Basic timekeeping deficit in the Beat-based Form of Congenital Amusia

Humans have the capacity to match movements' timing with the beat of music. Yet some individuals show marked difficulties. The causes of these difficulties remain to be determined. Here, we investigate to what extend a beat synchronization deficit can be traced to basic timekeeping abilities. Eight beat-impaired individuals who were unable to successfully synchronize to the beat of music were compared to matched controls in their ability to tap a self-paced regular beat, to tap to a metronome spanning a large range of tempi (225-1709 ms inter-tone onsets), and to maintain the tempi after the sounds had ceased. Whether paced by a metronome or not, beat-impaired individuals showed poorer regularity (higher variability) in tapping, with an inability to synchronize at a fast tempo (225 ms between beats) or to sustain tapping at slow tempi (above 1 sec). Yet, they showed evidence of predictive and flexible processing. We suggest that the beat impairment is due to imprecise internal timekeeping mechanism.