Elevated striatal and decreased dorsolateral prefrontal cortical activity in response to emotional stimuli in euthymic bipolar disorder: no associations with psychotropic medication load

Abnormal amygdala-prefrontal effective connectivity to happy faces differentiates bipolar from major depression

BACKGROUND

Bipolar disorder is frequently misdiagnosed as major depressive disorder, delaying appropriate treatment and worsening outcome for many bipolar individuals. Emotion dysregulation is a core feature of bipolar disorder. Measures of dysfunction in neural systems supporting emotion regulation might therefore help discriminate bipolar from major depressive disorder.

METHODS

Thirty-one depressed individuals-15 bipolar depressed (BD) and 16 major depressed (MDD), DSM-IV diagnostic criteria, ages 18-55 years, matched for age, age of illness onset, illness duration, and depression severity-and 16 age- and gender-matched healthy control subjects performed two event-related paradigms: labeling the emotional intensity of happy and sad faces, respectively. We employed dynamic causal modeling to examine significant among-group alterations in effective connectivity (EC) between right- and left-sided neural regions supporting emotion regulation: amygdala and orbitomedial prefrontal cortex (OMPFC).

RESULTS

During classification of happy faces, we found profound and asymmetrical differences in EC between the OMPFC and amygdala. Left-sided differences involved top-down connections and discriminated between depressed and control subjects. Furthermore, greater medication load was associated with an amelioration of this abnormal top-down EC. Conversely, on the right side the abnormality was in bottom-up EC that was specific to bipolar disorder. These effects replicated when we considered only female subjects.

CONCLUSIONS

Abnormal, left-sided, top-down OMPFC-amygdala and right-sided, bottom-up, amygdala-OMPFC EC during happy labeling distinguish BD and MDD, suggesting different pathophysiological mechanisms associated with the two types of depression.

Bipolar disorder: emotional dysregulation and neuronal vulnerability

Bipolar disorder is clinically characterized by fluctuating affect, and neuropsychologically by impairment in executive functions. Such phenomena are consistent with the centrality of emotional dysregulation and impulsivity to bipolar disorder. They are also consistent with a key role for prefrontal-subcortical (striatal-thalamic) and associated limbic circuitry in its mediation. Furthermore, there is growing data on the cellular mechanisms contributing to neuronal vulnerability in this mediating circuitry.

Elevated left and reduced right orbitomedial prefrontal fractional anisotropy in adults with bipolar disorder revealed by tract-based spatial statistics

CONTEXT

Diffusion tensor imaging (DTI) studies in adults with bipolar disorder (BD) indicate altered white matter (WM) in the orbitomedial prefrontal cortex (OMPFC), potentially underlying abnormal prefrontal corticolimbic connectivity and mood dysregulation in BD.

OBJECTIVE

To use tract-based spatial statistics (TBSS) to examine WM skeleton (ie, the most compact whole-brain WM) in subjects with BD vs healthy control subjects.

DESIGN

Cross-sectional, case-control, whole-brain DTI using TBSS.

SETTING

University research institute.

PARTICIPANTS

Fifty-six individuals, 31 having a DSM-IV diagnosis of BD type I (mean age, 35.9 years [age range, 24-52 years]) and 25 controls (mean age, 29.5 years [age range, 19-52 years]).

MAIN OUTCOME MEASURES

Fractional anisotropy (FA) longitudinal and radial diffusivities in subjects with BD vs controls (covarying for age) and their relationships with clinical and demographic variables.

RESULTS

Subjects with BD vs controls had significantly greater FA (t > 3.0, P <or= .05 corrected) in the left uncinate fasciculus (reduced radial diffusivity distally and increased longitudinal diffusivity centrally), left optic radiation (increased longitudinal diffusivity), and right anterothalamic radiation (no significant diffusivity change). Subjects with BD vs controls had significantly reduced FA (t > 3.0, P <or= .05 corrected) in the right uncinate fasciculus (greater radial diffusivity). Among subjects with BD, significant negative correlations (P < .01) were found between age and FA in bilateral uncinate fasciculi and in the right anterothalamic radiation, as well as between medication load and FA in the left optic radiation. Decreased FA (P < .01) was observed in the left optic radiation and in the right anterothalamic radiation among subjects with BD taking vs those not taking mood stabilizers, as well as in the left optic radiation among depressed vs remitted subjects with BD. Subjects having BD with vs without lifetime alcohol or other drug abuse had significantly decreased FA in the left uncinate fasciculus.

CONCLUSIONS

To our knowledge, this is the first study to use TBSS to examine WM in subjects with BD. Subjects with BD vs controls showed greater WM FA in the left OMPFC that diminished with age and with alcohol or other drug abuse, as well as reduced WM FA in the right OMPFC. Mood stabilizers and depressed episode reduced WM FA in left-sided sensory visual processing regions among subjects with BD. Abnormal right vs left asymmetry in FA in OMPFC WM among subjects with BD, likely reflecting increased proportions of left-sided longitudinally aligned and right-sided obliquely aligned myelinated fibers, may represent a biologic mechanism for mood dysregulation in BD.

A neural model of voluntary and automatic emotion regulation: implications for understanding the pathophysiology and neurodevelopment of bipolar disorder

The ability to regulate emotions is an important part of adaptive functioning in society. Advances in cognitive and affective neuroscience and biological psychiatry have facilitated examination of neural systems that may be important for emotion regulation. In this critical review we first develop a neural model of emotion regulation that includes neural systems implicated in different voluntary and automatic emotion regulatory subprocesses. We then use this model as a theoretical framework to examine functional neural abnormalities in these neural systems that may predispose to the development of a major psychiatric disorder characterized by severe emotion dysregulation, bipolar disorder.

Neural activation during encoding of emotional faces in pediatric bipolar disorder

OBJECTIVE

Neurobiological understanding of bipolar disorder (BD) is limited by a paucity of functional magnetic resonance imaging (fMRI) research examining correlates of psychological processes. To begin to address these limitations, the current study tests the hypothesis that pediatric BD (PBD) subjects exhibit altered neural activation during encoding of emotional faces compared to typically developing controls.

METHODS

Pediatric BD subjects (n=23; mean age=14.2+/-3.1 years) and controls (n=22; mean age=14.7+/-2.3 years) were matched on age, gender, and IQ. In this event-related fMRI study, subjects were scanned while viewing emotional faces and given a surprise recognition memory test 30 min postscan. Our main outcome measure was between-group differences in neural activation during successful versus unsuccessful face encoding.

RESULTS

Pediatric BD youth exhibited reduced memory for emotional faces, relative to healthy comparisons, particularly on fearful faces. Event-related fMRI analyses controlling for this behavioral difference showed that PBD subjects, compared to controls, had increased neural activation in the striatum and anterior cingulate cortex when successfully encoding happy faces and in the orbitofrontal cortex when successfully encoding angry faces. There were no between-group differences in neural activation during fearful face encoding.

CONCLUSIONS

Our results extend what is known about memory and face emotion processing impairments in PBD subjects by showing increased fronto-striatal activation during encoding of emotional faces. Further work is required to determine the impact of mood state, medication, and comorbid illnesses on these findings.