Abstract
While the preparatory neural mechanisms of real and imagined body movements have been extensively studied, the underpinnings of self‑initiated, voluntary mental acts are largely unknown. Therefore, using electroencephalography (EEG), we studied the time course and patterns of changes in brain activity associated with purely mental processes which start on their own, without an external or interoceptive stimulation. We compared EEG recordings for decisions to perform mental operations on numbers, imagined finger movements, and actual finger movements. In all three cases, we found striking similarities in slow negative shifts of brain electrical activity lasting around 1 s and, therefore, characteristic for readiness potential. These results show that the brain not only needs time to be ready for a purely mental task but also that a required preparatory interval involves neural changes analogical to the ones observed before intentional body movements. As such, the readiness potential represents a universal process of unconscious preparatory brain activity preceding any, including purely mental, voluntary action.
Highlights
Imagine that you are a skillful crossword puzzle solver and have just bought your favorite new brain teaser
The overall signal changes observed for mental actions were similar to the ones observed for imag‐ ined finger movements
Even though the movements were imagined or performed with the dominant hand, the readiness potential signals regis‐ tered on electrodes in the vicinity of Cz were barely lateralized to any of the hemispheres, except for some subtle effects observed in the very late phase of prepa‐ ratory activity for imagined finger movements
Summary
Imagine that you are a skillful crossword puzzle solver and have just bought your favorite new brain teaser. Its aim is not to find out what is happening in the immediate surroundings but to set the mind in motion to produce a purely mental result. This find‐ ing can later be expressed verbally but it is only an announcement of a previous solution. Such an an‐ nouncement is completely different from, for example, an “intention to move” because the effect of the latter is a real or imagined movement (expressed either as co‐ vert or overt bodily change), not a purely mental result
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