1. The Lesioned Brain Flashcards
TMS uses electromagnetic induction to:
disrupt brain activity via neural noise. If the neurons are needed for a cognitive function, it will be disrupted
What can TMS tell us
if certain neural regions and needed for a specific task
Being able to control the location affected, being transient/reversible, and providing a causal link between brain regions and behaviour are advantages of which brain technique
TMS
brain activity in a control task is subtracted from activity in an experimental task
Cognitive subtraction
How do you generate an ERP
measure populations of neurons producing electric field at scalp (EEG). Average these and link to stimulus onset to get ERP.
What does cognitive subtraction show?
a brain region that is active in a certain condition relative to another
A form of TES, tDCS can increase or decrease firing of neurons. Anodal stimulation has __ (excitatory/inhibitory) effects by inhibiting __ (GABA/Glutamate)
- excitatory
- GABA
In tDCS, cathodal stimulation leads to __ (excitation/inhibition), by inhibiting (GABA/Glutamate)?
- inhibition
- Glutamate
TMS involves disrupting neuronal firing leading to task disruption. TES, on the other hand, affects neurons by:
changing neuronal excitability, modulation.
This type of TES uses low level alternating current between anode and cathode to synchronise brain rhythms/cause phase locking
tACS
Name the type of neuropsychology: what function is disrupted by damage to region X? Functional specialisation.
Classical neuropsychology
Name the type of neuropsychology: can a particular function be spared/impaired relative to others? Single case methodology.
Cognitive neuropsychology
What is an ischaemic stroke?
- blood clot
- lack of blood and O2 to brain
- cells die
What is a haemorrhagic stroke?
- bleeding into brain
- weakened blood vessels
- neurons die
Patient is impaired on task X, but spared on task Y. What is this? What about if they’re normal on task Y?
- Single dissociation
- classical single dissociation
Patient is impaired on task X and Y, but significantly more impaired on task X. This is:
- strong single dissociation
Double dissociation
Patient is impaired on X but not Y. Another patient, with different injury, is impaired on Y but not X.
What type of dissociation can rule out task-resource artifacts (patient misunderstanding task or using wrong strategy)
Double dissociation
Can be grouped by syndrome, behavioural symptoms, or lesion locations
Group studies
alpha band oscillations in ERP have been linked to which cognitive process?
Attention and filtering irrelevant information.
Gamma band oscillations in tACS have been linked to:
lucid dreaming
What type of imaging is based on the fact that different types of tissue (e.g., skull, gray matter, white matter, cerebrospinal fluid) have different physical properties.
Structural imaging - MRI, CT
This type of imaging measures temporary changes in brain physiology associated with cognitive processing; the most common method is fMRI and is based on a hemodynamic measure.
Functional imaging
This type of imaging measures spatial, permanent characteristics of the brain
Structural imaging - eg MRI and CT
The ERP wave N170 and P300 are associated with processing of what?
N170 - face processing
P300 - famous faces
Biomarker for AD from ERP technique
Reduced P300 wave
This imaging technique measures magnetic fields using SQUIDs, is non invasive, has good temporal AND spatial resolution
Magnetoencephalography (MEG)
This technique measures local blood flow, radioactive tracer attached to glucose which decays and emits a positron
Positron Emission Tomography (PET)
Measures deoxyhaemoglobin (BOLD response), change in BOLD over time, voxels (volume pixels) has high spatial and low temporal resolution
fMRI
This scanning technique measures white matter organisation by assessing the diffusion of water from the axons
Diffusion Tensor Imaging (DTI)
What can you group patients by in group studies
- syndrome
- behaviour
- lesion location
measures brain activity based on blood volume
PET
This technique has a limited temporal capacity but very good spatial resolution
fMRI
Describe single cell recording and its limitation
- electrode inserted into axon or just outside axon membrane
- can be done in conscious animals due to absence of pain receptors
- stimulus presented to visual field. if in neurons RF, neuron will fire and get electrical signal
- cant be done in humans
EEG measures changes in __ between electrodes
potential difference/voltage
How many electrodes are in an EEG system and how are they named?
- 10-20
- letters correspond to location: X frontal, P parietal, O Occipital, C central
ERP peak for faces
N170
ERP peak for familiar or famous faces
P300
ERP peak range where name of a person is recalled
P400-P600
A potential biomarker of AD obtained by ERG
a decreased P300 peak
fNIRS - what is it and limitation
light in the IR range is scattered differently by oxygenated vs deoxygenated haemoglobin
- cant see deeper structures
what is iEEG/ECoG
- grid of electrodes to map function placed in brain during neurosurgery
- records electrical activity of many thousands of neurons
The only imaging technique with very high resolution in spatial and temporal
iEEG or ECoG
Advantages of TMS
- virtual lesion technique
- reversible and transient
- controllable location
- provides causal link
- can do within subjects design
TMS to different sides of the brain in language lateralisation and degree of lateralisation showed that
disruption of language due to lesion is correlated with the degree and side of lateralisation
- TMS to highly lateralised side = lower RT
- TMS to less lateralised side = higher RT because more resources available for other side of brain
What are the types of TES
tDCS, tACS and tRNS
strong single dissociation
patient is impaired on both tasks, but significantly more impaired one one than the other
when writing, omitted all vowels. Speechless but could use gestures. Name of patient and type of dissociation
patient CF, classical single dissociation
what is the dissociations between LATL atrophy and RATL?
LATL patient equally impaired on social and nonsocial tasks. RATL patient sig more impaired on social, but still impaired on nonsocial
Caramazza’s assumptions for cognitive neuropsychology single case studies
- fractionation: damage –> selective cognitive lesions
- transparency: lesion affects component of cognitive system but doesnt result in new. Can study the abnormal to understand normal
- universality: all cognitive systems the same
