Figure 1.
Illustration of tactile stimuli used.
A. The pins' driving signal was a 144 Hz sinusoidal carrier, which was amplitude-modulated by a rectified 2 Hz sine function. B. A directed propagation of the diagonals' sine phase across the display plane resulted in a percept of a bar pattern travelling smoothly across the fingertip. Both upward and downward diagonal orientations were used corresponding to orthogonal moving directions. For moving random stimuli, each of the four sine phases was assigned to four randomly chosen pins (not shown). C. Diagonals oscillating at opposite phases created the percept of a stationary bar pattern, which was periodically elevated and retracted. Again, both diagonal orientations were used. For stationary random stimuli, the driving signals were assigned to sets of randomly chosen pins (not shown). D. The target stimulus (to be detected on infrequently presented “catch” trials) was an oscillating square.
Figure 2.
Overall neuronal network associated with tactile stimulation.
Contrasting tactile stimulation trials with null events revealed a distributed network involved in tactile information processing, including contralateral SI and bilateral SII, anterior intraparietal sulcus (aIPS), inferior frontal gyrus (IFG), lateral prefrontal cortex (LPFC), pre-supplementary motor area (pre-SMA), insular cortex, thalamus, and cerebellum. (Group-level analysis; pcluster<0.05, whole-brain FWE corr.).
Table 1.
Functional regions active during tactile stimulation.
Figure 3.
Motion- and pattern-specific differences and differential effects for motion direction and pattern orientation.
A–B. Differential effects within the network associated with tactile stimulation (shown in Figure 2). Contrasting moving with stationary trials revealed an increased BOLD response in contralateral SI and SII (A). Contrasting patterned with random stimulus trials showed an increased BOLD response in anterior superior parietal cortex (aSPC) and SI (B). Effect sizes are plotted in terms of % signal change for all four stimulus types: moving patterned (mp), moving random (mr), stationary patterned (sp), and stationary random (sr). C–D. Differential effects for motion direction and pattern orientation. The regressor for moving pattern orientation revealed directionality effects for moving patterns in SI and SII (C). Differential effects for pattern orientation of stationary patterns were found in anterior intraparietal sulcus (aIPS; D). (Group-level analysis; p<0.005, uncorr.).
Figure 4.
Areas involved in tactile motion and pattern processing.
A. Contrasting moving with stationary trials revealed an increased BOLD response in medial superior parietal cortex (not visible) and middle temporal cortex (hMT+/V5; on the left). Individual subjects' contrast estimates in hMT+/V5 correlated positively with their accuracy in identifying moving stimuli correctly (on the right). B. Contrasting patterned with random stimulus trials revealed an increased BOLD response in inferior parietal cortex (IPC; on the left). Individual subjects' contrast estimates in IPC correlated positively with their accuracy in identifying patterned stimuli correctly (on the right). A-B. Effect sizes are plotted in terms of % signal change for all four stimulus types: moving patterned (mp), moving random (mr), stationary patterned (sp), and stationary random (sr). (Group-level analysis; pcluster<0.05, whole-brain FWE corr.).
Figure 5.
Psychophysiological interaction analyses using left hMT+/V5 and left IPC as seed regions.
A. The interaction term for moving vs. stationary trials revealed a significant increase in coupling between left hMT+/V5, bilateral SI, and right anterior intraparietal sulcus (aIPS) during motion processing. B. For patterned vs. random stimulus trials, the coupling between left IPC and right SI was significantly increased. (Group-level analysis; pcluster<0.05, whole-brain FWE corr.).