Sorry Steve, I forgot about the colors issue. Here's that post again with terms and claims that I think we should look at closely set in boldface type instead of being highlighted in red. In rereading my post and its embedded extract again, I've added the boldface signal to larger elements of the quoted extract and also added further comments at the end.
The original post is at this link:
Consciousness and the Paranormal — Part 10
'Following is an interesting extract from a 2017 report on current neuroscientific research under the title "Insights into how dopamine directs learning and new techniques for imaging and tracing cells were just some of the advances described at the third annual gathering of the Simons Collaboration on the Global Brain," linked at
Inner Workings of the Brain Explored at 2017 SCGB Annual Meeting | Simons Foundation
". . .Why don’t muscles move when we think about moving them?
When we think about reaching for a coffee cup, the motor cortex shows a pattern of neural activity similar to when we actually make the move. Why do similar activity patterns sometimes translate into movement and sometimes not?
Previous research suggests that neural activity patterns linked to movement are qualitatively different from those that aren’t. In mathematical terms, these patterns reside in different dimensions. In so-called ‘motor-potent’ dimensions, the linear combination of neuronal activity triggers a net output on muscle. In ‘motor-null’ dimensions, the summed activity essentially cancels itself out, having no effect on muscle.
Muscle service: Imagine a simplified system with two neurons driving a single muscle — the sum of their firing rates is a constant, say 20 spikes per second. When the firing rate for one neuron goes up, the other goes down. Individual neuronal activity can change, but the output to the muscle remains the same. The firing rates of these two neurons create a line that defines the motor-null dimension. In a more complex system of, say, 200 neurons, the line becomes a hyperplane. “When not driving the muscle, patterns of activity in motor cortex seem to live along this hyperplane,” Shenoy says. “Anything that doesn't fall on that output null hyperplane by definition does change activation of the muscle.” Credit: Krishna Shenoy
Motor-null dimensions may offer the motor cortex the ability to plan a movement before executing it. In new research, Krishna Shenoy, a neuroscientist at Stanford, and collaborators suggest that motor-null dimensions also help the motor cortex process new sensory information during movement planning. “We think of those null dimensions as a scratch pad where computations can happen,” Shenoy says.
If someone bumps your arm as you reach for a coffee cup, the brain processes that sensory information and adjusts the arm’s reach accordingly. But exactly how that happens is puzzling. Neural recordings have shown that sensory information itself can travel to the motor cortex very quickly, so how does the brain have enough time to act on it? Shenoy predicts that new sensory information briefly lingers in motor-null dimensions and then shifts to motor-potent dimensions, where it directs movement.
The researchers tested this hypothesis in monkeys implanted with a brain-machine interface (BMI), a device that records neural activity from roughly 200 neurons in the motor cortex and translates it into some kind of output. In this experiment, the monkeys learned to move a cursor on a computer screening using just their thoughts. On some trials, scientists made the cursor jump, mimicking someone getting bumped while reaching for coffee. The monkey then had to alter its thinking to correct the cursor’s movement.
Because the researchers are using a BMI, they know precisely how neural activity maps to the cursor’s movement and can clearly define motor-null and motor-potent dimensions. They first record neural activity and the location of a moving target on a screen, which the monkey is trained to plan to reach to. This generates natural motor cortical activity. They then fit a decode model to the neural and kinematic data, which defines a weight matrix that transforms the former into the latter. With the weight matrix in hand, they can then use standard linear algebra to define which dimensions are null and which are potent.
Shenoy’s team found that neural activity linked to the visual ‘bump’ did indeed exist in the motor-null dimension initially. After about 50 milliseconds, it morphed into the motor-potent dimension. “The data fall beautifully into those dimensions,” Shenoy says. The results suggest that the motor system performs computations locally before using that data to direct movement.
The researchers next plan to do that same experiment with monkeys trained to use a haptic robotic arm, which can detect tactile feedback. “Now that we can physically perturb the arm, we want to know if proprioceptive information also comes in to the null space first and to see how general this computational principle really is,” Shenoy says.
The researchers also want to apply the findings to their clinical work with people learning to use robotic arms. The software that translates brain activity into arm movement needs to know how to react if the robotic arm gets jostled. For example, the software needs to be able to distinguish motor cortex activity that is being processed in null dimensions from activity that is intended to drive arm movement. “We think that by understanding the null and potent dimensions, we can have people controlling robotic arms without the arm flailing around if it bumps into something,” Shenoy says."
I'm offering this extract for discussion if anyone is interested. I've underscored some of the questionable terms and speculative presuppositions that stand out for me in the extract and elsewhere in the Simons Foundation presentations at the link.'
ETA: Re the monkey experiment, how much does it actually explain about how the 'computational brain' assists physically compromised individuals who lack the ability to physically sense relevant aspects of their physical environments? It seems to me that it is not computation but consciousness that fills in the gaps. In other words, the brain does not produce consciousness but rather assists, enables consciousness in developing awareness of its situation and ability to cope with the conditions and demands of its situation.
In the text above concerning the monkey experiment, the experimenters interestingly go so far as to refer to what the monkeys "think": "The monkey then had to alter its thinking to correct the cursor’s movement." It's important to recognize that these experimenters believe that thinking goes on in what they call a "motor null dimension" of neural operations -- another way of claiming that it is our neurons that think, or as the Churchlands exquisitely expressed it, "we are our neurons."
It seems to me that evidentiary, empirical, support for this belief could only arise from ethically prohibited experiments that would place newborn infants in vats wearing life-sustaining but sensorially deprivational equipment/suits that effect total sensory deprivation for perhaps 7-10 years of physical growth and development, and then place them back into the actual, natural, physical world that sensorially impinges upon us humans (and all other living organisms and animals) and examine their mental processes at length -- after first laboriously teaching them language and human meanings embedded in it -- in order to find out about what they have been able to 'think'.
It's obvious, also, that these researchers hark back to Libet's famous experiments and implicitly adopt interpretations of his research that run counter to Libet's and others' interpretations. In fact, the way these Simon Foundation researchers interpret the 50 millisecond delay recognized in Libet's experiments runs directly counter to what Libet was able to establish: i.e., that the body begins to respond to a stimulus represented on a computer screen 50 milliseconds before the subject being tested 'decides' to respond by striking a key [or not striking a key], whereas the researchers quoted in the Simons Foundation article believe that 'information' lies latent, unconscious, and unexpressed in a conjectured "motor-null 'dimension'" before becoming available to the body's sensorally and mentally responsive behaviors/actions.
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