A patchy horizontal organization of the somatosensory activation of the rat cerebellum demonstrated by functional MRI (original) (raw)
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Analysis of the pattern of functional activation of the cerebellum and its topographical correlation
Radiología (English Edition), 2020
Objectives: To describe the normal patterns of cerebellar activation in specific cerebral functions (motor, language, memory) and their topographical correlations in the cerebellar cortex on functional magnetic resonance imaging. Materials and methods: We evaluated 25 healthy subjects (8 women and 17 men; 23 righthanded and 2 left-handed; age range, 16-64 years), who did language, memory, and motor tasks while undergoing 1.5 T functional magnetic resonance imaging. Results: We assessed functional activity of the cerebellum associated with motor, language, and memory components, describing their relations with topographical regions of the cerebellum and their functional relations with areas in the cerebral cortex. Conclusions: Knowledge of the normal patterns of morphological characteristics and functional behaviour in the cerebellum as well as their relations with the brain is important for radiologists and clinicians evaluating the cerebellum and possible pathological conditions that affect it.
Somatotopic motor representation in the human anterior cerebellum
Brain, 1996
Though somatotopic encoding of function is a prominent feature in brain structures involved in sensori-motor processing, it has not been well established for the human cerebellum. We delineated the representation of hand, foot and tongue movements in the anterior cerebellar lobe of eight healthy subjects using dynamic high-resolution MRI sensitized to changes in cerebral blood oxygenation (CBO). Activation was determined by pixel-by-pixel correlation of signal intensity time courses with the performance protocol.
Human Brain Mapping, 1999
We combined information from functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) to assess which cortical areas and in which temporal order show macroscopic activation after right median nerve stimulation. Five healthy subjects were studied with the two imaging modalities, which both revealed significant activation in the contra-and ipsilateral primary somatosensory cortex (SI), the contra-and ipsilateral opercular areas, the walls of the contralateral postcentral sulcus (PoCS), and the contralateral supplementary motor area (SMA). In fMRI, two separate foci of activation in the opercular cortex were discerned, one posteriorly in the parietal operculum (PO), and one anteriorly near the insula or frontal operculum (anterior operculum, AO). The activation sites from fMRI were used to constrain the solution of the inverse problem of MEG, which allowed us to construct a model of the temporal sequence of activation of the different sites. According to this model, the mean onset latency for significant activation at the contralateral SI was 20 msec (range, 17-22 msec), followed by activation of PoCS at 23 msec (range, 21-25 msec). The contralateral PO was activated at 26 msec (range, 19-32 msec) and AO at 33 msec (range, 22-51 msec). The contralateral SMA became active at 36 msec (range, 24-48 msec). The ipsilateral SI, PO, and AO became activated at 54-67 msec. We conclude that fMRI provides a useful means to constrain the inverse problem of MEG, allowing the construction of spatiotemporal models of cortical activation, which may have significant implications for the understanding of cortical network functioning.
BOLD and CBV-weighted functional magnetic resonance imaging of the rat somatosensory system
Magnetic Resonance in Medicine, 2006
A multislice spin echo EPI sequence was used to obtain functional MR images of the entire rat brain with blood oxygenation level dependent (BOLD) and cerebral blood volume (CBV) contrast at 11.7 T. Maps of activation incidence were created by warping each image to the Paxinos rat brain atlas and marking the extent of the activated area. Incidence maps for BOLD and CBV were similar, but activation in draining veins was more prominent in the BOLD images than in the CBV images. Cerebellar activation was observed along the surface in BOLD images, but in deeper regions in the CBV images. Both effects may be explained by increased signal dropout and distortion in the EPI images after administration of the ferumoxtran-10 contrast agent for CBV fMRI. CBV-weighted incidence maps were also created for 10, 20, and 30 mg Fe/kg doses of ferumoxtran-10. The magnitude of the average percentage change during stimulation increased from 4.9% with the 10 mg Fe/kg dose to 8.7% with the 30-mg Fe/kg dose. Incidence of activation followed a similar trend. Magn Reson Med, 2006. Published 2005 Wiley-Liss, Inc.
A Topographic analysis of limbic and somatic inputs to the cerebellar cortex in the rat
Experimental Brain Research, 1980
The effects of electrical stimulation of the fornix, snout, and limbs on the activity of electrophysiologically identified Purkinje cells were investigated. Extracellularly recorded responses were analyzed according to: latency; mode of termination as mossy or climbing fibers; and, whether excitatory or inhibitory responses were evoked. The positions of responsive cells were transposed onto a planar representation of the Purkinje cell layer of the rat cerebellum derived from a series of sagittal sections. Fornix responsive cells were found in the vermis of lobules IV, V, VI, and VII as well as in the paravermal regions of lobules II-VIIb. In addition, some evidence was obtained for a projection to lobulus simplex. Snout stimulation activated cells mainly in the vermis of lobule VI and also in adjacent lobules III, IV, V, and VIIa. A few responsive cells were also found in the paravermal regions of lobules V, VI, and VIIa and in the lateral portion of lobulus simplex. Forelimb responsive cells were located mainly in the vermis of lobules IV-VIa and in the paravermal portion of lobules III-VII. The few hindlimb cells encountered were located in the vermis and paravermis of lobules II-IV. The topographical overlap of the fornix projection with areas in receipt of forelimb, snout, neck, and auditory-visual teleceptor input suggests that the fornix-mediated information may modulate cerebellar circuits involved in postural adjustment, general orienting, and exploratory motor behavior.
Detectability of cerebellar activity with magnetoencephalography and electroencephalography
Human Brain Mapping, 2020
Electrophysiological signals from the cerebellum have traditionally been viewed as inaccessible to magnetoencephalography (MEG) and electroencephalography (EEG). Here, we challenge this position by investigating the ability of MEG and EEG to detect cerebellar activity using a model that employs a high‐resolution tessellation of the cerebellar cortex. The tessellation was constructed from repetitive high‐field (9.4T) structural magnetic resonance imaging (MRI) of an ex vivo human cerebellum. A boundary‐element forward model was then used to simulate the M/EEG signals resulting from neural activity in the cerebellar cortex. Despite significant signal cancelation due to the highly convoluted cerebellar cortex, we found that the cerebellar signal was on average only 30–60% weaker than the cortical signal. We also made detailed M/EEG sensitivity maps and found that MEG and EEG have highly complementary sensitivity distributions over the cerebellar cortex. Based on previous fMRI studies c...
European Journal of Neuroscience, 2006
The granule cell layer of the cerebellar hemispheres contains a patchy and noncontinuous map of the body surface, consisting of a complex mosaic of multiple perioral tactile representations. Previous physiological studies have shown that cerebrocerebellar mossy fibre projections, conveyed through the pontine nuclei, are mapped in registration with peripheral tactile projections to the cerebellum. In contrast to the fractured cerebellar map, the primary somatosensory cortex (SI) is somatotopically organized. To understand better the map transformation occurring in cerebrocerebellar pathways, we injected axonal tracers in electrophysiologically defined locations in Sprague-Dawley rat folium crus IIa, and mapped the distribution of retrogradely labelled neurons within the pontine nuclei using three-dimensional (3-D) reconstructions. Tracer injections within the large central upper lip patch in crus IIa-labelled neurons located centrally in the pontine nuclei, primarily contralateral to the injected side. Larger injections (covering multiple crus IIa perioral representations) resulted in labelling extending only slightly beyond this region, with a higher density and more ipsilaterally labelled neurons. Combined axonal tracer injections in upper lip representations in SI and crus IIa, revealed a close spatial correspondence between the cerebropontine terminal fields and the crus IIa projecting neurons. Finally, comparisons with previously published three-dimensional distributions of pontine neurons labelled following tracer injections in face receiving regions in the paramedian lobule (downloaded from http://www.rbwb.org) revealed similar correspondence. The present data support the coherent topographical organization of cerebro-ponto-cerebellar networks previously suggested from physiological studies. We discuss the present findings in the context of transformations from cerebral somatotopic to cerebellar fractured tactile representations.
Cerebellar Functional Anatomy: a Didactic Summary Based on Human fMRI Evidence
The Cerebellum, 2019
The cerebellum is relevant for virtually all aspects of behavior in health and disease. Cerebellar findings are common across all kinds of neuroimaging studies of brain function and dysfunction. A large and expanding body of literature mapping motor and non-motor functions in the healthy human cerebellar cortex using fMRI has served as a tool for interpreting these findings. For example, results of cerebellar atrophy in Alzheimer's disease in caudal aspects of Crus I/II and medial lobule IX can be interpreted by consulting a large number of task, resting-state, and gradient-based reports that describe the functional characteristics of these specific aspects of the cerebellar cortex. Here, we provide a concise summary that outlines organizational principles observed consistently across these studies of normal cerebellar organization. This basic framework may be useful for investigators performing or reading experiments that require a functional interpretation of human cerebellar topography.