currents (typically 1-2 mA) to the scalp for a few minutes through two surface electrodes, which can modulate cortical excitability. (Chrysikou & Hamilton, 2011, Restorative Neurology & Neuroscience; Hamilton, Chrysikou, & Coslett, 2011) Transcranial Direct Current Stimulation (tDCS)
excitability at the stimulation site through subthreshold neuron soma depolarization. ‣ Cathodal tDCS: decreases cortical excitability at the stimulation site due to neuron soma hyperpolarization. (Nitsche et al., 2008; Stagg & Nitsche, 2011)
Furthermore, faster naming responses correlated with decreased BOLD signal in Broca’s area. The data support the importance of Broca’s area within the normal naming network and as such indicate that Broca’s area may be a suitable candidate site for tDCS in neurorehabilitation of anomic patients, whose brain damage spares this region
activation in the left ventral IFG, an area speciﬁcally implicated in semantic retrieval processes. Under atDCS, resting- state fMRI revealed increased connectivity of the left IFG and additional major hubs overlapping with the language network. Meinzer et al. (2012)
changes in widespread brain areas compared with sham stimulation both during and after stimulation. Whereas bilateral tDCS predominantly modulated changes in primary and secondary motor as well as prefrontal regions, unilateral tDCS affected prefrontal, parietal, and cerebellar areas. No direct effect was seen under the stimulating electrode in the unilateral condition. The time course of changes in functional connectivity in the respective brain areas was nonlinear and temporally dispersed.
with a reduction in symptoms of about 30%.! This reduction persisted at follow-ups in studies where follow-ups were reported.! Signiﬁcant heterogeneity limits the interpretability and generalizability of the ﬁndings.
Unipolar depression is associated with negative affect, rumination, decreased motivation, and limited productivity.! Due to its massive individual and societal costs, much effort has been focused on the development of pharmacological and psychological interventions to alleviate the symptoms of depression. ! Although these treatments are effective for some patients, others fail to respond to such interventions alone.
over prefrontal cortex— holds promise for the treatment of depression and has useful characteristics such as low cost, ease of use, and reliable sham methodology ( Dell’Oso et al., 2010; Drevets, 2000; Ferrucci et al., 2009).! The optimal use of tDCS for reliable clinical beneﬁts in depression has not been fully explored. ! We are combining tDCS and fMRI to investigate the effects of neurostimulation on frontal cortical excitability during a negative thought regulation task in depressed and healthy control subjects. Functional Neuromodulation of PFC Activity with tDCS in Unipolar Depression
the frontal pole (a), and patients showed increased activity in the right precuneous (b) Controls showed increased activity of the left frontal pole (a), and patients showed increased activity in the left orbitofrontal cortex (b & c) Pre-tDCS > Concurrent tDCS Concurrent tDCS > Pre-tDCS
does alter cortical excitability in a manner that can be captured with fMRI.! Anodal stimulation is related to different activation patterns in depressed patients and controls.! Protocol Considerations:! Larger groups may help clean up behavioral comparisons. Increase current from 1.5mA?