Role of the cerebellum in motor cognition

Effects of Spontaneous Neural Activity during Learning Football Juggling—A Randomized Control Trial

To establish the characteristics of spontaneous neural activity during learning football juggling. We used fMRI to see which parts of the brain were changed by learning football juggling. Through recruitment, 111 college students (37 females and 74 males) were selected and randomly divided into football juggling (FJ) (n = 68, 23 females and 45 males) and a control group (CON) (n = 43, 14 females and 29 males). The FJ group learned football juggling 70 times, while CON had regular study sessions at the same time. Static functional magnetic resonance imaging (fMRI) was used to measure the dynamic changes of spontaneous nerve activity during learning football juggling. The result shows that the ALFF value in the right cerebellum 8 area was significantly higher than that before the 70 times of learning football juggling. The present study provides initial evidence that learning football juggling 70 times effectively increased the level of spontaneous neural activity in the cerebellum region. These promising findings provide new evidence to fully reveal the relationship between motion learning and brain plasticity.

Tutorial Review of Bio-Inspired Approaches to Robotic Manipulation for Space Debris Salvage

We present a comprehensive tutorial review that explores the application of bio-inspired approaches to robot control systems for grappling and manipulating a wide range of space debris targets. Current robot manipulator control systems exploit limited techniques which can be supplemented by additional bio-inspired methods to provide a robust suite of robot manipulation technologies. In doing so, we review bio-inspired control methods because this will be the key to enabling such capabilities. In particular, force feedback control may be supplemented with predictive forward models and software emulation of viscoelastic preflexive joint behaviour. This models human manipulation capabilities as implemented by the cerebellum and muscles/joints respectively. In effect, we are proposing a three-level control strategy based on biomimetic forward models for predictive estimation, traditional feedback control and biomimetic muscle-like preflexes. We place emphasis on bio-inspired forward modelling suggesting that all roads lead to this solution for robust and adaptive manipulator control. This promises robust and adaptive manipulation for complex tasks in salvaging space debris.

Trade-off of cerebello-cortical and cortico-cortical functional networks for planning in 6-year-old children

Childhood is a critical period for the development of cognitive planning. There is a lack of knowledge on its neural mechanisms in children. This study aimed to examine cerebello-cortical and cortico-cortical functional connectivity in association with planning skills in 6-year-olds (n = 76). We identified the cerebello-cortical and cortico-cortical functional networks related to cognitive planning using activation likelihood estimation (ALE) meta-analysis on existing functional imaging studies on spatial planning, and data-driven independent component analysis (ICA) of children's resting-state functional MRI (rs-fMRI). We investigated associations of cerebello-cortical and cortico-cortical functional connectivity with planning ability in 6-year-olds, as assessed using the Stockings of Cambridge task. Long-range functional connectivity of two cerebellar networks (lobules VI and lateral VIIa) with the prefrontal and premotor cortex were greater in children with poorer planning ability. In contrast, cortico-cortical association networks were not associated with the performance of planning in children. These results highlighted the key contribution of the lateral cerebello-frontal functional connectivity, but not cortico-cortical association functional connectivity, for planning ability in 6-year-olds. Our results suggested that brain adaptation to the acquisition of planning ability during childhood is partially achieved through the engagement of the cerebello-cortical functional connectivity.

Cerebellum-from J. E. Purkyně up to Contemporary Research

Jan. Evangelista Purkyně, the most famous among Czech physiologists, was the first who identified and described the largest nerve cells in the cerebellum. The most distinguished researchers of the nervous system then recommended naming these neurons Purkinje cells in his honor. Through experiments by Purkinje and his followers, the function of the cerebellum was properly attributed to the precision of motor movements and skills. This traditional concept was valid until early 1990s, when it was readjusted and replenished with new and important findings. It was discovered that the cerebellar cortex contains more neurons than the cerebral cortex and shortly thereafter was gradually revealed that such enormous numbers of neural cells are not without impact on brain functions. It was shown that the cerebellum, in addition to its traditional role, also participates in higher nervous activity. These new findings were obtained thanks to the introduction of modern methods of examination into the clinical praxis, and experimental procedures using animal models of cerebellar disorders described in this work.

Cerebellar damage impairs executive control and monitoring of movement generation

Executive control of motor responses is a psychological construct of the executive system. Several studies have demonstrated the involvement of the cerebral cortex, basal ganglia, and thalamus in the inhibition of actions and monitoring of performance. The involvement of the cerebellum in cognitive function and its functional interaction with basal ganglia have recently been reported. Based on these findings, we examined the hypothesis of cerebellar involvement in executive control by administering a countermanding task in patients with focal cerebellar damage. The countermanding task requires one to make a movement in response to a 'go' signal and to halt it when a 'stop' signal is presented. The duration of the go process (reaction time; RT), the duration of the stop process (stop signal reaction time; SSRT), and their relationship, expressed by a psychometric function, are recorded as measures of executive control. All patients had longer go process duration in general and in particular, as a proactive control, as demonstrated by the increase in RT after erroneously performed stop trials. Further, they were defective in the slope of the psychometric function indicating a difficulty on triggering the stop process, although the SSRT did not differ from controls. Notably, their performance was worse when lesions affected deep cerebellar nuclei. Our results support the hypothesis that the cerebellum regulates the executive control of voluntary actions. We speculate that its activity is attributed to specific cerebellar influence over the cortico-striatal loop.

Patterned-string tasks: relation between fine motor skills and visual-spatial abilities in parrots

String-pulling and patterned-string tasks are often used to analyse perceptual and cognitive abilities in animals. In addition, the paradigm can be used to test the interrelation between visual-spatial and motor performance. Two Australian parrot species, the galah (Eolophus roseicapilla) and the cockatiel (Nymphicus hollandicus), forage on the ground, but only the galah uses its feet to manipulate food. I used a set of string pulling and patterned-string tasks to test whether usage of the feet during foraging is a prerequisite for solving the vertical string pulling problem. Indeed, the two species used techniques that clearly differed in the extent of beak-foot coordination but did not differ in terms of their success in solving the string pulling task. However, when the visual-spatial skills of the subjects were tested, the galahs outperformed the cockatiels. This supports the hypothesis that the fine motor skills needed for advanced beak-foot coordination may be interrelated with certain visual-spatial abilities needed for solving patterned-string tasks. This pattern was also found within each of the two species on the individual level: higher motor abilities positively correlated with performance in patterned-string tasks. This is the first evidence of an interrelation between visual-spatial and motor abilities in non-mammalian animals.

Spatiotemporal neural interactions underlying continuous drawing movements as revealed by magnetoencephalography

Continuous and sequential movements are controlled by widely distributed brain regions. A series of studies have contributed to understanding the functional role of these regions in a variety of visuomotor tasks. However, little is known about the neural interactions underpinning continuous movements. In the current study, we examine the spatiotemporal neural interactions underlying continuous drawing movements and the association of them with behavioral components. We conducted an experiment in which subjects copied a pentagon continuously for ~45 s using an XY joystick, while neuromagnetic fluxes were recorded from their head using a 248-sensor whole-head magnetoencephalography (MEG) device. Each sensor time series was rendered stationary and non-autocorrelated by applying an autoregressive integrated moving average model and taking the residuals. We used the directional variability of the movement as a behavioral measure of the controls generated. The main objective of this study was to assess the relation between neural interactions and the variability of movement direction. That is, we divided the continuous recordings into consecutive periods (i.e., time-bins) of 51 steps duration and computed the pairwise cross-correlations between the prewhitened time series in each time-bin. The circular standard deviation of the movement direction within each time-bin provides an estimate of the directional variability of the 51-ms trajectory segment. We looked at the association between neural interactions and variability of movement direction, separately for each pair of sensors, by running a cross-correlation analysis between the strength of the MEG pairwise cross-correlations and the circular standard deviations. We identified two types of neuronal networks: in one, the neural interactions are correlated with the directional variability of the movement at negative time-lags (feedforward), and in the other, the neural interactions are correlated with the directional variability of the movement at positive time-lags (feedback). Sensors associated mostly with feedforward processes are distributed in the left hemisphere and the right occipital-temporal junction, whereas sensors related to feedback processes are distributed in the right hemisphere and the left cerebellar hemisphere. These results are in line with findings from a series of previous studies showing that specific brain regions are involved in feedforward and feedback control processes to plan, perform, and correct movements. Additionally, we looked at whether changes in movement direction modulate the neural interactions. Interestingly, we found a preponderance of sensors associated with changes in movement direction over the right hemisphere-ipsilateral to the moving hand. These sensors exhibit stronger coupling with the rest of the sensors for trajectory segments with high rather than low directional movement variability. We interpret these results as evidence that ipsilateral cortical regions are recruited for continuous movements when the curvature of the trajectory increases. To the best of our knowledge, this is the first study that shows how neural interactions are associated with a behavioral control parameter in continuous and sequential movements.

Greater disruption to control of voluntary saccades in autistic disorder than Asperger's disorder: evidence for greater cerebellar involvement in autism?

It remains unclear whether autism and Asperger's disorder (AD) exist on a symptom continuum or are separate disorders with discrete neurobiological underpinnings. In addition to impairments in communication and social cognition, motor deficits constitute a significant clinical feature in both disorders. It has been suggested that motor deficits and in particular the integrity of cerebellar modulation of movement may differentiate these disorders. We used a simple volitional saccade task to comprehensively profile the integrity of voluntary ocular motor behaviour in individuals with high functioning autism (HFA) or AD, and included measures sensitive to cerebellar dysfunction. We tested three groups of age-matched young males with normal intelligence (full scale, verbal, and performance IQ estimates >70) aged between 11 and 19 years; nine with AD, eight with HFA, and ten normally developing males as the comparison group. Overall, the metrics and dynamics of the voluntary saccades produced in this task were preserved in the AD group. In contrast, the HFA group demonstrated relatively preserved mean measures of ocular motricity with cerebellar-like deficits demonstrated in increased variability on measures of response time, final eye position, and movement dynamics. These deficits were considered to be consistent with reduced cerebellar online adaptation of movement. The results support the notion that the integrity of cerebellar modulation of movement may be different in AD and HFA, suggesting potentially differential neurobiological substrates may underpin these complex disorders.

Neuroimaging in attention-deficit hyperactivity disorder: beyond the frontostriatal circuitry

OBJECTIVES

To review the findings of structural and functional neuroimaging studies in attention-deficit hyperactivity disorder (ADHD), with a focus on abnormalities reported in brain regions that lie outside the frontostriatal circuitry, which is currently believed to play a central role in the pathophysiology of ADHD.

METHODS

Relevant publications were found primarily by searching the MEDLINE and PubMed databases using the keywords ADHD and the abbreviations of magnetic resonance imaging (MRI), functional MRI, positron emission tomography, and single photon emission computed tomography. The reference lists of the articles found through the databases were then reviewed for the purpose of finding additional articles.

RESULTS

There is now substantial evidence of structural and functional alterations in regions outside the frontostriatal circuitry in ADHD, most notably in the cerebellum and the parietal lobes.

CONCLUSIONS

Although there is compelling evidence suggesting that frontostriatal dysfunction may be central to the pathophysiology of ADHD, the neuroimaging findings point to distributed neural substrates rather than a single one. More research is needed to elucidate the nature of contributions of nonfrontostriatal regions to the pathophysiology of ADHD.

The multifaceted nature of the relationship between performance and brain activity in motor sequence learning

The 'learning and performance' conundrum has for a long time puzzled the field of cognitive neuroscience. Deciphering the genuine functional neuroanatomy of motor sequence learning, among that of other skills, has thereby been hampered. The main caveat is that changes in neural activity that inherently accompany task practice may not only reflect the learning process per se, but also the basic motor implementation of improved performance. Previous research has attempted to control for a performance confound in brain activity by adopting methodologies that prevent changes in performance. However, blocking the expression of performance is likely to distort the very nature of the motor sequence learning process, and may thus represent a major confound in itself. In the present study, we postulated that both learning-dependent plasticity mechanisms and learning-independent implementation processes are nested within the relationship that exists between performance and brain activity. Functional magnetic resonance imaging (fMRI) was used to map brain responses in healthy volunteers while they either (a) learned a novel sequence, (b) produced a highly automatized sequence or (c) executed non-sequential movements matched for speed frequency. In order to dissociate between qualitatively distinct, but intertwined, relationships between performance and neural activity, our analyses focused on correlations between variations in performance and brain activity, and how this relationship differs or shares commonalities between conditions. Results revealed that activity in the putamen and contralateral lobule VI of the cerebellum most strongly correlated with performance during learning per se, suggesting their key role in this process. By contrast, activity in a parallel cerebellar network, as well as in motor and premotor cortical areas, was modulated by performance during learning and during one or both control condition(s), suggesting the primary contribution of these areas in motor implementation, either as a function or not of the sequential content of movements. Our findings thus highlight the multifaceted nature of the link between performance and brain activity, and suggest that different components of the striato-cortical and cerebello-cortical motor loops play distinct, but complementary, roles during early motor sequence learning.

Activation of the pre-supplementary motor area but not inferior prefrontal cortex in association with short stop signal reaction time--an intra-subject analysis

BACKGROUND

Our previous work described the neural processes of motor response inhibition during a stop signal task (SST). Employing the race model, we computed the stop signal reaction time (SSRT) to index individuals' ability in inhibitory control. The pre-supplementary motor area (preSMA), which shows greater activity in individuals with short as compared to those with long SSRT, plays a role in mediating response inhibition. In contrast, the right inferior prefrontal cortex (rIFC) showed greater activity during stop success as compared to stop error. Here we further pursued this functional differentiation of preSMA and rIFC on the basis of an intra-subject approach.

RESULTS

Of 65 subjects who participated in four sessions of the SST, we identified 30 individuals who showed a difference in SSRT but were identical in other aspects of stop signal performance between the first ("early") and last two ("late") sessions. By comparing regional brain activation between the two sessions, we confirmed greater preSMA but not rIFC activity during short as compared to long SSRT session within individuals. Furthermore, putamen, anterior cerebellum and middle/posterior cingulate cortex also showed greater activity in association with short SSRT.

CONCLUSION

These results are consistent with a role of medial prefrontal cortex in controlled action and inferior frontal cortex in orienting attention. We discussed these findings with respect to the process of attentional monitoring and inhibitory motor control during stop signal inhibition.

Age-related changes in the cerebral substrates of cognitive procedural learning

Cognitive procedural learning occurs in three qualitatively different phases (cognitive, associative, and autonomous). At the beginning of this process, numerous cognitive functions are involved, subtended by distinct brain structures such as the prefrontal and parietal cortex and the cerebellum. As the learning progresses, these cognitive components are gradually replaced by psychomotor abilities, reflected by the increasing involvement of the cerebellum, thalamus, and occipital regions. In elderly subjects, although cognitive studies have revealed a learning effect, performance levels differ during the acquisition of a procedure. The effects of age on the learning of a cognitive procedure have not yet been examined using functional imaging. The aim of this study was therefore to characterize the cerebral substrates involved in the learning of a cognitive procedure, comparing a group of older subjects with young controls. For this purpose, we performed a positron emission tomography activation study using the Tower of Toronto task. A direct comparison of the two groups revealed the involvement of a similar network of brain regions at the beginning of learning (cognitive phase). However, the engagement of frontal and cingulate regions persisted in the older group as learning continued, whereas it ceased in the younger controls. We assume that this additional activation in the older group during the associative and autonomous phases reflected compensatory processes and the fact that some older subjects failed to fully automate the procedure.

Cerebellar Transcranial Direct Current Stimulation Impairs the Practice-dependent Proficiency Increase in Working Memory

How the cerebellum is involved in the practice and proficiency of non-motor functions is still unclear. We tested whether transcranial direct current stimulation (tDCS) over the cerebellum (cerebellar tDCS) induces after-effects on the practice-dependent increase in the proficiency of a working memory (WM) task (Sternberg test) in 13 healthy subjects. We also assessed the effects of cerebellar tDCS on visual evoked potentials (VEPs) in four subjects and compared the effects of cerebellar tDCS on the Sternberg test with those elicited by tDCS delivered over the prefrontal cortex in five subjects. Our experiments showed that anodal or cathodal tDCS over the cerebellum impaired the practice-dependent improvement in the reaction times in a WM task. Because tDCS delivered over the prefrontal cortex induced an immediate change in the WM task but left the practice-dependent proficiency unchanged, the effects of cerebellar tDCS are structure-specific. Cerebellar tDCS left VEPs unaffected, its effect on the Sternberg task therefore seems unlikely to arise from visual system involvement. In conclusion, tDCS over the cerebellum specifically impairs the practice-dependent proficiency increase in verbal WM.

The dynamic network subserving the three phases of cognitive procedural learning

Cognitive procedural learning is characterized by three phases (cognitive, associative, and autonomous), each involving distinct processes. We performed a behavioral study and a positron emission tomography (PET) activation study using the Tower of Toronto task. The aim of the behavioral study was to determine cognitive predictors for the length of each of the three learning phases, in order to preselect subjects for the PET study. The objective of the second study was to describe the cerebral substrates subtending these three phases. Contrasted with a reference (motor) task, the cognitive phase activated the prefrontal cortex, cerebellum, and parietal regions, all of which became less active as learning progressed. The associative phase was characterized by the activation of the occipital regions, right thalamus, and caudate nucleus. During the autonomous phase, new regions were involved, including the left thalamus and an anterior part of the cerebellum. These results, by employing a direct comparison between phases, provide the first evidence of the involvement and the time course of activation of different regions in each learning phase, in accordance with current models of cognitive procedural learning. The involvement of a frontoparietal network suggests the use of strategies in problem solving during the cognitive phase. The involvement of the occipital regions during the associative and autonomous phase suggests the intervention of mental imagery. Lastly, the activation of the cerebellum during the autonomous phase is consistent with the fact that performance in this phase is determined by psychomotor abilities.

Differences in saccade-evoked brain activation patterns with eyes open or eyes closed in complete darkness

In this study we attempted to differentiate distinct components of the saccade network, namely cortical ocular motor centers and parieto-occipital brain regions, by means of a "minimal design" approach. Using a blocked design fMRI paradigm we evaluated the BOLD changes in a 2 x 2 factorial design experiment which was performed in complete darkness: while looking straight ahead with eyes open (OPEN) or closed (CLOSED) as well as during the execution of self-initiated horizontal to-and-fro saccades with the eyes open (SACCopen) or closed (SACCclosed). Eye movements were monitored outside the scanner via electro-oculography and during scanning using video-oculography. Unintentional eye-drifts did not differ during OPEN and CLOSED and saccade frequencies, and amplitudes did not vary significantly between the two saccade conditions. The main findings of the functional imaging study were as follows: (1) Saccades with eyes open or closed in complete darkness lead to distinct differences in brain activation patterns. (2) A parieto-occipital brain region including the precuneus, superior parietal lobule, posterior part of the intraparietal sulcus (IPS), and cuneus was relatively deactivated during saccades performed with eyes closed but not during saccades with eyes open or when looking straight ahead. This could indicate a preparatory state for updating spatial information, which is active during saccades with eyes open even without actual visual input. The preparatory state is suppressed when the eyes are closed during the saccades. (3) Selected ocular motor areas, not including the parietal eye field (PEF), show a stronger activation during SACCclosed than during SACCopen. The increased effort involved in performing saccades with eyes closed, perhaps due to the unusualness of the task, may be the cause of this increased activation.

Relative contributions of the cerebellar vermis and prefrontal lobe volumes on cognitive function across the adult lifespan

Recent research has revealed significant relationships between the vermian regions of the cerebellum and cognitive functions typically associated with prefrontal lobe function. These relationships are believed to be supported by anatomical connections between the distant brain regions. Recent evidence also suggests that age-related reductions in the posterior vermis are associated with age-related decline in frontal lobe cognitive functions, but these studies did not consider concomitant age-related atrophy of the prefrontal lobes. In the present study we addressed this issue by examining cognitive and structural MRI data obtained from 251 adults ranging in age from 18 to 79. Cognition was examined with a computerized cognitive battery and volumes of the cerebellar vermian regions and the prefrontal lobes were determined using quantitative morphometry. Results of the study revealed that both prefrontal and vermian volumes were smaller in older adults compared to younger adults, and both volumes correlated with cognitive performances in the older individuals. However, after controlling for prefrontal volume, the relationships between cognitive function and vermian volumes were eliminated, whereas prefrontal lobe volume remained significantly related to cognitive function after controlling for vermian volumes. These results suggest that while a reduction in cerebellar vermian volume does not significantly relate to normal age-related cognitive decline, prefrontal volume is significantly related to cognitive aging. Our results are consistent with the frontal aging hypothesis.

Magnetic resonance imaging (MRI) findings and neuropsychological sequelae in children after severe traumatic brain injury: the role of cerebellar lesion

We studied the relationships between magnetic resonance imaging (MRI) findings and neuropsychological sequelae in children after severe traumatic brain injury. Twenty-three children ages 7-13 years underwent MRI assessment of brain lesion topography and volume and neuropsychological evaluations, more than 1 year after sustaining severe traumatic brain injury. Most children had lesions to the corpus callosum and frontal lobes. Total lesion volume and extent of cerebral atrophy did not impact on the neuropsychological evaluation. Additional relationships were observed: left frontal lesions with lower semantic verbal fluency, right occipital lesions with lower visual recognition task scores, dyscalculia with cerebellar lesions, and cerebellar damage with lower cognitive performances and lower visual recognition memory. This study demonstrates the significance of the cerebellum's role in neuropsychological outcomes after traumatic brain injury and the importance of the lesion depth classification in predicting functional results.

Cerebellar Vermis Relative Hypermetabolism: An Almost Constant PET Finding in an Injured Brain

Cortical alterations of brain metabolism, as seen in PET, obviously depend on the nature of the damage (either mechanical, toxic, anoxic, or other). However, some subcortical abnormalities seem to occur rather frequently regardless of the extension, position and cause of the damage. In particular, relative cerebellar vermis activation seems to be frequently encountered. The aim of this work was to determine the incidence of this pattern in a heterogeneous population of brain trauma, and to compare it on a quantitative basis with a group of age-sex matched controls. The case records of this study consist of 58 consecutive patients, 44 males, 14 females, age 14-69 (median 34) 44 traumatic, 8 anoxic, 4 vascular and 2 toxic injuries. In the trauma group, the visualization of the cerebellar vermis was readily appreciable as a consistent majority of cases. In particular, the mean vermis/cerebellum ratio (calculated by appropriate ROI positioning) was 1.26 +/- 0.17 SD (range 0.92-1.82); in the control group the same parameters showed much less dispersion: average 0.92 +/- 0.06, range 0.80-1.10 (P < 0.005). If, on the basis of the normal group data, a cut-off value of 1 is accepted for the v/c ratio, it is noted that 54/57 trauma patients (95%) showed a ratio above this value. In conclusion, a hypermetabolic cerebellar vermis is a common finding in a damaged brain, regardless of the nature of the trauma (probably due to the relative preservation compared with other structures of alternative metabolic pathways), and seems to be the hallmark of the injured brain.

The influences of task difficulty and response correctness on neural systems supporting fluid reasoning

This functional magnetic resonance imaging (fMRI) study examined neural contributions to managing task difficulty and response correctness during fluid reasoning. Previous studies investigate reasoning by independently varying visual complexity or task difficulty, or the specific domain. Under natural conditions these factors interact in a complex manner to support dynamic combinations of perceptual and conceptual processes. This study investigated fluid reasoning under circumstances that would represent the cognitive flexibility of real life decision-making. Results from a mixed effects analysis corrected for multiple comparisons indicate involvement of cortical and subcortical areas during fluid reasoning. A 2 x 2 ANOVA illustrates activity related to variances in task difficulty correlated with increased blood oxygenation level-dependent (BOLD)-signal in the left middle frontal gyrus (BA6). Activity related to response correctness correlated with increased BOLD-signal in a larger, distributed system including right middle frontal gyrus (BA6), right superior parietal lobule (BA7), left inferior parietal lobule (BA40), left lingual gyrus (BA19), and left cerebellum (Lobule VI). The dissociation of function in left BA 6 for task difficulty and right BA6 for response correctness and the involvement of a more diffuse network involving the left cerebellum in response correctness extends knowledge about contributions of classic motor and premotor areas supporting higher level cognition.

Brain Basis of Developmental Change in Visuospatial Working Memory

Although brain changes associated with the acquisition of cognitive abilities in early childhood involve increasing localized specialization, little is known about the brain changes associated with the refinement of existing cognitive abilities that reach maturity in adolescence. The goal of this study was to investigate developmental changes in functional brain circuitry that support improvements in visuospatial working memory from childhood to adulthood. We tested thirty 8- to 47-year-olds in an oculomotor delayed response task. Developmental transitions in brain circuitry included both quantitative changes in the recruitment of necessary working memory regions and qualitative changes in the specific regions recruited into the functional working memory circuitry. Children recruited limited activation from core working memory regions (dorsal lateral prefrontal cortex [DLPFC] and parietal regions) and relied primarily on ventromedial regions (caudate nucleus and anterior insula). With adolescence emerged a more diffuse network (DLPFC, anterior cingulate, posterior parietal, anterior insula) that included the functional integration of premotor response preparation and execution circuitry. Finally, adults recruited the most specialized network of localized regions together with additional performance-enhancing regions, including left-lateralized DLPFC, ventrolateral prefrontal cortex, and supramarginal gyrus. These results suggest that the maturation of adult-level cognition involves a combination of increasing localization within necessary regions and their integration with performance-enhancing regions.

Robot-aided intensive training in post-stroke recovery

The successful motor rehabilitation of stroke patients requires an intensive and task-specific therapy approach. The plasticity of the adult human brain provides opportunities to enhance traditional rehabilitation programs for these individuals. Intensive robot-aided sensorimotor training may have a positive effect on reducing impairment and disability and increasing reorganization of the adult brain. This approach may therefore efficaciously complement standard post-stroke multidisciplinary programs as shown by recent experimental trials.

Aprendizagem de procedimentos e efeitos ansiolíticos: medidas eletrencefalográficas, motora e atencional

O objetivo do presente estudo foi avaliar parâmetros atencionais, motores e eletrencefalográficos durante uma tarefa de procedimentos em sujeitos que ingeriram 6mg de bromazepam. A amostra consistiu de 26 sujeitos saudáveis, ambos os sexos, entre 19 e 36 anos. Os grupos controle e experimental foram submetidos à tarefa datilográfica em desenho duplo-cego randomizado. Os achados não revelaram diferenças nas medidas atencionais e motoras entre os grupos. Foram avaliadas medidas de coerência (EEGq) entre regiões do escalpo nas bandas teta, alfa e beta. Análise inicial revelou um efeito principal para condição (Anova 2- critérios de variação - condição versus blocos). Uma segunda Anova, também com 2 critérios de variação (condição versus região do escalpo), demonstrou um efeito principal para ambos os fatores. Em conclusão, a medida de coerência parece não ser uma ferramenta sensível para demonstrar diferenças entre áreas corticais em função de uma tarefa de procedimentos.

Is there evidence for neural compensation in attention deficit hyperactivity disorder? A review of the functional neuroimaging literature

This article reviews evidence for the presence of a compensatory, alternative, neural system and its possible link to associated processing strategies in children and adults with attention deficit hyperactivity disorder (ADHD). The article presents findings on a region by region basis that suggests ADHD should be characterized not only by neural hypo-activity, as it is commonly thought but neural hyperactivity as well, in regions of the brain that may relate to compensatory brain and behavioral functioning. In this context studies from the functional neuroimaging literature are reviewed. We hypothesize that impaired prefrontal (PFC) and anterior cingulate (ACC) cortex function in ADHD reduces the ability to optimally recruit subsidiary brain regions and strategies to perform cognitive tasks. The authors conclude that healthy individuals can recruit brain regions using visual, spatial or verbal rehearsal for tasks as needed. In contrast, individuals with ADHD may be less able to engage higher order executive systems to flexibly recruit brain regions to match given task demands. This may result in greater reliance on neuroanatomy that is associated with visual, spatial, and motoric processing rather than verbal strategies. The authors speculate that this impaired flexibility in recruiting brain regions and associated strategies limits adaptation to new cognitive demands as they present and may require more effortful processing.

Temporal information processing in ADHD: Findings to date and new methods

The ability to perceive and represent time is a fundamental but complex cognitive skill that allows us to perceive and organize sequences of events and actions, and to anticipate or predict when future events will occur. It is a multidimensional construct, and a variety of methods have been used to understand timing performance in ADHD samples, which makes it difficult to integrate findings across studies. While further replication is needed, growing evidence links ADHD to problems in several aspects of temporal information processing, including duration discrimination, duration reproduction, and finger tapping. Neuroimaging studies of ADHD have also implicated cerebellar, basal ganglia, and prefrontal regions of the brain, which are believed to subserve temporal information processing. This line of research implicates more basic cognitive mechanisms than previously linked with ADHD and challenges researchers to develop and utilize innovative, multidisciplinary, scientific methods to dissect the various components of temporal information processing. Recent advances in neuroimaging, such as magnetoencephalography in collaboration with structural magnetic resonance imaging, can discriminate temporal processing at the level of a millisecond. This approach can lay the groundwork to provide a more precise understanding of neural network activity during different aspects and stages of temporal information processing in ADHD.

Intermanual transfer effects in sequential tactuomotor learning: evidence for effector independent coding

Results from our earlier brain imaging studies regarding motor learning have shown different areas activated during naive and practiced performance. When right handed participants moved a pen either with the dominant or non-dominant hand continuously through a cut-out maze as quickly and accurately as possible, practice resulted in decreased brain activity in right premotor and parietal areas as well as left cerebellum, while increased activity was found in the supplementary motor area (SMA). These lateralized practiced-related changes in brain activation suggest effector-independent abstract coding of information. To test this hypothesis more extensively, intermanual transfer of learning was examined in 24 male and female participants (12 right- and 12 left-handed) using the same maze-learning task. It was hypothesized that if an abstract representation of the movement is learned and stored, intermanual transfer effects should be more pronounced when participants transferred to a same maze as opposed to a mirror image of the maze. Errors and velocity were measured during the following conditions: initial naive performance (Naive); after practice on the maze (Prac); during intermanual transfer to the same maze (Transfer Identical); and to the mirror maze (Transfer Mirror). Transfer direction was tested from the dominant to non-dominant hand and vice versa. No significant differences were found between right- and left-handed participants, males and females, and transfer directions. However, intermanual transfer of learning was significantly greater to the identical maze as opposed to the mirror maze. These results showed that learning was indeed taking place at an abstract effector independent level.

Resistance-based high resolution recording of predefined 2-dimensional pen trajectories in an fMRI setting

The recent advent of functional magnetic resonance imaging (fMRI) as a readily accessible neuroimaging method has led to exciting new insights into the functioning of the human motor system. However, technical complications related to the fMRI scanner environment often limit the ability to measure the desired behavioral data reflecting the subjects' movements. In order to perform kinematic registrations of predefined complex two-dimensional movement patterns while scanning, a new MR-compatible setup has been developed. The method presented here allows the recording of detailed pen tracing data during concurrent functional image acquisition. Essentially, temporally high resolved resistance measurements are used to keep track of the covered distance across time, as applied here to the tracing of various mazes. In this way, the current setup adds the close monitoring of continuous tracing movements to the spectrum of behavioral data which can be successfully obtained in an fMRI setting.

Emergence of rhythm during motor learning

Complex motor skill often consists of a fixed sequence of movements. Recent studies show that a stereotyped temporal pattern or rhythm emerges as we learn to perform a motor sequence. This is because the sequence is reorganized during learning as serial chunks of movements in both a sequence-specific and subject-specific manner. On the basis of human imaging studies we propose that the formation of chunk patterns is controlled by the cerebellum, its posterior and anterior lobes contributing, respectively, to the temporal patterns before and after chunk formation. The motor rhythm can assist the motor networks in the cerebral cortex to control automatic movements within chunks and the cognitive networks to control non-automatic movements between chunks, respectively. In this way, organized motor skill can be performed automatically and flexibly.

Functional motor compensation in amyotrophic lateral sclerosis

The present study investigated the fMRI correlates of functional compensation/neural reorganization of the motor system in patients with amyotrophic lateral sclerosis (ALS). The hypothesis was that ALS patients would recruit additional brain regions compared with controls in a motor task and that activity in these regions would vary as a function of task difficulty. Patients and controls executed a motor task with two sequences (a simple and a more difficult one) of consecutive button presses. Patients and controls both activated brain regions known to be involved in motor execution and control. Activity in ipsilateral motor areas as well as difficulty-related activity in the left cerebellum could only be observed in patients. The behavioral data indicated that the motor task was much more difficult for patients than for controls. At nearly equal difficulty the observed patterns of hemodynamic activity in controls were very similar to those observed in ALS. The findings suggest that functional compensation in ALS relies on existing resources and mechanisms that are not primarily developed as a consequence of the lesion.

Functional changes in brain activity during acquisition and practice of movement sequences

In the present study, brain activations were measured using positron emission tomography (PET) over the course of practice. Fourteen right-handed participants were scanned during six 1-min periods of practice tracing a cut-out maze design with their eyes closed. Practice-related decreases were found in the right premotor and posterior parietal cortex and left cerebellum, increases in the supplementary motor area (SMA) and primary motor cortex. The decrease in right premotor activity and the increase in SMA was significantly correlated with a decrease in the number of stops, implying involvement in learning and storing the movement sequence. The significant correlation between decreases in errors and left cerebellar and right posterior parietal activity suggests a role in accuracy. Involvement of the primary motor cortex in motor execution is suggested by the correlation of increased activation and movement speed. These results suggest that different neural structures (involving a premotor-parietal-cerebellar circuit) play a role in a sequential maze learning task.

Practice-induced changes of brain function during visual attention: a parametric fMRI study at 4 Tesla

A parametric functional MRI (fMRI) study with three levels of task difficulty was performed to determine the effect of practice and attentional load on brain activation during visual attention tasks. Brief practice during repeat fMRI scanning (20 min) did not change performance accuracy or reaction times (RT), but decreased activation bilaterally in the inferior, middle, and superior frontal gyri, superior temporal gyrus, thalamus, and cerebellum. Increased attentional load decreased performance accuracy but not RT, and increased activation bilaterally in the inferior, posterior, and superior parietal cortices, thalamus, cerebellum, and frontal gyri. These changes suggest that practice decreases dependency on thalamus, cerebellum, and the frontal cortices for controlled task processing possibly due to increased efficiency of the attentional network. Since short-term practice-effects in the prefrontal cortex may be similar to attentional load-effects, studies of attentional load need to take practice effects into account.

White Matter Lesions Detected by Magnetic Resonance Imaging After Radiotherapy and High-Dose Chemotherapy in Children With Medulloblastoma or Primitive Neuroectodermal Tumor

Purpose

White matter lesions (WMLs) have been described as a delayed effect of cranial irradiation in children with brain tumors, or a transient subacute effect characterized by an intralesional or perilesional reaction. We report the occurrence of subacute WMLs detected by magnetic resonance imaging (MRI) in children treated for medulloblastoma or primitive neuroectodermal tumor (PNET) and document the associated clinical, radiologic, and neurocognitive findings.

Patients and Methods

Among 134 patients with medulloblastoma or supratentorial PNET treated prospectively with risk-adjusted craniospinal irradiation and conformal boost to the tumor bed, followed by four high-dose chemotherapy (HDC) cycles with stem-cell rescue, 22 developed WMLs on T1-weighted imaging with and without contrast and/or T2-weighted imaging on MRI. Patients had ≥ 12 months of follow-up. Neurocognitive assessments included intelligence quotient (IQ) tests and tests of academic achievement.

Results

Twenty-two patients developed WMLs at a median of 7.8 months after starting therapy (range, 1.9 to 13.0 months). Lesions were predominantly in the pons (n = 8) and cerebellum (n = 6). Sixteen patients (73%) had WML resolution at a median of 6.2 months (range, 1.68 to 23.5 months) after onset; two patients developed necrosis and atrophy. Three developed persistent neurologic deficits. Cumulative incidence of WMLs at 1 year was 15% ± 3%. Patients with WMLs had a significant decline in estimated IQ (−2.5 per year; P = .03) and math (−4.5 per year; P = .003) scores.

Conclusion

WMLs in medulloblastoma or PNET patients treated with conformal radiotherapy and HDC are typically transient and asymptomatic, and may mimic early tumor recurrence. A minority of patients with WMLs develop permanent neurologic deficits and imaging changes. Overall, the presence of WMLs is associated with greater neurocognitive decline.

Cerebellar and premotor function in bimanual coordination: parametric neural responses to spatiotemporal complexity and cycling frequency

In the present functional magnetic resonance imaging (fMRI) study, we assessed the neural network governing bimanual coordination during manipulations of spatiotemporal complexity and cycling frequency. A parametric analysis was applied to determine the effects of each of both factors as well as their interaction. Subjects performed four different cyclical movement tasks of increasing spatiotemporal complexity (i.e., unimanual left-right hand movements, bimanual in-phase movements, bimanual anti-phase movements, and bimanual 90 degrees out-of-phase movements) across four frequency levels (0.9, 1.2, 1.5, and 1.8 Hz). Results showed that, within the network involved in bimanual coordination, functional subcircuits could be distinguished: Activation in the supplementary motor area, superior parietal cortex (SPS), and thalamic VPL Nc was mainly correlated with increasing spatiotemporal complexity of the limb movements, suggesting that these areas are involved in higher-order movement control. By contrast, activation within the primary motor cortex, cingulate motor cortex (CMC), globus pallidus, and thalamic VLo Nc correlated mainly with movement frequency, indicating that these areas play an important role during movement execution. Interestingly, the cerebellum and the dorsal premotor cortex were identified as the principal regions responding to manipulation of both parameters and exhibiting clear interaction effects. Therefore, it is concluded that both areas represent critical sites for the control of bimanual coordination.

Attenuation of activity-induced increases in cerebellar blood flow by lesion of the inferior olive

We sought to define the contribution of the climbing fibers (CF), one of the major inputs to Purkinje neurons, to the increase in cerebellar blood flow (BFcrb) produced by activation of the cerebellar cortex. The neurotoxin 3-acetylpyridine was used to lesion the inferior olive, the site from which the CF originate. Crus II, an area of the cerebellar cortex that receives sensory afferents from the perioral region, was activated by low-intensity stimulation of the upper lip (5-25 V and 4-16 Hz) in sham-lesioned and lesioned mice. BFcrb was recorded in crus II using a laser-Doppler flow probe. The increase in BFcrb produced by harmaline, an alkaloid that activates the CF, was abolished in lesioned mice (P > 0.05 vs. BFcrb before harmaline, n = 6), attesting to the effectiveness of the lesion. In sham-lesioned animals, upper lip stimulation increased BFcrb in crus II by 25 +/- 2% (25 V and 10 Hz, n = 6). The rise in BFcrb was attenuated by 63 +/- 7% (25 V and 10 Hz) in lesioned mice (P < 0.05, n = 6). In contrast, the increase in BFcrb produced by hypercapnia was not affected (P > 0.05). These data suggest that CF are responsible for a substantial portion of the increase in BFcrb produced by crus II activation. Thus the hemodynamic response evoked by functional activation of the cerebellar cortex reflects, in large part, CF activity.