Figure 2.
Neurofeedback bias score calculation. Bias scores were calculated based on the real-time decoder evidence for the two fingers adjacent to the pressed finger. Rewarded fingers are shown in green, punished fingers are shown in purple (middle finger presses: index rewarded, ring punished; ring finger presses: little rewarded, middle punished). If rewarded and punished finger evidence were equal, the bias score was 0.5. The square root of the difference between finger evidence was used as the basis of the bias score calculation. For example, with evidence of 0.75 for the rewarded finger (FR) and 0.25 for the punished finger (FP), the calculated bias score would be approximately 0.85. If the evidence for the punished finger was greater than the evidence for the rewarded finger, the bias score was less than 0.5 [i.e., if the sign (sgn) of the difference between rewarded and punished fingers was negative]. The heatmap of bias scores only includes possible decoder output combinations: the four-finger SMLR decoder could output four possible values, which must sum to 1. Therefore, the sum of the evidence of two fingers could never exceed 1. SMLR, sparse multinomial logistic regression.