Single trial variability in neural activity during a working memory task reveals multiple distinct information processing sequences

Multiple Brain Activation Patterns for the Same Perceptual Decision-Making Task

“…However, increasing gamma favors the identification of smaller clusters and lowering gamma favors the identification of larger clusters. Further, we expected to find a small number of clusters because in previous work in which we clustered trials in EEG data we found at most three 62,64 .…”

“…The representative partition is then obtained by using a Generalized Louvain algorithm to identify clusters within the thresholded nodal association matrix 60 . We have previously utilized this method to identify trial subtypes in brain activity measured with electroencephalography in a motion discrimination 61 task and working memory task 62 .…”

Brain signatures indexing variation in internal processing during perceptual decision-making

“…The similarity between trials was calculated using Pearson correlation because this is a commonly used measure to estimate the similarity. 19 The clustering utilized both spatial and temporal activity. The spatial data is represented from all EEG sensors (63 channels) and temporal activity is from stimulus onset to 500 ms post-stimulus sampled every 2 ms for a total of 63 (channels) x 251 (timepoints) = 15813 data points from each trial.…”

“…18 However, it is also possible that subsets of trials exhibit brain activity that is not well represented by the average. 19 , 20 Indeed, brain activity measured with EEG is both spatially and temporally variable during a task, with at least some of this variability likely stemming from meaningful variation in internal processing rather than simply noise. 8 , 9 , 10 , 11 Additionally, averaging across all trials might eliminate the ability to observe distinct forms of stimulus-driven activity (i.e., the ERP) that are engaged differentially on individual trials or contexts but that are, nonetheless, relevant for behavioral performance.…”

“…Here, we link trial-to-trial variation in brain activity measured with EEG and decision-making processes during a perceptual decision-making task using a data-driven classification method we developed previously. 19 Briefly, modularity-maximization identified unique stimulus-driven brain activity variation among repeated trials of a motion discrimination task. 21 To anticipate our results, modularity-maximation identified two distinct subtypes of stimulus-driven brain activity.…”