Emergence of preference coding in the macaque lateral prefrontal cortex by neurofeedback of unit activity related to working memory

Techniques utilizing neurofeedback, a form of biofeedback using neural signals from the brain, have been applied lately to higher association areas such as the lateral prefrontal cortex (LPFC); however, it remains unexplored how well neurofeedback using unit activity in the LPFC modulates its working memory-related activity and performance. To address this issue, we provided neurofeedback of LPFC unit activity during a delay period to two monkeys while they performed a delayed matching-to-paired-sample task. In the task, neurofeedback allowed the animals to shorten the delay length by increasing delay activity and make an earlier choice. Neurofeedback significantly increased delay activity in two-thirds of task-related neurons. Notably, in 16% of these neurons, a preference for delay activity and performance dependent on the stimulus emerged. Although neurofeedback decreased performance primarily due to choice errors, the disassociation of neurofeedback linkage rescued performance. Further, the neuronal activity of simultaneously recorded neurons without neurofeedback linkage suggests that neurofeedback reconfigured the net activity of the LPFC to adapt to new situations. These findings indicate that LPFC neurons can dynamically multiplex different types of information to adapt to environmental changes. Thus, we demonstrated the significant potential of neurofeedback using unit activity to investigate information processing in the brain.