Guiding the study of brain dynamics by using first-person data: synchrony patterns correlate with ongoing conscious states during a simple visual task - PubMed (original) (raw)

Guiding the study of brain dynamics by using first-person data: synchrony patterns correlate with ongoing conscious states during a simple visual task

Antoine Lutz et al. Proc Natl Acad Sci U S A. 2002.

Abstract

Even during well-calibrated cognitive tasks, successive brain responses to repeated identical stimulations are highly variable. The source of this variability is believed to reside mainly in fluctuations of the subject's cognitive "context" defined by his/her attentive state, spontaneous thought process, strategy to carry out the task, and so on... As these factors are hard to manipulate precisely, they are usually not controlled, and the variability is discarded by averaging techniques. We combined first-person data and the analysis of neural processes to reduce such noise. We presented the subjects with a three-dimensional illusion and recorded their electrical brain activity and their own report about their cognitive context. Trials were clustered according to these first-person data, and separate dynamical analyses were conducted for each cluster. We found that (i) characteristic patterns of endogenous synchrony appeared in frontal electrodes before stimulation. These patterns depended on the degree of preparation and the immediacy of perception as verbally reported. (ii) These patterns were stable for several recordings. (iii) Preparatory states modulate both the behavioral performance and the evoked and induced synchronous patterns that follow. (iv) These results indicated that first-person data can be used to detect and interpret neural processes.

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Figures

Figure 1

Figure 1

(I) Protocol. Tasks: (A) Fixation of the center of the screen; (B) fusion of the two dots and refixation of the center of the screen; (C) motor response; and (D) phenomenological report. Events: (1) Presentation of an image without binocular disparities; (2) auditory warning at the beginning of B; (3) presentation of the autostereogram. (II) Reaction times. Mean reaction times between (3) and the motor response (D) with two standard errors. PhCs: SR and SR′, FR, SU, and SIU. (III) Evoked oscillatory responses. For each subject and each PhC, time-frequency power of evoked potential was normalized compared with baseline B1 and average across electrodes, time intervals [50, 150 ms], and frequencies (20–64 Hz).

Figure 2

Figure 2

DNS for S1 during readiness with immediate perception SR (154 trials) and SU with surprise during stimulation (38 trials). Color coding indicates scalp distribution of time-frequency gamma power around 35 Hz normalized compared with distant baseline B0 average for trials and for time windows indicated by an arrow. In prepared trials, gamma power in frontal electrodes (FP1-FT8) during B1 increased significantly (P < 0.01) compared with distant baseline B0 and was significantly higher (P < 0.005) than in the unprepared trials. Black and white lines correspond to significant increase and decrease in synchrony, respectively. For each pair of electrodes, the density of long-distance synchrony above a surrogate threshold was calculated (see Statistics). This measure was normalized compared with the distribution for trials in baseline B0. A significant threshold was estimated with white-noise surrogates (35).

Figure 3

Figure 3

Correlation between first-person data and time-frequency power emission. For each subject and PhC, spectral distribution of power emission was normalized compared with the activity for trials in B0 and averaged in time window B1 and for selected frontal electrodes

Figure 4

Figure 4

Mean induced oscillatory responses for all subjects and PhCs in occipitoparietal electrodes in gamma frequency band normalized compared with B1. Error bars represents one standard error (see Statistics).

Figure 5

Figure 5

Stability of DNSs for recordings for S1 during SR in frontal electrodes (FP1 to FT8) with significant increase at 36 Hz and decrease between [44–64 Hz] during B1 for every recording (59, 60, and 35 trials, respectively) (see Results). S1 reported to be globally less focused during the third recording than during the second one. Color coding indicates scalp distribution of time-frequency gamma power normalized compared with distant baseline B0 averaged for trials and electrodes.

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