Glutamate modulates resting state activity in the perigenual anterior cingulate cortex - a combined fMRI-MRS study.

The perigenual anterior cingulate cortex (PACC) shows high resting state activity and is considered part of the default-mode network (DMN). However, the biochemical underpinnings of the PACC's high resting state activity remain unclear. While animal-based evidence points toward a role for the glutamatergic system, the modulation of the resting state activity level by itself as distinguished from stimulus-induced activity remains to be shown in humans. Using combined fMRI-MRS in healthy subjects, we here demonstrate that the PACC resting state concentration of glutamate is directly related to the level of resting state activity in the same region. In contrast, no such relationship could be detected during the anticipation of reward and punishment, nor in an independent control region (the left anterior insula). Taken together, our findings demonstrate for the first time the modulation of the PACC resting state activity level by the concentration of glutamate in the same regions. This contributes to a better understanding of the biochemical basis for the brain's resting state activity as well as providing some clues regarding its apparent pathological upregulation in psychiatric disorders like the major depressive disorder.

The narcissistic self and its psychological and neural correlates: an exploratory fMRI study.

BACKGROUND: The concept of narcissism has been much researched in psychoanalysis and especially in self psychology. One of the hallmarks of narcissism is altered emotion, including decreased affective resonance (e.g. empathy) with others, the neural underpinnings of which remain unclear. The aim of our exploratory study was to investigate the psychological and neural correlates of empathy in two groups of healthy subjects with high and low narcissistic personality trait. We hypothesized that high narcissistic subjects would show a differential activity pattern in regions such as the anterior insula that are typically associated with empathy. METHOD: A sample of 34 non-clinical subjects was divided into high (n=11) and low (n=11) narcissistic groups according to the 66th and 33rd percentiles of their scores on the Narcissism Inventory (NI). Combining the psychological, behavioral and neuronal [i.e. functional magnetic resonance imaging (fMRI)] measurements of empathy, we compared the high and low narcissistic groups of subjects. RESULTS: High narcissistic subjects showed higher scores on the Symptom Checklist-90 - Revised (SCL-90-R) and the 20-item Toronto Alexithymia Scale (TAS-20) when compared to low narcissistic subjects. High narcissistic subjects also showed significantly decreased deactivation during empathy, especially in the right anterior insula. CONCLUSIONS: Psychological and neuroimaging data indicate respectively higher degrees of alexithymia and lower deactivation during empathy in the insula in high narcissistic subjects. Taken together, our preliminary findings demonstrate, for the first time, psychological and neuronal correlates of narcissism in non-clinical subjects. This might stipulate both novel psychodynamic conceptualization and future psychological-neuronal investigation of narcissism.