Cerebellar contributions to cognition

Functional neural substrates of Parkinson's disease and potential underpinnings of acute responses to acupuncture stimulation

Parkinson's disease is a heterogenous neurodegenerative disorder with a wide variety of motor and non-motor symptoms. This study used resting-state fMRI to identify the neural substrates of PD and explore the acute neural response to acupuncture stimulation in 74 participants (50 patients with PD and 24 healthy controls). All participants with PD were evaluated for the severity of symptoms using the Unified Parkinson's Disease Rating Scale and Balance Master. The z-transformed fractional amplitude of low-frequency fluctuation analysis showed significant differences between the PD and healthy controls in the cerebellar regions, which are thought to play a crucial role in PD pathology. Subsequently, seed-based functional connectivity of the cerebellum with the frontal, parietal, and limbic regions was identified as a potential diagnostic marker for PD. In addition, spontaneous neural activity in the precentral gyrus and thalamus was significantly associated with the severity of PD symptoms. Neural activity in the precentral gyrus, precuneus, and superior temporal gyrus showed a significant correlation with Balance Master indicators. Finally, acupuncture stimulation at GB34 significantly reduced the activity of the occipital regions in patients with PD, but this effect was not observed in healthy controls. The mixed-effects analysis revealed an interaction effects between group and acupuncture stimulation, suggesting that the modulatory effects of acupuncture could differ depending on disease status. Therefore, this study suggests the neural substrates of PD and potential underpinnings of acute neural response to acupuncture stimulation.

Dysconnectivity of the cerebellum and somatomotor network correlates with the severity of alogia in chronic schizophrenia

Recent fMRI resting-state findings show aberrant functional connectivity within somatomotor network (SMN) in schizophrenia. Moreover, functional connectivity aberrations of the motor system are often reported to be related to the severity of psychotic symptoms. Thus, it is important to validate those findings and confirm their relationship with psychopathology. Therefore, we decided to take an entirely data-driven approach in our fMRI resting-state study of 30 chronic schizophrenia outpatients and 30 matched control subjects. We used independent component analysis (ICA), dual regression, and seed-based connectivity analysis. We found reduced functional connectivity within SMN in schizophrenia patients compared to controls and SMN hypoconnectivity with the cerebellum in schizophrenia patients. The latter was strongly correlated with the severity of alogia, one of the main psychotic symptoms, i.e. poverty of speech and reduction in spontaneous speech,. Our results are consistent with the recent knowledge about the role of the cerebellum in cognitive functioning and its abnormalities in psychiatric disorders, e.g. schizophrenia. In conclusion, the presented results, for the first time clearly showed the involvement of the cerebellum hypoconnectivity with SMN in the persistence and severity of alogia symptoms in schizophrenia.

The role of cerebellum in the child neuropsychological functioning

This chapter proposes a review of neuropsychologic and behavior findings in pediatric pathologies of the cerebellum, including cerebellar malformations, pediatric ataxias, cerebellar tumors, and other acquired cerebellar injuries during childhood. The chapter also contains reviews of the cerebellar mutism/posterior fossa syndrome, reported cognitive associations with the development of the cerebellum in typically developing children and subjects born preterm, and the role of the cerebellum in neurodevelopmental disorders such as autism spectrum disorders and developmental dyslexia. Cognitive findings in pediatric cerebellar disorders are considered in the context of known cerebellocerebral connections, internal cellular organization of the cerebellum, the idea of a universal cerebellar transform and computational internal models, and the role of the cerebellum in specific cognitive and motor functions, such as working memory, language, timing, or control of eye movements. The chapter closes with a discussion of the strengths and weaknesses of the cognitive affective syndrome as it has been described in children and some conclusions and perspectives.

Regional Brain Gray Matter Changes in Patients with Type 2 Diabetes Mellitus

Patients with Type 2 diabetes mellitus (T2DM) show cognitive and mood impairment, indicating potential for brain injury in regions that control these functions. However, brain tissue integrity in cognition, anxiety, and depression regulatory sites, and their associations with these functional deficits in T2DM subjects remain unclear. We examined gray matter (GM) changes in 34 T2DM and 88 control subjects using high-resolution T1-weighted images, collected from a 3.0-Tesla magnetic resonance imaging scanner, and assessed anxiety [Beck Anxiety Inventory], depressive symptoms [Beck Depression Inventory-II], and cognition [Montreal Cognitive Assessment]. We also investigated relationships between GM status of cognitive and mood control sites and these scores in T2DM. Significantly increased anxiety (p = 0.003) and depression (p = 0.001), and reduced cognition (p = 0.002) appeared in T2DM over controls. Decreased GM volumes appeared in several regions in T2DM patients, including the prefrontal, hippocampus, amygdala, insular, cingulate, cerebellum, caudate, basal-forebrain, and thalamus areas (p < 0.01). GM volumes were significantly associated with anxiety (r = -0.456,p = 0.009), depression (r = -0.465,p = 0.01), and cognition (r = 0.455,p = 0.009) scores in regions associated with those regulations (prefrontal cortices, hippocampus, para hippocampus, amygdala, insula, cingulate, caudate, thalamus, and cerebellum) in T2DM patients. Patients with T2DM show brain damage in regions that are involved in cognition, anxiety, and depression control, and these tissue alterations are associated with functional deficits. The findings indicate that mood and cognitive deficits in T2DM patients has brain structural basis in the condition.

Synergistic excitability plasticity in cerebellar functioning

The cerebellum, a universal processor for sensory acquisition and internal models, and its association with synaptic and nonsynaptic plasticity have been envisioned as the biological correlates of learning, perception, and even thought. Indeed, the cerebellum is no longer considered merely as the locus of motor coordination and its learning. Here, we introduce the mechanisms underlying the induction of multiple types of plasticity in cerebellar circuit and give an overview focusing on the plasticity of nonsynaptic intrinsic excitability. The discovery of long-term potentiation of synaptic responsiveness in hippocampal neurons led investigations into changes of their intrinsic excitability. This activity-dependent potentiation of neuronal excitability is distinct from that of synaptic efficacy. Systematic examination of excitability plasticity has indicated that the modulation of various types of Ca²⁺ - and voltage-dependent K⁺ channels underlies the phenomenon, which is also triggered by immune activity. Intrinsic plasticity is expressed specifically on dendrites and modifies the integrative processing and filtering effect. In Purkinje cells, modulation of the discordance of synaptic current on soma and dendrite suggested a novel type of cellular learning mechanism. This property enables a plausible synergy between synaptic efficacy and intrinsic excitability, by amplifying electrical conductivity and influencing the polarity of bidirectional synaptic plasticity. Furthermore, the induction of intrinsic plasticity in the cerebellum correlates with motor performance and cognitive processes, through functional connections from the cerebellar nuclei to neocortex and associated regions: for example, thalamus and midbrain. Taken together, recent advances in neuroscience have begun to shed light on the complex functioning of nonsynaptic excitability and the synergy.

Cerebellar Contribution to Motor and Non-motor Functions in Parkinson's Disease: A Meta-Analysis of fMRI Findings

Background: Parkinson's disease (PD) results in both motor and non-motor symptoms. Traditionally, the underlying mechanism of PD has been linked to neurodegeneration of the basal ganglia. Yet it does not adequately account for the non-motor symptoms of the disease, suggesting that other brain regions may be involved. One such region is the cerebellum, which is known to be involved, together with the basal ganglia, in both motor and non-motor functions. Many studies have found the cerebellum to be hyperactive in PD patients, a finding that is seldom discussed in detail, and warrants further examination. The current study thus aims to examine quantitively the current literature on the cerebellar involvement in both motor and non-motor functioning in PD. Methods: A meta-analysis of functional neuroimaging literature was conducted with Seed-based D mapping. Only the studies testing functional activation in response to motor and non-motor paradigms in PD and healthy controls (HC) were included in the meta-analysis. Separate analyses were conducted by including only studies with non-motor paradigms, as well as meta-regressions with UPDRS III scores and disease duration. Results: A total of 57 studies with both motor and non-motor paradigms fulfilled our inclusion criteria and were included in the meta-analysis, which revealed hyperactivity in Crus I-II and vermal III in PD patients compared to HC. An analysis including only studies with cognitive paradigms revealed a cluster of increased activity in PD patients encompassing lobule VIIB and VIII. Another meta-analysis including the only 20 studies that employed motor paradigms did not reveal any significant group differences. However, a descriptive analysis of these studies revealed that 60% of them reported cerebellar hyperactivations in PD and included motor paradigm with significant cognitive task demands, as opposed to 40% presenting the opposite pattern and using mainly force grip tasks. The meta-regression with UPDRS III scores found a negative association between motor scores and activation in lobule VI and vermal VII-VIII. No correlation was found with disease duration. Discussion: The present findings suggest that one of the main cerebellar implications in PD is linked to cognitive functioning. The negative association between UPDRS scores and activation in regions implicated in motor functioning indicate that there is less involvement of these areas as the disease severity increases. In contrast, the lack of correlation with disease duration seems to indicate that the cerebellar activity may be a compensatory mechanism to the dysfunctional basal ganglia, where certain sub-regions of the cerebellum are employed to cope with motor demands. Yet future longitudinal studies are needed to fully address this possibility.

Cerebellar volume deficits in medication-naïve obsessive compulsive disorder

Even though conventional neurobiological models of obsessive compulsive disorder (OCD) commonly demonstrate abnormalities involving fronto-striatal circuits, there is emerging evidence regarding the role of posterior brain structures such as cerebellum. In this study, we examined the cerebellar regional volume in a large sample of medication-naïve OCD patients compared to matched healthy controls (HC). In 49 medication naïve right handed OCD patients and 39 age and sex matched HC, sub-region wise volume of cerebellum was extracted from the T1 weighted images using Spatially Unbiased Infra tentorial Template (SUIT) toolbox and compared using hypothesis driven, region of interest approach after clinical assessment with standard scales. After controlling for age, sex and ICV, the subjects with OCD had significantly smaller cerebellum compared to HC, especially in the posterior lobe sub-regions - lobule VI and left crus 1. This study gives preliminary evidence for region specific cerebellar volumetric deficits in the pathophysiological of OCD. Regional cerebellar volume deficits conform to the abnormal connectivity of cerebellum to specific cortical regions and it is indicative of involvement of regions outside the conventional fronto-striatal circuitry. This might be important in the context of cognitive deficits seen in OCD.

Decoding the processing of lying using functional connectivity MRI

Background

Previous functional MRI (fMRI) studies have demonstrated group differences in brain activity between deceptive and honest responses. The functional connectivity network related to lie-telling remains largely uncharacterized.

Methods

In this study, we designed a lie-telling experiment that emphasized strategy devising. Thirty-two subjects underwent fMRI while responding to questions in a truthful, inverse, or deceitful manner. For each subject, whole-brain functional connectivity networks were constructed from correlations among brain regions for the lie-telling and truth-telling conditions. Then, a multivariate pattern analysis approach was used to distinguish lie-telling from truth-telling based on the functional connectivity networks.

Results

The classification results demonstrated that lie-telling could be differentiated from truth-telling with an accuracy of 82.81% (85.94% for lie-telling, 79.69% for truth-telling). The connectivities related to the fronto-parietal networks, cerebellum and cingulo-opercular networks are most discriminating, implying crucial roles for these three networks in the processing of deception.

Conclusions

The current study may shed new light on the neural pattern of deception from a functional integration viewpoint.

Electronic supplementary material

The online version of this article (doi:10.1186/s12993-014-0046-4) contains supplementary material, which is available to authorized users.

Language impairment in cerebellar ataxia

BACKGROUND

Several studies have suggested that language impairment can be observed in patients with cerebellar pathology. The aim of this study was to investigate language performance in patients with spinocerebellar ataxia type 6 (SCA6).

METHODS

We assessed speech and language in 29 SCA6 patients with standardized linquistic tests and correlated this with the severity of ataxia, as quantified by the Scale of Assessment and Rating of Ataxia.

RESULTS

Individual patients show mild-to-moderate linguistic impairment. Linguistic abnormalities were most distinct on the writing and comprehension subtests. A strong correlation between severity of ataxia and linguistic performance was consistently found.

CONCLUSIONS

This study confirms the occurrence of linguistic impairments in patients with cerebellar degenerative diseases, such as SCA6. The relation between linguistic abnormalities and severity of ataxia provides further evidence for a role of the cerebellum in linguistic processing.

Localization of cerebral functional deficits in patients with obsessive-compulsive disorder: a resting-state fMRI study

BACKGROUND

Abnormality of orbitofronto-striatal circuits was postulated in obsessive-compulsive disorder (OCD). The aim of this study is to test the abnormality hypothesis of orbitofronto-striatal circuits and explore whether there are any other dysfunctional brain regions in OCD using a resting-state functional magnetic resonance imaging (fMRI), and further investigate the relationship between the whole-brain voxel-based spontaneous neuronal activity of patients with OCD and clinical characteristics.

METHODS

23 patients with OCD and 23 age- and gender-matched normal controls were examined using resting-state fMRI, and amplitude of low-frequency fluctuation (ALFF) approach was used to analyze fMRI data.

RESULTS

Compared with normal controls, patients with OCD presented increased ALFF in the bilateral orbitofrontal cortex (OFC), anterior cingulate cortex (ACC) as well as decreased ALFF in the bilateral cerebellum and parietal cortex (P<0.01, corrected). Additionally, the ALFF values in bilateral OFC were positively correlated with total Y-BOCS scores (P<0.005, uncorrected).

CONCLUSION

Our findings added an expanding literature to the abnormality hypothesis of orbitofronto-striatal circuits and showed the changed spontaneous neuronal activity of the parietal cortex and cerebellum may also play an important role in the pathophysiology in patients with OCD.

Neuropsychological Outcomes of Children Treated for Posterior Fossa Tumours:A Review

The posterior fossa region of the brain is a frequent site for tumour development in children, with over half of all childhood tumours occurring at this site. The principal brain structure implicated at this site is the cerebellum. Children treated for posterior fossa tumours can have a wide range of neurological and psychosocial problems. This paper describes the literature to date that addresses the neuropsychological impact of tumour and treatment in children with posterior fossa tumours. This paper reviews the literature on the causes of morbidity in this group. It discusses the recent research on the role of the cerebellum in outcomes and the studies that identify variables that interact with radiation effects.

A novel mutation in CACNA1A associated with hemiplegic migraine, cerebellar dysfunction and late-onset cognitive decline

Hemiplegic migraine (HM) is a rare and severe subtype of migraine with aura, characterized by some degree of hemiparesis and other aura symptoms. Mutations in three genes (CACNA1A, ATP1A2 and SCN1A) have been detected in familial and, more rarely, in sporadic cases. The disease can be complicated by permanent neurological deficits, the most frequent one being a cerebellar syndrome; in addition, mental retardation has been recognized as part of the phenotypic spectrum. Here, we report a Caucasian male with a novel CACNA1A mutation and an unusual clinical phenotype: the patient, who had had a history of only two HM attacks, sought medical advice at age 49 primarily because of increasing cognitive decline accompanied by cerebellar dysfunction. While common neurodegenerative causes were excluded, neuropsychological evaluation revealed a distinct profile of deficits of a subcortico-prefrontal type as previously reported in patients with cerebellar dysfunction. This suggests a possible causal link between cerebellar and cognitive disturbances in this patient; in addition to these pathophysiological aspects, we review of the role of the cerebellum in cognition.

Preoperative and postoperative neurological, neuropsychological and behavioral impairment in children with posterior cranial fossa astrocytomas and medulloblastomas: the role of the tumor and the impact of the surgical treatment

INTRODUCTION

The aim of the present study was to prospectively investigate if a correlation might exist between preoperative and postoperative neurological conditions, neuroradiological/intraoperative findings and results of a complete neuropsychological evaluation in children with posterior fossa medulloblastomas and astrocytomas.

MATERIALS AND METHODS

Of the 65 children admitted at the Pediatric Neurosurgery of the UCSC of Rome between January 2005 and October 2009, 41 were selected; the only two exclusion criteria were represented by age under 24 months and severe neurological conditions, seen that in both cases it would not have been a possible reliable evaluation. All children underwent a preoperative and immediate postoperative complete MR study. Hydrocephalus was graded on the Evans score; brainstem infiltration was defined on intraoperative findings. Neuropsychological assessment consisted of a battery of tests tailored on the patient's age, cognitive level, and level of cooperation. Post operative neuropsychological evaluation was performed at a mean time of 2.5 min (2 mos, max 4.5 mos) from the operation, before any eventually needed adjuvant treatment (i.e., chemotherapy, radiotherapy).

RESULTS

Concerning neurological status, we found a statistically significant relation between the presence of oculomotor impairment and both verbal fluency deficits (p = 0.044) and imagery disorders (p = 0.03); also, the presence of ataxia/dysmetria was significantly correlated to attention dysfunction (p = 0.01) and, more tightly, to planning dysfunction (p = 0.006). For neuroradiological/intraoperative features, Intelligence Quotient (IQ) impairment was significantly correlated to the intraoperative evidence of tumor infiltration of the brainstem (p = 0.003), a severe hydrocephalus at diagnosis (p = 0.001) and the histological diagnosis of medulloblastoma (MB) (p = 0.002). For selective skills, a significant correlation was found between linguistic processing deficits and the evidence of dentate nuclei infiltration (blindly defined on MR); procedural memory defects and imagery disorders related to the severity of the hydrocephalus (p = 0.02), infiltration of the brain stem (p = 0.01) and a histological diagnosis of MB (p = 0.01). After surgery no patient showed a worsening of his/her cognitive profile; the relationships between clinical, intraoperative, and radiological findings were substantially confirmed.

DISCUSSION

Our results support the hypothesis that when present, neuropsychological impairment is already present at diagnosis and that the most statistically significant factors, which might be related with cognitive deficits in the preoperative as well as in the postoperative period, are tumor infiltration of the brainstem, the severity of hydrocephalus, and a histological diagnosis of MB.

Cognitive deficits and associated neurological complications in individuals with Down's syndrome

Improvements in medical interventions for people with Down's syndrome have led to a substantial increase in their longevity. Diagnosis and treatment of neurological complications are important in maintaining optimal cognitive functioning. The cognitive phenotype in Down's syndrome is characterised by impairments in morphosyntax, verbal short-term memory, and explicit long-term memory. However, visuospatial short-term memory, associative learning, and implicit long-term memory functions are preserved. Seizures are associated with cognitive decline and seem to cause additional decline in cognitive functioning, particularly in people with Down's syndrome and comorbid disorders such as autism. Vision and hearing disorders as well as hypothyroidism can negatively impact cognitive functioning in people with Down's syndrome. Dementia that resembles Alzheimer's disease is common in adults with Down's syndrome. Early-onset dementia in adults with Down's syndrome does not seem to be associated with atherosclerotic complications.

The cerebellum and language: the story so far

BACKGROUND

The cerebellum was traditionally considered to be exclusively involved in the coordination of voluntary movement, gait, posture, balance and motor speech. However, this view was challenged by recent neuroanatomical, neuroimaging and clinical findings, providing preliminary evidence of a cerebellar contribution to linguistic functioning.

AIM

To discuss the role of the cerebellum in a variety of linguistic functions and to explore the underlying mechanisms.

METHODS

A literature search was conducted via electronic databases. Exclusion criteria were: disorders following congenital cerebellar lesions, motor speech disorders, cognitive deficits outside the language sphere, neuropsychiatric disorders and insufficient information on the cerebellar role in language. Abstracts were not included. In addition, only adult subjects were taken into consideration.

RESULTS

A variety of linguistic disorders were found to occur following acquired cerebellar lesions: (1) impaired phonological and semantic fluency; (2) agrammatism (at morphological and sentence level); (3) naming and word finding difficulties; (4) cerebellar-induced aphasia; (5) reading difficulties; (6) writing problems, and (7) higher-level language deficits, including disturbed listening comprehension, impaired language proficiency and metalinguistic ability. Several hypotheses have been suggested to explain the nature of the cerebellar contribution to language. However, findings are not univocal.

CONCLUSION

The cerebellum appears to be involved in a variety of linguistic functions. However, the precise nature of this contribution is not clear yet. Linguistic, neuroimaging, neuroanatomical and neuropsychological studies should be combined in order to disentangle the specific contribution of the cerebellum to linguistic processing.

Brain morphometry and cognitive performance in detoxified alcohol-dependents with preserved psychosocial functioning

The extent of structural brain damage and related cognitive deficits has been little described in alcohol-dependent individuals with preserved social functioning. Thus, we investigated the relationship between regional alterations, executive performance, and drinking history. Volumes of gray and white matter were assessed using magnetic resonance imaging voxel-based morphometry in healthy men and in detoxified alcohol-dependent men with good psychosocial functioning. Their executive performance was assessed using neuropsychological tests. Regression analyses were carried out in the regions in which volume differences were detected. Decreases in gray matter were detected bilaterally in alcohol-dependents in the dorsolateral frontal cortex (up to 20% lower), and to a lesser extent in the temporal cortex, insula, thalamus, and cerebellum. Decreases in white matter volume were widespread, being up to 10% in corpus callosum. The degradation of neuropsychological performance correlated with gray matter volume decreases in the frontal lobe, insula, hippocampus, thalami and cerebellum, and with white matter decrease in the brainstem. An early age at first drinking was associated with decreased gray matter volumes in the cerebellum, brainstem (pons), and frontal regions. Regional alteration in gray and white matter volume was associated with impairment of executive function despite preserved social and somatic functioning in detoxified patients. Besides involving frontal regions, these findings are consistent with a cerebello-thalamo-cortical model of impaired executive functions in alcohol-dependent individuals.

The mixed-lineage leukemia fusion partner AF4 stimulates RNA polymerase II transcriptional elongation and mediates coordinated chromatin remodeling

AF4 gene, frequently translocated with mixed-lineage leukemia (MLL) in childhood acute leukemia, encodes a putative transcriptional activator of the AF4/LAF4/FMR2 (ALF) protein family previously implicated in lymphopoiesis and Purkinje cell function in the cerebellum. Here, we provide the first evidence for a direct role of AF4 in the regulation of transcriptional elongation by RNA polymerase II (Pol II). We demonstrate that mouse Af4 functions as a positive regulator of Pol II transcription elongation factor b (P-TEFb) kinase and, in complex with MLL fusion partners Af9, Enl and Af10, as a mediator of histone H3-K79 methylation by recruiting Dot1 to elongating Pol II. These pathways are interconnected and tightly regulated by the P-TEFb-dependent phosphorylation of Af4, Af9 and Enl which controls their transactivation activity and/or protein stability. Consistently, increased levels of phosphorylated Pol II and methylated H3-K79 are observed in the ataxic mouse mutant robotic, an over-expression model of Af4. Finally, we confirm the functional relevance of Af4, Enl and Af9 to the regulation of gene transcription as their over-expression strongly stimulates P-TEFb-dependent transcription of a luciferase reporter gene. Our findings uncover a central role for these proteins in the regulation of transcriptional elongation and coordinated histone methylation, providing valuable insight into their contribution to leukemogenesis and neurodegeneration. Since these activities likely extend to the entire ALF protein family, this study also significantly inputs our understanding of the molecular basis of FRAXE mental retardation syndrome in which FMR2 expression is silenced.

Cognitive function in multiple system atrophy of the cerebellar type

Dementia represents an exclusion criterion for the diagnosis of multiple system atrophy (MSA), but there have been reports of fronto-executive dysfunction in patients with MSA of the striatonigral type (MSA-P). To study the cognitive profile of MSA, 20 patients with MSA of the cerebellar type (MSA-C) were subjected to an extensive neuropsychological test battery comprising tests for IQ, attention, verbal and visuospatial memory, as well as executive function. There was evidence for impaired verbal memory and verbal fluency. Test performance was not related to the severity of motor disability. Regarding the similar cognitive syndrome of MSA-P, the otherwise subclinical problems in MSA-C result from subcortical rather than from cerebellar dysfunction.

Injury severity determines Purkinje cell loss and microglial activation in the cerebellum after cortical contusion injury

Clinical evidence suggests that the cerebellum is damaged after traumatic brain injury (TBI) and experimental studies have validated these observations. We have previously shown cerebellar vulnerability, as demonstrated by Purkinje cell loss and microglial activation, after fluid percussion brain injury. In this study, we examine the effect of graded controlled cortical impact (CCI) injury on the cerebellum in the context of physiologic and anatomical parameters that have been shown by others to be sensitive to injury severity. Adult male rats received mild, moderate, or severe CCI and were euthanized 7 days later. We first validated the severity of the initial injury using physiologic criteria, including apnea and blood pressure, during the immediate postinjury period. Increasing injury severity was associated with an increased incidence of apnea and higher mortality. Severe injury also induced transient hypertension followed by hypotension, while lower grade injuries produced an immediate and sustained hypotension. We next evaluated the pattern of subcortical neuronal loss in response to graded injuries. There was significant neuronal loss in the ipsilateral cortex, hippocampal CA2/CA3, and laterodorsal thalamus that was injury severity-dependent and that paralleled microglial activation. Similarly, there was a distinctive pattern of Purkinje cell loss and microglial activation in the cerebellar vermis that varied with injury severity. Together, these findings emphasize the vulnerability of the cerebellum to TBI. That a selective pattern of Purkinje cell loss occurs regardless of the type of injury suggests a generalized response that is a likely determinant of recovery and a target for therapeutic intervention.

Verb generation in children and adolescents with acute cerebellar lesions

The aim of the present study was to examine verb generation in a larger group of children and adolescents with acute focal lesions of the cerebellum. Nine children and adolescents with cerebellar tumours participated. Subjects were tested a few days after tumour surgery. For comparison, a subgroup was tested also 1 or 2 days before surgery. None of the children had received radiation or chemotherapy at or before the time of testing. Eleven age- and education-matched control subjects participated. Subjects had to generate verbs to blocked presentations of photographs of objects. As control condition, the objects had to be named. Furthermore, dysarthria was quantified by means of a sentence production and syllable repetition task. Detailed analysis of individual 3D-MR images revealed that lesions affected cerebellar hemispheres in all children and adolescents. The right cerebellar hemisphere was affected in four and the left hemisphere in five subjects. In the present study, naming and verb generation accuracy were preserved in the majority of subjects with cerebellar lesions. No significant signs of learning deficits were observed, as reduction of reaction times over blocks was not different compared to controls. There was a trend of children and adolescents with right-hemispheric lesions to perform worse compared to controls. In this group, however, significant signs of dysarthria were present. In sum, no significant signs of disordered verb generation were observed in children and adolescents with acute cerebellar lesions. Findings suggest that the role of the cerebellum in verb generation may be less pronounced than previously suggested. Findings need to be confirmed in a larger group of subjects with acute focal lesions.

Mental retardation and epilepsy in patients with isolated cerebellar hypoplasia

Congenital nonprogressive cerebellar ataxia includes a complex group of disorders with heterogeneous phenotypic and etiopathogenetic characteristics. Despite recent advances in the understanding of the role of the cerebellum in cognition and behavior, the opinion that the clinical presentation of congenital cerebellar diseases is principally linked to motor dysfunction is common. This is largely due to the lack of well-organized epidemiologic studies on the prevalence of nonmotor disturbances in cerebellar disease. The association between congenital cerebellar disease and epilepsy has rarely been described. We report clinical, neurophysiologic, neuroimaging, and neuropsychologic features in a group of 14 patients with congenital nonprogressive cerebellar ataxia associated with cerebellar hypoplasia, 5 of whom have familial disease, aiming to further a better knowledge of the prevalence of cognitive and/or emotional impairment and epilepsy. The results confirm that cerebellar hypoplasia predisposes individuals to psychomotor delay (71.4%) and cognitive impairment (85.7%). Moreover, the tendency toward abnormal electroencephalographic (EEG) findings (78.5%), associated in a minor percentage of cases with epilepsy (28.5%), is also evident in our study.

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.

Elevated expression of the G-protein-activated inwardly rectifying potassium channel 2 (GIRK2) in cerebellar unipolar brush cells of a Down syndrome mouse model

1. Down syndrome (DS) arises from the presence of three copies of chromosome (Chr.) 21. Fine motor learning deficits found in DS from childhood to adulthood result from expression of extra genes on Chr. 21, however, it remains unclear which if any of these genes are the specific causes of the cognitive and motor dysfunction. DS cerebellum displays morphological abnormalities that likely contribute to the DS motor phenotype. 2. The G-protein-activated inwardly rectifying potassium channel subunit 2 (GIRK2) is expressed in cerebellum and can shunt dendritic conductance and attenuate postsynaptic potentials. We have used an interbreeding approach to cross a genetic mouse model of DS (Ts65Dn) with Girk2 knockout mice and examined its relative expression level by quantitative real-time RT-PCR, Western blotting and immunohistochemistry. 3. We report here for the first time that GIRK2 is expressed in unipolar brush cells, which are excitatory interneurons of the vestibulocerebellum and dorsal cochlear nucleus. Analysis of disomic-Ts65Dn/Girk2((+/+/-)) and heterozygous-Diploid/Girk2((+/-)) mice shows that GIRK2 expression in Ts65Dn lobule X follows gene dosage. The lobule X of Ts65Dn mice contain greater numbers of unipolar brush cells co-expressing GIRK2 and calretinin than the control mouse groups. 4. These results demonstrate that gene triplication can impact specific cell types in the cerebellum. We hypothesize that GIRK2 overexpression will adversely affect cerebellar circuitry in Ts65Dn vestibulocerebellum and dorsal cochlear nucleus due to GIRK2 shunting properties and its effects on resting membrane potential.

Subtle cognitive deficits after cerebellar infarcts

The role of the cerebellum in cognitive functions has been under debate. We investigated the neuropsychological functioning of patients with cerebellar lesions (infarcts) and evaluated the significance of laterality in cognitive symptoms. Twenty-six patients with exclusive cerebellar lesions as verified by clinical and neuroradiological findings underwent a neuropsychological assessment at the acute stage and at 3 months. Their performance was compared with 14 controls, also assessed twice. The focus was on four domains: visuospatial/motor functions, episodic memory, working memory and attentional shifting/execution. Both groups improved over time. Statistical differences emerged in tests in the visuomotor domain as well as in the episodic and working memory domains. Patients with left cerebellar lesion were slow in a visuospatial task, whereas those with right cerebellar lesions had verbal memory difficulty compared with controls. By 3 months, 77% of the patients had returned to work, and only one had cognitive impairment and did not return to work. Our results indicate that cerebellar infarcts may result in subtle cognitive changes perhaps primarily related to working memory deficit. The symptoms may be mediated by the contralateral cortical hemisphere, left cerebellar infarcts producing mild right hemispheral dysfunction and right cerebellar infarct producing mild left hemispheral dysfunction.

Cerebellar damage produces selective deficits in verbal working memory

The cerebellum is often active in imaging studies of verbal working memory, consistent with a putative role in articulatory rehearsal. While patients with cerebellar damage occasionally exhibit a mild impairment on standard neuropsychological tests of working memory, these tests are not diagnostic for exploring these processes in detail. The current study was designed to determine whether damage to the cerebellum is associated with impairments on a range of verbal working memory tasks, and if so, under what circumstances. Moreover, we assessed the hypothesis that these impairments are related to impaired rehearsal mechanisms. Patients with damage to the cerebellum (n = 15) exhibited a selective deficit in verbal working memory: spatial forward and backward spans were normal, but forward and backward verbal spans were lower than controls. While the differences were significant, digit spans were relatively preserved, especially in comparison to the dramatic reductions typically observed in classic 'short-term memory' patients with perisylvian brain damage. The patients tended to be more impaired on a verbal version compared to a spatial version of a working memory task with a long delay and this impairment was correlated with overall symptom and dysarthria severity. These results are consistent with a contribution of the cerebellum to rehearsal and suggest that inclusion of a delay before recall is especially detrimental in individuals with cerebellar damage. However, when we examined markers of rehearsal (i.e. word-length and articulatory suppression effects) in an immediate serial recall task, we found that qualitative aspects of the patients' rehearsal strategies were unaffected. We propose that the cerebellum may contribute to verbal working memory during the initial phonological encoding and/or by strengthening memory traces rather than by fundamentally subserving covert articulatory rehearsal.

Disturbed overt but normal covert shifts of attention in adult cerebellar patients

In an attempt to provide a common denominator for cognitive deficits observed in cerebellar patients, it has been suggested that they might be secondary to impaired control of attention, a 'dysmetria of attention', conceptually analogous to motor dysmetria. Albeit appealing and quite influential, the concept of attentional dysmetria as a consequence of cerebellar disease remains controversial. In an attempt to test this concept in a direct way, we compared the performance of patients with cerebellar disorders to that of normal controls on tasks requiring either overt or covert shifts of spatial attention. In the first experiment, visually guided saccades, i.e. overt shifts of spatial attention, were elicited. In the second experiment, covert shifts of attention were evoked by the need to discriminate the orientation of a Landolt C observed during controlled fixation and presented in the same locations as the saccade targets in the previous experiment. The allocation of attention was assessed by comparing acuity thresholds determined with and without spatial cueing. The patients exhibited dysmetric saccades as reflected by larger absolute position errors or a higher number of corrective saccades compared to controls. In contrast, the ability to shift attention covertly was unimpaired in the patients, as indicated by a robust improvement in visual acuity induced by spatial cueing which did not differ from the one observed in the controls and which was independent of the range of SOAs (stimulus onset asynchronies) tested. Finally, the individual amount of saccadic dysmetria did not correlate with the individual performance in the covert attentional paradigm. In summary, we conclude that the contributions of the cerebellum to attention are confined to overt manifestations based on goal-directed eye movements.

Crossed cerebro-cerebellar language dominance

In addition to its traditional role in motor control, the cerebellum has been implicated in various cognitive and linguistic functions. Lesion, anatomic, and functional imaging studies indicate a link between left frontal language regions and the right cerebellum. To probe the specificity of this circuit, we examined the association between language-related lateralized activation of the frontal cortex with lateralized activation of the cerebellum. Functional magnetic resonance imaging (fMRI) was carried out during letter-cued word generation in 14 healthy subjects: 7 subjects displayed typical left-hemisphere and 7 subjects displayed atypical right-hemisphere language dominance. We found activation of the cerebellar hemisphere contralateral to the language-dominant cerebral hemisphere in each subject. The cerebellar activation was confined to the lateral posterior cerebellar hemisphere (lobule VI, VII B, Cr I, Cr II). This study demonstrates that crossed cerebral and cerebellar language dominance is a typical characteristic of brain organization. The functional significance of the reported activations can now be tested in patients with lesions of the lateral posterior cerebellum.

Behavioral and affective changes in children and adolescents with chronic cerebellar lesions

The aim of the present study was to investigate if clinically relevant affective or behavioral changes as described in adults in the cerebellar affective syndrome by Schmahmann and Sherman [The cerebellar cognitive affective syndrome, Brain 121 (1998) 561-579] are likely to occur as a long-term sequelae of cerebellar vermis lesions in children. Site and extent of the vermal lesion were defined on the basis of individual 3D-MRI scans and lesion data were correlated with behavioral and affective changes. Affect and behavior were assessed in children after cerebellar tumor surgery by means of experimenter ratings based on the description of the cerebellar affective syndrome and free ratings by the patients and their parents. Twelve children and adolescents with a former cerebellar astrocytoma surgery without subsequent radiation or chemotherapy participated. Detailed analysis of individual 3D-MR images revealed that lesions affected the vermis in nine children. Experimenter ratings according to Schmahmann revealed no relevant problems in patients. In five out of nine patients with vermal affection somewhat increased thoughtful, anxious or aggressive behavior was reported by patients and parents. In conclusion, minor behavioral and affective changes were present in a subset of children with chronic vermal lesions.

The robotic mouse: unravelling the function of AF4 in the cerebellum

The devastating nature and lack of effective treatments associated with neurodegenerative diseases have stimulated a world-wide search for the elucidation of their molecular basis to which mouse models have made a major contribution. In combination with transgenic and knockout technologies, large-scale mouse mutagenesis is a powerful approach for the identification of new genes and associated signalling pathways controlling neuronal cell death and survival. Here we review the characterization of the robotic mouse, a novel model of autosomal dominant cerebellar ataxia isolated from an ENU-mutagenesis programme, which develops adult-onset region-specific Purkinje cell loss and cataracts, and displays defects in early T-cell maturation and general growth retardation. The mutated protein, Af4, is a member of the AF4/LAF4/FMR2 (ALF) family of putative transcription factors previously implicated in childhood leukaemia and FRAXE mental retardation. The mutation, which lies in a highly conserved region among the ALF family members, significantly reduces the binding affinity of Af4 to the E3 ubiquitin-ligase Siah-1a, isolated with Siah-2 as interacting proteins in the brain. This leads to a markedly slower turnover of mutant Af4 by the ubiquitin-proteasome pathway and consequently to its abnormal accumulation in the robotic mouse. Importantly, the conservation of the Siah-binding domain of Af4 in all other family members reveals that Siah-mediated proteasomal degradation is a common regulatory mechanism that controls the levels, and thereby the function, of the ALF family. The robotic mouse represents a unique model in which to study the newly revealed role of Af4 in the maintenance of vital functions of Purkinje cells in the cerebellum and further the understanding of its implication in lymphopoeisis.

A pilot study of preirradiation chemotherapy and 1800 cGy craniospinal irradiation in young children with medulloblastoma

PURPOSE

Craniospinal irradiation (CSI) is necessary in the treatment of medulloblastoma, although it results in significant long-term sequelae, particularly in young children. We prospectively evaluated the feasibility of giving preirradiation chemotherapy followed by 1800 cGy CSI to young children with localized medulloblastoma.

METHODS AND MATERIALS

Between January 1993 and July 1997, 7 consecutive patients (age, 20-64 months) with M0 medulloblastoma were enrolled. After surgical resection, patients received 4 months of multiagent chemotherapy followed by 1800 cGy CSI and 5400 cGy to the posterior fossa.

RESULTS

Median follow-up is 8.9 years. No patient developed progressive disease during chemotherapy. One patient developed widespread metastatic recurrence 2 months after completing radiation therapy and died. Two additional patients developed isolated frontal horn relapses 32 and 36 months after initial diagnosis and received further irradiation and chemotherapy. Both of these patients remain alive 7.1 and 3.6 years from the time of recurrence. Four of the six survivors have endocrine deficits. All of the survivors require special assistance in school.

CONCLUSIONS

Craniospinal irradiation doses of 1800 cGy may not be adequate to prevent exoprimary recurrences. Despite the CSI dose reduction, neuroendocrine and neurocognitive sequelae are substantial.

Preserved verb generation in patients with cerebellar atrophy

A role of the right cerebellar hemisphere has been suggested in linguistic functions. Nevertheless, studies of verb generation in cerebellar patients provide inconsistent results. The aim of the present study was to examine verb generation in a larger group of cerebellar patients with well-defined lesions. Ten subjects with degenerative cerebellar disorders and ten healthy matched controls participated. Subjects had to generate verbs to the blocked presentation of photographs of objects (i.e. four blocks of sixteen objects). As control condition, the objects had to be named. Furthermore, dysarthria was quantified by means of a sentence production and syllable repetition task. Volumetric analysis of individual 3D-MR scans was performed to quantify cerebellar atrophy. Cerebellar patients were slower in the sentence production and syllable repetition tasks, and cerebellar volume was decreased compared to controls. Despite cerebellar atrophy and dysarthria, the answers produced did not differ between patients and controls. In addition, both groups revealed the same amount of decrease in verbal reaction time over blocks (i.e. learning). The results suggest that the role of the cerebellum in verb generation is less pronounced than previously suggested.

A critical review of the clinical effects of therapeutic irradiation damage to the brain: the roots of controversy

We critically examined the damaging affects of therapeutic irradiation by comparing results from cross-disciplinary studies of early- and late-delayed radiotherapy effects. Focus is attained by concentrating on clinical treatment issues (volume of brain, dose, timing of effects, age, modality types, and stereotactic treatment techniques), rather than on methodological means or problems, which is necessary to understand the mechanisms and characteristics of radiotherapy-induced behavioral dysfunction including cognition. We make observations and hypotheses about the actual risks from radiotherapy that could be informative in the treatment decision process, and which may lessen the concerns of some patients and their families about the risks they take when receiving radiation. Conditions that predispose to radiation injury are reviewed: (1) higher doses even to part of the brain versus lower doses to the whole brain, (2) combined treatment modalities, (3) malignancy itself, (4) radiation early during postnatal brain development, and (5) late-delayed effects (more than 3 years posttreatment). Current neurocognitive frameworks for understanding cognitive change over time in children and adults are summarized, along with the literature on effects of brain tumors and treatment on depression. No studies have as yet identified candidate brain regions that are more sensitive to radiotherapy. Two studies have provided early, preliminary evidence for a specific vulnerability of visual attention/memory to the early stage of late radiation damage. Furthermore, radiation effects appear severe only in a minority of patients. Risk is related to direct and indirect effects of cancer type, concurrent clinical factors, and premorbid risk factors.

Stimulus-response versus stimulus-stimulus-response learning in cerebellar patients

Ample evidence exists that the cerebellum is involved in associative motor learning, particularly in eyeblink-conditioning. In visuomotor associative learning the role of the cerebellum is less clear. One open question is whether cerebellar patients' deficits in visuomotor learning are present both in a stimulus-response and a stimulus-stimulus-response association task. Twelve patients with cerebellar degeneration and 12 healthy matched control subjects participated. A magnetic resonance imaging (MRI) volumetric analysis of the cerebellum was performed to assess the degree of cerebellar atrophy. In a blocked design, subjects had to learn the association between one color square or two color squares and a right or left key press. In the latter condition, the two colors were shown one after the other in the same sequence except for two blocks at the end of the experiment. Overall, cerebellar subjects reacted significantly slower than controls. In both groups, reaction time decreased over blocks, and the learning effect was more pronounced in the stimulus-response than in the stimulus-stimulus-response condition. Post hoc analyses revealed that learning differences between conditions were significant in cerebellar patients but not control subjects. Furthermore, only healthy subjects were irritated, i.e., they significantly increased reaction times in the blocks with reversed sequence in the stimulus-stimulus-response condition. Cerebellar subjects tended to name less correct stimulus-stimulus-response associations after the experiment. Finally, cerebellar volume correlated with parameters of motor performance, but not learning. In conclusion, cerebellar patients showed deficits in stimulus-stimulus-response, but not stimulus-response learning. Future experiments are needed to differentiate between possible deficits in learning the stimulus-stimulus association, use of sequence information, and/or impaired motor performance interfering with learning.

Time windows and reverberating loops: a reverse-engineering approach to cerebellar function

We review a reverse-engineering approach to cerebellar function that pays particular attention to temporal aspects of neuronal interactions. This approach offers new vistas on the role of GABAergic synapses and reverberating projections within the olivo-cerebellar system. More specifically, our simulations show that Golgi cells can control the ring time of granule cells rather than their ring rate and that Purkinje cells can trigger precisely timed rebound spikes in neurons of the deep cerebellar nuclei. This rebound activity can reverberate back to the cerebellar cortex giving rise to a complex oscillatory dynamics that may have interesting functional implications for working memory and timed-response tasks.

MRI in children with mental retardation

BACKGROUND

In mental retardation (MR) an aetiological diagnosis is not always obtained despite a detailed history, physical examination and metabolic or genetic investigations. In some of these patients, MRI is recommended and may identify subtle abnormal brain findings.

OBJECTIVE

We reviewed the cerebral MRI of children with non-specific mental retardation in an attempt to establish a neuroanatomical picture of this disorder.

MATERIALS AND METHODS

Thirty children with non-specific MR were selected to undergo cerebral MRI. The examination included supratentorial axial slices, mid-sagittal images and posterior fossa coronal images. Brain malformations, midline and cerebellar abnormalities were studied.

RESULTS

In 27 of 30 patients, the neuroimaging evaluation revealed a relatively high incidence of cerebral and posterior fossa abnormalities. The most frequent were: dysplasia of the corpus callosum (46%; hypoplasia, short corpus callosum and vertical splenium), partially opened septum pellucidum and/or cavum vergae (33%), ventriculomegaly (33%), cerebral cortical dysplasia (23%), subarachnoid space enlargement (16.6%), vermian hypoplasia (33%), cerebellar and/or vermian disorganised folia (20%), and subarachnoid spaces enlargement in the posterior fossa (20%). Other anomalies were: enlarged Virchow-Robin spaces (10%), white matter anomalies (10%) and cerebellar or vermian atrophy.

CONCLUSIONS

MRI has shown a high incidence of subtle cerebral abnormalities and unexpected minor forms of cerebellar cortical dysplasia. Even if most of these abnormalities are considered as subtle markers of brain dysgenesis, their role in the pathogenesis of mental retardation needs further investigation.

Perceptual learning in amnesia

Evidence from experiments on perceptual learning, accumulated during the last few years, increasingly indicates that the relative 'front end' parts of the visual system are more plastic even in adults than was previously expected. Hence, it might be possible that perceptual learning is similar in several respects to procedural learning and may be achieved even without (declarative) memory traces present. Results on six patients suffering from global amnesia due to damage to hippocampal-diencephalic systems demonstrate, for the first time, that at least some amnesic patients are able to significantly improve performance in a visual hyperacuity task as a result of training, showing improvement as good as the observers in the control group. This result corroborates the notion of a relatively 'front end' location of at least some forms of perceptual learning.

Dscam is associated with axonal and dendritic features of neuronal cells

Dscam, a novel cell-adhesion molecule belonging to the Ig-superfamily mediates homophilic intercellular adhesion and is expressed abundantly in the nervous system during development. To gain better understanding on the role of Dscam in neuronal differentiation, we raised an antibody and characterized its protein product. Anti-Dscam antibody detected an approximately 200-kDa protein band in human and mouse brain lysates. Immunohistochemical studies showed that during embryonic development of mice, mouse Dscam is expressed throughout the neuronal tissues and also in nonneuronal tissues such as lung, liver, and limb buds. In adult brain Dscam expression is predominant in the cerebellum, hippocampus, and olfactory bulb. Immunofluorescence double labeling of hippocampal and cerebellar primary cultures revealed that Dscam is associated with axonal and dendritic processes. In view of its cellular localization and spatiotemporal expression pattern, we suggest that Dscam is involved in cell-cell interactions during axonal-dendritic development, and maintenance of functional neuronal networks.

Cloning and functional characterization of DSCAML1, a novel DSCAM-like cell adhesion molecule that mediates homophilic intercellular adhesion

DSCAM, a conserved gene involved in neuronal differentiation, is a member of the Ig superfamily of cell adhesion molecules. Herein, we report the functional characterization of a human DSCAM (Down syndrome cell adhesion molecule) paralogue, DSCAML1, located on chromosome 11q23. The deduced DSCAML1 protein contains 10 Ig domains, six fibronectin-III domains, and an intracellular domain, all of which are structurally identical to DSCAM. When compared to DSCAM, DSCAML1 protein showed 64% identity to the extracellular domain and 45% identity to the cytoplasmic domain. In the mouse brain, DSCAML1 is predominantly expressed in Purkinje cells of the cerebellum, granule cells of the dentate gyrus, and in neurons of the cerebral cortex and olfactory bulb. Biochemical and immunofluorescence analyses indicated that DSCAML1 is a cell surface molecule that targets axonal features in differentiated PC12 cells. DSCAML1 exhibits homophilic binding activity that does not require divalent cations. Based on its structural and functional properties and similarities to DSCAM, we suggest that DSCAML1 may be involved in formation and maintenance of neural networks. The chromosomal locus for DSCAML1 makes it an ideal candidate for neuronal disorders (such as Gilles de la Tourette and Jacobsen syndromes) that have been mapped on 11q23.

The cerebellum and cognition: cerebellar lesions impair sequence learning but not conditional visuomotor learning in monkeys

Claims that the cerebellum contributes to cognitive processing in humans have arisen from both functional neuroimaging and patient studies. These claims challenge traditional theories of cerebellar function that ascribe motor functions to this structure. We trained monkeys to perform both a visuomotor conditional associative learning task and a visually guided sequence task, and studied the effects of bilateral excitotoxic lesions in the lateral cerebellar nuclei. In the first experiment three operated monkeys showed a small impairment in post-operative retention of a visuomotor associative task (A) but were then not impaired in learning a new task (B). However, the impairment on A could have been due to a problem in making the movements themselves. In a second experiment we therefore gave the three control animals a further pre-operative retest on both A and B and then tested after surgery on retention of both tasks. Though again the animals showed motor problems on task A, they reached criterion, and at this stage could clearly make both movements satisfactorily. The critical test was then retention of task B, and they were not impaired. In the final experiment (serial reaction time task) the monkeys response times on a repeating visuomotor sequence were compared with those for a pseudo-random control sequence. After bilateral nuclei lesions they were slow to execute the pre-operatively learned sequence but were still faster on this than on the control task. However, when they were then given a new repeating sequence to learn, they never performed the sequence as quickly as they had on retention of the first sequence. We conclude that the cerebellum is not essential for the learning or recall of stimulus-response associations but that it is crucially involved in the process by which motor sequences become automatic with extended practice.

Phonological grouping is specifically affected in cerebellar patients: a verbal fluency study

OBJECTIVES

Recent clinical and functional neuroimaging evidence points towards a cerebellar role in verbal production. At present it is not clear how the cerebellum participates in language production. The aim was to investigate the influence of cerebellar lesions on verbal fluency abilities with specific focus on the verbal searching strategies employed by patients with cerebellar damage.

METHODS

Twenty five patients with focal or degenerative cerebellar disease and 14 control subjects were tested in a timed verbal fluency task requiring word production under forced (phonemic or semantic) conditions. To analyse the verbal searching strategy employed, semantic and phonemic cluster analyses were also performed.

RESULTS

Performances of cerebellar patients were comparable with those of controls in the semantic task; conversely their performances were significantly impaired when tested in the letter task. Cluster analysis results showed that the verbal fluency impairment is linked to specific damage of phonemically related retrieval strategies.

CONCLUSION

Cerebellar damage impairs verbal fluency by specifically affecting phonemic rule performances while sparing semantic rule ones. These findings underline the importance of the cerebellar computing properties in strategy development in the linguistic domain.

Autism and autistic behavior in Joubert syndrome

To determine whether individuals with Joubert syndrome exhibit features of autism as defined by the Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV), we examined 11 children with Joubert syndrome using the Autism Diagnostic Interview-Revised and the Autism Diagnostic Observation Schedule-Generic. Three children met DSM-IV criteria for autistic disorder and one for pervasive developmental disorder not otherwise specified. The other seven all demonstrated at least one DSM-IV symptom of autism, but did not meet criteria for a pervasive developmental disorder. Both total number of DSM-IV symptoms and number of social symptoms distinguished the autism and nonautism subgroups. In contrast, the two subgroups displayed similar levels of communication impairments and repetitive or stereotyped behavior. The key to diagnosing autism in Joubert syndrome is to focus on social behaviors, particularly milestones typically achieved very early in life (eg, attending to human voices, showing objects of interest, enjoyment of social interactions). Implications for the role of the cerebellum in nonmotor behavior and for clinical management of Joubert syndrome also are discussed.

Cerebellar hypoperfusion and developmental dysphasia in a male

A male with developmental dysphasia is documented with fine motor dysfunction whose improvement in expressive language was associated with increased cerebellar perfusion, as detected by serial N-isopropyl-p-[iodine-123] iodoamphetamine single photon emission computed tomography (SPECT). His expressive language has been improving since 6 years, 8 months of age, and his verbal intelligence quotient improved from less than 45 at 5 years of age to 80 at 8 years of age. Compared with the SPECT findings at 4 years of age, the ratio of the average pixel values of the cerebellum to the frontal cortices increased at 9 years of age (from 0.81 to 1.03-1.09 in the hemisphere and from 0.66 to 0.98 in the vermis). However, he was not able to understand stories presented orally even at 9 years, 4 months of age. These results suggest that developmental dysphasia, which mostly involves expressive impairment, in this patient could have been the result of delayed maturation of cerebellar function, mainly that of the vermis.

Non-motor associative learning in patients with isolated degenerative cerebellar disease

In recent decades it has become clear that the cerebellum is involved in associative motor learning, but its exact role in motor learning as such is still controversial. Recently, a contribution of the cerebellum to different cognitive abilities has also been considered, but it remains unclear whether the cerebellum contributes to cognitive associative learning. We compared nine patients with an isolated cerebellar degenerative disease in a cognitive associative learning task with 10 controls. Patients and controls were matched for age, sex, handedness, level of education, intelligence and capabilities of visual memory. The subjects were asked to learn the association between six pairs of colours and numerals by trial and error. Additionally, a simple reaction time and a visual scanning test were conducted in order to control for the influence of motor performance deficits in cerebellar patients. In comparison with the controls, it took the patients significantly longer to learn the correct associations between colours and numerals, and they were impaired in recognizing them later on. Two patients showed no associative learning effect at all. Neither the simple reaction time nor the visual scanning time correlated substantially with the results of associative learning. Therefore, motor-associated disabilities are unlikely to be the reason for the learning deficit in cerebellar patients. Our results suggest that the cerebellum might contribute to motor-independent processes that are generally involved in associative learning.