FREE ELECTRONIC LIBRARY - Dissertations, online materials

Pages:     | 1 | 2 || 4 | 5 |   ...   | 6 |

«Published in final edited form in: European Journal of Neuroscience. (2013) doi: dx.doi.org/10.1111/ejn.12324 Gaze direction affects linear ...»

-- [ Page 3 ] --

Ni, J., Tatalovic, M., Straumann, D., Olasagasti, I. (2013) Gaze direction affects linear self-motion heading discrimination in humans. European Journal of Neuroscience. doi: dx.doi.org/10.1111/ejn.12324 were not statistically significant (  3 = 7.68, n = (10, 7, 7, 14), P = 0.053), but that those for ( s R  s L ) / 2 were (  3 = 9.61, n = (13, 7, 11, 15), P = 0.022). When data from paradigm A and the eccentric position data from paradigm D were pooled (the experimental conditions for eccentric trials  in D were the same as in paradigm A), the effect of the paradigm was significant for l o gR L (  22 = 7.4, n = (24, 7, 7), P =.025) and ( s R  s L ) / 2 (  22 = 9, n = (28, 7, 11), P = 0.011). Tukey’s honestly significant difference test at the 0.05 significance level found differences in the mean rank  of l o gR L between alternating fixations ([A,D]) and dark fixations (B), and in the mean rank of ( s R  s L ) / 2 between alternating fixations ([A,D]) and sustained fixations (C). Taken together, the group comparisons for the four quantities of interest suggest that the difference in difficulty did not translate into a clear difference in PSEL  PSER or BR  BL.

Figure 4 Histograms of data pooled across all paradigms with centered head-on-trunk.

Nonparametric measures on the top row (A-C) and parametric measures on the bottom row (D-F).

Panels C and F are the paired comparisons of the same data represented on panels A and D, respectively. Not only the paired differences peak away from zero (C and F), but the population distributions (A and D) have a small overlap.

Figure 4 shows the population distributions pooled across the four paradigms. As expected from symmetry considerations, there was no significant difference between looking right and left (E = 16 and E = -16) for precision (W = 14, n = 32, P = 0.85, Wilcoxon signed-rank test) or sensitivity (W = 14, n = 38, P = 0.14, Wilcoxon signed-rank test) and there was a high degree of overlap between the right and left populations as quantified by the cosine similarity (non-centered Pearson correlation coefficient) of the two histograms (r = 0.94 and r = 0.72 respectively). The effect on PSE Ni, J., Tatalovic, M., Straumann, D., Olasagasti, I. (2013) Gaze direction affects linear self-motion heading discrimination in humans. European Journal of Neuroscience. doi: dx.doi.org/10.1111/ejn.12324 and B on the other hand is substantial. Not only was the distribution of paired differences significantly different from zero (W = 2, n = 32, P = 2.5e-7 and W = 2, n =38, P =5.4e-9 respectively, Wilcoxon signed-rank test) but the two distributions were well separated, with cosine similarity coefficients of r = 0.18 for both PSE and B. Across the four paradigms PSEL  PSER varied between

-3.3 and 9 with a median of 5.3 and the 95% confidence derived from bootstrapping with 1000 iterations was between 4.3 and 6.15. BR  BL varied between -0.22 and 0.60 with a median of 0.3 and a 95% confidence interval between 0.23 and 0.35.

The average pooled psychometric curves are shown in Figure 5 together with the average difference between the two as a function of trajectory deviation. In principle, the observed change in the proportion of rightward responses could be due to a horizontal shift of perceived direction of motion (or direction of the subjective median plane of the trunk) or by biasing the response towards the direction of eye eccentricity in lapse trials. The first explanation leads to a horizontal shift of the psychometric curves while the second would predict a vertical shift, and the difference in the proportion of rightward responses would not depend on trajectory deviation. Since the effect of trajectory deviation was significant (  3 = 17.3, n = 32, P = 6e-4, Friedman test), we conclude that, at least at the population level, the result was not simply due to an effect on lapse trials or to a nonspecific increase to report in the direction of eye deviation.

Figure 5 A: The proportion of rightward responses averaged over all 32 subjects in the head centric paradigms. When subjects participated in several paradigms, a within-subjects average was done prior to the average across subjects. B: average of intra-individual differences in rightward reports. The difference in reports when looking right and left is maximal for trajectories close to straight-ahead and decreases for larger trajectory deviations. In both panels error bars represent the 95% confidence interval as estimated from bootstrapping the data with 500 repetitions.

Centered versus deviated eye-in-head The results from the previous paradigms suggested that eye deviation shifts either the point of subjective equivalence or the median plane of the trunk. In this paradigm we asked whether eye eccentricity also affects the uncertainty in the task. A higher uncertainty would be reflected in higher  and lower sensitivities when compared with centric eye fixation. A group of subjects performed the task with blocks that had alternating left and right eccentric fixations and blocks in which gaze was always guided towards a center LED. Figure 6A shows the pooled psychometric functions (including the three subjects that showed the reversed eye eccentricity effect) together with the Ni, J., Tatalovic, M., Straumann, D., Olasagasti, I. (2013) Gaze direction affects linear self-motion heading discrimination in humans. European Journal of Neuroscience. doi: dx.doi.org/10.1111/ejn.12324

–  –  –

Figure 6 Paradigm with eccentric and centric eye positions. The goal was to determine whether eye eccentricity also changes sensitivity. A: average psychometric curves across all the subjects in the paradigm.

B: the difference in sensitivity as quantified by log σ and the nonparametric measure s. Individual data is superimposed on the boxplot. The median log σ was lower for the eccentric conditions, but the difference was not statistically significant.

The effect of head-on-trunk deviation We next asked whether head-on-trunk direction would have a similar effect on vestibular direction discrimination. To that end, another group of subjects performed the experiment with headNi, J., Tatalovic, M., Straumann, D., Olasagasti, I. (2013) Gaze direction affects linear self-motion heading discrimination in humans. European Journal of Neuroscience. doi: dx.doi.org/10.1111/ejn.12324 on-trunk displaced to the left 16° (Figure 1). Eccentric head-on-trunk (H = -16°) combined with a centric eye-in-head (E = 0°, gaze aligned with the head) when fixating the left LED, and with an eccentric eye-in-head (E = 16°, gaze aligned with the trunk) when fixating the center LED. As in paradigms A and D one of the two LEDs stayed on during motion (left or center in pseudo-random order in consecutive trials). Only one participant missed a few trials (four). All but one of the 17 subjects showed a significant effect of eye position on the total number of rightward reports. In 13 out of the 17 datasets the proportion of rightward reports was higher for E = 16° than for E = 0°, but 3 out of 17 showed the reversed effect. Since we were interested on the effect of head eccentricity, we excluded the participants with reversed eye effect from further analysis to minimize the impact of such a confounding factor. Therefore, the following analysis excludes the three reversed datasets. This left 13 parametric and 14 non-parametric datasets.

Figure 7 Bias and PSE with different combinations of eye and head directions. Data came from three datasets: (E=0˚,H=0˚) data from paradigm D, (E=16˚, H=0˚) and (E=-16˚, H=0˚) from paradigm A, and (E=0˚, H=-16˚) and (E=16˚, H=-16˚) from the head eccentric paradigm. With centered eye-in-head (E=0˚), there was a significant difference between the head centric and eccentric conditions. The two conditions with gaze to the left (G = -16˚) did not differ substantially providing evidence that gaze (the combination of eye-in-head and head-on-trunk) might be the determining factor. However, when looking at the condition with both eye- and head-deviations the distribution overlapped those with the same eye position (E=16˚, H=0˚) and same gaze (E=0˚, H=0˚) and the median value was not substantially different from the condition with the same eye position, indicating that the combination of eye and head eccentricity was highly variable across subjects.

To determine the effect of head eccentricity we compared the results in this paradigm with those in the two head-centered paradigms with alternating gaze directions (A and D). The datasets in paradigm A (10 parametric, 13 non-parametric) contributed the data for comparison with the H = 0°, E = +/-16° conditions, and the datasets in paradigm D (14 parametric, 15 non-parametric) the data for comparison with H = 0°, E = 0°. In the following n refers to the number of datasets in a given group.

Ni, J., Tatalovic, M., Straumann, D., Olasagasti, I. (2013) Gaze direction affects linear self-motion heading discrimination in humans. European Journal of Neuroscience. doi: dx.doi.org/10.1111/ejn.12324 First, to isolate the effect of head deviation we compared centric eye conditions (E = 0°) with and without head deviation. PSE (H = -16°, E = 0°) was between -0.4° and 4.6° with a median of

2.2°. The median PSE with head eccentric (n = 13) deviated 2.5° to the right with respect to head centric (H = 0°, E = 0°, n = 14) (  12 = 10, n = (13, 14), P = 0.001, Kruskal-Wallis test). Thus for E = 0°, a deviation of the head to the left shifted the psychometric curve to the right (higher proportion of leftward reports), that is, in the same direction as the shift due to eye deviations for most subjects described in the previous sections. There was a corresponding shift in the bias measure, which varied between 0.38 and 0.69 with a median of 0.5 with centered head (n = 15), and from 0.2 and 0.54 with a median of 0.39 with head eccentric (n = 14). Therefore, with head deviated to the left, the proportion of rightward responses was 20% smaller (  12 = 8.8, P = 0.003, n = (14,15), KruskalWallis test). We conclude that head eccentricity affected the proportion of rightward reports in the same direction as eye eccentricity did. Indeed, the difference in PSE median values when comparing the same gaze conditions attained with only head deviation (E = 0°, H = -16°, n = 13) or only eye deviation (E = -16°, H = 0°, n = 10), (columns 4 and 5 in Figure 7), was only -0.1° (  12 = 0.5, n = (13, 10), P = 0.49, Kruskal-Wallis test).

Finally, we compared the condition with simultaneous eye and head deviations (H = -16°, E = 16°) to the head-centric results with the same eye position (H = 0°, E = 16°) or same gaze (H = 0°, E = 0°). If the effects of eye and head were of the same size and independent, we should recover the head effect mentioned above for the first comparison and should find no difference for the second comparison. For the same eye position, the difference in median PSE was -0.15° (  12 = 0.015, n = (13, 10), P = 0.90, Kruskal-Wallis test), while the difference in bias was -0.03 (  12 = 1.0, n = (14, 13), P = 0.31, Kruskal-Wallis test). For the comparisons with the same gaze the difference in median PSE was -1.5° (  12 = 3.1, n = (13, 14), P = 0.081, Kruskal-Wallis test) and the difference in bias 0.11 (  12 = 4.8, n = (14, 15), P = 0.029, Kruskal-Wallis test).

In summary, we found an effect of head direction that looked like the effect of eye direction but only when head deviation was not simultaneous with eye deviation. In the condition with both head and eye deviations, the effect of eye direction was stronger.

Discussion Summary and relation to results in the literature Both the direction of eye-in-head and the direction of head-on-trunk affected subjective reports about motion direction during passive translations. Although the deviation of the trajectories with respect to the trunk was the same across eye and head directions, most participants were more likely to judge a motion as ‘to the right’ with respect to their trunk when eyes deviated to the right, and more likely to judge motion as ‘to the left’ when eyes deviated to the left. Likewise, we found evidence that with leftward head-on-trunk there were more reports to the left. Only a few subjects showed a significant and opposite effect of eye/head direction. The observed changes in the proportion of rightward reports were consistent with a shift of the perceived direction of motion towards the eye/head (or a shift of the internal representation of the trunk straight ahead in the opposite direction). At the population level there was no bias when eye, head and trunk were aligned;

and the shift, although in opposite directions, was of the same magnitude for right and left eye deviations (Figure 7A). Despite introducing a shift in heading perception, eye deviation had no Ni, J., Tatalovic, M., Straumann, D., Olasagasti, I. (2013) Gaze direction affects linear self-motion heading discrimination in humans. European Journal of Neuroscience. doi: dx.doi.org/10.1111/ejn.12324 measurable effect on the uncertainty of the task; sensitivities and thresholds were not significantly different when comparing centered and deviated eye conditions. Assuming that the point of subjective equivalence can be written as PSE = aE + b, we were able to estimate the weight of eye deviation, a = 0.17 (0.06) (median and median absolute deviation).

This is the first time that shifts evoked by eye- and head- direction are reported in a task involving the perception of linear motion direction based on vestibular cues. However, the effect of eye eccentricity is well documented in auditory and visual localization and in the perception of the head straight ahead (Bohlander, 1984; Lewald, 1997; Lewald & Ehrenstein, 2000a; Razavi et al.,2007; Cui et al., 2010) and so is the effect of head eccentricity (Lewald & Ehrenstein, 1998;

Lewald et al., 2000b). Moreover, the effects of eye- and head-eccentricity are equivalent in their influence on visual and auditory stimuli (Lewald et al., 2000b). When eye- or head-eccentricity is of short duration, the auditory median plane and perceived straight ahead of the head shift in the direction of eccentric gaze. This leads to a shift of free-field sound localization in the opposite direction (Lewald&Geltzmann, 2006). However, when eye position is maintained eccentrically for longer periods both perceived head straight ahead and perceived free-field sound localization shift toward eye eccentricity with a larger shift of perceived straight ahead than sound localization (Cui et al., 2010).

Pages:     | 1 | 2 || 4 | 5 |   ...   | 6 |

Similar works:

«17 PATIENT COUNSELING INFORMATION Patients should be informed of the availability of a Medication guide and they should be instructed to read the Medication Guide prior to taking BANZEL. Patients should be instructed to take BANZEL only as prescribed.17.1 Suicidal Thinking and Behavior Patients, their caregivers, and families should be informed that antiepileptic drugs increase the risk of suicidal thoughts and behavior and should be advised of the need to be alert for the emergence or...»

«Neuropsychology Copyright 1991 by the Educational Publishing Foundation 1991. Vol. 5, No. 1, 43-48 0894-4105/91/53.00 Handedness Inventories: Edinburgh Versus Annett STEPHEN M. WILLIAMS Institute for Health Studies Colchester, United Kingdom Abstract: Two handedness inventories were compared. The Edinburgh Handedness Inventory yielded more either-hand and fewer left-hand responses than does the Annett questionnaire. Both questionnaires showed high internal consistency. Ear preference in...»

«THE A U S T R A L I A N N A T I ON A L Ul I V ERSI T Y THE AUSTRALIAN NATIONAL UNIVERSITY GENERAL INFORMATION Extracts from Part i of the University Calendar for igy2 revised September igy2 for igy3 T he U niversity’s postal address is Box 4, P.O., C anberra, A.C.T. 2600, A ustralia, its telegraphic address N atuniv, C anberra, and its telephone num ber C anberra 495111. T he U niversity’s official correspondence is con­ ducted by the R egistrar. CONTENTS Principal Dates for 1973 4, 5 The...»

«Introduction Dental appliances can play an extremely important role in the management of sleep apnea and snoring. In fact, dental appliances (also called “oral appliances”) are second only to CPAP as the go-to treatment for sleep apnea recommended by the American Academy of Sleep Medicine. If you’ve been struggling with your CPAP and are looking for an alternative that is more comfortable, easier to use, and is more portable, then a dental appliance might be just what you need! But...»

«Public Health Service DEPARTMENT OF HEALTH & HUMAN SERVICES Food and Drug Administration Rockville, MD 20857 TRANSMITTED BY FACSIMILE D. Geoffrey Shulman, MD, FRCPC Chairman of the Board and Chief Executive Officer DUSA Pharmaceuticals, Inc. 25 Upton Drive Wilmington, MA 01887 RE: NDA # 20-965 Levulan® Kerastick® (aminolevulinic acid HCl) for Topical Solution, 20% MACMIS ID # 15170 WARNING LETTER Dear Dr. Shulman: The Division of Drug Marketing, Advertising, and Communications (DDMAC) of the...»

«CONTAINS NON-BINDING RECOMMENDATIONS #135 Guidance for Industry Validation of Analytical Procedures for Type C Medicated Feeds This guidance discusses characteristics that may be considered during the validation of nonmicrobiological analytical procedures for the analysis of drugs in Type C medicated feeds included as part of original and supplemental new animal drug applications (NADAs) and abbreviated new animal drug applications (ANADAs) for Type A Medicated Articles submitted to the Food...»

«ANNEX I SUMMARY OF PRODUCT CHARACTERISTICS 1 1. NAME OF THE MEDICINAL PRODUCT Protaphane 40 IU/ml Suspension for injection in a vial 2. QUALITATIVE AND QUANTITATIVE COMPOSITION Insulin human, rDNA (produced by recombinant DNA technology in Saccharomyces cerevisiae). 1 ml contains 40 IU of insulin human 1 vial contains 10 ml equivalent to 400 IU One IU (International Unit) corresponds to 0.035 mg of anhydrous human insulin. Protaphane is a suspension of isophane (NPH) insulin. For excipients,...»

«I. PROJECT NARRATIVE (1) PLAN FOR IMPROVING POPULATION HEALTH Delaware aspires to be one of the five healthiest states in the nation, as measured by its performance on core dimensions of Centers for Disease Control and Prevention’s (CDC) Healthy People 2020 goals. Although Delaware has strong public health, community, and health care programs and a track record of success on specific initiatives, Delaware spends 25% more per capita on health care than the U.S. average and outcomes remain...»

«Advanced Statistical Analysis of Mortality Rhodes, Thomas E. and Freitas, Stephen A. MIB, Inc 160 University Avenue Westwood, MA 02090 001-(781)-751-6356 fax 001-(781)-329-3379 trhodes@mib.com Abstract This paper demonstrates the utility of the Poisson Distribution in advanced statistical analysis of mortality in order to allow the researcher to obtain more information from their data. The use of the Poisson Distribution allows one to compare low numbers of deaths in a strata, thereby deriving...»

«REPORT ON BASELINE EMPLOYER SURVEY AND WORKER INTERVIEWS The Seattle Minimum Wage Study Team1 University of Washington April 2016 Daniel J. Evans School of Public Policy & Governance University of Washington Box 353055 Seattle, WA 98195 School of Social Work University of Washington Box 354900 Seattle, WA 98195 School of Public Health University of Washington Box 357230 Seattle, WA 98195 Any opinions expressed in this report are those of the authors and not the University of Washington or any...»

«John D. Meeker Professor & Associate Dean for Research School of Public Health University of Michigan Room 1835, SPH I Phone: (734) 764-7184 1415 Washington Hts. Fax: (734) 936-7283 Ann Arbor, MI 48109 meekerj@umich.edu EDUCATION: Harvard University School of Public Health, Boston, MA Sc.D., Exposure, Epidemiology & Risk, April 2004 Harvard University School of Public Health, Boston, MA M.S., Environmental Science and Engineering, June 2001 Iowa State University of Science and Technology, Ames,...»

«Commentary – Author Version Better than nothing or savvy risk-reduction practice? The importance of withdrawal Rachel K. Jones, Julie Fennell, Jenny A. Higgins and Kelly Blanchard Corresponding author: Rachel K. Jones, Guttmacher Institute, New York, NY 10038, rjones@guttmacher.org, 212.248.1111 X2262 Julie Fennell: Sociology Dept, Central Connecticut State University, New Britain, CT 06050 Jenny A. Higgins: Office of Population Research, Wallace Hall, Princeton University, Princeton, NJ...»

<<  HOME   |    CONTACTS
2016 www.dissertation.xlibx.info - Dissertations, online materials

Materials of this site are available for review, all rights belong to their respective owners.
If you do not agree with the fact that your material is placed on this site, please, email us, we will within 1-2 business days delete him.