fMRI investigation of disinhibition in cognitively impaired patients with multiple sclerosis

Pathomechanisms of behavioral abnormalities in Huntington disease: an update

Huntington disease (HD), a devastating autosomal-dominant neurodegenerative disease caused by an expanded CAG trinucleotide repeat, is clinically characterized by a triad of symptoms including involuntary motions, behavior problems and cognitive deficits. Behavioral symptoms with anxiety, irritability, obsessive-compulsive behaviors, apathy and other neuropsychiatric symptoms, occurring in over 50% of HD patients are important features of this disease and contribute to impairment of quality of life, but their pathophysiology is poorly understood. Behavior problems, more frequent than depression, can be manifest before obvious motor symptoms and occur across all HD stages, usually correlated with duration of illness. While specific neuropathological data are missing, the relations between gene expression and behavior have been elucidated in transgenic models of HD. Disruption of interneuronal communications, with involvement of prefronto-striato-thalamic networks and hippocampal dysfunctions produce deficits in multiple behavioral domains. These changes that have been confirmed by multistructural neuroimaging studies are due to a causal cascade linking molecular pathologies (glutamate-mediated excitotoxicity, mitochondrial dysfunctions inducing multiple biochemical and structural alterations) and deficits in multiple behavioral domains. The disruption of large-scale connectivities may explain the variability of behavior profiles and is useful in understanding the biological backgrounds of functional decline in HD. Such findings offer new avenues for targeted treatments in terms of minimizing neurobehavioral impairment in HD.

Symptom Interconnectivity in Multiple Sclerosis: A Narrative Review of Potential Underlying Biological Disease Processes

Introduction

Fatigue, cognitive impairment, depression, and pain are highly prevalent symptoms in multiple sclerosis (MS). These often co-occur and may be explained by a common etiology. By reviewing existing literature, we aimed to identify potential underlying biological processes implicated in the interconnectivity between these symptoms.

Methods

A literature search was conducted to identify articles reporting research into the biological mechanisms responsible for the manifestation of fatigue, cognitive impairment, depression, and pain in MS. PubMed was used to search for articles published from July 2011 to July 2021. We reviewed and assessed findings from the literature to identify biological processes common to the symptoms of interest.

Results

Of 693 articles identified from the search, 252 were selected following screening of titles and abstracts and assessing reference lists of review articles. Four biological processes linked with two or more of the symptoms of interest were frequently identified from the literature: (1) direct neuroanatomical changes to brain regions linked with symptoms of interest (e.g., thalamic injury associated with cognitive impairment, fatigue, and depression), (2) pro-inflammatory cytokines associated with so-called ‘sickness behavior,’ including manifestation of fatigue, transient cognitive impairment, depression, and pain, (3) dysregulation of monoaminergic pathways leading to depressive symptoms and fatigue, and (4) hyperactivity of the hypothalamic–pituitary-adrenal (HPA) axis as a result of pro-inflammatory cytokines promoting the release of brain noradrenaline, serotonin, and tryptophan, which is associated with symptoms of depression and cognitive impairment.

Conclusion

The co-occurrence of fatigue, cognitive impairment, depression, and pain in MS appears to be associated with a common set of etiological factors, namely neuroanatomical changes, pro-inflammatory cytokines, dysregulation of monoaminergic pathways, and a hyperactive HPA axis. This association of symptoms and biological processes has important implications for disease management strategies and, eventually, could help find a common therapeutic pathway that will impact both inflammation and neuroprotection.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40120-022-00368-2.

Thalamic atrophy correlates with dysfunctional impulsivity in multiple sclerosis

BACKGROUND

Recent studies highlight the central role of thalamic atrophy in Multiple Sclerosis (MS) related disorders. Behavioural aspects of (MS) are rarely explored but their investigation is of high interest. Dickman's Impulsiveness Inventory (DII) allows distinguishing functional impulsivity (FI) which is the ability to react fast and properly when necessary, from dysfunctional impulsivity (DI) which is a behavioural symptom corresponding to the tendency to miss forethought before acting.

OBJECTIVE

This paper aims to explore whether MS patients show significantly high and pathological DI, and to evaluate the impulsivity frequency in the different forms of MS including at the early stage of the Clinically Isolated Syndrome. Furthermore, this study focused on the factors that may induce abnormal impulsivity, and the link between thalamic atrophy and dysfunctional impulsivity in patients with MS.

METHODS

95 patients with demyelinating diseases including 21 Clinically Isolated Syndrome (CIS), 30 Relapsing-Remitting MS (RRMS), 23 Secondary Progressive MS (SPMS) and 21 Primary Progressive MS (PPMS) were prospectively recruited, and covered by extensive cognitive evaluation including the BCCogSEP (French version of the Brief Repeatable Battery for Neurological disease), the CSCT (Computerized Speed Cognitive Test) for processing speed of information (PSI), the DII to measure FI and DI, the Fast BDI to evaluate depression, and the EMIF-SEP scale to study physical, cognitive and social fatigues. 3D T2-FLAIR and 3D T1-weighted MRI were analyzed using automatic segmentation tools to quantify the T2 lesion load and to measure the whole and regional brain atrophy.

RESULTS

7% showed a pathologically high DI. The level of DI tended to differ significantly depending on the MS phenotype. There was no significant difference between RRMS, SPMS and PPMS, but RRMS showed significantly higher DI than CIS patients. Cognitive fatigue (r:-0.27, p<.01), depression (r:-0.21, p=.04) but mainly PSI (r:.33, p<.001) showed a significant correlation with DI. Among the brain regions of interest, the strongest significant correlation with DI was with thalamic atrophy (r:.33, p<.001).

CONCLUSION

Some MS patients show a pathologically high DI, mainly RRMS compared to CIS. Previous study highlighted impulsive traits in MS patients only in relation with the presence of depression. The present study demonstrates that depression tends to correlate with DI, but that cognitive fatigue, and mainly slowing of PSI, which is the most early and severe cognitive impairment in MS, have a stronger impact on the rise of pathological impulsive behaviour. DI in MS is linked to frontal regions but even more strongly to thalamus atrophy. This is in line with the hypothesis of a disconnection syndrome in MS that causes cognitive impairment to trigger and could have the same impact on behaviour. Hence, impulsive behaviour should be evaluated and taken into account in the care of patients with MS.

Distinct neural substrates underlying target facilitation and distractor suppression: A combined voxel-based morphometry and resting-state functional connectivity study

Selective attention, the ability to filter relevant from a sea of sensory information, relies on the prioritization of goal-relevant information (target facilitation) and the suppression of goal-irrelevant information (distractor suppression). Although several lines of evidence have shown that target facilitation and distractor suppression were mediated by distinct mechanisms, the underlying neural substrates remain unclear. To address this question, we acquired structural and resting-state magnetic resonance imaging scans, as well as behavioral data from a modified Posner cueing task. Specifically, the location of a target (Target Cue, TC) and a distractor (Distractor Cue, DC) was either cued in advance to separately trigger target facilitation and distractor suppression, or no predictive information was provided, serving as a baseline. We combined voxel-based morphometry (VBM) and resting-state functional connectivity (rsFC) analyses to explore the neural correlates of behavioral benefits, yielding the following results. First, behavioral data showed faster responses to TC and DC conditions compared to baseline, the benefits of which were named TC-benefit and DC-benefit. Second, the VBM analysis revealed that the gray matter volume (GMV) in the superior frontal (SFG) and postcentral gyrus inversely correlated with individual TC-benefit, while the GMV in the superior parietal lobe, middle frontal gyrus, and angular gyrus inversely correlated with individual DC-benefit, indicating that target facilitation and distractor suppression was associated with the GMV of distinct and distributed regions in the frontoparietal cortex. Third, the rsFC analysis with the SFG as a seed region further found distinct patterns of rsFC for target facilitation and distractor suppression. Specifically, individual TC-benefit were positively correlated with distributed connections between the SFG and brain regions, mainly within the ventral attention and somato-motor network; but individual DC-benefit were positively correlated with centralized connections between the SFG and brain regions, mainly within the frontoparietal, dorsal attention and ventral attention network. Finally, a multiple linear regression analysis showed that the GMV and rsFC could jointly explain individual differences in TC- and DC-benefit. Taken together, these results provided neural evidence for different structural and functional substrates underlying target facilitation and distractor suppression.

Identify a shared neural circuit linking multiple neuropsychiatric symptoms with Alzheimer's pathology

Neuropsychiatric symptoms (NPS) are common in Alzheimer's disease (AD)-associated neurodegeneration. However, NPS lack a consistent relationship with AD pathology. It is unknown whether any common neural circuits can link these clinically disparate while mechanistically similar features with AD pathology. Here, we explored the neural circuits of NPS in AD-associated neurodegeneration using multivariate pattern analysis (MVPA) of resting-state functional MRI data. Data from 98 subjects (70 amnestic mild cognitive impairment and 28 AD subjects) were obtained. The top 10 regions differentiating symptom presence across NPS were identified, which were mostly the fronto-limbic regions (medial prefrontal cortex, caudate, etc.). These 10 regions' functional connectivity classified symptomatic subjects across individual NPS at 69.46-81.27%, and predicted multiple NPS (indexed by Neuropsychiatric Symptom Questionnaire-Inventory) and AD pathology (indexed by baseline and change of beta-amyloid/pTau ratio) all above 70%. Our findings suggest a fronto-limbic dominated neural circuit that links multiple NPS and AD pathology. With further examination of the structural and pathological changes within the circuit, the circuit may shed light on linking behavioral disturbances with AD-associated neurodegeneration.

The Role of fMRI in the Assessment of Neuroplasticity in MS: A Systematic Review

Neuroplasticity, which is the ability of the brain to adapt to internal and external environmental changes, physiologically occurs during growth and in response to damage. The brain's response to damage is of particular interest in multiple sclerosis, a chronic disease characterized by inflammatory and neurodegenerative damage to the central nervous system. Functional MRI (fMRI) is a tool that allows functional changes related to the disease and to its evolution to be studied in vivo. Several studies have shown that abnormal brain recruitment during the execution of a task starts in the early phases of multiple sclerosis. The increased functional activation during a specific task observed has been interpreted mainly as a mechanism of adaptive plasticity designed to contrast the increase in tissue damage. More recent fMRI studies, which have focused on the activity of brain regions at rest, have yielded nonunivocal results, suggesting that changes in functional brain connections represent mechanisms of either adaptive or maladaptive plasticity. The few longitudinal studies available to date on disease evolution have also yielded discrepant results that are likely to depend on the clinical features considered and the length of the follow-up. Lastly, fMRI has been used in interventional studies to investigate plastic changes induced by pharmacological therapy or rehabilitation, though whether such changes represent a surrogate of neuroplasticity remains unclear. The aim of this paper is to systematically review the existing literature in order to provide an overall description of both the neuroplastic process itself and the evolution in the use of fMRI techniques as a means of assessing neuroplasticity. The quantitative and qualitative approach adopted here ensures an objective analysis of published, peer-reviewed research and yields an overview of up-to-date knowledge.

Characterization of inhibitory failure in Multiple Sclerosis: Evidence of impaired conflict resolution

INTRODUCTION

Inhibitory control deficits are frequently reported in Multiple Sclerosis (MS), although it is unclear whether these deficits represent a global or process-specific failure. Notably, most models of inhibitory control recognize at least two dissociable processes, the most consistent being: (a) the inhibition of a dominant response: response suppression, and (b) the inhibition of a dominant response and initiation of a nondominant response: executive control. This study aimed to ascertain the processes underlying inhibitory failure in MS.

METHOD

Twenty-three MS patients and 25 healthy controls completed a battery of commonly used inhibitory tasks, with measures from each task entered into a principal components analysis with orthogonal (varimax) rotation.

RESULTS

As anticipated, two components emerged, with tasks evaluating response suppression (stop signal, go/no go) loading on a common component, and tasks evaluating executive control (Stroop, antisaccade, endogenously-cued saccade) loading on a separate common component. Composite scores were generated for each component and compared between groups. Unlike response suppression scores, executive control scores were significantly poorer for MS patients.

CONCLUSIONS

Inhibitory control deficits in MS may reflect poor resolution in the context of competing processes, rather than difficulty in preventing the execution of an inappropriate response.

Neural Correlates of Outcome Anticipation in Multiple Sclerosis

Outcome anticipation is not only a mental preparation for upcoming consequences, but also an essential component of learning and decision-making. Thus, anticipation of consequences is a key process in everyday functioning. The striatum and the ventromedial prefrontal cortex are among the key regions that have been shown to be involved in outcome anticipation. However, while structural abnormalities of these regions as well as altered decision-making have been noted in individuals with multiple sclerosis (MS), neural correlates of outcome anticipation have not been explored in this population. Thus, we examined the neural correlates of outcome anticipation in MS by analyzing brain activation in individuals with MS while they performed a modified version of a card-guessing task. Seventeen MS and 13 healthy controls performed the task while functional magnetic resonance imaging (fMRI) was obtained. To achieve maximal anticipatory response and prevent the possibility of differential performance on the task, participants were presented with monetary rewards only on 50% of the trials. While replicating previous evidence of structural abnormalities of the striatum in MS, our results further showed that individuals with MS exhibited greater activation in the putamen, right hippocampus, and posterior cingulate cortex during outcome anticipation compared to healthy controls. Furthermore, even though there was no strategy that participants could learn in order to predict outcomes, 76% of participants with MS indicated that they used strategies while performing the task. We thus propose that the increased neural activation observed in MS during outcome anticipation might be explained by a failure in recognizing the lack of regularity in the task structure that could result in using strategies to perform the task.

Cerebellar Control on Prefrontal-Motor Connectivity During Movement Inhibition

Converging evidence suggests a crucial role of right inferior frontal gyrus (r-IFG) and right pre-supplementary motor area (r-preSMA) in movement inhibition control. The present work was aimed to investigate how the effective connectivity between these prefrontal areas and the primary motor cortex could change depending on the activity of the cerebellar cortex. Paired transcranial magnetic stimulation (TMS) was delivered in healthy subjects over the r-IFG/left primary motor area (l-M1) and over r-preSMA/l-M1 before (100 ms after the fixation cross onset) and 50, 75, 100, 125, and 150 ms after the presentation of a Go/NoGo visual cue establishing the specific time course and the causal interactions of these regions in relation to l-M1 as measured by motor evoked potentials (MEPs). The same paired-pulse protocol was applied following sham or real cerebellar continuous theta burst stimulation (cTBS). Following sham cTBS, for NoGo trials only, MEPs collected showed the expected pattern of activation for both r-IFG-l-M1 and r-preSMA-l-M1 connectivity, characterized by peaks of increased and decreased MEP amplitude regularly repeated every 50 ms. Following cerebellar cTBS, this pattern of activation related to NoGo trials was modified selectively for the r-IFG-M1 but not for r-preSMA-M1 connection. A common monitoring action of r-IFG and r-preSMA in inhibitory control was confirmed. The effects of cerebellar cTBS showed a specific interaction between cerebellum and r-IFG activity during the inhibitory process.

Effects of cerebellar transcranial alternating current stimulation on motor cortex excitability and motor function

The cerebellum regulates several motor functions through two main mechanisms, the cerebellum-brain inhibition (CBI) and the motor surround inhibition (MSI). Although the exact cerebellar structures and functions involved in such processes are partially known, Purkinje cells (PC) and their surrounding interneuronal networks may play a pivotal role concerning CBI and MSI. Cerebellar transcranial alternating current stimulation (tACS) has been proven to shape specific cerebellar components in a feasible, safe, effective, and non-invasive manner. The aim of our study was to characterize the cerebellar structures and functions subtending CBI and MSI using a tACS approach. Fifteen healthy individuals underwent a cerebellar tACS protocol at 10, 50, and 300 Hz, or a sham-tACS over the right cerebellar hemisphere. We measured the tACS aftereffects on motor-evoked potential (MEP) amplitude, CBI induced by tACS (tiCBI) at different frequencies, MSI, and hand motor task performance. None of the participants had any side effect related to tACS. After 50-Hz tACS, we observed a clear tiCBI-50Hz weakening (about +30%, p < 0.001) paralleled by a MEP amplitude increase (about +30%, p = 0.001) and a reduction of the time required to complete some motor task (about -20%, p = 0.01), lasting up to 30 min. The 300-Hz tACS induced a selective, specific tiCBI-300Hz and tiCBI-50Hz modulation in surrounding muscles (about -15%, p = 0.01) and MSI potentiation (about +40%, p < 0.001). The 10-Hz tACS and the sham-tACS were ineffective (p > 0.6). Our preliminary data suggest that PC may represent the last mediator of tiCBI and that the surrounding interneuronal network may have an important role in updating MSI, tiCBI, and M1 excitability during tonic muscle contraction, by acting onto the PC. The knowledge of these neurophysiological issues offers new cues to design innovative, non-invasive neuromodulation protocols to shape cerebellar-cerebral functions.

Abnormalities of the executive control network in multiple sclerosis phenotypes: An fMRI effective connectivity study

The Stroop interference task is a cognitively demanding task of executive control, a cognitive ability that is often impaired in patients with multiple sclerosis (MS). The aim of this study was to compare effective connectivity patterns within a network of brain regions involved in the Stroop task performance between MS patients with three disease clinical phenotypes [relapsing-remitting (RRMS), benign (BMS), and secondary progressive (SPMS)] and healthy subjects. Effective connectivity analysis was performed on Stroop task data using a novel method based on causal Bayes networks. Compared with controls, MS phenotypes were slower at performing the task and had reduced performance accuracy during incongruent trials that required increased cognitive control. MS phenotypes also exhibited connectivity abnormalities reflected as weaker shared connections, presence of extra connections (i.e., connections absent in the HC connectivity pattern), connection reversal, and loss. In SPMS and the BMS groups but not in the RRMS group, extra connections were associated with deficits in the Stroop task performance. In the BMS group, the response time associated with correct responses during the congruent condition showed a positive correlation with the left posterior parietal → dorsal anterior cingulate connection. In the SPMS group, performance accuracy during the congruent condition showed a negative correlation with the right insula → left insula connection. No associations between extra connections and behavioral performance measures were observed in the RRMS group. These results suggest that, depending on the phenotype, patients with MS use different strategies when cognitive control demands are high and rely on different network connections. Hum Brain Mapp, 37:2293-2304, 2016. © 2016 Wiley Periodicals, Inc.

Cerebellar activity in young people with familial risk for psychosis--The Oulu Brain and Mind Study

OBJECTIVE

The cerebellum plays a critical role in cognition and behavior. Altered function of the cerebellum has been related to schizophrenia and psychosis but it is not known how this applies to spontaneous resting state activity in young people with familial risk for psychosis.

METHODS

We conducted resting-state functional MRI (R-fMRI) in 72 (29 male) young adults with a history of psychosis in one or both parents (FR) but without their own psychosis, and 72 (29 male) similarly healthy control subjects without parental psychosis. Both groups in the Oulu Brain and Mind Study were drawn from the Northern Finland Birth Cohort 1986. Participants were 20-25 years old. Parental psychosis was established using the Care Register for Health Care. R-fMRI data pre-processing was conducted using independent component analysis with 30 and 70 components. A dual regression technique was used to detect between-group differences in the cerebellum with p<0.05 threshold corrected for multiple comparisons.

RESULTS

FR participants demonstrated statistically significantly increased activity compared to control subjects in the anterior lobe of the right cerebellum in the analysis with 70 components. The volume of the increased activity was 73 mm(3). There was no difference between the groups in the analysis with 30 components.

CONCLUSION

The finding suggests that increased activity of the anterior lobe of the right cerebellum may be associated with increased vulnerability to psychosis. The finding is novel, and needs replication to be confirmed.

Cannabis-induced alterations in brain activation during a test of information processing speed in patients with MS

Objective

The objective of this article is to determine the functional brain correlates of information processing speed in multiple sclerosis (MS) patients who smoke cannabis and those who are drug naïve.

Methods

Two neurologically and demographically matched samples of MS patients were enrolled, those who smoked cannabis daily (n = 20) and those who were cannabis naïve (n = 19). All participants completed the Brief Repeatable Battery of Neuropsychological Tests and underwent fMRI testing during which they were administered a modified version of the Symbol Digit Modalities Test (mSDMT).

Results

The cannabis group responded slower in nine of 11 blocks of the mSDMT (p < 0.001), showing a trend toward a slower response time (p < 0.08), but did not differ in the accuracy of response (p < 0.18). Both groups displayed activation in a prefrontal cortex-parietal network associated with information processing speed. When compared to the cannabis-naïve group, cannabis users showed less activation in the right (p = 0.009) and left (p = 0.001) thalami and increased activation in the anterior cingulate (p = 0.006).

Conclusion

Regular cannabis use in MS patients is associated with slower information processing speed and a pattern of cerebral activity that differs from cannabis-naïve individuals, most notably in a bilateral reduction of thalamic activity.

The grey matter correlates of impaired decision-making in multiple sclerosis

OBJECTIVE

People with multiple sclerosis (MS) have difficulties with decision-making but it is unclear if this is due to changes in impulsivity, risk taking, deliberation or risk adjustment, and how this relates to brain pathology.

METHODS

We assessed these aspects of decision-making in 105 people with MS and 43 healthy controls. We used a novel diffusion MRI method, diffusion orientational complexity (DOC), as an index of grey matter pathology in regions associated with decision-making and also measured grey matter tissue volumes and white matter lesion volumes.

RESULTS

People with MS showed less adjustment to risk and slower decision-making than controls. Moreover, impaired decision-making correlated with reduced executive function, memory and processing speed. Decision-making impairments were most prevalent in people with secondary progressive MS. They were seen in patients with cognitive impairment and those without cognitive impairment. On diffusion MRI, people with MS showed DOC changes in all regions except the occipital cortex, relative to controls. Risk adjustment correlated with DOC in the hippocampi and deliberation time with DOC in the medial prefrontal, middle frontal gyrus, anterior cingulate and caudate parcellations and with white matter lesion volumes.

CONCLUSIONS

These data clarify the features of decision-making deficits in MS, and provide the first evidence that they relate to grey and white matter abnormalities seen using MRI.

Meaningful Change in Cognition in Multiple Sclerosis: Method Matters

Objective:

To determine if different methods of evaluating cognitive change over time yield measurably different outcomes.

Methods:

Twelve cognitively impaired patients with clinically definite Multiple sclerosis (10 relapsing-remitting, 2 secondary progressive) underwent neuropsychological testing (baseline, 6, 12 months). Data was analysed using: t-tests evaluating group differences on individual tests, group differences in composite scores, reliable change analyses at the level of the individual, and comparisons regarding number of tests failed at each time point.

Results:

Group t-tests on individual tests yielded no change. When tests were grouped according to theoretical constructs, analyses revealed change in processing speed. Reliable change estimates revealed that 16% of the sample deteriorated. When change was measured with respect to the number of domains affected at each time point, 58% of the sample deteriorated on at least one subtest.

Conclusions:

Methodology has a significant impact on interpretation of longitudinal data. In the same group of subjects, traditional group analyses documented no change in individual test scores or change on a single composite score. Analyses of individual results documented change from 16 to 58% of the sample. Advantages and disadvantages of each method were discussed. Findings have implications for interpretation of longitudinal studies.

Cortical thickness at the time of the initial attack in two patients with paediatric relapsing-remitting multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is a chronic demyelinating disease of the central nervous system with a low incidence in the paediatric population; cortical atrophy is often striking, even in the early stages of the disease. Evidence of cortical thinning in childhood MS is scant.

AIMS

This study aimed to assess cortical thickness in paediatric patients during the initial attack of remitting-relapsing MS.

METHODS

We report two cases of remitting-relapsing MS, with initial attacks at 12 and 16 years of age. We analysed brain cortical thickness (CTh) in these patients and compared these data to the CTh of a control group comprised of six 12-year-old females and six 16-year-old males.

RESULTS

Both cases exhibited a total brain CTh significantly below that of the control group. This difference was also observed when analysing the CTh of all lobes except the left parietal lobe in one of the cases.

CONCLUSIONS

Cortical atrophy is already present at the time of onset of MS. Studies with larger patient populations that have a more homogenous clinical presentation could identify the time of onset of cortical atrophy and use this parameter as a prognostic and/or treatment marker of MS.

Brain activity changes in cognitive networks in relapsing-remitting multiple sclerosis - insights from a longitudinal FMRI study

Background

Extrapolations from previous cross-sectional fMRI studies suggest cerebral functional changes with progression of Multiple Sclerosis (MS), but longitudinal studies are scarce. We assessed brain activation changes over time in MS patients using a cognitive fMRI paradigm and examined correlations with clinical and cognitive status and brain morphology.

Methods

13 MS patients and 15 healthy controls (HC) underwent MRI including fMRI (go/no-go task), neurological and neuropsychological exams at baseline (BL) and follow-up (FU; minimum 12, median 20 months). We assessed estimates of and changes in fMRI activation, total brain and subcortical grey matter volumes, cortical thickness, and T2-lesion load. Bland-Altman (BA) plots served to assess fMRI signal variability.

Results

Cognitive and disability levels remained largely stable in the patients. With the fMRI task, both at BL and FU, patients compared to HC showed increased activation in the insular cortex, precuneus, cerebellum, posterior cingulate cortex, and occipital cortex. At BL, patients vs. HC also had lower caudate nucleus, thalamus and putamen volumes. Over time, patients (but not HC) demonstrated fMRI activity increments in the left inferior parietal lobule. These correlated with worse single-digit-modality test (SDMT) performance. BA-plots attested to reproducibility of the fMRI task. In the patients, the right caudate nucleus decreased in volume which again correlated with worsening SDMT performance.

Conclusions

Given preserved cognitive performance, the increased activation at BL in the patients may be viewed as largely adaptive. In contrast, the negative correlation with SDMT performance suggests increasing parietal activation over time to be maladaptive. Several areas with purported relevance for cognition showed decreased volumes at BL and right caudate nucleus volume decline correlated with decreasing SDMT performance. This highlights the dynamics of functional changes and the strategic importance of specific brain areas for cognitive processes in MS.

Spontaneous neuronal activity predicts intersubject variations in executive control of attention

Executive control of attention regulates our thoughts, emotion and behavior. Individual differences in executive control are associated with task-related differences in brain activity. But it is unknown whether attentional differences depend on endogenous (resting state) brain activity and to what extent regional fluctuations and functional connectivity contribute to individual variations in executive control processing. Here, we explored the potential contribution of intrinsic brain activity to executive control by using resting-state functional magnetic resonance imaging (fMRI). Using the amplitude of low-frequency fluctuations (ALFF) as an index of spontaneous brain activity, we found that ALFF in the right precuneus (PCUN) and the medial part of left superior frontal gyrus (msFC) was significantly correlated with the efficiency of executive control processing. Crucially, the strengths of functional connectivity between the right PCUN/left msFC and distributed brain regions, including the left fusiform gyrus, right inferior frontal gyrus, left superior frontal gyrus and right precentral gyrus, were correlated with individual differences in executive performance. Together, the ALFF and functional connectivity accounted for 67% of the variability in behavioral performance. Moreover, the strength of functional connectivity between specific regions could predict more individual variability in executive control performance than regionally specific fluctuations. In conclusion, our findings suggest that spontaneous brain activity may reflect or underpin executive control of attention. It will provide new insights into the origins of inter-individual variability in human executive control processing.

Symptomatic treatment and management of multiple sclerosis

The range of symptoms which occur in multiple sclerosis (MS) can have disabling functional consequences for patients and lead to significant reductions in their quality of life. MS symptoms can also interact with each other, making their management challenging. Clinical trials aimed at identifying symptomatic therapies have generally been poorly designed and have tended to be underpowered. Therefore, the evidence base for the management of MS symptoms with pharmacologic therapies is not strong and tends to rely upon open-label studies, case reports, and clinical trials with small numbers of patients and poorly validated clinical outcome measures. Recently, there has been a growing interest in the management of MS symptoms with pharmacologic treatments, and better-designed, randomized, double-blind, controlled trials have been reported. This chapter will describe the evidence base predominantly behind the various pharmacologic approaches to the management of MS symptoms, which in most, if not all, cases, requires multidisciplinary input. Drugs routinely recommended for individual symptoms and new therapies, which are currently in the development pipeline, will be reviewed. More interventional therapies related to symptoms that are refractory to pharmacotherapy will also be discussed, where relevant.

The relationship between executive functioning, processing speed, and white matter integrity in multiple sclerosis

The primary purpose of the current study was to examine the relationship between performance on executive tasks and white matter integrity, assessed by diffusion tensor imaging (DTI) in multiple sclerosis (MS). A second aim was to examine how processing speed affects the relationship between executive functioning and fractional anisotropy (FA). This relationship was examined in two executive tasks that rely heavily on processing speed: the Color-Word Interference Test and the Trail Making Test (Delis-Kaplan Executive Function System). It was hypothesized that reduced FA is related to poor performance on executive tasks in MS, but that this relationship would be affected by the statistical correction of processing speed from the executive tasks. A total of 15 healthy controls and 25 persons with MS participated. Regression analyses were used to examine the relationship between executive functioning and FA, both before and after processing speed was removed from the executive scores. Before processing speed was removed from the executive scores, reduced FA was associated with poor performance on the Color-Word Interference Test and Trail Making Test in a diffuse network including corpus callosum and superior longitudinal fasciculus. However, once processing speed was removed, the relationship between executive functions and FA was no longer significant on the Trail Making Test, and significantly reduced and more localized on the Color-Word Interference Test.

Differential cerebellar functional interactions during an interference task across multiple sclerosis phenotypes

PURPOSE

To determine whether modification of the connections between cerebellar and prefrontal areas might vary among multiple sclerosis (MS) phenotypes and might be associated with cognitive failure.

MATERIALS AND METHODS

Approval of the institutional review boards and written informed consent were obtained from each participant. Stroop-related functional magnetic resonance (MR) imaging activations and effective connectivity abnormalities between the right cerebellum and any other brain regions were assessed by using a psychophysiologic interaction (PPI) analysis from 17 patients with relapsing-remitting (RR), 17 with benign, and 23 with secondary progressive (SP) MS and 18 healthy control subjects (P < .05, corrected at cluster level). Correlations with disease duration, T2 lesion volume, brain volume, and response times (RTs) during the incongruent condition were estimated (P < .001, uncorrected).

RESULTS

Activation and PPI analyses showed that, compared with the other groups, RR MS group had abnormal recruitment of regions of the left frontoparietal lobes, whereas compared with RR MS group, SP MS group had abnormal recruitment of the cingulum or precuneus. Benign MS group had increased activation of the right prefrontal cortex, and increased interaction between these regions and the right cerebellum. In healthy controls, RTs inversely correlated with activity of right cerebellum and several frontoparietal regions. In MS, RTs inversely correlated with bilateral cerebellar activity and directly correlated with right precuneus activity. In MS, disease duration inversely correlated with right cerebellar activity and directly correlated with left inferior frontal gyrus and right precuneus activity. Higher T2 lesion volume and lower brain volumes were related to activity in these areas.

CONCLUSION

Patients with MS who have various clinical phenotypes experience different abnormalities in activation and effective connectivity between the right cerebellum and frontoparietal areas, which contribute to inefficient cortical reorganization, with increasing cognitive load.

SUPPLEMENTAL MATERIAL

http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120216/-/DC1.

Superior temporal gyrus thickness correlates with cognitive performance in multiple sclerosis

Decreased cortical thickness that signifies gray matter pathology and its impact on cognitive performance is a research field with growing interest in relapsing-remitting multiple sclerosis (RRMS) and needs to be further elucidated. Using high-field 3.0 T MRI, three-dimensional T1-FSPGR (voxel size 1 × 1 × 1 mm) cortical thickness was measured in 82 regions in the left hemisphere (LH) and right hemisphere (RH) in 20 RRMS patients with low disease activity and in 20 age-matched healthy subjects that in parallel underwent comprehensive cognitive evaluation. The correlation between local cortical atrophy and cognitive performance was examined. We identified seven regions with cortical tissue loss that differed between RRMS and age-matched healthy controls. These regions were mainly located in the frontal and temporal lobes, specifically within the gyrus rectus, inferior frontal sulcus, orbital gyrus, parahippocampal gyrus, and superior temporal gyrus, with preferential left asymmetry. Increased cortical thickness was identified in two visual sensory regions, the LH inferior occipital gyrus, and the RH cuneus, implicating adaptive plasticity. Correlation analysis demonstrated that only the LH superior temporal gyrus thickness was associated with cognitive performance and its thickness correlated with motor skills (r = 0.65, p = 0.003), attention (r = 0.45, p = 0.042), and information processing speed (r = 0.50, p = 0.025). Our findings show that restricted cortical thinning occurs in RRMS patients with mild disease and that LH superior temporal gyrus atrophy is associated with cognitive dysfunction.

Cognitive and neurobehavioral features in multiple sclerosis

Multiple sclerosis (MS) is the most common nontraumatic neurological condition of early and middle adulthood. Cognitive and neurobehavioral problems associated with this disorder are common. Approximately 50% of MS patients experience lifetime clinical depression, and at least 50% will experience significant cognitive difficulties. Fatigue is also extremely common and disabling in MS and appears to be associated with sleep problems and primary neurological features, in addition to secondary factors, including depression and pain. Quality of life is affected in MS by all of these factors and is an especially salient issue given that patients often live for many years following diagnosis. In this article, we explore the literature on cognitive and neurobehavioral features in MS, provide a commentary on the state of the literature and make suggestions for research directions over the next 5 years that would move the field forward significantly.