Modulation of P3m Amplitude by Task Difficulty in a Visual Oddball Task

Background

In cognitive neuroscience research, Event-Related Potentials (ERP) and Event-Related Fields (ERF) are important means to explore the cognitive processing mechanisms of the brain. Among these, the P3 component (referred to as P3m in magnetoencephalography) has garnered special attention. The P3 typically appears between 300 to 600 milliseconds after stimulus presentation, manifesting as a large positive deflection. Its latency and amplitude can be influenced by various task parameters, such as task difficulty and stimulus probability. Additionally, changes in P3 are closely associated with several neurological and psychiatric disorders, including Attention Deficit Hyperactivity Disorder (ADHD), Alzheimer’s disease, schizophrenia, and depression. Thus, P3 is considered a potential physiological biomarker for diagnosing these conditions.

Previous research indicates that increasing task difficulty generally leads to a reduction in P3(m) amplitude. However, it remains unclear whether the modulation of P3 due to changes in task difficulty originates from the same brain regions traditionally associated with P3 generation. Clarifying the origin of P3m and its modulation due to task difficulty holds significant importance for the application of non-invasive brain stimulation (NIBS) interventions.

Research Background and Motivation

To investigate these scientific questions, the research team developed a new visual Oddball discrimination task. By using nearly identical visual stimuli but varying task difficulty, the study aimed to modulate the P3m component. The research sought to identify the brain regions generating P3m under different task difficulties and to understand the modulation induced by these changes.

Research Source

This study was conducted by scholars Cindy Boetzel, Heiko I. Stecher, Florian H. Kasten, and Christoph S. Herrmann, affiliated with the Laboratory of Experimental Psychology at the European Medical School, the Neuroimaging Department at Carl von Ossietzky University, and the Brain and Cognition Research Center at Paul Sabatier University in Toulouse, France. The research findings were published in the 2024 issue of Scientific Reports, article number 14:1505, DOI: https://doi.org/10.1038/s41598-023-50857-z.

Research Design and Methods

1. Experimental Task Design Researchers designed a visual Oddball discrimination task with two levels of difficulty (simple and difficult). Task difficulty was manipulated by adjusting the rotation angle of Gabor patches while maintaining other physical properties of the stimuli unchanged. Smaller rotation angles represented higher task difficulty.

2. Participants A total of 19 participants took part in the MEG experiment, with 15 participants (9 females) meeting the criteria for data analysis. Participants were right-handed, had no psychiatric or neurological disorders, and had normal or corrected-to-normal vision.

3. MEG and Data Collection During the MEG experiment, participants were required to discern the rotation direction of Gabor stripes and complete the task under both simple and complex conditions. Neuromagnetic signals were recorded using a 306-channel whole-head MEG system, followed by source analysis of the data.

4. Data Analysis Data processing was conducted using the FieldTrip toolbox and custom MATLAB scripts. Statistical analyses of ERF differences were performed using the CBPT method and LCMV beamformer algorithm to explore the dependency of P3m amplitude modulation on task difficulty and determine its brain origin.

Research Results

1. Behavioral Results The study found that increasing task difficulty (difficult condition) led to a significant decrease in D’ (discrimination ability) and prolonged reaction time (RT), indicating successful modulation of task difficulty.

2. P3m Amplitude Modulation MEG data analysis revealed that in the difficult condition, the P3m amplitude for target and standard stimuli significantly decreased, primarily within the 300-600 millisecond post-stimulus time window.

3. Source Analysis Source localization of P3m modulation showed that the reduction in P3m amplitude mainly occurred in bilateral central-parietal and temporal regions. These regions align with previously identified P3 generators and also include parts of the precentral and postcentral gyri and inferior parietal lobule.

Discussion

The study demonstrated that adjusting task complexity significantly influenced P3m amplitude, with such modulation mainly originating from traditional P3 generator regions. Results underscore the importance of brain resource allocation and information processing load on ERP amplitude, providing valuable insights for future interventions using NIBS to modulate P3m.

Significance of the Study

This research offers new methods and perspectives for exploring brain cognitive processing mechanisms. Through rigorous experimental design and data analysis, the study identified the brain regions involved in the modulation of P3m due to task difficulty changes, laying the groundwork for applying such findings in brain stimulation interventions. Additionally, it highlights multiple task modulation methods and different stimulus parameters in ERP research, pointing to new directions for future studies.

Conclusion

The study successfully established a reliable experimental paradigm to investigate the impact of task difficulty on P3m amplitude modulation and identified the brain regions responsible for these effects. These findings will be instrumental for future experiments and could apply this knowledge to the diagnosis and intervention of neurological disorders.