A fronto–striato–subthalamic–pallidal network for goal-directed and habitual inhibition

Abnormal asymmetries in subcortical brain volume in early adolescents with subclinical psychotic experiences

Subcortical structures may have an important role in the pathophysiology of psychosis. Our recent mega-analysis of structural magnetic resonance imaging (MRI) data has reported subcortical volumetric and lateralization alterations in chronic schizophrenia, including leftward asymmetric increases in pallidal volume. The question remains, however, whether these characteristics may represent vulnerability to the development of psychosis or whether they are epiphenomena caused by exposure to medication or illness chronicity. Subclinical psychotic experiences (SPEs) occur in some adolescents in the general population and increase the odds of developing psychosis in young adulthood. Investigations into the association between SPEs and MRI-measured volumes of subcortical structures in the general adolescent population would clarify the issue. Here, we collected structural MRI data in a subsample (10.5-13.3 years old) of a large-scale population-based cohort and explored subcortical volume and lateralization alterations related to SPEs (N = 203). Adolescents with SPEs demonstrated significant volumetric increases in the left hippocampus, right caudate, and right lateral ventricle, as well as a marginally significant increase in the left pallidum. Furthermore, adolescents with SPEs showed significantly more leftward laterality of pallidal volume than individuals without SPEs, which replicates our mega-analysis findings in chronic schizophrenia. We suggest that leftward asymmetries in pallidal volume already present in early adolescence may underlie the premorbid predisposition for developing psychosis in later life.

The Anatomy of Inference: Generative Models and Brain Structure

To infer the causes of its sensations, the brain must call on a generative (predictive) model. This necessitates passing local messages between populations of neurons to update beliefs about hidden variables in the world beyond its sensory samples. It also entails inferences about how we will act. Active inference is a principled framework that frames perception and action as approximate Bayesian inference. This has been successful in accounting for a wide range of physiological and behavioral phenomena. Recently, a process theory has emerged that attempts to relate inferences to their neurobiological substrates. In this paper, we review and develop the anatomical aspects of this process theory. We argue that the form of the generative models required for inference constrains the way in which brain regions connect to one another. Specifically, neuronal populations representing beliefs about a variable must receive input from populations representing the Markov blanket of that variable. We illustrate this idea in four different domains: perception, planning, attention, and movement. In doing so, we attempt to show how appealing to generative models enables us to account for anatomical brain architectures. Ultimately, committing to an anatomical theory of inference ensures we can form empirical hypotheses that can be tested using neuroimaging, neuropsychological, and electrophysiological experiments.

The frontal aslant tract (FAT) and its role in speech, language and executive function

In this review, we examine the structural connectivity of a recently-identified fiber pathway, the frontal aslant tract (FAT), and explore its function. We first review structural connectivity studies using tract-tracing methods in non-human primates, and diffusion-weighted imaging and electrostimulation in humans. These studies suggest a monosynaptic connection exists between the lateral inferior frontal gyrus and the pre-supplementary and supplementary motor areas of the medial superior frontal gyrus. This connection is termed the FAT. We then review research on the left FAT's putative role in supporting speech and language function, with particular focus on speech initiation, stuttering and verbal fluency. Next, we review research on the right FAT's putative role supporting executive function, namely inhibitory control and conflict monitoring for action. We summarize the extant body of empirical work by suggesting that the FAT plays a domain general role in the planning, timing, and coordination of sequential motor movements through the resolution of competition among potential motor plans. However, we also propose some domain specialization across the hemispheres. On the left hemisphere, the circuit is proposed to be specialized for speech actions. On the right hemisphere, the circuit is proposed to be specialized for general action control of the organism, especially in the visuo-spatial domain. We close the review with a discussion of the clinical significance of the FAT, and suggestions for further research on the pathway.

Negation markers inhibit motor routines during typing of manual action verbs

We explored whether negation markers recruit inhibitory mechanisms during keyboard-based action-verb typing. In each trial, participants read two sentences: the first featured a context (There is a contract) and the second ended with a relevant verb which had to be immediately typed. Crucially, the verb could describe manual actions, non-manual actions or non-motor processes, with either affirmative (You do sign it) or negative (You don't sign it) polarity. We assessed the impact of verb type and polarity on two typing dimensions: motor programming (lapse between target onset and first keystroke) and motor execution (lapse between first and last keystroke). Negation yielded no effect on motor planning, but it selectively delayed typing execution for manual-action verbs, irrespective of the subjects' typing skills. This suggests that processing negations during comprehension of manual-action sentences recruits inhibitory mechanisms acting on same-effector movements. Our novel finding extends embodied models of language and effector-specific motor-language integration.

Altered Functional Interactions of Inhibition Regions in Cognitively Normal Parkinson's Disease

Deficient inhibitory control in Parkinson's disease (PD) is often observed in situations requiring inhibition of impulsive or prepotent behaviors. Although activation of the right-hemisphere frontal-basal ganglia response inhibition network is partly altered in PD, disturbances in interactions of these regions are poorly understood, especially in patients without cognitive impairment. The present study investigated context-dependent connectivity of response inhibition regions in PD patients with normal cognition and control participants who underwent fMRI while performing a stop signal task. PD participants were tested off antiparkinsonian medication. To determine if functional disturbances depended on underlying brain structure, aberrant connectivity was correlated with brain volume and white-matter tissue diffusivity. We found no group differences in response inhibition proficiency. Yet the PD group showed functional reorganization in the long-range connectivity of inhibition regions, despite preserved within network connectivity. Successful inhibition in PD differed from the controls by strengthened connectivity of cortical regions, namely the right dorsolateral prefrontal cortex, pre-supplementary motor area and right caudal inferior frontal gyrus, largely with ventral and dorsal attention regions, but also the substantia nigra and default mode network regions. Successful inhibition in controls was distinguished by strengthened connectivity of the right rostral inferior frontal gyrus and subcortical inhibition nodes (right caudate, substantia nigra, and subthalamic nucleus). In both groups, the strength of context-dependent connectivity correlated with various indices of response inhibition performance. Mechanisms that may underlie aberrantly stronger context-specific connectivity include reduced coherence within reorganized systems, compensatory mechanisms, and/or the reorganization of intrinsic networks. In PD, but not controls, abnormally strengthened connectivity was linked to individual differences in underlying brain volumes and tissue diffusivity, despite no group differences in structural variables. The pattern of structural-functional associations suggested that subtle decreases in tissue diffusivity of underlying tracts and posterior cortical volumes may undermine the enhancement of normal cortical-striatal connectivity or cause strengthening in cortical-cortical connectivity. These novel findings demonstrate that functionally reorganized interactions of inhibition regions predates the development of inhibition deficits and clinically significant cognitive impairment in PD. We speculate that altered interactions of inhibition regions with attention-related networks and the dopaminergic system may presage future decline in inhibitory control.

Central Executive and Default Mode Network Intranet work Functional Connectivity Patterns in Chronic Migraine

Background:

The neural mechanisms of chronic migraine remain largely unknown but linked to the decreased connectivity to intrinsic brain networks.

Objective:

To characterize the intranetwork functional connectivity within the Central Executive Network (CEN) and Default Mode Network (DMN) in chronic migraine (CM), with and without medication overuse headache (MOH).

Methods:

Using functional magnetic resonance imaging, we performed post-hoc analysis of a total of 136 pairs of nodes to node functional connectivity (NTNC) within the CEN and 6 pairs of NTNC within the DMN in CM (n=13) and CM^MOH (n=16) as compared to controls, and between these two subgroups.

Results:

Connectivity between right ventrolateral prefrontal cortex (PFC) to contralateral anterior thalamus and connectivity between left dorsal PFC/frontal eye field (FEF) to dorsomedial PFC were decreased within the CEN in both CM and CM^MOH subgroups. In the CEN, there was more widespread disruption in the CM^MOH (n=16) versus CM (n=13), when compared to healthy controls. Within the subgroups, connectivity between right inferior frontal gyrus to left dorsolateral PFC was decreased in CM^MOH compared to CM. In the DMN, only one NTNC (left lateral parietal to precuneus/PCC) was disrupted in the CM^MOH group when compared to controls.

Conclusion:

There are similar patterns of NTNC dysfunction within CEN in CM regardless of MOH status. We observed more extensive intranetwork disruption in CM^MOH than CM. The decreased coherence between the right inferior frontal gyrus and the left dorsolateral PFC in CM^MOH is likely associated with a significant disruption in the inhibitory control and a maladaptive response in risk aversion and reward; whereas the decreased coherence between right dorsolateral and ventrolateral PFC to contralateral dorsal PFC/FEF may be related to lack of cognitive control and top-down regulation of pain in both CM and CM^MOH.

The Discrete and Continuous Brain: From Decisions to Movement-And Back Again

To act upon the world, creatures must change continuous variables such as muscle length or chemical concentration. In contrast, decision making is an inherently discrete process, involving the selection among alternative courses of action. In this article, we consider the interface between the discrete and continuous processes that translate our decisions into movement in a Newtonian world-and how movement informs our decisions. We do so by appealing to active inference, with a special focus on the oculomotor system. Within this exemplar system, we argue that the superior colliculus is well placed to act as a discrete-continuous interface. Interestingly, when the neuronal computations within the superior colliculus are formulated in terms of active inference, we find that many aspects of its neuroanatomy emerge from the computations it must perform in this role.

Revealing a novel nociceptive network that links the subthalamic nucleus to pain processing

Pain is a prevalent symptom of Parkinson's disease, and is effectively treated by deep brain stimulation of the subthalamic nucleus (STN). However, the link between pain and the STN remains unclear. In the present work, using in vivo electrophysiology in rats, we report that STN neurons exhibit complex tonic and phasic responses to noxious stimuli. We also show that nociception is altered following lesions of the STN, and characterize the role of the superior colliculus and the parabrachial nucleus in the transmission of nociceptive information to the STN, physiologically from both structures and anatomically in the case of the parabrachial nucleus. We show that STN nociceptive responses are abnormal in a rat model of PD, suggesting their dependence on the integrity of the nigrostriatal dopaminergic system. The STN-linked nociceptive network that we reveal is likely to be of considerable clinical importance in neurological diseases involving a dysfunction of the basal ganglia.

Dissecting executive control circuits with neuron types

Executive control supports our ability to behave flexibly in accordance with a given situation. In order to fully understand how cortical circuits achieve this task, we need to determine the intrinsic physiological and connection profiles of neuron types and analyze their functional roles during behavior. This article introduces current knowledge regarding neuron type classification in the cortex and reviews our understanding of how each neuron type is incorporated in the functional cortical circuit to implement executive control. Recent work using neuron-type specific imaging/recording has begun to reveal significant functional organizations of pyramidal neurons and their subtypes depending on the layers and long-range projection targets. GABAergic interneurons also make crucial contributions to executive control in a subtype-specific manner. Vasoactive intestinal peptide (VIP)-positive interneurons are preferentially recruited by top-down inputs from higher-order cortical regions and amplify the signals in pyramidal neurons by inhibiting other interneuron subtypes. Particularly in the prefrontal cortex, one of the hierarchically highest cortices, executive control signals are regulated by the VIP neuron-mediated disinhibition and robustly maintained through recurrent connections at a long time scale. The differences and commonalities in the functional organization between sensory areas and the prefrontal cortex are discussed.

The Relationship between Saccades and Locomotion

Human locomotion involves a complex interplay among multiple brain regions and depends on constant feedback from the visual system. We summarize here the current understanding of the relationship among fixations, saccades, and gait as observed in studies sampling eye movements during locomotion, through a review of the literature and a synthesis of the relevant knowledge on the topic. A significant overlap in locomotor and saccadic neural circuitry exists that may support this relationship. Several animal studies have identified potential integration nodes between these overlapping circuitries. Behavioral studies that explored the relationship of saccadic and gait-related impairments in normal conditions and in various disease states are also discussed. Eye movements and locomotion share many underlying neural circuits, and further studies can leverage this interplay for diagnostic and therapeutic purposes.

A Multilevel Computational Characterization of Endophenotypes in Addiction

Addiction is characterized by a profound intersubject (phenotypic) variability in the expression of addictive symptomatology and propensity to relapse following treatment. However, laboratory investigations have primarily focused on common neural substrates in addiction and have not yet been able to identify mechanisms that can account for the multifaceted phenotypic behaviors reported in the literature. To fill this knowledge gap theoretically, here we simulated phenotypic variations in addiction symptomology and responses to putative treatments, using both a neural model, based on cortico-striatal circuit dynamics, and an algorithmic model of reinforcement learning (RL). These simulations rely on the widely accepted assumption that both the ventral, model-based, goal-directed system and the dorsal, model-free, habitual system are vulnerable to extra-physiologic dopamine reinforcements triggered by addictive rewards. We found that endophenotypic differences in the balance between the two circuit or control systems resulted in an inverted-U shape in optimal choice behavior. Specifically, greater unbalance led to a higher likelihood of developing addiction and more severe drug-taking behaviors. Furthermore, endophenotypes with opposite asymmetrical biases among cortico-striatal circuits expressed similar addiction behaviors, but responded differently to simulated treatments, suggesting personalized treatment development could rely on endophenotypic rather than phenotypic differentiations. We propose our simulated results, confirmed across neural and algorithmic levels of analysis, inform on a fundamental and, to date, neglected quantitative method to characterize clinical heterogeneity in addiction.

Area-specific Modulation of Functional Cortical Activity During Block-based and Trial-based Proactive Inhibition

Animals can suppress their behavioral response in advance according to changes in environmental context (proactive inhibition: delaying the start of response), a process in which several cortical areas may participate. However, it remains unclear how this process is adaptively regulated according to contextual changes on different timescales. To address the issue, we used an improved stop-signal task paradigm to behaviorally and electrophysiologically characterize the temporal aspect of proactive inhibition in head-fixed rats. In the task, they must respond to a go cue as quickly as possible (go trial), but did not have to respond if a stop cue followed the go cue (stop trial). The task alternated between a block of only go trials (G-block) and a block of go-and-stop trials (GS-block). We observed block-based and trial-based proactive inhibition (emerging in GS-block and after stop trial, respectively) by behaviorally evaluating the delay in reaction time in correct go trials depending on contextual changes on different timescales. We electrophysiologically analyzed task-related neuronal activity in the primary and secondary motor, posterior parietal, and orbitofrontal cortices (M1, M2, PPC, and OFC, respectively). Under block-based proactive inhibition, spike activity of cue-preferring OFC neurons was attenuated continuously, while M1 and M2 activity was enhanced during motor preparation. Subsequently, M1 activity was attenuated during motor decision/execution. Under trial-based proactive inhibition, the OFC activity was continuously enhanced, and PPC and M1 activity was also enhanced shortly during motor decision/execution. These results suggest that different cortical mechanisms underlie the two types of proactive inhibition in rodents.

The neuroanatomical and neurochemical basis of apathy and impulsivity in frontotemporal lobar degeneration

Apathy and impulsivity are common and often coexistent consequences of frontotemporal lobar degeneration (FTLD). They increase patient morbidity and carer distress, but remain under-estimated and poorly treated. Recent trans-diagnostic approaches that span the spectrum of clinical presentations of FTLD and parkinsonism, indicate that apathy and impulsivity can be fractionated into multiple neuroanatomical and pharmacological systems. These include ventral/dorsal fronto-striatal circuits for reward-sensitivity, response-inhibition, and decision-making; moderated by noradrenaline, dopamine, and serotonin. Improved assessment tools, formal models of cognition and behavior, combined with brain imaging and psycho-pharmacology, are creating new therapeutic targets and establishing principles for stratification in future clinical trials.

Brain GABA Levels Are Associated with Inhibitory Control Deficits in Older Adults

Healthy aging is accompanied by motor inhibition deficits that involve a slower process of stopping a prepotent motor response (i.e., reactive inhibition) rather than a diminished ability to anticipate stopping (i.e., proactive inhibition). Some studies suggest that efficient motor inhibition is related to GABAergic function. Since age-related alterations in the GABA system have also been reported, motor inhibition impairments might be linked to GABAergic alterations in the cortico-subcortical network that mediates motor inhibition. Thirty young human adults (mean age, 23.2 years; age range, 18-34 years; 14 men) and 29 older human adults (mean age, 67.5 years; age range, 60-74 years; 13 men) performed a stop-signal task with varying levels of stop-signal probability. GABA⁺ levels were measured with magnetic resonance spectroscopy (MRS) in right inferior frontal cortex, pre-supplementary motor area (pre-SMA), left sensorimotor cortex, bilateral striatum, and occipital cortex. We found that reactive inhibition was worse in older adults compared with young adults, as indicated by longer stop-signal reaction times (SSRTs). No group differences in proactive inhibition were observed as both groups slowed down their response to a similar degree with increasing stop-signal probability. The MRS results showed that tissue-corrected GABA⁺ levels were on average lower in older as compared with young adults. Moreover, older adults with lower GABA⁺ levels in the pre-SMA were slower at stopping (i.e., had longer SSRTs). These findings suggest a role for the GABA system in reactive inhibition deficits.SIGNIFICANCE STATEMENT Inhibitory control has been shown to diminish as a consequence of aging. We investigated whether the ability to stop a prepotent motor response and the ability to prepare to stop were related to GABA levels in different regions of the network that was previously identified to mediate inhibitory control. Overall, we found lower GABA levels in older adults compared with young adults. Importantly, those older adults who were slower at stopping had less GABA in the pre-supplementary motor area, a key node of the inhibitory control network. We propose that deficits in the stop process in part depend on the integrity of the GABA system.

Systems Neuroscience of Psychosis: Mapping Schizophrenia Symptoms onto Brain Systems

Schizophrenia research has been in a deadlock for many decades. Despite important advances in clinical treatment, there are still major concerns regarding long-term psychosocial reintegration and disease management, biological heterogeneity, unsatisfactory predictors of individual course and treatment strategies, and a confusing variety of controversial theories about its etiology and pathophysiological mechanisms. In the present perspective on schizophrenia research, we first discuss a methodological pitfall in contemporary schizophrenia research inherent in the attempt to link mental phenomena with the brain: we claim that the time-honored phenomenological method of defining mental symptoms should not be contaminated with the naturalistic approach of modern neuroscience. We then describe our Systems Neuroscience of Psychosis (SyNoPsis) project, which aims to overcome this intrinsic problem of psychiatric research. Considering schizophrenia primarily as a disorder of interindividual communication, we developed a neurobiologically informed semiotics of psychotic disorders, as well as an operational clinical rating scale. The novel psychopathology allows disentangling the clinical manifestations of schizophrenia into behavioral domains matching the functions of three well-described higher-order corticobasal brain systems involved in interindividual human communication, namely, the limbic, associative, and motor loops, including their corticocortical sensorimotor connections. The results of several empirical studies support the hypothesis that the proposed three-dimensional symptom structure, segregated into the affective, the language, and the motor domain, can be specifically mapped onto structural and functional abnormalities of the respective brain systems. New pathophysiological hypotheses derived from this brain system-oriented approach have helped to develop and improve novel treatment strategies with noninvasive brain stimulation and practicable clinical parameters. In clinical practice, the novel psychopathology allows confining the communication deficits of the individual patient, shifting attention from the symptoms to the intact resources. We have studied this approach and observed important advantages for therapeutic alliances, personalized treatment, and de-escalation strategies. Future studies will further conjoin clinical definitions of psychotic symptoms with brain structures and functions, and disentangle structural and functional deficit patterns within these systems to identify neurobiologically distinct subsyndromes. Neurobiologically homogeneous patient groups may provide new momentum for treatment research. Finally, lessons learned from schizophrenia research may contribute to developing a comprehensive perspective on human experience and behavior that integrates methodologically distinct, but internally consistent, insights from humanities and neuroscience.

The Connectivity Fingerprint of the Human Frontal Cortex, Subthalamic Nucleus, and Striatum

Within the cortico basal ganglia (BG)-thalamic network, the direct and indirect pathways comprise of projections from the cortex to the striatum (STR), whereas the hyperdirect pathway(s) consist of cortical projections toward the subthalamic nucleus (STN). Each pathway possesses a functionally distinct role for action selection. The current study quantified and compared the structural connectivity between 17 distinct cortical areas with the STN and STR using 7 Tesla diffusion weighted magnetic resonance imaging (dMRI) and resting-state functional MRI (rs-fMRI) in healthy young subjects. The selection of these cortical areas was based on a literature search focusing on animal tracer studies. The results indicate that, relative to other cortical areas, both the STN and STR showed markedly weaker structural connections to areas assumed to be essential for action inhibition such as the inferior frontal cortex pars opercularis. Additionally, the cortical connectivity fingerprint of the STN and STR indicated relatively strong connections to areas related to voluntary motor initiation such as the cingulate motor area and supplementary motor area. Overall the results indicated that the cortical-STN connections were sparser compared to the STR. There were two notable exceptions, namely for the orbitofrontal cortex and ventral medial prefrontal cortex, where a higher tract strength was found for the STN. These two areas are thought to be involved in reward processing and action bias.

Consolidation of a Learned Skill Correlates with Dopamine SPECT Uptake in Early Parkinson's Disease

BACKGROUND AND PURPOSE

Basal ganglia play a pivotal role in procedural memory. However, the correlation between skill learning and striatal ¹²³I-ioflupane uptake in Parkinson's disease (PD) has not been reported previously. Our objective was to determine whether visuomotor skill learning is associated with striatal ¹²³I-ioflupane uptake in early PD.

METHODS

We designed a case-control study to assess learning and consolidation of a visuomotor learning task (mirrored drawing of star-shaped figures) performed on two consecutive days by early-PD patients (disease duration <2 years) and age-matched healthy subjects. Outcomes were the error rate and time per trial, as well as performance indices to assess the relative improvement on the first day (learning) and the retention on the second day (consolidation). For PD patients, we evaluated the correlation of skill learning with semiquantitative ¹²³I-ioflupane uptake.

RESULTS

We included 9 PD patients and 10 control subjects with the same baseline characteristics (age, male/female ratio, educational level, Mini Mental State Examination score, and Hospital Anxiety and Depression Scale score, all p>0.18) other than the score on part III of the Movement Disorders Society Unified Parkinson's Disease Rating Scale, which was higher in the PD patients (mean±SD: 15.0±10.4 vs. 1.3±1.1, p<0.001). The learning indices were the same in the two groups (p>0.5), whereas PD patients showed a lower consolidation index for the time per trial (p=0.009). Moreover, this performance was correlated with uptake in the right caudate nucleus (Spearman's rho=0.82, p=0.007) and the right striatum (Spearman's rho=0.67, p=0.049), including when multiple linear regression adjusting for the levodopa equivalent daily dose was performed (p=0.005 for the caudate nucleus and p=0.024 for the striatum).

CONCLUSIONS

This study provides evidence of a correlation between procedural memory impairment and striatal dopaminergic dysfunction in early PD.

Surprise: A More Realistic Framework for Studying Action Stopping?

Motor inhibition enables rapid action stopping, even post initiation. When action stopping is anticipated (such as in laboratory stopping tasks), inhibition is engaged proactively. Such proactive inhibition changes the physiological implementation of action stopping. However, many real-world action-stopping scenarios involve little proactive inhibition. To investigate purely reactive inhibition, researchers need a different paradigm: studying surprise.

Characterization of Tissue Plasminogen Activator Expression and Trafficking in the Adult Murine Brain

Tissue plasminogen activator (tPA) is an immediate-early gene important for regulating physiological processes like synaptic plasticity and neurovascular coupling. It has also been implicated in several pathological processes including blood-brain barrier (BBB) permeability, seizure progression, and stroke. These varied reports suggest that tPA is a pleiotropic mediator whose actions are highly compartmentalized in space and time. The specific localization of tPA, therefore, can provide useful information about its function. Accordingly, the goal of this study was to provide a detailed characterization of tPA's regional, cellular, and subcellular localization in the brain. To achieve this, two new transgenic mouse lines were utilized: (1) a PlatβGAL reporter mouse, which houses the β-galactosidase gene in the tPA locus and (2) a tPABAC-Cerulean mouse, which has a cerulean-fluorescent protein fused in-frame to the tPA C-terminus. Using these two transgenic reporters, we show that while tPA is expressed throughout most regions of the adult murine brain, it appears to be preferentially targeted to fiber tracts in the limbic system. In the hippocampus, confocal microscopy revealed tPA-Cerulean (tPA-Cer) puncta localized to giant mossy fiber boutons (MFBs) and astrocytes in stratum lucidum. With amplification of the tPA-Cer signal, somatically localized tPA was also observed in the stratum oriens (SO)/alveus layer of both CA1 and CA3 subfields. Coimmunostaining of tPA-Cer and interneuronal markers indicates that these tPA-positive cell bodies belong to a subclass of somatostatin (SST)/oriens-lacunosum moleculare (O-LM) interneurons. Together, these data imply that tPA's localization is differentially regulated, suggesting that its neuromodulatory effects may be compartmentalized and specialized to cell type.

Deep temporal models and active inference

How do we navigate a deeply structured world? Why are you reading this sentence first - and did you actually look at the fifth word? This review offers some answers by appealing to active inference based on deep temporal models. It builds on previous formulations of active inference to simulate behavioural and electrophysiological responses under hierarchical generative models of state transitions. Inverting these models corresponds to sequential inference, such that the state at any hierarchical level entails a sequence of transitions in the level below. The deep temporal aspect of these models means that evidence is accumulated over nested time scales, enabling inferences about narratives (i.e., temporal scenes). We illustrate this behaviour with Bayesian belief updating - and neuronal process theories - to simulate the epistemic foraging seen in reading. These simulations reproduce perisaccadic delay period activity and local field potentials seen empirically. Finally, we exploit the deep structure of these models to simulate responses to local (e.g., font type) and global (e.g., semantic) violations; reproducing mismatch negativity and P300 responses respectively.

Bridging the Great Divide: What Can Neurology Learn From Psychiatry?

Neurology and psychiatry share common historical origins and rely on similar tools to study brain disorders. Yet the practical integration of medical and scientific approaches across these clinical neurosciences remains elusive. Although much has been written about the need to incorporate emerging systems-level, cellular-molecular, and genetic-epigenetic advances into a science of mind for psychiatric disorders, less attention has been given to applying clinical neuroscience principles to conceptualize neurologic conditions with an integrated neurobio-psycho-social approach. In this perspective article, the authors briefly outline the historically interwoven and complicated relationship between neurology and psychiatry. Through a series of vignettes, the authors then illustrate how some traditional psychiatric conditions are being reconceptualized in part as disorders of neurodevelopment and awareness. They emphasize the intersection of neurology and psychiatry by highlighting conditions that cut across traditional diagnostic boundaries. The authors argue that the divide between neurology and psychiatry can be narrowed by moving from lesion-based toward circuit-based understandings of neuropsychiatric disorders, from unidirectional toward bidirectional models of brain-behavior relationships, from exclusive reliance on categorical diagnoses toward transdiagnostic dimensional perspectives, and from silo-based research and treatments toward interdisciplinary approaches. The time is ripe for neurologists and psychiatrists to implement an integrated clinical neuroscience approach to the assessment and management of brain disorders. The subspecialty of behavioral neurology & neuropsychiatry is poised to lead the next generation of clinicians to merge brain science with psychological and social-cultural factors. These efforts will catalyze translational research, revitalize training programs, and advance the development of impactful patient-centered treatments.

Warping an atlas derived from serial histology to 5 high-resolution MRIs

Previous work from our group demonstrated the use of multiple input atlases to a modified multi-atlas framework (MAGeT-Brain) to improve subject-based segmentation accuracy. Currently, segmentation of the striatum, globus pallidus and thalamus are generated from a single high-resolution and -contrast MRI atlas derived from annotated serial histological sections. Here, we warp this atlas to five high-resolution MRI templates to create five de novo atlases. The overall goal of this work is to use these newly warped atlases as input to MAGeT-Brain in an effort to consolidate and improve the workflow presented in previous manuscripts from our group, allowing for simultaneous multi-structure segmentation. The work presented details the methodology used for the creation of the atlases using a technique previously proposed, where atlas labels are modified to mimic the intensity and contrast profile of MRI to facilitate atlas-to-template nonlinear transformation estimation. Dice's Kappa metric was used to demonstrate high quality registration and segmentation accuracy of the atlases. The final atlases are available at https://github.com/CobraLab/atlases/tree/master/5-atlas-subcortical.

The Discrete and Continuous Brain: From Decisions to Movement-And Back Again

To act upon the world, creatures must change continuous variables such as muscle length or chemical concentration. In contrast, decision making is an inherently discrete process, involving the selection among alternative courses of action. In this article, we consider the interface between the discrete and continuous processes that translate our decisions into movement in a Newtonian world—and how movement informs our decisions. We do so by appealing to active inference, with a special focus on the oculomotor system. Within this exemplar system, we argue that the superior colliculus is well placed to act as a discrete-continuous interface. Interestingly, when the neuronal computations within the superior colliculus are formulated in terms of active inference, we find that many aspects of its neuroanatomy emerge from the computations it must perform in this role.

Exogenously triggered response inhibition in developmental stuttering

PURPOSE

The purpose of the present study was to examine relations between children's exogenously triggered response inhibition and stuttering.

METHOD

Participants were 18 children who stutter (CWS; mean age = 9;01 years) and 18 children who not stutter (CWNS; mean age = 9;01 years). Participants were matched on age (±3 months) and gender. Response inhibition was assessed by a stop signal task (Verbruggen, Logan, & Stevens, 2008).

RESULTS

Results suggest that CWS, compared to CWNS, perform comparable to CWNS in a task where response control is externally triggered.

CONCLUSIONS

Our findings seem to indicate that previous questionnaire-based findings (Eggers, De Nil, & Van den Bergh, 2010) of a decreased efficiency of response inhibition cannot be generalized to all types of response inhibition.

Brain connectivity changes when comparing effects of subthalamic deep brain stimulation with levodopa treatment in Parkinson's disease

Levodopa and, later, deep brain stimulation (DBS) have become the mainstays of therapy for motor symptoms associated with Parkinson's disease (PD). Although these therapeutic options lead to similar clinical outcomes, the neural mechanisms underlying their efficacy are different. Therefore, investigating the differential effects of DBS and levodopa on functional brain architecture and associated motor improvement is of paramount interest. Namely, we expected changes in functional brain connectivity patterns when comparing levodopa treatment with DBS.

Clinical assessment and functional magnetic resonance imaging (fMRI) was performed before and after implanting electrodes for DBS in the subthalamic nucleus (STN) in 13 PD patients suffering from severe levodopa-induced motor fluctuations and peak-of-dose dyskinesia. All measurements were acquired in a within subject-design with and without levodopa treatment, and with and without DBS. Brain connectivity changes were computed using eigenvector centrality (EC) that offers a data-driven and parameter-free approach—similarly to Google's PageRank algorithm—revealing brain regions that have an increased connectivity to other regions that are highly connected, too. Both levodopa and DBS led to comparable improvement of motor symptoms as measured with the Unified Parkinson's Disease Rating Scale motor score (UPDRS-III). However, this similar therapeutic effect was underpinned by different connectivity modulations within the motor system. In particular, EC revealed a major increase of interconnectedness in the left and right motor cortex when comparing DBS to levodopa. This was accompanied by an increase of connectivity of these motor hubs with the thalamus and cerebellum.

We observed, for the first time, significant functional connectivity changes when comparing the effects of STN DBS and oral levodopa administration, revealing different treatment-specific mechanisms linked to clinical benefit in PD. Specifically, in contrast to levodopa treatment, STN DBS was associated with increased connectivity within the cortico-thalamo-cerebellar network. Moreover, given the favorable effects of STN DBS on motor complications, the changes in the patients' clinical profile might also contribute to connectivity changes associated with STN-DBS. Understanding the observed connectivity changes may be essential for enhancing the effectiveness of DBS treatment, and for better defining the pathophysiology of the disrupted motor network in PD.

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Functional MRI was done before and after implanting DBS electrodes in same patients.

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Impacts of DBS and levodopa administration on brain motor circuitry are different.

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Comparison between DBS and levodopa treatment shows a major connectivity increase.

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Treatment related connectivity changes can be disentangled from electrode implantation.

Functionally separated networks for self-paced and externally-cued motor execution in Parkinson's disease: Evidence from deep brain recordings in humans

Spatially segregated cortico-basal ganglia networks have been proposed for the control of goal-directed and habitual behavior. In Parkinson's disease, selective loss of dopaminergic neurons regulating sensorimotor (habitual) behavior might therefore predominantly cause deficits in habitual motor control, whereas control of goal-directed movement is relatively preserved. Following this hypothesis, we examined the electrophysiology of cortico-basal ganglia networks in Parkinson patients emulating habitual and goal-directed motor control during self-paced and externally-cued finger tapping, respectively, while simultaneously recording local field potentials in the subthalamic nucleus (STN) and surface EEG. Only externally-cued movements induced a pro-kinetic event-related beta-desynchronization, whereas beta-oscillations were continuously suppressed during self-paced movements. Connectivity analysis revealed higher synchronicity (phase-locking value) between the STN and central electrodes during self-paced and higher STN to frontal phase-locking during externally-cued movements. Our data provide direct electrophysiological support for the existence of functionally segregated cortico-basal ganglia networks controlling motor behavior in Parkinson patients, and corroborate the assumption of Parkinson patients being shifted from habitual towards goal-directed behavior.

Subthalamic oscillatory activity and connectivity during gait in Parkinson's disease

Local field potentials (LFP) of the subthalamic nucleus (STN) recorded during walking may provide clues for determining the function of the STN during gait and also, may be used as biomarker to steer adaptive brain stimulation devices. Here, we present LFP recordings from an implanted sensing neurostimulator (Medtronic Activa PC + S) during walking and rest with and without stimulation in 10 patients with Parkinson's disease and electrodes placed bilaterally in the STN. We also present recordings from two of these patients recorded with externalized leads. We analyzed changes in overall frequency power, bilateral connectivity, high beta frequency oscillatory characteristics and gait-cycle related oscillatory activity. We report that deep brain stimulation improves gait parameters. High beta frequency power (20-30 Hz) and bilateral oscillatory connectivity are reduced during gait, while the attenuation of high beta power is absent during stimulation. Oscillatory characteristics are affected in a similar way. We describe a reduction in overall high beta burst amplitude and burst lifetimes during gait as compared to rest off stimulation. Investigating gait cycle related oscillatory dynamics, we found that alpha, beta and gamma frequency power is modulated in time during gait, locked to the gait cycle. We argue that these changes are related to movement induced artifacts and that these issues have important implications for similar research.

Prevalence and predictors of hair pulling disorder and excoriation disorder in Tourette syndrome

Trichotillomania/hair pulling disorder (HPD) and excoriation/skin picking disorder (SPD) are childhood-onset, body-focused repetitive behaviors that are thought to share genetic susceptibility and underlying pathophysiology with obsessive-compulsive disorder (OCD) and Tourette syndrome (TS). We sought to determine the prevalence of DSM-5 HPD and SPD in TS patients, and to identify clinical factors most associated with their co-morbidity with TS. Participants included 811 TS patients recruited from TS specialty clinics for a multi-center genetic study. Patients were assessed using standardized, validated semi-structured interviews. HPD and SPD diagnoses were determined using a validated self-report questionnaire. HPD/SPD prevalence rates were calculated, and clinical predictors were evaluated using regression modeling. 3.8 and 13.0% of TS patients met DSM-5 criteria for HPD and SPD, respectively. In univariable analyses, female sex, OCD, and both tic and obsessive-compulsive symptom severity were among those associated with HPD and/or SPD. In multivariable analyses, only lifetime worst-ever motor tic severity remained significantly associated with HPD. Female sex, co-occurring OCD, ADHD, and motor tic severity remained independently associated with SPD. This is the first study to examine HPD and SPD prevalence in a TS sample using semi-structured diagnostic instruments. The prevalence of HPD and SPD in TS patients, and their association with increased tic severity and co-occurring OCD, suggests that clinicians should screen children with TS and related disorders for HPD/SPD, particularly in females and in those with co-occurring OCD. This study also helps set a foundation for subsequent research regarding HPD/SPD risk factors, pathophysiology, and treatment models.

Multi-polygenic score approach to trait prediction

A primary goal of polygenic scores, which aggregate the effects of thousands of trait-associated DNA variants discovered in genome-wide association studies (GWASs), is to estimate individual-specific genetic propensities and predict outcomes. This is typically achieved using a single polygenic score, but here we use a multi-polygenic score (MPS) approach to increase predictive power by exploiting the joint power of multiple discovery GWASs, without assumptions about the relationships among predictors. We used summary statistics of 81 well-powered GWASs of cognitive, medical and anthropometric traits to predict three core developmental outcomes in our independent target sample: educational achievement, body mass index (BMI) and general cognitive ability. We used regularized regression with repeated cross-validation to select from and estimate contributions of 81 polygenic scores in a UK representative sample of 6710 unrelated adolescents. The MPS approach predicted 10.9% variance in educational achievement, 4.8% in general cognitive ability and 5.4% in BMI in an independent test set, predicting 1.1%, 1.1%, and 1.6% more variance than the best single-score predictions. As other relevant GWA analyses are reported, they can be incorporated in MPS models to maximize phenotype prediction. The MPS approach should be useful in research with modest sample sizes to investigate developmental, multivariate and gene-environment interplay issues and, eventually, in clinical settings to predict and prevent problems using personalized interventions.

Cyclic AMP-producing chemogenetic activation of indirect pathway striatal projection neurons and the downstream effects on the globus pallidus and subthalamic nucleus in freely moving mice

The indirect pathway striatal medium spiny projection neurons (iMSNs) are critical to motor and cognitive brain functions. These neurons express a high level of cAMP-increasing adenosine A2a receptors. However, the potential effects of cAMP production on iMSN spiking activity have not been established, and recording identified iMSNs in freely moving animals is challenging. Here, we show that in the transgenic mice expressing cAMP-producing G protein G_s -coupled designer receptor exclusively activated by designer drug (Gs-DREADD) in iMSNs, the baseline spike firing in MSNs is normal, indicating DREADD expression does not affect the normal physiology of these neurons. Intraperitoneal injection of the DREADD agonist clozapine-N-oxide (CNO; 2.5 mg/kg) increased the spike firing in 50% of the recorded MSNs. However, CNO did not affect MSN firing in Gs-DREADD-negative mice. We also found that CNO injection inhibited the spike firing of globus pallidus external segment (GPe) neurons in Gs-DREADD-positive mice, further indicating CNO excitation of iMSNs. Temporally coincident with these effects on spiking firing in the indirect pathway, CNO injection selectively inhibited locomotion in D2 Gs-DREADD mice. Taken together, our results strongly suggest that cAMP production in iMSNs can increase iMSN spiking activity and cause motor inhibition, thus addressing a long-standing question about the cellular functions of the cAMP-producing adenosine A2a receptors in iMSNs. Cover Image for this issue: doi: 10.1111/jnc.14181.

Improving the Standard for Deep Brain Stimulation Therapy: Target Structures and Feedback Signals for Adaptive Stimulation. Current Perspectives and Future Directions

Deep brain stimulation (DBS) is an established therapeutic option for the treatment of various neurological disorders and has been used successfully in movement disorders for over 25 years. However, the standard stimulation schemes have not changed substantially. Two major points of interest for the further development of DBS are target-structures and novel adaptive stimulation techniques integrating feedback signals. We describe recent research results on target structures and on neural and behavioural feedback signals for adaptive deep brain stimulation (aDBS), as well as outline future directions.

Neural correlates of interference resolution in the multi-source interference task: a meta-analysis of functional neuroimaging studies

Background

Interference resolution refers to cognitive control processes enabling one to focus on task-related information while filtering out unrelated information. But the exact neural areas, which underlie a specific cognitive task on interference resolution, are still equivocal. The multi-source interference task (MSIT), as a particular cognitive task, is a well-established experimental paradigm used to evaluate interference resolution. Studies combining the MSIT with functional magnetic resonance imaging (fMRI) have shown that the MSIT evokes the dorsal anterior cingulate cortex (dACC) and cingulate–frontal–parietal cognitive-attentional networks. However, these brain areas have not been evaluated quantitatively and these findings have not been replicated.

Methods

In the current study, we firstly report a voxel-based meta-analysis of functional brain activation associated with the MSIT so as to identify the localization of interference resolution in such a specific cognitive task. Articles on MSIT-related fMRI published between 2003 and July 2017 were eligible. The electronic databases searched included PubMed, Web of Knowledge, and Google Scholar. Differential BOLD activation patterns between the incongruent and congruent condition were meta-analyzed in anisotropic effect-size signed differential mapping software.

Results

Robustness meta-analysis indicated that two significant activation clusters were shown to have reliable functional activity in comparisons between incongruent and congruent conditions. The first reliable activation cluster, which included the dACC, medial prefrontal cortex, supplementary motor area, replicated the previous MSIT-related fMRI study results. Furthermore, we found another reliable activation cluster comprising areas of the right insula, right inferior frontal gyrus, and right lenticular nucleus-putamen, which were not typically discussed in previous MSIT-related fMRI studies.

Conclusions

The current meta-analysis study presents the reliable brain activation patterns on MSIT. These findings suggest that the cingulate-frontal-striatum network and right insula may allow control demands to resolve interference on MSIT. These results provide new insights into the neural mechanisms underlying interference resolution.

Hierarchical Active Inference: A Theory of Motivated Control

Motivated control refers to the coordination of behaviour to achieve affectively valenced outcomes or goals. The study of motivated control traditionally assumes a distinction between control and motivational processes, which map to distinct (dorsolateral versus ventromedial) brain systems. However, the respective roles and interactions between these processes remain controversial. We offer a novel perspective that casts control and motivational processes as complementary aspects - goal propagation and prioritization, respectively - of active inference and hierarchical goal processing under deep generative models. We propose that the control hierarchy propagates prior preferences or goals, but their precision is informed by the motivational context, inferred at different levels of the motivational hierarchy. The ensuing integration of control and motivational processes underwrites action and policy selection and, ultimately, motivated behaviour, by enabling deep inference to prioritize goals in a context-sensitive way.

Altered functional connectivity of the subthalamus and the bed nucleus of the stria terminalis in obsessive-compulsive disorder

BACKGROUND

The assessment of inter-regional functional connectivity (FC) has allowed for the description of the putative mechanism of action of treatments such as deep brain stimulation (DBS) of the nucleus accumbens in patients with obsessive-compulsive disorder (OCD). Nevertheless, the possible FC alterations of other clinically-effective DBS targets have not been explored. Here we evaluated the FC patterns of the subthalamic nucleus (STN) and the bed nucleus of the stria terminalis (BNST) in patients with OCD, as well as their association with symptom severity.

METHODS

Eighty-six patients with OCD and 104 healthy participants were recruited. A resting-state image was acquired for each participant and a seed-based analysis focused on our two regions of interest was performed using statistical parametric mapping software (SPM8). Between-group differences in FC patterns were assessed with two-sample t test models, while the association between symptom severity and FC patterns was assessed with multiple regression analyses.

RESULTS

In comparison with controls, patients with OCD showed: (1) increased FC between the left STN and the right pre-motor cortex, (2) decreased FC between the right STN and the lenticular nuclei, and (3) increased FC between the left BNST and the right frontopolar cortex. Multiple regression analyses revealed a negative association between clinical severity and FC between the right STN and lenticular nucleus.

CONCLUSIONS

This study provides a neurobiological framework to understand the mechanism of action of DBS on the STN and the BNST, which seems to involve brain circuits related with motor response inhibition and anxiety control, respectively.

GABA and glutamate in children with Tourette syndrome: A 1H MR spectroscopy study at 7T

Tourette syndrome (TS) is characterized by presence of chronic, fluctuating motor and phonic tics. The underlying neurobiological basis for these movements is hypothesized to involve cortical-striatal-thalamo-cortical (CSTC) pathways. Two major neurotransmitters within these circuits are γ-aminobutyric acid (GABA) and glutamate. Seventy-five participants (32 with TS, 43 controls) ages 5-12 years completed ¹H MRS at 7T. GABA and glutamate were measured in dorsolateral prefrontal cortex (DLPFC), ventromedial prefrontal cortex (VMPFC), premotor cortex (PMC), and striatum, and metabolites quantified using LCModel. Participants also completed neuropsychological assessment emphasizing inhibitory control. Scans were well tolerated by participants. Across ROIs combined, glutamate was significantly higher in the TS group, compared to controls, with no significant group differences in GABA observed. ROI analyses revealed significantly increased PMC glutamate in the TS group. Among children with TS, increased PMC glutamate was associated with improved selective motor inhibition; however, no significant associations were identified between levels of glutamate or GABA and tic severity. The dopaminergic system has long been considered to have a dominant role in TS. Accumulating evidence, however, suggests involvement of other neurotransmitter systems. Data obtained using ¹H MRS at 7T supports alteration of glutamate within habitual behavior-related CSTC pathways of children with TS.

Subthalamic nucleus pathology contributes to repetitive behavior expression and is reversed by environmental enrichment

Repetitive motor behaviors are common in neurodevelopmental, psychiatric and neurological disorders. Despite their prevalence in certain clinical populations, our understanding of the neurobiological cause of repetitive behavior is lacking. Likewise, not knowing the pathophysiology has precluded efforts to find effective drug treatments. Our comparisons between mouse strains that differ in their expression of repetitive behavior showed an important role of the subthalamic nucleus (STN). In mice with high rates of repetitive behavior, we found significant differences in dendritic spine density, gene expression and neuronal activation in the STN. Taken together, these data show a hypoglutamatergic state. Furthermore, by using environmental enrichment to reduce repetitive behavior, we found evidence of increased glutamatergic tone in the STN with our measures of spine density and gene expression. These results suggest the STN is a major contributor to repetitive behavior expression and highlight the potential of drugs that increase STN function to reduce repetitive behavior in clinical populations.

The role of stress in the pathogenesis and maintenance of obsessive-compulsive disorder

Individuals with obsessive-compulsive disorder often identify psychosocial stress as a factor that exacerbates their symptoms, and many trace the onset of symptoms to a stressful period of life or a discrete traumatic incident. However, the pathophysiological relationship between stress and obsessive-compulsive disorder remains poorly characterized: it is unclear whether trauma or stress is an independent cause of obsessive-compulsive disorder symptoms, a triggering factor that interacts with a preexisting diathesis, or simply a nonspecific factor that can exacerbate obsessive-compulsive disorder along with other aspects of psychiatric symptomatology. Nonetheless, preclinical research has demonstrated that stress has conspicuous effects on corticostriatal and limbic circuitry. Specifically, stress can lead to neuronal atrophy in frontal cortices (particularly the medial prefrontal cortex), the dorsomedial striatum (caudate), and the hippocampus. Stress can also result in neuronal hypertrophy in the dorsolateral striatum (putamen) and amygdala. These neurobiological effects mirror reported neural abnormalities in obsessive-compulsive disorder and may contribute to an imbalance between goal-directed and habitual behavior, an imbalance that is implicated in the pathogenesis and expression of obsessive-compulsive disorder symptomatology. The modulation of corticostriatal and limbic circuits by stress and the resultant imbalance between habit and goal-directed learning and behavior offers a framework for investigating how stress may exacerbate or trigger obsessive-compulsive disorder symptomatology.

A model-based quantification of action control deficits in Parkinson's disease

Basal ganglia dysfunction in Parkinson's disease (PD) is thought to generate deficits in action control, but the characterization of these deficits have been qualitative rather than quantitative. Patients with PD typically show prolonged response times on tasks that instantiate a conflict between goal-directed processing and automatic response tendencies. In the Simon task, for example, the irrelevant location of the stimulus automatically activates a corresponding lateralized response, generating a potential conflict with goal-directed choices. We applied a new computational model of conflict processing to two sets of behavioral data from the Simon task to quantify the effects of PD and dopaminergic (DA) medication on action control mechanisms. Compared to healthy controls (HC) matched in age gender and education, patients with PD showed a deficit in goal-directed processing, and the magnitude of this deficit positively correlated with cognitive symptoms. Analyses of the time-course of the location-based automatic activation yielded mixed findings. In both datasets, we found that the peak amplitude of the automatic activation was similar between PD and HC, demonstrating a similar degree of response capture. However, PD patients showed a prolonged automatic activation in only one dataset. This discrepancy was resolved by theoretical analyses of conflict resolution in the Simon task. The reduction of interference generated by the automatic activation appears to be driven by a mixture of passive decay and top-down inhibitory control, the contribution of each component being modulated by task demands. Our results suggest that PD selectively impairs the inhibitory control component, a deficit likely remediated by DA medication. This work advances our understanding of action control deficits in PD, and illustrates the benefit of using computational models to quantitatively measure cognitive processes in clinical populations.

Value encoding in the globus pallidus: fMRI reveals an interaction effect between reward and dopamine drive

The external part of the globus pallidus (GPe) is a core nucleus of the basal ganglia (BG) whose activity is disrupted under conditions of low dopamine release, as in Parkinson's disease. Current models assume decreased dopamine release in the dorsal striatum results in deactivation of dorsal GPe, which in turn affects motor expression via a regulatory effect on other nuclei of the BG. However, recent studies in healthy and pathological animal models have reported neural dynamics that do not match with this view of the GPe as a relay in the BG circuit. Thus, the computational role of the GPe in the BG is still to be determined. We previously proposed a neural model that revisits the functions of the nuclei of the BG, and this model predicts that GPe encodes values which are amplified under a condition of low striatal dopaminergic drive. To test this prediction, we used an fMRI paradigm involving a within-subject placebo-controlled design, using the dopamine antagonist risperidone, wherein healthy volunteers performed a motor selection and maintenance task under low and high reward conditions. ROI-based fMRI analysis revealed an interaction between reward and dopamine drive manipulations, with increased BOLD activity in GPe in a high compared to low reward condition, and under risperidone compared to placebo. These results confirm the core prediction of our computational model, and provide a new perspective on neural dynamics in the BG and their effects on motor selection and cognitive disorders.

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We investigate the representation of action-state values in the basal ganglia.

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Value representation is enhanced in the GPe under reduced dopaminergic drive.

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Value representation is enhanced in the SNr under basal dopaminergic drive.

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The results validate a proposed neural model of the basal ganglia.

Computational Neuropsychology and Bayesian Inference

Computational theories of brain function have become very influential in neuroscience. They have facilitated the growth of formal approaches to disease, particularly in psychiatric research. In this paper, we provide a narrative review of the body of computational research addressing neuropsychological syndromes, and focus on those that employ Bayesian frameworks. Bayesian approaches to understanding brain function formulate perception and action as inferential processes. These inferences combine ‘prior’ beliefs with a generative (predictive) model to explain the causes of sensations. Under this view, neuropsychological deficits can be thought of as false inferences that arise due to aberrant prior beliefs (that are poor fits to the real world). This draws upon the notion of a Bayes optimal pathology – optimal inference with suboptimal priors – and provides a means for computational phenotyping. In principle, any given neuropsychological disorder could be characterized by the set of prior beliefs that would make a patient’s behavior appear Bayes optimal. We start with an overview of some key theoretical constructs and use these to motivate a form of computational neuropsychology that relates anatomical structures in the brain to the computations they perform. Throughout, we draw upon computational accounts of neuropsychological syndromes. These are selected to emphasize the key features of a Bayesian approach, and the possible types of pathological prior that may be present. They range from visual neglect through hallucinations to autism. Through these illustrative examples, we review the use of Bayesian approaches to understand the link between biology and computation that is at the heart of neuropsychology.

Effectiveness of Rotigotine plus intensive and goal-based rehabilitation versus Rotigotine alone in "de-novo" Parkinsonian subjects: a randomized controlled trial with 18-month follow-up

Background

Dopamine Replacement Therapy (DRT) represents the most effective treatment for Parkinson’s disease (PD). Nevertheless, several symptoms are unresponsive to treatment and its long-term use leads to serious side effects. To optimize the pharmacological management of PD, dopamine-agonists are often prescribed to “de-novo” patients. Moreover, several studies have shown the effectiveness and the synergic effect of rehabilitation in treating PD.

Objective

To evaluate the synergism between DRT and rehabilitation in treating PD, by investigating the short and the long-term effectiveness of a multidisciplinary, intensive and goal-based rehabilitation treatment (MIRT) in a group of patients treated with Rotigotine.

Materials and methods

In this multicenter, single blinded, parallel-group, 1:1 allocation ratio, randomized, non-inferiority trial, 36 “de-novo” PD patients were evaluated along 18 months: 17 were treated with Rotigotine plus MIRT; 19 were treated with Rotigotine alone (R). The primary outcome measure was the total score of Unified Parkinson’s Disease Rating Scale (UPDRS). The secondary outcomes included the UPDRS sub-sections II and III (UPDRS II-III), the 6-Minute Walk Test (6MWT), the Timed Up and Go Test (TUG) and the amount of Rotigotine. Patients were evaluated at baseline (T0), 6 months (T1), 1 year (T2), and at 18 months (T3).

Results

No differences in UPDRS scores in the two groups (total score, III part and II part, p = 0.48, p = 0.90 and p = 0.40, respectively) were found in the time course. Conversely, a greater improvement in Rotigotine + MIRT group was observed for 6MWT (p < 0.0001) and TUG (p = 0.03). Along time, the dosage of Rotigotine was higher in patients who did not undergo MIRT, at all observation times following T0.

Conclusions

Over the course of 18 months, the effectiveness of the combined treatment (Rotigotine + MIRT) on the patients’ global clinical status, evaluated with total UPDRS, was not inferior to that of the pharmacological treatment with Rotigotine alone. Importantly, rehabilitation allowed patients to gain better motor performances with lower DRT dosage.

Perceptual Surprise Improves Action Stopping by Nonselectively Suppressing Motor Activity via a Neural Mechanism for Motor Inhibition

Motor inhibition is a cognitive control ability that allows humans to stop actions rapidly even after initiation. Understanding and improving motor inhibition could benefit adaptive behavior in both health and disease. We recently found that presenting surprising, task-unrelated sounds when stopping is necessary improves the likelihood of successful stopping. In the current study, we investigated the neural underpinnings of this effect. Specifically, we tested whether surprise-related stopping improvements are due to a genuine increase in motor inhibition. In Experiment 1, we measured motor inhibition in primary motor cortex of male and female humans by quantifying corticospinal excitability (CSE) via transcranial magnetic stimulation and electromyography during a hybrid surprise-Go/NoGo task. Consistent with prior studies of motor inhibition, successful stopping was accompanied by nonselective suppression of CSE; that is, CSE was suppressed even in task-unrelated motor effectors. Importantly, unexpected sounds significantly increased this motor-system inhibition to a degree that was directly related to behavioral improvements in stopping. In Experiment 2, we then used scalp encephalography to investigate whether unexpected sounds increase motor-inhibition-related activity in the CNS. We used an independent stop-signal localizer task to identify a well characterized frontocentral low-frequency EEG component that indexes motor inhibition. We then investigated the activity of this component in the surprise-Go/NoGo task. Consistent with Experiment 1, this signature of motor inhibition was indeed increased when NoGo signals were followed by unexpected sounds. Together, these experiments provide converging evidence suggesting that unexpected events improve motor inhibition by automatically triggering inhibitory control.SIGNIFICANCE STATEMENT The ability to stop ongoing actions rapidly allows humans to adapt their behavior flexibly and rapidly. Action stopping is important in daily life (e.g., stopping to cross the street when a car approaches) and is severely impaired in many neuropsychiatric disorders. Therefore, finding ways to improve action stopping could aid adaptive behaviors in health and disease. Our current study shows that presenting unexpected sounds in stopping situations facilitates successful stopping. This improvement is specifically due to a surprise-related increase in a neural mechanism for motor inhibition, which rapidly suppresses the excitability of the motor system after unexpected events. These findings suggest a tight interaction between the neural systems for surprise processing and motor inhibition and yield a promising avenue for future research.

Subthalamic Neural Activity Patterns Anticipate Economic Risk Decisions in Gambling

Economic decision-making is disrupted in individuals with gambling disorder, an addictive behavior observed in Parkinson's disease (PD) patients receiving dopaminergic therapy. The subthalamic nucleus (STN) is involved in the inhibition of impulsive behaviors; however, its role in impulse control disorders and addiction is still unclear. Here, we recorded STN local field potentials (LFPs) in PD patients with and without gambling disorder during an economic decision-making task. Reaction times analysis showed that for all patients, the decision whether to risk preceded task onset. We compared then for both groups the STN LFP preceding high- and low-risk economic decisions. We found that risk avoidance in gamblers correlated with larger STN LFP low-frequency (<12-Hz) fluctuations preceding task onset. In particular, the amplitude of low-frequency LFP fluctuations carried significant information about future decisions. Decisions of patients not affected by gambling disorder were instead not correlated with pretask STN LFP. Our results suggest that STN activity preceding task onset affects risk decisions by preemptively inhibiting attraction to high but unlikely rewards in favor of a long-term payoff.