Week 2 Flashcards
What neuroanatomical model of affective disorders is referenced as the most advanced?
The model by Price and Drevets
This model includes many brain regions and speculates on the relationship between the medial frontal cortex and subcortical areas.
Which brain regions are included in the Price and Drevets model?
- Medial frontal cortex
- Frontopolar cortex
- Ventral striatum
- Hippocampus
- Amygdala
These regions are part of the limbic system.
According to Price/Drevets, activation of the medial frontal cortex is related to what?
It is related to self-reference or the default system.
However, we saw that the medial frontal area was also connected to reference to others. This may be a limitation of the moedel.
The medial frontal cortex is also activated when thinking about others. Limitations!
What is a key takeaway regarding affective disorders, that has general consensus?
Affective disorders are network conditions affecting networks of frontal and subcortical regions
The specifics of this disruption are not well understood.
What concerns are raised about current anatomical models of affective disorders?
- Unclear relationships between symptoms and psychological components
- Poorly tested hypotheses on the relationship between neuroanatomical structures and psycological functions.
- Similar neuroanatomical structures across different disorders without specificity
- Inadequate modeling of mood state differences and trait vulnerabilities
These concerns suggest limitations in understanding affective disorders.
What does functional MRI measure?
Blood oxygenation level dependent effects (BOLD effects)
BOLD effects are measured relative to a baseline condition.
What is the significance of local field potentials in fMRI studies?
They correspond to the summation of many neurons firing
Local field potentials can be recorded from electrodes placed in the brain.
What is the ‘whole brain illusion’ in fMRI studies?
The assumption that activity is measured across the whole brain, which is not true due to signal dropout in certain areas
This dropout occurs near air-filled cavities or bones.
What is the problem of multiple comparison correction in fMRI studies?
It decreases statistical power due to the large number of statistical tests conducted across brain voxels. The idea is to correct so that you can isolate the real reasons of why something is happening, and minimize false positives.
A hypothesis should be established before data analysis to mitigate this issue.
What is the BOLD effect and its limitations?
The BOLD effect is slow, peaking after several seconds
For measuring fast activity, EEG is more suitable.
What is the relationship between fMRI activation and task necessity?
Task necessity = that that region was necessary for the task
Activation may show regions not necessary for the task
Determining necessity requires lesion studies or virtual lesion studies.
What findings were reported in Sachar et al., 2012 regarding major depression?
- Decreases in grey matter volume in medial frontal areas
- Abnormalities in the ventral striatum
- Abnormalities in subgenual metabolism
These findings highlight structural differences between patients and healthy controls.
What were the findings of the meta-analysis comparing major depression and healthy controls regarding brain activation?
Hamilton 2012
- Increased amygdala activation in depression
- Increased dorsal medial frontal cortex activation
- Increased lateral frontal cortex activation in healthy controls
The overall network involved is reproducible, but specific directional effects can be unclear.
What is the approach taken in the meta-analysis comparing bipolar disorder to schizophrenia?
Hamilton 2012
It controls for distress levels and medication effects
This method helps address confounding factors that affect brain region analysis.
What confounding factors were controlled for in meta-analyses of bipolar disorder?
Amone, 2009
- Mood stabilisers
- Anti-psychotics
- Antidepressants
- Slice thickness
These factors significantly impact the analysis of brain regions of interest.
What do we mean by reverse inference?
That we may infer that since a specific brain region activated during an fMRI, then it means that it is part of the psychological function. This can lead to complete misinterpretation of data.
Solution can be to deactivate such areas, or create lesions, which is costly too.
Why is it good practice to have an hypothesis to test, with fMRI?
Because it allows to test for specific variables, and avoid the possibility of too many variables and false positives, which brings down the statistical power of the research
How much of the signal is the BOLD Effect? And why does this matter?
2%. This is important to know since tasks may need to be repeated multiple times to obtain valid data.
Researchers, therefore, can only fit so many tasks/experiments in one.
What can be done to overcome the challenge of fMRI showing activations in areas not relevant to the task?
Lesion or deactivation (transcranial magnetic stimulation TMS)
What does “optimized sequence” mean?
In fMRI, optimized sequences allow to collect higher quality images - especially in areas of the brain where the signals is interrupted (like bones, or ocular cavities).
Potentially, consider they will lowere the statistical power of what has been found - since they may not be accurate.
