A new paper studied if the excitability of the motor cortex correlates with working memory performance – and results were positive. 

By measuring the motor excitability, conclusions can be drawn as to general cortical excitability – as well as to cognitive performance, say the scholars from the Transfacultary Research Platform at the University of Basel.

Working memory allows the temporary storage of information such as memorizing a phone number for a short period of time. Studies in animals have shown that working memory processes among others depend on the excitability of neurons in the prefrontal cortex. There is some evidence that motor neuronal excitability might be related to the neuronal excitability of other cortical regions. 

Measuring of the motor excitability with transcranial magnetic stimulation. Credit and link: Cognitive Neuroscience, University of Basel

"The motor cortical excitability can be easily studied with transcranial magnetic stimulation," says Nathalie Schicktanz, doctoral student and first author of the study. During this procedure, electromagnetic impulses with increasing intensity are applied over the motor cortex. For subjects with high motor excitability already weak impulses are sufficient to trigger certain muscles – such as those of the hand – to show a visible twitch.

The results from 188 college students found that subjects with a high motor excitability had increased working memory performance as compared to subjects with a low excitability. "By measuring the excitability of the motor cortex, conclusions can be drawn as to the excitability of other cortical areas," says Schicktanz.

Since working memory deficits may be a component of many neuropsychiatric disorders, such as schizophrenia or attention deficit hyperactivity disorder, they next plan to study the relation between neuronal excitability and memory on a molecular level.

Citation: Nathalie Schicktanz, Kyrill Schwegler, Matthias Fastenrath, Klara Spalek, Annette Milnik, Andreas Papassotiropoulos, Thomas Nyffeler&Dominique J.-F. de Quervain, 'Motor threshold predicts working memory performance in healthy humans', Annals of Clinical and Translational Neurology, 2013, DOI: 10.1002/acn3.22