Limits...
Ocular accommodation and cognitive demand: an additional indicator besides pupil size and cardiovascular measures?

Jainta S, Hoormann J, Jaschinski W - J Negat Results Biomed (2008)

Bottom Line: Heart period, pulse transit time, and the pupillary response were considered as reference for possible closed-loop accommodative effects.An observed decrease in accommodation could not be attributed to the cognitive demand itself for two reasons: (1) the cognitive demand induced a shift in gaze direction which, for methodological reasons, accounted for a substantial part of the observed accommodative changes. (2) Remaining effects disappeared when the correctness of task processing was taken into account.Although the expectation of accommodation as possible autonomic indicator of cognitive demand was not confirmed, the present results are informative for the field of applied psychophysiology noting that it seems not to be worthwhile to include closed-loop accommodation in future studies.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut fuer Arbeitsphysiologie an der Universitaet Dortmund, Ardeystrasse 67, D-44139, Dortmund, Germany. jainta@ifado.de

ABSTRACT

Background: The aim of the present study was to assess accommodation as a possible indicator of changes in the autonomic balance caused by altered cognitive demand. Accounting for accommodative responses from a human factors perspective may be motivated by the interest of designing virtual image displays or by establishing an autonomic indicator that allows for remote measurement at the human eye. Heart period, pulse transit time, and the pupillary response were considered as reference for possible closed-loop accommodative effects. Cognitive demand was varied by presenting monocularly numbers at a viewing distance of 5 D (20 cm) which had to be read, added or multiplied; further, letters were presented in a "n-back" task.

Results: Cardiovascular parameters and pupil size indicated a change in autonomic balance, while error rates and reaction time confirmed the increased cognitive demand during task processing. An observed decrease in accommodation could not be attributed to the cognitive demand itself for two reasons: (1) the cognitive demand induced a shift in gaze direction which, for methodological reasons, accounted for a substantial part of the observed accommodative changes. (2) Remaining effects disappeared when the correctness of task processing was taken into account.

Conclusion: Although the expectation of accommodation as possible autonomic indicator of cognitive demand was not confirmed, the present results are informative for the field of applied psychophysiology noting that it seems not to be worthwhile to include closed-loop accommodation in future studies. From a human factors perspective, expected changes of accommodation due to cognitive demand are of minor importance for design specifications - of, for example, complex visual displays.

Show MeSH

Related in: MedlinePlus

Gaze direction measurements. Measured horizontal gaze direction (deg; mean ± SD) as a function of presented horizontal position (deg) for the PowerRefractor and PowerRef II. Regression equations are shown separately. As indicated by the slope of the regression equations, the distance between the presented horizontal positions was underestimated by the measured gaze direction, even though the measurement distance of 1 m was correctly maintained; maybe the Hirschberg ratio set by the default routine was to low for our sample.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2542343&req=5

Figure 8: Gaze direction measurements. Measured horizontal gaze direction (deg; mean ± SD) as a function of presented horizontal position (deg) for the PowerRefractor and PowerRef II. Regression equations are shown separately. As indicated by the slope of the regression equations, the distance between the presented horizontal positions was underestimated by the measured gaze direction, even though the measurement distance of 1 m was correctly maintained; maybe the Hirschberg ratio set by the default routine was to low for our sample.

Mentions: The direction of gaze may affect the measured refraction value without any change in curvature of the lens [15-17]. In order to quantify this possible measurement artefact, we presented small targets (0.16 deg × 0.16 deg) at 9 horizontal gaze positions to the right eye at eye level. The total range of presentation was ± 2 deg with gaps between each gaze position of 0.5 deg. Refraction and gaze direction were measured monocularly for 10 subjects with the PowerRefractor and for 15 subjects with the PowerRef II (subject pool described above). Each gaze position was fixated for 2 s and refraction and gaze direction were sampled with 25 Hz; for analysis we extracted the medial second of each stable fixation by cutting off the first and last 500 ms. The measured gaze positions reflected the presented gaze positions (see Figure 8); the deviation of both regression lines along the y-axes reflected a mean difference in the position of the two cameras (PowerRefractor/PowerRef II); both cameras were fixed in 1 m distance – relative to the right eye. Additionally, the stimulus range of ± 2 deg was not completely reflected by the measured data.


Ocular accommodation and cognitive demand: an additional indicator besides pupil size and cardiovascular measures?

Jainta S, Hoormann J, Jaschinski W - J Negat Results Biomed (2008)

Gaze direction measurements. Measured horizontal gaze direction (deg; mean ± SD) as a function of presented horizontal position (deg) for the PowerRefractor and PowerRef II. Regression equations are shown separately. As indicated by the slope of the regression equations, the distance between the presented horizontal positions was underestimated by the measured gaze direction, even though the measurement distance of 1 m was correctly maintained; maybe the Hirschberg ratio set by the default routine was to low for our sample.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2542343&req=5

Figure 8: Gaze direction measurements. Measured horizontal gaze direction (deg; mean ± SD) as a function of presented horizontal position (deg) for the PowerRefractor and PowerRef II. Regression equations are shown separately. As indicated by the slope of the regression equations, the distance between the presented horizontal positions was underestimated by the measured gaze direction, even though the measurement distance of 1 m was correctly maintained; maybe the Hirschberg ratio set by the default routine was to low for our sample.
Mentions: The direction of gaze may affect the measured refraction value without any change in curvature of the lens [15-17]. In order to quantify this possible measurement artefact, we presented small targets (0.16 deg × 0.16 deg) at 9 horizontal gaze positions to the right eye at eye level. The total range of presentation was ± 2 deg with gaps between each gaze position of 0.5 deg. Refraction and gaze direction were measured monocularly for 10 subjects with the PowerRefractor and for 15 subjects with the PowerRef II (subject pool described above). Each gaze position was fixated for 2 s and refraction and gaze direction were sampled with 25 Hz; for analysis we extracted the medial second of each stable fixation by cutting off the first and last 500 ms. The measured gaze positions reflected the presented gaze positions (see Figure 8); the deviation of both regression lines along the y-axes reflected a mean difference in the position of the two cameras (PowerRefractor/PowerRef II); both cameras were fixed in 1 m distance – relative to the right eye. Additionally, the stimulus range of ± 2 deg was not completely reflected by the measured data.

Bottom Line: Heart period, pulse transit time, and the pupillary response were considered as reference for possible closed-loop accommodative effects.An observed decrease in accommodation could not be attributed to the cognitive demand itself for two reasons: (1) the cognitive demand induced a shift in gaze direction which, for methodological reasons, accounted for a substantial part of the observed accommodative changes. (2) Remaining effects disappeared when the correctness of task processing was taken into account.Although the expectation of accommodation as possible autonomic indicator of cognitive demand was not confirmed, the present results are informative for the field of applied psychophysiology noting that it seems not to be worthwhile to include closed-loop accommodation in future studies.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut fuer Arbeitsphysiologie an der Universitaet Dortmund, Ardeystrasse 67, D-44139, Dortmund, Germany. jainta@ifado.de

ABSTRACT

Background: The aim of the present study was to assess accommodation as a possible indicator of changes in the autonomic balance caused by altered cognitive demand. Accounting for accommodative responses from a human factors perspective may be motivated by the interest of designing virtual image displays or by establishing an autonomic indicator that allows for remote measurement at the human eye. Heart period, pulse transit time, and the pupillary response were considered as reference for possible closed-loop accommodative effects. Cognitive demand was varied by presenting monocularly numbers at a viewing distance of 5 D (20 cm) which had to be read, added or multiplied; further, letters were presented in a "n-back" task.

Results: Cardiovascular parameters and pupil size indicated a change in autonomic balance, while error rates and reaction time confirmed the increased cognitive demand during task processing. An observed decrease in accommodation could not be attributed to the cognitive demand itself for two reasons: (1) the cognitive demand induced a shift in gaze direction which, for methodological reasons, accounted for a substantial part of the observed accommodative changes. (2) Remaining effects disappeared when the correctness of task processing was taken into account.

Conclusion: Although the expectation of accommodation as possible autonomic indicator of cognitive demand was not confirmed, the present results are informative for the field of applied psychophysiology noting that it seems not to be worthwhile to include closed-loop accommodation in future studies. From a human factors perspective, expected changes of accommodation due to cognitive demand are of minor importance for design specifications - of, for example, complex visual displays.

Show MeSH
Related in: MedlinePlus