The authors review existing structural and functional neuroimaging studies of patients with bipolar disorder and discuss how these investigations enhance our understanding of the neurophysiology of this illness. Findings from structural magnetic resonance imaging (MRI) studies suggest that some abnormalities, such as those in prefrontal cortical areas (SGPFC), striatum and amygdala exist early in the course of illness and, therefore, potentially, predate illness onset. In contrast, other abnormalities, such as those found in the cerebellar vermis, lateral ventricles and other prefrontal regions (eg, left inferior), appear to develop with repeated affective episodes, and may represent the effects of illness progression and associated factors. Magnetic resonance spectroscopy investigations have revealed abnormalities of membrane and second messenger metabolism, as well as bioenergetics, in striatum and prefrontal cortex. Functional imaging studies report activation differences between bipolar and healthy controls in these same anterior limibic regions. Together, these studies support a model of bipolar disorder that involves dysfunction within subcortical (striatalthalamic)-prefrontal networks and the associated limbic modulating regions (amygdala, midline cerebellum). These studies suggest that, in bipolar disorder, there may be diminished prefrontal modulation of subcortical and medial temporal structures within the anterior limbic network (eg, amygdala, anterior striatum and thalamus) that results in dysregulation of mood. Future prospective and longitudinal studies focusing on these specific relationships are necessary to clarify the functional neuroanatomy of bipolar disorder.

Objectives Functional neuroimaging methods have proliferated in recent years, such that functional magnetic resonance imaging, in particular, is now widely used to study bipolar disorder. However, discrepant findings are common. A workgroup was organized by the Department of Psychiatry, University of Cincinnati (Cincinnati, OH, USA) to develop a consensus functional neuroanatomic model of bipolar I disorder based upon the participants’ work as well as that of others. Methods Representatives from several leading bipolar disorder neuroimaging groups were organized to present an overview of their areas of expertise as well as focused reviews of existing data. The workgroup then developed a consensus model of the functional neuroanatomy of bipolar disorder based upon these data. Results Among the participants, a general consensus emerged that bipolar I disorder arises from abnormalities in the structure and function of key emotional control networks in the human brain. Namely, disruption in early development (e.g., white matter connectivity, prefrontal pruning) within brain networks that modulate emotional behavior leads to decreased connectivity among ventral prefrontal networks and limbic brain regions, especially amygdala. This developmental failure to establish healthy ventral prefrontal–limbic modulation underlies the onset of mania and ultimately, with progressive changes throughout these networks over time and with affective episodes, a bipolar course of illness. Conclusions This model provides a potential substrate to guide future investigations and areas needing additional focus are identified.

Lateral ventriculomegaly was greater in bipolar disorder patients who had had repeated manic episodes, but it does not appear to be secondary to small critical periventricular structures. A larger than normal striatum, which has been reported in previous studies, was observed in first-episode patients. These results support the importance of prospectively studying neuroanatomic changes in bipolar disorder.

BackgroundAlthough environmental lead exposure is associated with significant deficits in cognition, executive functions, social behaviors, and motor abilities, the neuroanatomical basis for these impairments remains poorly understood. In this study, we examined the relationship between childhood lead exposure and adult brain volume using magnetic resonance imaging (MRI). We also explored how volume changes correlate with historic neuropsychological assessments.Methods and FindingsVolumetric analyses of whole brain MRI data revealed significant decreases in brain volume associated with childhood blood lead concentrations. Using conservative, minimum contiguous cluster size and statistical criteria (700 voxels, unadjusted p < 0.001), approximately 1.2% of the total gray matter was significantly and inversely associated with mean childhood blood lead concentration. The most affected regions included frontal gray matter, specifically the anterior cingulate cortex (ACC). Areas of lead-associated gray matter volume loss were much larger and more significant in men than women. We found that fine motor factor scores positively correlated with gray matter volume in the cerebellar hemispheres; adding blood lead concentrations as a variable to the model attenuated this correlation.ConclusionsChildhood lead exposure is associated with region-specific reductions in adult gray matter volume. Affected regions include the portions of the prefrontal cortex and ACC responsible for executive functions, mood regulation, and decision-making. These neuroanatomical findings were more pronounced for males, suggesting that lead-related atrophic changes have a disparate impact across sexes. This analysis suggests that adverse cognitive and behavioral outcomes may be related to lead's effect on brain development producing persistent alterations in structure. Using a simple model, we found that blood lead concentration mediates brain volume and fine motor function.

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The symptoms of bipolar disorder suggest dysfunction of anterior limbic networks that modulate emotional behavior and that reciprocally interact with dorsal attentional systems. Bipolar patients maintain a constant vulnerability to mood episodes even during euthymia, when symptoms are minimal. Consequently, we predicted that, compared with healthy subjects, bipolar patients would exhibit abnormal activation of regions of the anterior limbic network with corresponding abnormal activation of other cortical areas involved in attentional processing. In all, 10 unmedicated euthymic bipolar patients and 10 group-matched healthy subjects were studied with fMRI while performing the Continuous Performance Task-Identical Pairs version (CPT-IP). fMRI scans were obtained on a 3.0 T Bruker system using an echo planar imaging (EPI) pulse sequence, while subjects performed the CPT-IP and a control condition to contrast group differences in regional brain activation. The euthymic bipolar and healthy subjects performed similarly on the CPT-IP, yet showed significantly different patterns of brain activation. Specifically, bipolar patients exhibited increased activation of limbic, paralimbic, and ventrolateral prefrontal areas, as well as visual associational cortices. Healthy subjects exhibited relatively increased activation in fusiform gyrus and medial prefrontal cortex. In conclusion, these differences suggest that bipolar patients exhibit overactivation of anterior limbic areas with corresponding abnormal activation in visual associational cortical areas, permitting successful performance of an attentional task. Since the differences occurred in euthymia, they may represent trait, rather than state, abnormalities of brain function in bipolar disorder.

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Dietary DHA intake and associated elevations in erythrocyte DHA composition are associated with alterations in functional activity in cortical attention networks during sustained attention in healthy boys. This trial was registered at clinicaltrials.gov as NCT00662142.