Motion-Induced Scotoma

Abstract

We investigated artificial scotomas created when a moving object instantaneously crossed a gap, jumping ahead and continuing its otherwise smooth motion. Gaps of up to 5.1 degrees of visual angle, presented at 18º eccentricity, either closed completely or appeared much shorter than when the same gap was crossed by two-point apparent motion, or crossed more slowly, mimicking occlusion. Prolonged exposure to motion trajectories with a gap in most cases led to further shrinking of the gap. The same gapshrinking effect has been observed in touch (Seizova-Cajic & Taylor, 2014). In both sensory modalities, it implicates facilitation among co-directional local motion detectors and motion neurons with receptive fields larger than the gap. Unlike stimuli that simply deprive a receptor surface of input, suggesting it is insentient, our motion pattern skips a section in a manner that suggests a portion of the receptor surface has been excised and the remaining portions stitched back together. This makes it a potentially useful tool in the experimental study of plasticity in sensory maps.

Scrambling the skin: A psychophysical study of adaptation to scrambled tactile apparent motion

“…Qualitative data (see Fig 7) and the drawings show that the two conditioning patterns were similarly perceived: the participants felt motion up and down the forearm, mostly along a straight line. A variety of tactile and visual spatiotemporal patterns containing sudden accelerations are misperceived such that the percept tends to be smoother than the stimulus patterns [6,7,21,22]. Vision research shows that transient changes in the motion sequence such as gaps in the trajectory or changes in colour or shape of the moving object are imperceptible provided they do not occur too early in the motion sequence [23].…”

“…In subsequent research, timing has usually been conceptualized and operationalized as temporal coincidence or neural co-activation (see [3][4][5]), although motion across the receptor surface is a better candidate for the general organizing principle of spatial maps (its importance was recently emphasized in [6][7][8]). It is a ubiquitous form of natural stimulation and, importantly, unlike simultaneous (coincident) stimulation, it cannot lead to 'fusion' of skin parts that often touch each other, such as lips or fingers.…”

Scrambling the skin: Simulated Skin Re-Arrangement Using Apparent Motion

“…7) and the drawings show that the two conditioning patterns were similarly perceived: the participants felt motion up and down the forearm, mostly along the straight line. A variety of tactile and visual spatiotemporal patterns containing sudden accelerations are misperceived such that percept tends to be smoother than the stimulus patterns [8,9,20,21]. Vision research also shows that transient changes in the motion sequence such as gaps in the trajectory or changes in colour or shape of the moving object are imperceptible provided they do not occur too early in the motion sequence [22].…”

“…Motion is a very strong candidate for the experience-dependent map organization because locations next to each other on a sensory surface are stimulated one after the other by moving objects, and can thus learn that they are neighbours. The idea is illustrated in Fig 1 (and was previously described in [8,9]). Although quite simple and old (Lotze, 19 th C, cited in Herrnstein and Boring, 1965), it has attracted surprisingly little research and has little direct evidence to support it (to our knowledge, none in humans).…”

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“…In subsequent research, timing has usually been conceptualized and operationalized as temporal coincidence or neural co-activation (see [3][4][5]), although motion across the receptor surface is a better candidate for the general organizing principle of spatial maps (its importance was recently emphasized in [6][7][8]). It is a ubiquitous form of natural stimulation and, importantly, unlike simultaneous (coincident) stimulation, it cannot lead to 'fusion' of skin parts that often touch each other, such as lips or fingers.…”