Libet

Question 1

Libet and the relative timing of conscious willing and overt action

Answer 1

Since 1960 it has been clear that the “readiness potential” (RP) precedes voluntary movements. The readiness potential stands for a negative charge in the electrical potential that can be measured with electrodes applied to the skull before performing any actions. He could easily perceive the beginning of the movement and the beginning of the RP. Interestingly, he found out that the conscious choice to move arises after the RP. These results seem to say that consciousness comes too late to be the cause of the movement. Libet stated that unconscious brain processesare the cause of a voluntary movement, but consciousness can (just before the voluntary movement is performed) stop this or not. This would occur approximately 150 ms before the movement execution. In this way, Libet argued that consciousness nevertheless has a causal role in voluntary actions

Question 2

Libet and the relative timing of conscious willing and overt action kritiek

Answer 2

doubts about the method of measuring the will, doubts about the method of backwards referral, and it has been suggested by some researchers that awareness of one’s own actions is associated with events after the intention and preparation, but before the motor command is sent

Question 3

Libet’s stimulation of the brain of patients

Answer 3

Libet conducted experiments showing that there must be about half a second of neural activity to induce consciousness. This is also called “half-second delay”. During his experiments, he stimulated the sensory cortex of people who were awake and aware. Their somatosensory cortex was stimulated with electrodes. This stimulation always differed in frequency, intensity and duration. As a result, the participants stated that they had conscious sensory perceptions.Libet discovered the relationship between the intensity of the stimulation and how long the sensory experience lasts. He stated that a certain amount of intensity is required for sensory perception. If this degree is not reached, no perception would occur, however long a part of the brain was stimulated. He found that the stimulation must last at least half a second to take effect. It is also said that the “train duration” should last atleast half a second. Libet also concluded that only the somatosensory cortex itself can provide conscious perception