i have just lost my husband and will not have time or inclination to post for a while. I will be back in a a few months.
Brain waves are measured for many reasons and they have been linked to various brain activities. But very little is known about how they arise. Are they the result or the cause of the activities they are associated with? How exactly are they produced at a cellular or network level? We know little about these waves.
One type of wave, beta waves (18-25 Hz) are associated with consciousness and alertness. In the motor cortex they are found when muscle contractions are isotonic (contractions that do not produce movement) but are absent just prior and during movement. They are increased during sensory feedback to static motor control and when movement is resisted or voluntarily suppressed. In the frontal cortex the beta waves are found during attention to cognitive tasks directed to the outside world. They are found in alert attentive states, problem solving, judgment, decision making, and concentration. The more involved the cognitive activity the faster the beta waves.
ScienceDaily reports a press release from Brown University on the work of Stephanie Jones and team, who are attempting to understand how beta waves arise. (here) Three types of study are used: MEG recordings, computer models, and implanted electrodes in animals.
The MEG recordings from the somatosensory cortex (sense of touch) and the inferior frontal cortex (higher cognition) showed a very distinct form for the beta waves, “they lasted at most a mere 150 milliseconds and had a characteristic wave shape, featuring a large, steep valley in the middle of the wave.” This wave form was recreated in a computer model of the layers of the cortex. “They found that they could closely replicate the shape of the beta waves in the model by delivering two kinds of excitatory synaptic stimulation to distinct layers in the cortical columns of cells: one that was weak and broad in duration to the lower layers, contacting spiny dendrites on the pyramidal neurons close to the cell body; and another that was stronger and briefer, lasting 50 milliseconds (i.e., one beta period), to the upper layers, contacting dendrites farther away from the cell body. The strong distal drive created the valley in the waveform that determined the beta frequency. Meanwhile they tried to model other hypotheses about how beta waves emerge, but found those unsuccessful.” The model was tested in mice and rhesus monkeys with implanted electrodes and was supported.
Where do the signals come from that drive the pyramidal neurons? The thalamus is a reasonable guess at the source. Thalamo-cortex-thalamus feedback loop makes those very contacts of the thalamus axons within the cortex layers. The thalamus is known to have signals with 50 millisecond duration. All of the sensory and motor information that enters the cortex (except smell) comes though the thalamus. It regulates consciousness, alertness and sleep. It is involved in processing sensory input and voluntary motor control. It has a hand in language and some types of memory.
The team is continuing their study. “With a new biophysical theory of how the waves emerge, the researchers hope the field can now investigate beta rhythms affect or merely reflect behavior and disease. Jones’s team in collaboration with Professor of neuroscience Christopher Moore at Brown is now testing predictions from the theory that beta may decrease sensory or motor information processing functions in the brain. New hypotheses are that the inputs that create beta may also stimulate inhibitory neurons in the top layers of the cortex, or that they may may saturate the activity of the pyramidal neurons, thereby reducing their ability to process information; or that the thalamic bursts that give rise to beta occupy the thalamus to the point where it doesn’t pass information along to the cortex.”
It seems very clear that understanding of overall brain function will depend on understanding the events at a cellular/circuit level; and that those processes in the cortex will not be understood without including other regions like the thalamus in the models.
A post in Science of Us in Feb, by Christian Jarrett, reviews the Libet experiment and recent attempts to overturn the implications of it. (http://nymag/scienceofus/2016/02/a-neuroscience-finding-on-free-will.html ) I find the struggle to reverse Libet’s finding to be the result of a mistaken way of viewing thought. An enormous amount of effort has gone into failed attempts to show this experiment was flawed over the last 30 years. Why are the implications so hard for people to accept?
Here is the first bit of Jarrett’s article (underlining is mine).
“Back in the 1980s, the American scientist Benjamin Libet made a surprising discovery that appeared to rock the foundations of what it means to be human. He recorded people’s brain waves as they made spontaneous finger movements while looking at a clock, with the participants telling researchers the time at which they decided to waggle their fingers. Libet’s revolutionary finding was that the timing of these conscious decisions was consistently preceded by several hundred milliseconds of background preparatory brain activity (known technically as “the readiness potential”).
The implication was that the decision to move was made nonconsciously, and that the subjective feeling of having made this decision is tagged on afterward. In other words, the results implied that free will as we know it is an illusion — after all, how can our conscious decisions be truly free if they come after the brain has already started preparing for them?
For years, various research teams have tried to pick holes in Libet’s original research. It’s been pointed out, for example, that it’s pretty tricky for people to accurately report the time that they made their conscious decision. But, until recently, the broad implications of the finding have weathered these criticisms, at least in the eyes of many hard-nosed neuroscientists, and over the last decade or so his basic result has been replicated and built upon with ever more advanced methods such as fMRI and the direct recording of neuronal activity using implanted electrodes.
These studies all point in the same, troubling direction: We don’t really have free will. In fact, until recently, many neuroscientists would have said any decision you made was not truly free but actually determined by neural processes outside of your conscious control.”
That is the stumbling block: ‘neural processes outside of conscious control’. That is what some scientists are fighting so hard not to lose. The whole notion of what free will is rests on how we view who we are, what our consciousness is, and how control works.
When we think of who we are, we cannot separate self from non-self within our bodies. We are not really divided at the neck, or between the upper and lower parts of the brain, or between different ‘minds’ co-existing in one skull. This idea of two separate minds, that was inherited from Freud and others, has not been demonstrated to be true. It has not been shown that we have two distinct thinking minds that are somehow separate. Thinking appears to be a complex, widespread but interconnected and unified affair. Whether a particular thought process becomes conscious or remains non-conscious does not depend on the basic process of thought.
There is every reason to reject the notion of a separate conscious mind that thinks in a ‘conscious’ manner to produce conscious thoughts. We are aware of thoughts (some thoughts) but we are not aware of the mechanisms that produced the thoughts. We do not metaphorically hear the gears of thought production grinding. We are simply not aware of how thought happens. Consciousness is a form of awareness and probably not much more. There is awareness of some things that go on in the brain but not of all things or even the bulk of things.
So why are some thoughts made conscious while others aren’t? A good guess is that consciousness gives a remembered experience, an episodic memory, or at least the material for such memories. With memories of our actions, it would be important information to remember whether the action was our doing or just happened to us, whether it was accidental or intended, whether it was a choice or coerced, carefully planned or an automatic habit and so on. These pieces of information are important to save and so would be incorporated into conscious events. We need that information to learn from experience. Just because the feeling of having an intent, an urge and then an execution of an action is there in our conscious awareness does not mean that they were a form of conscious control. They are there as important parts of the event that consciousness is recording.
We can still control our actions, and we still can be aware of controlling our actions, but that does not mean that our awareness is producing the control that we are aware of. Consciousness does not produce the tree that I am aware of – it just produces the awareness. And you are just you, and not your awareness of you. There is reality and there are models of reality; there is territory and there are maps of the territory; there is an original and there are copies of the original. There is you and there is your awareness of you. You make decisions (with neural activity) but your awareness of a decisions is not the same as making it.
I personally find it a little difficult to understand why this idea of a conscious mind as opposed to a conscious awareness is so strong and indestructible an idea to most people. I cannot remember exactly how or when (it was a gradual process) but some time in my late teens, over 50 years ago, my consciousness became a flickering imperfect movie screen and not a thinking mind. So “determined by neural processes outside of conscious control” is obvious because there is no such thing as conscious control and what is more, it is a comforting rather than alarming viewpoint.
I am assuming that the current experiments with showing ‘free won’t’ will not turn out to be any more robust than the attempts to show free will. We shall see.