The neural basis of Neuron's "Yerkes-Dodson law"

Our inner state directly affects our perception and decision-making
.
Thanks to the research of psychologists Robert Yerkes and John Dilligham Dodson, the role that motivation plays in behavioral tasks has been known for more than a century, but its exact effects on the brain remain unclear
.
A team from the University of Geneva (UNIGE), in collaboration with EPFL, revealed how motivation changes the neural circuits responsible for sensory perception in mice before making decisions
.
This research reveals why too high or too low a level of motivation affects our perception, and thus our choices
.
The results, published in Neuron, open up new perspectives on
learning methods.

Going to work early in the morning and choosing a restaurant for lunchtime: many of our decisions are driven by needs, such as making a living or satisfying our hunger
.
However, decision-making is a complex process, and it can also be influenced by external factors, such as the environment or other individuals, as well as our internal state, such as our emotions, our level of attention, or our degree of
motivation.

The lab of Sami El-Boustani, assistant professor in the Department of Basic Neurosciences at the United Nations School of Health School of Medicine
, is studying neural circuits related to decision-making.
Sami El-Boustani received an Eccellenza Scholarship (SNSF).

In recent work, his lab worked with Professor Carl Petersen's team at EPFL to investigate the role
that a specific internal state – motivation – plays in perception and decision-making.
For more than a century, thanks to the work of American psychologists Robert Yerkes and John Diligam Dodson, it has been known that there is a relationship
between motivation and performance.
Too much or too little motivation is not good for performance
.
However, the way this affects our neural circuits is unclear
.
"We wanted to look at how the sensory information transmitted by neurons in the cortex is altered by the degree of motivation, and to what extent motivation affects performance in learning and decision-making tasks," explains
Sami El-Boustani, lead author of the study.

The research team developed a behavioral paradigm that allows mice to move
around in a controlled state of water consumption.
They first trained these rodents to respond to tactile stimuli through two whiskers (A and B) and produced an action — licking the spout — that only beard A could get a drop of water
.
After this training, the mice mainly responded to stimuli from beard A, thus demonstrating their ability to distinguish between the two senses
.
Finally, to change the rodents' motivation to participate in the task, the researchers conducted these experiments
with reduced thirst.

Highly motivated states obscure sensory information

In a state of extreme thirst, rodents behave poorly, licking the spout indiscriminately and not distinguishing between irritated whiskers
.
In contrast, in a state of moderate thirst, behavioral choices become optimal
.
Stimulate beard A, lick the spout
.
Finally, when they are not very thirsty, their performance in the task drops
again.

By observing the activity of groups of neurons responsible for perceptual decision-making in these mice, the researchers found that when the mice were highly stimulated, the neurons in these circuits were filled with electrical signals
.
Conversely, in a low-motivation state, the signal is
too weak.
Giulio Matteucci, a postdoctoral researcher in Sami El-Boustani's lab and first author of the study, said: "Overmotivation leads to intense stimulation of cortical neurons, which leads to a decrease
in the accuracy of tactile stimulation perception.
"

In contrast, in the low-motivation state, the accuracy of the sensory information was restored, but the signal strength was too low to be transmitted
correctly.
As a result, the perception of stimuli is also impaired
.

Have a new understanding of learning

These results open up new perspectives
.
They provide the possible neural basis
for the Yerkes-Dodson law.
"They also reveal that the level of motivation influences not only decision-making, but also the perception of sensory information that leads to it," explains Carl Petersen, a full professor at the EPFL Brain Mind Institute and co-senior author
of the study.

This work also demonstrates the need to separate the acquisition and expression of new knowledge
.
"We observed that the rats understood this rule very quickly, but it took a long time to express this learning, depending on changes
in perception associated with their motivational levels.
" The revelation of the role of motivation in learning opens the way to new adaptive approaches that aim to maintain optimal levels of
motivation during the learning process.

Cortical sensory processing across motivational states during goal-directed behavior