Benjamin Libet (born 1916) is a researcher in the physiology department of the University of California, San Fransisco, and a pioneering scientist in the field of human consciousness. 1916 (MCMXVI) is a leap year starting on Saturday (link will take you to calendar) // Events January-February January 1 - The Royal Army Medical Corps first successful blood transfusion using blood that had been stored and cooled. ... Physiology (in Greek physis = nature and logos = word) is the study of the mechanical, physical, and biochemical functions of living organisms. ... The University of California (UC) is a public university system in the state of California. ... This article is about the city in California. ... Consciousness is a quality of the mind generally regarded to comprise such key features as subjectivity, self-awareness, sentience, sapience, and the ability to perceive the relationship between oneself and ones environment. ...

In the 1970s, Libet was involved in research into neural activity and sensation thresholds. His initial investigations involved determining how much activation at specific sites in the brain was required to trigger artificial somatic sensations, relying on routine psychophysical procedures. This work soon crossed into an investigation into human consciousness; his most famous and controversial experiment demonstrates that unconscious electrical processes in the brain (called 'readiness potential') precede conscious decisions to perform volitional, spontaneous acts, implying that unconcious neuronal processes precede and potentially cause volitional acts which are retrospectively felt to be consciously motivated by the subject. The 1970s decade refers to the years from 1970 to 1979, inclusive. ... The nervous system of an animal coordinates the activity of the muscles, monitors the organs, constructs and processes input from the senses, and initiates actions. ... The term somatic refers to the body. ... Psychophysics is the branch of psychology dealing with the relationship between physical stimuli and their perception. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Volition is the study of will, choice, and decision. ... The unconscious mind (or subconscious) is more than simply the aspect or aspects of the mind of which we are not directly conscious or aware. ...

Volitional acts and readiness potential

Equipment and methodology

In order to gauge the relationship between unconscious readiness potential ('RP') and subjective feelings of volition and action, Libet required an objective method of marking the subject's conscious experience of the will to perform an action in time, and afterward comparing this information with data recording the brain's electrical activity during the same interval. For this, Libet required specialized pieces of equipment. The first of these was the cathode ray oscilloscope, an instrument typically used to graph the amplitude and frequency of sound waves. With a few adjustments, however, the oscilloscope could be made to act as a timer: instead of displaying a series of waves, the output was a single dot that could be made to travel in a circular motion, similar to the movements of a second hand around a clock face. This timer was set so that the time it took for the dot to travel between intervals marked on the oscilloscope was approximately forty-three milliseconds. As the angular velocity of the dot remained constant, any change in distance could easily be converted into the time it took to travel that distance. Template:Wiktionarypar objective Objective may be: Objective lens, an optical element in a camera or microscope. ... A schematic diagram of a Crookes tube apparatus. ... A Tektronix model 475A portable analogue oscilloscope, a very typical instrument of the late 1970s. ... Amplitude is a nonnegative scalar measure of a waves magnitude of oscillation, that is, magnitude of the maximum disturbance in the medium during one wave cycle. ... Sine waves of various frequencies; the lower waves have higher frequencies than those above. ... A millisecond is an SI-derived unit of time, equal to one thousandth of a second. ...

To monitor brain activity during the same period, Libet used an electroencephalogram, or EEG. Developed in 1936 by British scientist Walter Grey Walter and inspired by work performed in 1929 by German psychologist Hans Berger, the EEG uses small electrodes placed at various points on the scalp that measure neuronal activity in the cortex, the outermost portion of the brain, which is associated with higher cognition. The transmission of electrical signals across regions of the cortex causes differences in measured voltage across EEG electrodes. These differences in voltage reflect changes in neuronal activity in specific areas of the cortex. Electroencephalography is the neurophysiologic exploration of the electrical activity of the brain by the application of electrodes to the scalp. ... 1936 (MCMXXXVI) was a leap year starting on Wednesday (link will take you to calendar). ... // His life W. Grey Walter February 19, 1910 - May 6, 1977 was born in Kansas City, Missouri, in 1910. ... 1929 (MCMXXIX) was a common year starting on Tuesday (link will take you to calendar). ... A psychologist is a scientist who studies psychology, the systematic investigation of the human behaviour and mental processes. ... Hans Berger was born in May 21, 1873, in Neuses near Coburg, Thuringia, Germany. ... Alternative meanings: There is also an Electric-type Pokémon named Electrode. ... Cortex (Latin for bark) has different meanings, depending on the context: In neuroanatomy: the cerebral cortex (often simply called cortex) is the thin wrinkled outermost layer of the brain. ... Comparative brain sizes In animals, the brain, or encephalon (Greek for in the head), is the control center of the central nervous system. ... Look up Cognition in Wiktionary, the free dictionary The term cognition (Latin, cogito: to think) is used in several different loosely related ways. ...

Researchers carrying out Libet’s procedure would ask each participant to sit at a desk in front of the oscilloscope timer. They would affix the EEG electrodes to the participant’s scalp, and would then instruct the subject to carry out some small, simple motor activity, such as pressing a button, or flexing a finger or wrist, within a certain time frame. No limits were placed on the number of times the subject could perform the action within this period. During the experiment, the subject would be asked to note the position of the dot on the oscilloscope timer when "he/she was first aware of the wish or urge to act" (control tests with Libet's equipment demonstrated a comfortable margin of error of only -50 milliseconds). Pressing the button also recorded the position of the dot on the oscillator, this time electronically. By comparing the marked time of the button's pushing and the subject's conscious decision to act, researchers were able to calculate the total time of the trial from the subject's initial volition through to the resultant action. On average, approximately two hundred milliseconds elapsed between the first appearance of conscious will to press the button and the act of pressing it. The top portion of this graphic depicts probability densities that show the relative likelihood that the true percentage is in a particular area given a reported percentage of 50 percent. ...

Researchers also analyzed EEG recordings for each trial with respect to the timing of the action. It was noted that brain activity involved in the initiation of the action, primarily centered in the secondary motor cortex, occurred, on average, approximately five hundred milliseconds before the trial ended with the pushing of the button. That is to say, researchers recorded mounting brain activity related to the resultant action as many as three hundred milliseconds before subjects reported the first awareness of conscious will to act. In other words, apparently conscious decisions to act were preceded by an unconscious buildup of electrical charge within the brain - this buildup came to be called Bereitschaftspotential or readiness potential. // Early work on motor cortex function Back in the 1940s, Canadian neurosurgeon Wilder Penfield wanted to know which bits of epileptics brains he could suck out without them noticing. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...

The implications of Libet's experiments

If unconscious processes in the brain are the true initiator of volitional acts, as Libet's experiments suggest, then little room remains for the operations of free will. If the brain has already taken steps to initiate an action before we are aware of any desire to perform it, the causal role of consciousness in volition is all but eliminated. Free will is the philosophical doctrine that holds that our choices are ultimately up to ourselves. ...

Libet himself finds room for free will in the interpretation of his results, but in a massively reduced role to that which we are used to. This is in the form of 'the power of veto', in which conscious acquiescence is required to allow the unconscious buildup of RP to be actualised as a movement. Thus, while consciousness plays no part in the instigation of volitional acts, it retains a part to play in the form of suppressing or withholding from certain acts instigated by the unconscious. Certainly, as Libet notes, we have all experienced the withholding from performing an unconscious urge. If it is recalled that the subjective experience of the conscious will to act preceded the action by only 200 milliseconds, this leaves consciousness only 100-150 milliseconds to veto an action (this is because the final 50 milliseconds prior to an act are occupied by the activation of the spinal motor neurones by the primary motor cortex, plus the margin of error indicated by tests utilising the oscillator must also be considered). However, such a role for free will remains speculative, and one must acknowledge the fact that Libet's investigations imply an ultimately unconscious basis for human action. For further discussions of Libet's findings with regard to free will, see Michael Pauen, "Does Free Will Arise Freely?" in Scientific American Mind, Volume 14, Number 1: 2004. Look up spine on Wiktionary, the free dictionary. ...

It has been suggested that consciousness is merely a side-effect of neuronal functions, an epiphenomenon of brain states. On the face of it, Libet's experiments offer support to this theory; our reports of conscious instigation of our own acts is, arguably, a mistake of retrospection. However, for consciousness to be reduced to brain states, Leibniz's law would have to be observed; that is, for A to be the same as B, the properties of A must be the same as the properties of B. An epiphenomenon is a secondary phenomenon that occurs alongside a primary phenomenon. ... The identity of indiscernibles is an ontological principle that states that if there is no way of telling two entities apart then they are one and the same entity. ...

Phenomenally speaking, the properties of consciousness are entirely unlike the properties of either its neural causes or correlates. Reducing consciousness to being simply a brain state is fraught with philosophical difficulty:

"in short, the [neuronal] causes and correlates of conscious experience should not be confused with their ontology [...] the only evidence about what conscious experiences are like comes from first-person sources, which consistently suggest consciousness to be something other than or additional to neuronal activity" (Max Velmans, Understanding Consciousness, Routledge, London, 2000: 35-37; emphases author's own).

Thus the ramifications of Libet's experiments remain a point of philosophical contention. Ontology (from the [Greek on, ontos being, existence + logia <logos word, study]) is the philosophical science of reality. ... Max Velmans is a Professor of Psychology at Goldsmiths College, University of London. ... Routledge is an imprint for books in the humanities part of the Taylor & Francis Group, which also has Brunner-Routledge, RoutledgeCurzon and RoutledgeFalmer divisions. ... The Houses of Parliament and the clock tower containing Big Ben Part of the London skyline viewed from the South Bank London (see Wiktionary:London for the name in other languages) is the capital of the United Kingdom and England. ... This article is about the year 2000. ...