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Cognitive Neuroscience > The lesioned brain > Flashcards

The lesioned brain Flashcards

1
Q

How does TMS work?

A
  • Have a TMS coil current
  • creates a magnetic field pulse
  • rapid rate of change of magnetic field
  • induced electric field
  • induced tissue current
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2
Q

Why do we use TMS?

A
  • to see whether areas in the brain are necessary for the task or are just engaged in the task
  • TMS will interfere with the relevant neural signal when doing a task and you should observe a change in behaviour or speed of response of the task. Using this we can see if the area is critical or supporting a certain task
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3
Q

What are the advantages of TMS?

A
  • interference/ virtual lesion technique
  • transient and reversible
  • controls location of stimulation
  • Establishes a causal link of different brain areas and a behavioural task
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4
Q

What is the TMS study that states that the degree of language lateralisation determines susceptibility to unilateral brain lesions?

A
  • some people are either right or left language dominant
  • these people were bought to the lab. A TMS experiment was given where they were given a picture word verification task (does the word match the picture)? and reaction time and accuracy were measured
  • when TMS was applied the side of lateralisation they found language disruption correlated to this.
  • When left vermis’s area stimulated area people who were left dominant were slower at word picture verification task and when right was stimulated they were quicker and vice versa for right dominant people
  • Also tells us about how the two hemispheres communicate with each-other. When non dominant hemisphere is stimulated people are faster at the task. This means that the dominant hemisphere has more resources to process the language and so we see faster responses
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5
Q

What is transcranial electric stimulation (TES)?

A
  • Not actually stimulation technique, it is a modulation technique – small amount of electrical stimulation applied
    TES uses low level (1-2 mA) currents applied via scalp electrodes to specific brain regions.
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6
Q

What are the different protocols for TES?

A
  1. Transcranial direct current stimulation (tDCS)
  2. Transcranial alteration current stimulation - tACS
  3. Transcranial random noise stimulation - tRNS
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7
Q

What is at the heart of the tDCS protocols for clinical application?

A

When applied in sessions of repeated stimulation, tDCS can lead to changes in neuronal excitability that outlast the stimulation itself.

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8
Q

What is the mechanism of TES?

A
  • We have an anode (positive) and cathode (negative) electrode
  • In direct stimulation (transcranial current stimulation - tDCS) current flows from the cathode to the anode
  • in alternating stimulation current flows from the anode to the cathode and back at a certain frequency which is pre-set
    1. Anodal: facilitation effects
    2. Cathodal: inhibition effect
    3. Sham (Control) - 30 sec stimulation
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9
Q

What does anodal stimulation inhibit?

A

GABA, therefore produces excitation

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10
Q

What does cathodal stimulation inhibit?

A

Glutamate: therefore produces inhibition

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11
Q

What does transcranial alternating current stimulation use?

A

low level (0.5 - 2mA) alternating currents applied via scalp electrodes to specific brain regions

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12
Q

What is the rationale behind tACS?

A

The entrainment (synchronisation) of internal brain rhythms with externally applied oscillating electric fields. The oscillatory fields cause phase-locking of a large pool of neurons, leading to increases of neural synchronisation at the corresponding frequency (because the brain has its own oscillating electric fields - so tACS can enhance certain frequencies at the frequency it is applied)

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13
Q

What waves are shown when people have lucid dreams?

A

Gamma waves in the frontal cortex - an activity pattern that is linked to consciousness but is nearly absent during sleep and normal dreaming

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14
Q

What did Voss et al do to induce lucid dreaming?

A
  • they measured the EEG in 27 participants who were not lucid dreamers. 2 minutes after Ps entered REM phase while tACS was applied for 30 seconds in the range of 2 Hz - 100 Hz. The participants were then immediately woken up to report their dreams on the LuCID scale. The EEG data showed that thte brain’s gamma activity increased during stimulation with 40 Hz and to a lesser degree during stimulation with 25 Hz
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15
Q

What are the two traditions of patient based neuropsychology?

A
  1. Classical neuropsychology

2. Cognitive neuropsychology

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16
Q

What is classical neuropsychology

A
  • What functions are disrupted by damage to region X?
  • Addresses questions of functional specialisation, converging evidence to functional imaging. Tends to use group study methods
17
Q

What is Cognitive neuropsychology?

A

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
18
Q

What is a single dissociation?

A

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

19
Q

What is referred to by a classical single dissociation?

A

When the patient performs within the normal range on task B

20
Q

What is meant by a strong single dissociation?

A

When a patient is impaired on both tasks but is significantly more impaired on one task

21
Q

What is double dissociation derived from?

A

2 or more single cases with complementary profiles. E.g Broca’s Aphasia vs Wernicke’s Aphasia

22
Q

What is the difference between Broca’s and Wernicke’s Aphasia

A
  • Broca’s Aphasia: production aphasia: difficul;ty with language production but understand language quite well
    Wernicke’s aphasia: more difficulty with the meaning of language but has relatively fluid speech
23
Q

What are issues with single case studies?

A
  • lesion needs to be assessed for each patient and we have no guarantee that the same anatomical lesions have the same cognitive effect in different patients
  • therefore, the cognitive profile of each patient needs to be assessed separately from other patients
  • we cannot average observations from single studies because each patient may have a different cognitive lesions that we cannot know a priori
24
Q

How are brain lesioned studies usually graphed?

A

As a series of single case studies

25
Q

What are the different types of ways neuropsychological studies are grouped?

A
  1. Group by syndrome: useful for investigating neural correlates of a disease pathology but not for dissecting cognitive theory
  2. Group by behavioural syndrome: can potentially identify multiple regions that are implicated in behaviour
  3. Group by lesion location: useful for testing predictions derived from functional imaging

Cognitive Neuroscience (9 decks)

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