According to recent evidence, stimulus-tuned neurons in the cerebral cortex exhibit reduced variability in firing rate across trials, after the onset of a stimulus. However, in order for a reduction in variability to be directly relevant to perception and behavior, it must be realized within trial-the pattern of activity must be relatively stable. Stability is characteristic of decision states in recurrent attractor networks, and its possible relevance to conscious perception has been suggested by theorists. However, it is difficult to measure on the within-trial time scales and broadly distributed spatial scales relevant to perception. We recorded simultaneous magneto-and electroencephalography (MEG and EEG) data while subjects observed threshold-level visual stimuli. Pattern-similarity analyses applied to the data from MEG gradiometers uncovered a pronounced decrease in variability across trials after stimulus onset, consistent with previous single-unit data. This was followed by a significant divergence in variability depending upon subjective report (seen/ unseen), with seen trials exhibiting less variability. Applying the same analysis across time, within trial, we found that the latter effect coincided in time with a difference in the stability of the pattern of activity. Stability alone could be used to classify data from individual trials as "seen" or "unseen." The same metric applied to EEG data from patients with disorders of consciousness exposed to auditory stimuli diverged parametrically according to clinically diagnosed level of consciousness. Differences in signal strength could not account for these results. Conscious perception may involve the transient stabilization of distributed cortical networks, corresponding to a global brain-scale decision.correlated variability | consciousness | dynamical systems | pattern similarity | directional variance R ecent evidence suggests that population neuronal activity in stimulus-tuned regions of cortex is reliably drawn to the same region of state space in response to a stimulus (1). Churchland et al. (1) analyzed recordings from many different areas of monkey cortex, under a variety of different task conditions, and found a common decrease in intertrial firing-rate variability beginning just after stimulus onset. At the macroscopic level, intertrial variability of the pattern of activity, measured using functional MRI (fMRI), is reduced immediately following stimulus onset (2) and has been shown to correlate with perception (3) and explicit recognition memory (4). However, to be relevant for decision making and behavior, a reduction in variability must be realized within trial, in the form of a stable pattern of activity.Both stability (within episode) and reproducibility (between episodes) are characteristic of decision states in recurrent attractor networks: When presented with a learned input pattern of sufficient intensity, the activity within the network will evolve from an arbitrary initial state toward a relatively low-energy stable state that can ...

HighlightsWe used a continuous performance measure VSTM in children aged between 7 and 12.This was combined with a probabilistic mixture model.Older children were more likely to remember the target, but were no more precise.Mixture model parameters corresponded to differences in standardized WM and STM.

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