Summary: Our brains make predictions based on experience during episodes of learning. Researchers found expectations during the predictions affect the activity of various brain networks.
During learning, the brain is a prediction engine that continually makes theories about our environment and accurately registers whether an assumption is true or not. A team of neuroscientists from Ruhr-Universität Bochum has shown that expectation during these predictions affects the activity of various brain networks. Dr. Bin Wang, Dr. Lara Schlaffke and Associate Professor Dr. Burkhard Pleger from the Neurological Clinic of Berufsgenossenschaftliches Universitätsklinikum Bergmannsheil report on the results in two articles that were published in March and April 2020 in the journals Cerebral Cortex and Journal of Neuroscience.
The neuroscientists identified two key regions in the brain: the thalamus plays a central role in decision-making. The insular cortex, on the other hand, is particularly active when it is clear whether the right or wrong decision has been made. “The expectation during learning then regulates specific connections in the brain and thus the prediction for learning-relevant sensory perception,” says Burkhard Pleger.
Focus on the decision making process
For the investigation, the team used a learning task that focuses on the decision-making process during the perception of skin contact in the brain. “It’s like learning a computer strategy game using a game pad, which gives sensory feedback to certain fingers on certain stimuli,” compares Pleger. “The point is that a certain touch stimulus leads to success and that this has to be learned from stimulation to stimulation.”
28 participants were given either tactile stimulus A or B on the index finger in each trial run. At the push of a button, they then had to predict whether the subsequent tactile stimulus would be the same or not. The probability of A and B was constantly changing, which the participant had to learn from prediction to prediction.
During the test, the participants’ brain activity was examined using functional magnetic resonance imaging. The researchers were particularly interested in the trial runs in which the participants changed their decision-making strategy. They asked the question to what extent the change in expectations influenced brain activity.
To the researchers two brain regions stood out: the thalamus and the insular cortex. The thalamus processes information that comes from the sensory organs or other areas of the brain and passes it on to the cerebrum. It is also called the gateway to consciousness.
A new role for the thalamus
Using functional magnetic resonance images, the researchers were able to show that different brain connections between the prefrontal cortex and the thalamus were responsible for maintaining a learning strategy or changing the strategy. The higher the expectations before the decision, the sooner the strategy was maintained and the lower the strength of these connections. With low expectations, there was a change of strategy and the regions seemed to interact much more strongly with each other. “The brain appears to be particularly active when a learning strategy has to be changed while it takes significantly less energy to maintain a strategy,” concludes Pleger.
“So far, the thalamus has been viewed as a switch,” adds the neuroscientist. “Our results underline its role in higher cognitive functions that help decision-making while learning. So the thalamus is not only a gateway to sensory consciousness, but rather it seems to link it to cognitive processes that serve, for example, to make decisions
Affecting sensory perception
The insular cortex, on the other hand, is involved in perception, motor control, self-confidence, cognitive functions and interpersonal experiences. This part was particularly active when a participant had already made his decision and then found out whether he was right or wrong. “Different networks that are anchored in the insular cortex are regulated by expectations and thus seem to have a direct influence on future sensory perception,” said Pleger.
About this neuroscience research article
Source: RUB Media Contacts: Burkhard Pleger – RUB Image Source: The image is credited to RUB, Marquard.
Confidence in decision-making during probabilistic tactile learning is related to distinct thalamo-prefrontal pathways
The flexibility in adjusting the decision strategy from trial to trial is a prerequisite for learning in a probabilistic environment. Corresponding neural underpinnings remain largely unexplored. In the present study, 28 male humans were engaged in an associative learning task, in which they had to learn the changing probabilistic strengths of tactile sample stimuli. Combining functional magnetic resonance imaging with computational modeling, we show that an unchanged decision strategy over successively presented trials related to weakened functional connectivity between ventralmedial prefrontal cortex (vmPFC) and left secondary somatosensory cortex. The weaker the connection strength, the faster participants indicated their choice. If the decision strategy remained unchanged, participant’s decision confidence (i.e., prior belief) was related to functional connectivity between vmPFC and right pulvinar. While adjusting the decision strategy, we instead found confidence-related connections between left orbitofrontal cortex and left thalamic mediodorsal nucleus. The stronger the participant’s prior belief, the weaker the connection strengths. Together, these findings suggest that distinct thalamo–prefrontal pathways encode the confidence in keeping or changing the decision strategy during probabilistic learning. Low confidence in the decision strategy demands more thalamo–prefrontal processing resources, which is in-line with the theoretical accounts of the free-energy principle.
Modulations of insular projections by prior belief mediate the precision of prediction error during tactile learning
Awareness for surprising sensory events is shaped by their prior belief inferred from past experience. Here, we combined hierarchical Bayesian modeling with fMRI on an associative learning task in 28 male human participants to characterize the effect of the prior belief of tactile events on connections mediating the outcome of perceptual decisions. Activity in anterior insula (AIC), premotor cortex (PMd) and inferior parietal lobule (IPL) were modulated by prior belief on unexpected targets as compared to expected targets. On expected targets, prior belief decreased the connection strength from AIC to IPL, whereas it increased the connection strength from AIC to PMd when targets were unexpected. Individual differences in the modulatory strength of prior belief on insular projections correlated with the precision that increases the influence of prediction errors on belief updating. These results suggest complementary effects of prior belief on insular-frontoparietal projections mediating the precision of prediction during probabilistic tactile learning.
In a probabilistic environment, the prior belief of sensory events can be inferred from past experiences. How this prior belief modulates effective brain connectivity for updating expectations for future decision-making remains unexplored. Combining hierarchical Bayesian modeling with fMRI, we show that during tactile associative learning, prior expectations modulate connections originating in the anterior insula cortex and targeting salience and attention related frontoparietal areas (i.e., parietal and premotor cortex). These connections seem to be involved in updating evidence based on the precision of ascending inputs to guide future decision-making.