Connectivity analysis of somatosensory evoked potentials in patients with major depression. Analysis of connectivity

Connectivity analysis was used to investigate the processing of intracutaneous stimuli and directed interactions within the pain matrix in patients with major depression (MD) and healthy controls (HCs), by means of frequency selective generalized partial directed coherence (gPDC).

Eighteen patients with MD and 18 HCs underwent stimulations consisting of moderately painful intracutaneous electrical stimuli to the right and left middle fingers. Connectivity analysis was based on nine selected EEG electrodes.

Stimulus-induced changes of the gPDC in a pre/post stimulus comparison and changes in the connectivity pattern in the post-stimulus condition were found. We could identify network changes correlating to the side stimulated, as well as differences between HCs and MD patients.

These data support the suggestion that pain processing in response to noxious stimulation in MD patients is different compared to healthy controls, suggesting aberrant functional connectivity. Generalized partial directed coherence is shown to be a promising method to detect changes in connectivity in both within- and between-subject designs.