Rappresentazioni mentali della musica: studi comportamentali sull'interazione uditivo-motoria durante l'analisi dell'altezza dei suoni e brain imaging funzionale della rappesentazione del ritmo

The experimental studies presented in this thesis concern two different research projects. The first one aimed to study the auditory-motor interaction in pianists with respect to the pitch-height processing. The second one aimed to study the neural underpinnings of musical rhythm subcomponents (Pattern, Meter and Tempo) processing. The auditory-motor interaction in pianists during pitch-height processing has been investigated by means of four behavioral experiments. In the first one, three group of participants (pianists, nonpianists musicians and non-musicians) were tested with a shape decision task where left-hand and right-hand responses were required; each visual stimulus was paired with an auditory task-irrelevant stimulus (high-pitched or low-pitched piano-timbre chords). Of the three groups, only pianists had longer reaction times for left-hand/high-pitched chords and right-hand/low-pitched chords associations. These findings are consistent with an auditory-motor interaction effect elicited by pitch dimension, as only pianists show an interaction between motor responses and implicit pitch processing. This interaction is consistent with the canonical mapping of hand gestures and pitch dimension on the piano keyboard. The second experiment was aimed to study the temporal dynamic of the emerged effect. We used the same experimental procedure of the Experiment 1, varying only the Stimulus Onset Asinchrony between the auditory and visual stimuli. The results shown that the effect was stable within a time-window of 0-400 ms. The aim of the third experiment was to study whether a spatial representation was involved in the effect emerged in Experiment 1. The same experimental task used in Experiment 1 was proposed to a fresh group of pianists, with the only difference that participants responded with their hands crossed. Using this manipulation the effect of association disappeared, suggesting that motor and spatial representation are involved at the same time. The fourth experiment was aimed to confirm the hypothesis that a spatial representation was involved in the effect emerged in Experiment 1. A fresh group of pianists was tested with the same task of Experiment 1 with the only difference that participants responded by pressing two pedals with their feet. The results replicate those of Experiment 1 and are consistent with the involvement of spatial representations. The second project was aimed to study the brain basis of musical rhythm perception. The temporal organisation of music is composed of distinct independent features such as Pattern, Meter and Tempo, and each feature has a different computational processing, likely requiring different neural mechanisms. Nonetheless, there is a lack of clear evidence at present to assess such differences. To this aim, the present study compared the neural basis of the perception of these rhythmic features. The functional brain activity of healthy musicians and non-musicians was recorded with positron emission tomography (PET) as they made covert same-different discriminations of pairs of rhythmic, monotonic musical sequences, or pairs of isochronous melodies. Brain activity observed here suggests that meter processing recruits a more cognitive, abstract, multi-modal (visualauditory) set of mechanisms, than does processing pattern or tempo. Pattern processing recruits a set of mechanisms involved in auditory and emotion information, and tempo processing engages mechanisms subserving somatosensory, premotor, and emotion information. Moreover, musicians seem to recruit higher level representations in temporal, occipital, and frontal areas, whereas nonmusicians use more sensory-motor, basal ganglia (putamen, caudate), and cerebellar mechanisms.