes and comparing their performance in two or more groups of individuals who have sustained different types of brain damage.
The method is used to show that different cognitive processes are controlled by different neural resources in the brain.

Question 9

Two single cases with complementary profiles

Answer 9

The double dissociation method is derived from two or more single cases with complementary profiles.
The complementary profiles refer to two or more groups of individuals with different types of brain damage who perform differently on different tasks.
If one group performs better on one task than the other, and the second group performs better on a different task than the first group, then a double dissociation is said to have occurred.

Question 10

Separate neural resources for processing written vowels and consonants

Answer 10

The brain has separate neural resources for processing written vowels relative to consonants.
This is supported by the findings of double dissociation studies, where individuals with brain damage show selective impairments in processing vowels or consonants.
The findings suggest that the neural resources for processing vowels and consonants are independent of each other.

Question 11

Implications of double dissociation for cognitive and neural resources

Answer 11

The findings of double dissociation studies have important implications for our understanding of cognitive and neural resources in the brain.
They suggest that different cognitive processes are controlled by different neural resources, supporting the modular organization of the brain.
The method provides a powerful tool for investigating the functional architecture of the brain and can be used to identify the neural mechanisms underlying a wide range of cognitive processes.

Question 12

What are the issues with single case studies?

Answer 12

Lesions need to be assessed for each patient, and there is no guarantee that same anatomical lesions have same cognitive effect in different patients. Therefore, cognitive profile of each patient needs to be assessed separately.

Question 13

Space in the brain

Answer 13

The brain does not regard space as a continuous single entity.
Space exists in different forms in the brain, including retinocentric, egocentric, and allocentric space.
Cross-modal perception, integrating information from different senses, is necessary to locate things in space.

Question 14

Topic Attention

Answer 14

Attention is the process by which certain information is selected for further processing while other information is discarded.
Attention is necessary because of the limited capacity to process all received information.
Attention is typically directed to locations in space, and is often likened to a spotlight metaphor.

Question 15

Spotlight metaphor of attention

Answer 15

The spotlight metaphor of attention suggests that attention is like a spotlight that can move from one location to another, and can zoom in or out.
The location of attention is not necessarily the same as eye fixation, although there is a natural tendency for attention and eye-fixations to go together.
Attention has limited capacity, so not everything can be illuminated.

Question 16

Control of the spotlight

Answer 16

The spotlight of attention can be controlled exogenously, meaning it is externally guided by a stimulus, such as in visual search.
Inhibition of Return (IOR) is a phenomenon where there is a slowing of processing speed when going back to a previously attended location.
The control of attention is an active process and is influenced by both bottom-up and top-down factors.

Question 17

What is feature integration theory?

Answer 17

Feature Integration Theory (FIT) proposes that perceptual features are encoded in parallel and prior to attention, and unique features may be detected without attention while shared features require serial search.

Question 18

What do the parietal lobes do in terms of processing?

Answer 18

Parietal lobes are specialized for spatial processing and are part of the “where” and “how” routes, with the dorsal pathway reaching into parietal lobes for spatial processing and guiding movements, and the ventral pathway reaching into temporal lobes for object recognition.
The parietal lobes bring together different types of spatial representation needed for action and integrate visual space with body space.

Question 19

What are the two main attention networks?

Answer 19

A dorso-dorsal network involving lateral intraparietal area (LIP) and frontal eye fields (FEF), and a ventro-dorsal network involving the right temporoparietal junction and ventral frontal cortex.
The dorso-dorsal network controls attention to locations in space, while the ventro-dorsal network interrupts ongoing tasks to divert attention.

Question 20

Neglect

Answer 20

Definition: Neglect is a condition in which patients fail to attend to stimuli on the opposite side of space to their lesion, most commonly following a stroke to the right hemisphere of the brain.

Neuroanatomy: Neglect is associated with lesions in the parietal association cortex, which integrates multiple sensory signals and has extensive connections with frontal areas.

Clinical Picture: Patients with neglect do not suffer from primary disorders of perception, sensation, or movement, but may fail to attend to stimuli in the affected side of space. Neglect can affect different modalities, including visual, auditory, and somatosensory.

Question 21

Types of neglect

Answer 21

Perceptual vs. representational neglect: Neglect can affect both perceptual and representational aspects of external and imagined space, with compromised information on the left side.
Neglect for near vs. far space: Patients with neglect can have impairments in near space (line bisection using pen and paper) but be spared in far space (tested with a light pointer).
Personal vs. peripersonal space: Patients can have body neglect (failure to attend to the left side of their body) or near space neglect (failure to attend to the left side of external objects).
Within objects vs. between objects: Object-based neglect involves attending to objects on the left side of space but omitting to attend to one-half of the object itself. Space-based neglect involves attending to one-half of space while ignoring the other half.
Spatial vs. object-based neglect: Patients with object-based neglect may not detect differences on the left side of an object, even when it falls into the right side of space.

Question 22

What are the parietal lobes roles in neglect?

Answer 22

The right parietal lobe contains a richer representation of space than the left parietal lobe, leading to a tendency to attend to the left side of space (pseudoneglect).
Lesions in the left parietal lobe can result in less severe neglect and faster recovery than lesions in the right parietal lobe.

Question 23

Neglect and Extinction

Answer 23

Also known as unilateral neglect, spatial neglect, or hemispatial neglect.
Patients fail to attend stimuli on the opposite side of space to their lesion.
Most prominent following a stroke to the right hemisphere of the human brain.
Neglect can arise from different mechanisms, including the loss of neurons dedicated to the representation of that space or a failure to shift attention to that side.
Patients may fail to attend to the left side of space, shave, groom, and dress only one side of the body, or fail to read the left side of words printed anywhere on the page.

Question 24

Neglect as a Disorder of Attention and Not Low-Level Perception

Answer 24

Neglect patients still activate visual regions in occipital lobes for the information they claim not to be aware of.
They are often able to detect objects on the left if cued there.
Affects auditory and tactile judgments as well as vision.
The phenomenon of visual extinction suggests different perceptual representations are competing for attention.

Question 25

Rehabilitation of Neglect: Prism Adaptation:

Answer 25

Patients wear prism lens glasses that shift their view to the right.
When asked to point at objects, they make errors by missing to the right.
Visual feedback allows them to compensate for the errors and correct towards the left.
The deviation towards the left persists after the prism lenses are removed, producing a relatively long-lasting improvement in symptoms.

Question 26

Effects of Video Games on Perceptual and Motor Skills:

Answer 26

Perceptual learning is specific to trained tasks.
Action video game playing can alter a range of visual skills.
Regular video game players show less activation in brain regions linked to attention when searching for specific objects.

Question 27

Test of Variables of Attention (TOVA):

Answer 27

Assesses impulsivity and sustained attention.
Measures the ability to respond quickly to rare targets and withhold responding to non-targets.

Question 28

Dye et al., (2009):

Answer 28

Used TOVA to assess impulsivity and sustained attention in non-video game players and habitual video game players.
Results show that habitual video game players are overall faster and have enhanced attentional control.

Question 29

Can Video Games Keep Mental Decline at Bay?:

Answer 29

Cognitive control is a set of neural processes that allow us to interact with our complex environment in a goal-directed manner.
Video games have the potential to improve cognitive control and possibly slow down mental decline.

Question 30

Transcranial Direct Current Stimulation (tDCS) and Multitasking:

Answer 30

The dorsolateral prefrontal cortex (DLPFC) is thought to be important for multitasking.
Anodal tDCS or sham tDCS was applied over left DLPFC in healthy young adults before they played a 3-D video game designed to assess multitasking performance.

Question 31

What were the results from the anodal tDCS study?

Answer 31

The anodal tDCS group showed enhanced multitasking performance and decreased multitasking cost during the second session, indicating delayed cognitive benefits of tDCS.
Performance benefits were observed only for multitasking and not on a single-task version of the game.
This study provides evidence of how custom-designed video games can be used to assess and enhance cognitive abilities across the lifespan.