Variation of haemodynamic responses with changes in (from baseline 40 mmHg) and blood pressure (baseline 100 mmHg). In the upper 3D graphs, responses are shown for simultaneous changes in both inputs. (Note the axis for in these plots increases from right to left.) The 2D graphs in the middle row show effects of changing and alone. Shaded regions indicate where a false identification results when using a simple distance-based classifier. At the bottom, results from the same classifier are shown for both factors varying jointly over their ranges, with colour indicating the strength of the classification. A Systemic factors were varied with no change in metabolic demand. False positive responses (magenta in the bottom plot) occurred in the region of reduced pressure and increased . They could be produced by changes alone, but not by pressure. B Metabolic demand was increased at the same time as the systemic changes, shifting the response upwards and the HHb downwards. False negatives (cyan in the bottom plot) occurred across a wide range of combinations, but especially with reduced and increased pressure. They could also arise from changes in either factor alone.