Jeehye Seo

Alteration of functional connectivity in tinnitus brain revealed by resting-state fMRI?: A pilot study

Abstract Objective: We report a case study on possible alterations in resting-state functional connectivity between the auditory network and non-auditory brain regions in tinnitus patients. Design: Independent component analyses were performed to evaluate coherent spontaneous activity in distributed brain networks. The resting-state functional connectivity scores between the right and left auditory networks were measured. Direct comparison of resting-state connectivity between tinnitus patients and controls was made using a two-sample t-test. Study sample: Four patients (three male, one female; mean age 45 ± 3.92 years) with chronic tinnitus lateralized to the left ear, and six age-matched controls (four male, two female; mean age 45 ± 2.76 years) participated in this case study. Results: The average resting-state functional connectivity (FC) score between the left and right auditory cortical regions was significantly lower in tinnitus patients than in controls (P < 0.05). Direct comparison between patients and controls showed that increased functional connectivity caused by tinnitus occurred predominantly in the left amygdala and in the dorsomedial prefrontal cortex. Conclusions: Our pilot study suggested that resting state functional magnetic resonance imaging (fMRI) could be useful to investigate possible alterations in resting-state neuronal activity between the auditory and non-auditory networks in tinnitus patients.

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.

Altered working memory process in the manganese-exposed brain.

Chronic manganese (Mn) exposure often leads to impairments in fine motor and cognitive functions, particularly memory. However, the neural correlates of Mn-induced alterations in memory remain unclear. In the present study, we performed functional MRI (fMRI) with 2-back memory tests to assess the neural correlates of Mn-induced memory impairment in response to subclinical dysfunction in the working memory networks in welders exposed to Mn for extended periods of time. Within-group and between-group analyses revealed that brain activity in working memory networks was increased in welders with chronic Mn exposure during the 2-back verbal working memory task compared to healthy control individuals. Therefore, our fMRI findings indicate that welders might require more neural resources in working memory networks to compensate for subtle deficits in working memory and altered working memory processes, even if they performed the tasks at the same level as healthy control individuals.

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.

Altered white matter microstructural integrity revealed by voxel-wise analysis of diffusion tensor imaging in welders with manganese exposure.

Chronic exposure to manganese (Mn), which can be an occupational hazard or can result from liver failure, is associated with adverse motor and cognitive outcomes. Evidence from previous neuroimaging and magnetic resonance spectroscopy studies suggested alteration of function in Mn-exposed brains. However, the effect of chronic exposure of the human brain to Mn on white matter (WM) structure has not yet been determined. In the present study, we used diffusion tensor imaging (DTI) to investigate whether welders exposed to Mn demonstrate differences in WM integrity, compared with control subjects. Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) were measured on a voxel-wise basis in 30 male welders with exposure to Mn and in 19 age- and gender-matched control subjects. Direct comparison between welders and controls using investigator-independent Statistical Parametric Mapping (SPM) voxel-wise analysis of DTI metrics revealed a reduction of FA in the corpus callosum (CC) and frontal WM in Mn-exposed welders. Further, marked increases in RD and negligible changes in AD suggested that the microstructural changes in the CC and frontal WM result from compromised radial directionality of fibers in these areas, caused primarily by demyelination. Correlation analysis with neurobehavioral performance also suggested that the microstructural abnormalities were associated with subtle motor and cognitive differences in welders.

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

Effect of repetitive transcranial magnetic stimulation in a patient with chronic crossed aphasia: fMRI study.

OBJECTIVE We report here the case of a 52-year-old Korean woman who was initially diagnosed with non-fluent/global crossed aphasia. METHODS AND RESULTS Initial computed tomography of the brain revealed a haematoma of approximately 40 ml in the right basal ganglia area and cavitation around the right lateral ventricle. Three years after onset the aphasia was resolved to a conduction aphasia and she had an ongoing left-sided gait disturbance. Follow-up anatomical magnetic resonance imaging found no recurrence of haemorrhage. Language functional magnetic resonance imaging was examined before and after repetitive transcranial magnetic stimulation treatment. A 90-mm round coil stimulator was used and the repetitive transcranial magnetic stimulation treatment location was P3 on the 10-20 International electrode placement system (1 Hz, 20 min per day for 10 days over a 2-week period). Functional magnetic resonance imaging results before repetitive transcranial magnetic stimulation treatment showed no significant activity in either the ipsilesional or contralesional hemispheres for noun generation and sentence completion paradigms (p < 0.001, cluster size 128). Compared with the pre-treatment phase, following repetitive transcranial magnetic stimulation treatment the data from functional magnetic resonance imaging revealed significant activations in the right inferior frontal lobe (Brocas area), posterior temporal gyrus (Wernickes area), and parietal lobe for both the noun generation and sentence completion tasks (p < 0.001, cluster size 128). CONCLUSION This functional magnetic resonance imaging case study is the first to suggest the use of repetitive transcranial magnetic stimulation for improving language outcome in a patient with crossed aphasia. In addition, we report the value of language functional magnetic resonance imaging before and after repetitive transcranial magnetic stimulation treatment for determining the effect of treatment and the underlying neurobiological mechanism of functional recovery following repetitive transcranial magnetic stimulation treatment.

Brain activation patterns of motor imagery reflect plastic changes associated with intensive shooting training

Evidence from previous studies has suggested that motor imagery and motor action engage overlapping brain systems. As a result of this observation that motor imagery can activate brain regions associated with actual motor movement, motor imagery is expected to enhance motor skill performance and become an underlying principle for physical training in sports and physical rehabilitation. However, few studies have examined the effects of physical training on motor imagery in beginners. Also, differences in neural networks related to motor imagery before and after training have seldom been studied. In the current study, using functional magnetic resonance imaging (fMRI), we investigated the question of whether motor imagery can reflect plastic changes of neural correlates associated with intensive training. In fact, motor imagery was used in this study as a tool to assess the brain areas involved in shooting and involved in learning of shooting. We discovered that use of motor imagery resulted in recruitment of widely distributed common cortical areas, which were suggested to play a role in generation and maintenance of mental images before and after 90 h of shooting training. In addition to these common areas, brain activation before and after 90 h of shooting practice showed regionally distinct patterns of activity change in subcortical motor areas. That is, basal ganglia showed increased activity after 90 h of shooting practice, suggesting the occurrence of plastic change in association with gains in performance and reinforcement learning. Therefore, our results suggest that, in order to reach a level of expertise, the brain would change through initial reinforcement of preexistent connections during the training period and then use more focused neural correlates through formation of new connections.