recognising and following the beat in a piece of music. We can even continue to
play the beat in our minds once a song has finished. However, despite the ease
with which we carry out such a task, the brain activity which underpins it
remains a topic of investigation.
the beat – why does it matter?
the niggling irritation of a song that’s stuck in our heads. However, few of us
are aware that our knack for holding a beat in our thoughts actually makes life
easier. The capacity to identify patterns in streams of sound supports many
forms of human behaviour, including moving, speaking and listening.
this internal rhythm is disrupted, such as in Parkinson’s disease, problems
begin to arise. People with Parkinson’s disease have difficulty with
psychological tasks, such as holding a beat in their minds, as well as with
practical tasks, such as walking. The more we know about the regions of the
brain that are causing these difficulties, the more effective we will be in
designing treatments to combat them. Previous research suggests that a set of
brain structures known as the basal ganglia are involved in identifying and
following a beat.
are the basal ganglia?
network of brain regions that are involved in movement and action. Many of the regions
within the basal ganglia appear to play a role in the processing of rhythm. One
such region is the putamen, a round structure near the centre of the brain.
Studies measuring levels of brain activity have found that the putamen is
active when a person is listening to a beat. However, it is not clear whether
the putamen is merely identifying the presence of the beat, or whether it is
actually helping us to recreate that beat in our minds.
can we tell what the putamen is doing?
designed a study which allowed them to distinguish between these two
possibilities. They began their work by creating small snippets of sound. Some
of the sound-bites contained a beat, while others did not. These ‘non beat’
sound-bites involved sounds which were not arranged in any rhythmic order. The
researchers then combined the order of the sound-bites to create different sequences.
These sequences fell into one of four key groups: (1) no beat, (sequences with
no beat present), (2) new beat, (sequences in which participants heard a non
beat followed by a beat), (3) beat continuation, (sequences with two versions
of the same beat), and
(sequences where the original beat got faster or slower).
participants to listen to the different sequences whilst a scanner measured how
their brain responded. In order to measure this brain activity, they used
functional magnetic resonance imaging, often know as fMRI. This is a form of
brain imaging that allows us to see which regions of the brain are involved in
which tasks. It does this by measuring the amount of oxygen that a specific
brain region is using relative to other regions. If a region is using a lot of oxygen,
it suggests that the region is ‘active’, that is, it’s involved in carrying out
did the researchers find?
putamen responded differently to different beat sequences. When there was no
beat, the putamen wasn’t active. Similarly, when participants heard a new beat,
the putamen didn’t respond. By contrast, when participants heard the same beat
twice, the putamen was highly active. It was also active, but to a lesser
extent, when the sequence involved the same beat played at different speeds.
the putamen was not responding to the presence of a beat per se, but was processing
the continuation of the beat across the sequence. This supports the theory that
the putamen is involved in our ability to recreate a beat in our minds.
is this important?
researchers knew that the putamen was related to beat processing, but they
didn’t know what its specific role was. This study showed that the putamen is
important for the mental generation of a beat.
our knowledge of the putamen’s role in beat processing, these findings have
notable clinical implications. People with Parkinson’s disease are capable of
identifying a beat in a piece of music, but have difficulty when it comes to
reproducing the beat in their own minds. The research shows that this pattern
of symptoms could be caused by damage to the putamen. Consequently, it
highlights the necessity of focusing on the putamen as a target for future
treatment of Parkinson’s disease.