Whether we are in a good or poor mood, attentive or distracted, in desperate need or not, our interior moods have a direct impact on our perceptions and decisions. The work of psychologists Robert Yerkes and John Dilligham Dodson, the effect of motivation on the performance of behavioral tasks has been understood for more than a century, but its specific effect on the brain remains unknown. In conjunction with the EPFL, a team from the University of Geneva (UNIGE) has discovered how motivation affects the brain circuits involved in sensory perception before decision-making in mice. This study explains why an excessively high or low amount of motivation might influence our perception and, consequently, our decisions. These findings, published in the journal Neuron, offer new perspectives on learning strategies.
Many of our decisions, like going to work early in the morning and selecting a restaurant for lunch, are motivated by requirements, such as earning a living or fulfilling our hunger. Still, making a choice is a complicated process that can be affected by things outside of us, like the environment or other people, as well as by things inside of us, like our mood, level of attention, or level of motivation.
Sami El-Boustani, Assistant Professor in the Department of Basic Neurosciences at the UNIGE Faculty of Medicine and recipient of an Eccellenza fellowship from the Swiss National Science Foundation, is researching the brain circuits involved in decision-making in his lab. In recent collaboration with Professor Carl Petersen’s team at EPFL, his lab has investigated the function of a particular internal state — motivation — in perception and decision-making. Thanks to the research of American psychologists Robert Yerkes and John Dilligham Dodson, it has been recognized for more than a century that there is a connection between motivation and performance. Both excessive and insufficient motivation are detrimental to performance. However, it remains unknown how this affects our neuronal circuits. The main author of the study, Sami El-Boustani, says, “We wanted to find out how motivation affects how neurons in the cortex send sensory information and how motivation might affect learning and performance in a decision-making task.”
The study team established a behavioral paradigm in which mice consume water in a regulated manner. In order to receive a drop of water, they initially trained these rodents to respond to tactile inputs via two whiskers (A and B) and to perform an action—licking a spout—using only whisker A. As a result of this training, these mice responded primarily to stimulation of whisker A, suggesting their capacity to distinguish between these two sensations. Researchers did these tests at progressively lower levels of thirst so they could change how much the rodents wanted to do the job.
A hyper-motivational state obscures sensory information.
In a state of extreme thirst (and hence high motivation), rodents demonstrated poor performance. They licked the spout without discriminating between the whiskers that were activated. In contrast, when their thirst was mild, the best course of action became apparent. When whisker A was activated, they mostly licked the spout. When they were no longer thirsty, their performance on the job declined once more.
Observing the activity of neuronal populations important for perceptual decision-making in these mice, researchers found that neurons in these circuits were inundated with electrical signals when the mice were highly motivated. In a state of low motivation, however, the signals were too weak. According to Giulio Matteucci, a postdoctoral fellow in the laboratory of Sami El-Boustani and the study’s lead author, hyper-motivation produces a loss of precision in the perception of tactile stimuli.
In contrast, in the low-motivation condition, the precision of the sensory information was restored, but the signal intensity was insufficient for correct transmission. Consequently, perception of the stimuli was hampered.
A fresh perspective on learning
These findings provide new insights. They suggest a neurological foundation for the Yerkes-Dodson law. Carl Petersen, a Full Professor at EPFL’s Brain Mind Institute and the study’s co-lead author, says, “They also show that the level of motivation affects not only the decision-making process but also how sensory information is interpreted, which in turn affects the decision.”
This research also implies that information acquisition and expression must be separated. We noticed that mice comprehended the rule relatively early but were unable to convey this understanding until much later due to a perceptual change correlated with their level of drive. This better understanding of how motivation affects learning makes it possible to come up with new, flexible ways to keep the right amount of motivation throughout the learning process.
