Example predictive models and prediction errors.

The inset figure has two panels. The first panel gives the relative size and spacing of the measurement arrays for two subjects. The three axes are ‘AP’: anterior-posterior; ‘IS’: inferior-superior; ‘LR’: left-right. A typical phase gradient is shown in colour from the scalar values of phase. The second panel shows the distributions of estimated spatial frequency of the measured phase, over all trials and samples for the subject. The distribution of estimated spatial frequency of phase gradients (see Methods) is shown for all samples in grey. The figure is composed by overlay of samples drawn from the top third of prediction accuracy (red), middle third (green), and lower third (blue). Since selection by prediction accuracy does not alter the distribution, the combined plot is mostly grey. The main figure is broken into five panels. The first four panels show the past phase (as a head map and on the complex plane), the past model phase, the model prediction of the future phase, the actual future phase. For the past phase and future phase panels, head maps are shown in the centre of the panel, with unit circle of phase surrounding. The colours are used to represent phase in both head and circle, and phase is reiterated as angular position on the unit phase circle. For the past model and model prediction, the model output is shown on the complex plane in the centre of the panel. The argument of the model phase i.e. the angle, is shown in colours here and on the model head map (top left of these two panels). The site to be predicted is indicated with a black circle in both the model prediction panel and the future phase panel. These two example predictions are built using only the first eigenvector from the PCA, and therefore the second and third panels illustrate that eigenvector. Upper row: Subject MEG 6, centre frequency 2.0Hz, to-be-predicted site left out of past model. The letters ‘A’, ‘P’, ‘I’, ‘S’, ‘L’, ‘R’ indicate the position of the anterior-most (posterior-most etc.) recording site on either the head map or the unit circle of phase. The site to be predicted is missing from the past model representation, on the bottom row of sensors, just to the right of the ‘L’ sensor. This snapshot is taken during the third trial, at 364ms. See S1 Video, for the first three trials of this subject. Lower row: Subject ECoG 1, centre frequency 6.7Hz. The letters ‘A1’, ‘A8’, ‘H1’, ‘H8’ indicate the labels and positions of the corner recording sites of the ECoG array. The site to be predicted is missing from the past model representation, in position ‘B6’ i.e. one column in from the left, three rows down. This snapshot is taken during the first trial, at -250ms. See S2 Video, for the first three trials of this subject. In the fifth panel (lower right of figure), the mean prediction error is shown with a black arrow for Subject MEG 6 at 354ms, 2.0Hz (upper) and Subject ECoG 1 at -250ms, 6.7Hz (lower). The prediction errors are for a specific site, chosen as the to-be-predicted site during the model construction phase. The phase locking value (PLV) is the real part (i.e. the length of this arrow along the x-axis), here, 0.58 and 0.64 respectively. The prediction errors for each individual trial are also shown with coloured crosses, hot colours are trials with high mean log power, cold colours with low. The prediction error for the trial shown in Fig 1 is indicated with a black cross.