Article Figures & Data
Figures
- Figure 1.
Task design. A, Trial types. Subjects were asked to perform congruent (top) and incongruent (bottom) trials requiring left (left) or right (right) finger responses according to an imperative stimulus consisting of a central arrow (target) surrounded by two irrelevant arrows on each side (flankers). B, Time course of a typical trial. Each trial started with the presentation of five black squares remaining on the screen for 7000 ms (top left). Then, the imperative stimulus appeared (top right), indicating the required response (right key-press in current example). Once a response was provided (or after 700 ms), a mask appeared and remained on the screen for an interval of 1200 ms (bottom right). A feedback score was then displayed for 1500 ms depending on the subject RT and accuracy (bottom left). C, Block types. The experiment involved two block types, including either a majority of congruent trials (MCB; left) or a majority of incongruent trials (MIB; right). Conflict expectation was highest in the latter block type. D, SSVEP procedure. In half of the blocks, the stimuli were slightly shifted to the left (left), whereas they were slightly shifted to the right in the other blocks (right). The target square (TargetSq) appeared on the left of the fixation cross in left-shifted stimuli and on the right of it in right-shifted stimuli; it was flickering at 16.6 Hz. The most central flanker square (Flanker-CSq) was flickering at 12.5 Hz; it was always the one located on the other side of the fixation point. The three more peripheral flanker squares (Flanker-PSq) were flickering at 14.2 Hz.
- Figure 2.
EEG data processing steps. A, Attention epochs: SSVEP. (1) For each subject, multiple z scored spectra were obtained (i.e., in 4 conditions and 64 electrodes). Typical single-subject spectra are represented, showing three SSVEP peaks at 12.5, 14.2, and 16.6 Hz. (2) The spectra obtained at electrodes of a posterior ROI (ROIPost) were exploited to compute linear channel maps. (3) A cluster-based statistical analysis was applied on the maps to test for any significant effect of the factors of interest (i.e., hemisphere and context) on the spectral amplitude among the frequency and scalp location dimensions. B, Selection epochs: RLP. (1) For each subject, multiple RLPs were obtained (in μV/m2; i.e., in 16 conditions and 64 electrodes). Typical single-subject potentials are represented. (2) The potentials obtained at electrodes of a central ROI (ROICentral) were exploited to compute channel maps. (3) A cluster-based statistical analysis was applied on the maps to test for any significant effect of the factors of interest (e.g., trial [congruent, incongruent], context [MCB, MIB]) on the potential amplitude among the time and scalp location dimensions.
- Figure 3.
Accuracy (A–C) and RT (D–F). Data are mean ± SE. A, D, The hand factor significantly impacted the accuracy and RT data. Green and blue colors represent data obtained for left and right hand responses, respectively. Both trial types and contexts are pooled together. B, E, The trial factor had a significant influence on the accuracy and RT data. Both hands and contexts are pooled together. C, F, The trial × context interaction was significant. Both hands are pooled together. *Significant difference at p < 0.05.
- Figure 4.
Effect of conflict expectation on midfrontal theta activity. A, The cluster-based statistical analysis revealed that ΔSpectPower, a marker of theta activity due to conflict expectation, was significantly different from 0 for a cluster of data points in the theta range. B, Grand-average TF maps were obtained for the Fpz (top), Fz (middle), and Cz (bottom) electrodes. For illustrative purposes, maps were resampled by multiplying temporal and frequency resolutions by a factor of 10. Rectangle (black dotted lines) represents the significant cluster on each map: note the significantly higher ΔSpectPower for the midfrontal Fz electrode specifically (absence of effect for the two other electrodes). C, Grand-average topography was obtained using the time-frequency boundaries of the detected cluster to extract the values at each electrode: 4700 ms, 5400 ms/6 Hz, 8 Hz. D, Post hoc results show the larger ΔSpectPower for Fz compared with Fpz and Cz. Time-frequency boundaries used to extract the cluster-level average values in each subject are the same as in C. Bar graphs indicate group-level mean ± SE. *Significant difference at p < 0.05.
- Figure 5.
Effect of the factor hemisphere on SSVEPs. A, The cluster-based statistical analysis revealed a significant main effect of hemisphere on two clusters of data points (red). B, Effect of hemisphere at the Flanker-CSq frequency. Top, Grand-average channel maps as obtained for HEMIContra-to-Target (left) and HEMIIpsi-to-Target (right; ipsilateral and contralateral to the Flanker-Csq, respectively). The ROIPost locations (2–5) showing a significant hemisphere effect are comprised in the rectangles (black dotted lines). Bottom left, Grand-average frequency spectra (all electrodes composing the cluster pooled together) as obtained for the HEMIContra-to-Target (solid line) and HEMIIpsi-to-Target (dashed line). Gray rectangle represents the frequency window of statistical significance. *Significant difference at p < 0.05. Bottom right, Grand-average topographies at 12.5 Hz for left- and right-shifted stimuli (left and right topographies, respectively). *The electrode composing the detected cluster. C, Same as B for the TargetSq frequency.
- Figure 6.
Effect of the factor context on SSVEPs. A, The cluster-based statistical analysis revealed a significant main effect of context on two clusters of data points (red). B, SSVEP amplitude in MCB (orange) and MIB (red) blocks. Top left, Grand-average channel maps as obtained for MCBs and MIBs. The ROIPost locations (1–3) showing a significant effect of the factor context at the Flanker-PSq frequency are comprised in the rectangles (black dotted lines). Top right, Grand-average frequency spectra (all electrodes composing the cluster pooled together) as obtained for the MCBs (orange) and MIBs (red). There is higher Flanker-PSq-related SSVEPs in MIBs compared with MCBs. Gray rectangle represents the frequency window of statistical significance. *Significant difference at p < 0.05. Bottom, Grand-average topographies at 14.2 Hz for left- and right-shifted stimuli (left and right topographies, respectively). *The electrode composing the detected cluster.
- Figure 7.
Effect of the hemisphere × context × time interaction on SSVEPs. A, The cluster-based statistical analysis revealed a significant hemisphere × context × time interaction on a cluster of data points (red). B, StageEarly. Top, Grand-average channel maps as obtained for HEMIContra-to-Target (left) and HEMIIpsi-to-Target (right), in MCBs (top) and MIBs (bottom). The ROIPost locations (4–5) showing a significant hemisphere × context × time interaction are comprised in the rectangles (black dotted lines). Bottom left, Grand-average frequency spectra as obtained for the HEMIContra-to-Target (solid line) and HEMIIpsi-to-Target (dashed line), in MCBs (orange) and MIBs (red). The frequency spectra measured at the electrodes composing the detected cluster were averaged together. Gray rectangle represents the frequency window of statistical significance. *Significant difference at p < 0.05. Bottom right, Grand-average topographies at 16.6 Hz for left- and right-shifted stimuli (left and right topographies, respectively). *The electrode composing the detected cluster. C, Same as B for StageLate. *Significant difference at p < 0.05.
- Figure 8.
Effect of the factor hemisphere on RLPs. A, The cluster-based statistical analysis revealed a significant main effect of the hemisphere factor on two clusters of data points (red). B, Top, Grand-average channel maps as obtained for HEMIContra-to-Resp (left) and HEMIIpsi-to-Resp (right). The ROICentral locations showing a significant effect of hemisphere are comprised in the rectangles (black dotted lines). Bottom left, Grand-average RLP waveforms as obtained for the HEMIContra-to-Resp (solid line) and HEMIIpsi-to-Resp (dashed line). The RLPs measured at the electrodes composing the two detected clusters were averaged separately; that is, ROICentral_1 and ROICentral_2 were exploited to compute the left segment of the RLP (from −500 ms to −150 ms) while the averaging for the right segment also involved ROICentral_3 (from −150 to −50 ms). Gray rectangles represent the time windows of statistical significance. *Significant difference at p < 0.05. Bottom right, Grand-average topographies at −250 ms and −100 ms (left and right topographies, respectively) for left hand responses. *The electrode composing the detected cluster.
- Figure 9.
Effect of the hemisphere × hand × trial interaction on RLPs. A, The cluster-based statistical analysis revealed a significant main effect of the hemisphere × hand × trial interaction on a cluster of data points (red). B, Left, Grand-average channel maps as obtained for congruent trials, for left (top row) and right (bottom row) hand responses, in HEMIContra-to-Resp (left column) and HEMIIpsi-to-Resp (right column). The ROICentral location showing a significant hemisphere × hand × trial interaction is comprised in the rectangles (black dotted lines). Right, Same as B. Left, Incongruent trials. C, Left, Grand-average RLP waveforms as obtained for congruent (left column) and incongruent (right column) trials, for left (top row; green) and right (bottom row; blue) responses, in the HEMIContra-to-Resp (solid lines) and HEMIIpsi-to-Resp (dashed lines). The RLP waveform measured at the electrode composing the detected cluster was extracted for each condition. Gray rectangle represents the time window of statistical significance. *Significant difference at p < 0.05. Right, The same RLP waveforms as the ones represented in C. Left, Exploited to highlight the significant differences in RLP amplitude for left and right responses in incongruent trials. RLPs obtained in the HEMIContra-to-Resp and HEMIIpsi-to-Resp are represented at top and bottom rows, respectively. D, Grand-average topographies for congruent (left; obtained at −250 ms) and incongruent (right; at −200 ms) trials. For each trial type, topographies for both hand responses are represented. *The electrode composing the detected cluster.
- Figure 10.
Effect of the hemisphere × trial × context interaction on RLPs. A, The cluster-based statistical analysis revealed a significant main effect of the hemisphere × trial × context interaction on a cluster of data points (red). B, Left, Grand-average channel maps as obtained for congruent trials, for MCB (top row) and MIB (bottom row) contexts, in HEMIContra-to-Resp (left column) and HEMIIpsi-to-Resp (right column). The ROICentral location showing a significant hemisphere × trial × context interaction is comprised in the rectangles (black dotted lines). Right, Same as B. Left, Incongruent trials. C, Left, Grand-average RLP waveforms as obtained for congruent (left column) and incongruent (right column) trials, for MCB (top row; orange) and MIB (bottom row; red) contexts, in the HEMIContra-to-Resp (solid lines) and HEMIIpsi-to-Resp (dashed lines). The RLP waveforms measured at the electrodes composing the detected cluster were averaged together for each condition. Gray rectangle represents the time window of statistical significance. *Significant difference at p < 0.05. Right, The same RLP waveforms as the ones represented in C (left) were exploited to highlight the significant differences in RLP amplitude in the HEMIIpsi-to-Resp between MCB and MIB contexts in incongruent trials. RLPs obtained in the HEMIContra-to-Resp and HEMIIpsi-to-Resp are represented at top and bottom rows, respectively. D, Grand-average topographies obtained at −230 ms for congruent (left) and incongruent (right) trials. For each trial type, topographies for both hand responses and both contexts are represented. *The electrodes composing the detected cluster.
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