Lesioned Brain

Question 1

what is TMS?

Answer 1

• TMS: a means of disrupting normal brain activity by introducing neural noise – ‘virtual lesion’
• Uses the principle of electromagnetic induction

Question 2

who discovered TMS?

Answer 2

• Michael Faraday (1791-1867)

○ Faraday’s Coil

Question 3

How does TMS works?

Answer 3

TMS coil applies a magnetic current pulse to and area in the brain = induces electrical field = induced tissue current.

Question 4

why is TMS sometimes better than fMRI or PET?

Answer 4

• fMRI and PET give correlational evidence of brain activity but this isn’t definitive.
• TMS identifies regions that are responsible for certain tasks by inhibiting that area.

Question 5

what happens when TMS interferes with neural signals?

Answer 5

• efficacy of the neural signal will be degraded

- observe change in behaviour (RT change – it will take us longer to read)

Question 6

State the advantages of TMS.

Answer 6

• interference/virtual lesion technique.
• transient and reversible
• control location of stimulation
• establishes a causal link of different brain areas and a behavioural task

Question 7

What did Knecht et al., 2002 study?

Answer 7

how people recover from aphasia as a consequence of a stroke depending on lateralisation.

Question 8

What did Knecht et al., (2002) find?

aphasia recovery after stroke

Answer 8

• Language disruption correlated with degree and side of lateralization.
• Left dominant results:
  ○ When stimulated left side these Ps were slower
  ○ When stimulated right side Ps were faster in word picture verification task.
• Right dominant results:
  ○ Opposite to the left dominant participants.

Question 9

What is Transcranial electrical stimulation (TES)?

Answer 9

Not actually a stimulation technique because it is a modulation technique.
The amount of electrical stimulus is so low that it doesn’t stimulate but modulates the brain activity.

Question 10

What is tDCS?

Answer 10

Non-invasive stimulation of the brain caused by passing a weak electrical current through it.

Question 11

What is a Single Dissociation?

Answer 11

A situation in which a patient is impaired on a particular task (task A) but relatively spared on another task (task B)

Question 12

Define a double dissociation?

Answer 12

Two single dissociations that have a complementary profile of abilities

Question 13

Define Functional Integration

Answer 13

how one region influences another or how one cognitive function influences another.

Question 14

What are the 3 protocols for TES?

Answer 14

1. Transcranial direct current stimulation - tDCS
2. Transcranial alternating current stimulation -tACS
3. Transcranial random noise stimulation - tRNS

Question 15

How can tDCS be used?

Answer 15

Can be used to temporarily disrupt or boost cognitive function.

Question 16

What are the effects of Anodal, Cathodal tDCS.

Answer 16

Cathodal tDCS - Decreases cortical excitability and decrease in performance. (inhibts Glutamate)

Anodal tDCS - Increases cortical excitability and increases the performance. (inhibits GABA = excitation)

Question 17

How is Transcranial alternating current stimulation used?

Answer 17

• low level alternating currents applied via scalp electrodes to specific brain regions.
• can cause entrainment and enhance certain brain frequencies at the frequency that it is applied at = modulation of brain oscillations that are important for a certain task

Question 18

why are TMS and tES promising?

Answer 18

• TMS and tES combined with behavioural training can offer promising alternatives to pharmacological interventions and can enhance cognitive performance.

Question 19

Do TMS and tES have lasting effects?

Answer 19

TMS and tES can cause after-effects on excitability of neurons and networks that outlast the stimulation by minutes, even hours

Question 20

Describe Classical neuropsychology and its research methods.

Answer 20

• Addresses questions of functional specialization, converging evidence to functional imaging
• Tends to use group study methods

Question 21

Describe Cognitive neuropsychology and its research methods.

Answer 21

• Addresses questions of what the building blocks of cognition are (irrespective of where they are)
• Tends to use single case methodology

Question 22

What are the 2 types of Stroke and what causes them?

Answer 22

Ischemia (lack of glucose & oxygen supply)

Haemorrhage (bleeding into brain tissue)

Question 23

What are the issues with Single Case studies?

Answer 23

• Lesion needs to be assessed for each patient, and no guarantee that same anatomical lesions have same cognitive effect in different patients
• Therefore the cognitive profile of each patient needs to be assessed separately from other patients.
• one can not average observations from single studies because each patient may have a different cognitive lesion that we can not know a priori.

Question 24

What are the 3 categories for group studies?

Answer 24

• Group by syndrome
• Group by behavioural (or cognitive) symptom
• Group by lesion location

Question 25

Why are Group by syndrome studies useful?

Answer 25

useful for investigating neural correlates of a disease pathology (e.g. Alzheimer’s) but not for dissecting cognitive theory

Question 26

Why are studies grouped by behavioural (or cognitive) symptom useful?

Answer 26

Can potentially identify multiple regions that are implicated in a behaviour

Question 27

How are Group by lesion location studies useful?

Answer 27

Useful for testing predictions derived from functional imaging

Question 28

why are group studies important?

Answer 28

can be important for establishing whether a given region is critical for performing a given task or tasks.

Question 29

What are the problems with structural imaging techniques?

Answer 29

Swelling (oedema) and tumours can distort the true size and shape of the brain tissue. This may render neurons inoperative even if they are not destroyed. It is also makes it difficult to identify lesions.