Biomedical subjects

M C Perez-Abalo

Publications and source records attributed to M C Perez-Abalo.

6 recordsLinked to original sources

PubMed2001

Steady state responses to multiple amplitude-modulated tones: an optimized method to test frequency-specific thresholds in hearing-impaired children and normal-hearing subjects.

OBJECTIVE: To evaluate, using statistical methods, the usefulness of the binaural multiple frequency auditory steady state responses (MF SSRs) for objective, frequency-specific audiometry in a large sample of hearing-impaired children and normal-hearing subjects. DESIGN: The MF SSRs were recorded in a sample of 43 hearing-impaired children (86 ears) and 40 normal-hearing young adults (80 ears). Simultaneous carrier tones (0.5, 1, 2, and 4 kHz) modulated in amplitude at different rates (77 to 105 Hz) were presented binaurally (TDH 49 earphones) at variable intensities (110 to 20 dB SPL). For each subject the response thresholds (RTHs) at 0.5, 1, 2, and 4 kHz, were determined automatically (F test) and compared with the corresponding behavioral thresholds (BTHs). RESULTS: In the normal-hearing subjects, RTHs were detectable, on average, between 11 and 15 dB above the BTH. These differences were significantly smaller in the hearing-impaired (5 to 13 dB). Also a close correspondence was found between the subjective and objective audiogram curves in both groups. The within subject Spearman correlation coefficients calculated between the two curves, were in most cases above the significance cut off point (p < 0.05). Also in 1-way repeated measures analysis of variance, the overall error in the estimation of the audiogram (vector across frequency of absolute distances between the curves) did not differ significantly from zero. CONCLUSIONS: The binaural MF SSR was proven to be a valid technique for the estimation of an objective audiogram, in a large sample of hearing-impaired children and normal-hearing subjects. With this method, frequency-specific thresholds at 0.5, 1, 2, and 4 kHz could be determined in all subjects (and both ears) with no appreciable loss in accuracy and a considerable reduction in testing time (average recording time = 21 minutes) when compared with other frequency-specific techniques.

Acoustic Impedance Tests↗

PubMed1997

Comparison of statistical indicators for the automatic detection of 80 Hz auditory steady state responses.

OBJECTIVE: To evaluate, using receiver operation characteristic (ROC) curves, the performance of several statistical indicators in the objective detection of 80 Hz steady state auditory evoked responses. DESIGN: Steady state auditory evoked responses elicited by amplitude modulated tones of 500 and 1000 Hz, were obtained in 16 normal adults. Recordings were made at intensities ranging from 80 to 30 dB SPL and without stimulation. Four statistics: coherence synchrony measure, circular T2, a new variant of Hotelling T2 (labeled HT2) and a test for hidden periodicity (F test) were calculated. The statistics were compared using ROC curves and bootstrapping techniques. Two outcome measures were considered: behavioral threshold prediction and averaging efficiency. RESULTS: All indicators were highly accurate to detect a response (8 to 9 dB above mean behavioral threshold for the 1000 Hz and 14 to 16 dB for the 500 Hz carrier). Responses could be reliable detected after averaging about five individual epochs of long duration. No statistically significant differences were evidenced though in their capability to predict behavioral threshold or their averaging efficiency. CONCLUSIONS: Despite the more adequate statistical properties of some of these indicators no significant differences were found in their performance. Thus all of these indicators could be recommended for automatic detection of 80 Hz auditory steady state responses.

Adolescent↗

PubMed1996

Frequency-specific audiometry using steady-state responses.

OBJECTIVE: To evaluate the audiometric usefulness of steady-state responses to multiple simultaneous tones, amplitude-modulated at 75 to 110 Hz. DESIGN: Steady-state responses to multiple tones amplitude-modulated at different rates between 75 and 110 Hz and presented simultaneously were recorded at different intensities in normal adults, well babies, normal adults with simulated hearing loss, and adolescents with known hearing losses. Response thresholds were compared with behavioral thresholds. RESULTS: In normal adults the thresholds for steady-state responses to tones of 0.5, 1, 2, and 4 kHz were 14 +/- 11, 12 +/- 11, 11 +/- 8, and 13 +/- 11 dB, respectively, above behavioral thresholds for air-conducted stimuli, and 11 +/- 5, 14 +/- 8, 9 +/- 8, and 10 +/- 10 dB above behavioral thresholds for bone-conducted stimuli. In well babies tested in a quiet environment, the thresholds were 45 +/- 13, 29 +/- 10, 26 +/- 8, and 29 +/- 10 dB SPL. In adolescents with known hearing losses, the steady-state responses thresholds predict behavioral thresholds with correlation coefficients (r) of 0.72, 0.70, 0.76, and 0.91 at 0.5, 1, 2, and 4 kHz, respectively. CONCLUSION: Steady-state responses to tone amplitude-modulated at 75 to 110 Hz can be used for frequency-specific objective audiometry. The multiple-stimulus technique allows thresholds to be estimated for eight different stimuli at the same time.

Adolescent↗

PubMed1994

Brain potentials and the availability of semantic and phonological codes over time.

ERPs were recorded from subjects performing semantic and rhyme matching tasks using either spoken words, printed words or pictures as stimuli. Mismatches enhanced N400 (in the semantic task) and N450 (in the rhyme task). Onset and peak latencies were shorter for N450 than for N400 with spoken words; this relationship was inverted for pictures. Thus these latencies could index availability of semantic and phonological codes. For printed words, the latencies were shorter for N400 than N450, a result that supports direct-access modes of reading with late phonological code activation. The longer latencies found for N400 and N450 to pictures could suggest longer initial decoding for pictures with respect to words.

Adolescent↗

PubMed1987

Comparison of auditory-evoked potential detection methods using signal detection theory.

The performance of statistical evoked-potential detection methods was compared with that of human observers and among themselves by means of receiver operating characteristics (ROC) curves. The test material was a collection of brain stem auditory-evoked responses obtained from 98 infants with 60 and 30 dB nHL clicks. The observers and the statistical methods had to discriminate these responses from control recordings obtained without acoustic stimulation. Although the observers' criteria on different days varied considerably, the discrimination capacity was more stable. The discrimination capacity depended on the observers' experience. The statistical methods tested were the correlation coefficient (CCR), the standard deviation ratio (SDR) and a new method named T2R. The most efficient detection method was T2R. For false-alarm rates of 0.01 the statistical methods were more efficient than the human observers. Signal detection theory is useful for the evaluation of evoked-potential analysis methods.

Brain Stem↗

PubMedDate not supplied

[Early detection and intervention of hearing impairment in Cuba: outcome after 20 years].

INTRODUCTION: Infant hearing loss is a highly prevalent disorder which untreated can severely disrupt normal brain development. As a result there is a significant delay in language acquisition as well as many cognitive and emotional problems in the child. Over the last decades important advances have occurred in the available technology for early detection and assessment of hearing impairment. Therefore many countries worldwide have become aware of the need for hearing screening programs. The optimal protocols depending on the local conditions of health care as well as the availability of technological and human resources. AIM: To summarize the results obtained over the last 20 years by an ongoing hearing screening protocol. DEVELOPMENT: Data on the coverage program, sensitivity and specificity, age of identification of hearing losses, diagnostic and intervention stages will be summarized and discussed. Also the long terms effects of early detection on the child cognitive and language development are analyzed. Finally, the possible role of a new technique based on the recording of multiple auditory steady state potentials with Cuban equipment (AUDIX system) was evaluated within this context. CONCLUSIONS: The Cuban targeting multiple high risk hearing screening program is a useful alternative to early detection of hearing losses. The average detection age of hearing loss was 10 months during the period of optimal functioning. Cognitive, emotional and linguistic development are improved by early detection and intervention. The multiple auditory steady state responses can provide valuable audiometric information within a screening context.

Child↗