Tagged: Timing

Using single-trial EEG to estimate the timing of target onset during rapid serial visual presentation

The timing of a behavioral response, such as a button press in reaction to a visual stimulus, is highly variable across trials. In this paper we describe a methodology for single-trial analysis of electroencephalography (EEG) which can be used to reduce the error in the estimation of the timing of the behavioral response and thus reduce the error in estimating the onset time of the stimulus. We consider a rapid serial visual presentation (RSVP) paradigm consisting of concatenated video clips and where subjects are instructed to respond when they see a predefined target. We show that a linear discriminator, with inputs distributed across sensors and time and chosen via an information theoretic feature selection criterion, can be used in conjunction with the response to yield a lower error estimate of the onset time of the target stimulus compared to the response time. We compare our results to response time and previous EEG approaches using fixed windows in time, showing that our method has the lowest estimation error. We discuss potential applications, specifically with respect to cortically-coupled computer vision based triage of large image databases

Spatio-temporal linear discrimination for inferring task difficulty from EEG

We present a spatio-temporal linear discrimination method for single-trial classification of multi-channel electroencephalography (EEG). No prior information about the characteristics of the neural activity is required i.e. the algorithm requires no knowledge about the timing and/or spatial distribution of the evoked responses. The algorithm finds a temporal delay/window onset time for each EEG channel and then spatially integrates the channels for each channel-specific onset time. The algorithm can be seen as learning discrimination trajectories defined within the space of EEG channels. We demonstrate the method for detecting auditory evoked neural activity and discrimination of task difficulty in a complex visual-auditory environment