Unconscious processing of facial affect in children and adolescents

In a previous study, with adults, we demonstrated that the amygdala and anterior cingulate gyrus are differentially responsive to happy and sad faces presented subliminally. Because the ability to perceive subtle facial signals communicating sadness is an important aspect of prosocial development, and is critical for empathic behavior, we examined this phenomenon from a developmental perspective using a backward masking paradigm. While undergoing functional magnetic resonance imaging (fMRI), 10 healthy adolescent children were presented with a series of happy and sad facial expressions, each lasting 20 ms and masked immediately by a neutral face to prevent conscious awareness of the affective expression. Relative to fixation baseline, masked sad faces activated the right amygdala, whereas masked happy faces failed to activate any of the regions of interest. Direct comparison between masked happy and sad faces revealed valence specific differences in the anterior cingulate gyrus. When the data were compared statistically to our previous sample of adults, the adolescent group showed significantly greater activity in the right amygdala relative to the adults during the masked sad condition. Groups also differed in several non-hypothesized regions. Development of unconscious perception from adolescence into adulthood appears to be accompanied by reduced activity within limbic affect processing systems, and perhaps increased involvement of other cortical and cerebellar systems.

Citicoline enhances frontal lobe bioenergetics as measured by phosphorus magnetic resonance spectroscopy

Citicoline supplementation has been used to ameliorate memory disturbances in older people and those with Alzheimer's disease. This study used MRS to characterize the effects of citicoline on high-energy phosphate metabolites and constituents of membrane synthesis in the frontal lobe. Phosphorus ((31)P) metabolite data were acquired using a three-dimensional chemical-shift imaging protocol at 4 T from 16 healthy men and women (mean +/- SD age 47.3 +/- 5.4 years) who orally self-administered 500 mg or 2000 mg Cognizin Citicoline (Kyowa Hakko Kogyo Co., Ltd, Ibaraki, Japan) for 6 weeks. Individual (31)P metabolites were quantified in the frontal lobe (anterior cingulate cortex) and a comparison region (parieto-occipital cortex). Significant increases in phosphocreatine (+7%), beta-nucleoside triphosphates (largely ATP in brain, +14%) and the ratio of phosphocreatine to inorganic phosphate (+32%), as well as significant changes in membrane phospholipids, were observed in the anterior cingulate cortex after 6 weeks of citicoline treatment. These treatment-related alterations in phosphorus metabolites were not only regionally specific, but tended to be of greater magnitude in subjects who received the lower dose. These data show that citicoline improves frontal lobe bioenergetics and alters phospholipid membrane turnover. Citicoline supplementation may therefore help to mitigate cognitive declines associated with aging by increasing energy reserves and utilization, as well as increasing the amount of essential phospholipid membrane components needed to synthesize and maintain cell membranes.

Relationship between white matter volume and cognitive performance during adolescence: effects of age, sex and risk for drug use

AIM

Familial drug abuse history has been shown to have an impact on cognitive development during adolescence. The present study examined the relationship between white matter volume and cognitive processing speed in adolescents with and without a familial substance abuse history.

PARTICIPANTS

The sample comprised 33 female and male adolescents stratified by risk (family history positive, FH+) and low-risk (FH-) groups.

MEASUREMENTS

Gray and white matter volumes were measured by segmenting magnetic resonance imaging (MRI) data. The neurocognitive test battery included tests that assessed processing speed, verbal ability and mental flexibility.

FINDINGS

Age-related differences in neuropsychological functioning were seen but did not differ by risk group status, although there was some evidence for an age x gender effect. Information processing speed (digit symbol and Stroop word color naming) was correlated significantly with white matter volume; however, this pattern was observed only in FH- females. Cognitive performance and tissue volumes did not differ significantly between risk groups.

CONCLUSIONS

Age-related differences in neuropsychological functioning were seen that might, in larger samples, prove to be related to risk for substance abuse in adolescents who have not yet initiated drug use.

Differences in regional blood volume during a 28-day period of abstinence in chronic cannabis smokers

Cerebral blood volume (CBV) studies have provided important insight into the effects of illicit substances such as cannabis. The present study examined changes in regional blood volume in the frontal and temporal lobe, and the cerebellum during 28 days of supervised abstinence from cannabis. Dynamic susceptibility contrast MRI (DSCMRI) data were collected on 15 current, long-term cannabis users between 6 and 36 h after the subjects' last reported cannabis use (Day 0), and again after 7 and 28 days of abstinence. Resting state CBV images were also acquired on 17 healthy comparison subjects. The present findings demonstrate that at Day 7, cannabis users continued to display increased blood volumes in the right frontal region, the left and right temporal regions, and the cerebellum. However, after 28 days of abstinence, only the left temporal area and cerebellum showed significantly increased CBV values in cannabis users. These findings suggest that while CBV levels begin to normalize with continued abstinence from cannabis, specifically in frontal areas, other temporal and cerebellar brain regions show slower CBV decreases.

Increased amygdala fMRI activation after secretin administration

It has recently been reported that secretin activates gene expression in the central nucleus of the amygdala in rats. To examine the neurophysiological effects of secretin on amygdalar activation in humans, the authors measured Blood Oxygen Level Dependent functional magnetic resonance imaging signal change during facial affect processing in a placebo-controlled double-blind study. The authors studied 12 healthy male subjects who were presented with three stimulus conditions: viewing happy, fearful, and neutral faces, before and after infusion with either secretin or placebo. To test whether treatment was associated with distinct patterns of activation, the two conditions (Pre and Post) were subjected to a subtraction analyses in SPM99 and hypotheses regarding the activation of the left and right amygdala were tested using a region-of-interest approach. Subtraction of treatment minus baseline activation during the fear condition yielded significant (p=.001) activation in the right amygdala and a nonsignificant increase in activation in the left amygdala. No significant differences were seen between the treatment conditions for the amygdala when viewing happy or neutral faces. These preliminary findings indicate that secretin may alter responsivity to affective stimuli. The presence of increased activation of the amygdala during the viewing of fearful faces is consistent with findings from animal studies and suggests a mechanism by which secretin may modulate social behavior.

Performance on the Stroop predicts treatment compliance in cocaine-dependent individuals

Treatment dropout is a problem of great prevalence and stands as an obstacle to recovery in cocaine-dependent (CD) individuals. Treatment attrition in CD individuals may result from impairments in cognitive control, which can be reliably measured by the Stroop color-word interference task. The present analyses contrasted baseline performance on the color-naming, word-reading, and interference subtests of the Stroop task in CD subjects who completed a cocaine treatment trial (completers: N=50) and those who dropped out of the trial before completion (non-completers: N=24). A logistic regression analysis was used to predict trial completion using three models with the following variables: the Stroop task subscale scores (Stroop model); the Hamilton depression rating scale (HDRS) scores (HDRS model); and both the Stroop task subscale scores and HDRS scores (Stroop and HDRS model). Each model was able to significantly predict group membership (completers vs non-completers) better than a model based on a simple constant (HDRS model p=0.02, Stroop model p=0.006, and Stroop and HDRS model p=0.003). Models using the Stroop preformed better than the HDRS model. These findings suggest that the Stroop task can be used to identify cocaine-dependent subjects at risk for treatment dropout. The Stroop task is a widely available, reliable, and valid instrument that can be easily employed to identify and tailor interventions of at risk individuals in the hope of improving treatment compliance.

Cannabis and motor function: fMRI changes following 28 days of discontinuation

The authors hypothesized that supplementary motor cortex (SMA) and anterior cingulate cortex (ACC) activation in chronic cannabis users, studied 4 to 36 hours after their last episode of use, would disappear by Day 28 of abstinence during finger-tapping tests. Eleven cannabis users and 16 comparison subjects were scanned during right (RFT) and left (LFT) finger-tapping tasks on a GE 1.5 Tesla scanner retrofitted with a whole body echo planar coil. Image analyses were conducted in SPM99 using an ROI approach to define each Brodmann area (BA). Differences in cerebral activation were examined in the left and right primary motor cortex (BA4), SMA (BA6), and ACC (BA24 and BA32 separately). The authors found diminished activation for contralateral BA6 from Day 0 to Day 28. For LFT, the authors also found: ipsilaterally diminished BA6 activation on Day 7, but not Day 0 or Day 28; ipsilaterally diminished BA32 activation on Day 0, but not Day 7 or Day 28; contralaterally diminished BA 4 activation on Day 28, but not Day 0 or Day 7; and contralaterally diminished BA32 activation on Day 0 and Day 28, but not Day 7. For RFT, the authors found ipsilaterally diminished BA32 activation on Days 0 and 7 but not on Day 28; contralaterally diminished BA32 activation on Days 0, 7, and 28; and ipsilaterally diminished BA6 activation on Days 0, 7, and 28. These results suggest that residual diminished brain activation is still observed after discontinuing cannabis use in motor cortical circuits.

Mood disorders

Despite the prevalence of the mood disorders, the underlying neuropathology is still poorly understood. This article describes abnormalities in brain activation that have been reported in neuroimaging studies of patients with depression and bipolar illness. Functional changes have been identified in regions important for neural networks underlying emotional processing, including frontal, subcortical, and limbic regions. The interpretation of neuroimaging studies in mood disorders is limited by potential confounding factors including medication effects, duration of illness, comorbidity, and gender.

Cerebellar gray matter volume correlates with duration of cocaine use in cocaine-dependent subjects

This study was conducted to explore differences in gray and white matter volume between cocaine-dependent and healthy comparison subjects using optimized voxel-based morphometry (VBM). Brain magnetic resonance imaging (MRI) and neuropsychological function tests were performed for 40 cocaine-dependent subjects (41.4+/-6.9 years, 27 men) and 41 healthy age- and sex-matched comparison subjects (38.7+/-8.8 years, 26 men). Optimally normalized whole brain MR images were segmented, modulated, smoothed, and compared between groups with statistical parametric mapping. The cocaine-dependent group had lower gray matter volumes in bilateral premotor cortex (Brodmann area (BA) 6, 8; 16.6%), right orbitofrontal cortex (BA 10, 15.1%), bilateral temporal cortex (BA 20, 38; 15.9%), left thalamus (12.6%), and bilateral cerebellum (13.4%) as well as lower right cerebellar white matter volume (10.0%) relative to the comparison group at a corrected p<0.05 for multiple comparisons. Duration of cocaine use negatively correlated with right and left cerebellar gray matter volumes (r=-0.37, r=-0.39, respectively). In cocaine-dependent subjects, lower cerebellar hemispheric gray and white matter volumes were correlated with deficits in executive function and decreased motor performance. This study reports that cocaine-dependent subjects have lower gray matter volumes in cerebellar hemispheres as well as in frontal, temporal cortex, and thalamus. These findings are the first to suggest that the cerebellum may be vulnerable to cocaine-associated brain volume changes, and that cerebellar deficits may contribute to neuropsychological deficits and motor dysfunction frequently observed in cocaine-dependent subjects.

Neuropsychological Consequences of Opiate Use

Approximately 3.7 million individuals have used heroin and other opiate substances in their lifetime. Despite increasing knowledge of the effects of heroin, it remains the most abused opiate and use among adults has recently increased. The empirical literature examining the neurocognitive effects of acute and chronic opioid use remains limited; however, findings to date suggest that the use of opiates has both acute and long-term effects on cognitive performance. Neuropsychological data indicate deficits in attention, concentration, recall, visuospatial skills and psychomotor speed with both acute and chronic opioid use. The long-term effects of opiate use appear to have the greatest impact on executive functions, including the ability to shift cognitive set and inhibit inappropriate response tendencies. Factors that contribute to addiction and recovery are also discussed, as it is difficult to disentangle the effects of opiate use on cognitive performance from other factors that may affect neurobehavioral measures.

White matter abnormalities observed in bipolar disorder: a diffusion tensor imaging study

OBJECTIVES

An increased incidence in white matter abnormalities is among the most frequently reported brain change in patients with bipolar disorder. The objective of the present study was to examine white matter tract integrity, using diffusion tensor imaging (DTI), in bipolar patients and healthy comparison subjects.

METHODS

Eleven DSM-IV bipolar I patients and 10 healthy age- and sex-matched controls were studied. DTI data were acquired on a 1.5 Tesla scanner. Fractional anisotropy (FA) and diffusivity (trace) were determined from axial images using region of interest (ROI) analyses. The ROIs were manually placed in the midline and forward projecting arms of the genu (anterior) and the midline of the splenium (posterior) of the corpus callosum.

RESULTS

Bipolar patients had significantly higher FA in the midline of the genu compared with healthy controls. Regional white matter differences were also observed, with significantly lower FA in the genu than forward projecting regions in both groups and lower FA in the genu than the splenium in controls.

CONCLUSIONS

Diffusion tensor imaging revealed significant microstructural differences in the genu, as measured by elevated FA in bipolar patients compared with healthy controls. These preliminary findings further support the hypothesis that anomalous frontal brain mechanisms may be associated with bipolar disorder.

Recognition of happy facial affect in panic disorder: an fMRI study

BACKGROUND

This study investigated activation of the anterior cingulate cortex (ACC) and amygdala during the presentation of happy facial affect images in patients with panic disorder (PD) as measured by blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI).

METHODS

Eight patients with PD and eight sex-matched controls were recruited for the study. Scanning was performed on a general electric (GE) Signa 1.5T scanner retrofitted with a whole body echo planar coil. Using a quadrature head coil, echo planar images and high-resolution MR images were acquired.

RESULTS

After covarying for age, examination of group differences revealed greater ACC activation bilaterally in patients with PD compared to controls in response to happy faces. However, there were no differences in amygdala activation between the groups. These findings contrasted with regional brain activation in response to neutral faces where there were was also greater bilateral ACC activation in the PD group, but only 44 ACC voxels showed significant increases as opposed to 509 voxels for the happy condition. There were no between group differences in activation in the amygdala.

CONCLUSION

This is the first fMRI study to our knowledge that demonstrates ACC abnormalities in response to happy facial affect recognition in PD.

Positive affect modulates activity in the visual cortex to images of high calorie foods

Activity within the visual cortex can be influenced by the emotional salience of a stimulus, but it is not clear whether such cortical activity is modulated by the affective status of the individual. This study used functional magnetic resonance imaging (fMRI) to examine the relationship between affect ratings on the Positive and Negative Affect Schedule and activity within the occipital cortex of 13 normal-weight women while viewing images of high calorie and low calorie foods. Regression analyses revealed that when participants viewed high calorie foods, Positive Affect correlated significantly with activity within the lingual gyrus and calcarine cortex, whereas Negative Affect was unrelated to visual cortex activity. In contrast, during presentations of low calorie foods, affect ratings, regardless of valence, were unrelated to occipital cortex activity. These findings suggest a mechanism whereby positive affective state may affect the early stages of sensory processing, possibly influencing subsequent perceptual experience of a stimulus.

Neural correlates of emotional intelligence in adolescent children

The somatic marker hypothesis posits a key role for the ventromedial prefrontal cortex, amygdala, and insula in the ability to utilize emotions to guide decision making and behavior. However, the relationship between activity in these brain regions and emotional intelligence (EQ) during adolescence, a time of particular importance for emotional and social development, has not been studied. Using functional magnetic resonance imaging (fMRI), we correlated scores from the Bar-On Emotional Quotient Inventory, Youth Version (EQ-i:YV) with brain activity during perception of fearful faces in 16 healthy children and adolescents. Consistent with the neural efficiency hypothesis, higher EQ correlated negatively with activity in the somatic marker circuitry and other paralimbic regions. Positive correlations were observed between EQ and activity in the cerebellum and visual association cortex. The findings suggest that the construct of self-reported EQ in adolescents is inversely related to the efficiency of neural processing within the somatic marker circuitry during emotional provocation.

Quantitative magnetic resonance brain imaging in US army veterans of the 1991 Gulf War potentially exposed to sarin and cyclosarin

BACKGROUND

In March 1991, a munitions storage complex at Khamisiyah, Iraq was destroyed, potentially exposing more than 100,000 US troops to low levels of the organophosphate nerve agents sarin and cyclosarin. Little is known about the neurophysiological effects of low-dose exposure to sarin/cyclosarin in humans, although some research has indicated subtle but persistent neurobehavioral and neurochemical changes in individuals exposed to sarin/cyclosarin at levels insufficient to produce obvious clinical symptoms. However, the neuroanatomical correlates of these changes are unclear. The current study examined the association between modeled estimates of sarin/cyclosarin exposure levels and volumetric measurements of gross neuroanatomical structures in 1991 Gulf War veterans with varying degrees of possible low-level sarin/cyclosarin exposure.

METHODS

Twenty-six GW-deployed veterans recruited from the Devens Cohort Study participated. Magnetic resonance images of the brain were acquired and analyzed using morphometric techniques, producing volumetric measurements of white matter, gray matter, right and left lateral ventricles, and cerebrospinal fluid. Volumetric data were analyzed using exposure estimates obtained from refined models of the 1991 Khamisiyah presumed exposure hazard area.

RESULTS

Binary comparisons of sarin/cyclosarin 'exposed' (N=13) and 'unexposed' (N=13) veterans revealed no differences in volumetric measurements of discrete brain tissues. However, linear trend analyses showed a significant association between higher levels of estimated sarin/cyclosarin exposure and both reduced white matter (adjusted parameter estimate=-4.64, p<0.0001) and increased right lateral ventricle (adjusted parameter estimate=.11, p=0.0288) and left lateral ventricle (adjusted parameter estimate=.13, p<0.0001) volumes.

CONCLUSIONS

These findings suggest subtle but persistent central nervous system pathology in Gulf War veterans potentially exposed to low levels of sarin/cyclosarin and argue for further investigation of the long-term effects of low-dose sarin/cyclosarin exposures in humans.

Reduced amygdala volumes in first-episode bipolar disorder and correlation with cerebral white matter

BACKGROUND

Previous magnetic resonance imaging (MRI) findings on amygdala volume abnormalities in bipolar disorder have been inconsistent, which may partly reflect clinical heterogeneity. It is unclear whether amygdala abnormalities are present early in the course of illness and/or are the consequence of disease progression.

METHODS

Twenty patients with first-episode bipolar disorder and 23 matched healthy comparison subjects were included. Magnetic resonance images were used to measure amygdala volumes, as well as whole brain measures of gray and white matter volume.

RESULTS

First-episode bipolar patients had significant reductions in amygdala volume relative to healthy subjects in an analysis of covariance that accounted for the effects of age, sex, and whole brain volume. First-episode patients also showed a trend reduction in cerebral white matter volume, and there was a significant correlation between cerebral white matter volume and total amygdala volume in patients but not control subjects.

CONCLUSIONS

These findings indicate that amygdala volume deficits are present early in the course of bipolar disorder and may occur within a neuroanatomical context of reduced cerebral white matter. Additional research should examine whether the nature of regional white matter deficits, particularly in frontal-temporal tracts, may help parse the pathophysiology of amygdala volume abnormalities in bipolar disorder.

Depressed mood and lateralized prefrontal activity during a Stroop task in adolescent children

Negative affective style and depressive disorders share a common pattern of brain activation asymmetry in adults, characterized by reduced left relative to right prefrontal activation. It is not clear whether a similar pattern of asymmetry is related to depressive mood state during the period of adolescence, an important stage of emotional and brain development. We correlated Beck Depression Inventory (BDI) scores from 16 adolescents with prefrontal, anterior cingulate, and amygdala activity during functional magnetic resonance imaging (FMRI) of the Stroop Interference task. Depressed mood correlated positively with activity in the left dorsolateral prefrontal cortex (DLPFC) and anterior cingulate gyrus, and negatively with activity in the right DLPFC. When interpreted from a compensatory recruitment perspective, findings suggest that affective lateralization in adolescents is consistent with that seen in adulthood.

Altered regional blood volume in chronic cannabis smokers

The quantitative measurement of cerebral perfusion is crucial for the study of both normal and impaired human brain function. Although cannabis is the most commonly abused illicit substance in the United States, its effects on cerebral blood volume (CBV) have not been fully examined. The objective of the present study was to examine differences in relative regional blood volume in focal regions of interest--including the frontal lobe, the temporal lobe, and the cerebellum--during a period of supervised abstinence from cannabis. Dynamic susceptibility contrast MRI data were collected on 12 current, long-term daily cannabis users between 6 and 36 hr after the subjects' last reported cannabis use. Resting-state CBV images were also acquired in 17 healthy comparison subjects. Data were acquired in the axial plane with a 1.5-Tesla GE Signa scanner following a bolus of gadolinium contrast agent. Cannabis users demonstrated significantly increased blood volumes in the right frontal area (p < .05), in the left temporal area (p < .005), and in the cerebellum (p < .005) relative to comparison subjects. Among the cannabis users, there were no significant correlations between regional blood volumes and either total lifetime episodes of smoking or urinary tetrahydrocannabinol concentrations. These findings have important implications for understanding the effects of chronic heavy cannabis use on brain function. It would be of interest to extend the investigation beyond 6-36 hr of abstinence from cannabis to determine whether increased CBV values persist for several weeks or eventually normalize.

Fear-related activity in the prefrontal cortex increases with age during adolescence: A preliminary fMRI study

An emerging theory of adolescent development suggests that brain maturation involves a progressive "frontalization" of function whereby the prefrontal cortex gradually assumes primary responsibility for many of the cognitive processes initially performed by more primitive subcortical and limbic structures. To test the hypothesis of developmental frontalization in emotional processing, we analyzed the correlation between age and prefrontal cortex activity in a sample of 16 healthy adolescents (nine boys; seven girls), ranging in age from 8 to 15 years, as they viewed images of fearful and happy faces while undergoing functional magnetic resonance imaging (fMRI). During fear perception, age was significantly positively correlated with greater functional activity within the prefrontal cortex, whereas no significant relationship was evident between age and activity in the amygdala. Consistent with previous gender-related findings, age was significantly correlated with bilateral prefrontal activity for the sample of females, but was only significantly related to right prefrontal activity for the males. In contrast, similar age-related correlations were not evident during the perception of happy faces. These results suggest that the maturation of threat-related emotional processing during adolescence is related to the progressive acquisition of greater functional activity within the prefrontal cortex. The hypothesis of age related decreases in amygdala activity was not supported, but may have been due to low signal-to-noise and inadequate power in the present sample to resolve subtle changes in this small structure.

fMRI of fearful facial affect recognition in panic disorder: the cingulate gyrus-amygdala connection

BACKGROUND

This study investigated cingulate cortex (CC) and amygdala response to fearful facial affect recognition in patients with panic disorder (PD) as measured by BOLD fMRI during the presentation of static facial images.

METHODS

Eight patients with PD and eight controls were studied. Scanning was performed on a GE Signa 1.5-T scanner. Echo planar and high-resolution MR images were acquired.

RESULTS

Controls produced greater CC activation compared to patients with PD in response to fearful faces. Furthermore, patients with PD produced less amygdala activation than controls in response to fearful faces. During the neutral face condition, overall activation for the CC was significantly greater in PD patients although anterior cingulate cortex (ACC) activation was not as markedly different between both groups. There were no between group differences in amygdala activation on exposure to the neutral face. Only left CC activation was significantly correlated negatively with HAM-A in PD patients in the fearful facial affect condition.

LIMITATIONS

Although comparable to similar studies, the sample size is small enough to warrant further investigation. Also, the effects of medication need to be considered when interpreting these results.

CONCLUSIONS

Patients with PD activate the ACC and amygdala significantly less than controls when asked to identify fearful facial affect during fMRI. The higher the anxiety, the lower the left CC activation. Thus, chronic hyperarousal in PD may diminish attentional resources and emotional response reflected in reduced ACC and amygdala activation. Even if these are medication effects, the differences from controls are clinically relevant.

Affect modulates appetite-related brain activity to images of food

OBJECTIVE

We examined whether affect ratings predicted regional cerebral responses to high and low-calorie foods.

METHOD

Thirteen normal-weight adult women viewed photographs of high and low-calorie foods while undergoing functional magnetic resonance imaging (fMRI). Regression analysis was used to predict regional activation from positive and negative affect scores.

RESULTS

Positive and negative affect had different effects on several important appetite-related regions depending on the calorie content of the food images. When viewing high-calorie foods, positive affect was associated with increased activity in satiety-related regions of the lateral orbitofrontal cortex, but when viewing low-calorie foods, positive affect was associated with increased activity in hunger-related regions including the medial orbitofrontal and insular cortex. The opposite pattern of activity was observed for negative affect.

CONCLUSION

These findings suggest a neurobiologic substrate that may be involved in the commonly reported increase in cravings for calorie-dense foods during heightened negative emotions.

Sex differences in the relationship between white matter microstructure and impulsivity in adolescents

Rapid maturational brain changes occur during adolescence--a time associated with risk-taking behaviors and improvements in cognition. The present study examined the relationship between white matter (WM) microstructure, impulsive behavior and response inhibition in female and male adolescents. Twenty-one healthy adolescents underwent diffusion tensor imaging using a 3.0-T magnetic resonance imaging system. Impulse control was assessed using the Bar-On Emotional Quotient Inventory, Youth Version. Response inhibition was assessed using the Stroop Color-Word Interference Test. Fractional anisotropy (FA), a measure of WM coherence, and trace, a measure of overall diffusivity, were determined from voxels manually placed in the midline and in the left and right forward-projecting arms of the genu and the splenium of the corpus callosum. Sex-specific differences were observed for the relationship between FA and impulsive behavior in the right anterior callosum for males and in the splenium for females. Males, compared to females, displayed significantly higher FA in the left WM region. Although trace was not associated with impulse control, trace in the genu (for females) and splenium (males and females) was associated with Stroop performance. Regional differences in trace also were evident, with lower values in the splenium observed than in all other regions. Although the latter significantly improved with age, no sex differences in impulse control or in Stroop performance were detected. The present findings provide supporting evidence for sex-related differences in the development of WM microstructure during adolescence. These data further suggest a neurobiological mechanism underlying some of the emotional and cognitive changes commonly observed in males versus females during the adolescent period.

Methadone maintenance improves cognitive performance after two months of treatment

Methadone maintenance (MM) has received little scientific attention regarding neurocognitive effects. The present study examined cognitive function in 17 opiate-dependent subjects at baseline and after 2 months of MM treatment. Subjects demonstrated significant improvements from baseline on measures of verbal learning and memory, visuospatial memory, and psychomotor speed and reduced frequency of drug use (Addiction Severity Index) relative to baseline, although the total percentage of urine samples positive for additional illicit substances was slightly increased. No effect of illicit drug use was observed when the sample was stratified by urine toxicology results, suggesting that improvements in cognition were not associated with additional illicit drug use. Results suggest that opiate-dependent subjects exhibit significant improvement in cognitive function after MM treatment. Future investigations are needed to confirm these findings.

Functional magnetic resonance imaging studies in bipolar disorder

Abnormalities in brain activation using functional magnetic resonance imaging (fMRI) during cognitive and emotional tasks have been identified in bipolar disorder patients, in frontal, subcortical and limbic regions. Several studies also indicate that mood state may be differentiated by lateralization of brain activation in fronto-limbic regions. The interpretation of fMRI studies in bipolar disorder is limited by the choice of regions of interest, medication effects, comorbidity, and task performance. These studies suggest that there is a complex alteration in regions important for neural networks underlying cognition and emotional processing in bipolar disorder. However, measuring changes in specific brain regions does not identify how these neural networks are affected. New analytical techniques of fMRI data are needed in order to resolve some of these issues and identify how changes in neural networks relate to cognitive and emotional processing in bipolar disorder.