Beat finding versus beat prediction
Example stimulus sound that participants heard during brain scanning.
In the auditory domain, perception of a regular pulse, or beat, within a sequence of temporal intervals is associated with basal ganglia activity. Two alternative accounts of this activity are possible: searching for temporal regularity in early stimulus processing stages, or internal generation or prediction of the timing of future beats after the beat is already found.
To resolve between these different accounts, we used fMRI to investigate neural activity in different stages of beat perception. Participants listened to beat and non-beat (irregular) rhythms. For each beat rhythm, the preceding sequence provided a beat context for the following sequence. A beat sequence could be preceded by a non-beat sequence, requiring the beat to be found anew (‘beat-finding’ condition), or could be preceded by a beat sequence with the same beat rate (‘beat-continuation'), or a different rate ('beat-adjustment').
We found the highest basal ganglia activity for beat-continuation trials, less for beat-adjustment trials, and the least for beat-finding trials. Other motor areas did not show this graded activation pattern. Thus, the basal ganglia responds after a beat has been found, suggesting they do not play a role in beat finding, but rather in beat generation.
You can also read the paper.
Activity during beat perception is found in the putamen (part of the basal ganglia).
The putamen responds less when a new beat has to be found (new condition), and more when the beat stays the same (same rate/same rhythm conditions).