noninvasive methods

Question 1

What is transcranial magnetic stimulation (TMS), and how does it disrupt normal brain activity?

Answer 1

Transcranial Magnetic Stimulation (TMS) is a technique used to disrupt normal brain activity by introducing a neural noise, often referred to as a “virtual lesion.”

Question 2

Explain the concept of a “virtual lesion” induced by TMS. How does it relate to cognitive functions?

Answer 2

A “virtual lesion” induced by TMS occurs when neurons under the stimulation site are activated, disrupting cognitive functions associated with those neurons. If the stimulated area is involved in the ongoing task, this disruption occurs, leading to the term “virtual lesion.”

Question 3

Describe the mechanism behind transcranial magnetic stimulation (TMS) and how it influences neural activity.

Answer 3

TMS works through electromagnetic induction. A change in current in a wire (the TMS coil) generates a magnetic field, which induces a secondary electric current in the neurons below the stimulation site. This current mimics neuronal firing patterns, interfering with ongoing cognitive processes.

Question 4

Differentiate between online and offline TMS protocols. Provide examples of their applications.

Answer 4

Online TMS protocols = delivering single pulses or short trains of pulses in synchronization with a cognitive task. Allows observation of immediate effects on task performance. For instance, disrupting visual search tasks with TMS applied to the V5/MT
Offline protocols = delivering TMS repeatedly over a period before the cognitive task is performed to influence cognition after the task.
Used in investigating language lateralization by applying it to language-related areas then assessing language performance afterward.

Question 5

How does TMS contribute to understanding functional contributions of specific brain regions during tasks?

Answer 5

TMS contributes to understanding the functional contributions of brain regions by selectively disrupting activity in those regions during tasks, revealing their roles in cognitive processes.

Question 6

Discuss the use of TMS in investigating competition in the brain, citing relevant research examples.

Answer 6

TMS is used to investigate competition in the brain by disrupting specific brain regions involved in different processes. For example, Walsh et al. investigated competition in visual processing by disrupting the visual motion perception region (V5/MT)
Improved search for targets in static images but imapaired performance for motion images

Question 7

Evaluate the advantages and disadvantages of transcranial magnetic stimulation (TMS) as a research tool in neuropsychology.

Answer 7

Advantages of TMS include its interference/virtual lesion technique, transient and reversible effects, and the ability to control the location of stimulation to establish causal links between brain areas and behavioral tasks. However, disadvantages include limitations in studying lesions beyond cortical areas, uncertainty about the spatial extent of stimulation effects, and difficulties in observing effects beyond slowed reaction times.

Question 8

What is transcranial electrical stimulation (TES), and how does it differ from TMS?

Answer 8

Transcranial Electrical Stimulation (TES) involves applying low-level (1-2 mA) currents via scalp electrodes to specific brain regions, differing from TMS in its mechanism and applications.

Question 9

Describe the different techniques of transcranial electrical stimulation (tDCS, tACS, tRNS) and their applications.

Answer 9

TES techniques include transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS), and transcranial random noise stimulation (tRNS). These techniques have been applied in various neurological and psychiatric conditions to modulate neuronal excitability and improve symptoms.

Question 10

How does tDCS (direct stimulation) work?

Answer 10

Stimulating pad placed over region of interest, control pad (SHAM) over site of no interest
Cathodal stim (negative to positive) = inhibition effects/performance disruption
Anodal stim (positive to negative) = facilitation effects/performance enhancement

Question 11

Give an example of a piece of research where tDCS has been used.

Answer 11

Stimulation of visual cortex = early visual N100 component and enhancement of detecting weak stim (cathodal stim had opposite effect)

Question 12

Explain the immediate and after-effects of anodal and cathodal transcranial direct current stimulation (tDCS).

Answer 12

Immediate:
Anodal tDCS increases spontaneous firing rates (depolarising neurons = more likely to fire)
Cathodal tDSC hyperpolarises neurons = less excitable and likely to fire
After: (cognition)
Anodal stimulation inhibits (inhibitory) GABA - leads to enhanced synaptic inhibition which improves cognitive function
Cathodal stimulation inhibits (excitatory) glutamate - leading to decreased synaptic excitation and cognitive performance

Question 13

How does tACS work?

Answer 13

Uses low level (0.5-2mA) alternating currents applied via scalp electrodes to specific brain regions.
This leads to the synchronisation of internal brain rhythms with the externally applied oscillating fields. The oscillatory fields cause phase-locking of neurons = inc neural synchronisation at corresponding freq

Question 14

What is a lucid dream, and how does it differ from normal dreaming? Explain its neural correlates.

Answer 14

A lucid dream involves an overlap between states of consciousness, incorporating elements of wakefulness into the dream state. The presence of gamma waves in the frontal cortex during lucid dreams reflects higher awareness and control.

Question 15

Describe the experimental setup and findings regarding the induction of lucid dreaming using transcranial alternating current stimulation (tACS).

Answer 15

In an experimental setup, EEG was measured while tACS was applied to induce lucid dreaming during REM sleep. Stimulation at gamma frequencies (40 Hz > 25Hz), increased gamma activity, correlating with reports of lucid dreaming experiences

Question 16

Summarize the potential applications and benefits of non-invasive brain stimulation techniques in cognitive enhancement and therapy.

Answer 16

Non-invasive brain stimulation has prominent effect on cognitive processes
TMS and tES combined with behavioural training can offer promising alternatives to pharmacological interventions and can enhance cognitive performance
TMS and tES can cause after-effects on excitability of neurons and networks that outlast the stimulation by minutes, even hours

Question 17

Compare and contrast classical neuropsychology and cognitive neuropsychology in terms of their methodologies and research objectives.

Answer 17

Classical neuropsychology - what functions are disrupted by damage to brain region X? Uses group study methods
Cognitive neuropsychology - doesn’t focus on regions but rather what the independent building blocks of our cognitive processes are. Uses case studies.

Question 18

What patients do cognitive neuropsychologists tend to study?

Answer 18

Stroke - loss of a brain function due to disturbance in blood supply
Ischemia stroke - lack of gluecose and O2 supply due to a clot
Menorrage stroke - bleeding into brain tissue leading to death of cells

Question 19

Define the following:
single dissociation
classical signal dissociation
strong single dissociation
double dissociation

Answer 19

single dissociation - impaired on Task A, relatively spared on Task B
classical signal dissociation - impaired on task A, completely spared in Task B
strong single dissociation - impaired on both tasks, but significantly more impaired on one than the other
double dissociation - comparison of two single dissociation with complementary profiles to conclude that the brain has different neural resources for each of the tasks (e.g processing written vowels vs constants)

Question 20

Outline patient CF’s classic single dissociation.

Answer 20

CF - suffered a stroke to left parietal areas and could only communicate through gestures.
Omitted vowels only in writing
( - other patient would omit constants = double dissociation)

Question 21

What is a strong single dissociation and what does it tell us?

Answer 21

If patient is impaired on both tasks, but is significantly more impaired on one task, this is referred to as a strong single dissociation
task A and task B utilize different cognitive processes with different neural resources.

Question 22

What are the risks when conducting researching for single disassociations?

Answer 22

Task-resource artifact - Both task A and task B use exactly the same cognitive/neural resources as each other, but task B requires more of this resource than task A (i.e., task B is harder). If brain damage depletes this resource, then task B may be relatively or selectively impaired

Task-demand artifact - patient performs one of the tasks suboptimally- patient may have misunderstood the instructions or have adopted an unusual strategy for performing the task

(clear instructions, intelligence test)

Question 23

Discuss the significance of double dissociations in neuropsychological research of language.

Answer 23

Double dissociations involve two single dissociations with complementary profiles of capabilities. For example, damage to Broca’s area impacts speech production but leaves comprehension intact, while damage to Wernicke’s area specifically impairs comprehension while sparing speech production (tells us that the brain has different areas for language processing)

Question 24

What are the strengths and limitations of using single case studies in neuropsychological research?

Answer 24

• good for determining different components of cognitive systems
• lesions might have varying impacts on people (unique cognitive profiles, or different lesions)
• don’t have prioir - can’t average observations

Question 25

What are the strengths and limitations of using group studies in neuropsychological research?

Answer 25

• good for establishing lesion-deficit associations
• attempts to find causal links over correlations (like imaging studies)
• may overlook variability within a group

Question 26

How are patients grouped in neuropsychological group study research?

Answer 26

behavioural syndrome - investigates neural correlates/lesions for cluster of symptoms
behavioural symptom - identify regions/lesions which are implicated with specific behaviour
lesion location - tests predictions of imaging research and tests behavioural symptoms

Question 27

Outline how TMS has been used to investigate language lateralisation.

Answer 27

Language lateralisation determines suceptibility to a unilateral brain lesions
Most people are left side dominant - applying TMS would impact performance
People who are right side dominant - applying TMS to right would have same effect

Question 28

Outline the clinical applications of tDCS.

Answer 28

When applied in sessions of repeated stimulation, leads to changes in neuronal excitability which outlast the stimulation itself. Such aftereffects are used to treat dementia, strokes, Parkinsons etc