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Biomedical subjects

R Efron

Publications and source records attributed to R Efron.

At least 37 records · Page 2Linked to original sources
PubMed1983

Central auditory processing. II. Effects of anterior temporal lobectomy.

Ear dominance for the pitch of dichotically presented tonal stimuli was measured in nine patients before and after a unilateral anterior temporal lobectomy. Four subjects had a left and five had a right lobectomy. Every patient exhibited a change of ear dominance consistent with the hypothesis that a unilateral lobectomy decreases the perceptual salience of the tone presented to the ear contralateral to the lesion. Depending on the direction and magnitude of the subject's preoperative ear dominance and the side of the lobectomy, the postoperative results either increased or decreased the strength of ear dominance in a predictable fashion. The results support the idea that within each temporal lobe lie physiological mechanisms which can enhance the perceptual salience of the acoustic signal emitted by one sound source when other, concurrent, spatially separated sound sources are present. It is also argued that the same mechanism operates on speech, melodic, and tonal signals.

Auditory Pathways↗
PubMed1983

Central auditory processing. III. The "cocktail party" effect and anterior temporal lobectomy.

The capacity to selectively attend to only one of multiple, spatially separated. simultaneous sound sources--the "cocktail party" effect--was evaluated in normal subjects and in those with anterior temporal lobectomy using common environmental sounds. A significant deficit in this capacity was observed for those stimuli located on the side of space contralateral to the lobectomy, a finding consistent with the hypothesis that within each anterior temporal lobe is a mechanism that is normally capable of enhancing the perceptual salience of one acoustic stimulus on the opposite side of space, when other sound sources are present on that side. Damage to this mechanism also appears to be associated with a deficit of spatial localization for sounds contralateral to the lesion.

Attention↗
PubMed1983

Central auditory processing. IV. Ear dominance--spatial and temporal complexity.

Ear dominance for dichotically presented tones was measured in 63 righthanded subjects when the frequency difference (delta f) was small compared to the center frequency (fc) and again when it was large. Although two-thirds of the population exhibited a left-ear dominance in both conditions, a shift toward right-ear dominance occurred when the delta f was increased. An additional study, employing the alternating tone illusion described by Deutsch, revealed the same general effect, i.e., a shift toward right-ear dominance with increasing values of delta f/fc. The results of these experiments, coupled with a review of previously published data of other dichotic experiments, indicate that as the ratio of delta f/fc increases, the subjective complexity of the sound image increases, and there is a progressive emergence of a "right-ear advantage" (or ear dominance). A tentative explanation relates these results to the effects of anatomical asymmetries of primary and auditory association cortex and the efferent temporal lobe enhancement mechanism described by R. Efron, P.H. Crandall, B. Koss, P.L. Divenyi, and E.W. Yund (Brain and Language, 1983, 19, 254-263.

Adolescent↗
PubMed1979

The effect of bone conduction on the intensity independence of dichotic chords.

The relative salience of the pitch components of a two-tone dichotic chord is invariant with respect to the relative intensity of the two tones over a wide range of interaural intensity differences [R. Efron and E. W. Yund, J. Acoust, Soc. Am. 889--898 (1976)]. According to a recently developed model, the range of intensity independence is limited by the bone-conducted energy from the more intense tone [E. W. Yund and R. Efron, J. Acoust. Soc. Am. 62, 607--617 (1977)]. The model predicts that a decrease in bone conduction such as the one achieved by using insertion earphones, must increase the range of intensity independence. This prediction is confirmed.

Bone Conduction↗
PubMed1979

Individual differences in the perception of dichotic chords.

A new method was employed to measure the changes in the strength of ear dominance in the perception of dichotic chords as a function of stimulus intensity. The results of the first experiment, where the right and left tones were of equal intensity, revealed striking individual differences in the way the ear dominance of five subjects changed as the intensity of the chords was varied over a 60-dB range--no two subjects exhibiting the same pattern of behavior. Since, within the context of the model of Yund and Efron [J. Acoust. Soc. Am. 62, 607-617 (1977)] these individual differences could result from right-left asymmetries in the subject's intensity-response (I-R) transduction mechanisms, a second experiment was performed in which the two tones had different intensities. From the results of the second experiment the shape of the I-R function for each ear could be computed. Using these I-R functions as parameters, the model accurately predicted the idiosyncratic changes of ear dominance observed in the first experiment. The right-left asymmetries in the I-R functions also a-count for previously reported idiosyneratic changes in ear dominance as a function of the frequency difference between the two tones of the dichotic chord.

Acoustic Stimulation↗
PubMed1977

Perception of dichotic chords by normal and commisurotomized human subjects.

A perceptual suppression of an ipsilateral by a concurrent contralateral auditory signal occurs in commissurotomized subjects and probably in normal subjects. This suppression of the ipsilateral signal depends on the nature of the auditory stimuli. For dichotic speech sounds the suppression of the ipsilateral signal is overwhelming; for dichotically presented pure tones it is not present. For dichotically presented pure tones, unlike speech signals, a subcortical central pitch processor determines the contribution to the perceptual experience of the right and left ear signals in both normal as well as commissurotomized subjects.

Acoustic Stimulation↗