| dc.description.abstract | P300, an event-related potential evoked by oddball paradigm, has drawn a lot of attentions in cognitive neuroscience. Many efforts have been put on the study of the generating mechanism underlying P300, in particular, the network architectures and their possible functional roles, yet the conclusion has not been reached.
In this study, we aim to explore the hierarchical network of sensory P300 production by dynamic causal modelling for event-related potential (DCM for ERP) with a VR based novel oddball paradigm. Moreover, we investigate the connection strength changes and causal relationship of this P300 network to address the possible functional roles. Ten healthy right-handed volunteers underwent electroencephalogram recording while performing a catch-ball game using their dominant hand in 3-D Virtual Reality environment. For eliciting sensory P300, the game was designed to comprise two types of tactile stimuli: standard (with force feedback via a haptic feedback system) and target (without force feedback), with the 479 and 121 trials (i.e. 80% and 20%occurring), respectively. 30 channels electroencephalogram (EEG) and 2 channels electrooculography (EOG) were recorded with 250 Hz sampling rate during the task. The data were epoched offline, with a peristimulus window of -500 to1000 ms, filtered with 30 Hz low-pass filter, artefact removal using the fully automated correction method and averaged across artefact-free trials for classical ERP study. In DCM analysis, the time window of interest was set from 0 to 900ms, and the data were reduced to nine key dimensions using principal component analysis for computational expense. We first specify six plausible models, differed in the areas and the input based on three previous literatures, to identify the most likely model hierarchy. Then the target-specific modulation effects in terms of forward, backward and forward-backward were tested based on the winning model.
Classical event-related potentials analysis suggested that the catch-ball game based on 3-D Virtual Reality can be used to elicit the somatosensory P300 components reliably. DCM results show that the parietal-frontal network was the most possible model among models tested to explain the brain activity during this sensory oddball paradigm. In our experiment, the P300 was generated by the network with forward and backward modulations, and the contribution of forward modulations to the generation of P300 was significantly greater than that of backward modulations. The functional role of this forward modulation may involve in the delivery of the sensory information and the automatic detection of difference, the stimulus-driven attentional processes and the memory operation related to context-updating and subsequent memory storage. In contrast, the backward modulation was thought to engage in attention control and motor control, which is absent (i.e. no motor output requested) in our experiment, and leads to a minor contribution to our model.
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