[Comp-neuro] New method for single-trial electrophysiology analysis

Rapela, Joaquin joaquin_rapela at brown.edu
Sat Dec 15 20:47:09 CET 2018


We have recently published an article reporting a new method to study
expectation on single trials of the EEG (Rapela et al., 2018). Using this
method (in an audio-visual attention-shifting oddball task) we discovered a
behaviorally-relevant effect of temporal expectation on the single-trial
coherence of the EEG.

I am interested in checking if this effect can be observed in other
experiments. Thus, I would like to collaborate with, or help to, a scientist
that is interested in studying with our method single-trial effects of
temporal expectation on his/her electrophysiological recordings (EEG, MEG,
ECoG, MEA, single units, etc). If this could interest you, please email me
joaquin_rapela at brown.edu.

Our article appears in Neural Computation and a preprint of it can be found
my web page https://sccn.ucsd.edu/~rapela/pub.htm Code implementing our
appears in https://github.com/joacorapela/singleTrialEEGPredictions

Joaquín Rapela, Marissa Westerfield, Jeanne Townsend (2018a). A new
effect on single-trial phase coherence. Part I: existence and relevance.
Neural Computation 30(9): 2348-83.


This letter makes scientific and methodological contributions.
it demonstrates a new and behaviorally relevant effect of temporal
on the phase coherence of the electroencephalogram (EEG). Methodologically,
introduces novel methods to characterize EEG recordings at the single-trial
level. Expecting events in time can lead to more efficient behavior. A
remarkable finding in the study of temporal expectation is the foreperiod
effect on reaction time, that is, the influence on reaction time of the
between a warning signal and a succeeding imperative stimulus to which
subjects are instructed to respond as quickly as possible. Here we study a
foreperiod effect in an audiovisual attention-shifting oddball task in which
attention-shift cues directed the attention of subjects to impendent deviant
stimuli of a given modality and therefore acted as warning signals for these
deviants. Standard stimuli, to which subjects did not respond, were
interspersed between warning signals and deviants. We hypothesized that
foreperiod durations modulated intertrial phase coherence (ITPC, the degree
phase alignment across multiple trials) evoked by behaviorally irrelevant
standards and that these modulations are behaviorally meaningful. Using
averaged data, we first observed that ITPC evoked by standards closer to the
warning signal was significantly different from that evoked by standards
further away from it, establishing a new foreperiod effect on ITPC evoked by
standards. We call this effect the standard foreperiod (SFP) effect on ITPC.
We reasoned that if the SFP influences ITPC evoked by standards, it should
possible to decode the former from the latter on a trial-by-trial basis. We
were able to do so showing that this effect can be observed in single
We demonstrated the behavioral relevance of the SFP effect on ITPC by
significant correlations between its strength and subjects' behavioral

Cordially, Joaquin
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