Fig. 1
IEM-based time-resolved reconstruction of orientation representation. a Stimuli and trial structure in the model training part. Subjects performed an orientation discrimination task at one of six orientations (15°–165° in steps of 30°, coded in different colors) that corresponded to the preferred orientation of six orientation channels. b The idealized tuning of these channels were characterized as smooth, Gaussian-like functions centered at their respective preferred orientation and plotted in the corresponding colors as in a, which spanned the entire orientation space. c Channel responses to a given orientation (e.g., 45°) could thus be predicted based on the functions. d The time-resolved decoding analysis was performed on the model training part data. The pattern of instantaneous MEG sensor signals that achieved the highest decoding accuracy (indicated by the red arrow) was extracted as the optimal orientation pattern (shown inset). Correspondence of trial-wise vectors of sensor signals (organized in columns) to the six orientations was color coded in the top row. The contribution of each orientation channel (i.e., weight) to the MEG signal from each sensor was estimated based on the optimal orientation pattern. These estimated weights were then inverted and applied to each time point to reconstruct the instantaneous channel response function at that time point, as shown in e. f The degree to which the reconstructed channel responses encoded the information of an orientation (e.g., 45°) was quantified as representation fidelity, which was calculated as the projection of the mean vector onto the direction corresponding to that orientation. g The reconstruction procedure was performed at each time point, yielding a continuous representation fidelity time course. h Time course of orientation decoding performance. i Averaged channel response functions across the six orientations with the reference channel (0°) at their respective peak orientation. Error bars denote one SEM across subjects. j Time course of orientation representation fidelity averaged across the six orientations. The gray-shaded area around the curve denotes one SEM across subjects and the red solid line indicates the time point of the highest decoding performance in h and j
