Diagnostic strategy for diabetic polyneuropathy: Focus on nerve fiber type and magnetic resonance neurography.

Recently, various neurological tests for evaluating small-fiber neuropathy have been developed. Magnetic resonance neurography has also developed as a novel method to visualize diabetic neuropathy. The current status of diabetic polyneuropathy diagnosis focusing on the types of nerve fiber and magnetic resonance neurography is summarized.

[In vivo imaging of the corneal nerve plexus : From single image to large scale map]. / In-vivo-Bildgebung des kornealen Nervenplexus : Vom Einzelbild zur großflächigen Darstellung.

The sub-basal nerve plexus (SNP) of the cornea provides the possibility of in vivo and non-invasive examination of peripheral nerve structures by corneal confocal microscopy (CCM). Thus morphological alterations of the SNP can be directly detected and quantified. A single CCM image is insufficient for a well-founded diagnosis because of the inhomogeneous distribution of the nerve fibers; therefore, there is a demand for techniques for large area imaging of the SNP. This article provides an overview of published approaches to the problem. Current developmental work at the Karlsruhe Institute of Technology and the University of Rostock Eye Clinic is expected to lead to a simplified handling of the technology and a further improvement in the image quality.

Long-term follow-up of peptidergic and nonpeptidergic reinnervation of the epidermis following sciatic nerve reconstruction in rats.

OBJECT: Peripheral nerve injuries are a commonly encountered clinical problem and often result in long-term functional deficits. The current gold standard for transected nerves is an end-to-end reconstruction, which results in the intermittent appearance of neuropathic pain. METHODS: To improve our understanding of the relation between this type of reconstruction and neuropathic pain, the authors transected and immediately end-to-end reconstructed the sciatic nerve in rats. The effect of this procedure on neuropathic pain, as measured by thermal and mechanical hypersensitivity at 4 different time points (5, 10, 20, and 30 weeks), was related to the density of peptidergic and nonpeptidergic fiber innervation in the glabrous skin of rats' hind paws. RESULTS: Thermal hypersensitivity occurring 20 weeks after reconstruction was accompanied by a significant increase in peptidergic epidermal fibers. However, the lesion-induced reduction in the density of nonpeptidergic epidermal fibers remained decreased at all experimental time points. Moreover, temporal collateral sprouting by undamaged saphenous nerve was visualized using the recently revised Evans blue extravasation technique. Strikingly, as the sciatic nerve repopulated rats' hind paw, the saphenous nerve withdrew to its original territory. CONCLUSIONS: The authors conclude that the transient thermal hypersensitivity is related to increased density of epidermal peptidergic fibers, which mainly originate from regenerating fibers. Furthermore, a changed composition in the peptidergic and nonpeptidergic epidermal fibers is demonstrated following end-to-end reconstruction of the sciatic nerve.

Determinants of nerve conduction recovery after nerve injuries: Compression duration and nerve fiber types.

INTRODUCTION: The aims of this study were to determine the influences of: (1) timing of nerve decompression; and (2) nerve fiber types on the patterns of nerve conduction studies (NCS) after nerve injury. METHODS: Nerve conduction studies (NCS) were performed on 3 models of nerve injury: (1) crush injury due to transient nerve compression (crush group); (2) chronic constriction injury (CCI), or permanent compression (CCI group); and (3) CCI with removal of ligatures, or delayed nerve decompression (De-CCI group). RESULTS: There were distinct patterns of NCS recovery. The crush and De-CCI groups achieved similar motor nerve recovery, better than that of the CCI group. In contrast, recovery of sensory nerves was limited in the CCI and De-CCI groups and was lower than in the crush group. CONCLUSIONS: Immediate relief of compression resulted in the best recovery of motor and sensory nerve conduction. In contrast, delayed decompression restored only motor nerve conduction.

New insights on vertebrate olivo-cerebellar climbing fibers from computerized morphological reconstructions.

Characterization of neuronal connectivity is essential to understanding the architecture of the animal nervous system. Specific labeling and imaging techniques can visualize axons and dendrites of single nerve cells. Two-dimensional manual drawing has long been used to describe the morphology of labeled neuronal elements. However, quantitative morphometry, which is essential to understanding functional significance, cannot be readily extracted unless the detailed neuronal geometry is comprehensively reconstructed in three-dimensional space. We have recently applied an accurate and robust digital reconstruction system to cerebellar climbing fibers, which form highly dense and complex terminal arbors as one of the strongest presynaptic endings in the vertebrate nervous system. Resulting statistical analysis has shown how climbing fibers morphology is special in comparison to other axonal terminals. While thick primary branches may convey excitation quickly and faithfully to the far ends, thin tendril branches, which have a larger bouton density, form the majority of presynaptic outputs. This data set, now publicly available from NeuroMorpho.Org for further modeling and analysis, may constitute the first detailed and comprehensive digital reconstruction of the complete axonal terminal field with identified branch types and full accounting of boutons for any neuronal class in the vertebrate brain.

Digital morphometry of rat cerebellar climbing fibers reveals distinct branch and bouton types.

Cerebellar climbing fibers (CFs) provide powerful excitatory input to Purkinje cells (PCs), which represent the sole output of the cerebellar cortex. Recent discoveries suggest that CFs have information-rich signaling properties important for cerebellar function, beyond eliciting the well known all-or-none PC complex spike. CF morphology has not been quantitatively analyzed at the same level of detail as its biophysical properties. Because morphology can greatly influence function, including the capacity for information processing, it is important to understand CF branching structure in detail, as well as its variability across and within arbors. We have digitally reconstructed 68 rat CFs labeled using biotinylated dextran amine injected into the inferior olive and comprehensively quantified their morphology. CF structure was considerably diverse even within the same anatomical regions. Distinctly identifiable primary, tendril, and distal branches could be operationally differentiated by the relative size of the subtrees at their initial bifurcations. Additionally, primary branches were more directed toward the cortical surface and had fewer and less pronounced synaptic boutons, suggesting they prioritize efficient and reliable signal propagation. Tendril and distal branches were spatially segregated and bouton dense, indicating specialization in signal transmission. Furthermore, CFs systematically targeted molecular layer interneuron cell bodies, especially at terminal boutons, potentially instantiating feedforward inhibition on PCs. This study offers the most detailed and comprehensive characterization of CF morphology to date. The reconstruction files and metadata are publicly distributed at NeuroMorpho.org.

Projection of non-peptidergic afferents to mouse tooth pulp.

A large proportion of pulpal nociceptors are known to contain neuropeptides such as CGRP. However, the projection of non-peptidergic nociceptors to tooth pulp is controversial. Recently, the non- peptidergic subset of nociceptors has been implicated in mechanical pain in the skin. Since mechanical irritation of pulpal nociceptors is critical for evoking tooth pain under pathophysiological conditions, we investigated whether the non-peptidergic afferents project to tooth pulp as potential mechanotransducing afferents. For clear visualization of the non-peptidergic afferents, we took advantage of a recently generated knock-in mouse model in which an axonal tracer, farnesylated green fluorescence protein (GFP), is expressed from the locus of a sensory neuron-specific gene, Mrgprd. In the trigeminal ganglia (TG), we demonstrated that GFP is exclusively expressed in afferents binding to isolectin B4 (IB4), a neurochemical marker of non-peptidergic nociceptors, but is rarely co-localized with CGRP. Retrograde labeling of pulpal afferents demonstrated that a low proportion of pulpal afferents was co-localized with GFP. Immunohistochemical detection of the axonal tracer revealed that GFP-positive afferent terminals were densely projected into the tooth pulp. These results provide convincing evidence that non-peptidergic nociceptors are projected into the tooth pulp and suggest a potential role for these afferents in tooth pain.

Spinocerebellar projections from the cervical and lumbosacral enlargements in the chicken spinal cord.

In birds, spinocerebellar (SC) projections to the cerebellar cortex have not been understood well. We examined SC fiber terminal fields originating from the cervical and lumbosacral enlargements (CE and LSE, respectively) in the chicken. SC fiber terminals show parasagittal bands in the granular layer. Labeled terminals from the CE were distributed primarily in folia II-V and IX. Parasagittal bands of labeled terminals from the CE were not clearly separated in folia II and III but were clearly separated in folia IV and V. In folium IX, labeled terminals were diffusely distributed in all subfolia with no evidence of banding. The numbers of bands were 5 in folium II, 12 in folium III and 7 in folia IV and V at maximum. Labeled terminals from the LSE were distributed primarily in folia II-VI and IX. Labeled terminals from the LSE were arranged in 4 bands in folium II and in 8 bands in folium III at maximum. Parasagittal bands from the LSE in folia IV and V were not clearly separated. In folium VI, the numbers of parasagittal bands was 6 at maximum. In folium IX, labeled terminals were mainly found in subfolium IXc forming 6-8 parasagittal bands. There were more parasagittal bands of labeled terminals from the CE than from the LSE. The topography of SC fiber terminals from the CE was different from that of SC fiber terminals from the LSE.

Microanatomical and immunohistochemical study of the human lateral antebrachial cutaneous nerve of forearm at the antecubital fossa and its clinical implications.

Changes in the intraneural anatomy with age can cause poor prognosis of nerve repair in patients after nerve injury. The occurrence of Complex Regional Pain Syndrome-Type II, secondary to peripheral nerve injury, is common. The purpose of this study is to asses changes in cross-sectional anatomy of the lateral antebrachial cutaneous nerve of forearm (LCNF) at the antecubital fossa in the fascicular, nonfascicular components (adipose and nonadipose tissue), and sympathetic fibers area with respect to age. For the purpose of the study, 32 human (37-88 years) fresh cadaveric LCNF were collected from left-antecubital fossae and processed for histological, morphometric analysis [total cross-sectional (Asc), fascicular (Af), and nonfascicular area (Anonf)], and immunohistochemical method (tyrosine hydroxylase) for sympathetic fibers. The LCNF's average total cross-sectional area was 3.024 mm(2), and fascicular area was 0.582 mm(2). The average number of fascicles per mm(2) was 3.09. The cross-sectional area in the nerve was mainly occupied by nonfascicular connective tissue (80.75%). There was increased adipose tissue deposition (48.48% of Asc) and decreased collagen fibers (32.24% of Asc) in interfascicular domains without any definite relationship with age. The average sympathetic fiber area was 0.026 mm(2) within the nerve fascicular area without any correlation with age. In LCNF, there was more adipose tissue and less collagen fibers deposition in the interfascicular domains of all age cases, and this may act as an obstacle for nerve fiber regeneration on using LCNF as an interpositional nerve graft.

Afferent nerve fibers and acupuncture.

Acupuncture has been used for analgesia, for treating visceral function disorders and for improving motor functions. It is well established that stimulation of the skin and muscles, either electrically or with noxious or non-noxious stimuli, induces a variety of somato-motor and autonomic responses. This strongly suggests that acupuncture acts by exciting cutaneous and/or muscular afferent nerve fibers. A question of considerable scientific and practical interest is what kinds of somatic afferent fibers are stimulated by acupuncture and are involved in its effects. There are several types of afferent fiber: thick myelinated Aα and Aß (group I and II), thin myelinated Aδ (group III) and thinner unmyelinated C (group IV) fibers. In recent studies we have tried to establish which ones of these types of somatic afferent fiber are stimulated by acupuncture. In this article we first review the experimental evidence showing that the effects of acupuncture are mediated by the activation of afferent nerve fibers innervating the skin and muscles. Secondly, we discuss what types of afferent nerve fiber are activated by electrical acupuncture, and what types are involved in its effects on somato-motor functions and on visceral functions. Finally, we present some new findings based on recordings from single afferent nerve fibers excited by manual acupuncture.

Vagal afferent nerves with the properties of nociceptors.

Vagal afferent nerves are essential for optimal neural regulation of visceral organs, but are not often considered important for their defense. However, there are well-defined subsets of vagal afferent nerves that have activation properties indicative of specialization to detect potentially harmful stimuli (nociceptors). This is clearly exemplified by the vagal bronchopulmonary C-fibers that are quiescent in healthy lungs but are readily activated by noxious chemicals and inflammatory molecules. Vagal afferent nerves with similar activation properties have been also identified in the esophagus and probably exist in other visceral tissues. In addition, these putative vagal nociceptors often initiate defensive reflexes, can be sensitized, and have the capacity to induce central sensitization. This set of properties is a characteristic of nociceptors in somatic tissues.

The classification and identification of human somatic and parasympathetic nerve fibres including urinary bladder afferents and efferents is preserved following spinal cord injury.

UNLABELLED: Single-fibre extracellular action potentials were recorded with 2 pairs of wire electrodes from lower human sacral nerve roots during surgery. The roots from which was recorded from were used for morphometry. Nerve fibre groups were identified by conduction velocity distribution histograms of single afferent and efferent fibres and partly by nerve fibre diameter distribution histograms. The values of group conduction velocity and group nerve fibre diameter measured in the paraplegics were very similar to those obtained from brain-dead humans and patients with no spinal cord injury. Thus the classification and identification of nerve fibre groups remained preserved following spinal cord injury. Upon retrograde bladder filling the urinary bladder stretch and tension receptor afferent activities were increased; on two occasions they even fired when the bladder was empty. Two reasons are brought forward for a too small storage volume of the urinary bladder in paraplegics: too high afferent activity of the bladder due to changed receptor field transduction mechanisms and too low compliance. SUMMARY: 1. Single nerve fibre action potentials (APs) of lower sacral nerve roots were recorded extracellularly with 2 pairs of wire electrodes during an operation for implanting an anterior root stimulator for bladder control in 9 humans with a spinal cord injury and a dyssynergia of the urinary bladder. Roots that were not saved and that were used to record from were later used for morphometry. 2. Nerve fibre groups were identified by conduction velocity distribution histograms of single afferent and efferent fibres and partly by nerve fibre diameter distribution histograms, and correlation analysis was performed. Group conduction velocity values were obtained additionally from compound action potentials (CAPs) evoked by electrical stimulation of nerve roots and the urinary bladder. 3. The group conduction velocities and group nerve fibre diameters had the following pair-values at 35.5 degrees C: Spindle afferents: SP1 (65 m/s / 13.1 microm), SP2 (51/12.1); touch afferents: T1 (47/11.1), T2 (39/10.1), T3 (27/9.1), T4 (19/8.1); urinary bladder afferents: S1 (41 m/s / -), ST (35/-); alpha-motoneurons: alpha 13 (-/14.4), alpha 12 (65 m/s /13.1 microm), alpha 11 (60?/12.1)[FF], alpha 2 (51/10.3)[FR], alpha 3 (41/8.2)[S]; gamma-motoneurons: gamma(beta) (27/7.1), gamma 1 (21/6.6), gamma 21 (16/5.8), gamma 22 (14/5.1); preganglionic parasympathetic motoneurons: (10 m/s / 3.7 microm). 4. The values of group conduction velocity and group nerve fibre diameter measured in the paraplegics were very similar to those obtained earlier from brain-dead humans and patients with no spinal cord injury. Also, the axon number and the axon density of myelinated fibres of lower sacral nerve roots remain unchanged following spinal cord injury. Thus the classification and identification of nerve fibre groups remained preservedfollowing spinal cord injury. A direct comparison can thus be made of natural impulse patterns of afferent and efferent nerve fibres between paraplegics (pathologic) and brain-dead humans (supraspinal destroyed CNS, in many respects physiologic). 5. When changing the root temperature from 32 degrees C to 35.5 degrees C, the group conduction velocities changed in the following way in one case: SP2: 40 m/s (32 degrees C) to 50 m/s (35.5%), S1: 31.3 to 40, ST: 25 to 33.8, M: 12.5 to 13.8; alpha 2: 40 to 50, alpha 3: 33 to 40. The group conduction velocities showed different temperature dependence apart from SP2 fibres and alpha 2-motoneurons. 6. Upon retrograde bladder filling the urinary bladder stretch (S1) and tension receptor afferent (ST) activity levels were undulating and increased. As compared to activity levels detected in a brain-dead human, S1 (designates afferents, not cord segment) and ST afferents fired even when the bladder was empty, with an activity level similar to those observed in a brain-dead human with the bladder half filled. Two reasons are brought forward for an too small storage volume of the urinary bladder in paraplegics: too high afferent activity of the bladder due to changed receptor field signal transduction mechanisms and too low compliance. 7. With the newly developed 'coordination dynamics therapy', applied early after spinal cord injury, such complications of bladder functioning can be avoided; the bladder can causally be cured in severe spinal cord injury.

The sweet taste quality is linked to a cluster of taste fibers in primates: lactisole diminishes preference and responses to sweet in S fibers (sweet best) chorda tympani fibers of M. fascicularis monkey.

BACKGROUND: Psychophysically, sweet and bitter have long been considered separate taste qualities, evident already to the newborn human. The identification of different receptors for sweet and bitter located on separate cells of the taste buds substantiated this separation. However, this finding leads to the next question: is bitter and sweet also kept separated in the next link from the taste buds, the fibers of the taste nerves? Previous studies in non-human primates, P. troglodytes, C. aethiops, M. mulatta, M. fascicularis and C. jacchus, suggest that the sweet and bitter taste qualities are linked to specific groups of fibers called S and Q fibers. In this study we apply a new sweet taste modifier, lactisole, commercially available as a suppressor of the sweetness of sugars on the human tongue, to test our hypothesis that sweet taste is conveyed in S fibers. RESULTS: We first ascertained that lactisole exerted similar suppression of sweetness in M. fascicularis, as reported in humans, by recording their preference of sweeteners and non- sweeteners with and without lactisole in two-bottle tests. The addition of lactisole significantly diminished the preference for all sweeteners but had no effect on the intake of non-sweet compounds or the intake of water. We then recorded the response to the same taste stimuli in 40 single chorda tympani nerve fibers. Comparison between single fiber nerve responses to stimuli with and without lactisole showed that lactisole only suppressed the responses to sweeteners in S fibers. It had no effect on the responses to any other stimuli in all other taste fibers. CONCLUSION: In M. fascicularis, lactisole diminishes the attractiveness of compounds, which taste sweet to humans. This behavior is linked to activity of fibers in the S-cluster. Assuming that lactisole blocks the T1R3 monomer of the sweet taste receptor T1R2/R3, these results present further support for the hypothesis that S fibers convey taste from T1R2/R3 receptors, while the impulse activity in non-S fibers originates from other kinds of receptors. The absence of the effect of lactisole on the faint responses in some S fibers to other stimuli as well as the responses to sweet and non-sweet stimuli in non-S fibers suggest that these responses originate from other taste receptors.

Rich innervation of deep infiltrating endometriosis.

BACKGROUND: Deep infiltrating endometriosis (DIE) is a specific type of endometriosis, which can be associated with more severe pelvic pain than other forms of endometriotic lesions. However, the mechanisms by which pain is generated are not well understood. METHODS: DIE (n = 31) and peritoneal endometriotic (n = 40) lesions were sectioned and stained immunohistochemically with antibodies against protein gene product 9.5, neurofilament, nerve growth factor (NGF), NGF receptors tyrosine kinase receptor-A (Trk-A) and p75, substance P, calcitonin gene-related peptide, vesicular acetylcholine transporter, neuropeptide Y, vasoactive intestinal peptide and tyrosine hydroxylase to demonstrate myelinated, unmyelinated, sensory and autonomic nerve fibres. RESULTS: There were significantly more nerve fibres in DIE (67.6 +/- 65.1/mm(2)) than in peritoneal endometriotic lesions (16.3 +/- 10.0/mm(2)) (P < 0.01). DIE was innervated abundantly by sensory Adelta, sensory C, cholinergic and adrenergic nerve fibres; NGF, Trk-A and p75 were strongly expressed in endometriotic glands and stroma of DIE. CONCLUSIONS: The rich innervation of DIE may help to explain why patients with this type of lesion have severe pelvic pain.

Comparison of paclitaxel and cisplatin effects on the slowly adapting type I mechanoreceptor.

Cisplatin and paclitaxel are two of the most widely used chemotherapy drugs for the treatment of several forms of cancer. Both agents produce significant levels of peripheral neuropathy that can result in changes of treatment regimen. Although there have been recent efforts to understand the effects of these agents on nociceptor populations, little study has been made on their effects on large afferent populations. Here we report acute and chronic effects of paclitaxel and cisplatin administration on the type I mechanoreceptor using a skin-nerve preparation in rat and a standardized mechanical stimulus to compare mechanoreceptor response before and after treatment. In a control preparation, suppression of type I mechanoreceptor response during 2-min, arterial infusion of paclitaxel or cisplatin was significant for paclitaxel (28%, 1 microM; 33%, 10 microM; p<0.025), but not cisplatin (9%, 500 microM; 19%, 5 mM; p>0.05). Response returned to baseline within a 2-min washout period. Following pretreatment with paclitaxel or cisplatin, baseline response was significantly reduced from control animals. In addition, unlike the control preparation, a subsequent infusion of paclitaxel induced prolonged response suppression. Nerve fascicles innervating the preparation showed significant reduction in conduction velocity relative to control (cisplatin pretreatment: Abeta, 22%, p<0.01; C-fiber, 33%, p<0.01. paclitaxel pretreatment: Abeta, 17%, p<0.05; C-fiber, 23%, p<0.05). It was concluded that chronic paclitaxel or cisplatin treatment not only significantly alters the type I mechanotransduction process, but also increases susceptibility of the type I ending to further paclitaxel exposure.

A brief historical note on the classification of nerve fibers.

This is a brief review of the literature focused on the articles that formed the basis for the classification of the nerve fibers. Mention is also made to the origin of the nomenclature of the different motoneurons (alpha, beta and gamma).

Quantitative analysis of the distribution of the motor cortex representations of the fore-and hindlimbs in the red nucleus of the cat.

A quantitative analysis of the distribution of corticorubral fibers was performed after precise electrolytic lesioning of the lateral and medial margins of the posterior sigmoid gyrus--the motor representations of the fore-and hindlimbs respectively--in cats. The cortical representations of the forelimbs were found to project to the whole of the rostrocaudal extent of the red nucleus (RN). The number of efferent fibers terminating at the rostral margin of the RN was almost twice that terminating in the caudal third of the RN. Efferent fibers of the cortical representation of the hindlimbs did not project to the rostral two thirds of the RN but ended in its caudal third; the number of projecting corticorubral fibers was the same as the number running from the cortical representation of the forepaws to the caudal third of the RN. The significantly (almost double) greater number of fibers running from the cortical representation of the forelimbs in comparison with the number directed from the representation of the hindlimbs found in the present study is probably evidence of the greater functional importance of corticorubral connections in movement reactions performed by the forelimbs.

A brief historical note on the classification of nerve fibers

This is a brief review of the literature focused on the articles that formed the basis for the classification of the nerve fibers. Mention is also made to the origin of the nomenclature of the different motoneurons (a, b and g).

Os autores fazem uma breve revisão da literatura com foco nos artigos que deram origem à classificação das fibras nervosas. É também mencionada no texto a origem da nomenclatura dos diferentes neurônios motores (a, b and g).

Morphometry of saphenous nerve in young rats.

The rat saphenous nerve contains only somato-sensory fibers and is used in investigations of neuropathic pain and its treatment. Due to its superficial anatomical path, the saphenous nerve is also widely used in electrophysiological studies. Nevertheless, morphologic and morphometric descriptions of the normal saphenous nerve are scanty in the literature and information on useful morphometric parameters of this nerve is still missing. Thus, the present study aimed to investigate the longitudinal and lateral symmetry of the saphenous nerve in young rats. Proximal and distal segments of the left and right saphenous nerves from female Wistar rats, aged 30 days (N=5) were morphometrically evaluated and comparisons were made between sides and segments. Our results show that the saphenous nerve is longitudinally and laterally symmetric since there were no morphometric differences between proximal and distal segments, as well as between right and left sides. This lateral symmetry is important in order to validate those experiments in which the contralateral nerve is used as the control. Also, the longitudinal symmetry information is fundamental to further studies involving the "dying back" neuropathy models. The present study adds to the literature new morphometric information on the rat saphenous nerve that might be useful for a better interpretation of further studies involving this nerve and experimental models of nerve diseases.

Intraburst and interburst signaling by climbing fibers.

Although cerebellar Purkinje cell complex spikes occur at low frequency (approximately 1/s), each complex spike is often associated with a high-frequency burst (approximately 500/s) of climbing fiber spikes. We examined the possibility that signals are present within the climbing fiber bursts. By intracellularly recording from depolarized, nonspiking Purkinje cells in anesthetized pigmented rabbits, climbing fiber burst patterns were investigated by determining the number of components in the induced compound EPSPs during spontaneous activity and during visual stimulation. For our sample of 43 cells, >70% of all EPSPs were of the compound type composed of two or three EPSPs. During spontaneous activity, the number of components in each compound EPSP was not related to the latency to the succeeding compound EPSP. Conversely, the number of components in each compound EPSP was related to its latency after the preceding compound EPSP. This latency increased from 0.62 s for one-component EPSPs to 1.69 s for compound EPSPs with four or more components. The effect of visual stimulation on the climbing fiber activity was studied in 19 floccular Purkinje cells whose low-frequency interburst climbing fiber response was modulated by movement about the vertical axis. During sinusoidal oscillation (0.1 Hz, +/-10 degrees), compound EPSPs with a larger number of components tended to be more prevalent during movement in the excitatory direction than in the inhibitory direction. Thus, climbing fibers can, in addition to modulation of their low interburst frequency, transmit signals in the form of the number of spikes within each high-frequency burst.