June 18, 2006

Initiating Free Will

The Loom posted a very interesting article a few years back illustrating the one of the peculiarities of our brains. Yesterday I talked about the issue of free will on a quantum level... today I will talk about free will in less abstract terms.

In 1970s and 80s, a neuroscientist from UCSF conducted experiments to test the boundaries of consciousness. In 1983, Benjamin Libet published a paper entitled "Time of Conscious Intention to Act in Relation to Onset of Cerebral Activity (Readiness Potential)".

This experiment measured brain activity with an electroencephalogram (EEG) as the subjects pushed a button. The subjects noted each time they wanted to push the button based on the clock position of a dot on a modified oscilloscope. The average reaction time between the intention of pushing the button and actually pushing it was ~350 milliseconds with a minimum of ~150 ms. The EEG measured brain activity in the secondary motor cortex and noted that the subjects recorded brain activity ~500 ms before the button was pushed.

What does this mean? Libet's team suggested that the brain was preparing for action before the subjects even decided to push the button by as much as 350 ms. We are acting before we are even aware of our actions... the primary buildup in the motor cortex (readiness potential) was unconsciously driving the action. Libet felt that the role of the conscious brain is primarily inhibitive... we've all felt those moments when we had urges to do something that we strove to hold back. This inner control over our visceral impulses defines free will. After the brain ticks away and neurons are already firing to activate the muscles to push the button, the conscious brain decides to resist or comply.

The Loom talked about another followup experiment for the anniversary of Libet's experiment:
"... a team of European neuroscientists published a fitting tribute to Libet... They ran Libet's experiment again, but some of the people they chose as their subjects had damage to certain parts of the brain. As they report in Nature Neuroscience, some kinds of brain damage make no difference to people's performance. But something fascinating happened to people who suffered damage to the parietal cortex, located at the back of the head. Like the healthy controls, they could nail the moment they actually pressed the button, to within a few milliseconds. But they also noted that they intended to press the button just around the time they actually did press the button. In other words, they were completely unconscious of their action until the action was already taking place."
I found another example of how free will, awareness, and unconscious behavior play a role in our own actions:
Humans have the conscious experience of 'free will': we feel we can generate our actions, and thus affect our environment. Here we used the perceived time of intentional actions and of their sensory consequences as a means to study consciousness of action. These perceived times were attracted together in conscious awareness, so that subjects perceived voluntary movements as occurring later and their sensory consequences as occurring earlier than they actually did. Comparable involuntary movements caused by magnetic brain stimulation reversed this attraction effect. We conclude that the CNS applies a specific neural mechanism to produce intentional binding of actions and their effects in conscious awareness.
These experiments provide a great deal of insight into the pathology of brain damage and psychoses. Damage to certain parts of the brain can disrupt the cortico-cortical sensorimotor processing loop. Paranoid schizophrenia is a mental disorder in which the normal process of free will/awareness and unconscious behavior gets disrupted. The central nervous system has a way of fooling the conscious brain into thinking that it is directing movement when in fact, it is just predicting the responses of what other parts of the brain are already doing.

We are under the illusion that our bodies are governed by a singular consciousness. This is true for the most part... not very many people can concentrate on two tasks at once or have more than one inner dialogue at once! The people who can function like this are considered unusual at best, crazy at worst.

Our brains are hardwired to believe in this "Oneitude." However, the truth of the matter is that we run parallel processors (the left and right hemisphere) and they function both independently and interdependently.

No comments:

Post a Comment