Contribution of the cerebellum to neuropsychological functioning: evidence from a case of cerebellar degenerative disorder

A Scoping Review on Movement, Neurobiology and Functional Deficits in Dyslexia: Suggestions for a Three-Fold Integrated Perspective

Developmental dyslexia is a common complex neurodevelopmental disorder. Many theories and models tried to explain its symptomatology and find ways to improve poor reading abilities. The aim of this scoping review is to summarize current findings and several approaches and theories, focusing on the interconnectedness between motion, emotion and cognition and their connection to dyslexia. Consequently, we present first a brief overview of the main theories and models regarding dyslexia and its proposed neural correlates, with a particular focus on cerebellar regions and their involvement in this disorder. After examining different types of intervention programs and remedial training, we highlight the effects of a specific structured sensorimotor intervention named Quadrato Motor Training (QMT). QMT utilizes several cognitive and motor functions known to be relevant in developmental dyslexia. We introduce its potential beneficial effects on reading skills, including working memory, coordination and attention. We sum its effects ranging from behavioral to functional, structural and neuroplastic, especially in relation to dyslexia. We report several recent studies that employed this training technique with dyslexic participants, discussing the specific features that distinguish it from other training within the specific framework of the Sphere Model of Consciousness. Finally, we advocate for a new perspective on developmental dyslexia integrating motion, emotion and cognition to fully encompass this complex disorder.

Neurological Soft Signs (NSS) in Census-Based, Decade-Adjusted Healthy Adults, 20 to >70 Years of Age

Neurological soft signs (NSS) represent minor neurological features and have been widely studied in psychiatric disease. The assessment is easily performed. Quantity and quality may provide useful information concerning the disease course. Mostly, NSS scores differ significantly between patients and controls. However, literature does not give reference values. In this pilot study, we recruited 120 healthy women and men to build a cross-sectional, census-based sample of healthy individuals, aged 20 to >70 years, subdivided in 10-year blocks for a close approach to the human lifeline. Testing for NSS and neurocognitive functioning was performed following the exclusion of mental and severe physical illness. NSS scores increased significantly between ages 50+ and 60+, which was primarily accountable to motor signs. Gender and cognitive functioning were not related to changes of scores. Although the number of individuals is small, study results may lay a foundation for further validation of NSS in healthy individuals.

Spatiotemporal development of spinal neuronal and glial populations in the Ts65Dn mouse model of Down syndrome

BACKGROUND

Down syndrome (DS), caused by the triplication of chromosome 21, results in a constellation of clinical features including changes in intellectual and motor function. Although altered neural development and function have been well described in people with DS, few studies have investigated the etiology underlying the observed motor phenotypes. Here, we examine the development, patterning, and organization of the spinal cord throughout life in the Ts65Dn mouse, a model that recapitulates many of the motor changes observed in people with DS.

METHODS

Spinal cords from embryonic to adult animals were processed for gene and protein expression (immunofluorescence) to track the spatiotemporal development of excitatory and inhibitory neurons and oligodendroglia. Postnatal analyses were focused on the lumbar region due to the reflex and gait abnormalities found in Ts65Dn mice and locomotive alterations seen in people with DS.

RESULTS

Between embryonic days E10.5 and E14.5, we found a larger motor neuron progenitor domain in Ts65Dn animals containing more OLIG2-expressing progenitor cells. These disturbed progenitors are delayed in motor neuron production but eventually generate a large number of ISL1+ migrating motor neurons. We found that higher numbers of PAX6+ and NKX2.2+ interneurons (INs) are also produced during this time frame. In the adult lumbar spinal cord, we found an increased level of Hb9 and a decreased level of Irx3 gene expression in trisomic animals. This was accompanied by an increase in Calretinin+ INs, but no changes in other neuronal populations. In aged Ts65Dn animals, both Calbindin+ and ChAT+ neurons were decreased compared to euploid controls. Additionally, in the dorsal corticospinal white matter tract, there were significantly fewer CC1+ mature OLs in 30- and 60-day old trisomic animals and this normalized to euploid levels at 10-11 months. In contrast, the mature OL population was increased in the lateral funiculus, an ascending white matter tract carrying sensory information. In 30-day old animals, we also found a decrease in the number of nodes of Ranvier in both tracts. This decrease normalized both in 60-day old and aged animals.

CONCLUSIONS

We show marked changes in both spinal white matter and neuronal composition that change regionally over the life span. In the embryonic Ts65Dn spinal cord, we observe alterations in motor neuron production and migration. In the adult spinal cord, we observe changes in oligodendrocyte maturation and motor neuron loss, the latter of which has also been observed in human spinal cord tissue samples. This work uncovers multiple cellular perturbations during Ts65Dn development and aging, many of which may underlie the motor deficits found in DS.

Links between looking and speaking in autism and first-degree relatives: insights into the expression of genetic liability to autism

Background

Rapid automatized naming (RAN; naming of familiar items presented in an array) is a task that taps fundamental neurocognitive processes that are affected in a number of complex psychiatric conditions. Deficits in RAN have been repeatedly observed in autism spectrum disorder (ASD), and also among first-degree relatives, suggesting that RAN may tap features that index genetic liability to ASD. This study used eye tracking to examine neurocognitive mechanisms related to RAN performance in ASD and first-degree relatives, and investigated links to broader language and clinical-behavioral features.

Methods

Fifty-one individuals with ASD, biological parents of individuals with ASD (n = 133), and respective control groups (n = 45 ASD controls; 58 parent controls) completed RAN on an eye tracker. Variables included naming time, frequency of errors, and measures of eye movement during RAN (eye-voice span, number of fixations and refixations).

Results

Both the ASD and parent-ASD groups showed slower naming times, more errors, and atypical eye-movement patterns (e.g., increased fixations and refixations), relative to controls, with differences persisting after accounting for spousal resemblance. RAN ability and associated eye movement patterns were correlated with increased social-communicative impairment and increased repetitive behaviors in ASD. Longer RAN times and greater refixations in the parent-ASD group were driven by the subgroup who showed clinical-behavioral features of the broad autism phenotype (BAP). Finally, parent-child dyad correlations revealed associations between naming time and refixations in parents with the BAP and increased repetitive behaviors in their child with ASD.

Conclusions

Differences in RAN performance and associated eye movement patterns detected in ASD and in parents, and links to broader social-communicative abilities, clinical features, and parent-child associations, suggest that RAN-related abilities might constitute genetically meaningful neurocognitive markers that can help bridge connections between underlying biology and ASD symptomatology.

The functional anatomy of the cerebrocerebellar circuit: A review and new concepts

The cerebrocerebellar circuit is a feedback circuit that bidirectionally connects the neocortex and the cerebellum. According to the classic view, the cerebrocerebellar circuit is specifically involved in the functional regulation of the motor areas of the neocortex. In recent years, studies carried out in experimental animals by morphological and physiological methods, and in humans by magnetic resonance imaging, have indicated that the cerebrocerebellar circuit is also involved in the functional regulation of the nonmotor areas of the neocortex, including the prefrontal, associative, sensory and limbic areas. Moreover, a second type of cerebrocerebellar circuit, bidirectionally connecting the hypothalamus and the cerebellum, has been detected, being specifically involved in the regulation of the hypothalamic functions. This review analyzes the morphological features of the centers and pathways of the cerebrocerebellar circuits, paying particular attention to their organization in different channels, which separately connect the cerebellum with the motor areas and nonmotor areas of the neocortex, and with the hypothalamus. Actually, a considerable amount of new data have led, and are leading, to profound changes on the views on the anatomy, physiology, and pathophysiology of the cerebrocerebellar circuits, so much they may be now considered to be essential for the functional regulation of many neocortex areas, perhaps all, as well as of the hypothalamus and of the limbic system. Accordingly, clinical studies have pointed out an involvement of the cerebrocerebellar circuits in the pathophysiology of an increasing number of neuropsychiatric disorders.

Transcranial Cerebellar Direct Current Stimulation Enhances Verb Generation but Not Verb Naming in Poststroke Aphasia

Although the role of the cerebellum in motor function is well recognized, its involvement in the lexical domain remains to be further elucidated. Indeed, it has not yet been clarified whether the cerebellum is a language structure per se or whether it contributes to language processing when other cognitive components (e.g., cognitive effort, working memory) are required by the language task. Neuromodulation studies on healthy participants have suggested that cerebellar transcranial direct current stimulation (tDCS) is a valuable tool to modulate cognitive functions. However, so far, only a single case study has investigated whether cerebellar stimulation enhances language recovery in aphasic individuals. In a randomized, crossover, double-blind design, we explored the effect of cerebellar tDCS coupled with language treatment for verb improvement in 12 aphasic individuals. Each participant received cerebellar tDCS (20 min, 2 mA) in four experimental conditions: (1) right cathodal and (2) sham stimulation during a verb generation task and (3) right cathodal and (4) sham stimulation during a verb naming task. Each experimental condition was run in five consecutive daily sessions over 4 weeks. At the end of treatment, a significant improvement was found after cathodal stimulation only in the verb generation task. No significant differences were present for verb naming among the two conditions. We hypothesize that cerebellar tDCS is a viable tool for recovery from aphasia but only when the language task, such as verb generation, also demands the activation of nonlinguistic strategies.

Changes of Functional and Directed Resting-State Connectivity Are Associated with Neuronal Oscillations, ApoE Genotype and Amyloid Deposition in Mild Cognitive Impairment

The assessment of effects associated with cognitive impairment using electroencephalography (EEG) power mapping allows the visualization of frequency-band specific local changes in oscillatory activity. In contrast, measures of coherence and dynamic source synchronization allow for the study of functional and effective connectivity, respectively. Yet, these measures have rarely been assessed in parallel in the context of mild cognitive impairment (MCI) and furthermore it has not been examined if they are related to risk factors of Alzheimer’s disease (AD) such as amyloid deposition and apolipoprotein ε4 (ApoE) allele occurrence. Here, we investigated functional and directed connectivities with Renormalized Partial Directed Coherence (RPDC) in 17 healthy controls (HC) and 17 participants with MCI. Participants underwent ApoE-genotyping and Pittsburgh compound B positron emission tomography (PiB-PET) to assess amyloid deposition. We observed lower spectral source power in MCI in the alpha and beta bands. Coherence was stronger in HC than MCI across different neuronal sources in the delta, theta, alpha, beta and gamma bands. The directed coherence analysis indicated lower information flow between fronto-temporal (including the hippocampus) sources and unidirectional connectivity in MCI. In MCI, alpha and beta RPDC showed an inverse correlation to age and gender; global amyloid deposition was inversely correlated to alpha coherence, RPDC and beta and gamma coherence. Furthermore, the ApoE status was negatively correlated to alpha coherence and RPDC, beta RPDC and gamma coherence. A classification analysis of cognitive state revealed the highest accuracy using EEG power, coherence and RPDC as input. For this small but statistically robust (Bayesian power analyses) sample, our results suggest that resting EEG related functional and directed connectivities are sensitive to the cognitive state and are linked to ApoE and amyloid burden.

Eye-voice span during rapid automatized naming: evidence of reduced automaticity in individuals with autism spectrum disorder and their siblings

Background

Individuals with autism spectrum disorder (ASD) and their parents demonstrate impaired performance in rapid automatized naming (RAN), a task that recruits a variety of linguistic and executive processes. Though the basic processes that contribute to RAN differences remain unclear, eye-voice relationships, as measured through eye tracking, can provide insight into cognitive and perceptual processes contributing to RAN performance. For example, in RAN, eye-voice span (EVS), the distance ahead the eyes are when articulation of a target item's label begins, is an indirect measure of automaticity of the processes underlying RAN. The primary objective of this study was to investigate automaticity in naming processes, as indexed by EVS during RAN. The secondary objective was to characterize RAN difficulties in individuals with ASD and their siblings.

Methods

Participants (aged 15–33 years) included 21 individuals with ASD, 23 siblings of individuals with ASD, and 24 control subjects, group-matched on chronological age. Naming time, frequency of errors, and EVS were measured during a RAN task and compared across groups.

Results

A stepwise pattern of RAN performance was observed, with individuals with ASD demonstrating the slowest naming across all RAN conditions, controls demonstrating the fastest naming, and siblings demonstrating intermediate performance. Individuals with ASD exhibited smaller EVSs than controls on all RAN conditions, and siblings exhibited smaller EVSs during number naming (the most highly automatized type of naming). EVSs were correlated with naming times in controls only, and only in the more automatized conditions.

Conclusions

These results suggest that reduced automaticity in the component processes of RAN may underpin differences in individuals with ASD and their siblings. These findings also provide further support that RAN abilities are impacted by genetic liability to ASD. This study has important implications for understanding the underlying skills contributing to language-related deficits in ASD.

Changes in cerebellar activity and inter-hemispheric coherence accompany improved reading performance following Quadrato Motor Training

Dyslexia is a multifactorial reading deficit that involves multiple brain systems. Among other theories, it has been suggested that cerebellar dysfunction may be involved in dyslexia. This theory has been supported by findings from anatomical and functional imaging. A possible rationale for cerebellar involvement in dyslexia could lie in the cerebellum’s role as an oscillator, producing synchronized activity within neuronal networks including sensorimotor networks critical for reading. If these findings are causally related to dyslexia, a training regimen that enhances cerebellar oscillatory activity should improve reading performance. We examined the cognitive and neural effects of Quadrato Motor Training (QMT), a structured sensorimotor training program that involves sequencing of motor responses based on verbal commands. Twenty-two adult Hebrew readers (12 dyslexics and 10 controls) were recruited for the study. Using Magnetoencephalography (MEG), we measured changes in alpha power and coherence following QMT in a within-subject design. Reading performance was assessed pre- and post-training using a comprehensive battery of behavioral tests. Our results demonstrate improved performance on a speeded reading task following one month of intensive QMT in both the dyslexic and control groups. Dyslexic participants, but not controls, showed significant increase in cerebellar oscillatory alpha power following training. In addition, across both time points, inter-hemispheric alpha coherence was higher in the dyslexic group compared to the control group. In conclusion, the current findings suggest that the combination of motor and language training embedded in QMT increases cerebellar oscillatory activity in dyslexics and improves reading performance. These results support the hypothesis that the cerebellum plays a role in skilled reading, and begin to unravel the underlying mechanisms that mediate cerebellar contribution in cognitive and neuronal augmentation.

Isolating a cerebellar contribution to rapid visual attention using transcranial magnetic stimulation

Patient and neuroimaging research have provided increasing support for a role of the posterior-lateral cerebellum in cognition, particularly attention. During rapid serial visual presentation, when two targets are presented in close temporal proximity (<500 ms), accuracy at detecting the second target (T2) suffers. This phenomenon is known as the attentional blink (AB), and in cerebellar lesion patients this effect is exaggerated. Damage to the cerebellum may thus disrupt the use of attentional resources during stimulus processing conditions that are temporally demanding. There are reciprocal connections between the cerebral cortex and the contralateral cerebellum, these connections allow for the possibility that lateralized functions in the cerebral cortex (such as language) remain lateralized in the cerebellum. The purpose of this study was to investigate the temporal characteristics of the cerebellar contribution to the AB and to functionally localize the contribution of the cerebellum to the AB using transcranial magnetic stimulation (TMS). We hypothesized that T2 accuracy would decrease after right cerebellar stimulation when the delay between the first target (T1) and T2 was short (120–400 ms) compared to long (720–960 ms). We used continuous theta burst stimulation (cTBS), a form of TMS, to transiently inhibit a focal population of neurons in the left and right posterior-lateral cerebellum of healthy participants (n = 45). Three groups of participants (n = 15) performed the AB before and after either sham, left, or right cerebellar stimulation. The results of this cTBS study support our hypothesis. During the short delay, participants in the right cTBS group showed a greater AB magnitude compared to both the left and sham cTBS groups (p < 0.05). No difference in T2 detection was found over long delays. The results provide further support for a cerebellar contribution to an integrated neural network recruited during temporally demanding attention-based tasks.

The cerebellum and its role in word generation: a cTBS study

The purpose of this study was to investigate the role of the cerebellum in the executive control of word generation using a phonemic and semantic fluency task. Phonemic fluency tasks require novel strategy to organize verbal output, and are more effortful than semantic fluency tasks. The number of category switches made between subcategories of words is a measure of mental flexibility, and is greatest during the early phase of the task (first 15sec). Both tasks were tested on healthy participants, before and after the application of transcranial magnetic stimulation using continuous theta burst stimulation (cTBS) applied over the left or the right posterior/lateral cerebellar cortex in separate groups. We hypothesized that the number of category switches and number of words produced within the first 15sec would be reduced after cTBS to the right, posterior-lateral cerebellum during phonemic fluency tasks. The results from the study were consistent with the hypothesis. Within the first 15sec of each trial, right cTBS participants displayed significantly lower switching scores (p=.05) after stimulation. Previous studies have illustrated similar impairments in switching between categories during phonemic fluency performance in patients with damage to the left frontal cortex. Our findings support the general hypothesis of cerebellar involvement in executive control through connections to the frontal cortex.

Evidence for topographic organization in the cerebellum of motor control versus cognitive and affective processing

Patients with cerebellar damage often present with the cerebellar motor syndrome of dysmetria, dysarthria and ataxia, yet cerebellar lesions can also result in the cerebellar cognitive affective syndrome (CCAS), including executive, visual spatial, and linguistic impairments, and affective dysregulation. We have hypothesized that there is topographic organization in the human cerebellum such that the anterior lobe and lobule VIII contain the representation of the sensorimotor cerebellum; lobules VI and VII of the posterior lobe comprise the cognitive cerebellum; and the posterior vermis is the anatomical substrate of the limbic cerebellum. Here we analyze anatomical, functional neuroimaging, and clinical data to test this hypothesis. We find converging lines of evidence supporting regional organization of motor, cognitive, and limbic behaviors in the cerebellum. The cerebellar motor syndrome results when lesions involve the anterior lobe and parts of lobule VI, interrupting cerebellar communication with cerebral and spinal motor systems. Cognitive impairments occur when posterior lobe lesions affect lobules VI and VII (including Crus I, Crus II, and lobule VIIB), disrupting cerebellar modulation of cognitive loops with cerebral association cortices. Neuropsychiatric disorders manifest when vermis lesions deprive cerebro-cerebellar-limbic loops of cerebellar input. We consider this functional topography to be a consequence of the differential arrangement of connections of the cerebellum with the spinal cord, brainstem, and cerebral hemispheres, reflecting cerebellar incorporation into the distributed neural circuits subserving movement, cognition, and emotion. These observations provide testable hypotheses for future investigations.

Neuroanatomical structures and segregated circuits

Segregated neural circuits that effect particular domain-specific behaviors can be differentiated from neuroanatomical structures implicated in many different aspects of behavior. The basal ganglionic components of circuits regulating nonlinguistic motor behavior, speech, and syntax all function in a similar manner. Hence, it is unlikely that special properties and evolutionary mechanisms are associated with the neural bases of human language.

How to grow a human

I enlarge on the theme that the brain mechanisms required for languageand other aspects of the human mind evolved through selective changes in the regulatory genes governing growth. Extension of the period of postnatal growth increases the role of the environment in structuring the brain, and spatiotemporal programming (heterochrony) ofgrowth might explain hierarchical representation, hemispheric specialization, and perhaps sex differences.

Genes, specificity, and the lexical/functional distinction in language acquisition

Contrary to Müller's claims, and in support of modular theories, genetic factors play a substantial and significant role in language. The finding that some children with specific language impairment (SLI) have nonlinguistic impairments may reflect improper diagnosis of SLI or impairments that are secondary to linguistic impairments. Thus, such findings do not argue against the modularity thesis. The lexical/functional distinction appears to be innate and specifically linguistic and could be instantiated in either symbolic or connectionist systems.

Autonomy of syntactic processing and the role of Broca's area

Both autonomy and local specificity are compatible with observed interconnectivity at the cell level when considering two different levels: cell assemblies and brain systems. Early syntactic structuring processes in particular are likely to representan autonomous module in the language/brain system.

Neurobiological approaches to language: Falsehoods and fallacies

The conclusion that language is not really innate or modular is based on several fallacies. I show that the target article confuses communicative skills with linguistic abilities, and that its discussion of brain/language relations is replete with factual errors. I also criticize its attempt to contrast biological and linguistic principles. Finally, I argue that no case is made for the “alternative” approach proposed here.

Is human language just another neurobiological specialization?

One can disagree with Müller that it is neurobiologically questionable to suppose that human language is innate, specialized, and species-specific, yet agree that the precise brain mechanisms controlling language in any individual will be influenced by epigenesis and genetic variability, and that the interplay between inherited and acquired aspects of linguistic capacity deserves to be investigated.

Evolutionary principles and the emergence of syntax

The belief that syntax is an innate, autonomous, species-specific module is highly questionable. Syntax demonstrates the mosaic nature of evolutionary change, in that it made use of (and led to the enhancement of) numerous preexisting neurocognitive features. It is best understood as an emergent characteristic of the explosion of semantic complexity that occurred during hominid evolution.

Neurobiology and linguistics are not yet unifiable

Neurobiological models of language need a level of analysis that can account for the typical range of language phenomena. Because linguistically motivated models have been successful in explaining numerous language properties, it is premature to dismiss them as biologically irrelevant. Models attempting to unify neurobiology and linguistics need to be sensitive to both sources of evidence.

An innate language faculty needs neither modularity nor localization

Müller misconstrues autonomy to mean strict locality of brain function, something quite different from the functional autonomy that linguists claim. Similarly, he misperceives the interaction of learned and innate components hypothesized in current generative models. Evidence from sign languages, Creole languages, and neurological studies of rare forms of aphasia also argues against his conclusions.

Sign language and the brain: Apes, apraxia, and aphasia

The study of signed languages has inspired scientific' speculation regarding foundations of human language. Relationships between the acquisition of sign language in apes and man are discounted on logical grounds. Evidence from the differential hreakdown of sign language and manual pantomime places limits on the degree of overlap between language and nonlanguage motor systems. Evidence from functional magnetic resonance imaging reveals neural areas of convergence and divergence underlying signed and spoken languages.

Innateness, autonomy, universality? Neurobiological approaches to language

The concepts of the innateness, universality, species-specificity, and autonomy of the human language capacity have had an extreme impact on the psycholinguistic debate for over thirty years. These concepts are evaluated from several neurobiological perspectives, with an emphasis on the emergence of language and its decay due to brain lesion and progressive brain disease.

Evidence of perceptuomotor homologies and preadaptations for human language in nonhuman primates suggests a gradual emergence of language during hominid evolution. Regarding ontogeny, the innate component of language capacity is likely to be polygenic and shared with other developmental domains. Dissociations between verbal and nonverbal development are probably rooted in the perceptuomotor specializations of neural substrates rather than the autonomy of a grammar module. Aphasiologicaldata often assumed to suggest modular linguistic subsystems can be accounted for in terms of a neurofunctional model incorporating perceptuomotor-based regional specializationsand distributivity of representations. Thus, dissociations between grammatical functors and content words are due to different conditions of acquisition and resulting differences in neural representation. Human brains are characterized by multifactorial interindividual variability, and strict universality of functional organization is biologically unrealistic.

A theoretical alternative is proposed according to which (1) linguistic specialization of brain areas is due to epigenetic and probabilistic maturational events, not to genetic ”hard-wiring,” and (2) linguistic knowledge is neurally represented in distributed cell assemblies whose topography reflects the perceptuomotor modalities involved in the acquisition and use of a given item of knowledge.

Normal Spatial Attention But Impaired Saccades and Visual Motion Perception After Lesions of the Monkey Cerebellum

Lesions of the cerebellum produce deficits in movement and motor learning. Saccadic dysmetria, for example, is caused by lesions of the posterior cerebellar vermis. Monkeys and patients with such lesions are unable to modify the amplitude of saccades. Some have suggested that the effects on eye movements might reflect a more global cognitive deficit caused by the cerebellar lesion. We tested that idea by studying the effects of vermis lesions on attention as well as saccadic eye movements, visual motion perception, and luminance change detection. Lesions in posterior vermis of four monkeys caused the known deficits in saccadic control. Attention tested by examination of acuity threshold changes induced by prior cueing of the location of the targets remained normal after vermis lesions. Luminance change detection was also unaffected by the lesions. In one case, after a lesion restricted to lobulus VIII, the animal had impaired visual motion perception.

The cerebellum and language: evidence from patients with cerebellar degeneration

Clinical and imaging studies suggest that the cerebellum is involved in language tasks, but the extent to which slowed language production in cerebellar patients contributes to their poor performance on these tasks is not clear. We explored this relationship in 18 patients with cerebellar degeneration and 16 healthy controls who completed measures of verbal fluency (phonemic and semantic), word stem completion, and oral naming speed. Cerebellar patients showed significantly slower response times when naming common nouns, which correlated with their degree of motor impairment. Patients were significantly impaired on both phonemic and semantic fluency measures compared to controls (p<0.001), even when naming speed was entered as a covariate (p=0.03). On the word stem completion task, patients were significantly less accurate (p<0.001), had more errors due to non-responses (p=0.008), and were slower to respond (p=0.036) than controls; group effects were significant for overall accuracy, but not response time, when the effects of naming speed were covaried (p=0.014). These findings suggest that cerebellar patients' poorer performance on language tasks cannot be explained solely by slower language production, and that the integrity of cerebellar-prefrontal loops might underlie poorer performance on measures of executive function in cerebellar patients.

Slowed orienting of covert visual-spatial attention in autism: Specific deficits associated with cerebellar and parietal abnormality

The most commonly reported finding from structural brain studies in autism is abnormality of the cerebellum. Autopsy and magnetic resonance imaging (MR) studies from nine independent research groups have found developmental abnormality of the cerebellar vermis or hemispheres in the majority of the more than 240 subjects with autism who were studied. We reported previously that patients with autism and those with acquired damage to the cerebellum were slow to shift attention between and within sensory modalities. In this study, we found that patients with autism who come from a group with significant cerebellar abnormality were also slow to orient attention in space.

A subgroup of these patients who have additional or corollary parietal abnormality, like previously studied patients with acquired parietal damage, were also slow to detect and respond to information outside an attended location. Posner, Walker, Friedrich, and Rafal (1984) showed that patients with parietal lesions were slow to respond to contralesional information if they were attending an ipsilesional location. This study has replicated that finding in patients with autism who have developmental bilateral parietal abnormality, and found a strong correlation between the attentional deficits and the amount of neuroanatomic parietal abnormality in these patients. This is the first time in the study of autism that there is evidence for a statistically significant association of the size of a specific brain structural abnormality with a specific behavioral deficit.

These findings illustrate that in autism different patterns of underlying brain pathology may result in different patterns of functional deficits. In conjunction with previous studies of patients with acquired lesions, these data have implications for the brain bases of normal attention. The cerebellum may affect the speed with which attentional resources can be activated, while the parietal cortex affects the ability to use those resources for efficient information processing at locations outside an attended focus. Deficits in the speed and efficiency with which neural activity can be modulated to facilitate processing can clearly influence cognitive function. Such deficits may contribute to the behavioral disabilities that characterize autism.

Differential prefrontal-like deficit in children after cerebellar astrocytoma and medulloblastoma tumor

Background

This study was realized thanks to the collaboration of children and adolescents who had been resected from cerebellar tumors. The medulloblastoma group (CE+, n = 7) in addition to surgery received radiation and chemotherapy. The astrocytoma group (CE, n = 13) did not receive additional treatments. Each clinical group was compared in their executive functioning with a paired control group (n = 12). The performances of the clinical groups with respect to controls were compared considering the tumor's localization (vermis or hemisphere) and the affectation (or not) of the dentate nucleus. Executive variables were correlated with the age at surgery, the time between surgery-evaluation and the resected volume.

Methods

The executive functioning was assessed by means of WCST, Complex Rey Figure, Controlled Oral Word Association Test (letter and animal categories), Digits span (WISC-R verbal scale) and Stroop test. These tests are very sensitive to dorsolateral PFC and/or to medial frontal cortex functions. The scores for the non-verbal Raven IQ were also obtained. Direct scores were corrected by age and transformed in standard scores using normative data. The neuropsychological evaluation was made at 3.25 (SD = 2.74) years from surgery in CE group and at 6.47 (SD = 2.77) in CE+ group.

Results

The Medulloblastoma group showed severe executive deficit (≤ 1.5 SD below normal mean) in all assessed tests, the most severe occurring in vermal patients. The Astrocytoma group also showed executive deficits in digits span, semantic fluency (animal category) and moderate to slight deficit in Stroop (word and colour) tests. In the astrocytoma group, the tumor's localization and dentate affectation showed different profile and level of impairment: moderate to slight for vermal and hemispheric patients respectively. The resected volume, age at surgery and the time between surgery-evaluation correlated with some neuropsychological executive variables.

Conclusion

Results suggest a differential prefrontal-like deficit due to cerebellar lesions and/or cerebellar-frontal diaschisis, as indicate the results in astrocytoma group (without treatments), that also can be generated and/or increased by treatments in the medulloblastoma group. The need for differential rehabilitation strategies for specific clinical groups is remarked. The results are also discussed in the context of the Cerebellar Cognitive Affective Syndrome.

Cerebellar lesion studies of cognitive function in children and adolescents - limitations and negative findings

An increasing number of human lesion and functional brain imaging studies appear to support the hypothesis that the cerebellum contributes to a wide range of non-motor functions, including attention, language and visuospatial functions. Various abnormalities have been reported in standard neuropsychological tests in children and adolescents who have been treated for cerebellar tumors. This review focuses on limitations of lesion studies and negative findings in children and adolescents with focal cerebellar lesions. Frequently cited early findings have not been replicated in later studies or have been explained by motor components of the tasks. Such discrepancies may relate to a number of methodological problems. In addition to impaired motor function, it is unclear to what extent deficits in neuropsychological tests are caused by unspecific effects such as increased intracranial pressure and depression. Effects of extracerebellar lesions are frequently not considered. Although a role of the cerebellum in specific aspects of non-motor functions seems obvious it is still an open question which cognitive functions are involved, why and to what extent. It is a matter of ongoing discussion whether or not cognitive dysfunction belongs to the symptoms of cerebellar disease. Overall, disorders appear to be mild and far less frequent than disorders observed following lesions of cerebral areas. The aim of the review is to demonstrate that many findings frequently cited to support cerebellar involvement in cognition are insufficient to prove the hypothesis. There is ongoing need of well-controlled lesion studies, which show that disorders are due to cerebellar lesions independent of motor dysfunction and other confounding factors.

Cerebellum and Reading

BACKGROUND

Traditionally, the cerebellum has been considered to control coordinated movement. However, in recent years it has been argued that it contributes to higher cognitive functions.

OBJECTIVES

This review aims to present recent evidence concerning the role of the cerebellum and discusses how it can contribute to reading.

METHOD

The procedure used involves findings coming from three quite different areas, lesion, anatomic and functional imaging studies.

RESULTS

These studies indicate a link between cerebellum and reading and its relationship with specific reading difficulties.

CONCLUSIONS

Our review provides evidence which is in accordance with the recently established role of the cerebellum as a regulator of mental functions and supports theoretical models suggesting that cerebellar deficits might be a cause of developmental dyslexia.

N-acetyl aspartate in autism spectrum disorders: regional effects and relationship to fMRI activation

Rapid progress in our understanding of macrostructural abnormalities in autism spectrum disorders (ASD) has occurred in recent years. However, the relationship between the integrity of neural tissue and neural function has not been previously investigated. Single-voxel proton magnetic resonance spectroscopy and functional magnetic resonance imaging of an executive functioning task was obtained in 13 high functioning adolescents and adults with ASD and 13 age-matched controls. The ASD group showed significant reductions in N-acetyl aspartate (NAA) in all brain regions combined and a specific reduction in left frontal cortex compared to controls. Regression analyses revealed a significant group interaction effect between frontal and cerebellar NAA. In addition, a significant positive semi-partial correlation between left frontal lobe NAA and frontal lobe functional activation was found in the ASD group. These findings suggest that widespread neuronal dysfunction is present in high functioning individuals with ASD. Hypothesized developmental links between frontal and cerebellar vermis neural abnormalities were supported, in that impaired neuronal functioning in the vermis was associated with impaired neuronal functioning in the frontal lobes in the ASD group. Furthermore, this study provided the first direct evidence of the relationship between abnormal functional activation in prefrontal cortex and neuronal dysfunction in ASD.

The cerebellum and motor dysfunction in neuropsychiatric disorders

The cerebellum is densely interconnected with sensory-motor areas of the cerebral cortex, and in man, the great expansion of the association areas of cerebral cortex is also paralleled by an expansion of the lateral cerebellar hemispheres. It is therefore likely that these circuits contribute to non-motor cognitive functions, but this is still a controversial issue. One approach is to examine evidence from neuropsychiatric disorders of cerebellar involvement. In this review, we narrow this search to test whether there is evidence of motor dysfunction associated with neuropsychiatric disorders consistent with disruption of cerebellar motor function. While we do find such evidence, especially in autism, schizophrenia and dyslexia, we caution that the restricted set of motor symptoms does not suggest global cerebellar dysfunction. Moreover, these symptoms may also reflect involvement of other, extra-cerebellar circuits and detailed examination of specific sub groups of individuals within each disorder may help to relate such motor symptoms to cerebellar morphology.

Imagerie par résonance magnétique du retard mental non spécifique

Mental retardation is considered idiopathic or not otherwise specified when no etiological diagnosis can be identified in spite of comprehensive history, physical examination and metabolic or genetic investigations. In such cases, brain MRI is indicated for patients with abnormal head size or shape, craniofacial malformation, somatic anomalies, neurocutaneous findings, seizures, focal neurological findings or behavioral and/or developmental problems. Brain anomalies are now considered a main category for the etiology of mental retardation. MRI evaluation should include axial images of the entire brain, sagittal images through the midline structures, and coronal images of the posterior fossa or entire brain. MRI allows detection of major and or minor cerebral anomalies or malformations, sometimes multiple. In the literature, the most frequently involved structures include: 1/ corpus callosum (hypoplasia, short corpus callosum and verticalized splenium), 2/ septum pellucidum (cavum septum pellucidum or cavum vergae), 3/ ventricles (ventriculomegaly), 4/ cerebral cortex (cortical dysplasia), 5/ cerebellum (hypoplasia), and 6/ extra-axial CSF spaces (enlargement). In our patient population, dysplasia involving the cerebellum and vermis have been identified, a finding that has not yet been described in the literature. MRI allows detection of multiple minor morphological anomalies. Most have classically been considered as normal variants but they may in fact be markers of cerebral dysgenesis and are currently the only anomaly detected in the work-up of patients with mental retardation. Their role in the pathogenesis of mental retardation is under evaluation.

Task switching after cerebellar damage

The authors of this study investigated task switching following cerebellar damage. The study group consisted of 7 children and adolescents (M age=13.8 years) who underwent surgical removal of a benign posterior fossa tumor. They were tested at a sufficient interval after surgery (M lag=6.13 years) for restoration of normal cognitive skills and intelligence. Although all showed normal learning of the task compared with control participants, when rapid behavioral changes were required (short preparation time), they exhibited behavioral rigidity manifested by enhanced switching cost. These results are in line with another study on serial reaction time with the same patients (A. Berger et al., in press). They have important implications for our understanding of the cognitive sequelae of early cerebellar damage as well as the involvement of the cerebellum in task switching.

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.

Neuroanatomical markers for dyslexia: a review of dyslexia structural imaging studies

A neuroanatomical description of dyslexia has been elusive, due in part to the complex cognitive nature of dyslexia. People with dyslexia have varying degrees of impairment in reading skills that engage oral and written language (reading) neural networks. Although findings for the inferior parietal lobule, inferior frontal gyrus, and cerebellum have been relatively consistent across studies, these studies also demonstrate that anatomical patterns of results vary according to the reading skills that characterize dyslexia. The number and likelihood of atypical anatomical findings in oral and/or written language systems appears to be related to the pattern of impairments in measures of phonology, orthography, and fluency. A comprehensive neurobiological understanding of dyslexia will depend on studies of dyslexic individuals with homogeneous perceptual, cognitive, and genetic backgrounds.