Article Figures & Data
Figures
- Figure 1.
Stimulus material and task design. Top left, Six tactile stimulators were attached to the distal phalanges of the index (D2), middle (D3), and ring (D4) fingers of the left and right hands. Two sample stimuli were presented simultaneously to one finger of the left and right hands. A visual retro-cue signaled which of these two stimuli had to be retained and compared with the location of a subsequent test pulse at the same hand. The cue was followed by a task-irrelevant unilateral tactile probe and task-relevant bilateral test stimuli. In the example (shown for a block with uncrossed hand posture), the retro-cue indicates that the sample stimulus on the right hand has to be memorized, and the test stimulus presented to this hand does not match the location of the sample.
- Figure 2.
ERPs elicited in response to visual retro-cues during the 1800 ms interval until the presentation of the bilateral test stimuli, at electrodes contralateral (bold lines) and ipsilateral (thin lines) to the hand specified as task relevant by the retro-cue, are shown separately for blocks with uncrossed (blue) and crossed (red) hand posture. Bottom left, The difference maps show the topographical distribution of lateralized activity in the tCDA time window (350–1600 ms after retro-cue onset) in blocks with uncrossed and crossed hands. These maps represent the amplitude difference of contralateral minus ipsilateral ERP waveforms, collapsed across trials where the left hand or right hand was relevant for the memory matching task. Bottom right, The bar graph shows contralateral minus ipsilateral difference amplitudes for the tCDA time window in blocks with uncrossed (blue) and crossed (red) hand posture. Error bars reflect 95% confidence intervals of conditional difference values tested against zero (i.e., no lateralized effect). Hand posture had no effect on tCDA amplitudes.
- Figure 3.
A, ERPs elicited by tactile probe stimuli delivered to the task-relevant hand at electrodes contralateral to this hand during the 300 ms interval after probe onset, collapsed across blocks with uncrossed and crossed hands. ERPs are shown separately for trials where a probe was presented at the same finger as the memorized sample stimulus (match trials) and trials where the probe was delivered to another finger of the same hand (mismatch trials). The somatosensory P100 component was enhanced on match trials, and the map shows the topographical distribution of this P100 modulation on the basis of difference waves obtained by subtracting ERP mean amplitudes measured in the P100 time range (80–120 ms after probe onset) on mismatch trials from ERPs on match trials. B, ERPs elicited by bilateral tactile test stimuli at electrodes contralateral to the task-relevant hand during the 300 ms interval after test onset, on match trials where the test stimulus was presented at the same finger as the memorized sample stimulus and on mismatch trials where it was delivered to another finger of the same hand. ERPs are shown separately for blocks with uncrossed and crossed hands. The somatosensory P100 component was enhanced on match trials, and this attentional modulation overlapped with the subsequent N140 component. The topographical maps show the distribution of this effect during the 80–150 ms interval after test stimulus onset. They were obtained by subtracting ERPs on mismatch trials from ERPs on match trials. Difference waves (match minus mismatch trials) show identical attentional modulations in blocks with uncrossed and crossed hands. Bar graphs show mean difference amplitudes at contralateral central electrodes. Error bars reflect 95% confidence intervals of difference values tested against zero.
