Perceptual Experience of Visual Motion Activates hMT+ Independently From the Physical Reality: fMRI Insights From the Looming Pinna Figure

The human motion processing area, hMT+, has been labeled the critical neural area for processing of real and illusory visual motion in radial 2D patterns. However, the activation in hMT+ during perception of illusory rotation in the looming double-circular Pinna Figure (PF) generated in 3D space has not been observed yet. To do so, an optic-flow like motion of rings (looming) in PF was generated on a computer screen. A psychophysically precise nulling procedure allowed quantifying the individual amount of the perceived illusory rotation in PF (PI) for each participant. The interpolation of the individual illusory motion parameters created a subjectively non-rotating PF and a physically rotating control stimulus of identical rotary strength as the PI. The physically rotating control was a double-circular figure which diverged from PF only in its arrangement of luminance gradients. In a 3-Tesla scanner, participants were presented with a random order of rotating and non-rotating figures (illusory, real, no rotation, and nulled PI). Both types, illusory and real rotation, when equal in perceptual strength for the observer, were found to be processed by hMT+.

Taylor JE, Pratt J. Frogs Jump Forward: Semantic Knowledge Influences the Perception of Element Motion in the Ternus Display

The Ternus effect is a robust illusion of motion that produces element motion at short interstimulus intervals (ISIs; <50 ms) and group motion at longer ISIs (>50 ms). Previous research has shown that the nature of the stimuli (e.g., similarity, grouping), not just ISI, can influence the likelihood of perceiving element or group motion. We examined if semantic knowledge can also influence what type of illusory motion is perceived. In Experiment 1, we used a modified Ternus display with pictures of frogs in a jump-ready pose facing forwards or backwards to the direction of illusory motion. Participants perceived more element motion with the forward-facing frogs and more group motion with the backward-facing frogs. Experiment 2 tested whether this effect would still occur with line drawings of frogs, or if a more life-like image was necessary. Experiment 3 tested whether this effect was due to visual asymmetries inherent in the jumping pose. Experiment 4 tested whether frogs in a “non-jumping,” sedentary pose would replicate the original effect. These experiments elucidate the role of semantic knowledge in the Ternus effect. Prior knowledge of the movement of certain animate objects, in this case, frogs can also bias the perception of element or group motion.

Vection can be induced in the absence of explicit motion stimuli

The present study utilized two separate experiments to demonstrate that illusory self-motion (vection) can be induced/modulated by cognition. In the first experiment, two curved lines, which simulated road edges seen while driving at night, were employed. Although the lines induced adequate strength of forward vection, when one of the lines was horizontally reversed, vection was significantly reduced. In the second experiment, two static converging lines with moving characters, which simulated side edges of a straight road with a traffic sign, were utilized. The road sign moved only during the first 5 s. After the sign disappeared, only static lines or a blank screen were able to induce vection. These results suggested that vection was largely affected by cognitive factors and that vection could be induced by implicit motion stimuli.