The millisecond precision planning of the brain

Bielefeld researchers demonstrate how humans control grip

What takes place in the brain when humans grip objects? Until now, there has been little research on this question. Neuroscientists studying movement at Bielefeld University have now ascertained how long the brain needs to plan a precision movement. The answer: The brain needs just about half a second from the planning of the movement to its completion. The researchers published their findings in the science journal PLOS ONE on Tuesday (1.4.2014).

According to the researchers, the way humans grip objects has mainly been researched by just studying behaviour: How do humans move their arms and fingers to grip an object? And how long do they need on average to carry out a gripping movement? There has been no research, the researchers say, on what takes place inside the brain up until now, as it was assumed that the muscle activity in the hands would distort the brain waves. ‘In our study we factored these distortions out’, says Dr. Dirk Koester of the research group Neurocognition and Action – Biomechanics of the Centre of Excellence CITEC of Bielefeld University.

20 people took part in the study. They had the task of holding a rod that was mounted on a rotatable disc, and were asked to turn one of its ends to one of eight targets around the edge. ‘This is an open gripping movement which we make, for example, when we put a coffee cup into the cup holder of a car,’ explains Koester. There is a need for high precision at the end of a movement such as this. ‘We have to position it precisely so that we can let it finally slide into the holder’, says Koester. In the experiment, the precision movement was to align the ‘pointer’ to one of the targets.

The research team wanted to find out when the preplanning for the precision movement began and how long it lasted. ‘Our measurements show that the preplanning begins 600 milliseconds before the movement ends – which is just over half a second. Our brain is still absorbed in the gripping movement for 200 milliseconds more after the target has been reached. It needs this time to make sure that the movement has been carried out correctly and whether it needs to be corrected,’ says Professor Thomas Schack, head of the Research Group Neurocognition and Action – Biomechanics.

According to Schack, the Bielefeld research studies could, for instance, be used for medical examinations of patients with Parkinson’s disease. ‘Using these methods we can compare, for example, if the brain of a patient needs the same amount of planning time as a healthy brain to move objects precisely.’ The results of this study can also be of use to robotics researchers working at the Cluster of Excellence CITEC. ‘If you want to achieve optimal communication between humans and robots, then mechanisms of the human brain such as these can be technically reproduced in robots.’

With its latest study, the research team has proven how much gripping movements place demands on working memory. In an earlier study, the researchers discovered that the replanning of movements makes demands on both spatial and verbal working memory. ‘This means that the planning of current actions makes demands on the corresponding resources and influences other cognition and motor processes,’ says Schack. ‘This can have life-threatening implications. ‘Someone reaching for their mobile phone or reaching for their coffee cup whilst driving could have difficulties in critical traffic situations because they can’t react quickly enough to swerve out of the way, for instance.’

Original publication:
Jan Westerholz, Thomas Schack, Christoph Schütz, Dirk Koester: Habitual vs. Non- Habitual Manual Actions: An ERP Study on Overt Movement Execution. PLOS ONE,
http://dx.doi.org/10.1371/journal.pone.0093116, published on 1 April 2014.

Contact:
Dr. Dirk Koester, Bielefeld University
Cluster of Excellence Cognitive Interaction Technology (CITEC)
Telephone: +49 (0)521 106 2420
Email:dirk.joester@uni-bielefeld.de