the lesioned brain

Question 1

What is TMS?

Answer 1

Transcranial Magnetic Stimulation

means of disrupting normal brain activity by introducing neural noise - ‘virtual lesion’

Question 2

how does TMS work?

Answer 2

• TMS coil current
• magnetic field pulse
• rate of change of magnetic field
• induced electric field
• induced tissue current

Question 3

TMS- Faraday’s coil

Answer 3

if apply current of electricity through one side of coil, will generate a magnetic field

if varies enough, can generate current in another part of the coil

Question 4

What is the aim of TMS studies?

Answer 4

applying a pulse at any cortical node of the neural network will interfere with the relevant neural signal

efficacy of neural signal is degraded

observe change in behaviour

Question 5

what are the advantages of TMS?

Answer 5

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

Question 6

what is language lateralisation?

Answer 6

language is a function of the left side of brain (generally)

Question 7

comparing left and right language dominant people

Answer 7

given semantic task, then TMS

when you stimulate the dominant side, that side is inhibited

so therefore it cannot inhibit the actions of the opposite side

Question 8

What is TES?

Answer 8

Transcranial electric stimulation

produces weak current applied via scalp electrodes to specific brain regions

promising results in therapy

Question 9

what are the different protocols for TES?

Answer 9

tDCS: transcranial direct current stimulation

tACS: transcranial alternating current stimulation

tRNS: transcranial random noise stimulation

Question 10

effect of repeated stimulation of tDCS

Answer 10

lead to changes in neuronal excitability that outlast the stimulation itself

clinical application

Question 11

TES protocols - tDCS

Answer 11

1. anodal: facilitation effects
2. cathodal: inhibition effects
3. Sham (control): 30s stimulation

Question 12

how do neurotransmitters work in tDCS?

Answer 12

anodal stimulation inhibits GABA (inhibitory neuro.)

cathodal stimulation inhibits glutamate (excitatory neuro.)

Question 13

tACS

Answer 13

uses low level alternating currents applied via scalp electrodes to specific brain regions

Question 14

what is the rationale behind tACS?

Answer 14

entrainment (synchronisation) of internal brain rhythms with externally applied oscillating electric fields

oscillatory fields cause phase-locking of large pool of neurons –>

increases of neural synchronisation at corresponding frequency

Question 15

what is lucid dreaming?

Answer 15

an overlap between two states of consciousness

one in dreaming, one in wakefulness

transfer elements of waking consciousness into the dream

Question 15

Voss et al: lucid dreaming

Answer 15

EEG for 27 ps, applied tACS

LuCID scale to report dreams

Question 16

how is lucid dreaming shown shown in EEG?

Answer 16

overlap of states is reflected in brain waves.

shows in gamma waves in frontal cortex, an activity pattern that is linked to consciousness but is nearly absent during sleep and normal dreaming

Question 16

Voss et al: results

Answer 16

brain’s gamma activity increased during stimulation with 40Hz, and lesser degree with 25Hz

insight and dissociation (control over plot only with 25Hz)

Question 17

both TMS and TES can cause…

Answer 17

after-effects on excitability of neurons and networks that outlast stimulation by mins/hrs

Question 18

TMS and TES combined with behavioural training…

Answer 18

can offer promising alts to pharmacological interventions and can enhance cognitive performance

Question 19

what is Neuropsychology and what traditions?

Answer 19

studying brain damaged patients - gives insight into formal function

classical neuropsychology and cognitive neuropsychology

Question 20

what is classical neuropsychology?

Answer 20

what functions are disrupted by damage to region x?

Addresses questions of functional specialization, converging evidence to
functional imaging

Tends to use group study methods

Question 21

what is cognitive neuropsychology

Answer 21

Can a particular function be spared/impaired relative to other cognitive functions?

Addresses questions of what the building blocks of cognition are (irrespective of
where they are)

Tends to use single case methodology

Question 22

forms of brain damage

Answer 22

Cerebrovascular accident (CVA or stroke)

Neurosurgery (split brain)

Viral infections (HSE, HIV)

Tumour (glioma)

Head injury (traffic accidents, rugby)

Neurodegenerative disease (Dementias: Alzheimer type)

Question 23

what is a stroke and what are the 2 types?

Answer 23

loss of brain function after disturbance of blood supply Ischemia and haemorrhage

Question 23

What is ischemia?

Answer 23

blood clot stops flow of blood to area of brain (lack of glucose and oxygen supply)

Question 24

what is a haemorrhage?

Answer 24

weakened blood vessels rupture and leak into brain tissue (bleeding into brain tissue)

Question 25

what is the aim of neuropsychological testing?

Answer 25

Assess what they can do after having a stroke: semantic memory: pyramids and palm trees/pine tree, which one is related? visuospatial testing: figure of ray - draw from memory

Question 26

what is a single dissociation?

Answer 26

If a patient is impaired on a particular task (Task A), but relatively spared on another task (Task B)

Question 27

what is a classical single dissociation?

Answer 27

If patient performs within the normal range on the Task B (spared task)

Question 28

what is a strong single dissociation?

Answer 28

If patient is impaired on both tasks, but is significantly more impaired on one task

Question 29

Patient CF

Answer 29

classical single dissociation at time of stroke, was completely speechless but could communicate through gestures writing: systematically omitted vowels (another patient made errors on only consonants)

Question 30

what does Patient CF tell us about cognitive neuropsychology?

Answer 30

behind these single dissociations is that a difficulty in one domain, relative to an absence in difficulty in another domain can be used to infer the independence of these domains comparing 2 patients: conclude that brain has separate neural resources for processing vowels and consonants

Question 31

what is a double dissociation?

Answer 31

derived from 2 single cases with complementary profiles: lesion of brain area A impairs function 1 but not function 2, while a lesion of brain area B produces the reverse pattern eg. Broca's aphasia and Wernicke's aphasia

Question 32

what are the issues with single case studies?

Answer 32

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 33

how are group studies grouped?

Answer 33

by syndrome by behavioural symptoms by lesion location

Question 34

grouping studies by syndrome

Answer 34

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

Question 35

grouping studies by behavioural symptoms

Answer 35

Can potentially identify multiple regions that are implicated in a behaviour

Question 36

grouping studies. by lesion location

Answer 36

Useful for testing predictions derived from functional imaging

Question 37

what are 3 methods for studying the lesioned brain?

Answer 37

TMS tDCS Neuropsychology