Linking brain structures with symptoms : the role of the anterior cingulate cortex and a frontocingulate circuit in affective states

Linking brain regions or neural circuits to specific affective symptoms could help elucidate the neural mechanisms of affective states as well as antidepressant treatment effects. Much research has implicated the anterior cingulate cortex (ACC), mid-dorsolateral frontal cortex (MDLFC), and a "frontocingulate" (i.e., MDLFC-ACC) circuit in sad affect and depression as well as the mood response to antidepressant treatment, including 10-Hz repetitive transcranial magnetic stimulation (rTMS) applied over the MDLFC. While the empirical support for a direct role of the MDLFC in affect is unclear, a wealth of research supports the ACC as an interface between action and emotion (Paus, 2001). In a series of experiments using behavioural, brain imaging and brain stimulation techniques we investigated the involvement of the ACC and an MDLFC-ACC (i.e., frontocingulate) circuit in an "action and emotion" relevant behaviour, namely, paralinguistic aspects of speech production. (e.g., speech pitch and loudness). In Experiment 1, we examined the relationship between affect and paralinguistic aspects of speech and in Experiment 2 we investigated the role of the ACC in mediating this phenomenon. Next, applying our knowledge of the role of the ACC in affect-relevant behaviour, we combined rTMS with a speech task (Experiment 3) and with PET (Experiment 4) in order investigate further the possibility that influencing brain activity in a frontocingulate circuit may contribute to the known mood effects of rTMS applied over the MDLFC. Taken together, our results demonstrated a role for the ACC in pitch variation during affective states and suggested that changes in affect and pitch variation following 10-Hz rTMS applied over the left MDLFC may involve changes in neural activity in a network of brain regions widely implicated in affect, including a frontocingulate circuit. The findings of this collection of studies take us a step further toward understanding the