An HRP study of hypothalamo-cerebellar and cerebello-hypothalamic connections in squirrel monkey (Saimiri sciureus)

Doubling down on dual systems: A cerebellum-amygdala route towards action- and outcome-based social and affective behavior

The amygdala and cerebellum are both evolutionary preserved brain structures containing cortical as well as subcortical properties. For decades, the amygdala has been considered the fear-center of the brain, but recent advances have shown that the amygdala acts as a critical hub between cortical and subcortical systems and shapes social and affective behaviors beyond fear. Likewise, the cerebellum is a dedicated control unit that fine-tunes motor behavior to fit contextual requirements. There is however increasing evidence that the cerebellum strongly influences subcortical as well as cortical processes beyond the motor domain. These insights broadened the view on the cerebellum's functions to also include social and affective behavior. Here we explore how the amygdala and cerebellum might interact in shaping social and affective behaviors based on their roles in threat reactivity and reinforcement learning. A novel mechanistic neural framework of cerebellum-amygdala interactions will be presented which provides testable hypotheses for future social and affective neuroscientific research in humans.

A Systematic Review of Direct Outputs from the Cerebellum to the Brainstem and Diencephalon in Mammals

The cerebellum is involved in many motor, autonomic and cognitive functions, and new tasks that have a cerebellar contribution are discovered on a regular basis. Simultaneously, our insight into the functional compartmentalization of the cerebellum has markedly improved. Additionally, studies on cerebellar output pathways have seen a renaissance due to the development of viral tracing techniques. To create an overview of the current state of our understanding of cerebellar efferents, we undertook a systematic review of all studies on monosynaptic projections from the cerebellum to the brainstem and the diencephalon in mammals. This revealed that important projections from the cerebellum, to the motor nuclei, cerebral cortex, and basal ganglia, are predominantly di- or polysynaptic, rather than monosynaptic. Strikingly, most target areas receive cerebellar input from all three cerebellar nuclei, showing a convergence of cerebellar information at the output level. Overall, there appeared to be a large level of agreement between studies on different species as well as on the use of different types of neural tracers, making the emerging picture of the cerebellar output areas a solid one. Finally, we discuss how this cerebellar output network is affected by a range of diseases and syndromes, with also non-cerebellar diseases having impact on cerebellar output areas.

Involvement of the cerebellum in migraine

Migraine is a disabling neurological disease characterized by moderate or severe headaches and accompanied by sensory abnormalities, e.g., photophobia, allodynia, and vertigo. It affects approximately 15% of people worldwide. Despite advancements in current migraine therapeutics, mechanisms underlying migraine remain elusive. Within the central nervous system, studies have hinted that the cerebellum may play an important sensory integrative role in migraine. More specifically, the cerebellum has been proposed to modulate pain processing, and imaging studies have revealed cerebellar alterations in migraine patients. This review aims to summarize the clinical and preclinical studies that link the cerebellum to migraine. We will first discuss cerebellar roles in pain modulation, including cerebellar neuronal connections with pain-related brain regions. Next, we will review cerebellar symptoms and cerebellar imaging data in migraine patients. Lastly, we will highlight the possible roles of the neuropeptide calcitonin gene-related peptide (CGRP) in migraine symptoms, including preclinical cerebellar studies in animal models of migraine.

Modulation of the functional connectome in major depressive disorder by ketamine therapy

BACKGROUND

Subanesthetic ketamine infusion therapy can produce fast-acting antidepressant effects in patients with major depression. How single and repeated ketamine treatment modulates the whole-brain functional connectome to affect clinical outcomes remains uncharacterized.

METHODS

Data-driven whole brain functional connectivity (FC) analysis was used to identify the functional connections modified by ketamine treatment in patients with major depressive disorder (MDD). MDD patients (N = 61, mean age = 38, 19 women) completed baseline resting-state (RS) functional magnetic resonance imaging and depression symptom scales. Of these patients, n = 48 and n = 51, completed the same assessments 24 h after receiving one and four 0.5 mg/kg intravenous ketamine infusions. Healthy controls (HC) (n = 40, 24 women) completed baseline assessments with no intervention. Analysis of RS FC addressed effects of diagnosis, time, and remitter status.

RESULTS

Significant differences (p < 0.05, corrected) in RS FC were observed between HC and MDD at baseline in the somatomotor network and between association and default mode networks. These disruptions in FC in MDD patients trended toward control patterns with ketamine treatment. Furthermore, following serial ketamine infusions, significant decreases in FC were observed between the cerebellum and salience network (SN) (p < 0.05, corrected). Patient remitters showed increased FC between the cerebellum and the striatum prior to treatment that decreased following treatment, whereas non-remitters showed the opposite pattern.

CONCLUSION

Results support that ketamine treatment leads to neurofunctional plasticity between distinct neural networks that are shown as disrupted in MDD patients. Cortico-striatal-cerebellar loops that encompass the SN could be a potential biomarker for ketamine treatment.

Networking of the Human Cerebellum: From Anatomo-Functional Development to Neurosurgical Implications

In the past, the cerebellum was considered to be substantially involved in sensory-motor coordination. However, a growing number of neuroanatomical, neuroimaging, clinical and lesion studies have now provided converging evidence on the implication of the cerebellum in a variety of cognitive, affective, social, and behavioral processes as well. These findings suggest a complex anatomo-functional organization of the cerebellum, involving a dense network of cortical territories and reciprocal connections with many supra-tentorial association areas. The final architecture of cerebellar networks results from a complex, highly protracted, and continuous development from childhood to adulthood, leading to integration between short-distance connections and long-range extra-cerebellar circuits. In this review, we summarize the current evidence on the anatomo-functional organization of the cerebellar connectome. We will focus on the maturation process of afferent and efferent neuronal circuitry, and the involvement of these networks in different aspects of neurocognitive processing. The final section will be devoted to identifying possible implications of this knowledge in neurosurgical practice, especially in the case of posterior fossa tumor resection, and to discuss reliable strategies to improve the quality of approaches while reducing postsurgical morbidity.

Gene expression atlas of energy balance brain regions

Energy balance is controlled by interconnected brain regions in the hypothalamus, brainstem, cortex, and limbic system. Gene expression signatures of these regions can help elucidate the pathophysiology underlying obesity. RNA sequencing was conducted on P56 C57BL/6NTac male mice and E14.5 C57BL/6NTac embryo punch biopsies in 16 obesity-relevant brain regions. The expression of 190 known obesity-associated genes (monogenic, rare, and low-frequency coding variants; GWAS; syndromic) was analyzed in each anatomical region. Genes associated with these genetic categories of obesity had localized expression patterns across brain regions. Known monogenic obesity causal genes were highly enriched in the arcuate nucleus of the hypothalamus and developing hypothalamus. The obesity-associated genes clustered into distinct “modules” of similar expression profile, and these were distinct from expression modules formed by similar analysis with genes known to be associated with other disease phenotypes (type 1 and type 2 diabetes, autism, breast cancer) in the same energy balance–relevant brain regions.

Emotional disorders and the cerebellum: Neurobiological substrates, neuropsychiatry, and therapeutic implications

The notion that the cerebellum is devoted exclusively to motor control has been replaced by a more sophisticated understanding of its role in neurological function, one that includes cognition and emotion. Early clinical reports, as well as physiological and behavioral studies in animal models, raised the possibility of a nonmotor role for the cerebellum. Anatomical studies demonstrate cerebellar connectivity with the distributed neural circuits linked with autonomic, sensorimotor, vestibular, associative, and limbic/paralimbic brain areas. Identification of the cerebellar cognitive affective syndrome in adults and children underscored the clinical relevance of the role of the cerebellum in cognition and emotion. It opened new avenues of investigation into higher-order deficits that accompany the ataxias and other cerebellar diseases, as well as the contribution of cerebellar dysfunction to neuropsychiatric and neurocognitive disorders. Brain imaging studies have demonstrated the complexity of cerebellar functional topography, revealing a double representation of the sensorimotor cerebellum in the anterior lobe and lobule VIII and a triple cognitive representation in the cerebellar posterior lobe, as well as representation in the cerebellum of the intrinsic connectivity networks identified in the cerebral hemispheres. This paradigm shift in thinking about the cerebellum has been advanced by the theories of dysmetria of thought and the universal cerebellar transform, harmonizing the dual anatomic realities of homogeneously repeating cerebellar cortical microcircuitry set against the heterogeneous and topographically arranged cerebellar connections with extracerebellar structures. This new appreciation of cerebellar incorporation into circuits that subserve cognition and emotion mandates a deeper understanding of the cerebellum by practitioners in behavioral neurology and neuropsychiatry because it impacts the understanding and diagnosis of disorders of emotion and intellect and has potential for novel cerebellar-based approaches to therapy.

Hunger and BMI modulate neural responses to sweet stimuli: fMRI meta-analysis

OBJECTIVE

Consuming sweet foods, even when sated, can lead to unwanted weight gain. Contextual factors, such as longer time fasting, subjective hunger, and body mass index (BMI), may increase the likelihood of overeating. Nevertheless, the neural mechanisms underlying these moderating influences on energy intake are poorly understood.

METHODS

We conducted both categorical meta-analysis and meta-regression of factors modulating neural responses to sweet stimuli, using data from 30 functional magnetic resonance imaging (fMRI) articles incorporating 39 experiments (N = 995) carried out between 2006 and 2019.

RESULTS

Responses to sweet stimuli were associated with increased activity in regions associated with taste, sensory integration, and reward processing. These taste-evoked responses were modulated by context. Longer fasts were associated with higher posterior cerebellar, thalamic, and striatal activity. Greater self-reported hunger was associated with higher medial orbitofrontal cortex (OFC), dorsal striatum, and amygdala activity and lower posterior cerebellar activity. Higher BMI was associated with higher posterior cerebellar and insular activity.

CONCLUSIONS

Variations in fasting time, self-reported hunger, and BMI are contexts associated with differential sweet stimulus responses in regions associated with reward processing and homeostatic regulation. These results are broadly consistent with a hierarchical model of taste processing. Hunger, but not fasting or BMI, was associated with sweet stimulus-related OFC activity. Our findings extend existing models of taste processing to include posterior cerebellar regions that are associated with moderating effects of both state (fast length and self-reported hunger) and trait (BMI) variables.

Altered Hypothalamic Region Covariance in Migraine and Cluster Headache: A Structural MRI Study

OBJECTIVES

The hypothalamus plays a key role in both migraine and cluster headache (CH). As brain region-to-region structural correlations are believed to reflect structural and functional brain connectivity patterns, we assessed the structural covariance patterns between the volume of the hypothalamic region and vertex-by-vertex measurements of cortical thickness in patients with migraine and in those with CH relative to healthy controls (HC).

METHODS

T1-weighted images were acquired on a 3T MRI scanner for a total of 59 subjects including 18 patients with CH (age: mean = 43.8, SD = 12.4), 19 with migraine (age: mean = 40.1, SD = 12.2), and 22 HCs (age: mean = 39.1, SD = 8.2). Imaging was collected between attacks (migraineurs) and during out-of-bout phases (CH). Data were post-processed using FreeSurfer version 6.0 and within-group correlations between hypothalamic region volume with cortical thickness were explored using a whole-brain vertex-wise linear model approach. Between-group differences in correlation slopes between hypothalamic region volume and vertex-by-vertex measurements of cortical thickness were interrogated using post-hoc comparisons.

RESULTS

There were no significant between-group differences (migraine vs CH; migraine vs HC; or CH vs HC) for age, sex, total brain volume or volume of the left or right hypothalamic region. For each group, there were significant positive correlations (P < .01) between right and left hypothalamic region volumes with cortical thickness measurements. HC had significant positive correlations between hypothalamic region volume and cortical thickness over large portions of the superior and rostral medial frontal, orbitofrontal cortex and rostral anterior cingulate, and smaller clusters in the superior and middle temporal, posterior cingulate, fusiform, and precentral cortex. Post-hoc analysis showed significant differences in covariance patterns in those with migraine and CH relative to HC, with both migraine patients and CH having weaker structural covariance of hypothalamic region volume with frontal and temporal cortical thickness.

CONCLUSION

Recent evidence suggests hypothalamic region connectivity to frontal and temporal areas to be relevant for regulating pain perception. Thus, the diminished structural covariance in migraineurs and CH might suggest abnormal functioning of the pain control circuitry and contribute to mechanisms underlying central sensitization and chronification of pain.

Fiber dissection and 3-tesla diffusion tensor tractography of the superior cerebellar peduncle in the human brain: emphasize on the cerebello-hypthalamic fibers

Experimental studies in various species using tract-tracing techniques showed clear evidence of the presence of cerebello-hypothalamic projections. However, these connections were not clearly described in humans. In the present study we aimed to describe the direct cerebello-hypothalamic connections within the superior cerebellar peduncle (SCP) using fiber dissection techniques on cadaveric brains and diffusion tensor tractography (DTI) in healthy adults. Fiber dissection was performed in a stepwise manner from lateral to medial on 6 cerebral hemispheres. The gray matter was decorticate and fiber tracts were revealed. The SCP was exposed and the fibers were traced distally using wooden spatulas. The MRI examinations were performed in seven cases using 3-tesla 3T unit. The direct cerebello-hyothalamic pathways were exposed using high-spatial-resolution DTI. The present study using both fiber dissection and DTI in adult human showed direct cerebello-hypothalamic fibers within the SCP. The SCP fibers course anterolateral to the cerebral aqueduct reaching the level of the red nucleus of the midbrain. The majority of the fibers crosses over and reached the contralateral diencephalic structures and some of these fibers terminated at the contralateral anterior hypothalamic area. Some of the uncrossed SCP fibers reached the ipsilateral diencephalic structures and terminated at the ipsilateral posterior hypothalamic area. We further reported the close relationship of the SCP with the MCP, lateral lemniscus, red nucleus and substantia nigra. In the DTI evaluations of the SCP we exposed unilateral left cerebello-hypothalamic fibers in five cases and bilateral cerebello-hypothalamic fibers in two cases. The present study demonstrates the direct cerebello-hypothalamic connections within the SCP for the first time using fiber dissection and DTI technique in the human brain. The detailed knowledge of the cerebello-hypothalamic fibers can outline the unexplained deficit that may occur during regional surgery.

Is the Cerebellum Involved in the Nervous Control of the Immune System Function?

BACKGROUND

According to the views of psychoneuroendocrinoimmunology, many interactions exist between nervous, endocrine and immune system the purpose of which is to achieve adaptive measures restoring an internal equilibrium (homeostasis) following stress conditions. The center where these interactions converge is the hypothalamus. This is a center of the autonomic nervous system that controls the visceral systems, including the immune system, through both the nervous and neuroendocrine mechanisms. The nervous mechanisms are based on nervous circuits that bidirectionally connect hypothalamic neurons and neurons of the sympathetic and parasympathetic system; the neuroendocrine mechanisms are based on the release by neurosecretory hypothalamic neurons of hormones that target the endocrine cells and on the feedback effects of the hormones secreted by these endocrine cells on the same hypothalamic neurons. Moreover, the hypothalamus is an important subcortical center of the limbic system that controls through nervous and neuroendocrine mechanisms the areas of the cerebral cortex where the psychic functions controlling mood, emotions, anxiety and instinctive behaviors take place. Accordingly, various studies conducted in the last decades have indicated that hypothalamic diseases may be associated with immune and/or psychic disorders.

OBJECTIVE

Various researches have reported that the hypothalamus is controlled by the cerebellum through a feedback nervous circuit, namely the hypothalamocerebellar circuit, which bi-directionally connects regions of the hypothalamus, including the immunoregulatory ones, and related regions of the cerebellum. An objective of the present review was to analyze the anatomical bases of the nervous and neuroendocrine mechanisms for the control of the immune system and, in particular, of the interaction between hypothalamus and cerebellum to achieve the immunoregulatory function.

CONCLUSION

Since the hypothalamus represents the link through which the immune functions may influence the psychic functions and vice versa, the cerebellum, controlling several regions of the hypothalamus, could be considered as a primary player in the regulation of the multiple functional interactions postulated by psychoneuroendocrinoimmunology.

Altered microglia and neurovasculature in the Alzheimer's disease cerebellum

Traditionally regarded to coordinate movement, the cerebellum also exerts non-motor functions including the regulation of cognitive and behavioral processing, suggesting a potential role in neurodegenerative conditions affecting cognition, such as Alzheimer's disease (AD). This study aims to investigate neuropathology and AD-related molecular changes within the neocerebellum using post-mortem human brain tissue microarrays (TMAs). Immunohistochemistry was conducted on neocerebellar paraffin-embedded TMAs from 24 AD and 24 matched control cases, and free-floating neocerebellar sections from 6 AD and 6 controls. Immunoreactivity was compared between control and AD groups for neuropathological hallmarks (amyloid-β, tau, ubiquitin), Purkinje cells (calbindin), microglia (IBA1, HLA-DR), astrocytes (GFAP) basement-membrane associated molecules (fibronectin, collagen IV), endothelial cells (CD31/PECAM-1) and mural cells (PDGFRβ, αSMA). Amyloid-β expression (total immunolabel intensity) and load (area of immunolabel) was increased by >4-fold within the AD cerebellum. Purkinje cell counts, ubiquitin and tau immunoreactivity were unchanged in AD. IBA1 expression and load was increased by 91% and 69%, respectively, in AD, with no change in IBA1-positive cell number. IBA1-positive cell process length and branching was reduced by 22% and 41%, respectively, in AD. HLA-DR and GFAP immunoreactivity was unchanged in AD. HLA-DR-positive cell process length and branching was reduced by 33% and 49%, respectively, in AD. Fibronectin expression was increased by 27% in AD. Collagen IV, PDGFRβ and αSMA immunoreactivity was unchanged in AD. The number of CD31-positive vessels was increased by 98% in AD, suggesting the increase in CD31 expression and load in AD is due to greater vessel number. The PDGFRβ/CD31 load ratio was reduced by 59% in AD. These findings provide evidence of molecular changes affecting microglia and the neurovasculature within the AD neocerebellum. These changes, occurring without overt neuropathology, support the hypothesis of microglial and neurovascular dysfunction as drivers of AD, which has implications on the neocerebellar contribution to AD symptomatology and pathophysiology.

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.

Constrained Spherical Deconvolution Tractography Reveals Cerebello-Mammillary Connections in Humans

According to the classical view, the cerebellum has long been confined to motor control physiology; however, it has now become evident that it exerts several non-somatic features other than the coordination of movement and is engaged also in the regulation of cognition and emotion. In a previous diffusion-weighted imaging-constrained spherical deconvolution (CSD) tractography study, we demonstrated the existence of a direct cerebellum-hippocampal pathway, thus reinforcing the hypothesis of the cerebellar role in non-motor domains. However, our understanding of limbic-cerebellar interconnectivity in humans is rather sparse, primarily due to the intrinsic limitation in the acquisition of in vivo tracing. Here, we provided tractographic evidences of connectivity patterns between the cerebellum and mammillary bodies by using whole-brain CSD tractography in 13 healthy subjects. We found both ipsilateral and contralateral connections between the mammillary bodies, cerebellar cortex, and dentate nucleus, in line with previous studies performed in rodents and primates. These pathways could improve our understanding of cerebellar role in several autonomic functions, visuospatial orientation, and memory and may shed new light on neurodegenerative diseases in which clinically relevant impairments in navigational skills or memory may become manifest at early stages.

Network-selective vulnerability of the human cerebellum to Alzheimer's disease and frontotemporal dementia

SEE SCHMAHMANN DOI101093/BRAIN/AWW064 FOR A SCIENTIFIC COMMENTARY ON THIS ARTICLE: Neurodegenerative diseases are associated with distinct and distributed patterns of atrophy in the cerebral cortex. Emerging evidence suggests that these atrophy patterns resemble intrinsic connectivity networks in the healthy brain, supporting the network-based degeneration framework where neuropathology spreads across connectivity networks. An intriguing yet untested possibility is that the cerebellar circuits, which share extensive connections with the cerebral cortex, could be selectively targeted by major neurodegenerative diseases. Here we examined the structural atrophy in the cerebellum across common types of neurodegenerative diseases, and characterized the functional connectivity patterns of these cerebellar atrophy regions. Our results showed that Alzheimer's disease and frontotemporal dementia are associated with distinct and circumscribed atrophy in the cerebellum. These cerebellar atrophied regions share robust and selective intrinsic connectivity with the atrophied regions in the cerebral cortex. These findings for the first time demonstrated the selective vulnerability of the cerebellum to common neurodegenerative disease, extending the network-based degeneration framework to the cerebellum. Our work also has direct implications on the cerebellar contribution to the cognitive and affective processes that are compromised in neurodegeneration as well as the practice of using the cerebellum as reference region for ligand neuroimaging studies.

Consensus paper: the role of the cerebellum in perceptual processes

Various lines of evidence accumulated over the past 30 years indicate that the cerebellum, long recognized as essential for motor control, also has considerable influence on perceptual processes. In this paper, we bring together experts from psychology and neuroscience, with the aim of providing a succinct but comprehensive overview of key findings related to the involvement of the cerebellum in sensory perception. The contributions cover such topics as anatomical and functional connectivity, evolutionary and comparative perspectives, visual and auditory processing, biological motion perception, nociception, self-motion, timing, predictive processing, and perceptual sequencing. While no single explanation has yet emerged concerning the role of the cerebellum in perceptual processes, this consensus paper summarizes the impressive empirical evidence on this problem and highlights diversities as well as commonalities between existing hypotheses. In addition to work with healthy individuals and patients with cerebellar disorders, it is also apparent that several neurological conditions in which perceptual disturbances occur, including autism and schizophrenia, are associated with cerebellar pathology. A better understanding of the involvement of the cerebellum in perceptual processes will thus likely be important for identifying and treating perceptual deficits that may at present go unnoticed and untreated. This paper provides a useful framework for further debate and empirical investigations into the influence of the cerebellum on sensory perception.

Global and regional brain mean diffusivity changes in patients with heart failure

Heart failure (HF) patients show gray and white matter changes in multiple brain sites, including autonomic and motor coordination areas. It is unclear whether the changes represent acute or chronic tissue pathology, a distinction necessary for understanding pathological processes that can be resolved with diffusion tensor imaging (DTI)-based mean diffusivity (MD) procedures. We collected four DTI series from 16 HF (age 55.1 ± 7.8 years, 12 male) and 26 control (49.7 ± 10.8 years, 17 male) subjects with a 3.0-Tesla magnetic resonance imaging scanner. MD maps were realigned, averaged, normalized, and smoothed. Global and regional MD values from autonomic and motor coordination sites were calculated by using normalized MD maps and brain masks; group MD values and whole-brain smoothed MD maps were compared by analysis of covariance (covariates; age and gender). Global brain MD (HF vs. controls, units × 10(-6) mm(2) /sec, 1103.8 ± 76.6 vs. 1035.9 ± 69.4, P = 0.038) and regional autonomic and motor control site values (left insula, 1,085.4 ± 95.7 vs. 975.7 ± 65.4, P = 0.001; right insula, 1,050.2 ± 100.6 vs. 965.7 ± 58.4, P = 0.004; left hypothalamus, 1,419.6 ± 165.2 vs. 1,234.9 ± 136.3, P = 0.002; right hypothalamus, 1,446.5 ± 178.8 vs. 1,273.3 ± 136.9, P = 0.004; left cerebellar cortex, 889.1 ± 81.9 vs. 796.6 ± 46.8, P < 0.001; right cerebellar cortex, 797.8 ± 50.8 vs. 750.3 ± 27.5, P = 0.001; cerebellar deep nuclei, 1,236.1 ± 193.8 vs. 1,071.7 ± 107.1, P = 0.002) were significantly higher in HF vs. control subjects, indicating chronic tissue changes. Whole-brain comparisons showed increased MD values in HF subjects, including limbic, basal-ganglia, thalamic, solitary tract nucleus, frontal, and cerebellar regions. Brain injury occurs in autonomic and motor control areas, which may contribute to deficient function in HF patients. The chronic tissue changes likely result from processes that develop over a prolonged period.

Altered hypothalamic functional connectivity with autonomic circuits and the locus coeruleus in migraine

The hypothalamus has been implicated in migraine based on the manifestation of autonomic symptoms with the disease, as well as neuroimaging evidence of hypothalamic activation during attacks. Our objective was to determine functional connectivity (FC) changes between the hypothalamus and the rest of the brain in migraine patients vs. control subjects. This study uses fMRI (functional magnetic resonance imaging) to acquire resting state scans in 12 interictal migraine patients and 12 healthy matched controls. Hypothalamic connectivity seeds were anatomically defined based on high-resolution structural scans, and FC was assessed in the resting state scans. Migraine patients had increased hypothalamic FC with a number of brain regions involved in regulation of autonomic functions, including the locus coeruleus, caudate, parahippocampal gyrus, cerebellum, and the temporal pole. Stronger functional connections between the hypothalamus and brain areas that regulate sympathetic and parasympathetic functions may explain some of the hypothalamic-mediated autonomic symptoms that accompany or precede migraine attacks.

A hypothetical universal model of cerebellar function: reconsideration of the current dogma

The cerebellum is commonly studied in the context of the classical eyeblink conditioning model, which attributes an adaptive motor function to cerebellar learning processes. This model of cerebellar function has quite a few shortcomings and may in fact be somewhat deficient in explaining the myriad functions attributed to the cerebellum, functions ranging from motor sequencing to emotion and cognition. The involvement of the cerebellum in these motor and non-motor functions has been demonstrated in both animals and humans in electrophysiological, behavioral, tracing, functional neuroimaging, and PET studies, as well as in clinical human case studies. A closer look at the cerebellum's evolutionary origin provides a clue to its underlying purpose as a tool which evolved to aid predation rather than as a tool for protection. Based upon this evidence, an alternative model of cerebellar function is proposed, one which might more comprehensively account both for the cerebellum's involvement in a myriad of motor, affective, and cognitive functions and for the relative simplicity and ubiquitous repetitiveness of its circuitry. This alternative model suggests that the cerebellum has the ability to detect coincidences of events, be they sensory, motor, affective, or cognitive in nature, and, after having learned to associate these, it can then trigger (or "mirror") these events after having temporally adjusted their onset based on positive/negative reinforcement. The model also provides for the cerebellum's direction of the proper and uninterrupted sequence of events resulting from this learning through the inhibition of efferent structures (as demonstrated in our lab).

Cerebellar fastigial nuclear GABAergic projections to the hypothalamus modulate immune function

Our previous work has shown that the cerebellar fastigial nucleus (FN) is involved in modulation of lymphocyte function. Herein, we investigated effect of FN γ-aminobutyric acid (GABA)-ergic projections to the hypothalamus on lymphocytes to understand pathways and mechanisms underlying cerebellar immunomodulation. By injection of Texas red dextran amine (TRDA), an anterograde tracer, into FN, we found that the TRDA-labeled fibers from the FN traveled through the superior cerebellar peduncle (SCP), crossed in decussation of SCP (XSCP), entered the hypothalamus, and primarily terminated in the lateral hypothalamic area (LHA). Further, by injecting Fluoro-Ruby (FR), a retrograde tracer, in LHA, we observed that the FR-stained fibers retrogradely passed through XSCP and reached FN. Among these FR-positive neurons in the FN, there were GABA-immunoreactive cells. We then microinjected vigabatrin, which is an inhibitor of GABA-transaminase (GABA-T) that degrades GABA, bilaterally into FN. The vigabatrin treatment increased both number of GABA-immunoreactive neurons in FN-LHA projections and GABA content in the hypothalamus. Simultaneously, vigabatrin significantly reduced concanavalin A (Con A)-induced lymphocyte proliferation, anti-sheep red blood cell (SRBC) IgM antibody level, and natural killer (NK) cell number and cytotoxicity. In support of these findings, we inhibited GABA synthesis by using 3-mercaptopropionic acid (3-MP), which antagonizes glutamic acid decarboxylase (GAD). We found that the inhibition of GABA synthesis caused changes that were opposite to those when GABA was increased with vigabatrin. These findings show that the cerebellar FN has a direct GABAergic projection to the hypothalamus and that this projection actively participates in modulation of lymphocytes.

The cerebellum link to neuroticism: a volumetric MRI association study in healthy volunteers

Prior research suggests an association between reduced cerebellar volumes and symptoms of depression and anxiety in patients with mood disorders. However, whether a smaller volume in itself reflects a neuroanatomical correlate for increased susceptibility to develop mood disorders remains unclear. The aim of the present study was to examine the relationship between cerebellar volume and neurotic personality traits in a non-clinical subject sample. 3T Structural magnetic resonance imaging scans were acquired, and trait depression and anxiety scales of the revised NEO personality inventory were assessed in thirty-eight healthy right-handed volunteers. Results showed that cerebellar volume corrected for total brain volume was inversely associated with depressive and anxiety-related personality traits. Cerebellar gray and white matter contributed equally to the observed associations. Our findings extend earlier clinical observations by showing that cerebellar volume covaries with neurotic personality traits in healthy volunteers. The results may point towards a possible role of the cerebellum in the vulnerability to experience negative affect. In conclusion, cerebellar volumes may constitute a clinico-neuroanatomical correlate for the development of depression- and anxiety-related symptoms.

Modulatory effects of theta burst stimulation on cerebellar nonsomatic functions

Clinical and functional imaging studies suggest that the cerebellar vermis is involved in the regulation of a range of nonsomatic functions including cardiovascular control, thirst, feeding behavior, and primal emotions. Cerebello-hypothalamic circuits have been postulated to be a potential neuroanatomical substrate underlying this modulation. We tested this putative relationship between the cerebellar vermis and nonsomatic functions by stimulating the cerebellum noninvasively via neuronavigated transcranial magnetic stimulation. In this randomized, counter-balanced, within-subject study, intermittent theta burst stimulation (TBS) was applied on three different days to the vermis and the right and left cerebellar hemispheres of 12 right-handed normal subjects with the aim of modulating activity in the targeted cerebellar structure. TBS-associated changes were investigated via cardiovascular monitoring, a series of emotionally arousing picture stimuli, subjective analog scales for primal emotions, and the Profile of Mood States test. All 36 sessions of cerebellar stimulation were tolerated well without serious adverse events. Cardiovascular monitoring pointed to a mild but significant decrease in heart rate subsequent to vermal stimulation; no changes were detected in systolic or diastolic blood pressure measurements. Subjective ratings detected a significant increase in Thirst and a trend toward increased Appetite following vermal stimulation. These observations are consistent with existing neurophysiological and neuroimaging data indicating a role for the cerebellum in the regulation of visceral responses. In conjunction with the modulatory function of the cerebellum, our results suggest a role for the vermis in somatovisceral integration likely through cerebello-hypothalamic pathways. Further research is warranted to elucidate the potential mechanisms underlying the cerebellar modulation of nonsomatic functions.

Brain axonal and myelin evaluation in heart failure

Although gray matter injury appears in heart failure (HF) patients, the presence, extent, and nature of axonal injury impacting on cardiovascular regulation and other functions is unclear. We performed diffusion tensor imaging (3.0-Tesla magnetic resonance imaging scanner) in 16 HF and 26 control subjects, and assessed whole-brain water diffusion parallel (axial diffusivity; axonal status) and perpendicular (radial diffusivity; myelin changes) to fibers. Regions with increased axial diffusivity only, indicating impaired axonal integrity, emerged in cardiovascular, hedonic, and pain regulatory areas, including basal forebrain, hypothalamic and limbic projections through the medial forebrain bundle and raphe magnus projections to the medulla and cerebellum. Other fiber paths between sites implicated in cognition, including limbic, basal-ganglia, thalamic, internal capsule, and corpus callosum were also altered. Sites with increased radial diffusivity only, indicating myelin breakdown, appeared in the corpus callosum, cingulate, and temporal, parietal, occipital, and frontal regions. Both higher axial and radial diffusivity, indicating loss of tissue integrity, appeared in parietal and occipital lobes, limbic regions, insula, internal capsule, cerebellum, and dorsolateral medulla. Axons and myelin are altered in HF, likely resulting from ischemic/hypoxic processes acting chronically and sub-acutely, respectively. The alterations would contribute to the multiple autonomic and neuropsychological symptoms found in HF.

The cerebellum and pain: passive integrator or active participator?

The cerebellum is classically considered to be a brain region involved in motor processing, but it has also been implicated in non-motor, and even cognitive, functions. Though previous research suggests that the cerebellum responds to noxious stimuli, its specific role during pain is unclear. Pain is a multidimensional experience that encompasses sensory discriminative, affective motivational, and cognitive evaluative components. Cerebellar involvement during the processing of pain could thus potentially reflect a number of different functional processes. This review will summarize the animal and human research to date that indicates that (1) primary afferents conduct nociceptive (noxious) input to the cerebellum, (2) electrical and pharmacological stimulation of the cerebellum can modulate nociceptive processing, and (3) cerebellar activity occurs during the presence of acute and chronic pain. Possible functional roles for the cerebellum relating to pain will be considered, including perspectives relating to emotion, cognition, and motor control in response to pain.

The role of the cerebellum in cognition and emotion: personal reflections since 1982 on the dysmetria of thought hypothesis, and its historical evolution from theory to therapy

The cognitive neuroscience of the cerebellum is now an established multidisciplinary field of investigation. This essay traces the historical evolution of this line of inquiry from an emerging field to its current status, with personal reflections over almost three decades on this journey of discovery. It pays tribute to early investigators who recognized the wider role of the cerebellum beyond motor control, traces the origins of new terms and concepts including the dysmetria of thought theory, the universal cerebellar transform, and the cerebellar cognitive affective syndrome, and places these developments within the broader context of the scientific efforts of a growing community of cerebellar cognitive neuroscientists. This account considers the converging evidence from theoretical, anatomical, physiological, clinical, and functional neuroimaging approaches that have resulted in the transition from recognizing the cerebellar incorporation into the distributed neural circuits subserving cognition and emotion, to a hopeful new era of treatment of neurocognitive and neuropsychiatric manifestations of cerebellar diseases, and to cerebellar-based interventions for psychiatric disorders.

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.

Distinct cerebellar contributions to intrinsic connectivity networks

Convergent data from various scientific approaches strongly implicate cerebellar systems in nonmotor functions. The functional anatomy of these systems has been pieced together from disparate sources, such as animal studies, lesion studies in humans, and structural and functional imaging studies in humans. To better define this distinct functional anatomy, in the current study we delineate the role of the cerebellum in several nonmotor systems simultaneously and in the same subjects using resting state functional connectivity MRI. Independent component analysis was applied to resting state data from two independent datasets to identify common cerebellar contributions to several previously identified intrinsic connectivity networks (ICNs) involved in executive control, episodic memory/self-reflection, salience detection, and sensorimotor function. We found distinct cerebellar contributions to each of these ICNs. The neocerebellum participates in (1) the right and left executive control networks (especially crus I and II), (2) the salience network (lobule VI), and (3) the default-mode network (lobule IX). Little to no overlap was detected between these cerebellar regions and the sensorimotor cerebellum (lobules V-VI). Clusters were also located in pontine and dentate nuclei, prominent points of convergence for cerebellar input and output, respectively. The results suggest that the most phylogenetically recent part of the cerebellum, particularly crus I and II, make contributions to parallel cortico-cerebellar loops involved in executive control, salience detection, and episodic memory/self-reflection. The largest portions of the neocerebellum take part in the executive control network implicated in higher cognitive functions such as working memory.

Functional grouping and cortical-subcortical interactions in emotion: a meta-analysis of neuroimaging studies

We performed an updated quantitative meta-analysis of 162 neuroimaging studies of emotion using a novel multi-level kernel-based approach, focusing on locating brain regions consistently activated in emotional tasks and their functional organization into distributed functional groups, independent of semantically defined emotion category labels (e.g., "anger," "fear"). Such brain-based analyses are critical if our ways of labeling emotions are to be evaluated and revised based on consistency with brain data. Consistent activations were limited to specific cortical sub-regions, including multiple functional areas within medial, orbital, and inferior lateral frontal cortices. Consistent with a wealth of animal literature, multiple subcortical activations were identified, including amygdala, ventral striatum, thalamus, hypothalamus, and periaqueductal gray. We used multivariate parcellation and clustering techniques to identify groups of co-activated brain regions across studies. These analyses identified six distributed functional groups, including medial and lateral frontal groups, two posterior cortical groups, and paralimbic and core limbic/brainstem groups. These functional groups provide information on potential organization of brain regions into large-scale networks. Specific follow-up analyses focused on amygdala, periaqueductal gray (PAG), and hypothalamic (Hy) activations, and identified frontal cortical areas co-activated with these core limbic structures. While multiple areas of frontal cortex co-activated with amygdala sub-regions, a specific region of dorsomedial prefrontal cortex (dmPFC, Brodmann's Area 9/32) was the only area co-activated with both PAG and Hy. Subsequent mediation analyses were consistent with a pathway from dmPFC through PAG to Hy. These results suggest that medial frontal areas are more closely associated with core limbic activation than their lateral counterparts, and that dmPFC may play a particularly important role in the cognitive generation of emotional states.

Cerebellar lesions: is there a lateralisation effect on memory deficits?

BACKGROUND

Until recently, neurosurgeons eagerly removed cerebellar lesions without consideration of future cognitive impairment that might be caused by the resection. In children, transient cerebellar mutism after resection has lead to a diminished use of midline approaches and vermis transection, as well as reduced retraction of the cerebellar hemispheres. The role of the cerebellum in higher cognitive functions beyond coordination and motor control has recently attracted significant interest in the scientific community, and might change the neurosurgical approach to these lesions. The aim of this study was to investigate the specific effects of cerebellar lesions on memory, and to assess a possible lateralisation effect.

METHODS

We studied 16 patients diagnosed with a cerebellar lesion, from January 1997 to April 2005, in the "Centre Hospitalier Universitaire Vaudois (CHUV)", Lausanne, Switzerland. Different neuropsychological tests assessing short term and anterograde memory, verbal and visuo-spatial modalities were performed pre-operatively.

RESULTS

Severe memory deficits in at least one modality were identified in a majority (81%) of patients with cerebellar lesions. Only 1 patient (6%) had no memory deficit. In our series lateralisation of the lesion did not lead to a significant difference in verbal or visuo-spatial memory deficits.

FINDINGS

These findings are consistent with findings in the literature concerning memory deficits in isolated cerebellar lesions. These can be explained by anatomical pathways. However, the cross-lateralisation theory cannot be demonstrated in our series. The high percentage of patients with a cerebellar lesion who demonstrate memory deficits should lead us to assess memory in all patients with cerebellar lesions.

The cerebellum in feeding control: possible function and mechanism

Accumulating anatomical, functional, and behavioral studies reveal that the cerebellum is involved in the regulation of various visceral functions including feeding control. Cerebellar lesions may induce alterations in feeding behavior and decreases in body weight. Although the exact mechanisms underlying the cerebellar regulation of food intake is still unclear, a series of studies have demonstrated that there are neural pathways directly and/or indirectly connecting the cerebellum with several important centers for feeding control, such as the hypothalamus. Electrophysiological data suggest that via the direct cerebellohypothalamic projections, the cerebellar outputs may reach, converge, and be integrated with some critical feeding signals including gastric vagal afferents, CCK, leptin, and glycemia on single hypothalamic neurons. Furthermore, recent functional imaging studies provide substantial evidences that hunger, satiation, and thirst are accompanied with a cerebellar activation. Here we describe that the cerebellum may be much more than a movement coordinator and actively participate in feeding control, i.e., it may act as an essential node linking somatic and visceral systems and help to generate an integrated and coordinated somatic-visceral response in feeding behavior.

The neuropsychiatry of the cerebellum - insights from the clinic

A central aspect of the cerebellar cognitive affective syndrome is the dysregulation of affect that occurs when lesions involve the 'limbic cerebellum' (vermis and fastigial nucleus). In this case series we describe neuropsychiatric disturbances in adults and children with congenital lesions including cerebellar agenesis, dysplasia, and hypoplasia, and acquired conditions including cerebellar stroke, tumor, cerebellitis, trauma, and neurodegenerative disorders. The behaviors that we witnessed and that were described by patients and families included distractibility and hyperactivity, impulsiveness, disinhibition, anxiety, ritualistic and stereotypical behaviors, illogical thought and lack of empathy, as well as aggression and irritability. Ruminative and obsessive behaviors, dysphoria and depression, tactile defensiveness and sensory overload, apathy, childlike behavior, and inability to appreciate social boundaries and assign ulterior motives were also evident. We grouped these disparate neurobehavioral profiles into five major domains, characterized broadly as disorders of attentional control, emotional control, and social skill set as well as autism spectrum disorders, and psychosis spectrum disorders. Drawing on our dysmetria of thought hypothesis, we conceptualized the symptom complexes within each putative domain as reflecting either exaggeration (overshoot, hypermetria) or diminution (hypotonia, or hypometria) of responses to the internal or external environment. Some patients fluctuated between these two states. We consider the implications of these neurobehavioral observations for the care of patients with ataxia, discuss the broader role of the cerebellum in the pathogenesis of these neuropsychiatric symptoms, and revisit the possibility of using cerebellar stimulation to treat psychiatric disorders by enhancing cerebellar modulation of cognition and emotion.

The cerebellar-hypothalamic circuits: potential pathways underlying cerebellar involvement in somatic-visceral integration

The cerebellum has been considered only as a classical subcortical center for motor control. However, accumulating experimental and clinical evidences have revealed that the cerebellum also plays an important role in cognition, for instance, in learning and memory, as well as in emotional behavior and in nonsomatic activities, such as visceral and immunological responses. Although it is not yet clear through which pathways such cerebellar nonsomatic functions are mediated, the direct bidirectional connections between the cerebellum and the hypothalamus, a high autonomic center, have recently been demonstrated in a series of neuroanatomical investigations on a variety of mammals and indicated to be potential pathways underlying the cerebellar autonomic modulation. The direct hypothalamocerebellar projections originate from the widespread hypothalamic nuclei/areas and terminate in both the cerebellar cortex as multilayered fibers and the cerebellar nuclei. Immunohistochemistry studies have offered fairly convincing evidence that some of these projecting fibers are histaminergic. It has been suggested that through their excitatory effects on cerebellar cortical and nuclear cells mediated by metabotropic histamine H(2) and/or H(1) receptors, the hypothalamocerebellar histaminergic fibers participate in cerebellar modulation of somatic motor as well as non-motor responses. On the other hand, the direct cerebellohypothalamic projections arise from all cerebellar nuclei (fastigial, anterior and posterior interpositus, and dentate nuclei) and reach almost all hypothalamic nuclei/areas. Neurophysiological and neuroimaging studies have demonstrated that these connections may be involved in feeding, cardiovascular, osmotic, respiratory, micturition, immune, emotion, and other nonsomatic regulation. These observations provide support for the hypothesis that the cerebellum is an essential modulator and coordinator for integrating motor, visceral and behavioral responses, and that such somatic-visceral integration through the cerebellar circuitry may be fulfilled by means of the cerebellar-hypothalamic circuits.

The integrated response of the human cerebro-cerebellar and limbic systems to acupuncture stimulation at ST 36 as evidenced by fMRI

Clinical and experimental data indicate that most acupuncture clinical results are mediated by the central nervous system, but the specific effects of acupuncture on the human brain remain unclear. Even less is known about its effects on the cerebellum. This fMRI study demonstrated that manual acupuncture at ST 36 (Stomach 36, Zusanli), a main acupoint on the leg, modulated neural activity at multiple levels of the cerebro-cerebellar and limbic systems. The pattern of hemodynamic response depended on the psychophysical response to needle manipulation. Acupuncture stimulation typically elicited a composite of sensations termed deqi that is related to clinical efficacy according to traditional Chinese medicine. The limbic and paralimbic structures of cortical and subcortical regions in the telencephalon, diencephalon, brainstem and cerebellum demonstrated a concerted attenuation of signal intensity when the subjects experienced deqi. When deqi was mixed with sharp pain, the hemodynamic response was mixed, showing a predominance of signal increases instead. Tactile stimulation as control also elicited a predominance of signal increase in a subset of these regions. The study provides preliminary evidence for an integrated response of the human cerebro-cerebellar and limbic systems to acupuncture stimulation at ST 36 that correlates with the psychophysical response.

The effects of unilateral removal of the cerebellar hemispheres on motor functions and weight gain in rats

Left or right unilateral removal of a cerebellar hemisphere resulted in a high mortality rate caused by anorexia, not previously seen in cerebellectomized animals. The reduced post-surgical gain in body weight may be explained by oropharyngeal dyspraxia or a loss in appetite. However, the growth rate of the surviving animals was similar to that of controls. After unilateral damage of the cerebellum, deficits were observed in motor coordination tasks, such as the rotorod, the hole-board, and the stationary beam, and the left hemisphere group fell from a suspended wire sooner than controls. The motor deficits were more pronounced after left as opposed to right cerebellar damage on the rotorod, implying a certain degree of functional lateralization for this test.

Cerebellar blood volume in bipolar patients correlates with medication

BACKGROUND

Cerebellar abnormalities, including decreased tissue volume, have been implicated in the pathophysiology of bipolar disorder. Relatively little research has focused on blood flow in the cerebellum of patients with bipolar disorder. Furthermore, the significance of metabolic changes in the brains of psychiatric patients may be confounded by the effects of various pharmacotherapies. Having previously found differences in cerebellar blood volume in patients with bipolar disorder compared to healthy control subjects, this study examined whether some variability in the patient population may be an effect of medication.

METHODS

In this study, we have examined the association between medication status and cerebellar blood volume. Thirteen healthy comparison subjects and 21 bipolar patients underwent dynamic susceptibility contrast magnetic resonance imaging. Nine cerebellar regions were identified, and the absolute cerebellar blood volume data from each was compared to medication status measures.

RESULTS

Patients on conventional antipsychotics had the lowest mean absolute blood volume measures for all cerebellar regions, whereas those on atypical antipsychotics had the highest blood volume measures. Comparison subjects had cerebellar blood volume measures in the middle, with results closer to subjects in the atypical group.

CONCLUSIONS

This evidence suggests that antipsychotic treatment may influence cerebellar blood volume. This effect will be important in considering imaging studies on medicated patients with bipolar disorder and may suggest novel pathways by which these medications affect their changes.

Neuroimaging evidence implicating cerebellum in the experience of hypercapnia and hunger for air

Recent neuroimaging and neurological data implicate cerebellum in nonmotor sensory, cognitive, vegetative, and affective functions. The present study assessed cerebellar responses when the urge to breathe is stimulated by inhaled CO(2). Ventilation changes follow arterial blood partial pressure CO(2) changes sensed by the medullary ventral respiratory group (VRG) and hypothalamus, entraining changes in midbrain, pons, thalamus, limbic, paralimbic, and insular regions. Nearly all these areas are known to connect anatomically with the cerebellum. Using positron emission tomography, we measured regional brain blood flow during acute CO(2)-induced breathlessness in humans. Separable physiological and subjective effects (air hunger) were assessed by comparisons with various respiratory control conditions. The conjoint physiological effects of hypercapnia and the consequent air hunger produced strong bilateral, near-midline activations of the cerebellum in anterior quadrangular, central, and lingula lobules, and in many areas of posterior quadrangular, tonsil, biventer, declive, and inferior semilunar lobules. The primal emotion of air hunger, dissociated from hypercapnia, activated midline regions of the central lobule. The distributed activity across the cerebellum is similar to that for thirst, hunger, and their satiation. Four possible interpretations of cerebellar function(s) here are that: it subserves implicit intentions to access air; it provides predictive internal models about the consequences of CO(2) inhalation; it modulates emotional responses; and that while some cerebellar regions monitor sensory acquisition in the VRG (CO(2) concentration), others influence VRG to adjust respiratory rate to optimize partial pressure CO(2), and others still monitor and optimize the acquisition of other sensory data in service of air hunger aroused vigilance.

Differences in cerebellar blood volume in schizophrenia and bipolar disorder

Brain morphometry has been studied extensively in schizophrenic patients, and among the cortical differences identified two consistent findings are decreased cerebellar vermal volume and increased volume of the fourth ventricle; although contradictory findings are reported as well. Recent cognitive activation studies utilizing PET, SPECT and fMRI have identified both decreased and increased activation in the cerebellum of schizophrenic patients compared with healthy controls. This study used DSC fMRI to map cerebellar blood volume in patients with schizophrenia or bipolar disorder and healthy controls. For all cerebellar regions analyzed, schizophrenic patients had the highest cerebellar blood volume, while bipolars had the lowest blood volume. Morphometric measurements were completed and indicated that the ratio of vermis to whole CBL tissue volume was 24% less for the schizophrenic population than controls, whereas the subjects with bipolar disorder had a ratio that was non-significantly smaller than controls by 19%. Comparison of morphometric data with blood volume data did not reveal any statistically significant correlations among the study groups.

Therapeutic and research implications

Investigations into the relationship between the cerebellum and nonmotor processing have produced a substantial body of evidence which seems to require a revision of accepted notions about the functional role of the cerebellum. This chapter presents a perspective on the contemporary and possible future therapeutic and research implications of these findings. These include the need for patients and their families to know of the behavioral consequences of cerebellar disease processes; potential approaches for improvement through rehabilitation therapies; and future treatment strategies, such as electrical stimulation of the cerebellum and psychosurgical approaches applied to the cerebellum. In addition, some areas of basic science investigation that could prove informative in understanding this relationship are addressed. It will be important to obtain a more complete characterization of the anatomy, physiology, and functional topography of the cerebellum in humans and in animal models, and a greater understanding of the clinical consequences of cerebellar lesions.

Rediscovery of an early concept

The study of the cerebellum has been dominated by interest in its role in movement and motor control. From the earliest days of the neuroscientific era, however, clinical reports and physiological and behavioral investigations have suggested that overt motor dysfunction is but one manifestation of cerebellar disease. The nature of cerebellar involvement in autonomic, sensory, and cognitive functions has been investigated for many years, and possible mechanisms that could subserve this relationship have been specifically addressed. This work has not been incorporated into the mainstream of neuroscience or clinical neurological thinking. This chapter traces the history of these early investigations that demonstrated the need to revise the notion that cerebellar function is confined to the motor realm. The collaboration across disciplines and the advances in the methods and concepts of contemporary neuroscience have facilitated the maturation of this field of inquiry. The "new" story of the cerebellum and cognition, in fact, represents the evolution of a century-old revolutionary concept.