Dataset Information

Cerebellar lobules and dentate nuclei mirror cortical force-related-BOLD responses: Beyond all (linear) expectations.

ABSTRACT: The relationship between the BOLD response and an applied force was quantified in the cerebellum using a power grip task. To investigate whether the cerebellum responds in an on/off way to motor demands or contributes to motor responses in a parametric fashion, similarly to the cortex, five grip force levels were investigated under visual feedback. Functional MRI data were acquired in 13 healthy volunteers and their responses were analyzed using a cerebellum-optimized pipeline. This allowed us to evaluate, within the cerebellum, voxelwise linear and non-linear associations between cerebellar activations and forces. We showed extensive non-linear activations (with a parametric design), covering the anterior and posterior lobes of the cerebellum with a BOLD-force relationship that is region-dependent. Linear responses were mainly located in the anterior lobe, similarly to the cortex, where linear responses are localized in M1. Complex responses were localized in the posterior lobe, reflecting its key role in attention and executive processing, required during visually guided movement. Given the highly organized responses in the cerebellar cortex, a key question is whether deep cerebellar nuclei show similar parametric effects. We found positive correlations with force in the ipsilateral dentate nucleus and negative correlations on the contralateral side, suggesting a somatotopic organization of the dentate nucleus in line with cerebellar and cortical areas. Our results confirm that there is cerebellar organization involving all grey matter structures that reflect functional segregation in the cortex, where cerebellar lobules and dentate nuclei contribute to complex motor tasks with different BOLD response profiles in relation to the forces. Hum Brain Mapp 38:2566-2579, 2017. © 2017 Wiley Periodicals, Inc.

SUBMITTER: Alahmadi AA

PROVIDER: S-EPMC5413835 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature

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Cerebellar lobules and dentate nuclei mirror cortical force-related-BOLD responses: Beyond all (linear) expectations.

Alahmadi Adnan A S AA Pardini Matteo M Samson Rebecca S RS Friston Karl J KJ Toosy Ahmed T AT D'Angelo Egidio E Gandini Wheeler-Kingshott Claudia A M CA

Human brain mapping 20170227 5

The relationship between the BOLD response and an applied force was quantified in the cerebellum using a power grip task. To investigate whether the cerebellum responds in an on/off way to motor demands or contributes to motor responses in a parametric fashion, similarly to the cortex, five grip force levels were investigated under visual feedback. Functional MRI data were acquired in 13 healthy volunteers and their responses were analyzed using a cerebellum-optimized pipeline. This allowed us t ...[more]

PMID: 28240422

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Project description:ObjectiveCerebellar transcranial direct current stimulation (ctDCS) is challenging due to the complexity of the cerebellar structure which is reflected by the well-known variability in ctDCS effects. Therefore, our objective is to present a freely available computational modeling pipeline for cerebellar lobules' optimal stimulation (CLOS).MethodsCLOS can optimize lobule-specific electric field distribution following finite element analysis (FEA) using freely available computational modeling pipelines. We modeled published ctDCS montages with 5 cm × 5 cm anode placed 3 cm lateral to inion, and the same sized cathode was placed on the: (1) contralateral supra-orbital area (called Manto montage), and (2) buccinators muscle (called Celnik montage). Also, a published (3) 4×1 HD-ctDCS electrode montage was modeled. We also investigated the effects of the subject-specific head model versus Colin 27 average head model on lobule-specific electric field distribution. Three-way analysis of variance (ANOVA) was used to determine the effects of lobules, montage, and head model on the electric field distribution. The differences in lobule-specific electric field distribution across different freely available computational pipelines were also evaluated using subject-specific head model. We also presented an application of our computational pipeline to optimize a ctDCS electrode montage to deliver peak electric field at the cerebellar lobules VII-IX related to ankle function.ResultsEta-squared effect size after three-way ANOVA for electric field strength was 0.05 for lobule, 0.00 for montage, 0.04 for the head model, 0.01 for lobule?montage interaction, 0.01 for lobule? head model interaction, and 0.00 for montage?head model interaction. The electric field strength of both the Celnik and the Manto montages affected the lobules Crus I/II, VIIb, VIII, and IX of the targeted cerebellar hemisphere where Manto montage had a spillover to the contralateral cerebellar hemisphere. The 4×1 HD-ctDCS montage primarily affected the lobules Crus I/II of the targeted cerebellar hemisphere. All three published ctDCS montages were found to be not optimal for ankle function (lobules VII-IX), so we presented a novel HD-ctDCS electrode montage.DiscussionOur freely available CLOS pipeline can be leveraged to optimize electromagnetic stimulation to target cerebellar lobules related to different cognitive and motor functions.

Project description:Motivation and methodExisting rational expectations models cannot satisfactorily explain why political budget manipulations systematically raise re-election chances and only occur in "specific contexts". This paper offers a theoretical explanation by including unsophisticated voters into an opportunistic political cycle model; unsophisticated voters are unable to take the optimal behaviour of other agents (fully) into account, but may, nonetheless, vaguely suspect government deception.ResultsFirst, rationally expected manipulations are, on average, fruitless in equilibrium. By including unsophisticated voters we can, however, corroborate empirically found electoral effects of political budget manipulations. Second, unsophisticated voters become anxious and suspicious in an intransparent or uncertain world, but the government tries to "outperform" their scepticism by increasing budget manipulations in order to appear more competent and, ultimately, increase re-election chances. It is, therefore, not surprising that political budget cycles are observed in countries suffering from intransparencies such as developing countries or new democracies. Third and in addition, the model presented here predicts that political opportunism produces, unintentionally, a countercyclical policy effect in election years, thereby, for instance, alleviating the typical problem of policy procyclicality in developing countries.Additional contributionThe paper also offers a theoretical explanation for political distortions found in forecasts by US states. Based on overly optimistic revenue forecasts the incumbent state government can conduct expansionary fiscal policies in order to appear more competent prior to an upcoming election. Since the resulting deficit can only be observed afterwards, the government can effectively circumvent a constitutional balanced budget constraint. As a result, there are political forecast and budget cycles in the state. More generally, however, these findings may also apply to European countries where balanced budget constraints are or will be in place (for instance the debt brakes in Switzerland and Germany); similarly, they apply to the supra-national European Fiscal Compact of the European Union.

Dataset Information

Cerebellar lobules and dentate nuclei mirror cortical force-related-BOLD responses: Beyond all (linear) expectations.

Publications

Cerebellar lobules and dentate nuclei mirror cortical force-related-BOLD responses: Beyond all (linear) expectations.

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