the direction of apparent motion flipped back and forth from vertical to horizontal, on average about twice per minute, even though there was no change in the stimulus itself.
After a period of adaptation to an unambiguous horizontal or vertical stimulation produced by activating a row of tactors in succession, the subjects were more likely to perceive a subsequent ambiguous stimulus as being in the orthogonal direction.
The researchers say point out that similar after-effects are common in vision, and were once thought to reflect fatigue in the brain circuits responsible for a particular perceptual interpretation, but are now thought to reflect a continual recalibration of the brain to its sensory environment.
In another experiment, an ambiguous touch stimulus was interrupted by a three-second break, after which subjects tended to experience the same direction as before the break, suggesting that the prior interpretation was somehow retained in memory and used to reinterpret the ambiguous stimulus.
The authors used their tactile illusion to explore the interaction between touch and vision, and instructed their subjects to make vertical or horizontal eye movements during the ambiguous touch stimuli.
The subjects perceived that the direction of tactile motion shifted into alignment with the direction of the eye movements, but only if the head and finger were also aligned.
Tilting the head sideways 90 degrees produced a shift to the other direction, suggesting that the tactile and visuomotor systems were somehow aligned with respect to the external world.
“We don”t yet understand what’’s happening in the brain during these illusions. But we think this illusion will be a useful new tool to understand more about the similarities between different sensory modalities and how they all work together,” says Konkle. (ANI)
Tags: biology web, braille display, brain research, christopher moore, cognitive sciences, current biology, general principles, harvard university, massachusetts institute of technology, mcgill university, postdoctoral researcher, principles of perception, qi wang, research article, square array, tactors, talia, vincent hayward, visual illusion, volunteer subjects