Yang-Tae Kim

Impairments of facial emotion recognition and theory of mind in methamphetamine abusers.

Chronic use of methamphetamine is related to behavioral disturbances including depression, aggressive behavior, and social isolation. These alterations of social behavior may be attributable to impairments in social cognition. However, few studies have evaluated social cognition in methamphetamine (MA) abusers. Therefore, the aim of the present study was to investigate whether MA abusers exhibit social cognition deficits in terms of facial emotion recognition and theory of mind (ToM). We also assessed cognitive flexibility by using the Wisconsin Card Sorting Test (WCST) to evaluate the impact of this function on social cognition. Twenty-eight MA abusers and twenty-seven healthy subjects enrolled in this study. All participants performed the Facial Emotion Recognition Task and advanced ToM tasks such as the Eye Test and Hinting Task. The Korean Wechsler Adult Intelligence Scale-Revised and computerized versions of the WCST were also administrated. The performances of MA abusers on the Facial Emotion Recognition Task and Eyes Test were lower than those of healthy subjects. In the WCST, MA abusers completed significantly fewer categories and made more total and perseverative errors than healthy subjects did. In addition, impairments in cognitive flexibility are correlated with impairments in facial emotion recognition and ToM within MA abusers. These findings lend further support to the assertion that the capacity to identify emotions from facial expression and infer mental state of others is impaired in MA abusers. Therefore, treatment and rehabilitation for MA abusers must consider role of social cognition and include relearning social interactions and behaviors.

Dose-dependent frontal hypometabolism on FDG-PET in methamphetamine abusers

OBJECTIVE Although a lot of evidence from neuropsychological and neuroimaging studies supports the view that patients with substance dependence have abnormalities in the prefrontal cortex, functional deficits in the prefrontal cortex have not been fully investigated in methamphetamine (MA) dependent patients. This study was prepared to examine whether MA abusers have cerebral metabolic abnormalities and executive dysfunction. METHOD Twenty-four abstinent MA dependent patients and 21 age-matched control subjects underwent resting brain FDG-PET and completed computerized versions of the Wisconsin card sorting test (WCST). Resting brain PET images were obtained 30min after an intravenous injection of 370MBq of (18)F-FDG. Significant differences in glucose metabolism were estimated for every voxel using t-statistics on SPM2 implemented in Matlab. RESULTS Resting brain FDG-PET revealed significant hypometabolism in the left inferior frontal white matter (Talairach coordinates (x, y, z): -34, 7, 31) in MA dependent patients compared to the control subjects (corrected p=0.001, peak Z=5.37, voxel number 201). The nearest gray matter region was the left inferior frontal cortex (Brodmann area 9). There were negative correlations between the relative regional cerebral metabolism for glucose (rCMRglc) in the left inferior frontal white matter and the total cumulative dose of MA (r=-0.57, p<0.01). MA dependent patients completed significantly fewer categories (3.8+/-2.2) and made more perseveration errors (21.3+/-11.8) and total errors (43.5+/-19.5) on the WCST when compared to the control subjects (p<0.01). CONCLUSIONS These data suggest that MA dependent patients have dose-dependent frontal hypometabolism and frontal executive dysfunction.

Increased power spectral density in resting-state pain-related brain networks in fibromyalgia.

Summary Higher power spectral density in patients with fibromyalgia may implicate the enhanced resting‐state baseline neural activity in several brain regions associated with pain processing. ABSTRACT Fibromyalgia (FM), characterized by chronic widespread pain, is known to be associated with heightened responses to painful stimuli and atypical resting‐state functional connectivity among pain‐related regions of the brain. Previous studies of FM using resting‐state functional magnetic resonance imaging (rs‐fMRI) have focused on intrinsic functional connectivity, which maps the spatial distribution of temporal correlations among spontaneous low‐frequency fluctuation in functional MRI (fMRI) resting‐state data. In the current study, using rs‐fMRI data in the frequency domain, we investigated the possible alteration of power spectral density (PSD) of low‐frequency fluctuation in brain regions associated with central pain processing in patients with FM. rsfMRI data were obtained from 19 patients with FM and 20 age‐matched healthy female control subjects. For each subject, the PSDs for each brain region identified from functional connectivity maps were computed for the frequency band of 0.01 to 0.25 Hz. For each group, the average PSD was determined for each brain region and a 2‐sample t test was performed to determine the difference in power between the 2 groups. According to the results, patients with FM exhibited significantly increased frequency power in the primary somatosensory cortex (S1), supplementary motor area (SMA), dorsolateral prefrontal cortex, and amygdala. In patients with FM, the increase in PSD did not show an association with depression or anxiety. Therefore, our findings of atypical increased frequency power during the resting state in pain‐related brain regions may implicate the enhanced resting‐state baseline neural activity in several brain regions associated with pain processing in FM.

Working Memory Impairment in Fibromyalgia Patients Associated with Altered Frontoparietal Memory Network

Background Fibromyalgia (FM) is a disorder characterized by chronic widespread pain and frequently associated with other symptoms. Patients with FM commonly report cognitive complaints, including memory problem. The objective of this study was to investigate the differences in neural correlates of working memory between FM patients and healthy subjects, using functional magnetic resonance imaging (MRI). Methodology/Principal Findings Nineteen FM patients and 22 healthy subjects performed an n-back memory task during MRI scan. Functional MRI data were analyzed using within- and between-group analysis. Both activated and deactivated brain regions during n-back task were evaluated. In addition, to investigate the possible effect of depression and anxiety, group analysis was also performed with depression and anxiety level in terms of Beck depression inventory (BDI) and Beck anxiety inventory (BAI) as a covariate. Between-group analyses, after controlling for depression and anxiety level, revealed that within the working memory network, inferior parietal cortex was strongly associated with the mild (r = 0.309, P = 0.049) and moderate (r = 0.331, P = 0.034) pain ratings. In addition, between-group comparison revealed that within the working memory network, the left DLPFC, right VLPFC, and right inferior parietal cortex were associated with the rating of depression and anxiety? Conclusions/Significance Our results suggest that the working memory deficit found in FM patients may be attributable to differences in neural activation of the frontoparietal memory network and may result from both pain itself and depression and anxiety associated with pain.

Neural correlates of motor imagery for elite archers

Motor imagery is a mental rehearsal of simple or complex motor acts without overt body movement. It has been proposed that the association between performance and the mental rehearsal period that precedes the voluntary movement is an important point of difference between highly trained athletes and beginners. We compared the activation maps of elite archers and nonarchers during mental rehearsal of archery to test whether the neural correlates of elite archers were more focused and efficiently organised than those of nonarchers. Brain activation was measured using functional MRI in 18 right‐handed elite archers and 18 right‐handed nonarchers. During the active functional MRI imagery task, the participants were instructed to mentally rehearse their archery shooting from a first‐person perspective. The active imagery condition was tested against the nonmotor imagery task as a control condition. The results showed that the premotor and supplementary motor areas, and the inferior frontal region, basal ganglia and cerebellum, were active in nonarchers, whereas elite archers showed activation primarily in the supplementary motor areas. In particular, our result of higher cerebellar activity in nonarchers indicates the increased participation of the cerebellum in nonarchers when learning an unfamiliar archery task. Therefore, the difference in cerebellar activation between archers and nonarchers provides evidence of the expertise effect in the mental rehearsal of archery. In conclusion, the relative economy in the cortical processes of elite archers could contribute to greater consistency in performing the specific challenge in which they are highly practised. Copyright

Neural correlates related to action observation in expert archers

A growing body of evidence suggests that activity of the mirror neuron system is dependent on the observers motor experience of a given action. It remains unclear, however, whether activity of the mirror neuron system is also associated with the observers motor experience in sports game. Therefore, the aim of the present study is to investigate differences in activation of the mirror neuron system during action observation between experts and non-archer control subjects. We used video of Western-style archery in which participants were asked to watch the archery movements. Hyperactivation of the premotor and inferior parietal cortex in expert archers relative to non-archer control subjects suggests that the human mirror neuron system could contain and expand representations of the motor repertoire. The fact that dorsomedial prefrontal cortex was more active in expert archers than in non-archer control subjects indicates a spontaneous engagement of theory of mind in experts when watching video of Western-style archery. Compared with the non-archer control subjects, expert archers showed greater activation in the neural system in regions associated with episodic recall from familiar and meaningful information, including the cingulate cortex, retrosplenial cortex, and parahippocampal gyrus. The results demonstrate that expertise effects stimulate brain activity not only in the mirror neuron system but also in the neural networks related to theory of mind and episodic memory.

Alterations in cortical activity of male methamphetamine abusers performing an empathy task: fMRI study.

We investigate possible differences in neural correlates of empathy processing between abstinent methamphetamine (MA) abusers and healthy subjects using functional magnetic resonance imaging (fMRI).

Reduced corpus callosum white matter microstructural integrity revealed by diffusion tensor eigenvalues in abstinent methamphetamine addicts

The purpose of the current study was to determine whether abstinent methamphetamine (MA) abusers demonstrate differences in white matter (WM) integrity of the corpus callosum (CC) due to possible neurotoxic effects of long-term MA abuse, compared with control subjects. In addition to fractional anisotropy (FA), the eigenvalues of the diffusion ellipsoid were used to evaluate the microstructural source of abnormal change in abstinent MA abusers if there occurred a difference in white matter integrity of the CC between healthy controls and abstinent MA abusers. Results showed significantly reduced FA in the genu of the corpus callosum in MA-dependent subjects compared with controls. Furthermore, the eigenvalues offered a unique opportunity to assess the microstructural source of abnormal changes in the genu of the CC. The relationships between Wisconsin Card Sorting Test (WCST) performance and the values of tensor measures also suggest that altered myelination is a possible source of FA reduction observed in the genu of the CC in MA abusers.

The differences in neural network activity between methamphetamine abusers and healthy subjects performing an emotion-matching task: functional MRI study

Methamphetamine (MA) abusers commonly exhibit socially problematic behaviors, such as diminished empathy, decreased emotional regulation and interpersonal violence, which may be attributable to alterations in emotional experience. However, few studies have used functional MRI to examine directly the emotional experience of threatening or fearful non‐face images in MA abusers. In this study, we investigated possible differences in neural correlates of negative emotional experiences between abstinent MA abusers and healthy subjects using complex visual scenes depicting fear or threat derived from the International Affective Picture System. In within‐group analyses, healthy subjects and MA abusers activated a similarly distributed cortical network, prominently including the amygdala, fusiform gyrus, parahippocampal gyrus, ventrolateral prefrontal cortex and inferior frontal cortex. In between‐group analyses, however, MA abusers showed a reduced activation in the bilateral dorsolateral prefrontal cortex and insula, and increased activation in the fusiform gyrus, hippocampus, parahippocampal gyrus and posterior cingulate cortex, relative to healthy subjects. Hypoactivation of the insula in MA abusers relative to healthy subjects suggests that the ability to have an emotional response to threatening scenes and empathy for anothers pain could be compromised in MA abusers. Hyperactivity in the fusiform gyrus, parahippocampal gyrus and posterior cingulate cortex in MA abusers relative to healthy subjects indicates that threatening and fearful images from the International Affective Picture System may remind MA abusers of episodic memory related to similar experiences. Therefore, functional impairment of these neural networks in MA abusers may contribute to altered emotional experience in social interactions, which could lead to increased negative mood and stress in interpersonal communication. Copyright

Delayed transition from ambiguous to risky decision making in alcohol dependence during Iowa Gambling Task.

It has been demonstrated that alcohol-dependent patients exhibit decision-making deficits, particularly, hypersensitivity to reward and executive dysfunction. Yet, how the impaired motivational process and executive dysfunction in the patients affect decisions under ambiguity and risk with different degrees of uncertainty is little known. To investigate the neuropsychological origin of the impaired decision making under uncertainty in alcohol dependence, we administered the Iowa Gambling Task (IGT), Game of Dice Task (GDT) and Wisconsin Card Sorting Test (WCST) to 23 alcohol-dependent patients and 21 healthy subjects, and calculated the correlations between the task performances. We found that the patients showed poor performance in all three tasks compared with the healthy subjects. Moreover, correlations between performances on the GDT and the later trials of the IGT were delayed in alcohol-dependent patients when compared with healthy subjects. There is also a significant correlation between performances of earlier trials of the IGT and the WCST in the patients. These findings suggest that executive dysfunction in alcohol-dependent patients hampers appropriate estimation of probability distributions of possible alternatives, leading to a delayed transition from ambiguous to risky conditions in the Iowa Gambling Task.