In a good mood or a bad mood, focused or distracted, desperate or unnecessary – our internal states directly affect our perceptions and decision making. Although the role of motivation in performing behavioral tasks has been known for more than a century, thanks to the work of psychologists Robert Yerkes and John Dilligham Dodson, its precise effect on the brain remains unclear. A team from the University of Geneva (UNIGE), in collaboration with the EPFL, revealed how motivation alters the neural circuits responsible for sensory perception that precedes decision making in mice. This study reveals why too high or too low a level of motivation can influence our perception and therefore our choices. These results, published in the journal Neuronopen new perspectives in learning methods.
Going to work early in the morning, choosing a restaurant at lunchtime – many of our decisions are motivated by needs, such as making a living or satisfying our hunger. However, decision making is a complex process, which can also be influenced by external factors, such as the environment or other individuals, and by our internal states, such as our mood, our level of attention or our degree of motivation.
The laboratory of Sami El-Boustani, researcher at the Department of Basic Neuroscience of the UNIGE Faculty of Medicine and recipient of an Excellence Scholarship (FSNS), is studying the neural circuits involved in decision-making. In a recent work, done in collaboration with Professor Carl Petersen’s team at EPFL, his lab studied the role played by a specific internal state – motivation – in perception and decision making. For more than a century, it has been known that there is a relationship between motivation and performance thanks to the work of American psychologists Robert Yerkes and John Dilligham Dodson. Too much or too little motivation is detrimental to performance. However, how this affects our neural circuits remains unclear. “We wanted to observe how sensory information transmitted by neurons in the cortex is altered by the degree of motivation and to what extent this can have an effect on learning and performance in a decision-making task,” explains Sami El-Boustani, the author. principal of the study.
The research team developed a behavioral paradigm involving mice in a controlled water consumption regime. First they trained these rodents to respond to tactile stimuli via two whiskers (A and B) and to produce an action – licking a spout – only for whisker A in order to obtain a drop of water. Following this training, these mice reacted primarily to whisker A stimulation, thus indicating their ability to discriminate between these two sensations. Finally, the researchers conducted these experiments at decreasing levels of thirst to vary the rodents’ motivation to participate in the activity.
The state of hypermotivation blurs sensory information
In a state of great thirst, therefore of great motivation, the rodents have behaved badly. They licked the nozzle indiscriminately, without distinguishing between the stimulated mustaches. On the contrary, in a state of moderate thirst, the choice of one’s action became optimal. They mainly licked the nozzle when the A whisker was stimulated. Eventually, when they weren’t very thirsty, their performance on the task decreased again.
By observing the activity of the neuronal populations responsible for perceptual decision making in these mice, the researchers found that the neurons in these circuits were flooded with electrical signals when the mice were hyper-motivated. Conversely, in a state of low motivation, the signals were too weak. “Hypermotivation leads to strong stimulation of cortical neurons, which causes a loss of precision in the perception of tactile stimuli,” says Giulio Matteucci, a Postdoctoral Fellow in Sami El-Boustani’s laboratory and first author of the study.
Conversely, in the state of low motivation, the accuracy of the sensory information was recovered, but the signal strength was too low to be transferred correctly. Consequently, the perception of stimuli was also impaired.
A new understanding of learning
These results open up new perspectives. They provide a possible neural basis for the Yerkes-Dodson law. “ They also reveal that the level of motivation not only affects the decision-making process, but also the perception of sensory information, which leads to the decision, ” explains Carl Petersen, Full Professor at EPFL’s Brain Mind Institute and co-senior author in the studio.
This work also suggests that there is a need to decouple the acquisition and expression of new knowledge. “ We observed that the mice understood the rule very quickly, but could only express this learning much later, depending on an altered perception linked to their level of motivation. ” This unveiling of the role of motivation in learning. paves the way for new adaptive methods that aim to maintain an optimal level of motivation during learning.
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