Inhibitory framing in hypersexual patients with Parkinson's disease. An fMRI pilot study.

Hypersexuality in medicated patients with PD is caused by an increased influence of motivational drive areas and a decreased influence of inhibitory control areas due to dopaminergic medication. In this pilot study, we test a newly developed paradigm investigating the influence of dopaminergic medication on brain activation elicited by sexual pictures with and without inhibitory contextual framing. Twenty PD patients with and without hypersexuality were examined with fMRI either OFF or ON standardized dopaminergic medication. The paradigm consisted of a priming phase where either a neutral context or an inhibitory context was presented. This priming phase was either followed by a sexual or a neutral target. Sexual, compared to neutral pictures resulted in a BOLD activation of various brain regions implicated in sexual processing. Hypersexual PD patients showed increased activity compared to PD controls in these regions. There was no relevant effect of medication between the two groups. The inhibitory context elicited less activation in inhibition-related areas in hypersexual PD, but had no influence on the perception of sexual cues. The paradigm partially worked: reactivity of motivational brain areas to sexual cues was increased in hypersexual PD and inhibitory contextual framing lead to decreased activation of inhibitory control areas in PD. We could not find a medication effect and the length of the inhibitory stimulus was not optimal to suppress reactivity to sexual cues. Our data provide new insights into the mechanisms of hypersexuality and warrant a replication with a greater cohort and an optimized stimulus length in the future.

Discounting Behavior in Problem Gambling.

Problem gamblers discount delayed rewards more rapidly than do non-gambling controls. Understanding this impulsivity is important for developing treatment options. In this article, we seek to make two contributions: First, we ask which of the currently debated economic models of intertemporal choice (exponential versus hyperbolic versus quasi-hyperbolic) provides the best description of gamblers' discounting behavior. Second, we ask how problem gamblers differ from habitual gamblers and non-gambling controls within the most favored parametrization. Our analysis reveals that the quasi-hyperbolic discounting model is strongly favored over the other two parametrizations. Within the quasi-hyperbolic discounting model, problem gamblers have both a significantly stronger present bias and a smaller long-run discount factor, which suggests that gamblers' impulsivity has two distinct sources.

Oscillatory brain activity associated with skin conductance responses in the context of risk.

Understanding the neural correlates of risk-sensitive skin conductance responses can provide insights into their connection to emotional and cognitive processes. To provide insights into this connection, we studied the cortical correlates of risk-sensitive skin conductance peaks using electroencephalography. Fluctuations in skin conductance responses were elicited while participants played a threat-of-shock card game. Precise temporal information about skin conductance peaks was obtained by applying continuous decomposition analysis on raw electrodermal signals. Shortly preceding skin conductance peaks, we observed a decrease in oscillatory power in the frequency range between 3 and 17 Hz in occipitotemporal cortical areas. Atlas-based analysis indicated the left lingual gyrus as the source of the power decrease. The oscillatory power averaged across 3-17 Hz showed a significant negative relationship with the skin conductance peak amplitude. Our findings indicate a possible interaction between attention and threat perception.NEW & NOTEWORTHY We studied neural oscillations associated with risk-sensitive skin conductance responses. Going beyond previous studies, we applied methods with high-temporal resolution to account for the temporal properties of the sympathetic activity. Preceding skin conductance peaks, we observed decreased occipital cortex oscillatory power and a relationship between the oscillatory power decrease and the skin conductance peak amplitude. Our study suggests an interaction between attention and emotion such as threat perception reflected in skin conductance responses.

MRI in patients with implanted active devices: how to combine safety and image quality using a limited transmission field?

OBJECTIVES: Radio frequency (RF) pulses in magnetic resonance imaging (MRI) can interact with implanted devices and cause tissue damage. However, there are new devices that can safely perform measurements with liberal MRI conditions such as an RF transmission field B1+rms ≤ 2.0 µT. We investigated whether MRI in this case is limited for these technical reasons. METHODS: We selected typical MRI protocols of six body regions (brain, cervical spine, lumbar spine, knee, liver, heart) using two typical 1.5T MRI scanners. Overall, we adapted 62 sequences to B1+rms conditions and evaluated their diagnostic quality. For this, we measured signal-to-noise-ratio (SNR), contrast-to-noise-ratio (CNR), and geometric deviation (GD) as quality parameters, using phantom studies. For questionnaire studies, we selected pairs of original and adapted sequences in healthy volunteers. Blinded radiologists rated the images as single sequence rating and in direct comparison. RESULTS: Roughly one-third of the checked sequences were below the B1+rms limit. Here, 56 of the 62 adapted sequences showed at least the same image quality in single ratings. A reduction in SNR and/or CNR was found with 31 sequences and only one sequence with considerably increased GD. Especially, sequences with original high B1+rms values, PD sequences, and sequences of the Siemens knee and heart protocol were difficult to adapt, whereas most TSE and IR sequences had no clinical limitations. CONCLUSION: By limiting the transmission field to B1+rms ≤ 2.0 µT, clinically relevant MR sequences can be adapted with nearly no reduction in image quality. Despite limiting the transmission field, high-quality MR imaging is possible. We could derive strategies for adaptation. KEY POINTS: • Despite limiting the transmission field, high-quality MRI is possible. • We could derive strategies for adapting the sequences to B1+rms≤ 2.0 µT. • This enables high-quality MRI of different body regions for patients with AD.

Reduced olfactory bulb volume in depression-A structural moderator analysis.

BACKGROUND: Removal of the olfactory bulb (OB) leads to depression like behavior in rodents. A link between depression and olfactory function is also established in humans. We hypothesized that the human OB volume relates to depressive state and tested whether such a potential coherence is moderated by structural alterations in other brain regions. METHODS: Eighty-three participants (32 patients with major depression and 51 matched healthy controls) underwent structural MR scanning. Individual OB volumes were compared between patients and controls and the impact of depression and comorbidity was analyzed with multiple regression analysis. Whole-brain voxel-based morphometry revealed structures co-varying with both depressive state and OB volume. RESULTS: The OB volume of patients was significantly reduced and this reduction averaged out at 17% compared to the controls. The OB volume was correlated to the volume of the insula, superior temporal cortex, and amygdala. The independent variables of depression (ß = -.37), age (ß = -.25), and gender (ß = -.40) explained the individual OB volume variation (R2 = .37). The correlation between OB volume and depression was moderated by volumetric reductions in a cluster including the insula and superior temporal gyrus (STG). CONCLUSIONS: The OB volume relates to depression in humans and to the volume of structures which are critical for salience detection. We assume that a reduced OB volume causes diminished neural olfactory input which facilitates volume reduction in the insula and STG. The OB volume may hence constitute a factor of vulnerability to depression. Olfactory-based deep brain stimulation is discussed as a future therapeutic approach.

Abnormal functional global and local brain connectivity in female patients with anorexia nervosa.

BACKGROUND: Previous resting-state functional connectivity studies in patients with anorexia nervosa used independent component analysis or seed-based connectivity analysis to probe specific brain networks. Instead, modelling the entire brain as a complex network allows determination of graph-theoretical metrics, which describe global and local properties of how brain networks are organized and how they interact. METHODS: To determine differences in network properties between female patients with acute anorexia nervosa and pairwise matched healthy controls, we used resting-state fMRI and computed well-established global and local graph metrics across a range of network densities. RESULTS: Our analyses included 35 patients and 35 controls. We found that the global functional network structure in patients with anorexia nervosa is characterized by increases in both characteristic path length (longer average routes between nodes) and assortativity (more nodes with a similar connectedness link together). Accordingly, we found locally decreased connectivity strength and increased path length in the posterior insula and thalamus. LIMITATIONS: The present results may be limited to the methods applied during preprocessing and network construction. CONCLUSION: We demonstrated anorexia nervosa-related changes in the network configuration for, to our knowledge, the first time using resting-state fMRI and graph-theoretical measures. Our findings revealed an altered global brain network architecture accompanied by local degradations indicating wide-scale disturbance in information flow across brain networks in patients with acute anorexia nervosa. Reduced local network efficiency in the thalamus and posterior insula may reflect a mechanism that helps explain the impaired integration of visuospatial and homeostatic signals in patients with this disorder, which is thought to be linked to abnormal representations of body size and hunger.

Spinal and supraspinal processing of thermal stimuli: an fMRI study.

PURPOSE: To assess and characterize responses to innocuous/noxious thermal stimuli and heat allodynia using functional spinal magnetic resonance imaging (spinal fMRI). MATERIALS AND METHODS: Spinal/supraspinal activation patterns of 16 healthy subjects were investigated by applying painful and nonpainful heat stimuli to dermatome C6 baseline and after sensitization with the heat/capsaicin model using fMRI (3T, single-shot TSE, TR 9000 msec, TE 38 msec, FOV 288 × 144 × 20 mm, matrix 192 × 96, voxel size 1 × 1 × 2 mm). RESULTS: Increased activity was observed in ipsi- and contralateral ventral and dorsal spinal horn during noxious heat and heat allodynia. During noxious heat, but not during heat allodynia, activations were visible in the periaqueductal gray, ipsilateral cuneiform nucleus, and ipsilateral dorsolateral pontine tegmentum (DLPT). However, during heat allodynia activations were observed in bilateral ruber nuclei, contralateral DLPT, and rostral ventromedial medulla oblongata (RVM). Activations in contralateral subnucleus reticularis dorsalis (SRD) were visible during both noxious heat and heat allodynia (T >2.5, P < 0.01 for all of the above). After sensitization, activations in RVM and SRD correlated with activations in the ipsilateral dorsal horn of the spinal cord (R = 0.52-0.98, P < 0.05). CONCLUSION: Spinal fMRI successfully demonstrates increased spinal activity and secondary changes in activation of supraspinal centers involved in pain modulation caused by peripheral nociceptor sensitization. J. Magn. Reson. Imaging 2015;41:1046-1055. © 2014 Wiley Periodicals, Inc.

Variability of EEG-fMRI findings in patients with SCN1A-positive Dravet syndrome.

PURPOSE: Dravet syndrome (DS) or severe myoclonic epilepsy of infancy is an intractable epileptic encephalopathy of early childhood that is caused by a mutation in the SCN1A gene in most patients. The aim of this study was to identify a syndrome-specific epileptic network underlying interictal epileptiform discharges (IEDs) in patients with DS. METHODS: Ten patients with the diagnosis of DS associated with mutations in the SCN1A gene were investigated using simultaneous recording of electroencephalography and functional magnetic resonance imaging ((EEG-fMRI). Time series of IEDs were used as regressors for the statistical fMRI analysis. KEY FINDINGS: In nine patients with DS, individual blood oxygenation level-dependent (BOLD) signal changes were seen. In three patients the thalamus was involved. Furthermore, regions of the default mode network were activated in seven patients. However, a common activation pattern associated with IEDs could not be detected. SIGNIFICANCE: The study demonstrates that, despite a common genetic etiology in DS, different neuronal networks underlie the individual IEDs.

EEG-fMRI in atypical benign partial epilepsy.

Atypical benign partial epilepsy (ABPE) is a subgroup among the idiopathic focal epilepsies of childhood. Aim of this study was to investigate neuronal networks underlying ABPE and compare the results with previous electroencephalography (EEG)-functional magnetic resonance imaging (fMRI) studies of related epilepsy syndromes. Ten patients with ABPE underwent simultaneous EEG-fMRI recording. In all 10 patients several types of interictal epileptiform discharges (IEDs) were recorded. Individual IED-associated blood oxygen level-dependent (BOLD) signal changes were analyzed in a single subject analysis for each IED type (33 studies). A group analysis was also performed to determine common BOLD signal changes across the patients. IED-associated BOLD signal changes were found in 31 studies. Focal BOLD signal changes concordant with the spike field (21 studies) and distant cortical and subcortical BOLD signal changes (31 studies) were detected. The group analysis revealed a thalamic activation. This study demonstrated that ABPE is characterized by patterns similar to studies in rolandic epilepsy (focal BOLD signal changes in the spike field) as well as patterns observed in continuous spikes and waves during slow sleep (CSWS) (distant BOLD signal changes in cortical and subcortical structures), thereby underscoring that idiopathic focal epilepsies of childhood form a spectrum of overlapping syndromes.

Abnormal changes of synaptic excitability in migraine with aura.

Migraine patients are characterized by altered cortical excitability and information processing between attacks. The relationship between these abnormalities is still poorly understood. In this study, visual evoked potentials (VEP) and proton magnetic resonance spectroscopy were recorded simultaneously in migraineurs and healthy subjects. In order to investigate the homeostatic-like plasticity in the visual cortex, cortical excitability was modified using transcranial direct current stimulation (tDCS). Before any stimulation, migraineurs showed significantly higher glutamate/creatine ratios (Glx/Cr) than healthy subjects. In healthy subjects, excitatory (anodal) tDCS caused an increase and inhibitory (cathodal) tDCS a decrease in the Glx/Cr ratio. Subsequent photic stimulation (PS) reversed the changes in Glx/Cr ratios, which returned back to baseline, demonstrating homeostatic-like metaplasticity in the control group. In migraine patients, both anodal and cathodal tDCS decreased the Glx/Cr ratio, which did not return to baseline after PS. While healthy subjects showed an increase in VEP amplitude under anodal and a reduction under cathodal tDCS, the modifiability of VEP under tDCS was reduced in migraineurs. The results demonstrate a reduced responsiveness of the occipital cortex to interventions that change cortical excitability in migraine. Moreover, altered glutamatergic neurotransmission seems to mediate the relation between abnormal cortical information processing and excitability in migraineurs.

Simultaneous EMG-fMRI during startle inhibition in monosymptomatic enuresis--an exploratory study.

Evidence is growing that monosymptomatic enuresis (ME) is a maturational disorder of the central nervous system with a lack of arousal and lacking inhibition of the micturition reflex. Previous studies have shown a significant reduction of prepulse inhibition (PPI) of startle in children with enuresis. However, it is still unclear whether the abnormal PPI in enuresis is based on an inhibitory deficit at brainstem or cortical level. Nine children with ME and ten healthy children were investigated using simultaneous recording of EMG from the M. orbicularis oculi and functional MRI. The experimental paradigm consisted of acoustic startle stimulation, with startle-alone stimuli and prepulse-startle combinations. Functional MRI data were processed using multiple regression and parametric modulation with startle amplitudes as a parameter. Neither patients with enuresis nor healthy children revealed measurable PPI in the MRI scanner. Startle stimuli caused equal hemodynamic changes in the acoustic cortex, medial prefrontal and orbitofrontal cortex in both groups. The amplitude of startle correlated with more prominent BOLD signal changes in the anterior cingulate cortex in healthy subjects than in patients with ME. This pronounced frontal activation in healthy controls was related to the PPI condition, indicating that the prefrontal cortex of healthy children was activated more strongly to inhibit startle than in patients with ME. In conclusion, apart from the possibility that recordings of PPI inside the MRI scanner may be compromised by methodological problems, the results of this study suggest that high cortical control mechanisms at the prefrontal level are relevant for the pathogenesis of ME.

White matter microstructural changes of thalamocortical networks in photosensitivity and idiopathic generalized epilepsy.

PURPOSE: Photosensitivity or photoparoxysmal response (PPR) is an electroencephalography trait that is highly associated with idiopathic generalized epilepsies (IGEs) and characterized by changes in cortical excitability in response to photic stimulation. Studying functional and structural changes of PPR might provide important insights into the pathogenesis of IGE. Recent studies revealed a functional network consisting of occipital, parietal, and precentral areas that might be implicated in PPR. Herein, we investigate the microstructural changes associated with PPR. METHODS: Twelve healthy subjects with PPR, nine patients with IGE and PPR (IGE-PPR group), and 18 healthy controls were studied with diffusion magnetic resonance imaging. Tract-based spatial statistics were used to test for regional differences in fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity, and radial diffusivity between groups. KEY FINDINGS: Subjects with PPR exhibited higher FA in the right precentral juxtacortical white matter and higher MD in lateral occipital areas relative to controls. Patients with IGE-patients showed additional increases in regional FA in the thalamus and juxtacortical precentral and parietal areas. Both subjects with PPR and patients with IGE-PPR presented axial and radial diffusivity changes in the occipital regions. SIGNIFICANCE: Our results show that PPR is associated with subcortical microstructural changes in precentral, parietal, and occipital regions. The coexistence of PPR and IGE is associated with white matter abnormalities in the thalamus and precuneus. PPR and epilepsy share similar functional and structural networks in widespread cortical and subcortical areas.

The value of EEG-fMRI and EEG source analysis in the presurgical setup of children with refractory focal epilepsy.

PURPOSE: In the presurgical evaluation of children and juvenile patients with refractory focal epilepsy, the main challenge is to localize the point of seizure onset as precisely as possible. We compared results of the conventional electroencephalography-functional magnetic resonance imaging (EEG-fMRI) analysis with those obtained with a newly developed method using voltage maps of average interictal epileptiform discharges (IEDs) recorded during clinical long-term monitoring and with the results of the electric source imaging (ESI). METHODS: Simultaneous EEG-fMRI was recorded in nine patients (ages 1.5-17.5 years) undergoing presurgical evaluation. The postoperative outcome and resected area were compared with the following: the localizations of blood oxygen-level dependent (BOLD) signal changes associated with IEDs, which were identified by visual inspection changes using SPM5 software (Analysis I); BOLD signal changes related to IED topography, which was characterized using spike-specific voltage maps of average IED recorded outside the MR scanner during clinical long-term monitoring (Analysis II); as well as results of EEG source analysis based on the distributed linear local autoregressive average (LAURA) algorithm using the Cartool software by Denis Brunet (Analysis III). KEY FINDINGS: All nine patients had postoperative outcome Engel class I-IIb (postoperative time 6-26 months). The analysis I revealed an IED-related area of activation within the resection area in 3 (33%) of 9 patients, analysis II was able to reliably localize the source of epileptic activity in 4 (44%) of 9 patients, and analysis III rendered results concordant with the postoperative resection site in all nine patients. CONCLUSIONS: The localization of seizure onset based on EEG-fMRI may be a useful adjunct in the preoperative evaluation but also has some deficits that impair the reliability of results. In contrast, EEG source analysis is clearly a more credible method for epileptic focus localization in children with refractory epilepsies. It seems likely that the analysis based on IED topography (Analysis II) may increase sensitivity and reliability of EEG-fMRI in some patients. However, the benefit from this innovative method in children is rather limited compared with adults.

Behavioural treatment increases activity in the cognitive neuronal networks in children with attention deficit/hyperactivity disorder.

Response cost and token approach (RCT) within the scope of a summer camp training is an effective treatment program for attention deficit hyperactivity disorder (ADHD). It is likely that intensive RCT training influences networks responsible for ADHD symptoms. Functional magnetic resonance imaging (fMRI) was carried out in 12 children with ADHD before and after the RCT program and in 12 healthy control children twice. For fMRI, a Go/No-go paradigm was used to investigate the influence of RCT training on attention and impulsivity. The No-go condition revealed only weak activation in the dorsal part of the anterior cingulate cortex (ACC), parietal and dorsolateral prefrontal cortex (DLPFC) before the training in children with ADHD compared to healthy children. However, this activation in these brain regions was significantly more pronounced after the training. This increase in hemodynamic response cannot be attributed merely to repetition of the measurement since the effect was not observed in healthy children. The increase in hemodynamic response in the ACC and right DLPFC was significantly associated with a reduction in response time variability and clinical symptoms in ADHD patients. After the RCT training, the children with ADHD demonstrated more pronounced activation of cortical structures which are typically related to response monitoring and self-control. It seems likely that children with ADHD learned more cognitive control in a continuous performance task as was revealed by both neuropsychological outcome and fMRI.

Neural Correlates of Executed Compared to Imagined Writing and Drawing Movements: A Functional Magnetic Resonance Imaging Study.

Objective: In this study we used functional magnetic resonance imaging (fMRI) to investigate whether motor imagery (MI) of handwriting and circle drawing activates a similar handwriting network as writing and drawing itself. Methods: Eighteen healthy right-handed participants wrote the German word "Wellen" and drew continuously circles in a sitting (vertical position) and lying position (horizontal position) to capture kinematic handwriting parameters such as velocity, pressure and regularity of hand movements. Afterward, they performed the same tasks during fMRI in a MI and an executed condition. Results: The kinematic analysis revealed a general correlation of handwriting parameters during sitting and lying except of pen pressure during drawing. Writing compared to imagined writing was accompanied by an increased activity of the ipsilateral cerebellum and the contralateral sensorimotor cortex. Executed compared to imagined drawing revealed elevated activity of a fronto-parieto-temporal network. By contrasting writing and drawing directly, executed writing induced an enhanced activation of the left somatosensory and premotor area. The comparison of the MI of these tasks revealed a higher involvement of occipital activation during imagined writing. Conclusion: The kinematic results pointed to a high comparability of writing in a vertical and horizontal position. Overall, we observed highly overlapping cortical activity except of a higher involvement of motor control areas during motor execution. The sparse difference between writing and drawing can be explained by highly automatized writing in healthy individuals.

White Matter Hyperintensities Are Associated With Severity of Essential Tremor in the Elderly.

Background: Essential tremor (ET) occurs with steeply increasing prevalence in the elderly, and apart from disease duration, age is independently associated with an increase of tremor amplitude and a decrease of frequency. White matter hyperintensities (WMHs) are a common finding in the elderly, and their role in the pathophysiology of ET is unknown. The aims of this study were to examine whether ET patients differ in their total or region-specific WMH volumes from healthy controls and to determine the impact of WMH on tremor characteristics. Methods: A total of 47 elderly ET patients with a mean age of 72 years and 39 age-matched healthy controls underwent a thorough clinical assessment and 3T MRI. Total WMH volumes were derived from T2-weighted fluid-attenuated inversion recovery (FLAIR) MR images. Additionally, region of interest-based WMH volumes for the Johns Hopkins University (JHU) white matter tracts and labels were calculated, and WMHs were assessed semiquantitatively using the Fazekas scale. Results: Essential tremor patients and healthy controls did not differ in their total or tract-specific WMH volumes or Fazekas scores. However, WMH volume was significantly positively correlated with tremor severity on the TETRAS scale, and there was a significant negative correlation with the mean accelerometric tremor frequency. In a multiple linear regression model including disease duration, age, and age-adjusted total WMH volume, only the WMH volume significantly predicted tremor severity, while age and disease duration were not significant. Conclusion: We found evidence for a direct association between WMH volume and tremor severity. If confirmed by larger studies, our findings could explain the well-known relation between age and tremor severity.

Abnormal effective connectivity in the sensory network in writer's cramp.

BACKGROUND: Writer's cramp (WC), a task specific form of dystonia, is considered to be a motor network disorder, but abnormal sensory tactile processing has also been acknowledged. The sensory spatial discrimination threshold (SDT) can be determined with a spatial acuity test (JVP domes). In addition to increased SDT, patients with WC exhibited dysfunctional sensory processing in the sensory cortex, insula, basal ganglia and cerebellum in a functional magnetic resonance imaging (fMRI) study while performing the spatial acuity test. OBJECTIVES: To assess whether effective connectivity (EC) in the sensory network including cortical, basal ganglia, thalamic and cerebellar regions of interest in WC patients is abnormal. METHODS: We used fMRI and applied a block design, while 19 WC patients and 13 age-matched healthy controls performed a spatial discrimination task. Before we assessed EC using dynamic causal modelling, we compared three model structures based on the current literature. We enclosed regions of interest that are established for sensory processing during right hand stimulation: Left thalamus, somatosensory, parietal and insular cortex, posterior putamen, and right cerebellum. RESULTS: The EC analysis revealed task-dependent decreased unidirectional connectivity between the insula and the posterior putamen. The connectivity involving the primary sensory cortex, parietal cortex and cerebellum were not abnormal in WC. The two groups showed no differences in their behavioural data. CONCLUSIONS: Perception and integration of sensory information requires the exchange of information between the insula cortex and the putamen, a sensory process that was disturbed in WC patients.

Never too little: Grip and lift forces following probabilistic weight cues in patients with writer's cramp.

OBJECTIVE: Planning of voluntary object-related movements requires the estimation of the most probable object properties. We investigated how 14 writer's cramp (WC) patients compared to 14 controls use probabilistic weight cues in a serial grip-lift task. METHODS: In every grip-lift trial, an object of either light, medium or heavy weight had to be grasped and lifted after a visual cue gave a probabilistic prediction of the object weights (e.g. 32.5% light, 67.5% medium, 0 % heavy). We determined peak (1) grip force GF, (2) load force LF, (3) grip force rate GFR, (4) load force rate LFR, while we registered brain activity with functional magnetic resonance imaging. RESULTS: In both groups, GFR, LFR and GF increased when a higher probability of heavy weights was announced. When a higher probability of light weights was indicated, controls reduced GFR, LFR and GF, while WC patients did not downscale their forces. There were no inter-group differences in blood oxygenation level dependent activation. CONCLUSIONS: WC patients could not utilize the decision range in motor planning and adjust their force in a probabilistic cued fine motor task. SIGNIFICANCE: The results support the pathophysiological model of a hyperfunctional dopamine dependent direct basal ganglia pathway in WC.

EEG-fMRI study of generalized spike and wave discharges without transitory cognitive impairment.

Generalized spike and wave discharges (GSW) are often accompanied by transitory cognitive impairment (TCI). As a possible neurophysiological correlate of TCI, activation in the thalamus and deactivation in the frontoparietal brain regions associated with GSW were discussed in previous studies which used simultaneous recordings of EEG and functional MRI (EEG-fMRI) in patients with absence epilepsy. We report on a girl having GSW up to 10seconds without any clinical concomitants. The girl underwent an EEG-fMRI investigation with simultaneous behavioral testing (continuous performance task). Although GSW repeatedly occurred during the task, no TCI was observed. EEG-fMRI revealed bilateral deactivation in frontoparietal brain areas and activation in the thalamus in association with GSWs. This study challenges the relation between cognitive impairment during absences and the characteristic pattern of thalamic activation and deactivation in frontoparietal areas associated with GSW.

Optimal HRF and smoothing parameters for fMRI time series within an autoregressive modeling framework.

The analysis of time series obtained by functional magnetic resonance imaging (fMRI) may be approached by fitting predictive parametric models, such as nearest-neighbor autoregressive models with exogeneous input (NNARX). As a part of the modeling procedure, it is possible to apply instantaneous linear transformations to the data. Spatial smoothing, a common preprocessing step, may be interpreted as such a transformation. The autoregressive parameters may be constrained, such that they provide a response behavior that corresponds to the canonical haemodynamic response function (HRF). We present an algorithm for estimating the parameters of the linear transformations and of the HRF within a rigorous maximum-likelihood framework. Using this approach, an optimal amount of both the spatial smoothing and the HRF can be estimated simultaneously for a given fMRI data set. An example from a motor-task experiment is discussed. It is found that, for this data set, weak, but non-zero, spatial smoothing is optimal. Furthermore, it is demonstrated that activated regions can be estimated within the maximum-likelihood framework.