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Biomedical subjects

A M Small

Publications and source records attributed to A M Small.

At least 55 records · Page 3Linked to original sources
PubMed1979

Binaural critical masking bands.

Current understanding of the relation monaural estimates of the critical bandwidth for masking and those obtained in binaural listening situations is poor. The present study was designed to improve this situation by obtaining estimates of critical bandwich when the signal and masker were presented: (1) monaurally (NmSm), (2) binaurally with both signal and masker in phase at the ears (NoSo), (3) binaurally with masker in phase and signals 180 degrees out of phase (NoSpi). Threshold estimates were obtained in a two-interval forced-choice paradigm as a function of masker bandwidth for signal frequencies of 500 and 2000 Hz for the three conditions mentioned above. Maskers were computer-synthesized and had essentially infinite rejection slopes. For all conditions, as masker bandwidth was narrowed from wide band, threshold remained relatively constant until some critical bandwidth was reached. Further reductions in bandwidth were followed by progressive lowering of threshold, presumably due to removal of masker energy in the critical band. For both signal frequencies, the derived critical bandwidth estimates for the NmSm and NoSo conditions were similar and were smaller than the critical bandwidth estimates obtained in the NoSpi condition.

Adult↗
PubMed1979

Unmasking produced by combination tones.

This experiment investigated some interactions between combination tones (CT) and unmasking. Data were obtained from nine normal-hearing listeners in a forward-masking paradigm in which a 2000-Hz, 35-dB SPL masker preceded a 2000-Hz test signal. An adaptive, three-interval forced-choice procedure was employed to estimate the threshold for the test signal. This measurement provided a baseline. When a second sinusoid, the suppressor, of variable frequency and 55 dB SPL was presented concurrently with the masker, the amount of masking could be less than in the baseline condition. This two-tone unmasking was observed when the suppressor was approximately 2300 Hz. In the cubic difference tone (CDT) condition, two higher-frequency sinusoids of 80 dB SPL (with the lower frequency fixed at 2800 Hz) were added to the masker. In the difference tone (DT) condition, two higher-frequency sinusoids of 100 dB SPL (with the lower frequency fixed at 3500 Hz) were added to the masker. None of these sinusoids produced unmasking when presented individually, but when the CDT and DT were approximately 2300 Hz, unmasking was observed. The unmasking produced by the CTs was similar in its frequency characteristics to that of the single, suppressor tone. These results indicate that unmasking can be produced by CTs, just as if CTs were present in the stimulus. These data indirectly support the notion that CTs may be present in the form of traveling waves propagated along the basilar membrane.

Acoustic Stimulation↗
PubMed1978

A controlled crossover study of triiodothyronine in autistic children.

A placebo-controlled crossover study of behavioral effects of triiodothyronine (T3) was conducted in 30 young clinically euthyroid autistic children. Multiple independent raters and multiple rating scales were used. Except for a few symptoms that were reduced on T3, the drug did not differ from placebo. Time itself accounted for most of the improvement in the whole sample. As a group, the lower IQ children responded to T3. The individual children who were responders could not be defined by any parameter.

Autistic Disorder↗
PubMed1978

Minor physical anomalies in young psychotic children.

The authors examined three groups of children for minor physical anomalies: 52 autistic children, 34 nonautistic siblings of these patients, and 29 normal controls. The total number of anomalies and the weighted score were significantly higher in the autistic children. The formation of these anomalies in the first three months of fetal life may concur with the developmental deviation of the central nervous system in some of these individuals.

Abnormalities, Multiple↗
PubMed1976

Blood platelet monoamine oxidase activity in schizophrenic children and their families. A preliminary study.

In this study monoamine oxidase (MAO) activity was measured in blood platelets of 21 individuals (age 2 6/12-19 years) who were diagnosed at preschool age as schizophrenics; MAO activity was not significantly different from that found in normals. An insignificant correlation was found between MAO activity in patients and age; a similar correlation for normals was also insignificant. In a sample of 15 families, no significant correlation between MAO activity of patients and their parents was obtained.

Adolescent↗
PubMed1975

The measurement of critical masking bands.

The characteristics of the critical masking band, that spectral region of a wideband noise that is effective in masking a pure-tone signal, were inferred by measuring detectability (d) for tonal signals as a function of the cutoff frequency of a low-pass or high-pass noise masker. As the cutoff frequency of a low-pass noise was decreased from the wide-band (100-7000 Hz) condition toward the signal frequency, (500, 1000, or 4000 Hz) dectability maintained a constant minimum until a further reduction in cutoff frequency increased detectability, presumably due to a reduction in masker power within the critical band. As cutoff frequency was reduced further, detectability increased monotonically until detection reached 100%. This usually occurred when the cutoff frequency is 0.04 to 0.06 octaves below the signal frequency. The range of cutoff frequencies over which detectability changes occurred defines the critical masking band. These ranges correspond closely to well-known critical ratio data. The dependence of d on noise cutoff frequency did not differ at the two signal levels (15 and 25 dB SL) used in this experiment. The critical band appeared symmetrical about the signal frequency for most subjects and most experimental conditions, although some subjects displayed a marked asymmetry in the high frequency direction for some conditions.

Acoustic Stimulation↗
PubMed1975

Blood serotonin in schizophrenic children. A preliminary study.

Blood serotonin levels were measured in schizophrenic children, all of whom showed manifestations of illness in the first 2 years of life, and controls. Serotonin levels were higher in patients (mean = 0.267 mug/ml) than in controls (mean = 0.218 mug/ml), although the difference did not reach statistical significance. Serotonin levels were significantly higher in patients with florid psychosis and those with lower IQs than in patients in remission or partial remission or higher IQs.

Adolescent↗