Beyond pitch: temporal processing deficits in congenital amusia

Congenital amusia is a neurodevelopmental disorder resulting in impaired pitch perception and memory. Here we investigated whether participants with congenital amusia have deficits in temporal processing of auditory information, in addition to pitch processing deficits. Individuals with amusia (n = 19) and matched controls (n = 21) were presented with sequences of five tones in which one tone was sometimes shifted in pitch or in time, and we adaptively assessed psychophysical thresholds for detecting these shifts. Pitch thresholds of the amusia group were higher (i.e., worse) than those of the control group as expected, and, crucially, time thresholds were too, although the group difference for time thresholds was smaller. Across participants, time thresholds correlated with pitch thresholds. Principal component analysis revealed that all pitch- and time-related variables (thresholds and amusia battery scores) were correlated to one component that also distinguished between amusics and controls; whereas a second component captured additional variability on the time task. Simulations suggest that prior studies had not found these time processing deficits because they had less statistical power, likely due to smaller sample sizes. The observed time processing deficit is in agreement with amusic individuals' subjective reports about their difficulties following the rhythm of the music. These data suggest that amusia deficits are not restricted to pitch, but extend to the time domain, yet with a smaller effect size, and at least when the stimuli have a clear pitch content, such as for tone sequences or music.