An Interesting Article

[From Rick Marken (2016.04.12.1130)

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Richard Pfau (2016.04.07 15:41 EDST)

RF: The following article is interesting: Olof Lagerlof et al., “The nutrient sensor OGT in PVN neurons regulates feeding,” Science, Vol. 351, Issue 6279, 18 March 2016, pp. 1293-1296.

RF: The article indicates that (1) an enzeme (OGT) that senses the level of nutrients inside certain brain neurons (PVN), (2) regulates excitatory synaptic input and firing of those neurons, that then (3) regulates/reduces satiation (appetite) and resulting eating behavior that affects the levels of nutrients sensed. Using PCT to interpret what is happening, the (PVN) neurons firing after enzyme sensitization seem to serve (a) as sensors that provide perceptual signals to other neural areas. However, I can also imagine that these sensitized (PVN) neurons might serve (b) as providers of reference signals, or (c) as comparators that produce error signals that lead to reduced satiation/appetite and resulting behavior.

RF: Perhaps someone more knowledgeable than me about neurology might better interpret the article’s findings with PCT in mind, because it’s not clear to me whether (a), (b), or (c) above is applicable.

RM: I think one can interpret the finding with just PCT. The article suggests that excitatory synaptic input is a controlled variable. If this is the case then there must be a control system controlling it. That implies something that senses excitatory synaptic input and acts to affect it. OMG is claimed to be an enzyme that senses, but it is not the purported controlled variable – excitatory synaptic input – that it senses. What it senses is the level of nutrients inside certain brain neurons. Perhaps the level of nutrients inside a neuron is directly proportional to excitatory synaptic input . If so, then OMG could be the sensor component of the control system that controls the level of excitatory synaptic input. But even if that is the case, OMG can’t “regulate” (that is, control) excitatory synaptic input. In order to determine how excitatory synaptic input is controlled you also need to find the output that affects it and the reference specification to the level at which excitatory synaptic input is controlled at any moment.

RM: The problem here is that the people who did this study don’t know what control is. They apparently think that controlling is the same as causing.This seems to be a very common error in studies of neuropsychology and, of course, in psychology in general. Very often research is reported as the discovery that “variable X controls variable Y”. But variables can’t control, they can only cause. Control results from a particular organization of causal connections between variables, the organization being that of a closed negative feedback loop.

Best

Rick


Richard S. Marken

Author, with Timothy A. Carey, of Controlling People: The Paradoxical Nature of Being Human.