Intracortical microstimulation of human somatosensory cortex induces natural perceptual biases

The study investigates how the timing between stimuli affects perception using intracortical microstimulation (ICMS) in the somatosensory cortex of humans with spinal cord injuries. Participants performed tasks to compare the intensity of two stimuli and estimate the magnitude of a single stimulus after another. The results showed that the perceived intensity of a stimulus is influenced by the preceding stimulus and the time interval between them. These findings suggest that time-order errors, where the order of stimuli affects perception, can occur even with direct stimulation of the somatosensory cortex, indicating that higher-level brain regions play a significant role.

• 1
  Systematic biases were observed in amplitude discrimination tasks, with the intensity of the second stimulus often overestimated, and the degree of overestimation depended on perceptual sensitivity.
• 2
  In magnitude estimation tasks, the perceptual intensity of the second stimulus was enhanced by the first, depending on the amplitude and duration of the first stimulus.
• 3
  Longer inter-stimulus intervals reduced the effect size in both amplitude discrimination and magnitude estimation tasks, suggesting a time-dependent integration mechanism.