Vowel identification and pitch perceptions by cochlear implant users

Lai, T.T., Svirsky, M.A., Meyer, T.A., Kaiser, A.R., Basalo, S, Silveira, A., Suárez, H., Simmons, P.M. & Miyamoto, R.T. (1999). Eastern Society for Pediatric Research. Journal of Investigative Medicine, 47 (2) Feb. 1999. Atlantic City, NJ.

 

Abstract

Despite advances in implant technology, cochlear implant (CI) users demonstrate a wide range of the ability to perceive speech in the absence of visual cues. To explain speech perception with a CI, Svirsky & Meyer (1997) developed a psychophysically-based mathematical model [Multidimensional Phoneme Identification (MPI)]. The model provides a full description of how listeners encode, represent and combine the sensory information elicited by vowel sounds. The model generates predicted confusion matrices, given a listener’s performance on various psychophysical tasks. The model predicts, for any given listener, how well s/he perceives vowels, as well as which pairs of vowels are and are not confused by the listener. A three-dimensional model has successfully predicted vowel identification for a group of experienced CI users. In this study, we were interested in using the MPI model to predict long-term vowel perception for an individual CI user based on performance on a psychophysical (pitch ranking) task at the time of initial stimulation. Vowel perception improves with continued CI use. Is this improvement due to increases in the listener’s ability to discriminate between sounds or to label vowel sounds according to a learned pattern? We measured vowel identification and pitch ranking at the time of initial stimulation and several months later. Vowel identification was obtained using ten to fifteen repetitions of each Spanish vowel (I,E,A,O,U) presented in a /hVd/-like context. In the pitch ranking task, the subject heard stimuli sent to adjacent pairs of intra-cochlear electrodes and had to indicate which stimulus was higher pitched. A software version of the MPI model was implemented to obtain predicted vowel confusion matrices based on the patient’s pitch ranking capabilities. The subject’s ability to accurately rank the pitch of different intracochlear electrodes did not vary much between initial stimulation and 6 months of use. Vowel identification, however, increased from approximately chance performance (24%) at initial stimulation to 86% correct identification by 4 months of implant use. Based on the subject’s pitch ranking ability at initial stimulation, the model generated a reasonably accurate prediction of her vowel identification performance 4 months post-implant. The results suggest that the MPI model is an appropriate tool for predicting vowel perception in individual CI users, and that improvements in vowel identification are related to changes in vowel labeling rather than to changes in pitch ranking abilities.

Vitamin D status in relation to postural stability in the elderly

D. Boersma, O. Demontiero, Z. Mohtasham Amiri, S. Hassan, H. Suarez, D. Geisinger, P. Suriyaarachchi, A. Sharma and Gustavo Duque

THE JOURNAL OF NUTRITION, HEALTH & AGING

Abstract

Objectives

Postural instability (PI) is an important risk factor for falls, especially in the frail older population. In this study, we investigated the impact of vitamin D deficiency on PI in a sample of community dwelling older subjects. Our objective was to determine the potential association between vitamin D deficiency and PI in older fallers.

Design 

Cross-sectional study.

Setting 

Falls and Fractures Clinic, Department of Geriatric Medicine, Nepean Hospital, Penrith, Australia.

Participants 

One hundred and forty-five adults aged 65 years and older who have had at least one episode of a fall within the six months prior to assessment at the Falls and Fractures Clinic.

Measurements

Serum 25(OH) vitamin D3 [25(OH)D3] and parathyroid hormone concentrations were determined at baseline. Subjects were separated into 3 groups based on serum 25(OH)D3 levels with the following cut-off values: < 30 nmol/L (deficient), 30–50 nmol/L (insufficient) and > 50 nmol/L (normal). Other baseline measurements included body mass index, mini-nutritional assessment, grip strength, serum calcium concentration and creatinine clearance, which were used as covariables. PI was assessed using a computerized virtual reality system (Medicaa, Uruguay). Measured parameters included limits of stability (LOS) and centre of pressure (COP) under eyes closed on foam (ECF) and visio-vestibular stimulation. The estimated swaying area, computed from the ellipse of confidence under eyes closed standing on foam (ECF), was also used as a PI parameter. Gait velocity (GV) was measured using a GaitRITE walkway system.

Results 

Posture was impaired in vitamin D deficiency (<30 nmol/L) as indicated by lower LOS (90 +/- 18), higher ECF (25 +/- 10) and slower GV (55 +/- 7) as compared with the insufficient and normal groups. After adjustment for demographic, biochemical and anthropometric variables, vitamin D deficiency significantly correlated with low LOS and high COP under ECF.

Conclusion

Low levels of vitamin D were associated with PI. This association could also have an effect on slow GV and increased risk of falls. In conclusion, using an objective method to measure balance in older fallers we have identified a novel role of vitamin D in balance control. Prospective studies are required to confirm the effect of vitamin D on PI and elucidate the mechanisms of this association.

Visual gravitational vertical perception in peripheral vestibular hypofunction.

Suarez H, Geisinger D, Ferreira E, Suarez A, San Román C, Sotta G.

Acta Otolaryngol. 2011 Nov 10.

Abstract
Abstract Conclusions: Rise time in the estimation of the gravitational vertical in the head tilt response (HTR) test is increased in patients with peripheral vestibular lesions and residual chronic dizziness. Objective: Assessment of the perception of the gravitational vertical in patients with peripheral vestibular lesions through the HTR. Methods: HTR was studied in 12 patients with peripheral vestibular lesion, 8 clinically with chronic dizziness and 4 without it; 23 normal subjects were studied as control group. Two parameters of the HTR were assessed, rise time and steady-state error to characterize a dynamical system step response. The Kolmogorov-Smirnov test (alpha = 5%) was used to verify normal distribution (steady-state error, p = 0.53; rise time, p = 0.88). The three sigma ellipse was calculated for the control group. ROC curves were used to measure the sensitivity and specificity of these parameters. Results: Rise time showed increased values in peripheral vestibular lesion patients with chronic dizziness. Two-dimensional analysis (rise time vs steady-state error) allows a better discrimination between patients with peripheral vestibular hypofunction with chronic dizziness and the rest of the studied population.

Vibrotactile Aid and Brain Cortical Activity

Suárez H, Cibils D, Caffa. C, Silveira A, Basalo S, Svirsky M. Acta Otolaryngol.(Stock) 1997 117:208-210.

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 prothesis was placed in the presternal area it showed Nl PI 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.