Overview: Research reveals that the posterior inferior parietal lobe plays a critical role in integrating information from different sources during decision-making tasks.
Three RIKEN neuroscientists have found a brain region in macaques that is responsible for integrating information from different sources while making decisions.
This finding, published in Mobile Reportswill aid in the investigation of psychiatric disorders that disrupt introspection.
Sometimes, when making decisions, we need to draw on both our memories and the current facts before us. An example is trying to decipher a hastily scribbled note while simultaneously trying to remember what we wrote about. To arrive at a decision, our brains assign levels of trust to the two sources of information and then combine them.
This ability to self-evaluate thoughts and memories is known as metacognition and underlies many behaviors. But it hasn’t been clear where the brain integrates this information when making decisions.
By conducting experiments on macaque monkeys, Kentaro Miyamoto, Rieko Setsuie and Yasushi Miyashita, all of the RIKEN Center for Brain Science, have shown that a brain region known as the posterior inferior parietal lobe (pIPL) performs this integration.
Monkeys were shown an image and had to decide whether they had seen it before or not. To assess their confidence in their decision, the monkeys had to bet on it by choosing between high-risk/high-reward or low-risk/low-reward options.
Perhaps unsurprisingly, the monkeys chose the high-risk option more often when they answered the question correctly than when they answered this wrong. This showed that the monkeys used effective metacognition processes.
Functional magnetic resonance imaging during these experiments revealed that the pIPL was active while the monkeys weighed their gambling options based on the memory test.
Miyamoto was surprised by this. “The prefrontal cortex is considered the most important area for overseeing behavior and making rules-based decisions; some believe that there is ‘the intelligence of the soul’”, he explains.
“So I was very surprised that the whole brain mapping indicated that a region at the back of the brain was active during metacognition.”
The pIPL drew on information from three brain regions in the prefrontal cortex that Miyamoto and Miyashita’s team had previously found to be involved in determining trust in memories. “The memory system itself isn’t in the prefrontal cortex, but the prefrontal cortex is important for reading out trust in memories,” Miyamoto said.
The pIPL then sent a signal to another area, the dorsal anterior cingulate cortex, to carry out the gambling decision.
Miyamoto plans to explore the processing of metacognition at the neuronal level and explore its association with psychiatric disorders in which people compulsively behave in ways they don’t want to.
About this decisive research news
Original research: Open access.
†Conversion of concept-specific decision trust in primate integrative introspectionby Kentaro Miyamoto et al. Mobile Reports
Conversion of concept-specific decision trust in primate integrative introspection
- Time-consuming compensation process for metacognitive evidence works in macaques
- The pIPL encodes the interaction between performance and trust
- The pIPL integrates trust specific to the concept of experience and novelty
- The pIPL prompts the dorsal anterior cingulate cortex to perform strategic actions
Introspection based on the integration of uncertain evidence is critical to acting on abstract thinking and devising future scenarios.
However, it is not known how to integrate confidence readings from multiple sources of different concepts, especially given the relationships between the concepts. In this study, monkeys made bets based on an estimate of their performance in a prior mnemonic.
We found that the longer the response times for post-decision betting, the more the limitations were caused by frontal dislocation. This suggests the existence of a time-consuming compensatory metacognitive process.
We found the posterior inferior parietal lobe (pIPL) as its candidate, which did not encode bet per se (i.e. only high or low bet), but became more active when monkeys successfully chose the optimal betting option based on mnemonic decision performance.
Thereafter, the pIPL prompts the dorsal anterior cingulate cortex to wear the chosen deployment option. Our findings suggest a role for the pIPL in metacognitive concept integration.