Exploring a possible tonal loop in musicians and non-musicians and the relationship between musical expertise and cognitive ageing
This thesis explored two main research questions, firstly investigating whether musical expertise offers a performance advantage in working memory for sequences of tones that vary in pitch, and secondly whether any advantage of musical expertise may be present in older as well as younger individuals. Previous research on working memory for tone sequences has reported that articulatory suppression interferes with temporary storage of verbal but not with tone sequences (Koelsch et al, 2009), suggesting a “tonal loop” within a musician’s working memory (Schulze, Zysset, Mueller, Friederici, & Koelsch, 2011) that complements the phonological loop for verbal material in musicians and non-musicians alike (e.g., Baddeley, 1986; 1992). The five experiments reported here explored detection of a pitch change between pairs of tone sequences with or without concurrent articulatory suppression or singing suppression. In Experiment 1, with pairs of auditory tonal (in a musical key) sequences to be compared, singing suppression impaired non-musicians significantly more than musicians, although both groups showed an impairment, whereas only non-musicians were affected by verbal articulatory suppression. In Experiment 2, conducted only with musicians who could read music, the first sequence of each pair was presented visually and the second sequence for comparison was presented aurally. Musicians were again impaired by singing suppression but not by articulatory suppression. For Experiment 3, for auditory atonal (no musical key) pairs of sequences, non-musicians performed at floor, and musicians were again significantly more impaired by singing suppression than by articulatory suppression. In contrast, for Experiment 4, only with musicians who could read music, for visually presented atonal sequences each followed by an auditory atonal sequence for comparison, musicians were significantly more impaired by articulatory suppression than singing suppression. These results suggest that for tonal sequences, musicians use their musical training and experience, coupled with subvocalised singing, but for atonal sequences, additional strategies involving phonological rehearsal may be used. Non-musicians may also rely on musical experience and subvocal singing for tonal sequences but seem to be unable to do so for atonal sequences. Results are consistent with the use by both musicians and non-musicians of a tonal loop for the rehearsal of tone sequences, which develops with musical training and may be used in addition to subvocal rehearsal. Previous research has suggested musical expertise may offer some protection against cognitive ageing (Hanna-Pladdy & MacKay, 2011; Amer, Kalender, Hasher, Trehub, & Wong, 2013). Experiment 5 in this thesis explored whether a lifetime of musical training and experience may offer the same advantages in old age for retaining tone sequences that had been found in Experiments 1 and 3 for younger musicians. This experiment also considered whether any advantage for older musicians on this task could be explained by the proposed “bilingual advantage” (e.g., Bialystok, Craik, Klein & Viswanathan, 2004), and what other aspects of cognition might be associated with tone sequence memory performance. A test battery was utilised with 74 older adults (60-80 years of age) to assess the influence of musical and language expertise, and cognitive abilities (attention, working memory capacity, self-reported prospective and retrospective memory) on the music-related pitch sequence comparison task from Experiments 1 and 3. Working memory capacity was found to predict individual differences in the ability to detect pitch changes between pairs of tone sequences, regardless of musical experience. Older musicians performed more poorly on the pitch change detection task overall than the younger musicians in the earlier experiments, but their performance on the task was significantly better than for age-matched non-musically trained peers who were close to floor for both tonal and atonal sequences, suggesting some benefit from a lifetime of musical experience.