Discriminating predation attempt outcomes during natural foraging using the post-buzz pause in Japanese large-footed bat Myotis macrodactylus

Bats emit a series of echolocation calls with an increasing repetition rate (the terminal buzz), when attempting to capture prey. This is often used as an acoustic indicator of prey-capture attempts. However, because it is directly linked to foraging efficiency, predation success is a more useful measure than predation attempts in ecological research. The characteristics of echolocation calls that consistently signify predation success across different situations have not been identified. Due to additional influencing factors, identification of these characteristics is particularly challenging for wild bats foraging in their natural environment compared to those in flight chambers. This study documented the natural foraging behavior of wild Japanese large-footed bat Myotis macrodactylus using synchronized acoustic and video recordings. From the video recordings, we could assign 137 attacks to three outcome categories: prey captured (51.8%), prey dropped (29.2%), and failed attempt (19%). Based on previous indications from laboratory studies that the length of the silent interval following the terminal buzz (post-buzz pause) might reflect the prey capture outcome, we compared post-buzz pause durations among categories of attack outcomes. The post-buzz pause was longest in the case of successful capture, suggesting that the length of the post-buzz pause is a useful acoustic indicator of predation success during natural foraging in M. macrodactylus. Our finding will advance the study of bat foraging behavior using acoustic data, including estimations of foraging efficiency and analyses of feeding habitat quality.Summary statementWe investigated the natural foraging behavior of wild Myotis macrodactylus and found that the length of the post-buzz pause is a useful acoustic indicator of predation success.

Effect of Clear Speech on the Duration of Silent Intervals at Syntactic and Phonemic Boundaries in the Speech of Individuals With Parkinson Disease

Purpose The purpose of the current investigation was to determine the extent to which individuals with and without Parkinson disease (PD) modified silent interval durations when using a clear speaking style. Method Ten individuals with idiopathic PD and 10 older adult control speakers produced a reading passage using both habitual and clear speaking styles. Silent intervals lasting 15 ms and longer were identified and extracted. Each silent interval was categorized according to the surrounding syntactic context of the reading passage. In addition, voiceless stop gaps that occurred within words, phrases, or clauses were categorized by the preceding phonemic context. Results Statistical analyses revealed that all participants increased silent interval duration with a clear speaking style at inter-sentence and intra-sentence syntactic boundaries. Compared to controls, individuals with PD exhibited significantly less increase in silent interval durations at these syntactic boundaries. Control speakers also increased silent stop gap durations in the clear speaking style regardless of preceding phonemic context. Individuals with PD, however, only increased stop gap duration when the silent interval was preceded by a sonorant. Conclusion These findings suggest that speakers with PD exhibit less clarity-related increase in silent interval duration than control speakers. In addition, speakers with PD exhibited significant increases in silent interval duration that coincided with syntactic boundaries of the reading passage but little to no clarity-related modulation of stop gap intervals. Therefore, these data suggest that speakers with PD exhibited changes in silent interval durations that were more so associated with modulation of speech prosody than articulation when using a clearer speaking style.

Auditory prediction errors as individual biomarkers of schizophrenia

Schizophrenia is a complex psychiatric disorder, typically diagnosed through symptomatic evidence collected through patient interview. We aim to develop an objective biologically-based computational tool which aids diagnosis and relies on accessible imaging technologies such as electroencephalography (EEG). To achieve this, we used machine learning techniques and a combination of paradigms designed to elicit prediction errors or Mismatch Negativity (MMN) responses. MMN, an EEG component elicited by unpredictable changes in sequences of auditory stimuli, has previously been shown to be reduced in people with schizophrenia and this is arguably one of the most reproducible neurophysiological markers of schizophrenia.EEG data were acquired from 21 patients with schizophrenia and 22 healthy controls whilst they listened to three auditory oddball paradigms comprising sequences of tones which deviated in 10% of trials from regularly occurring standard tones. Deviant tones shared the same properties as standard tones, except for one physical aspect: 1) duration-the deviant stimulus was twice the duration of the standard; 2) monaural gap-deviants had a silent interval omitted from the standard, or 3) inter-aural timing difference, which caused the deviant location to be perceived as 90° away from the standards.We used multivariate pattern analysis, a machine learning technique implemented in the Pattern Recognition for Neuroimaging Toolbox (PRoNTo) to classify images generated through statistical parametric mapping (SPM) of spatiotemporal EEG data, i.e. event-related potentials measured on the two-dimensional surface of the scalp over time. Using support vector machine (SVM) and Gaussian processes classifiers (GPC), we were able classify individual patients and controls with balanced accuracies of up to 80.48% (p-values = 0.0326, FDR corrected) and an ROC analysis yielding an AUC of 0.87. Crucially, a GPC regression revealed that MMN predicted global assessment of functioning (GAF) scores (correlation = 0.73, R2 = 0.53, p = 0.0006)

Attentional Capacity Limits Gap Detection during Concurrent Sound Segregation

Detecting a brief silent interval (i.e., a gap) is more difficult when listeners perceive two concurrent sounds rather than one in a sound containing a mistuned harmonic in otherwise in-tune harmonics. This impairment in gap detection may reflect the interaction of low-level encoding or the division of attention between two sound objects, both of which could interfere with signal detection. To distinguish between these two alternatives, we compared ERPs during active and passive listening with complex harmonic tones that could include a gap, a mistuned harmonic, both features, or neither. During active listening, participants indicated whether they heard a gap irrespective of mistuning. During passive listening, participants watched a subtitled muted movie of their choice while the same sounds were presented. Gap detection was impaired when the complex sounds included a mistuned harmonic that popped out as a separate object. The ERP analysis revealed an early gap-related activity that was little affected by mistuning during the active or passive listening condition. However, during active listening, there was a marked decrease in the late positive wave that was thought to index attention and response-related processes. These results suggest that the limitation in detecting the gap is related to attentional processing, possibly divided attention induced by the concurrent sound objects, rather than deficits in preattentional sensory encoding.

Effects of a Preparatory Singing Pattern on Melodic Dictation Success

The purpose of this study was to investigate effects of a preparatory contextual singing pattern on melodic dictation test scores. Forty-nine undergraduate music education majors took melodic dictations under three conditions. After hearing an orienting chord sequence, they (1) sang a preparatory solfége pattern in the key, meter, and tempo of the target dictations in the first condition; (2) prepared themselves silently during an equivalent time interval in the second condition; and (3) took the dictations immediately in the third condition. A repeated measures ANOVA and post hoc analysis revealed that participants scored significantly higher when they heard the dictation immediately following the chord sequence than when they sang the preparatory pattern first. Participants may have been distracted by the additional task of singing, interfering with their focus on the ensuing dictation. They reported a variety of preparatory strategies during the silent interval condition, suggesting that dictation students may benefit from learning multiple strategies and choosing what works best for them. Future research might investigate the relationship between strategies used during dictation and strategies used just prior to dictation. Implications for music educators include the need for careful decisions regarding when and how to combine musical tasks for student learning.

No Sustained Sound Illusion in Rhythmic Sequences

Recent Research has shown that subdivision of intervals between beats makes the beat tempo seem slower——a "divided time illusion" (DTI) in music. Another temporal illusion described in the psychophysical literature is that a sustained sound seems longer than a silent interval of the same duration. This "sustained sound illusion" (SSI) may be due to acceleration of an internal pacemaker by continuous sound, or it may result from slower perception of sound offsets than of sound onsets. Experiment 1 tested the pacemaker acceleration hypothesis in a rhythmic context by asking musicians to compare or reproduce the tempi of isochronous tone sequences played legato ("filled") or staccato ("unfilled"). There was no indication that legato sequences were perceived as slower than staccato sequences. Experiment 2 tested the delayed offset perception hypothesis by asking musicians to judge the relative time of occurrence of abrupt or decaying tone offsets in the interonset intervals of isochronous sequences. There was no evidence of delayed perception of abrupt offsets, and decaying offsets were perceived only slightly late. These results suggest that the SSI, unlike the DTI, does not occur in rhythmic contexts and thus is probably not of musical relevance. More generally, the results challenge some proposed explanations of this illusion and call for further research on the conditions under which it does occur.