Biomedical subjects

M S Valle

Publications and source records attributed to M S Valle.

10 recordsLinked to original sources

PubMed2006

Spatial anisotropy in the encoding of three-dimensional passive limb position by the spinocerebellum.

In an earlier study, we found that the encoding of limb position in the sagittal plane across the population of spinocerebellar Purkinje cells was anisotropic with a preferential gradient along horizontal direction. The aim of this study was to extend to a three-dimensional (3D) workspace the analysis of the relationships between Purkinje cells activity and rat's forelimb spatial position. In anesthetized animals, the extracellular activity of 121 neurons was recorded while a robot passively placed the limb in 18 positions within a cubic workspace (3x3x3 cm). In order to characterize the relationship between spatial locations and Purkinje cell activity we performed a backward stepwise regression starting from a model with three independent variables representing the antero-posterior, the medial-lateral and the vertical axes of workspace. Regression analysis showed that the firing of most cells was modulated exclusively along the antero-posterior (25%) or the medial-lateral (38%) axis, while a small portion was related only to the vertical axis (8%), indicating a generalized nonuniform sensitivity of Purkinje cells to limb displacement in 3D space.

Action Potentials↗

PubMed2001

Reticulocerebellar projections to the anterior and posterior lobes of the rat cerebellum.

By using retrograde double-labeling techniques, we analyzed the topography of projections from the lateral reticular nucleus (LRN) to the anterior and posterior lobes of the cerebellum, with the aim to investigate whether LRN projections to the two lobes come from different neurons or from branching axons of the same cells. We observed that about 4/5 of afferents the cerebellar cortex come from the ipsilateral LRN and about 1/5 from the contralateral nucleus. Furthermore, magnocellular division of LRN projects mainly to the anterior lobe, whereas parvicellular part primarily to the posterior lobe. The double-labelled cells were very numerous (about 1/3) and were located throughout the LRN, with the higher incidence in the magnocellular division and the lower in the subtrigeminal part.

Animals↗

PubMed2001

Analysis of ankle kinetics during walking in individuals with Down syndrome.

The biomechanical characteristics of the ankle during gait of 17 participants with Down syndrome, ages 8 to 36 years, were investigated. Ten volunteers without disabilities of comparable anthropometric parameters were the control group. A 3-dimensional gait analysis was performed using an optoelectronic system equipped with a force platform. Participants with Down syndrome showed significant decreases of plantar-flexor moments and of A1 and A2 joint powers. Furthermore, correlation between kinetic and temporal spatial parameters was markedly reduced or weak in comparison to the control group. These results point out a hypofunctioning of ankle, probably due to hypotonia and ligament laxity.

Adolescent↗

PubMed2000

Information processing in the spinocerebellar system.

The purpose of this study was to determine whether sensory information about limb kinematics relayed to the cerebellum over spinocerebellar pathways may be modified at the cerebellar level. We tested this by recording from dorsal spinocerebellar tract (DSCT) and Purkinje cells under the same experimental conditions in which the hindlimbs of anesthetized cats were passively moved through a series of step-like movement cycles. A population analysis of the response behavior showed that DSCT neurons encode a combination of limb axis position and movement velocity, whereas the Purkinje cells located in the DSCT cerebellar target areas encode limb axis velocity and position independently. We conclude from this that the cerebellum may somehow extract a velocity component from the afferent input signal.

Action Potentials↗

PubMed2000

Sensory representation of passive movement kinematics by rat's spinocerebellar Purkinje cells.

In this paper we examined Purkinje cells' sensory representations of kinematic parameters of passive movements imposed to the forelimb of anesthetized rats. Simple spike Purkinje cell activity was recorded while the rat's ipsilateral forearm was moved passively along circular footpaths at two different speeds. We found that the activity of 35.33% (165/467) of the neurons was significantly modulated during movement cycles. A multivariate regression analysis indicated that movement direction was the predominant factor in determining Purkinje cell activity, whereas movement velocity (i.e. the combination of movement direction and speed) was represented to a much lesser degree. Based on this result, we might suggest that a cortical efferent copy is necessary to the cerebellum in order to elaborate a movement velocity signal.

Action Potentials↗

PubMed2000

Distribution of spinocerebellar Purkinje cell responses to passive forelimb movements in the rat.

We recorded Purkinje cell activity throughout the spinocerebellum of anaesthetized rats while imposing circular passive movements to the unrestrained forelimb. The aim was to understand the type of processing of sensory information occurring at the level of the cerebellar cortex, on the basis that precerebellar sensory neurons have been shown to represent whole limb movement parameters better than single joint movements. We observed that neurons representing sensory aspects of arm movements were scattered throughout the spinocerebellar cortex without a distinct segregation from those that did not respond, albeit the relative density of responsive and unresponsive neurons was quite variable and depended on the area of the cortex. Furthermore, Purkinje cells that responded significantly to the arm movement cycles all showed the same response pattern consisting of a firing rate increase during the downward extension of the arm. These results are discussed as suggesting a coordinate framework for the representation of proprioceptive information in the cerebellum congruent to that observed for encoding motor parameters.

Animals↗

PubMed2000

C-Fos expression in the basilar pontine nuclei and reticulotegmental nucleus of the rat following lateral cerebellar nucleus stimulation.

The present study was carried out with the aim to observe whether, in the rat, the electric activation of the projection form the cerebellar lateral nucleus (LN) to the basilar pontine nuclei (BPN) and to the reticulotegmental nucleus (RtTg) is capable to induce the c-Fos expression. In particular, we compared the effects of a continuous LN stimulation at low-frequency (tonic stimulation) with those induced by high frequency pulse trains (phasic stimulation). The observed results show that the stimulation of LN induces c-Fos expression in a significant fraction of neurons in the contralateral BPN and RtTg. It was also observed that phasic stimulation was slightly more capable in producing c-Fos expression with respect to the tonic stimulation. Furthermore, systemic injection of MK-801, a non-competitive antagonist of the NMDA receptor, reduced the LN-induced c-Fos expression in BPN and RtTg. In contrast, GYKI 52466, an AMPA/kainate receptor antagonist, did not change the LN driven induction of c-Fos in both BPN and RtTg.

Animals↗

PubMed1999

On the relation of rat's external cuneate activity to global parameters of forelimb posture.

Using anesthetized adult rats, we studied the relationships between the activity of cells belonging to the external cuneate nucleus (ECN) and passive forelimb positions. In essence, we sought to distinguish between a representation of limb position based on local limb parameters (individual joint angles, for example) or a representation based on more global parameters such as the length and the orientation of the limb axis. Using multivariate regression analyses we found that most neurons showed strong linear relationships with the length and the orientation of the limb axis. Relationships to individual joint angles were, instead, rather weak and in most cases not significant. This result implies an extensive integration of sensory information at the level of second order sensory neurons.

Animals↗

PubMed1998

Spinocerebellar Purkinje cells and rat forelimb postures: a direction-dependent activity.

On anesthetized adult rats, we examined the possibility that the discharges of spinocerebellar Purkinje cells (PCs) are modulated by passive limb positioning. The rat forelimb was passively placed in four different sagittal positions while the simple spike spontaneous activity of single PCs was recorded; recordings started 5 s after the reaching of the posture and the forelimb remained at each position for at least 30 s. Although the activity of the PCs did not reflect the forelimb position, it showed hysteresis that depended in a cosine fashion on the direction of the preceding movement. This implies that the directional sensitivity of spinocerebellar PCs is persistent, since the activity levels were almost constant throughout the recording time.

Action Potentials↗

PubMed1993

Dental infections and coronary atherosclerosis.

An association between dental and other bacterial infections and coronary heart disease has recently been observed in both cross-sectional and longitudinal studies. To elucidate this topic, the severity of dental infections and coronary atheromatosis was assessed, together with measurements of the conventional coronary risk factors, in 100 individuals (88 men, 12 women, mean age 48, range 28-68 years) referred for diagnostic coronary angiography. Pantomography X-rays and coronary angiograms of the participants were scored blindly by single observers, a dentist and a radiologist respectively. The median pantomography score was 3.0 in male individuals belonging to the highest tertile of coronary atheromatosis score, as compared with 0.0 among the rest of the male participants (P = 0.003). The association between dental infections and severe coronary atheromatosis in males remained significant after adjusting for the effect of age, blood lipids, body mass index, hypertension, smoking and social class. No association between dental infections and coronary atheromatosis was observed in the small number of females studied. This observation supports the proposal that bacterial infections play a role in the pathogenesis of coronary atherosclerosis.

Adult↗