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Biomedical subjects

Luisa Lopez

Publications and source records attributed to Luisa Lopez.

9 recordsLinked to original sources
PubMed2006

Cognitive load affects postural control in children.

Inferring relations between cognitive processes and postural control is a relatively topical challenge in developmental neurology. This study investigated the effect of a concurrent cognitive task on postural control in a sample of 50 nine-year-old children. Each subject completed two balance trials of 60 s, one with a concurrent cognitive task (cognitive load) and another with no cognitive load. The concurrent cognitive task consisted of mentally counting backwards in steps of 2. Twelve posturographic parameters (PPs) were extracted from the centre of pressure (CoP) trajectory obtained through a load cell force plate. Analysis of variance revealed significant differences in the majority of the extracted PPs. CoP was found to travel faster, farther, and with substantially different features demonstrating an overall broadening of the spectrum in the frequency domain. Nonlinear stability factors revealed significant differences when exposed to a concurrent cognitive task, showing an increase of instability in the intervention rate of the postural control system. By grouping children through selected items from Teachers Ratings and PANESS assessment, specific significant differences were also found both in time and frequency domain PPs, thus confirming the hypothesis of an interaction between cognitive processes (and their development), and postural control.

Attention↗
PubMed2005

The development of postural strategies in children: a factorial design study.

BACKGROUND: The present study investigates balance control mechanisms, their variations with the absence of visual input, and their development in children from 7 to 11 years old, in order to provide insights on the development of balance control in the pediatric population. METHODS: Posturographic data were recorded during 60 s trials administered on a sample population of 148 primary school children while stepping and then quietly standing on a force plate in two different vision conditions: eyes closed and eyes open. The extraction of posturographic parameters on the quiet standing phase of the experiment was preceded by the implementation of an algorithm to identify the settling time after stepping on the force plate. The effect of different conditions on posturographic parameters was tested with a two-way ANOVA (Age x Vision), and the corresponding eyes-closed/eyes-open (Romberg) Ratios underwent a one-way ANOVA. RESULTS: Several posturographic measures were found to be sensitive to testing condition (eyes closed vs. eyes open) and some of them to age and anthropometric parameters. The latter relationship did not explain all the data variability with age. An evident modification of postural strategy was observed between 7 and 11 years old children. CONCLUSION: Simple measures extracted from posturographic signals resulted sensitive to vision and age: data acquired from force plate made it possible to confirm the hypothesis of the development of postural strategies in children as a more mature selection and re-weighting of proprioceptive inputs to postural control in absence of visual input.

Journal Article↗
PubMed2005

Brain damage in preterm infants: etiological pathways.

Preterm newborns represent a high-risk population for brain damage, primarily affecting the white matter, and for related neurodevelopmental disabilities. Determinants of brain damage have been extensively investigated, but there are still many controversies on how these factors can influence the developing brain and provoke damage. The concept of etiological pathway, instead of a single determinant, appears to better explain pathogenetic mechanisms: the brain damage may represent the final outcome of exposure to several combinations of risk factors in the same pathway or in different pathways and can change according to the gestational age. The aim of this article is to review the current knowledge on the pathogenesis of brain damage in preterm infants, within the frame of two main theoretical models, the ischemic and the inflammatory pathway. The relationship between the two pathways and the contribution of genetic susceptibility to ischemic and/or inflammatory insult, in modulating the extent and severity of brain damage, is also discussed.

Adult↗
PubMed2004

A chronic implant to record electroretinogram, visual evoked potentials and oscillatory potentials in awake, freely moving rats for pharmacological studies.

Electroretinogram (ERG), widely used to study the pharmacological effects of drugs in animal models (e.g., diabetic retinopathy), is usually recorded in anesthetized rats. We report here a novel simple method to obtain chronic implantation of electrodes for simultaneous recording at the retinal and cortical levels in freely moving, unanesthetized animals. We recorded cortical (VEPs) and retinal (ERGs) responses evoked by light (flash) stimuli in awake rats and compared the results in the same rats anesthetized with urethane (0.6 mg/kg) before and after the monocular administration of scopolamine methyl bromide (1 per thousand solution). We also compared the retinal responses with those derived from a classic acute corneal electrode. Anesthesia induced consistent changes of several VEP and ERG parameters like an increase of both latency and amplitude. In particular, the analysis of the variation of latency, amplitude, and spectral content of rapid oscillatory potentials could be important for a functional evaluation of the visual system in unanesthetized versus anesthetized animals.

Anesthetics↗
PubMed2003

Musicians versus nonmusicians. A neurophysiological approach.

The ability to perceive sounds and correctly categorize them within a scale is the result of the interaction between inherited capabilities and acquired rules. If a subject listens to a melody, occasional and unexpected endings of the melody typically evoke characteristic auditory evoked responses in the latency range of 300-400 ms (P300). Also, earlier stages of auditory information processing have been exhaustively investigated by means of mismatch negativity (MMN), a deflection that occurs in the auditory evoked response at a latency of about 200 ms, whenever a deviance is randomly inserted in a series of otherwise equal stimuli. Conceivably, perceptual deviations could also be detected against expectancies that are based on abstract rules; introspective experience suggests that such deviations may also elicit fast intuitive responses that typically initiate processes of analytical reasoning for confirmation. In music, the physical features of the stimulus are, in fact, always changing, because the melodic contour consists of a series of notes with different pitch characteristics. In such a condition, a typical mismatch negativity would not be evoked on the basis of physical deviance, but rather of criteria involving the musical contour of the stimulus. In this study, 20 healthy subjects (10 nonmusicians and 10 musicians) underwent auditory stimulation (tone, chord, chord sequence, Mozart and Bach melodies) and both electrical and magnetic recordings. Clear N1 was recorded for all paradigms, in all subjects; MMN and P300 were also recorded, and their amplitudes and latencies were significantly correlated with the musicality score and with the paradigm's difficulty.

Acoustic Stimulation↗
PubMed2002

Modulation of flash stimulation intensity and frequency: effects on visual evoked potentials and oscillatory potentials recorded in awake, freely moving mice.

Visual evoked potentials (VEP) responses to flash stimulation at nine intensities, from 0.611 to 945.6 cd/m(2)*s, and two frequencies (0.2 and 1 Hz) were recorded and oscillatory potentials (OPs) extracted after digital 50-Hz high pass filtering in unanaesthetized unrestrained mice. Both VEP and OPs morphology were replicable for all conditions and were similar to values reported in the literature. In particular OPs spectral analysis showed that the main frequency component remained stable at 66-77 Hz, for both stimulation frequencies, although it displayed an increase in amplitude, as a function of stimulus intensity. OPs amplitude at 1 Hz versus 0.2 Hz stimulus frequency was higher after taking into account the different noise contributions in the two conditions. Root mean square values calculated at selected time windows, revealed that, at 1 Hz, the main contribution to OPs occurs at the onset of the response (14-27 ms) while, at 0.2 Hz, the higher RMS was recorded later (42-56 ms). This difference accounts for the longer duration of the oscillatory event in the 0.2-Hz condition and suggests that oscillatory activity, modulated and carried along the visual pathway, is recorded at the cortical electrode after further elaboration at the cortical/subcortical level, depending on stimulus properties.

Animals↗
PubMed2002

Naloxone prevents cell-mediated immune alterations in adult mice following repeated mild stress in the neonatal period.

1. Mild stress plus mild pain (solvent injection) applied daily to neonatal mice induces hormonal, behavioural and metabolic changes perduring in the adult life. 2. We investigated whether daily mild stress to neonatal mice induces also long-term defined changes of immune response, and whether immune changes are prevented through repeated administration of the opioid antagonist naloxone. 3. Mild stress plus solvent injection administered from birth to the 21st postnatal day causes not only behavioural and metabolic changes, but also long-term (up to 110 days of life) splenocytes modifications, consisting in: increased release of the Th-1 type cytokines interleukin-2 (IL-2) (from an average of 346 to 788 pg ml(-1)), interferon-gamma (from 1770 to 3942) and tumour necrosis factor-alpha (from 760 to 1241); decreased release of the Th-2 type cytokines IL-4 (from 49.1 to 28.4) and IL-10 (from 1508 to 877). Moreover, enhanced natural killer-cell activity; enhanced proliferative splenocytes properties in resting conditions and following phytohemoagglutinin and concanavalin-A stimulation are observed. Immunological, behavioural and metabolic changes are prevented by the opioid antagonist (-)naloxone (1 mg kg(-1) per day s.c., administered instead of solvent) but not by the biologically inactive enantiomorph (+)naloxone. 4. In conclusion, endogenous opioid systems sensitive to naloxone are involved in long-lasting enhancement of the Th-1 type cytokines and cell-mediated immunological response caused by repeated mild stress administered postnatally.

Animals↗
PubMed2002

A neurophysiological approach to effects induced by accelerated particles on the central nervous system in mice.

This experiment was designed to study mechanisms of "phosphene vision". A beam of accelerated carbon particles (energy 100 and 300 MeV/n) was delivered into retina and sensorimotor cortex of anaesthetised mice bearing chronic electrodes. Cycles of light flashes were also administered. Following accelerated particles stimulation cycles to the retina, 500 to 5000 per stimulus, 30 stimuli per cycle, stimulus time-related brain waveforms in mice cortex were recorded. Their amplitude and latency appeared to be related to the energy delivered. The short waveforms latency (approximately 30 ms), and the lack of retinic potentials and oscillatory potentials following particles stimuli suggest that the impact of accelerated particles does not produce activation of retinic chemical structures.

Animals↗