The aim of this study was to model the components of rhythmic function in a case (H.J.) of acquired rhythmic disturbance. H.J. is a right-handed, amateur male musician who acquired arrhythmia in the context of a global amusia after sustaining a right temporoparietal infarct. His rhythmic disturbance was analysed in relation to three independent components using an autoregressive extension of Wing and Kristofferson's model of rhythmic timing. This revealed preserved error-correction and motor implementation capacities, but a gross disturbance of H.J.'s central timing system ("cognitive clock"). It rendered him unable to generate a steady pulse, prevented adequate discrimination and reproduction of novel metrical rhythms, and partly contributed to bi-manual co-ordination difficulties in his instrumental performance. The findings are considered in relation to the essential components of the cognitive architecture of rhythmic function, and their respective cerebral lateralisation and localisation. Overall, the data suggested that the functioning of the right temporal auditory cortex is fundamental to 'keeping the beat' in music. The approach is presented as a new paradigm for future neuropsychological research examining rhythmic disturbances.

Results of an experimental investigation of pattern production by a West African (Asante) master drummer are reported. He performed bimanual tapping, with the Kete time-line pattern in one hand and either a regular 3-pulse or a regular 4-pulse in the other hand. Experimental variables manipulated were pulse-stream size (three or four), pulse hand allocation (left or right), and recording protocol, which was either synchronous (played in relation to a computer-generated tone) or spontaneous (no tone). Structural equation modeling was used to systematically examine the comparative fit of two mental models: an asymmetric timeline- ground (TLG) model, which represents a computational elaboration of traditional African understanding, and a pulse-ground (PG) model, which is based on Western ideas of regular meter. The African-based TLG model with at most minor adjustment provided an excellent fit for seven of eight experimental conditions; one condition achieved a good fit only after more substantial modification of the model. The African TLG model achieved superiority over the Western PG model only under certain specific conditions, suggesting that the use of the African cognitive model is subtle, context-dependent, and linked to specific training regimes.