A 'passive' event-related potential?

Neuronal correlates of a virtual-reality-based passive sensory P300 network

P300, a positive event-related potential (ERP) evoked at around 300 ms after stimulus, can be elicited using an active or passive oddball paradigm. Active P300 requires a person’s intentional response, whereas passive P300 does not require an intentional response. Passive P300 has been used in incommunicative patients for consciousness detection and brain computer interface. Active and passive P300 differ in amplitude, but not in latency or scalp distribution. However, no study has addressed the mechanism underlying the production of passive P300. In particular, it remains unclear whether the passive P300 shares an identical active P300 generating network architecture when no response is required. This study aims to explore the hierarchical network of passive sensory P300 production using dynamic causal modelling (DCM) for ERP and a novel virtual reality (VR)-based passive oddball paradigm. Moreover, we investigated the causal relationship of this passive P300 network and the changes in connection strength to address the possible functional roles. A classical ERP analysis was performed to verify that the proposed VR-based game can reliably elicit passive P300. The DCM results suggested that the passive and active P300 share the same parietal-frontal neural network for attentional control and, underlying the passive network, the feed-forward modulation is stronger than the feed-back one. The functional role of this forward modulation may indicate the delivery of sensory information, automatic detection of differences, and stimulus-driven attentional processes involved in performing this passive task. To our best knowledge, this is the first study to address the passive P300 network. The results of this study may provide a reference for future clinical studies on addressing the network alternations under pathological states of incommunicative patients. However, caution is required when comparing patients’ analytic results with this study. For example, the task presented here is not applicable to incommunicative patients.

Characterization of N200 and P300: selected studies of the Event-Related Potential

The Event-Related Potential (ERP) is a time-locked measure of electrical activity of the cerebral surface representing a distinct phase of cortical processing. Two components of the ERP which bear special importance to stimulus evaluation, selective attention, and conscious discrimination in humans are the P300 positivity and N200 negativity, appearing 300 ms and 200 ms post-stimulus, respectively. With the rapid proliferation of high-density EEG methods, and interdisciplinary interest in its application as a prognostic, diagnostic, and investigative tool, an understanding of the underpinnings of P300 and N200 physiology may support its application to both the basic neuroscience and clinical medical settings. The authors present a synthesis of current understanding of these two deflections in both normal and pathological states.

Event-related potentials (ERPs) to schematic faces in adults and children

Event-related potentials (ERPs) were recorded from 4-year-old 8-10-year-old children and adults to a schematic face, inverted face and jumbled face. The subjects were instructed to fixate the stimuli and no other response was required. The schematic face and inverted face were shown with a frequency of 20% each and the remaining presentations (60%) were of the jumbled face. P1 and N170 peak latency were measurable in the children and adults. These peaks were at longer latencies in the children. P3 was measurable in the adults and 8-10-year-old children but not the 4-year-olds. The adults had larger and longer latency P1 and smaller amplitude N170 to the inverted face than the other faces. In contrast, the P1 was unaffected by inversion in the children and the N170 was not smaller to the inverted or jumbled face. It is concluded that this result reflects developmental differences in the processing of configuration, with the children relying on an under-specified configuration of the face.