Background:A few hours of monocular deprivation with a diffuser eye patch temporarily strengthens the contribution of the deprived eye to binocular vision.This shift in favour of the deprived eye is characterized as a...Background:A few hours of monocular deprivation with a diffuser eye patch temporarily strengthens the contribution of the deprived eye to binocular vision.This shift in favour of the deprived eye is characterized as a form of adult visual plasticity.Studies in animal and human models suggest that neuromodulators can enhance adult brain plasticity in general.Specifically,acetylcholine has been shown to improve certain aspects of visual function and plasticity in adulthood.We investigated whether a single administration of donepezil(a cholinesterase inhibitor)could further augment the temporary shift in perceptual eye dominance that occurs after two hours of monocular patching.Methods:We conducted three experiments to investigate whether donepezil enhances the shift in perceptual eye dominance induced by monocular patching.In each experiment,healthy adults completed two experimental sessions while taking either donepezil(5 mg,oral)or a placebo(lactose)pill.In experiment 1 we patched the non-dominant eye for 2 hours and measured ocular balance with a binocular phase combination task.In experiment 2 we patched for one hour to investigate whether donepezil shortens the amount of time necessary to observe a shift in ocular dominance.In experiment 3 we patched for 2 hours and measured ocular balance with a binocular rivalry task to see if the effect of donepezil was comparable across the two tasks.We calculated AUCs for the shift in perceptual eye dominance across five time points after removing the patch to compare our treatment conditions in each experiment.Results:Donepezil significantly reduces the magnitude and duration of the shift in perceptual eye dominance produced by both 2(P<0.01)and 1 hours(P<0.05)of monocular patching when measuring ocular balance with a binocular phase combination task.Donepezil also reduces the magnitude of the shift in ocular dominance when measuring balance with a binocular rivalry task.Conclusions:Previous studies have demonstrated that cholinergic potentiation enhances adult brain plasticity.Because of this,we hypothesized donepezil would further augment the strength of the deprived eye after patching.Our study demonstrates that enhanced cholinergic potentiation actually interferes with the consolidation of the perceptual eye dominance plasticity induced by several hours of monocular deprivation.These results contribute to the growing evidence that cholinergic potentiation enhances certain forms of adult brain plasticity at the expense of others.展开更多
Background:In situations where one eye gives a more blurred input to visual processing than the other,the input from the sharper eye tends to dominate the percept.This phenomenon has clinical relevance for monovision ...Background:In situations where one eye gives a more blurred input to visual processing than the other,the input from the sharper eye tends to dominate the percept.This phenomenon has clinical relevance for monovision treatment,where the two eyes are corrected separately for different distances.We performed a psychophysical investigation of subjects’ability to identify which of a set of images was blurred in one eye.Methods:We tested 17 subjects with normal or corrected-to-normal vision.On each trial,subjects viewed an array of four pictures using a monitor with shutter goggles.In the first experiment,three of the pictures were sharp in both eyes(distractors).The fourth picture was sharp in one eye and blurred by a low-pass filter in the other.Subjects identified that odd-one-out target over many trials with different degrees of blur.In the second experiment the target picture was given the same treatment,but the three non-target pictures were made monocular(sharp in one eye,mean grey in the other).Results:The results from the first experiment with binocular distractors followed our expectations,with subjects showing better performance at detecting more severe blurs.In the second experiment with monocular distractors,we found large individual differences between our observers.Some performed the same as they did in the first condition,others now found the task impossible,and a few performed worse with severe blurs than they did with slight blurs.Conclusions:Previous studies have reported individual differences in blur suppression,however this study reveals that these differences may depend on the precise details of the judgements being made.展开更多
Background:The human visual system extracts depth information from disparity in the images seen by the two eyes.The ability to calculate depth from disparity will be disrupted if local retinal abnormalities distort pa...Background:The human visual system extracts depth information from disparity in the images seen by the two eyes.The ability to calculate depth from disparity will be disrupted if local retinal abnormalities distort parts of those images,especially if these distortions are different in the two eyes.In its early stages,age-related macular degeneration(AMD)causes slight distortions in the central vision field which differ in the two eyes.AMD is the most common form of irreversible blindness in people over the age of 50.The goal of this project is to develop a stereoscopic perception test which leverages the sensitivity of binocular depth perception to detect the interocular differences symptomatic of either early-stage AMD or other diseases affecting the retina.Methods:A program was written in MATLAB that allowed separate left and right eye stimuli to be shown to the two eyes.NVIDIA 3D Vision 2 stereoscopic glasses were used to present the stimuli.The test we have developed consists of random dot patterns covering the central 5 degrees of vision.One or more disk-shaped perturbations in depth are displayed at different locations in the visual field of the subjects.Of the ten possible target locations,we present between one and four disks on each trial.The disks will only be visible if there is an undistorted input for that visual field location from the two retinae.The participant uses a keypad to report the number of floating disks seen.A set of trials with randomized locations and numbers of disks is used to gather initial data on likely areas of stereoscopic vision deficit;afterwards,likelihoods for deficits in each location are calculated and used to generate customized subsequent trials.Results:The software to perform the local stereovision test has been developed and is now being piloted.We are currently collecting data from healthy normal subjects prior to applying the test to clinical populations.In order to simulate the central vision distortions of AMD,patches of the stimulus for one eye are scrambled and blurred.This allows us to ensure that the task is functioning correctly.Conclusions:The next step for this project is for it to be tested on ageing clinical populations to find its effectiveness in differentiating patients with normal sight from those showing early symptoms of AMD or other retinal abnormalities such as diabetic retinopathy.This test could represent a novel approach in early clinical detection of ocular disease.展开更多
Background:We investigate whether changes in visual plasticity induced by monocular deprivation can be maintained across multiple days.It has been known that monocular deprivation strengthens the deprived eye in adult...Background:We investigate whether changes in visual plasticity induced by monocular deprivation can be maintained across multiple days.It has been known that monocular deprivation strengthens the deprived eye in adults with normal vision for a short period of time(30-60 minutes).This has been shown through a variety of visual tasks such as binocular combination and rivalry.Methods:Ten subjects were recruited and patched for five consecutive days for two hours.We used a binocular phase combination task to measure the subjects’sensory eye balances.We initially measured their baseline of sensory eye balance,patched their dominant eye,and then conducted post-patching measurements at 0,3,6,12,24 and 48 minutes after patching.Results:We performed a 2-way ANOVA(Before vs.after patching×Day);we found that although the effect of monocular deprivation on the deprived eye was significant,F(1,9)=17.32,P=0.002,the effect of Day was not.Conclusions:Hence we found no accumulation of the patching effect across five days in healthy adults.This suggests that the degree of remnant neural plasticity in adult primary visual cortex may be too limited to be exploited therapeutically.展开更多
Background:The human visual system can use binocular disparity to make depth judgements.Previous studies looking at the normal population have found a wide range in ability to perform depth-polarity tasks.We explored ...Background:The human visual system can use binocular disparity to make depth judgements.Previous studies looking at the normal population have found a wide range in ability to perform depth-polarity tasks.We explored if these large individual differences are also present when using a depth increment paradigm,and if they depend on the sign of disparity.Methods:Stereoacuity for detecting a wedge-shaped surface in a field of dots was measured in 53 adults(28 males)with normal vision.To better understand the variance in stereoacuity in the sample,for 18 subjects we measured stereo cuity with disparity noise added to the stimulus.Stereoacuity was unaffected at low levels of stimulus noise but beyond a critical value,it increased with the standard deviation of the noise.At this point the stimulus noise is equivalent to the internal noise of the subject.Stereoacuity measured at high stimulus noise levels reflects the efficiency with which a noisy input is processed by the visual system.We derived both parameters by fitting the linear amplifier model.Results:Stereoacuity ranged from 24 to 275 arc seconds.We found population differences in stereoacuity were explained by variation in both processing efficiency and internal noise levels.There was a tendency for higher task performance for crossed disparities compared to uncrossed disparities.Within subject sensitivity differences between crossed and uncrossed disparity were due to a higher efficiency when processing one direction.There was a trend for subjects with equal acuity for the two directions to have an increase in processing efficiency compensating for higher internal noise levels for that direction.Conclusions:Overall,our results show that the individual differences in stereoacuity for depth increment tasks can be attributed to variances in both the quality of the received input and the efficiency of processing of disparity-processing mechanisms.展开更多
文摘Background:A few hours of monocular deprivation with a diffuser eye patch temporarily strengthens the contribution of the deprived eye to binocular vision.This shift in favour of the deprived eye is characterized as a form of adult visual plasticity.Studies in animal and human models suggest that neuromodulators can enhance adult brain plasticity in general.Specifically,acetylcholine has been shown to improve certain aspects of visual function and plasticity in adulthood.We investigated whether a single administration of donepezil(a cholinesterase inhibitor)could further augment the temporary shift in perceptual eye dominance that occurs after two hours of monocular patching.Methods:We conducted three experiments to investigate whether donepezil enhances the shift in perceptual eye dominance induced by monocular patching.In each experiment,healthy adults completed two experimental sessions while taking either donepezil(5 mg,oral)or a placebo(lactose)pill.In experiment 1 we patched the non-dominant eye for 2 hours and measured ocular balance with a binocular phase combination task.In experiment 2 we patched for one hour to investigate whether donepezil shortens the amount of time necessary to observe a shift in ocular dominance.In experiment 3 we patched for 2 hours and measured ocular balance with a binocular rivalry task to see if the effect of donepezil was comparable across the two tasks.We calculated AUCs for the shift in perceptual eye dominance across five time points after removing the patch to compare our treatment conditions in each experiment.Results:Donepezil significantly reduces the magnitude and duration of the shift in perceptual eye dominance produced by both 2(P<0.01)and 1 hours(P<0.05)of monocular patching when measuring ocular balance with a binocular phase combination task.Donepezil also reduces the magnitude of the shift in ocular dominance when measuring balance with a binocular rivalry task.Conclusions:Previous studies have demonstrated that cholinergic potentiation enhances adult brain plasticity.Because of this,we hypothesized donepezil would further augment the strength of the deprived eye after patching.Our study demonstrates that enhanced cholinergic potentiation actually interferes with the consolidation of the perceptual eye dominance plasticity induced by several hours of monocular deprivation.These results contribute to the growing evidence that cholinergic potentiation enhances certain forms of adult brain plasticity at the expense of others.
文摘Background:In situations where one eye gives a more blurred input to visual processing than the other,the input from the sharper eye tends to dominate the percept.This phenomenon has clinical relevance for monovision treatment,where the two eyes are corrected separately for different distances.We performed a psychophysical investigation of subjects’ability to identify which of a set of images was blurred in one eye.Methods:We tested 17 subjects with normal or corrected-to-normal vision.On each trial,subjects viewed an array of four pictures using a monitor with shutter goggles.In the first experiment,three of the pictures were sharp in both eyes(distractors).The fourth picture was sharp in one eye and blurred by a low-pass filter in the other.Subjects identified that odd-one-out target over many trials with different degrees of blur.In the second experiment the target picture was given the same treatment,but the three non-target pictures were made monocular(sharp in one eye,mean grey in the other).Results:The results from the first experiment with binocular distractors followed our expectations,with subjects showing better performance at detecting more severe blurs.In the second experiment with monocular distractors,we found large individual differences between our observers.Some performed the same as they did in the first condition,others now found the task impossible,and a few performed worse with severe blurs than they did with slight blurs.Conclusions:Previous studies have reported individual differences in blur suppression,however this study reveals that these differences may depend on the precise details of the judgements being made.
文摘Background:The human visual system extracts depth information from disparity in the images seen by the two eyes.The ability to calculate depth from disparity will be disrupted if local retinal abnormalities distort parts of those images,especially if these distortions are different in the two eyes.In its early stages,age-related macular degeneration(AMD)causes slight distortions in the central vision field which differ in the two eyes.AMD is the most common form of irreversible blindness in people over the age of 50.The goal of this project is to develop a stereoscopic perception test which leverages the sensitivity of binocular depth perception to detect the interocular differences symptomatic of either early-stage AMD or other diseases affecting the retina.Methods:A program was written in MATLAB that allowed separate left and right eye stimuli to be shown to the two eyes.NVIDIA 3D Vision 2 stereoscopic glasses were used to present the stimuli.The test we have developed consists of random dot patterns covering the central 5 degrees of vision.One or more disk-shaped perturbations in depth are displayed at different locations in the visual field of the subjects.Of the ten possible target locations,we present between one and four disks on each trial.The disks will only be visible if there is an undistorted input for that visual field location from the two retinae.The participant uses a keypad to report the number of floating disks seen.A set of trials with randomized locations and numbers of disks is used to gather initial data on likely areas of stereoscopic vision deficit;afterwards,likelihoods for deficits in each location are calculated and used to generate customized subsequent trials.Results:The software to perform the local stereovision test has been developed and is now being piloted.We are currently collecting data from healthy normal subjects prior to applying the test to clinical populations.In order to simulate the central vision distortions of AMD,patches of the stimulus for one eye are scrambled and blurred.This allows us to ensure that the task is functioning correctly.Conclusions:The next step for this project is for it to be tested on ageing clinical populations to find its effectiveness in differentiating patients with normal sight from those showing early symptoms of AMD or other retinal abnormalities such as diabetic retinopathy.This test could represent a novel approach in early clinical detection of ocular disease.
文摘Background:We investigate whether changes in visual plasticity induced by monocular deprivation can be maintained across multiple days.It has been known that monocular deprivation strengthens the deprived eye in adults with normal vision for a short period of time(30-60 minutes).This has been shown through a variety of visual tasks such as binocular combination and rivalry.Methods:Ten subjects were recruited and patched for five consecutive days for two hours.We used a binocular phase combination task to measure the subjects’sensory eye balances.We initially measured their baseline of sensory eye balance,patched their dominant eye,and then conducted post-patching measurements at 0,3,6,12,24 and 48 minutes after patching.Results:We performed a 2-way ANOVA(Before vs.after patching×Day);we found that although the effect of monocular deprivation on the deprived eye was significant,F(1,9)=17.32,P=0.002,the effect of Day was not.Conclusions:Hence we found no accumulation of the patching effect across five days in healthy adults.This suggests that the degree of remnant neural plasticity in adult primary visual cortex may be too limited to be exploited therapeutically.
文摘Background:The human visual system can use binocular disparity to make depth judgements.Previous studies looking at the normal population have found a wide range in ability to perform depth-polarity tasks.We explored if these large individual differences are also present when using a depth increment paradigm,and if they depend on the sign of disparity.Methods:Stereoacuity for detecting a wedge-shaped surface in a field of dots was measured in 53 adults(28 males)with normal vision.To better understand the variance in stereoacuity in the sample,for 18 subjects we measured stereo cuity with disparity noise added to the stimulus.Stereoacuity was unaffected at low levels of stimulus noise but beyond a critical value,it increased with the standard deviation of the noise.At this point the stimulus noise is equivalent to the internal noise of the subject.Stereoacuity measured at high stimulus noise levels reflects the efficiency with which a noisy input is processed by the visual system.We derived both parameters by fitting the linear amplifier model.Results:Stereoacuity ranged from 24 to 275 arc seconds.We found population differences in stereoacuity were explained by variation in both processing efficiency and internal noise levels.There was a tendency for higher task performance for crossed disparities compared to uncrossed disparities.Within subject sensitivity differences between crossed and uncrossed disparity were due to a higher efficiency when processing one direction.There was a trend for subjects with equal acuity for the two directions to have an increase in processing efficiency compensating for higher internal noise levels for that direction.Conclusions:Overall,our results show that the individual differences in stereoacuity for depth increment tasks can be attributed to variances in both the quality of the received input and the efficiency of processing of disparity-processing mechanisms.
