Dataset Information

The flash grab effect.

ABSTRACT: When an object moves back and forth, its trajectory appears significantly shorter than it actually is. The object appears to stop and reverse well before its actual reversal point, as if there is some averaging of location within a window of about 100 ms (Sinico et al., 2009). Surprisingly, if a bar is flashed at the physical end point of the trajectory, right on top of the object, just as it reverses direction, the flash is also shifted - grabbed by the object - and is seen at the perceived endpoint of the trajectory rather than the physical endpoint. This can shift the perceived location of the flash by as much as 2 or 3 times its physical size and by up to several degrees of visual angle. We first show that the position shift of the flash is generated by the trajectory shortening, as the same shift is seen with or without the flash. The flash itself is only grabbed if it is presented within a small spatiotemporal attraction zone around the physical end point of the trajectory. Any flash falling in that zone is pulled toward the perceived endpoint. The effect scales linearly with speed, up to a maximum, and is independent of the contrast of the moving stimulus once it is above 5%. Finally, we demonstrate that this position shift requires attention. These results reveal a new "flash grab" effect in the family of motion-induced position shifts. Although it most resembles the flash drag effect, it differs from this in the following ways: (1) it has a different temporal profile, (2) it requires attention, (3) it is about 10 times larger.

SUBMITTER: Cavanagh P

PROVIDER: S-EPMC5047291 | biostudies-literature | 2013 Oct

REPOSITORIES: biostudies-literature

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The flash grab effect.

Cavanagh Patrick P Anstis Stuart S

Vision research 20130718

When an object moves back and forth, its trajectory appears significantly shorter than it actually is. The object appears to stop and reverse well before its actual reversal point, as if there is some averaging of location within a window of about 100 ms (Sinico et al., 2009). Surprisingly, if a bar is flashed at the physical end point of the trajectory, right on top of the object, just as it reverses direction, the flash is also shifted - grabbed by the object - and is seen at the perceived end ...[more]

PMID: 23872166

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Project description:IntroductionThe endocannabinoids (eCBs), 2-arachidonoylglycerol (2-AG) and arachidonoyl ethanolamine (AEA), are produced by separate enzymatic pathways, activate cannabinoid receptors with distinct pharmacology, and differentially regulate pathophysiological processes. The genetically encoded sensor, GRABeCB2.0, detects real-time changes in eCB levels in cells in culture and preclinical model systems; however, its activation by eCB analogues produced by cells and by phyto-cannabinoids remains uncharacterized, a current limitation when interpreting changes in its response. This information could provide additional utility for the tool in in vivo pharmacology studies of phyto-cannabinoid action.MethodsGRABeCB2.0 was expressed in cultured HEK293 cells. Live cell confocal microscopy and high-throughput fluorescent signal measurements.Results2-AG increased GRABeCB2.0 fluorescent signal (EC50 = 85 nM), and the cannabinoid 1 receptor (CB1R) antagonist, SR141617, decreased GRABeCB2.0 signal (SR1, IC50 = 3.3 nM), responses that mirror their known potencies at cannabinoid 1 receptors (CB1R). GRABeCB2.0 fluorescent signal also increased in response to AEA (EC50 = 815 nM), the eCB analogues 2-linoleoylglycerol and 2-oleoylglycerol (2-LG and 2-OG, EC50s = 1.5 and 1.0 μM, respectively), Δ9-tetrahydrocannabinol (Δ9-THC) and Δ8-THC (EC50s = 1.6 and 2.0 μM, respectively), and the artificial CB1R agonist, CP55,940 (CP, EC50 = 82 nM); however their potencies were less than what has been described at CB1R. Cannabidiol (CBD) did not affect basal GRABeCB2.0 fluorescent signal and yet reduced the 2-AG stimulated GRABeCB2.0 responses (IC50 = 8.8 nM).Conclusions2-AG and SR1 modulate the GRABeCB2.0 fluorescent signal with EC50s that mirror their potencies at CB1R whereas AEA, eCB analogues, THC and CP increase GRABeCB2.0 fluorescent signal with EC50s significantly lower than their potencies at CB1R. CBD reduces the 2-AG response without affecting basal signal, suggesting that GRABeCB2.0 retains the negative allosteric modulator (NAM) property of CBD at CB1R. This study describes the pharmacological profile of GRABeCB2.0 to improve interpretation of changes in fluorescent signal in response to a series of known eCBs and CB1R ligands.

Dataset Information

The flash grab effect.

Publications

The flash grab effect.

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