What is the intention to move and when does it occur?

Abstract

In 1983 Benjamin Libet and colleagues published a paper apparently challenging the view that the conscious intention to move precedes the brain's preparation for movement. The experiment initiated debates about the nature of intention, the neurophysiology of movement, and philosophical and legal understanding of free will and moral responsibility. Here we review the concept of "conscious intention" and attempts to measure its timing. Scalp electroencephalographic activity prior to movement, the Bereitschaftspotential, clearly begins prior to the reported onset of conscious intent. However, the interpretation of this finding remains controversial. Numerous studies show that the Libet method for determining intent, W time, is not accurate and may be misleading. We conclude that intention has many different aspects, and although we now understand much more about how the brain makes movements, identifying the time of conscious intention is still elusive.

Keywords: Bereitschaftspotential; Consciousness; Free will; Intention; Movement; Readiness potential.

Fig. 1.

1. The time of the onset of the brain state of a proximal intention (or proximal wanting); 1b. The time participants report as time 1; 1c. The time at which participants make this report; 2. The onset of the movement; 2a. The time at which participants become conscious of having moved; 2b. The time participants report as time 2; 2c. The time at which participants make this report.Time 1a, i.e., the time at which participants become conscious of a proximal intention, is the topic of this review, and it is not present in the graph, being unknown.

Fig. 2.

Examples of different BPs during a W session.