Recognizing structure in novel tunes: differences between human and rats.

A central feature in music is the hierarchical organization of its components. Musical pieces are not a simple concatenation of chords, but are characterized by rhythmic and harmonic structures. Here, we explore if sensitivity to music structure might emerge in the absence of any experience with musical stimuli. For this, we tested if rats detect the difference between structured and unstructured musical excerpts and compared their performance with that of humans. Structured melodies were excerpts of Mozart's sonatas. Unstructured melodies were created by the recombination of fragments of different sonatas. We trained listeners (both human participants and Long-Evans rats) with a set of structured and unstructured excerpts, and tested them with completely novel excerpts they had not heard before. After hundreds of training trials, rats were able to tell apart novel structured from unstructured melodies. Human listeners required only a few trials to reach better performance than rats. Interestingly, such performance was increased in humans when tonality changes were included, while it decreased to chance in rats. Our results suggest that, with enough training, rats might learn to discriminate acoustic differences differentiating hierarchical music structures from unstructured excerpts. More importantly, the results point toward species-specific adaptations on how tonality is processed.

Detecting surface changes in a familiar tune: exploring pitch, tempo and timbre.

Humans recognize a melody independently of whether it is played on a piano or a violin, faster or slower, or at higher or lower frequencies. Much of the way in which we engage with music relies in our ability to normalize across these surface changes. Despite the uniqueness of our music faculty, there is the possibility that key aspects in music processing emerge from general sensitivities already present in other species. Here we explore whether other animals react to surface changes in a tune. We familiarized the animals (Long-Evans rats) with the "Happy Birthday" tune on a piano. We then presented novel test items that included changes in pitch (higher and lower octave transpositions), tempo (double and half the speed) and timbre (violin and piccolo). While the rats responded differently to the familiar and the novel version of the tune when it was played on novel instruments, they did not respond differently to the original song and its novel versions that included octave transpositions and changes in tempo.

Spanish-learning infants switch from a vowel to a consonant bias during the first year of life.

The consonant bias is evidenced by a greater reliance on consonants over vowels in lexical processing. Although attested during adulthood for most Roman and Germanic languages (e.g., French, Italian, English, Dutch), evidence on its development suggests that the native input modulates its trajectory. French and Italian learners exhibit an early switch from a higher reliance on vowels at 5 and 6 months of age to a consonant bias by the end of the first year. This study investigated the developmental trajectory of this bias in a third Romance language unexplored so far-Spanish. In a central visual fixation procedure, infants aged 5, 8½, and 12 months were tested in a word recognition task. In Experiment 1, infants preferred listening to frequent words (e.g., leche, milk) over nonwords (e.g., machi) at all ages. Experiment 2 assessed infants' listening times to consonant and vowel alterations of the words used in Experiment 1. Here, 5-month-olds preferred listening to consonant alterations, whereas 12-month-olds preferred listening to vowel alterations, suggesting that 5-month-olds' recognition performance was more affected by a vowel alteration (e.g., leche →lache), whereas 12-month-olds' recognition performance was more affected by a consonant alteration (e.g., leche →keche). These findings replicate previous findings in Italian and French and generalize them to a third Romance language (Spanish). As such, they support the idea that specific factors common to Romance languages might be driving an early consonant bias in lexical processing.

Is the consonant bias specifically human? Long-Evans rats encode vowels better than consonants in words.

In natural languages, vowels tend to convey structures (syntax, prosody) while consonants are more important lexically. The consonant bias, which is the tendency to rely more on consonants than on vowels to process words, is well attested in human adults and infants after the first year of life. Is the consonant bias based on evolutionarily ancient mechanisms, potentially present in other species? The current study investigated this issue in a species phylogenetically distant from humans: Long-Evans rats. During training, the animals were presented with four natural word-forms (e.g., mano, "hand"). We then compared their responses to novel words carrying either a consonant (pano) or a vowel change (meno). Results show that the animals were less disrupted by consonantal alterations than by vocalic alterations of words. That is, word recognition was more affected by the alteration of a vowel than a consonant. Together with previous findings in very young human infants, this reliance on vocalic information we observe in rats suggests that the emergence of the consonant bias may require a combination of vocal, cognitive and auditory skills that rodents do not seem to possess.

Ternary meter from spatial sounds: Differences in neural entrainment between musicians and non-musicians.

The present study explores the relationship between the rhythmic structure of music and the spatial dimension of sound. We study how the brain interacts with spatially-separated sounds to build up a metrical structure. Participants listened to sequences of isochronous sounds that came from different positions on the azimuth plane: 0° (control condition), ±30°, ±60° or ±90° (spatial conditions). Ternary meter was signaled by the alternation of one sound on one side and two sounds on the symmetrical side. In Experiment 1, musicians and non-musicians paid attention to the spatial sounds. In Experiment 2, participants paid attention to a visual distractor. We recorded their electroencephalograms and performed frequency-tagging analyses. In both experiments, the isochronous beat elicited steady-state evoked-potentials at the frequency of the beat (2.4 Hz). While in Experiment 1 the alternation produced clear responses at the frequency of the ternary meter (0.8 Hz), in Experiment 2 these responses were only significant in the Spatial 90° condition, and mainly in musicians. This suggests that top-down attentional mechanisms are in play for meter induction. Besides, musicians showed stronger responses to beat and meter than non-musicians, suggesting that formal musical training enhances the neural entrainment to spatially-defined rhythms.

Differences in relative frequency facilitate learning abstract rules.

Humans learn the rules that govern how the elements of their language are organized over an input that is often not homogeneous (it might contain noise, or even include rules from different linguistic systems, as it might be the case for bilinguals). In the present study we explore the conditions under which participants can learn an abstract rule when it is presented in a heterogeneous context. Results from six experiments show that listeners can learn a token-independent rule even if it is presented together with some exemplars that implement a different regularity (Experiment 1a and 1b). In fact, learning rules from an input containing several patterns does not seem to differ from learning them from an input containing only one (Experiment 1c). More surprisingly, we observed that listeners can even learn an abstract rule that is only implemented over 10% of the exemplars that compose a familiarization stream (Experiments 2a and 2b). When the proportion of tokens implementing the target and the non-target rules is balanced, we did not observe any learning (Experiment 3). Our results suggest that listeners use differences in relative frequency to keep separate linguistic rules apart. This allows them to learn different abstract regularities from a non-homogeneous linguistic signal.

Direct Observation of Aryl Gold(I) Carbenes that Undergo Cyclopropanation, C-H Insertion, and Dimerization Reactions.

Mesityl gold(I) carbenes lacking heteroatom stabilization or shielding ancillary ligands have been generated and spectroscopically characterized from chloro(mesityl)methylgold(I) carbenoids bearing JohnPhos-type ligands by chloride abstraction with GaCl3 . The aryl carbenes react with PPh3 and alkenes to give stable phosphonium ylides and cyclopropanes, respectively. Oxidation with pyridine N-oxide and intermolecular C-H insertion to cyclohexane have also been observed. In the absence of nucleophiles, a bimolecular reaction, similar to that observed for other metal carbenes, leads to a symmetrical alkene.

Generalizing prosodic patterns by a non-vocal learning mammal.

Prosody, a salient aspect of speech that includes rhythm and intonation, has been shown to help infants acquire some aspects of syntax. Recent studies have shown that birds of two vocal learning species are able to categorize human speech stimuli based on prosody. In the current study, we found that the non-vocal learning rat could also discriminate human speech stimuli based on prosody. Not only that, but rats were able to generalize to novel stimuli they had not been trained with, which suggests that they had not simply memorized the properties of individual stimuli, but learned a prosodic rule. When tested with stimuli with either one or three out of the four prosodic cues removed, the rats did poorly, suggesting that all cues were necessary for the rats to solve the task. This result is in contrast to results with humans and budgerigars, both of which had previously been studied using the same paradigm. Humans and budgerigars both learned the task and generalized to novel items, but were also able to solve the task with some of the cues removed. In conclusion, rats appear to have some of the perceptual abilities necessary to generalize prosodic patterns, in a similar though not identical way to the vocal learning species that have been studied.

Gold(I) Carbenoids: On-Demand Access to Gold(I) Carbenes in Solution.

Chloromethylgold(I) complexes of phosphine, phosphite, and N-heterocyclic carbene ligands are easily synthesized by reaction of trimethylsilyldiazomethane with the corresponding gold chloride precursors. Activation of these gold(I) carbenoids with a variety of chloride scavengers promotes reactivity typical of metallocarbenes in solution, namely homocoupling to ethylene, olefin cyclopropanation, and Buchner ring expansion of benzene.

Experience-dependent emergence of a grouping bias.

Humans share with non-human animals perceptual biases that might form the basis of complex cognitive abilities. One example comes from the principles described by the iambic-trochaic law (ITL). According to the ITL, sequences of sounds varying in duration are grouped as iambs, whereas sequences varying in intensity are grouped as trochees. These grouping biases have gained much attention because they might help pre-lexical infants bootstrap syntactic parameters (such as word order) in their language. Here, we explore how experience triggers the emergence of perceptual grouping biases in a non-human species. We familiarized rats with either long-short or short-long tone pairs. We then trained the animals to discriminate between sequences of alternating and randomly ordered tones. Results showed animals developed a grouping bias coherent with the exposure they had. Together with results observed in human adults and infants, these results suggest that experience modulates perceptual organizing principles that are present across species.

Using isochrony, but not meter, to discriminate rhythmic sequences in rats (Rattus norvegicus).

Meter induction is a key process for rhythm perception. However, while some nonhuman animals readily detect temporal regularities and perceive beats in auditory sequences, there is no consistent evidence that they extract metrical structures. In the present experiment, we familiarized rats (Rattus norvegicus) to auditory rhythmic sequences that evoked a duple or a triple meter. We then tested their recognition of these familiar sequences when pitted against novel sequences that evoked no meter (isotonic), evoked a different meter (either duple or triple), or were nonmetrical (nonisochronous). The animals only discriminated isochronous from nonisochronous sequences. However, we found no evidence for meter induction, as the animals did not discriminate familiar from isotonic sequences or from sequences with a different meter. The findings suggest that, under a familiarization paradigm, the natural tendency of the animals is to focus on temporal rather than melodic changes to recognize rhythmic sequences. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Neural correlates of acoustic dissonance in music: The role of musicianship, schematic and veridical expectations.

In western music, harmonic expectations can be fulfilled or broken by unexpected chords. Musical irregularities in the absence of auditory deviance elicit well-studied neural responses (e.g. ERAN, P3, N5). These responses are sensitive to schematic expectations (induced by syntactic rules of chord succession) and veridical expectations about predictability (induced by experimental regularities). However, the cognitive and sensory contributions to these responses and their plasticity as a result of musical training remains under debate. In the present study, we explored whether the neural processing of pure acoustic violations is affected by schematic and veridical expectations. Moreover, we investigated whether these two factors interact with long-term musical training. In Experiment 1, we registered the ERPs elicited by dissonant clusters placed either at the middle or the ending position of chord cadences. In Experiment 2, we presented to the listeners with a high proportion of cadences ending in a dissonant chord. In both experiments, we compared the ERPs of musicians and non-musicians. Dissonant clusters elicited distinctive neural responses (an early negativity, the P3 and the N5). While the EN was not affected by syntactic rules, the P3a and P3b were larger for dissonant closures than for middle dissonant chords. Interestingly, these components were larger in musicians than in non-musicians, while the N5 was the opposite. Finally, the predictability of dissonant closures in our experiment did not modulate any of the ERPs. Our study suggests that, at early time windows, dissonance is processed based on acoustic deviance independently of syntactic rules. However, at longer latencies, listeners may be able to engage integration mechanisms and further processes of attentional and structural analysis dependent on musical hierarchies, which are enhanced in musicians.

Negative mental representations in infancy.

How do infants' thoughts compare to the thoughts adults express with language? In particular, can infants entertain negative representations, such as not red or not here? In four experiments, we used pupillometry to ask whether negative representations are possible without an external language. Eleven-month-olds were tested on their ability to detect and represent the abstract structure of sequences of syllables, defined by the relations identity and/or negation: AAAA (four identical syllables; Experiment 1), AAA¬A (three times the syllable A and one final syllable that is not A; Experiment 2), AA(A)(A)¬A (two-to-four times the syllable A and one final syllable that is not A; Experiment 3). Representing the structures in Experiments 2-3 requires a form of negation. Results suggest that infants are able to compute both identity and negation. More generally, these results lend credit to the hypothesis that the infant mind is equipped with rudimentary logical operators before language takes off.

Arc-shaped pitch contours facilitate item recognition in non-human animals.

Acoustic changes linked to natural prosody are a key source of information about the organization of language. Both human infants and adults readily take advantage of such changes to discover and memorize linguistic patterns. Do they so because our brain is efficiently wired to specifically process linguistic stimuli? Or are we co-opting for language acquisition purposes more general principles that might be inherited from our animal ancestors? Here, we address this question by exploring if other species profit from prosody to better process acoustic sequences. More specifically, we test whether arc-shaped pitch contours defining natural prosody might facilitate item recognition and memorization in rats. In two experiments, we presented to the rats nonsense words with flat, natural, inverted and random prosodic contours. We observed that the animals correctly recognized the familiarization words only when arc-shaped pitch contours were implemented over them. Our results suggest that other species might also benefit from prosody for the memorization of items in a sequence. Such capacity seems to be rooted in general principles of how biological sounds are produced and processed.

Non-human animals detect the rhythmic structure of a familiar tune.

The musical motives of a song emerge from the temporal arrangement of discrete tones. These tones normally have few durational values, and are organized in structured groups to create metrical patterns. In the present study we show that the ability to detect the rhythmic structure of a song, while ignoring surface changes, is also present in other species. We familiarized rats (Rattus norvegicus) with an excerpt of the Happy Birthday song. During test, we presented the animals with (i) the same excerpt of the familiarization, (ii) a constant-pitch version of the excerpt that reduced melodic intervals to only one tone (i.e., isotonic) but preserved rhythmic structure, and (iii) a rhythmically scrambled version of the excerpt that preserved the melodic intervals. The animals discriminated the rhythmically scrambled version from the versions that preserved the original rhythm. This demonstrates that rats were sensitive to at least some parts of the rhythmic structure of the tune. Together with previous findings, the present set of results suggests that the emergence of rhythmic musical universals might be based on principles shared with other species.

Discrimination of temporal regularity in rats (Rattus norvegicus) and humans (Homo sapiens).

The perception of temporal regularities is essential to synchronize to music and dance. Here, we explore the detection of isochrony in two mammal species. We trained rats (Rattus norvegicus) and humans (Homo sapiens) to discriminate sound sequences with regular intervals from sound sequences with irregular intervals using a go/no-go paradigm. We used four different tempi in the training sessions and two new tempi in the tests. We found that both rats and humans responded more to the novel regular test sequences than to the novel irregular test sequences. Differently from previous studies with birds, rats seem to have focused on the relative duration of the sounds, which means that they paid attention to global features defining the regularity of the sequences. In sum, this study suggests that detecting temporal regularities in sequences of sounds may have ancient evolutionary roots and could rely on timing mechanisms present in distantly related mammals. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Dissonant endings of chord progressions elicit a larger ERAN than ambiguous endings in musicians.

In major-minor tonal music, the hierarchical relationships and patterns of tension/release are essential for its composition and experience. For most listeners, tension leads to an expectation of resolution. Thus, when musical expectations are broken, they are usually perceived as erroneous and elicit specific neural responses such as the early right anterior negativity (ERAN). In the present study, we explored if different degrees of musical violations are processed differently after long-term musical training in comparison to day-to-day exposure. We registered the ERPs elicited by listening to unexpected chords in both musicians and nonmusicians. More specifically, we compared the responses of strong violations by unexpected dissonant endings and mild violations by unexpected but consonant endings (Neapolitan chords). Our results show that, irrespective of training, irregular endings elicited the ERAN. However, the ERAN for dissonant endings was larger in musicians than in nonmusicians. More importantly, we observed a modulation of the neural responses by the degree of violation only in musicians. In this group, the amplitude of the ERAN was larger for strong than for mild violations. These results suggest an early sensitivity of musicians to dissonance, which is processed as less expected than tonal irregularities. We also found that irregular endings elicited a P3 only in musicians. Our study suggests that, even though violations of harmonic expectancies are detected by all listeners, musical training modulates how different violations of the musical context are processed.

A Comparative Perspective on the Role of Acoustic Cues in Detecting Language Structure.

Most human language learners acquire language primarily via the auditory modality. This is one reason why auditory artificial grammars play a prominent role in the investigation of the development and evolutionary roots of human syntax. The present position paper brings together findings from human and non-human research on the impact of auditory cues on learning about linguistic structures with a special focus on how different types of cues and biases in auditory cognition may contribute to success and failure in artificial grammar learning (AGL). The basis of our argument is the link between auditory cues and syntactic structure across languages and development. Cross-species comparison suggests that many aspects of auditory cognition that are relevant for language are not human specific and are present even in rather distantly related species. Furthermore, auditory cues and biases impact on learning, which we will discuss in the example of auditory perception and AGL studies. This observation, together with the significant role of auditory cues in language processing, supports the idea that auditory cues served as a bootstrap to syntax during language evolution. Yet this also means that potentially human-specific syntactic abilities are not due to basic auditory differences between humans and non-human animals but are based upon more advanced cognitive processes.

Time course and functional neuroanatomy of speech segmentation in adults.

The present investigation was devoted to unraveling the time-course and brain regions involved in speech segmentation, which is one of the first processes necessary for learning a new language in adults and infants. A specific brain electrical pattern resembling the N400 language component was identified as an indicator of speech segmentation of candidate words. This N400 trace was clearly elicited after a short exposure to the words of the new language and showed a decrease in amplitude with longer exposure. Two brain regions were observed to be active during this process: the posterior superior temporal gyrus and the superior part of the ventral premotor cortex. We interpret these findings as evidence for the existence of an auditory-motor interface that is responsible for isolating possible candidate words when learning a new language in adults.

Early neural responses underlie advantages for consonance over dissonance.

Consonant musical intervals tend to be more readily processed than dissonant intervals. In the present study, we explore the neural basis for this difference by registering how the brain responds after changes in consonance and dissonance, and how formal musical training modulates these responses. Event-related brain potentials (ERPs) were registered while participants were presented with sequences of consonant intervals interrupted by a dissonant interval, or sequences of dissonant intervals interrupted by a consonant interval. Participants were musicians and non-musicians. Our results show that brain responses triggered by changes in a consonant context differ from those triggered in a dissonant context. Changes in a sequence of consonant intervals are rapidly processed independently of musical expertise, as revealed by a change-related mismatch negativity (MMN, a component of the ERPs triggered by an odd stimulus in a sequence of stimuli) elicited in both musicians and non-musicians. In contrast, changes in a sequence of dissonant intervals elicited a late MMN only in participants with prolonged musical training. These different neural responses might form the basis for the processing advantages observed for consonance over dissonance and provide information about how formal musical training modulates them.