Changes in Excitability of Ascending and Descending Inputs to Cerebellar Climbing Fibers during Locomotion (original) (raw)
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Gating of climbing fibre input to cerebellar cortical zones
Progress in brain research, 2000
AbstractÐThe inferior olive climbing ®bre projection and associated spino-olivocerebellar paths (SOCPs) have been studied intensively over the last quarter of a century yet precisely what information they signal to the cerebellar cortex during movements remains unclear. A dierent approach is to consider the times during a movement when aerent signals are likely to be conveyed via these paths.
Movement-related gating of climbing fibre input to cerebellar cortical zones
Progress in neurobiology, 1999
The inferior olive climbing fibre projection and associated spino-olivocerebellar paths (SOCPs) have been studied intensively over the last quarter of a century yet precisely what information they signal to the cerebellar cortex during movements remains unclear. A different approach is to consider the times during a movement when afferent signals are likely to be conveyed via these paths. Central regulation (gating) of afferent transmission during active movements is well documented in sensory pathways leading to the cerebral cortex and the present review examines the possibility that a similar phenomenon also occurs in SOCPs during movements such as locomotion and reaching. Several lines of evidence are considered which suggest that SOCPs are not always open for transmission. Instead, flow of sensory information to the cerebellum via climbing fibre paths is powerfully modulated during active movements. The findings are discussed in relation to the parasagittal zonal organization of...
A major route for peripheral information to gain access to the cerebellum is via ascending climbing fiber pathways. During active movements, gating of transmission in these pathways controls when climbing fiber signals can modify cerebellar activity. We investigated this phenomenon in rats during their exploratory behavior of rearing. During rearing up and down, transmission was reduced at a time when self-generated, behaviorally irrelevant (predictable) signals occur. However, during the upright phase of rearing, transmission was increased when behaviorally relevant (unpredictable) signals may occur. When the peripheral stimulation was delivered only during the upright phase, so its occurrence became predictable over time, transmission was reduced. Therefore, the results indicate that the gating is related to the level of predictability of a sensory signal.
Central regulation of cerebellar climbing fibre input during motor learning
The Journal of Physiology, 2002
A forelimb-withdrawal classical conditioning paradigm was used in awake cats (n = 4) to investigate changes in transmission in climbing fibre (CF) pathways during motor learning. The conditioned stimulus was an auditory tone, while the unconditioned stimulus was a low-intensity, single or double (0.1 ms) electrical pulse applied to the ipsilateral superficial radial nerve. Microwires chronically implanted into the paravermal cerebellar cortex (lobule V) were used to record the CF field potentials evoked by nerve stimulation, and fields at 22 recording sites (9 C1, 7 C2 and 6 C3 zone sites) were monitored during the complete sequence of at least one training run (i.e. over a period of about 2-3 weeks of conditioning). At 19 sites (86 %) conditioning led to a significant reduction in mean size of field. Similar reductions occurred at four sites studied over two successive training runs. At 10 sites (45 %) there was a statistically significant increase prior to the reduction. The three sites that failed to exhibit a significant reduction were all located in the C1 zone. Controls showed that the changes in CF transmission were dependent on the animal being conditioned. The mean size of CF field for trials in which a conditioned EMG response was present (in either the cleidobrachialis or biceps muscle) was not significantly different from the mean size for trials in which a conditioned response was absent. Similarly, on a trial-by-trial basis, CF pathway excitability was not correlated with the conditioned EMG activity in the flexor muscles under study. Overall, the results demonstrate that (1) the capacity of spino-olivocerebellar pathways (SOCPs) to forward information to the cerebellar cortex can be altered by recent experience, (2) establishment of a conditioned forelimb flexor reflex to a tone reduces SOCP excitability at most but not all sites within a forelimb-related region of the cerebellar cortex, (3) the extent of reductions differ at different sites and some are preceded by transient increases, and (4) the changes in transmission may not be related to the conditioned movement. The implications of these findings for some key theories of cerebellar cortical function are discussed.
Gating of cutaneous input to cerebellar climbing fibres during a reaching task in the cat
The Journal of Physiology, 1997
1. Task-dependent modulation of cutaneous input to climbing fibres projecting to the Cl, C2 and C3 zones in the cerebellar paravermal lobule V was investigated in awake cats during performance of a reaching task. 2. Climbing fibre responses resulting from low intensity (non-noxious) electrical stimulation of the ipsilateral superficial radial nerve were recorded as extracellular field potentials in the cerebellar cortex using chronically implanted microwires. 3. Response size, measured as the time-voltage integral of the evoked field potential, was assessed during three phases of the reaching movement, reaction, reach and grasp, and compared with the response size at rest. 4. At Cl and C3 zone recording sites response size was usually reduced during the task (7/10 sites). The reduction was most pronounced in the grasp phase, occasionally accompanied by a smaller reduction in the reach and reaction phases. In one case an enhancement was found in the reach phase. 5. Response size was also modulated during the task at four of six C2 zone recording sites.
The Journal of physiology, 1990
1. Cutaneous nerve stimulation was used to study the excitability of the spino-olivocerebellar pathways (SOCPs) to the c2 zone of the paravermal cerebellar cortex in the cat. Non-noxious single-shock stimulation of the right and left superficial radial (SR) nerves via implanted cuff electrodes was used to evoke field potentials in the cerebellar cortex via the SOCPs. 2. The evoked potentials were recorded extracellularly either in lobule V of the anterior lobe (three cats) or within the paramedian lobule of the posterior lobe (one cat) with glass-coated tungsten microelectrodes. Measurement of the amplitudes of the responses was used to monitor transmission in the SOCPs in cats at rest and during walking. 3. A total of eleven c2 recording sites were investigated in detail. At seven of these sites, responses were recorded both during locomotion and at rest. For all seven sites responses during locomotion were smaller, more variable in amplitude and less securely evoked (average reduc...
2006
The climbing fibre projection from the motor cortex to the cerebellar cortical C1 zone in the posterior lobe of the rat cerebellum was investigated using a combination of physiological, anatomical and neuropharmacological techniques. Electrical stimulation of the ipsilateral fore-or hindimbs or somatotopically corresponding parts of the contralateral motor cortex evoked climbing fibre field potentials at the same cerebellar recording sites. Forelimb-related responses were located in the C1 zone in the paramedian lobule or lobulus simplex and hindlimb-related responses were located in the C1 zone in the copula pyramidis. Microinjections of anterograde axonal tracer (Fluoro-Ruby or Fluoro-Emerald) were made into the fore-or hindlimb parts of the motor cortex where stimulation evoked the largest cerebellar responses. After a survival period of 7-10 days, the neuraxis was examined for anterograde labelling. No terminal labelling was ever found in the inferior olive, but labelled terminals were consistently found in a well-localized site in the dorso-medial medulla, ventral to the gracile nucleus, termed the matrix region. Pharmacological inactivation of the matrix region (2 mm caudal to the obex) selectively reduced transmission in descending (cerebro-olivocerebellar) but not ascending (spino-olivocerebellar) paths targeting fore-or hindlimb-receiving parts of the C1 zone. Transmission in spino-olivocerebellar paths was either unaffected, or in some cases increased. The identification of a novel pre-olivary relay in cerebro-olivocerebellar paths originating from fore-and hindlimb motor cortex has implications for the regulation of transmission in climbing fibre pathways during voluntary movements and motor learning.
Climbing fiber responses of cerebellar Purkinje cells to passive movement of the cat forepaw
Brain Research, 1976
The activity of cerebellar Purkinje cells during controlled and passive movement of the forepaw was studied in the cat. Burst responses characteristic of activation by climbing fibers were observed in Purkinje cells in lobules Vb and Vc of the cerebellar vermis and paravermis. The climbing fiber responses followed the onset of a movement with a latency ranging from 20 to 60 msec depending upon movement type and amplitude. Responsive Purkinje cells were localized in a well defined parasagittal strip very near the paravermal vein in lobules Vb and Vc. Cells within the responsive strip responded with identical response probabilities and latencies for any particular type of movement presentation. Responses were independent of starting paw position and direction of movement. Climbing fiber responses could be evoked by extremely small movements with most cells responding to displacements of 50/~m. The latencies and probabilities for climbing fiber responses were inversely related to movement amplitude with latencies as long as 80 msec for very small displacements.