Concomitant Synaptic Modulations Can Exacerbate or Rescue Imbalances. A-F) Changes to optimal network balance are shown for each permutation of simultaneous changes in two of the four synaptic properties. Grayscale values illustrate increases in max error rate relative to the optimal networks. Optimal networks are central in the 2D plots, bordered with a black box. Increasing max error rates resulting from alterations to single parameters are seen in the vertical or horizontal deviations from the optimal networks, while the remainder of each plot shows the effects of concomitant alterations to both parameters. Examples of pathological shifts towards intolerable pattern completion error (separation performance bias, red circles), or pathological shifts towards intolerable pattern separation error (completion performance bias, blue circles) are highlighted for individual synaptic pathologies. Error rates for these highlighted data points are shown, with pale red and blue bars illustrating completion and separation error rates within tolerable limits defined by optimal network performance. Completion or separation error rates exceeding tolerable limits are illustrated with dark red or dark blue, respectively. For each highlighted pathology, examples of therapeutic shifts towards more tolerable error rates that could be achieved by manipulating the other synaptic property are shown with red arrowheads (amelioration of separation biases) or blue arrowheads (amelioration of completion biases). Note that while increases in connectivity are included for completeness, that upper limits are likely biologically constrained, limiting the plausibility of the low error regions of parameter space seen with high connectivity (see text).