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Biomedical subjects

A M Small

Publications and source records attributed to A M Small.

At least 37 records · Page 2Linked to original sources
PubMed1987

Lateralization of dichotic noise bursts: effect of onset and offset disparity.

Sound image position associated with the interaural onset or offset disparity of a signal was quantified by a scaling procedure in three experiments. Lateralization cues derived from the steady-state portion of the broadband noise signal that would support a specific image position were minimized by the use of independent noise sources for each ear. Onset disparities produced lateralization toward the ear at which the sound was presented first, while offset disparity produced lateralization toward the ear at which the sound remained on longer. Disparity was systematically varied between 0 and 10 ms and for a given disparity, a greater shift in the sound image position was obtained when the disparity was at the onset rather than the offset. The duration of the shorter signal ranged from 2.5-100 ms and for either onset or offset disparity, the image of stimuli of long duration tended to remain near the center of the head, while those of shorter duration could be moved to more extreme positions. In an attempt to rule out dichotic loudness cues as a basis for the lateralization associated with offset disparity, stimuli were presented with equal energy at each ear. Image position for equal energy was virtually identical to that for equal sound pressure, suggesting that loudness differences are not mediating lateralization associated with offset disparity.

Adult↗
PubMed1984

Behavioral efficacy of haloperidol and lithium carbonate. A comparison in hospitalized aggressive children with conduct disorder.

The efficacy and safety of haloperidol, lithium carbonate, and placebo were critically assessed in 61 treatment-resistant, hospitalized children aged 5.2 to 12.9 years with diagnoses of conduct disorder, aggressive type. In this double-blind and well-controlled study, the optimal dosages of haloperidol ranged from 1.0 to 6.0 mg/day and those of lithium carbonate from 500 to 2,000 mg/day. For the assessment of behavioral changes and untoward effects, various rating scales were used in different settings. Both haloperidol and lithium carbonate were found to be significantly superior to placebo in decreasing behavioral symptoms. Although both medications were clinically effective, haloperidol was associated more often with untoward effects than was lithium carbonate.

Aggression↗
PubMed1984

Frequency effects in backward masking.

Frequency effects in auditory backward masking were examined by psychophysically determining the thresholds of 0.5-, 1-, 3-, 5-, and 7-kHz sinusoidal probes followed by a broadband noise masker. For each probe frequency, backward masking decreased approximately exponentially as the temporal interval between the probe and masker was increased. The rate of this exponential decay increased with increasing probe frequency. This latter result is consistent with Duifhuis' [J. Acoust. Soc. Am. 54, 1471-1488 (1973)] theory which attributes backward masking to the temporal overlap of cochlear responses to the probe and masker.

Adolescent↗
PubMed1984

The influence of temporal cues on the strength of periodicity pitches.

Three different waveforms were generated from the same component frequencies by setting the phase of the components so they were either homophasic (all component sinusoids start at 0 degree), diphasic (sinusoids alternate between -45 degrees and + 45 degrees), or heterophasic (starting phase randomly selected). Listeners were asked to rate the saliency of all periodicity pitches they could detect in stimuli which contained 12 or more components at frequencies above the region where pitches were perceived . A major finding was that the highest ratings of fundamental frequency (f1) pitch "strength" were always obtained for homophasic waveforms, which among the test stimuli have the most abrupt envelope fluctuations. In contrast, diphasic and heterophasic waveforms, which have smoother envelopes, yielded lower pitch strength estimates at f1 and higher ratings two octaves above the fundamental. These data indicate that information concerning the stimulus waveform envelope influences the relative prominence of competing pitches evoked by periodicity pitch stimuli. However, no one-to-one correspondence between pitch and waveform periodicity is apparent.

Acoustic Stimulation↗
PubMed1984

Haloperidol in the treatment of infantile autism: effects on learning and behavioral symptoms.

In this double-blind, placebo-controlled study the administration of haloperidol resulted in significant decreases in behavioral symptoms and in general clinical improvement in 40 autistic children ages 2.33 to 6.92 years. Haloperidol also produced greater facilitation and retention of discrimination learning in the laboratory. No adverse effects were observed at therapeutic doses, which ranged from 0.5 to 3.0 mg/day or 0.019 to 0.217 mg/kg per day.

Autistic Disorder↗
PubMed1983

Tonal masking and frequency selectivity for the monaural and binaural hearing systems.

A series of masking experiments was performed with the aim of comparing frequency selectivity for the monaural and binaural systems. The masking stimulus used in this study combined a sinusoid, which was gated simultaneously with the signal, with a continuous broadband noise. Signal frequency was fixed at 500 Hz. In one condition, the tonal masker and noise were interaurally in phase and the signal was phase reversed. In a second condition, noise, tonal masker, and signal were presented to one ear alone. Signal thresholds were obtained as a function of masker frequency for these two conditions. After making an appropriate selection of noise levels, masking functions for the monaural and binaural system conditions were found to agree closely except for a region about their tips where the binaural condition was more detectable. Two possible interpretations of these results are discussed. Either the monaural and binaural systems contain filters each which have similarly shaped skirts, or the frequency selectivity observed under both diotic and dichotic conditions (for large frequency separations of masker and signal) reflect the operation of a common peripheral filter.

Acoustic Stimulation↗
PubMed1982

The effects of haloperidol on learning and behavior in autistic children.

The effects of haloperidol on behavioral symptoms and learning were critically assessed in autistic children in an ongoing double-blind placebo-controlled clinical trial. Children were randomly assigned to haloperidol-placebo-haloperidol or placebo-haloperidol-placebo treatment sequences. Statistically, haloperidol was significantly superior to placebo in reducing behavioral symptoms. In discrimination learning paradigm, children receiving haloperidol learned the discrimination while those on placebo did not. Discrimination attained on haloperidol was retained when the children were switched to placebo.

Autistic Disorder↗
PubMed1982

Suppression effects for complex stimuli.

A pulsation-threshold paradigm was used to evaluate suppression effects within complex stimuli. Stimuli were chosen to represent a continuum of spectral complexity ranging from sinusoids to complexes with one and two suppressors. Results indicate that suppression effects exist between the response to components of complex stimuli. For frequencies above a single suppressor, the suppression region is broad whereas below a suppressor, the region is relatively narrow. With two suppressors, little additivity of suppression is seen. When they are spaced closely, the response to the higher-frequency suppressor is reduced, presumably due to the low-frequency suppressor; this tends to diminish spectral contrasts despite considerable suppression at frequencies between the two suppressors. Enhancement of contrasts is greatest when suppressors are widely spaced and when both are presented at moderate levels (less than or equal to dB SPL). These data suggest that suppression may not play a simple role of "peak enhancement" in the peripheral coding of steady-state vowels.

Acoustic Stimulation↗
PubMed1980

Detection of signals with identical energy spectra but different waveforms under conditions of signal uncertainty.

Previous research has shown that a signal which may be one of two pure tones will be less detectable than a signal that is of constant, known frequency. In the present study, the effect of waveform uncertainty was evaluated by using pulse-train signals with identical power spectra but different phase spectra. Results for a group of 11 listeners suggest that when differences in the energy spectra of signals are eliminated, signal uncertainty has, at best, a small effect on detection performance.

Acoustic Stimulation↗
PubMed1980

Some observations on simultaneous and nonsimultaneous masking.

The interactions between phase, signal level, and interstimulus interval (delta t) were examined in the transition region between simultaneous and nonsimultaneous masking. Phase effects as large as 22 dB were observed in forward masking. These trends can be explained by considering the effects of phase upon the stimulus envelope.

Acoustic Stimulation↗