Article Figures & Data
- Figure 1.
Scheme of the experimental design. Two independent cohorts of mice were trained daily in the visual water task (VWT) until reaching binocular visual acuity (VA) based on established protocols (Prusky et al., 2000b, 2004). At the day of standard VA assessment, the two groups were also tested in the virtual-reality optomotor (OPT) system (optomotry) to determine the spatial frequency threshold of the OPT response (standard OPT threshold). One of the cohorts then obtained monocular deprivation (MD). Both cohorts were continued to be trained in the VWT. The monocular VA and OPT threshold of the VWT/MD group (during MD) was again determined after reaching the criterion (see Materials and Methods). In about half of the mice of the VWT/MD group, the MD was reopened and mice were continued to be trained daily in the VWT (VWT/MD-reopening). The binocular long-term VA and OPT threshold of both the VWT/no-MD and VWT/MD-reopening group was again tested after a comparable training time (see Materials and Methods). Instead of reopening the MD, optical imaging of intrinsic signals (OI) was performed with the other half of the deprived group (VWT/MD-OI). For comparison, a cohort of mice that had been deprived for a comparably long time but not VWT-trained was imaged (SC/MD-OI). As a control for the long-term trained VWT/MD group, we used the VWT/no-MD group after finishing the VWT (VWT/no-MD-OI). Likewise, we also tested an age-matched nondeprived, SC-housed cohort (SC/no-MD-OI).
- Figure 2.
Extended VWT training strongly increased mouse VA. Mice were initially trained in the VWT to discriminate a vertical, low spatial frequency sine wave grating from isoluminant gray. Standard VA was determined after 18 ± 3 d (545 ± 88 trials) of VWT training; after a total of 66 ± 7 d (1987 ± 207 trials), long-term VA was determined. A, VA of an animal in cyc/deg plotted against total trials/training days of VWT-experience. B, Average VA-curve of the VWT/no-MD group (n = 5, mean ± SEM): individual curves were averaged starting from the test phase (time point 0). Gray vertical lines indicate the timepoints of VA and corresponding OPT threshold determination.
- Figure 3.
Extended monocular VWT training did not reliably increase VA, but long-term VWT training did. After determination of a standard VA, one eye was closed in animals of the VWT/MD group and mice were trained monocularly in the VWT. After an adaption phase of one week after MD (light gray background), a monocular VA (VA during MD) was determined (dark gray), then the previously closed eye was reopened, and binocular VWT training was continued (another 7 d adaption phase was introduced, light gray), until a long-term VA was determined (white). Note that individual mice (A, B) responded quite differently to MD. Data plotted as in Figure 2A.
- Figure 4.
Mouse X reached a VA of 1.49 cyc/deg after 34 d of VWT training (1040 trials). This individual mouse exhibited a consistent behavioral strategy for deciding where to swim: it held onto the midline divider (see also Video 1). Data plotted as in Figure 2A.
- Figure 5.
VA increase after long-term VWT training. A, Gain on baseline (%) of long-term VA of the VWT/no-MD (left, n = 5) and VWT/MD-reopening (sub)group (MD, right, n = 6). Values are represented as mean ± SEM. Statistical significance was tested by a two-tailed unpaired t test.
- Figure 6.
VWT and OPT thresholds of individual mice develop differently. Quantitative comparison of VWT-determined VA (A) and OPT thresholds (B) in individual animals of the VWT/no-MD group (n = 5) before (standard) and after long-term VWT training (left column) and in the VWT/MD group before (standard, n = 11), during (n = 11), and after MD (long-term, VWT/MD-reopening, n = 6/11; right column). The color code indicates low initial standard VA values in yellowish, higher values in reddish colors. A, VA (cyc/deg), determined by VWT. B, Spatial frequency threshold of the OPT reflex (OPT threshold, cyc/deg). A, B, Statistical significance was tested by two-tailed paired t tests; *p < 0.05; **p < 0.01; ***p < 0.001. C, Average VA and OPT thresholds. Values are represented as mean ± SEM (D) VA plotted against OPT thresholds of individual mice.
- Figure 7.
Training time in the VWT and correlation with VA. Time required to finish the different episodes of VWT training in (A) days and (B) minutes of the VWT/no-MD (upper row, n = 5) and VWT/MD(-reopening) group (lower row, n = 11 for standard and VA during MD, n = 6 for long-term VA after MD reopening). Individual data points are color-coded as introduced in Figure 6. C, Correlation of time required per correct trial near the break (spatial frequency of the break and two frequency steps below) and VA.
- Figure 8.
Long-term MD induced OD plasticity in adult mouse V1. Optically recorded activity maps of the contralateral (contra) and ipsilateral (ipsi) eye in the binocular part of V1 of SC-raised mice with (A, B) and without (C, D) VWT training, before (no-MD; A, C) and after MD (B, D). Gray scale-coded activity maps (numbers correspond to quantified V1 activation), color-coded two-dimensional OD maps (color codes ODI), and the histogram of OD scores, including the average ODI, are illustrated. In mice without MD (A, C), activity patches evoked by visual stimulation of the contralateral eye are darker than those of the ipsilateral eye, warm colors prevail in the two-dimensional OD maps and ODI values are positive. Long-term MD (MD eye is indicated by the black spot) resulted in a strong OD shift toward the open eye in both the VWT-trained and SC mice (B, D): both eyes activated V1 more equally strong, colder colors prevailed in the OD maps, and ODI values were lower, i.e., the ODI histograms shifted to the left (blue arrows). Note that there is a visible decrease of deprived (contra) eye responses after MD in V1 of VWT mice (B), which is absent after MD in SC mice (D). ant, anterior; lat, lateral. Scale bar: 1 mm.
- Figure 9.
Quantification of visual cortical activation before and after MD. ODI (A) and V1 activation (B) in V1 of VWT-trained and SC mice. A, Optically imaged ODIs without (no-MD) and with MD in VWT (white) and SC (gray) mice. Symbols represent ODI values of individuals; means are marked by horizontal lines. MD is indicated by half-black circles. B, V1 activation elicited by stimulation of the contralateral (C) or ipsilateral (I) eye in VWT and SC mice with MD. Black filled circles indicate MD eye. A, B, Data represented as mean ± SEM. Statistical significance was tested by Mann–Whitney tests: *p < 0.05; **p < 0.01.
Visual water task - rules Frequency range (cyc/deg) 0.086–0.172 0.201–0.372 ≥0.401 Criteria to pass(correct trials/total trials) 1/1 3/3 5/5 or 3/4 or 5/6 or 7/10 or 7/10 or 7/10 → break → break → break Different criteria applied for different spatial frequency ranges, e.g., in the lowest range, one correct trial was sufficient for passing this frequency step, resulting in an increase of the spatial frequency. If an animal failed the first trial, it still had the chance to pass by correctly choosing in three out of four or seven out of 10 trials. If it failed, the spatial frequency was decreased by three steps. In higher frequency ranges, the criteria were more strict to exclude coincidental passing.
Figure Group Parameter n CI95 Data structure Comparison Type of test p/r 2 value 5 VWT/no-MD and VWT/MD-reopening [A] no-MD – VA % gain[B] MD – VA % gain 56 [9.692; 53.92][11.10; 57.88] Normal distributionNormal distribution [A] vs [B] Unpaired t test p = 0.8328 6A VWT/no-MD [A] standard VA[B] long-term VA 55 [0.4854; 0.6263][0.5755; 0.8913] Normal distributionNormal distribution [A] vs [B] Paired t test p = 0.0171* 6A VWT/MD(-reopening) [A] standard VA[B] VA during MD[C] long-term VA 11/611/66 [0.5927; 0.6849][0.5339; 0.7873][0.7901; 0.9986] Normal distributionAssumed normal distributionNormal distribution [A] vs [B] (11/11)[B] vs [C] (6/6)[A] vs [C] (6/6) Paired t testPaired t testPaired t test p = 0.7291p = 0.0471*p = 0.0088** 6B VWT/no-MD [A] standard OPT thr[B] long-term OPT thr 55 [0.3822; 0.4110][0.3763: 0.4101] Normal distributionAssumed normal distribution [A] vs [B] Paired t test p = 0.3310 6B VWT/MD [A] standard OPT thr[B] OPT thr during MD[C] long-term OPT thr 11/611/66 [0.3831; 0.4072][0.4220; 0.4646][0.3795; 0.4363] Normal distributionNormal distributionNormal distribution [A] vs [B] (11/11)[B] vs [C] (6/6)[A] vs [C] (6/6) Paired t testPaired t testPaired t test p = 0.0002 ***p = 0.0289*p = 0.0783 6D VWT/no-MD [A] standard VA/OPT thr[B] long-term VA/OPT thr 55 NANA NANA VA vs OPT thrVA vs OPT thr CorrelationCorrelation r 2 = 0.2210r 2 = 0.2347 6D VWT/MD(-reopening) [A] standard VA/OPT thr[B] VA/OPT thr during MD[C] long-term VA/OPT thr 11116 NANANA NANANA VA vs OPT thrVA vs OPT thrVA vs OPT thr CorrelationCorrelationCorrelation r 2 = 0.0026r 2 = 0.0180r 2 = 0.0266 7C VWT/no-MD [A] standard VA[B] long-term VA 55 NANA NANA VA vs s/trialVA vs s/trial CorrelationCorrelation r 2 = 0.0741r 2 = 0.4973 7C VWT/MD(-reopening) [A] standard VA[B] VA during MD[C] long-term VA 11116 NANANA NANANA VA vs s/trialVA vs s/trialVA vs s/trial CorrelationCorrelationCorrelation r 2 = 0.1353r 2 = 0.1131r 2 = 0.0289 9A VWT andSC-OI [A] VWT/no-MD-OI[B] VWT/MD-OI[C] SC/no-MD-OI[D] SC/MD-OI 4554 [0.2754; 0.5196][-0.0677;0.1597][0.2492; 0.3908][0.04208; 0.1829] UnknownNormal distributionNormal distributionUnknown [A] vs [B][C] vs [D][A] vs [C][B] vs [D] Mann–WhitneyMann–WhitneyMann–WhitneyMann–Whitney p = 0.0159*p = 0.0159*p = 0.2187p = 0.2663 9B VWT andSC-OI [A] VWT/no-MD-OI, contra[B] VWT/no-MD-OI, ipsi[C] VWT/MD-OI, contra[D] VWT/MD-OI, ipsi[E] SC/no-MD-OI, contra[F] SC/no-MD-OI, ipsi[G] SC/MD-OI, contra[H] SC/MD-OI, ipsi 44555544 [1.649; 2.286][0.8821; 1.013][0.8455; 1.946][0.7713; 2.373][1.325; 1.915][0.7865; 1.150][0.7516; 1.878][0.9528; 1.487] UnknownUnknownNormal distributionNormal distributionNormal distributionNormal distributionUnknownUnknown [A] vs [B][C] vs [D][E] vs [F][G] vs [H][A] vs [C][B] vs [D][E] vs [G][F] vs [H] Mann–WhitneyMann–WhitneyMann–WhitneyMann–WhitneyMann–WhitneyMann–WhitneyMann–WhitneyMann–Whitney p = 0.0286*p = 0.8413p = 0.0079**p = 0.6857p = 0.0317*p = 0.1905p = 0.2857p = 0.0851 The table lists from left to right the figures referred to, groups compared (group), parameters analyzed (parameter), number of animals (n), lower (left) and upper (right) 95% confidence interval of the mean (CI95), distribution of the values (data structure), comparisons of (sub)groups abbreviated as indicated in the parameter column (comparison), test applied for the comparison (type of test), and statistical readout (p/r 2 value). OPT thr, OPT threshold; ipsi and contra, ipsilateral and contralateral eye; NA, not assessable; s/trial, seconds required per correct trial near the break. Significance levels were set as *p < 0.05; **p < 0.01; ***p < 0.001.
- Video 1.
Mouse X performing the VWT. In the recorded example, the rewarded visual stimulus consists of a vertical sine wave grating with a spatial frequency of 1.39 cyc/deg. The video starts with a close-up of the stimulus monitor to show the high spatial frequency of the presented grating stimulus (upper left), the nonrewarded stimulus is equiluminant gray (upper right). Reflections of the stimuli on the water surface are seen below. The mouse is released into the water-filled pool and swims toward the midline divider, holds on to it, and repeatedly looks either left or right before deciding to swim leftwards (correct response).
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