Concurrent Vocalization Research Articles

Finding Your Mate at a Cocktail Party: Frequency Separation Promotes Auditory Stream Segregation of Concurrent Voices in Multi-Species Frog Choruses

Vocal communication in crowded social environments is a difficult problem for both humans and nonhuman animals. Yet many important social behaviors require listeners to detect, recognize, and discriminate among signals in a complex acoustic milieu comprising the overlapping signals of multiple individuals, often of multiple species. Humans exploit a relatively small number of acoustic cues to segregate overlapping voices (as well as other mixtures of concurrent sounds, like polyphonic music). By comparison, we know little about how nonhuman animals are adapted to solve similar communication problems. One important cue enabling source segregation in human speech communication is that of frequency separation between concurrent voices: differences in frequency promote perceptual segregation of overlapping voices into separate “auditory streams” that can be followed through time. In this study, we show that frequency separation (ΔF) also enables frogs to segregate concurrent vocalizations, such as those routinely encountered in mixed-species breeding choruses. We presented female gray treefrogs (Hyla chrysoscelis) with a pulsed target signal (simulating an attractive conspecific call) in the presence of a continuous stream of distractor pulses (simulating an overlapping, unattractive heterospecific call). When the ΔF between target and distractor was small (e.g., ≤3 semitones), females exhibited low levels of responsiveness, indicating a failure to recognize the target as an attractive signal when the distractor had a similar frequency. Subjects became increasingly more responsive to the target, as indicated by shorter latencies for phonotaxis, as the ΔF between target and distractor increased (e.g., ΔF = 6–12 semitones). These results support the conclusion that gray treefrogs, like humans, can exploit frequency separation as a perceptual cue to segregate concurrent voices in noisy social environments. The ability of these frogs to segregate concurrent voices based on frequency separation may involve ancient hearing mechanisms for source segregation shared with humans and other vertebrates.

Temporal Coding of Concurrent Acoustic Signals in Auditory Midbrain

A fundamental problem faced by the auditory system of humans and other vertebrates is the segregation of concurrent vocal signals. To discriminate between individual vocalizations, the auditory system must extract information about each signal from the single temporal waveform that results from the summation of the simultaneous acoustic signals. Here, we present the first report of midbrain coding of simultaneous acoustic signals in a vocal species, the plainfin midshipman fish, that routinely encounters concurrent vocalizations. During the breeding season, nesting males congregate and produce long-duration, multiharmonic mate calls that overlap, producing beat waveforms. Neurophysiological responses to two simultaneous tones near the fundamental frequencies of natural calls reveal that midbrain units temporally code the difference frequency (dF). Many neurons are tuned to a specific dF; their selectivity overlaps the range of dFs for naturally occurring acoustic beats. Beats and amplitude-modulated (AM) signals are also coded differently by most units. Although some neurons exhibit differential tuning for beat dFs and the modulation frequencies (modFs) of AM signals, others exhibit similar temporal selectivity but differ in their degree of synchronization to dFs and modFs. The extraction of dF information, together with other auditory cues, could enable the detection and segregation of concurrent vocalizations, whereas differential responses to beats and AM signals could permit discrimination of beats from other AM-like signals produced by midshipman. A central code of beat dFs may be a general vertebrate mechanism used for coding concurrent acoustic signals, including human vowels.

Cerebral lateralization for speech production in congenitally blind adolescents

The effect of early visual deprivation on cerebral lateralization for speech production was investigated using the dual‐task paradigm (tapping with concurrent vocalization). Some 28 right‐handed subjects (14 congenitally blind and 14 normal‐sighted adolescents matched on the basis of sex and age) participated in this study. Results reveal significant suppressions from baseline tapping rates under concurrent vocalization with the right but not the left hand for both groups. These findings suggest that congenital blindness per se does not alter the normal pattern of left hemispheric dominance for speech. The role of adequate early linguistic environmental experience on language lateralization is discussed.

Bimanual handwriting reveals delayed interhemispheric integration in childhood stuttering

Three age groups each (6 to 8, 9 to 11, 12 to 15 years) of right‐handed male stutterers and nonstutterers performed a bimanual handwriting task under five conditions: Condition 1) bimanual handwriting, no vocalization; Condition 2) replication of Condition 1; Condition 3) bimanual handwriting with concurrent vocalization of the letter or digit being written; Condition 4) bimanual handwriting of a letter or digit with attention directed to the left hand; and Condition 5) bimanual handwriting of a letter or digit with attention directed to the right hand. Differences in bimanual handwriting organization and in mirror reversals of digits and letters suggest the hypothesis that interhemispheric integration emerges around age 9 for non‐stutterers, but remains immature at least through age 15 for stutterers.

The Effects of Concurrent Vocalization on Foot and Hand Motor Performance: A Test of the Functional Distance Hypothesis

The effects of concurrent vocalization on hand and foot motor performance were examined in two dual-task experiments as a test of the functional distance hypothesis. No interference effects were found with either hand or foot tapping under two difficulty levels of verbal activity. There was no evidence of differential or asymmetrical interference patterns despite the differential functional and anatomical distances of these motor centers from the sppech centers. Consequently, the data provided no support for the functional distance hypothesis.

Sex differences in lateralization for spatial abilities

Sex differences in cerebral lateralization for spatial abilities were studied using a dual-task paradigm. In the first phase of this experiment, both males and females were found to display similar cerebral lateralization patterns for manipulospatial processing of block designs across two levels of difficulty. There was no evidence of laterality effects in right-hand or left-hand tapping, but analysis of trade-off effects revealed that both males and females took significantly longer to solve the block designs when simultaneously tapping with the right hand and manipulating the block designs with the left hand. No specific lateralization patterns were found either within or between sexes. In Phase 2 of this study, it was observed that females may use a verbal mediation strategy in manipulospatial processing insofar as interference effects were found during concurrent vocalization and manipulospatial processing in females.

Control of echolocation pulses by neurons of the nucleus ambiguus in the rufous horseshoe bat, Rhinolophus rouxi. I. Single unit recordings in the ventral motor nucleus of the laryngeal nerves in spontaneously vocalizing bats.

The vocal motor control of the larynx was studied with single unit recordings from the efferent motor nucleus (nucleus ambiguus) in the CF-FM-bat Rhinolophus rouxi, spontaneously emitting echolocation sounds. The experiments were performed in a stereotaxic apparatus that allowed differentiation of activities in the recorded nucleus depending on the electrode position (Fig. 1). Echolocation calls and respiration activity were monitored simultaneously, thus it was possible to compare the time course of the motor control activity during respiration with and without concurrent vocalization. Unit discharges were classified as laryngeal motoneuron activity according to their correlation with the time course (onset and end) of echolocation calls and their discharge rate as: Pre-off-tonic, pre-off-phasic, off-pauser, off-tonic, on-chopper, on-tonic, prior-tonic and inhibitory (Fig. 4). The on-chopper and on-tonic discharge patterns were assigned to the motor activity of the lateral cricoarytenoid muscle and the off-pauser and off-tonic discharge patterns to the motor activity of the posterior cricoarytenoid muscle controlling the time course of vocal pulses. Motoneuron activities recorded under the condition of systematically shifted frequencies in the emitted echolocation calls were investigated in Doppler-shift compensating bats responding to electronically simulated echoes. Of all neurons classified as motor control, only units of the pre-off-tonic discharge type (cricothyroid muscle) changed their activity with frequency shifts in the vocalized pulses; they showed a positive linear correlation with the emitted sound frequency (Fig. 6). In addition, single unit activities in strict synchronization to vocalization were recorded, that by their low discharge rate were not valid as motor control, and were considered to represent activities of interneurons or internuclear neurons connecting the nucleus ambiguus with other vocalization- and respiration-centers (Fig. 3c). Electric lesions in the brain stem and iontophoretically applied horseradish peroxidase (HRP) served as references for localization and morphological identification of the recording sites in cell stained brain slices.

Reliability of verbal-manual interference

Considerable recent research has used unimanual finger tapping with concurrent vocalization to assess hemispheric lateralization for language. This study examined whether an index finger tapping task is a reliable measure in adults and whether the task demonstrates sex differences in hemispheric specialization for language. Thirty right-handed subjects, fifteen male and fifteen female, between the ages of 18 and 25 were tested. The task measured the differences in tapping rate for each hand between tapping with and without a concurrent verbal task. The task was completed once each day for 3 consecutive days to determine reliability. The tapping task was found to be a reliable measure. No significant differences were found between tapping scores of males and females.

Reading and writing in English and Japanese: A cross‐cultural study of young children*

We report a series of experiments which compare the ways in which Japanese and English children read and write single words. The Japanese children read and wrote the words in two types of script, kana and kanji. The first of these consists of symbols which signify syllables, and the second entirely of ideograms. Both groups read and wrote words with and without concurrent vocalization. Concurrent vocalization had no apparent effect on reading or writing kanji: nor did it affect reading English words. But it did consistently impede reading and writing kana words and it did impair writing English. We conclude, tentatively, that English children may read words without the help of prelexical phonological analysis, but that they spell them on the basis of sound‐symbol relationships. We also conclude that there may be no such sharp distinction between reading and writing in either of the two types of Japanese script.

The visual tongue-twister effect: Phonological activation in silent reading

We discuss the activation of phonological information during silent reading and report two experiments demonstratng a visual tongue-twister effect. Judgments of semantic acceptability took longer for sentences which repeated initial consonants or consonant pairs differing only in voicing such as /p/ and /b/ (tongue-twisters), compared with matched phonetically “neutral” sentences (those containing a natural mix of phenemes). In addition, concurrent vocalization with a tongue-twister phrase slowed performance, but did not produce reliable specific interference when the vocalization phrase repeated the same word-initial consonant (for example, bilabial /p/) as the sentences being read. We argue that the longer reading times for tongue-twisters is caused by interference due to the similarity of the phonetic representations automatically activated during reading. The lack of specific interference between concurrent vocalization and the reading task suggests that these automatically activated phonetic repreesntations are not subvocal motor programs and that the concurrent vocalization paradigm is not an appropriate method to examine the phonological information used during reading.

The Use of Matrix Training to Teach Concurrent Appropriate Actions and Vocalizations during Sociodramatic Play in a Child with Autism

Play skills are important for children to develop because they expand social and communicative skills (Lewis, 2003). Children with autism show impaired play skills because of repetitive or stereotypic behaviour (Jung & Sainato, 2013). Matrix training is defined as a generative form of instruction in which targets are organizaed in a matrix, and it is commonly used to teach communication (Axe & Sainato, 2010). After some skill combinations are taught, other untaught skill combinations within the matrix are tested for generative learning and responding (MacManus et al., 2015). A multiple-probe design was employed to test whether matrix training can teach play actions and language use during sociodramatic play in a 6-year-old boy with autism in an intensive behavioural intervention setting. Scripted actions and vocalizations were each arranged in a two-dimensional matrix and probe data were collected for correct responding with both components of the target play skills. The data showed an increasing trend and after teaching of three target combinations, the participant generalized four of the six alternative untrained combinations for actions and vocalizations. The mean level of acquired combinations was 83.33% by the end of the generalization phase. A visual analysis, using PEM, showed that the use of two parallel matrices was effective to concurrently increase both action and vocalization components of play.