Motivational urges, Motor System, and Neurological Correlates

 How can we measure the connection between human urges, the translation of those urges in the form of behavior, and the neurological mechanism of action? This is precisely the question Gupta and Aron set out to answer in their article, “Urges for food and money spill over into motor system excitability before action is taken.” No doubt, much of human behavior is driven by urges. In psychological jargon, the operational definition of an urge can be defined as how much someone desires an object, relative to its perceived value.

Wondering whether the urges for food and money are detectable by way of motor system excitability, the researchers in this article employed the use of transcranial magnetic stimulation (TMS) and concurrent electromyography to test their hypothesis. They hypothesized that stimuli associated with stronger urges, in this case food and money, would correspond to higher motor excitability and that this excitability would be evident before the participant consciously decided which motor response to make.

            As is typical, the experiment consisted of 17 young adults (9 male, mean age=21.9) who were instructed not to eat for 4 hours prior to the study. They were presented with 60 food items ranging from candy bars to clam juice, and were told to rate them on a 5 point likert scale. Two other similar experiments were conducted using a monetary paradigm instead of food. For all three experiments, there was a randomized presentation of food items (the stimuli), and each trial began by simple priming: either a picture of food or an empty rectangle. A choice screen followed, providing the participants with a Yes/No option corresponding to either the left or right index finger. Further, this Yes/No option was randomized—that is, participants would not always be presented with the “yes” option corresponding to the right index finger.

            This is interesting since it negates the possibility simple response preparation. Nor can this be simply a matter of increased arousal, since the effect was present only when action was required. Concerning this, the researchers note that “it must also reflect motivational processing that is upstream from the corticospinal system…[that] likely involves brain systems such as the orbital frontal cortex and associated limbic circuitry, including the ventral striatum ⁄ nucleus-accumbens and ventral pallidum.” (Gupta, 2010, p. 186).

            The article mentions its contribution to the growing literature of embodied cognition. Indeed, with the sensitive testing method they used, they provide the ability of observing the so called motivational “spill-over” into the motor system, even before the motor system knows exactly what to do.

            Further research is needed to investigate the action the researchers anticipated, namely that the motivational spill-over will correspond to heightened activation of motor regions of the basal ganglia.

by Phillip J. Kuna

for John G. Kuna, PsyD and Associates 

Licensed Psychologist

http://drjohngkuna.com

References

Gupta, N., & Aron, A. R. (2011). Urges for food and money spill over into motor system

excitability before action is taken. European Journal Of Neuroscience, 33(1), 183-188. doi:10.1111/j.1460-9568.2010.07510.x