Figure 1. Structures of the 16 DCM model families (A–P). In all model families, four intrinsic connections were defined. These intrinsic connections are indicated by the black lines with arrows, and the arrows indicate the direction of the connectivity. The 16 model families differ in terms of how the connections between the thalamus and S1 and between the thalamus and S2 are modulated (i.e., whether each of the two connections are modulated by non-nociceptive stimuli, by nociceptive stimuli, by both stimuli, or by neither of them). These modulations are indicated by the black dashed lines. The color of the vertical lines at the end of the dashed lines indicates the modality of the stimuli that exert the modulatory effect. Each model family contains 16 single models (data not shown) that differ in how the connections between S1 and S2 are modulated. Therefore, 256 models in total (16 models × 16 families) were defined in the present study. The thalamus was set as the receiving area, and the driving input to the thalamus was formed by all stimuli regardless of their modality. These stimuli are represented by vertical lines with different colors indicating different sensory modalities (red, nociceptive; blue, non-nociceptive; green, auditory; purple, visual). S1, Primary somatosensory cortex; S2, secondary somatosensory cortex; TH, thalamus.