Hemisphere Lobe Research Articles

Differential cerebellar activation related to perceived pain intensity during noxious thermal stimulation in humans: a functional magnetic resonance imaging study

Little is known about the cerebellar involvement in pain processing in spite of the fact that the cerebellum probably plays a crucial role in pain-related behavior. Using functional magnetic resonance imaging we examined the differential cerebellar activation in 18 healthy subjects in relation to their perceived pain-intensity of noxious and non-noxious thermal stimuli. In contrast to non-noxious (40°C) stimuli, noxious (48.5°C) stimuli revealed activation in the deep cerebellar nuclei, anterior vermis and bilaterally in the cerebellar hemispheric lobule VI. With the same noxious stimulus (48.5°C) there was differential cerebellar activation depending on the perceived pain intensity: high pain intensity ratings were associated with activation in ipsilateral hemispheric lobule III–VI, deep cerebellar nuclei and in the anterior vermis (lobule III). This differential cerebellar activation pattern probably reflects not only somatosensory processing but also perceived pain intensity that may be important for cerebellar modulation of nociceptive circuits.

Eyeblink-related areas in human cerebellum as shown by fMRI.

Classical eyeblink conditioning is used frequently to study the role of the cerebellum in associative learning. To understand the mechanisms involved in learning, the neural circuits that generate the eyeblink response should be identified. The goal of the present study was to examine cerebellar regions that are likely to control the human eyeblink response using event-related functional magnetic resonance imaging (fMRI). In 14 healthy volunteers eyeblinks were evoked by unilateral air-puff stimulation (total of 30 stimuli, inter-trial interval 27-44 sec). With eyes closed throughout the experiment, eyeblinks were recorded using a video-based system with infrared reflecting markers being attached to the upper eyelids. From each subject 500 scans were taken (TR = 2.2 sec, 22 slices per scan, slice thickness = 3 mm) using an echo planar imaging sequence (EPI). The statistical parametric maps of the experimental volume images were estimated with SPM99 specifying an appropriate event-related design matrix. Two main regions of significant activation were found in the ipsilateral posterior lobe of the cerebellar hemisphere. In the more anterior region the maxima of activation were located in hemispheral lobules VI and Crus I, and in the more posterior region in hemispheral lobules VIIb, Crus II and VIIIa (nomenclature according to Schmahmann et al. [2000]: MRI Atlas of the Human Cerebellum). Although less pronounced, activity was found also in corresponding areas of the contralateral cerebellar hemisphere. These eyeblink-related areas agree with trigeminal projection areas and blink reflex control areas shown in previous animal studies.

Corticopontocerebellar pathway from the prearcuate region to hemispheric lobule VII of the cerebellum: an anterograde and retrograde tracing study in the monkey

The relationship between axons derived from the prearcuate region and pontine neurons projecting to contralateral cerebellar hemispheric lobule VII, lobulus petrosus (LP) of the paraflocculus or the dorsal paraflocculus (DPFl) was investigated in the monkey. The frontopontine axons were labeled with biotinylated dextran and pontocerebellar neurons with cholera toxin subunit B or fast blue. Labeled frontopontine axons and terminals were seen in the dorsal, medial, paramedian and dorsolateral parts of the pontine nuclei. The distribution of the labeled frontopontine axons overlapped that of labeled neurons projecting to hemispheric lobule VII but did not overlap that of labeled neurons projecting to LP or DPFl. The pathway from the prearcuate region to hemispheric lobule VII may provide an anatomical substrate for the involvement of hemispheric lobule VII in voluntary eye movements.

The p38 Mitogen-Activated Protein Kinase Is Involved in Associative Learning in Rabbits

This study examined the role of the mitogen-activated protein kinase (MAPK) family during acquisition of the rabbit's classically conditioned eye-blink response. Eye-blink conditioning produced a significant, bilateral activation of both extracellular signal-regulated protein kinases (ERKs) and p38 MAPK in the anterior cerebellar vermis. There was also a significant bilateral activation of ERKs in the dorsal hippocampus with no change in p38 MAPK. These changes were seen at 2 min after the last conditioning session, were maintained for at least 180 min, and occurred without any change in the protein expression of either ERKs or p38 MAPK. There were no changes in ERKs or p38 MAPK in frontal cortex, in cerebellar hemispheral lobule VI, or in a section of brainstem containing the inferior olive. Moreover, the stress-related protein kinase Jun N-terminal kinase (JNK), another subfamily of MAPKs, was not altered in any of the brain regions examined. Animals receiving explicitly unpaired presentations of a conditioned stimulus and an unconditioned stimulus did not acquire conditioned responses (CRs) and did not demonstrate any changes in ERKs, p38 MAPK, or JNK. The intraventricular injection of SB203580, a selective p38 MAPK inhibitor, significantly retarded CR acquisition and blocked the learning-related increases in p38 MAPK activity in the anterior vermis. PD98059, a selective MAPK kinase inhibitor, had a smaller and only marginally significant effect on CR acquisition, although it did block the learning-related increases in ERK activity in both the hippocampus and anterior vermis. These results indicate that p38 MAPK is activated during associative learning and may play a role in the transcriptional events that lead to memory consolidation.

Case study Cognitive outcome after emergent treatment of acute herpes simplex encephalitis with acyclovir

Longitudinally designed case studies, reporting cognitive and psychosocial outcome of herpes simplex virus encephalitis (HSVE), were conducted prior to current antiviral medication usage and primarily in persons with either left hemispheric or bilateral temporal lobe involvement. The current study demonstrated relatively better outcome (cognitive recovery and functional independence for activities of daily life) in an individual treated with IV Acyclovir within hours of initial symptoms and whose CT scans showed right hemispheric involvement. In contrast with earlier case reports, no semantic specific categories of memory impairment were noted on serial assessment. The time from first symptoms to antiviral medical treatment appears to be the best predictor of outcome from HSVE. Historical case studies with relatively poorer outcome and differing deficits suggest survivors of HSVE are a heterogenous group. Variability in anatomic lesions and time to treatment contribute to outcome.

Neuropsychological testing in obsessive-compulsive disorder: a clinical review.

The role of neuropsychological testing in assessment of obsessive-compulsive disorder (OCD) is examined by review of 8 case reports and 14 patient series. Investigators generally agreed on localization of dysfunctional areas (e.g., prefrontal and frontal regions, limbic system, basal ganglia). They disagreed as to hemisphere and frontal lobe side impairment, involvement of other brain areas, pathophysiological connections, and impact of developmental phases and of concomitant cognitive and affective conditions. Conclusions about OCD pathogenesis are limited by test and sample variability. The authors outline an integrative approach based on sensorial and cognitive information disruptions that require activation of less specialized circuits. OCD may be syndromic, and subgroups may exist based on related but differentiable biochemical pathways.

Multiple-unit activity from rabbit cerebellar cortex and interpositus nucleus during classical discrimination/reversal eyelid conditioning

Multiple-unit activity was monitored in the hemispheric lobule VI (HVI) and the interpositus nucleus of the cerebellum during classical discrimination and reversal eyelid conditioning in rabbits. During both phases of conditioning similar patterns of activity were observed in lobule HVI: conditioned response (CR)-related activity was present on conditioned stimulus (CS)+ trials but not on CS — trials. Activity in the interpositus nucleus differed during the two phases of conditioning. After discrimination training, CR-related activity was present on CS + but not CS— trials. After reversal training, however, only a weak activation of the interpositus nucleus was seen on CS + trials with no activation present on CS — trials. These data suggest that lobule HVI and the interpositus nucleus may play different roles in classical eyelid conditioning.

Magnetotail views at 33RE: IMP 8 magnetometer observations

This paper presents magnetic field vector (B) maps, electric current vector (curl B) maps, magnetic force (J×B) contour maps, and total field contour maps covering the full tail cross section in the yz plane. The maps are based on 16 years of 5‐min averages of IMP 8 magnetic field data. During this time, IMP 8 traversed the tail between −25RE and −40RE in the x direction. Its average x distance was −33RE. For this average distance we show separate maps for low and high dipole tilts, corresponding to equinox and northern hemisphere summer seasons. The low‐tilt (equinox) maps show symmetrical field and current patterns; the high‐tilt (solstice) maps show the cross‐tail current sheet arcing above the equatorial diagonal in the center and dipping below it on the flanks. The shape of warped current sheet fits Fairfield's (1980) displaced ellipse model fairly well. The distance at which the current sheet is hinged to the magnetic equator is found to be 9.88RE and is independent of kp. The z profile of current density shows a central peak, 3RE full width at half maximum, and smaller, flanking shoulders. A Harris sheet profile with a 7RE thickness fits the Bx profile. Though these are magnetic field data, the J×B maps clearly outline the plasma sheet. This approach also gives a 7RE thickness. Many of the average field and current features inferred and demonstrated in earlier studies are confirmed here; some of them are seen for the first time in full cross‐section view. Among new features revealed are a large current vortex in the winter hemisphere lobe, a dawn‐dusk asymmetry in the J×B force in the plasma sheet (it is stronger on the duskside), and a separation of the cross‐tail current sheet into core and wing parts.

Recoverable and nonrecoverable deficits in conditioned responses after cerebellar cortical lesions

This study reexamined the effects of unilateral damage to cerebellar hemispheral lobule VI on the rabbit's conditioned nictitating membrane (NM) response. Extensive unilateral removal of hemispheral lobule VI in 11 rabbits impaired ipsilateral conditioned responses as reflected by reductions of 52% in mean frequency and 53% in mean amplitude during test trials on the first postoperative session. The decreases in the amplitude and frequency of conditioned responses were highly correlated (r = 0.82). The frequency of conditioned responses recovered to control levels but their amplitudes remained reduced such that the correlation between these two measures of responding was no longer significant by the 12th postoperative conditioning session. The decrease in the amplitude of conditioned responses was not accompanied by changes in onset latency or rise time. There was no significant impairment of conditioned responses in surgical controls and animals with only partial damage to hemispheral lobule VI. It was concluded that hemispheral lobule VI plays an important role in the regulation of motor centers in the brainstem so as to facilitate the initiation and optimum execution of the conditioned NM reflex. This cortical regulation of the conditioned NM response may contain learned elements; however, these cannot be resolved with lesion methods, nor has their existence been proven in this or other lesion studies. Nevertheless, the results of this study do demonstrate that the cerebellar cortex cannot be considered as the single locus necessary for NM conditioning.

Pressure balance between lobe and plasma sheet

Using eight months of AMPTE/IRM plasma and magnetic field data, we have done a statistical survey on the balance of total (thermal and magnetic) pressure in the Earth's plasma sheet and tail lobe. About 300,000 measurements obtained in the plasma sheet and the lobe were compared for different levels of magnetic activity as well as different distances from the Earth. Our data show that lobe and plasma sheet pressure balance very well. Even in the worst case they do not deviate by more than half of the variance in the data itself. Approximately constant total pressure was also seen during a quiet time pass when IRM traversed nearly the whole magnetotail in the vertical direction, from the southern hemisphere lobe through the neutral sheet and into the northern plasma sheet boundary layer.

The cerebellum in sagittal plane--anatomic-MR correlation: 2. The cerebellar hemispheres.

Thin (5-mm) sagittal high-field (1.5-T) MR images of the cerebellar hemispheres display (1) the superior, middle, and inferior cerebellar peduncles; (2) the primary white-matter branches to the hemispheric lobules including the central, anterior, and posterior quadrangular, superior and inferior semilunar, gracile, biventer, tonsil, and flocculus; and (3) several finer secondary white-matter branches to individual folia within the lobules. Surface features of the hemispheres including the deeper fissures (e.g., horizontal, posterolateral, inferior posterior, and inferior anterior) and shallower sulci are best delineated on T1-weighted (short TR/short TE) and T2-weighted (long TR/long TE) sequences, which provide greatest contrast between CSF and parenchyma. Correlations of MR studies of three brain specimens and 11 normal volunteers with microtone sections of the anatomic specimens provides criteria for identifying confidently these structures on routine clinical MR. MR should be useful in identifying, localizing, and quantifying cerebellar disease in patients with clinical deficits.

Inferior olivary nuclear complex of the rat: Morphology and comments on the principles of organization within the olivocerebellar system

This study was undertaken (1) to provide a description of the normal morphology and anatomical interrelationships within the inferior olivary cell groups and (2) to determine the topographical organization of projections from this nuclear complex to the cerebellum. Conventional histological methods and the technique of retrograde transport of horseradish peroxidase (HRP) and WGA-HRP in conjunction with the sensitive chromogen tetramethyl benzidine were used in this series of experiments. In common with that of other animals, the inferior olivary nucleus of the rat consists of three subdivisions: the medial accessory olive (MAO), dorsal accessory olive (DAO), and principal olive (PO). The MAO is made of several subnuclei including a, b, c, and nucleus beta. On the basis of their common connections, the smaller subnuclei, dorsal cap, ventrolateral outgrowth, and dorsomedial cell column can be considered as parts of the MAO. The DAO is made of two subdivisions or lamellae--the dorsal and ventral folds--joined together laterally to form a twisted V-shaped structure. The principal olive consists of dorsal and ventral lamellae. A point-to-point projection was determined for four areas of the cerebellum: the anterior lobe, the posterior vermis, the intermediate and the lateral cerebellum. Analysis of the details of the projection system revealed that distinct groups of cells, here referred to as lamellae, project to sagittal zones of the cerebellum. (1) The medial accessory olive appears to be composed of three lamellae: horizontal, vertical, and rostral. The horizontal lamella (elsewhere denoted as groups a and b) projects to a sagittal zone in the vermal anterior lobe. The vertical lamella (groups c, beta, dorsal cap, ventrolateral outgrowth, and dorsomedial cell column) projects to a sagittal zone in the posterior vermis and the flocculus, and the rostral lamella projects to the lateral cerebellum. (2) The dorsal accessory olive is composed of two distinct lamellae which we have previously denoted as the dorsal and ventral folds. The dorsal fold projects to the vermal anterior lobe and receives afferents from the spinal cord, whereas the ventral fold projects to a sagittal zone in the intermediate cerebellum and receives afferents primarily from dorsal column nuclei. (3) The principal olive contains the two familiar lamellae: dorsal and ventral lamellae, each of which projects to a specific sagittal strip in the lateral cerebellum.(ABSTRACT TRUNCATED AT 400 WORDS)

Intra- and interhemispheric collateral branching in the rat pontocerebellar system, a fluorescence double-label study

A double-labeling method which employed the injection and subsequent retrograde transport of two different fluorescent dyes was utilized to investigate the possibility that some pontocerebellar neurons might give rise to collateral branches which distributed to more than one lobule of the contralateral lateral cerebellar hemisphere (intrahemispheric branching) or bilaterally to homotopic or heterotopic lobules in both lateral hemispheres (interhemispheric branching). With regard to intrahemispheric branching, these studies revealed the largest number of double-labeled neurons when the dye injections involved a combination of crus I and the paraflocculus. A considerable number of double-labeled cells were also observed in simplex-crus II cases while a modest number were noted in crus I-paramedian and simplex-paramedian combinations. Evidence for interhemispheric branching was also apparent but the number of double-labeled cells was generally less than that observed in the intrahemispheric experiments. Following bilateral injections, a modest number of double-labeled cells was noted with simplex-simplex and crus I-Crus I homotopic injections and crus II-paramedian heterotopic combinations. In contrast to those cases with unilateral injections, not all bilateral injection combinations produced double-labeling, the most conspicuous in this regard being homotopic and heterotopic injections involving the paraflocculus. Overall, the population of double-labeled cells included many varieties of pontine neurons ranging from small, spindle-shaped to large multipolar. No clear topographic patterns emerged when the location or distribution of either intrahemispheric or interhemispheric double-labeled cells was compared. It was noted, however, that most double-labeled neurons were situated in zones of overlap that occurred between single-labeled neurons projecting to one or the other of the injected lobules. Conversely, in some situations, sharp borders were maintained between adjacent groups of single-labeled neurons. These studies have demonstrated the existence of both intrahemispheric and interhemispheric branching in the pontocerebellar system. The interhemispheric category included pontine neurons which distributed bilaterally to either homotopic or heterotopic lobules in each hemisphere. The overall distribution pattern of double-labeled pontine neurons, those whose axons distribute to more than one hemispheral lobule, is extremely complex and, although some trends were noted, no system-wide topographic organization was apparent. The category of double-labeled neurons included a wide variety of shapes and sizes ranging from the smallest to the largest types of pontine neurons. Most double-labeled neurons were intermixed with single-labeled pontine cells which projected to one or the other of the two injected lobules. No cluster of pontine neurons composed exclusively of double-labeled cells was ever observed although on some occasions, only one population of single-labeled pontine neuron was interspersed with double-labeled cells.