Limits...
Rapid eye movements to a virtual target are biased by illusory context in the Poggendorff figure.

Melmoth D, Grant S, Solomon JA, Morgan MJ - Exp Brain Res (2015)

Bottom Line: This additional Poggendorff effect was similar in direction and magnitude for the eye movements and the perceptual responses.Latency and dynamics of the eye movements were closely similar to those recorded for a control task in which observers made a saccade from the start fixation to an explicit target on the landing line.We conclude that the neural mechanisms for extrapolation can feed into the control of eye movements without obvious penalties in timing and accuracy and that this information can instantaneously modify motor response throughout the planning phase, suggesting close association between perceptual and motor mechanisms in the process of visuo-spatial extrapolation.

View Article: PubMed Central - PubMed

Affiliation: Division of Optometry and Visual Science, City University London, London, UK.

ABSTRACT
In order to determine the influence of perceptual input upon oculomotor responses, we examined rapid saccadic eye movements made by healthy human observers to a virtual target defined by the extrapolated intersection of a pointer with a distant landing line. While corresponding perceptual judgments showed no evidence of systematic bias, eye movements showed a strong bias, in the direction of assimilation of the saccade trajectory to the shortest path between the end of the pointer and the landing line. Adding an abutting vertical inducing line to make an angle of 45 deg with the pointer led to a larger bias in the same direction as the classical Poggendorff illusion. This additional Poggendorff effect was similar in direction and magnitude for the eye movements and the perceptual responses. Latency and dynamics of the eye movements were closely similar to those recorded for a control task in which observers made a saccade from the start fixation to an explicit target on the landing line. Further experiments with inducing lines presented briefly at various times during the saccade latency period showed that the magnitude of the saccade bias was affected by inducer presentation during the saccade planning process, but not during the saccade itself. We conclude that the neural mechanisms for extrapolation can feed into the control of eye movements without obvious penalties in timing and accuracy and that this information can instantaneously modify motor response throughout the planning phase, suggesting close association between perceptual and motor mechanisms in the process of visuo-spatial extrapolation.

No MeSH data available.


Related in: MedlinePlus

Top panel of the figure shows the mean bias in experiment 1, combining results from the upward and downward conditions (u–d)/2. The colored bars (reading left to right) show results for pointer-only, motor (dark blue), pointer-only perceptual (light blue), with inducer, motor (yellow) and with inducer, perceptual (brown) conditions. Results are shown separately for each participant. Negative values on the vertical axis represent a shift in the direction of the classical Poggendorff effect. The bottom panel shows the difference (D) between the with-inducer and no-inducer conditions for motor (dark blue) and perceptual (brown) responses, in order to isolate the Poggendorff bias from the undershoot effect. Note the difference in y-axis scale between top and bottom panels (color figure online)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4464882&req=5

Fig2: Top panel of the figure shows the mean bias in experiment 1, combining results from the upward and downward conditions (u–d)/2. The colored bars (reading left to right) show results for pointer-only, motor (dark blue), pointer-only perceptual (light blue), with inducer, motor (yellow) and with inducer, perceptual (brown) conditions. Results are shown separately for each participant. Negative values on the vertical axis represent a shift in the direction of the classical Poggendorff effect. The bottom panel shows the difference (D) between the with-inducer and no-inducer conditions for motor (dark blue) and perceptual (brown) responses, in order to isolate the Poggendorff bias from the undershoot effect. Note the difference in y-axis scale between top and bottom panels (color figure online)

Mentions: We define the Poggendorff bias in the saccade as the difference in angle (deg) between the true vector from the start position to its extrapolated intersection with the landing line and the vector joining the start position to the point of regard upon the landing line following the initial saccade. The perceptual Poggendorff bias is defined similarly, using the observer’s report of the apparent point of alignment. The results for individual participants (Fig. 2) showed strong saccade direction biases in the Poggendorff direction in both the inducer-absent and inducer-present conditions. The perceptual effect was smaller than the saccade effect in all cases.Fig. 2


Rapid eye movements to a virtual target are biased by illusory context in the Poggendorff figure.

Melmoth D, Grant S, Solomon JA, Morgan MJ - Exp Brain Res (2015)

Top panel of the figure shows the mean bias in experiment 1, combining results from the upward and downward conditions (u–d)/2. The colored bars (reading left to right) show results for pointer-only, motor (dark blue), pointer-only perceptual (light blue), with inducer, motor (yellow) and with inducer, perceptual (brown) conditions. Results are shown separately for each participant. Negative values on the vertical axis represent a shift in the direction of the classical Poggendorff effect. The bottom panel shows the difference (D) between the with-inducer and no-inducer conditions for motor (dark blue) and perceptual (brown) responses, in order to isolate the Poggendorff bias from the undershoot effect. Note the difference in y-axis scale between top and bottom panels (color figure online)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4464882&req=5

Fig2: Top panel of the figure shows the mean bias in experiment 1, combining results from the upward and downward conditions (u–d)/2. The colored bars (reading left to right) show results for pointer-only, motor (dark blue), pointer-only perceptual (light blue), with inducer, motor (yellow) and with inducer, perceptual (brown) conditions. Results are shown separately for each participant. Negative values on the vertical axis represent a shift in the direction of the classical Poggendorff effect. The bottom panel shows the difference (D) between the with-inducer and no-inducer conditions for motor (dark blue) and perceptual (brown) responses, in order to isolate the Poggendorff bias from the undershoot effect. Note the difference in y-axis scale between top and bottom panels (color figure online)
Mentions: We define the Poggendorff bias in the saccade as the difference in angle (deg) between the true vector from the start position to its extrapolated intersection with the landing line and the vector joining the start position to the point of regard upon the landing line following the initial saccade. The perceptual Poggendorff bias is defined similarly, using the observer’s report of the apparent point of alignment. The results for individual participants (Fig. 2) showed strong saccade direction biases in the Poggendorff direction in both the inducer-absent and inducer-present conditions. The perceptual effect was smaller than the saccade effect in all cases.Fig. 2

Bottom Line: This additional Poggendorff effect was similar in direction and magnitude for the eye movements and the perceptual responses.Latency and dynamics of the eye movements were closely similar to those recorded for a control task in which observers made a saccade from the start fixation to an explicit target on the landing line.We conclude that the neural mechanisms for extrapolation can feed into the control of eye movements without obvious penalties in timing and accuracy and that this information can instantaneously modify motor response throughout the planning phase, suggesting close association between perceptual and motor mechanisms in the process of visuo-spatial extrapolation.

View Article: PubMed Central - PubMed

Affiliation: Division of Optometry and Visual Science, City University London, London, UK.

ABSTRACT
In order to determine the influence of perceptual input upon oculomotor responses, we examined rapid saccadic eye movements made by healthy human observers to a virtual target defined by the extrapolated intersection of a pointer with a distant landing line. While corresponding perceptual judgments showed no evidence of systematic bias, eye movements showed a strong bias, in the direction of assimilation of the saccade trajectory to the shortest path between the end of the pointer and the landing line. Adding an abutting vertical inducing line to make an angle of 45 deg with the pointer led to a larger bias in the same direction as the classical Poggendorff illusion. This additional Poggendorff effect was similar in direction and magnitude for the eye movements and the perceptual responses. Latency and dynamics of the eye movements were closely similar to those recorded for a control task in which observers made a saccade from the start fixation to an explicit target on the landing line. Further experiments with inducing lines presented briefly at various times during the saccade latency period showed that the magnitude of the saccade bias was affected by inducer presentation during the saccade planning process, but not during the saccade itself. We conclude that the neural mechanisms for extrapolation can feed into the control of eye movements without obvious penalties in timing and accuracy and that this information can instantaneously modify motor response throughout the planning phase, suggesting close association between perceptual and motor mechanisms in the process of visuo-spatial extrapolation.

No MeSH data available.


Related in: MedlinePlus