Dissociative Tendency, Anger Expression, and Frontal Activation During a Verbal Fluency Task

Dissociation in adolescence has been described as a part of severe psychopathology with a complex comorbidity or serious trauma including sexual abuse (e.g., Chu and Dill, 1990; Sar et al., 2006). In contrast, it is also possible for healthy subjects to experience nonpathological (nonclinical) dissociation including daydreams or defense from strong stressors (de Ruiter et al., 2006). It is important to clarify the etiology of dissociative experiences. For example, a lack of integration of consciousness, amnesia, derealization, or depersonalization, and some neural mechanisms underlying dissociation could be reasonably hypothesized as core features of dissociative disorders (DD). Particularly, self-reference related regions such as the medial prefrontal or ventral frontal area might be involved in identity diffusion or multiple identity disorder (Reinders et al., 2003). Actually, recent advances in neuroimaging technology enable us to explore the brain functioning of dissociation. Although it is ideal to examine a patient with DD who is experiencing dissociation in vivo, it is simultaneously intrusive to induce pathological dissociation using reminders or stressors. According to the spectrum of dissociative experiences, another option would be to examine nonclinical dissociation or dissociative tendencies in a typical setting. Dissociative experiences usually begin in childhood, and less than 8% of the DD diagnoses are made in adolescents between the ages of 12 and 19 (Kluft, 1984). Some of the experiences are not subjectively distressful; therefore, dissociation might be underestimated as a clinical phenomenon (Foote et al., 2006). Furthermore, recent campus mental health professionals in Japan have often indicated that a trend for defence mechanism is “to dissociate from repression” in young adults (e.g., Takaishi, 2000). Based on these assumptions, the present study focused on nonclinical dissociative tendencies and investigated frontal functioning during a cognitive task in healthy university students. Aggression or impulsivity is another important mental health topic in youth including attention-deficit hyperactivity disorder (ADHD) or childhood bipolar spectrum including temper dysregulation disorder. Impulsivity is related to the loss of response inhibition, particularly to the lack of frontal functioning (e.g., Chamberlain and Sakahian, 2007). A recent study concluded that slower cortical thinning in the prefrontal cortex during adolescence is characteristic of ADHD, providing neurobiological evidence for the