Crystal structure of PAV1-137: a protein from the virus PAV1 that infects Pyrococcus abyssi.

Pyrococcus abyssi virus 1 (PAV1) was the first virus particle infecting a hyperthermophilic Euryarchaeota (Pyrococcus abyssi strain GE23) that has been isolated and characterized. It is lemon shaped and is decorated with a short fibered tail. PAV1 morphologically resembles the fusiform members of the family Fuselloviridae or the genus Salterprovirus. The 18 kb dsDNA genome of PAV1 contains 25 predicted genes, most of them of unknown function. To help assigning functions to these proteins, we have initiated structural studies of the PAV1 proteome. We determined the crystal structure of a putative protein of 137 residues (PAV1-137) at a resolution of 2.2 Å. The protein forms dimers both in solution and in the crystal. The fold of PAV1-137 is a four- α -helical bundle analogous to those found in some eukaryotic adhesion proteins such as focal adhesion kinase, suggesting that PAV1-137 is involved in protein-protein interactions.

Analysis of the first genome of a hyperthermophilic marine virus-like particle, PAV1, isolated from Pyrococcus abyssi.

Only one virus-like particle (VLP) has been reported from hyperthermophilic Euryarchaeotes. This VLP, named PAV1, is shaped like a lemon and was isolated from a strain of "Pyrococcus abyssi," a deep-sea isolate. Its genome consists of a double-stranded circular DNA of 18 kb which is also present at a high copy number (60 per chromosome) free within the host cytoplasm but is not integrated into the host chromosome. Here, we report the results of complete analysis of the PAV1 genome. All the 25 predicted genes, except 3, are located on one DNA strand. A transcription map has been made by using a reverse transcription-PCR assay. All the identified open reading frames (ORFs) are transcribed. The most significant similarities relate to four ORFs. ORF 180a shows 31% identity with ORF 181 of the pRT1 plasmid isolated from Pyrococcus sp. strain JT1. ORFs 676 and 678 present similarities with a concanavalin A-like lectin/glucanase domain, which could be involved in the process of host-virus recognition, and ORF 59 presents similarities with the transcriptional regulator CopG. The genome of PAV1 displays unique features at the nucleic and proteinic level, indicating that PAV1 should be attached at least to a novel genus or virus family.

Genetic elements of Thermococcales.

This minireview summarizes our current knowledge about archaeal genetic elements in the hyperthermophilic order Thermococcales in the phylum Euryarchaeota. This includes recent work on the first virus of Pyrococcus, PAV1, the discovery of novel unique virus morphotypes in hot deep-sea environments, and preliminary observations on novel cryptic plasmids. We also review the work accomplished over the last 5 years in the development of genetic tools for members of the Pyrococcus and Thermococcus genera, mainly in our laboratories.

EMG remains fractionated in Parkinson's disease, despite practice-related improvements in performance.

OBJECTIVE: We studied the ability of patients with Parkinson's disease to improve their performance in a motor task requiring both speed and accuracy in the execution of elbow flexion movements. Our goal was to investigate the changes in electromyographic activity associated with the changes in movement performance. METHODS: Eleven patients on anti-Parkinsonian medication were tested. The patients were selected for being bradykinetic, having little or no resting tremor or dyskinesias, and being in stages II or III of the Hoehn and Yahr rating scale. RESULTS: The untrained patients displayed multiple bursts of agonist activity, characteristic of Parkinsonian EMG recordings. All patients improved their performance by increasing peak velocity while maintaining movement accuracy within strict boundaries. With practice, the patients' performance changed in a manner similar to that which has been previously observed for performance curves in neurologically normal subjects. As movement duration decreased (i.e. peak velocity increased), we observed a slight decrease in the number of agonist bursts and an increase in the average burst duration. However, the patients continued to generate a fractionated, multi-burst agonist pattern. CONCLUSIONS: We conclude that Parkinsonian patients benefit from practice by improving their performance but remain fundamentally impaired in the generation of muscle activation patterns. This study has shown that the generation of fractionated, multiple short bursts of EMG activity that is characteristic of movements made by Parkinsonian patients is not normalized by practice.

Characterization of two DNA polymerases from the hyperthermophilic euryarchaeon Pyrococcus abyssi.

The complete genome sequence of the hyperthermophilic archaeon Pyrococcus abyssi revealed the presence of a family B DNA polymerase (Pol I) and a family D DNA polymerase (Pol II). To extend our knowledge about euryarchaeal DNA polymerases, we cloned the genes encoding these two enzymes and expressed them in Escherichia coli. The DNA polymerases (Pol I and Pol II) were purified to homogeneity and characterized. Pol I had a molecular mass of approximately 90 kDa, as estimated by SDS/PAGE. The optimum pH and Mg(2+) concentration of Pol I were 8.5-9.0 and 3 mm, respectively. Pol II is composed of two subunits that are encoded by two genes arranged in tandem on the P. abyssi genome. We cloned these genes and purified the Pol II DNA polymerase from an E. coli strain coexpressing the cloned genes. The optimum pH and Mg(2+) concentration of Pol II were 6.5 and 15-20 mm, respectively. Both P. abyssi Pol I and Pol II have associated 3'-->5' exonuclease activity although the exonuclease motifs usually found in DNA polymerases are absent in the archaeal family D DNA polymerase sequences. Sequence analysis has revealed that the small subunit of family D DNA polymerase and the Mre11 nucleases belong to the calcineurin-like phosphoesterase superfamily and that residues involved in catalysis and metal coordination in the Mre11 nuclease three-dimensional structure are strictly conserved in both families. One hypothesis is that the phosphoesterase domain of the small subunit is responsible for the 3'-->5' exonuclease activity of family D DNA polymerase. These results increase our understanding of euryarchaeal DNA polymerases and are of importance to push forward the complete understanding of the DNA replication in P. abyssi.

Characterization of a highly thermostable alkaline phosphatase from the euryarchaeon Pyrococcus abyssi.

This work reports the first isolation and characterization of an alkaline phosphatase (AP) from a hyperthermophilic archaeon. An AP gene from Pyrococcus abyssi, a euryarchaeon isolated from a deep-sea hydrothermal vent, was cloned and the enzyme expressed in Escherichia coli. Analysis of the sequence showed conservation of the active site and structural elements of the E. coli AP. The recombinant AP was purified and characterized. Monomeric and homodimeric active forms were detected, with a monomer molecular mass of 54 kDa. Apparent optimum pH and temperature were estimated at 11.0 and 70 degrees C, respectively. Thus far, P. abyssi AP has been demonstrated to be the most thermostable AP, with half-lives at 100 and 105 degrees C of 18 and 5 h, respectively. Enzyme activity was found to be dependent on divalent cations: metal ion chelators inhibited activity, whereas the addition of exogenous Mg(II), Zn(II), and Co(II) increased activity. The enzyme was inhibited by inorganic phosphate, but not by molybdate and vanadate. Strong inhibitory effects were observed in the presence of thiol-reducing agents, although cysteine residues of the P. abyssi AP were not found to be incorporated within intra- or interchain disulfide bonds. In addition, P. abyssi AP was demonstrated to dephosphorylate linear DNA fragments with dephosphorylation efficiencies of 93.8 and 84.1% with regard to cohesive and blunt ends, respectively.

Time course and temporal order of changes in movement kinematics during motor learning: effect of joint and instruction.

Learning a motor task is associated with specific changes in movement kinematics. Recently, it has been shown that changes in different kinematic parameters occurred with different time courses for subjects who practiced simple, single-joint elbow movements. For example, movement time was seen to decrease and level off in a shorter time than peak velocity, which increased and plateaued later. What is not known, however, is whether the time course and temporal order of these learning-related changes seen at the elbow are similar for movements learned at other joints and with different instructions. In this study, neurologically normal subjects practiced 50 degrees -flexion movements made at the wrist, with the instruction to be both "fast and accurate" (same instruction used in the earlier elbow study). A different group of subjects practiced wrist movements of the same amplitude, but with instructions to make movements that were "always accurate;" only as movement skill developed could subjects increase their speed (but without ever sacrificing accuracy). We measured time-related parameters (duration of acceleration, duration of deceleration, and total movement duration) and magnitude-related parameters (peak velocity, peak acceleration, and peak deceleration). We found that the time course of changes in kinematic parameters for subjects instructed to be "fast and accurate" was similar to that reported at the elbow. When the instruction was changed to be "always accurate," the time for changes in kinematic parameters to level off was found to be longer. However, regardless of instruction, time-related parameters plateaued before magnitude-related parameters. Thus, our results indicate that motor learning mechanisms may operate in a similar way at different joints.

Characterization of the maltooligosyl trehalose synthase from the thermophilic archaeon Sulfolobus acidocaldarius.

We report the molecular characterization and the detailed study of the recombinant maltooligosyl trehalose synthase mechanism from the thermoacidophilic archaeon Sulfolobus acidocaldarius. The mts gene encoding a maltooligosyl trehalose synthase was overexpressed in Escherichia coli using the T7-expression system. The purified recombinant enzyme exhibited optimum activity at 75 degrees C and pH 5 with citrate-phosphate buffer and retained 60% of residual activity after 72 h of incubation at 80 degrees C. The recombinant enzyme was active on maltooligosaccharides such as maltotriose, maltotetraose, maltopentaose and maltoheptaose. Investigation of the enzyme action on maltooligosaccharides has brought much insight into the reaction mechanism. Results obtained from thin-layer chromatography suggested a possible mechanism of action for maltooligosyl trehalose synthase: the enzyme, after converting the alpha-1,4-glucosidic linkage to an alpha-1,1-glucosidic linkage at the reducing end of maltooligosaccharide glc(n) is able to release glucose and maltooligosaccharide glc(n-1) residues. And then, the intramolecular transglycosylation and the hydrolytic reaction continue, with the maltooligosaccharide glc(n-1) until the initial maltooligosaccharide is reduced to maltose. An hypothetical mechanism of maltooligosyl trehalose synthase acting on maltooligosaccharide is proposed.

Representation of accuracy in the dorsal premotor cortex.

The endpoint accuracy of a reaching movement strongly affects kinematics, particularly during the final phases of movement. However, where and how accuracy is represented in the central nervous system remains unknown. In this study, the discharge of 150 neurons located primarily in the dorsal premotor cortex (PMd), were recorded from monkeys performing an instructed delay, centre-out reaching task in which movement direction and target size were systematically varied. Linear regression analyses were used to assess the dependence of movement kinematics and cell discharge on target direction, size and tangential velocity (i.e. speed). The speed and timing of the movement were dependent on both direction and target size. Initially direction was the dominant predictor whilst target size became more important as the hand reached the target. A temporal multiple linear regression analysis found significant correlations with target size in 99 of 150 cells. The discharge of 134 cells was directionally tuned and 83 cells modulated with mean speed. Significant correlations of discharge with target size occurred throughout the task as did correlations with direction. However, correlations with direction preferentially occurred early in the task, prior to movement onset, whilst correlations with target size tended to occur late, well after movement onset. This temporal dependency of the firing in relationship to target direction and size mirrored that observed for the kinematics. We conclude that the discharge of PMd cells is highly correlated with the accuracy requirement of the movement. The timing of the correlations suggest that accuracy information is available for the planning and for the on-line control of endpoint accuracy.

Expression, purification, crystallization and preliminary X-ray analysis of the iota-carrageenase from Alteromonas fortis.

This is the first crystallization report of a glycoside hydrolase which belongs to family 82. A recombinant form of His-tagged iota-carrageenase from Alteromonas fortis was expressed, purified and crystallized. Crystals were obtained by the vapour-diffusion method using polyethylene glycol (M(W) = 6000) as a precipitant. They belong to space group P2(1), with unit-cell parameters a = 56. 75, b = 91.04, c = 125.01 A, beta = 93.41 degrees. The unit cell contains two molecules in the asymmetric unit related by a non-crystallographic twofold axis. Crystals diffracted to 2.0 A resolution on a synchrotron beamline.

Impaired compensation for mechanical loads in a patient with hemiballismus following stroke.

Flexion movements of the wrist were studied in a patient who showed signs of hemiballismus following a unilateral infarction, which damaged the region neighboring the subthalamic nucleus. The experiments were designed to test whether a lesion of this nature impairs load compensation and, specifically, whether antagonist activity can be appropriately suppressed when initiating a movement. The latency between movement onset and agonist EMG onset changed from the normal relationship where agonist onset precedes movement to one where agonist onset followed movement when an extensor load was placed on the affected limb. This was found to result from the inability to inhibit tonic activity in the antagonist and simultaneously activate the agonist muscle. The results suggest that the indirect pathway through the basal ganglia may be necessary to compensate for mechanical loads and to suppress antagonist activity when a movement is initiated.

Time course and temporal order of changes in movement kinematics during learning of fast and accurate elbow flexions.

Learning of a motor task, such as making accurate goal-directed movements, is associated with a number of changes in limb kinematics and in the EMG activity that produces the movement. Some of these changes include increases in movement velocity, improvements in end-point accuracy, and the development of a biphasic/triphasic EMG pattern for fast movements. One question that has remained unanswered is whether the time course of the learning-related changes in movement parameters is similar for all parameters. The present paper focuses on this question and presents evidence that different parameters evolve with a specific temporal order. Neurologically normal subjects were trained to make horizontal, planar movements of the elbow that were both fast and accurate. The performance of the subjects was monitored over the course of 400 movements made during experiments lasting approximately 1.5 h. We measured time-related parameters (duration of acceleration, duration of deceleration, and movement duration) and amplitude-related parameters (peak acceleration, peak deceleration, peak velocity), as well as movement distance. In addition, each subject's reaction time and EMG activity was monitored. We found that reaction time was the parameter that changed the fastest and that reached a steady baseline earliest. Time-related parameters decreased at a somewhat slower rate and plateaued next. Amplitude-related parameters were slowest in reaching steady-state values. In subjects making the fastest movements, a triphasic EMG patterns was observed to develop. Our findings reveal that movement parameters change with different time courses during the process of motor learning. The results are discussed in terms of the neural substrates that may be responsible for the differences in this aspect of motor learning and skill acquisition.

Expression, purification, crystallization and preliminary x-ray analysis of the kappa-carrageenase from Pseudoalteromonas carrageenovora.

A recombinant form of His-tagged kappa-carrageenase from Pseudoalteromonas carrageenovora has been expressed, purified and crystallized. Crystals have been obtained by the vapour-diffusion method using polyethylene glycol (Mr = 4000) as a precipitant. These crystals belong to the space group P212121, with unit-cell parameters a = 58.2, b = 62.8, c = 77.9 A, and diffract to 2.2 A resolution on a rotating-anode X-ray source.

Functional magnetic resonance imaging of motor, sensory, and posterior parietal cortical areas during performance of sequential typing movements.

We investigated the activation of sensory and motor areas involved in the production of typing movements using functional magnetic resonance imaging (fMRI). Eleven experienced typists performed tasks, in which the spatial and temporal requirements as well as the number of digits involved were varied. These included a simple uni-digit repetitive task, a uni-digit sequential task, a dual-digit sequential task, a multi-digit sequential task, and typing text from memory. We found that the production of simple repetitive keypresses with the index finger primarily involved the activation of contralateral primary motor cortex (M1), although a small activation of the supplementary motor area (SMA) and other regions was sometimes observed as well. The sequencing of keypresses involved bilateral M1 and a stronger activation of the SMA and to a lesser extent the premotor area, cingulate gyrus, caudate, and lentiform nuclei. However, the activation of these areas did not exclusively depend on the complexity of the movements, since they were often activated during more simple movements, such as alternating two keypresses repeatedly. Somatosensory and parietal regions were also found to be activated during typing sequences. The activation of parietal areas did not exclusively depend on the spatial requirements of the task, since similar activation was observed during movements within intra-personal space (finger-thumb opposition) and may instead be related to the temporal requirements of the task. Our findings suggest that the assembly of well-learned, goal-directed finger movement sequences involves the SMA and other secondary motor areas as well as somatosensory and parietal areas.

Relationship of cerebellar Purkinje cell simple spike discharge to movement kinematics in the monkey.

The simple spike discharge of 231 cerebellar Purkinje cells in ipsilateral lobules V and VI was recorded in three monkeys trained to perform a visually guided reaching task requiring movements of different directions and distances. The discharge of 179 cells was significantly modulated during movement to one or more targets. Mean simple spike rate was fitted to a cosine function for direction tuning, a simple linear function for distance modulation, and a multiple linear regression model that included terms for direction, distance, and target position. On the basis of the fit to the direction and distance models, there were more distance-related than direction-related Purkinje cells. The simple spike discharge of most direction-related cells modulated at only one target distance. The preferred directions for the simple spike tuning were not uniformly distributed across the workspace. The discharge of most distance-related cells modulated along only one movement direction. On the basis of the multiple linear regression model, simple spike discharge was also correlated with target position, in addition to direction and distance. Approximately half of the Purkinje cells had simple spike activity associated with only a single parameter, and only a small fraction of the cells with all three. The multiple regression model was extended to evaluate the correlations as a function of time. Considerable overlap occurred in the timing of the simple spike correlations with the parameters. The latency for correlation with movement direction occurred mainly in a 500-ms interval centered on movement onset. The correlations with target position also occurred around movement onset, in the range of -200-500 ms. Distance correlations were more variable, with onset latencies from -500 to 1,000 ms. These results demonstrate that the simple spike discharge of cerebellar Purkinje cells is correlated with movement direction, distance, and target position. Comparing these results to motor cortical discharge shows that the correlations with these parameters were weaker in Purkinje cell simple spike discharge, and that, for the majority of Purkinje cells, the simple spike discharge was significantly related to only a single movement parameter. Other differences between simple spike responses and those of motor cortical cells include the nonuniform distribution of preferred directions and the extensive overlap in the timing of the correlations. These differences suggest that Purkinje cells process, encode, and use kinematic information differently than motor cortical neurons.

Movement kinematics encoded in complex spike discharge of primate cerebellar Purkinje cells.

Monkeys performed a multijoint arm-reaching task that systematically varied movement direction and distance. Purkinje cell activity was recorded from 231 task-related cells, and the complex spike discharge was analyzed in relation to distance and direction. The complex spike activity of 123 Purkinje cells changed significantly relative to the background rate. Of these 123, the activity of 85 cells was related to distance and/or direction. The complex spike activity of 54 of these 85 cells fitted a cosine tuning curve for direction, generally at one distance. Using a simple linear regression model, the complex spike activity of 56 cells was significantly correlated with movement distance, usually in one direction. We conclude that the complex spike discharge of Purkinje cells is spatially tuned and strongly related to movement kinematics.

Response patterns and postspike effects of premotor neurons in cervical spinal cord of behaving monkeys.

Most of our information about spinal neurons has been derived from experiments with anesthetized or surgically. reduced preparations. To investigate these neurons under normal behavioral conditions, we recorded the activity of single afferent units in cervical dorsal root ganglia and of single interneurons in the cervical spinal cord of macaque monkeys, as they generated alternating flexion and extension torques about the wrist. Spike-triggered averages of rectified electromyographic activity were used to identify "premotor" (PreM) units associated with correlated postspike effects in active muscles. In addition to postspike effects, some spike-triggered averages showed early increases in average muscle activity, which were attributed to synchronous discharges in other PreM units. In recordings of peripheral afferents, 49% of the task-related dorsal root ganglia units produced postspike facilitation (PSF) of at least one forearm muscle, with a mean PSF latency of 5.8 +/- 0.3 ms (SE). The PSF amplitude was measured as the mean percent increase (MPI): the average increase of the PSF as a percentage of the prespike baseline mean. PreM afferent units produced PSF with an average MPI of 4.6 +/- 0.3%. In a study of cervical interneurons, about 13% (72/562) of the task-related cells showed postspike effects. These PreM interneurons had a mean PSF latency of 7.2 +/- 0.3 ms and a mean MPI of 4.6 +/- 0.2%. The MPI values for spinal neurons were similar to the MPIs reported for rubromotoneuronal and corticomotoneuronal cells. PreM neurons usually facilitated a subset of the coactivated muscles called the unit's "muscle field." The PreM afferents facilitated an average of 46% of the synergistically coactivated muscles, while PreM interneurons facilitated an average of 37%. These are comparable with the percentage of muscles facilitated by corticomotoneuronal (40%) and rubromotoneuronal (50%) cells. During the step-tracking task the monkeys generated ramp-and-hold torques about the wrist. The PreM afferents typically became active during either flexion or extension of the wrist, although a few were bidirectionally active. The most common response pattern in PreM afferents was a tonic discharge, followed by phasic and phasic-tonic discharge. The most common patterns exhibited by PreM interneurons were tonic and phasic-tonic responses. PreM afferent units began to discharge on average 51 +/- 13 ms before activation of their target muscle. This early onset supports our hypothesis that these PreM afferents arose from muscle spindles, which is also consistent with their short-latency PSF and their responses to perturbations that stretched their target muscles. The results reveal some salient differences between the discharge properties of dorsal root ganglia neurons, spinal interneurons, and supraspinal PreM cells in the motor cortex and red nucleus. All four PreM populations include tonic, phasic-tonic, and phasic cells, but in significantly different proportions. Most PreM afferents resembled corticomotoneuronal cells in being active only with their target muscles, unlike rubromotoneuronal cells and spinal PreM interneurons, which tended to exhibit more bidirectional discharges.

Functional magnetic resonance imaging of cerebellar activation during the learning of a visuomotor dissociation task.

We have used functional magnetic resonance imaging (fMRI) to study the changes in cerebellar activation that occur during the acquisition of motor skill in human subjects presented with a new task. The standard paradigm consisted of a center-out movement in which subjects used a joystick to superimposed a cursor onto viusual targets. Two variations of this paradigm were introduced: (1) a learning paradigm, where the relationship between movement of the joystick and cursor was reversed, requiring the learning of a visuomotor transformation to optimize performance and (2) a random paradigm, where the joystick/cursor relationship was changed randomly for each trial. Activation in the cerebellum was highest during the random paradigm and during the early stages of the learning paradigm. In the early stages of learning and during the random paradigm performance was poor with a decrease in the number of completed movements, and an increase in the time and length of movements. With repeated practice at the learning paradigm performance improbed and reached the same level of proficiency as in the standard task. Commensurate with the improbement in performance was a decrease in cerebellar activation, that is, activation in the cerebellum changed in a parallel, but inverse relationship with performance. Linear regression analysis demonstarated that the inverse correlation between cerebellar activation and motor performance was significant. Repeated practice at the random paradigm did not produce improvements in performance and cerebellar activity remained high. The data support the hypothesis that the cerebellum is strongly activated when motor performance is inaccurate, consistent with a role for the cerebellum in the detection of, and correction for visuomotor errors.

Temporal encoding of movement kinematics in the discharge of primate primary motor and premotor neurons.

1. Several neurophysiological studies of the primary motor and premotor cortices have shown that the movement parameters direction, distance, and target position are correlated with the discharge of single neurons. Here we investigate whether the correlations with these parameters occur simultaneously (i.e., parallel processing), or sequentially (i.e., serial processing). 2. The single-unit data used for the analyses presented in this paper are the same as those used in our earlier study of neuronal specification of movement parameters. We recorded the activity of single neurons in the primary motor and premotor cortices of two rhesus monkeys (Macaca mulatta) while the animals performed reaching movements made in a horizontal plane. Specifically, the animals moved from a centrally located start position to 1 of 48 targets (1 cm2) placed at eight different directions (0-360 degrees in 45 degrees intervals) and six distances (1.4-5.4 cm in 0.8-cm increments) from the start position. 3. We analyzed 130 task-related cells; of these, 127 (99 in primary motor cortex, 28 near the superior precentral sulcus) had average discharges that were significantly modulated with the movement and were related to movement direction, distance, or target position. To determine the temporal profile of the correlation of each cell's discharge with the three parameters, we performed a regression analysis of the neural discharge. We calculated partial R2s for each parameter and the total R2 for the model as a function of time. 4. The discharge of the majority of units (73.2%) was significantly correlated for some time with all three parameters. Other units were found that correlated with different combinations of pairs of parameters (21.3%), and a small number of units appeared to code for only one parameter (5.5%). There was no obvious difference in the presence of correlations between cells recorded in the primary motor versus premotor cortices. 5. On average we found a clear temporal segregation and ordering in the onset of the parameter-related partial R2 values: direction-related discharge occurred first (115 ms before movement onset), followed sequentially by target position (57 ms after movement onset) and movement distance (248 ms after movement onset). Some overlap in the timing of the correlation of these parameters was evident. We found a similar sequential ordering for the latency of the peak of the R2 curves (48, 254, and 515 ms after movement onset, respectively, for direction, target position, and distance).(ABSTRACT TRUNCATED AT 400 WORDS)

Spatial patterns of functional activation of the cerebellum investigated using high field (4 T) MRI.

Using single and multislice functional MRI at high field strength (4 T) we studied cerebellar activation in 12 subjects making a series of alternating wrist flexion and extension movements against constant inertial loads. Three spatial patterns of activation were observed: (i) parasagittal bands of activity localized primarily in the ipsilateral intermediate and lateral zones of the cerebellar hemispheres, (ii) medio-lateral bands which in some subjects followed the contour of individual folia and (iii) fragmented regions of activation covering extensive areas of the cerebellum. Bilateral activation of the cerebellum was observed in all subjects with measurable activity. Mean statistically significant activation intensity ranged from 2.34 to 13.54% above baseline.