Dopamine influences attentional rate modulation in Macaque posterior parietal cortex

Distinct processing of the state prediction error signals in frontal and parietal correlates in learning the environment model

Goal-directed reinforcement learning constructs a model of how the states in the environment are connected and prospectively evaluates action values by simulating experience. State prediction error (SPE) is theorized as a crucial signal for learning the environment model. However, the underlying neural mechanisms remain unclear. Here, using electroencephalogram, we verified in a two-stage Markov task two neural correlates of SPEs: an early negative correlate transferring from frontal to central electrodes and a late positive correlate over parietal regions. Furthermore, by investigating the effects of explicit knowledge about the environment model and rewards in the environment, we found that, for the parietal correlate, rewards enhanced the representation efficiency (beta values of regression coefficient) of SPEs, whereas explicit knowledge elicited a larger SPE representation (event-related potential activity) for rare transitions. However, for the frontal and central correlates, rewards increased activities in a content-independent way and explicit knowledge enhanced activities only for common transitions. Our results suggest that the parietal correlate of SPEs is responsible for the explicit learning of state transition structure, whereas the frontal and central correlates may be involved in cognitive control. Our study provides novel evidence for distinct roles of the frontal and the parietal cortices in processing SPEs.

Challenges and innovations in brain PET analysis of neurodegenerative disorders: a mini-review on partial volume effects, small brain region studies, and reference region selection

Positron Emission Tomography (PET) brain imaging is increasingly utilized in clinical and research settings due to its unique ability to study biological processes and subtle changes in living subjects. However, PET imaging is not without its limitations. Currently, bias introduced by partial volume effect (PVE) and poor signal-to-noise ratios of some radiotracers can hamper accurate quantification. Technological advancements like ultra-high-resolution scanners and improvements in radiochemistry are on the horizon to address these challenges. This will enable the study of smaller brain regions and may require more sophisticated methods (e.g., data-driven approaches like unsupervised clustering) for reference region selection and to improve quantification accuracy. This review delves into some of these critical aspects of PET molecular imaging and offers suggested strategies for improvement. This will be illustrated by showing examples for dopaminergic and cholinergic nerve terminal ligands.

Music-based interventions for unilateral spatial neglect: A systematic review

This study aimed to evaluate the effects of music-based interventions on unilateral spatial neglect. Five databases were retrieved prior to May 5, 2022. A range of study designs were considered, including randomized controlled trials, controlled clinical trials, cohorts, and case series/reports. Types of music-based interventions were not limited. Methodological quality of randomized trials were evaluated using the RoB 2 tool, and the RoBiNT scale was utilized to assess the quality of case studies. Two authors independently summarized main results for assessments. Search strategies identified 186 potentially relevant articles, and 10 articles were collected for in-depth analysis. Preliminary results showed that USN patients performed better in cancellation tests than bisection tests after music-based intervention. In summary, pleasant music listening may have a beneficial effect on the visual attention of USN patients, and it can be hypothesized that this is related to the positive mood and emotions of patients induced by music. Music with a dynamic auditory stimulus as a new music listening programme in USN rehabilitation is worthy of further investigation. Instrument playing intervention can be considered as a multisensory stimulation to ameliorate neglect performance via multiple mechanisms. However, current results only support the short-term positive effects of music-based interventions on USN.