Humans continuously adapt their actions and behaviors in response to changes in their surrounding environment. Past neuroscience studies suggest that this adaptation process relies on the brain’s ability to translate abstract goals or rules into specific physical actions or behaviors, yet its neural underpinnings have not yet been clearly elucidated.
Researchers at University Medical Center Tübingen and University of Tübingen recently carried out a study aimed at better understanding how context-related mental representations in a region of the brain known as the prefrontal cortex (PFC) are transformed into movement plans, which are processed in the primary motor cortex (M1). Their findings, published in Nature Neuroscience, led to the identification of a distinct communication subspace that links the PFC and M1, through which contextual information that can inform the planning of actions is transmitted.
“Adaptive behavior relies on the ability to translate abstract rules and goals into actions suited to the current context,” wrote Neha Binish, Jonas Terlau and their colleagues in their paper. “Neural population activity in the PFC has been proposed to support such flexible computations through high-dimensional dynamics, whereas activity in the M1 is related more directly to movement execution. How contextual representations in PFC are transformed into ensuing action plans within M1 remains unknown.”
Converting abstract contextual information into action plans
As part of their study, Binish, Terlau and their colleagues recorded neural activity in the brains of 12 patients with drug-resistant epilepsy, who had electrodes implanted in their brain as part of their treatment. They particularly focused on activity in the PFC and M1, as earlier works suggested that these regions play a key role in the flexible planning of future actions or behaviors.
“Previous work suggests that low-dimensional coding subspaces might organize interareal communication, but direct evidence for such population-level communication mechanisms in humans is lacking,” wrote the authors. “We use intracranial recordings from human PFC and M1 to identify a communication subspace embedded within high-dimensional PFC activity, that selectively relays behaviorally relevant information at the single-trial level.”
The study participants were asked to complete a task that required them to detect a specific target as quickly as possible, using contextual cues as guidance. When they analyzed the brain activity recorded while the participants were completing this task, using computational and statistical tools, the researchers uncovered a simplified neural signaling pathway (i.e., a communication subspace) via which contextual information appeared to be transmitted from the PFC to the M1.
“Activity in this subspace predicts context-dependent action more strongly than either region, revealing a fundamental coding principle by which coordinated interareal population dynamics filter and relay predictive information to guide context-dependent actions,” wrote Binish, Terlau and their colleagues.
Informing future research and new tech development
The recent work by Binish, Terlau and their colleagues identifies a new communication subspace between the PFC and M1 that appears to selectively transmit behaviorally relevant contextual information that can help to plan movements. As their study only involved 12 participants, further research is needed to validate their observations.
Overall, the team’s preliminary findings appear to support the idea that the brain relies on simplified communication pathways to efficiently transfer information that can inform the planning of future behaviors. If these results are confirmed in further studies, they could potentially improve the understanding of neurological or psychiatric conditions characterized by difficulties with planning future actions, including Parkinson’s disease and schizophrenia.
In the future, the researchers’ efforts might also inform the development of new technologies, including neuro-prosthetic devices and other devices that can interface with the human brain, translating people’s intentions into specific commands. Concurrently, they could also inspire the creation of new brain-inspired algorithms that plan the actions of robots, adapting to changes in their surrounding environment.