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The Neurobiological Impact of High Frequency Repetitive Transcranial Magnetic Stimulation on the Underlying Neurocircuitry of Depressed Mood

Thursday, 11 June, 2009 - 17:00
Campus: Brussels Health Campus
Faculty: Medicine and Pharmacy
auditorium P. Brouwer
Chris Baeken
phd defence

Repetitive Transcranial Magnetic Stimulation
(rTMS) is safely used to treat psychiatric
illnesses, especially major depression. By using
TMS ‘off-line’ paradigms, the main purpose of this
thesis was to evaluate the neurobiological effects
of fixed high frequency (HF)-rTMS parameters on
mood changes in healthy subjects, as well as in
unipolar TRD patients of the melancholic subtype.
The absence of HF-rTMS effects on the HPA-axis
in non-depressed subjects, in contrast to the
effects found in depressed individuals could imply
that the neurobiological influences of HF-rTMS
are specific for a given pathophysiological
condition. The ‘hypersensitive’ HPA-axis, only
observed in HF-rTMS non-responders, indicates
that only those depressed patients with some
kind of ‘normal or preserved’ cortico-subcortical
neurocircuitries could be susceptible to this kind
of treatment. In line with these assumptions, TRD
patients displaying metabolically more active
fronto-cingulate networks responded better to
multiple HF-rTMS sessions. Furthermore, our
results indicate that HF-rTMS treatment affects
(pre)frontal cortical and hippocampal 5-HT2A
receptor binding indices in a different way,
depending as to where these receptors are
located in the brain. In short, our results
demonstrate that HF-rTMS has immediate and
prolonged neurobiological effects on the selected
pathophysiological systems we examined in
melancholic TRD patients. Furthermore, our
results support the choice of the left DLPFC as a
valid HF-rTMS target site to intervene with the
neuronal pathways deregulated in major
depression.