How does our brain respond when we perceive a beat?
Stimuli
These stimuli were used in a rhythm reproduction task (people listening to a rhythm and then tapping that rhythm back on a computer keyboard) and an fMRI discrimination task. (listening to 2 rhythms and indicating if the second was different from or the same as the first). (Grahn and Brett, 2007)
The metric simple and complex rhythms are composed of intervals related by integer-ratios (1:2:3:4), whereas nonmetric use noninteger-ratios (1:1.4:3.5:4.5).
The metric simple rhythms also have a regular grouping which induces a stronger perception of a beat than in the metric complex rhythms. As the behavioural data show below, integer-ratios are not enough to lead to better rhythm performance--regular grouping is also required.
Stimuli
These stimuli were used in a rhythm reproduction task (people listening to a rhythm and then tapping that rhythm back on a computer keyboard) and an fMRI discrimination task. (listening to 2 rhythms and indicating if the second was different from or the same as the first). (Grahn and Brett, 2007)
The metric simple and complex rhythms are composed of intervals related by integer-ratios (1:2:3:4), whereas nonmetric use noninteger-ratios (1:1.4:3.5:4.5).
The metric simple rhythms also have a regular grouping which induces a stronger perception of a beat than in the metric complex rhythms. As the behavioural data show below, integer-ratios are not enough to lead to better rhythm performance--regular grouping is also required.
The rhythms

To listen to the sounds, click each of the names below:
Reproducing metric simple rhythms was most accurate.

For the reproduction task, participants heard each rhythm 3 times, then tapped back what they heard on a computer keyboard.
As you can see from the graph on the left, the metric simple rhythms are remembered correctly significantly more often than the other two types.
This pattern has been replicated with rhythms made with brief percussion noises (rather than longer sine tones).
For the fMRI study, participants performed a rhythm discrimination task. They listened to 3 presentations of a rhythm, and had to decide if the third presentation was the same as or different from the first 2 presentations of that rhythm.
A sample trial (decide if the third presentation is different from the first two)
We measured brain activity when participants were hearing the first 2 presentations (we only measured activity related to listening and trying to remember rhythms, not activity related to discriminating the change, so the third presentation was ignored).
As you can see from the graph on the left, the metric simple rhythms are remembered correctly significantly more often than the other two types.
This pattern has been replicated with rhythms made with brief percussion noises (rather than longer sine tones).
For the fMRI study, participants performed a rhythm discrimination task. They listened to 3 presentations of a rhythm, and had to decide if the third presentation was the same as or different from the first 2 presentations of that rhythm.
A sample trial (decide if the third presentation is different from the first two)
We measured brain activity when participants were hearing the first 2 presentations (we only measured activity related to listening and trying to remember rhythms, not activity related to discriminating the change, so the third presentation was ignored).
Neuroimaging results

This picture shows greater activity in the basal ganglia to metric simple rhythms compared to the other two types. This suggests the basal ganglia play a role in beat perception.
All the areas that responded to 'the beat'

This graph shows relative activity to the three rhythm types.
Significantly greater activity is observed for the metric simple condition than the other two conditions in the basal ganglia, supplementary motor area, and superior temporal gyri (auditory cortex).
Significantly greater activity is observed for the metric simple condition than the other two conditions in the basal ganglia, supplementary motor area, and superior temporal gyri (auditory cortex).