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Biomedical subjects

H Suárez

Publications and source records attributed to H Suárez.

At least 19 recordsLinked to original sources
PubMed2004

Long-term auditory adaptation to a modified peripheral frequency map.

OBJECTIVE: Cochlear implants (CIs) attempt to mimic the tonotopicity of the normal ear by stimulating more basal regions of the cochlea in response to higher frequencies. However, there may be a mismatch between the normal place-frequency map and that implemented by a CI. MATERIAL AND METHODS: Aiming to measure this potential mismatch and its changes over time, the present study used a method-of-adjustment procedure where CI users and normal-hearing listeners selected synthetic vowels to match prespecified vowel targets. Data from CI users were obtained longitudinally, starting on the day of initial stimulation and continuing for 2 years. RESULTS: CI users showed a significant amount of initial mismatch with respect to the normal-hearing listeners, but they also showed significant learning and adaptation over time and achieved nearly normal performance after some experience with the CI. CONCLUSION: In general, the adaptation process took several months, suggesting that some CI users may benefit from alternative signal processing or rehabilitation procedures designed to facilitate perceptual learning after cochlear implantation.

Acoustic Stimulation↗
PubMed2001

Assessment of the risk of fall, related to visual stimulation, in patients with central vestibular disorders.

In order to assess the influence of visual stimulation in the triggering of imbalance and falls in the elderly population, the postural responses of 18 elderly patients with central vestibular disorders and clinical evidence of instability and falls were studied while receiving different types of visual stimuli. The stimulation conditions were: (i) no specific stimuli; (ii) smooth pursuit with pure sinusoids of 0.2 Hz as foveal stimulation; and (iii) optokinetic stimulation (OK) as retinal stimuli. Using a platform AMTI Accusway platform, the 95% confidence ellipse (CE) and sway velocity (SV) were evaluated with a scalogram using wavelets in order to assess the relationship between time and frequency in postural control. Velocity histograms were also constructed in order to observe the distribution of velocity values during the recording. A non-homogeneous postural behavior after visual stimulation was found among this population. In five of the patients the OK stimulation generated: (i) significantly higher average values of CE ( > 3.4+/-0.69 cm2); (ii) a significant increase in the average values of the SV ( > 3.89+/-1.15 cm/s) and a velocity histogram with a homogeneous distribution between 0 and 18 cm/s; and (iii) a scalogram with sway frequencies of up to 4 Hz distributed in both the X and Y directions (backwards and forwards and lateral) during visual stimulation with arbitrary units of energy density > 5. These three qualitative and quantitative aspects could be "markers" of visual dependence in the triggering of the mechanism of lack of equilibrium and hence falls in some elderly patients and should be considered in order to prevent falls and also to assist in the rehabilitation program of these patients.

Accidental Falls↗
PubMed1999

Changes in the cerebral blood flow in postlingual cochlear implant users.

Five postlingually deaf patients (age range 28-58 years) with multichannel cochlear implants were examined with single photon emission tomography (SPECT) (triple-head rotating gamma camera). Changes in the regional cerebral blood flow (rCBF) after intravenous administration of technetium-99m ethyl cysteinate dimer (Tc-99m ECD) were assessed through a stimulation paradigm, consisting of: i) click stimuli (75 dB SPL) in the ear that was to be implanted, 2 weeks before surgery; ii) stimulation with the same click, one month after initial fitting; iii) stimulation with hearing sequential Spanish sentences one month after initial fitting. The results showed a significant increase in the rCBF in the primary left auditory area and in the right auditory cortex, in conditions ii) and iii). The rCBF also showed a significant asymmetrical increase in the frontal lobes when the patient was hearing sequential sentences (condition iii)) with asymmetrical distribution among patients. These results are discussed, principally the correlation between speech discrimination scores and the rCBF distribution in the frontal and temporal lobes.

Adult↗
PubMed1997

Vibrotactile aid and brain cortical activity.

Six profoundly deaf patients were studied with mapping evoked potentials (MEP) using an acoustic signal passed through the vibrotactile prosthesis. This stimulus produced an activation of the central sulcus brain cortex. When the proSthesis was placed in the presenternal area it showed N1 P1 potentials with higher voltage and a more defined cortical dipole inversion than when the prosthesis was placed in the arm or abdomen: thus the presternal stimulation is considered an adequate place for the use of vibrotactile stimulation. The MEP were recorded in 2 patients after a period of audiological training and they showed new earlier potentials. These suggest plastic changes in the processing of an acoustic signal sent from the presternal skin by the somatosensory pathway after training and involving learning procedures.

Adolescent↗
PubMed1992

Prevalence of Entamoeba histolytica and other intestinal parasites in a community from Maracaibo, Venezuela.

The prevalences of Entamoeba histolytica and other intestinal parasites were assessed in a suburban community of Maracaibo, Venezuela, by examination of a stool specimen from each of 342 individuals, using iron-haematoxylin stained faecal smears and formalin-ether concentration. The overall parasitic infection rate was 80.4%, and 65.8% of the population had multiple infections. The overall amoebic infection rate, which was highest in female adults, averaged 39.7%. The E. histolytica infection rate was 8.7% and most of those infected were passing cysts. Entamoeba polecki was observed in two samples. Amongst the protozoa, Entamoeba coli was observed most frequently (24.8%) and Giardia lamblia was the predominant pathogen (13.0%). Trichuris trichiura (71.9%) and Ascaris lumbricoides (54%) were the most common parasites, particularly in school-children. The high rates of parasitic and multiple infections reflect the low socio-economic status of the community studied.

Adolescent↗
PubMed1992

Plastic properties of the vestibulo-ocular reflex in olivo-ponto-cerebellar atrophy.

Disorders in vestibulo-ocular functions were studied in 4 patients with olivo-ponto-cerebellar atrophy (OPCA). The phenomenon of habituation, considered as a plastic property of the vestibulo-ocular reflex (VOR), was explored with a behavioural paradigm in these patients. When subjected to the habituation paradigm all patients presented a modified response opposite to that observed in normal subjects. The role played by the cerebellum in relation to VOR plasticity--well known in different experimental models--is analyzed. The hypothesis of a modification of the cerebellum's inhibitory action on vestibular nuclei neurons is put forward to explain the inversion of the VOR habituation phenomenon in these patients.

Adult↗
PubMed1991

Serum ferritin deficiency in Huntington's disease patients.

This study was designed to investigate serum levels of iron, ferritin, vitamin B12 and folic acid in 18 Huntington's disease patients and 86 healthy control subjects. Serum iron, vitamin B12 and folic acid levels were normal. Ferritin concentrations were significantly diminished in the choreic patients. The importance of this finding in our attempt to understand the underlying biochemical defect and the chemical nature of the iron deposits found in several brain nuclei in Huntington's disease patients is unknown.

Adolescent↗
PubMed1989

Nutritional evaluation of Huntington disease patients.

A nutritional survey and evaluation was made in Huntington disease patients by the 24-h-recall method. Control subjects and choreic patients consumed a diet that supplied all the essential amino acids. The diet was hypocaloric, rich in animal protein, and low in fat and carbohydrates. The ratio of calcium to phosphorus in the groups studied was less than 1. High vitamin A and low vitamin C and niacin intakes were observed in Huntington disease patients. Only 17% of control subjects showed weight deficiency; 55% of the patients at stages III and IV of the disease were malnourished despite receiving the same food intake as controls. Although iron intake was deficient in all groups studied, it was enough to maintain normal serum levels of this metal. The deficiencies found in some nutrients do not explain the clinical manifestations observed in Huntington disease patients.

Adolescent↗