1
|
Birch EE, Duffy KR. Leveraging neural plasticity for the treatment of amblyopia. Surv Ophthalmol 2024; 69:818-832. [PMID: 38763223 PMCID: PMC11380599 DOI: 10.1016/j.survophthal.2024.04.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2023] [Revised: 04/27/2024] [Accepted: 04/29/2024] [Indexed: 05/21/2024]
Abstract
Amblyopia is a form of visual cortical impairment that arises from abnormal visual experience early in life. Most often, amblyopia is a unilateral visual impairment that can develop as a result of strabismus, anisometropia, or a combination of these conditions that result in discordant binocular experience. Characterized by reduced visual acuity and impaired binocular function, amblyopia places a substantial burden on the developing child. Although frontline treatment with glasses and patching can improve visual acuity, residual amblyopia remains for most children. Newer binocular-based therapies can elicit rapid recovery of visual acuity and may also improve stereoacuity in some children. Nevertheless, for both treatment modalities full recovery is elusive, recurrence of amblyopia is common, and improvements are negligible when treatment is administered at older ages. Insights derived from animal models about the factors that govern neural plasticity have been leveraged to develop innovative treatments for amblyopia. These novel therapies exhibit efficacy to promote recovery, and some are effective even at ages when conventional treatments fail to yield benefit. Approaches for enhancing visual system plasticity and promoting recovery from amblyopia include altering the balance between excitatory and inhibitory mechanisms, reversing the accumulation of proteins that inhibit plasticity, and harnessing the principles of metaplasticity. Although these therapies have exhibited promising results in animal models, their safety and ability to remediate amblyopia need to be evaluated in humans.
Collapse
Affiliation(s)
- Eileen E Birch
- Crystal Charity Ball Pediatric Vision Laboratory, Retina Foundation, Dallas, TX, USA; University of Texas Southwestern Medical Center, Dallas, TX, USA.
| | - Kevin R Duffy
- Department of Psychology and Neuroscience, Dalhousie University, Halifax, NS, Canada
| |
Collapse
|
2
|
Mikhalkin AA, Nikitina NI, Merkulyeva NS. Early postnatal development of the primary visual areas 17 and 18 of the cat cerebral cortex: An SMI-32 study. J Neurosci Res 2024; 102:e25375. [PMID: 39105520 DOI: 10.1002/jnr.25375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Revised: 06/04/2024] [Accepted: 07/26/2024] [Indexed: 08/07/2024]
Abstract
Using anti-neurofilament H non-phosphorylated antibodies (SMI-32) as markers for the neuronal maturation level and Y channel responsible for motion processing, we investigated early postnatal development of the primary visual areas 17 and 18 in cats aged 0, 10, 14, and 34 days and in adults. Two analyzed parameters of SMI-32-immunolabeling were used: the total proportion of SMI-32-labeling and the density of labeled neurons. (i) The developmental time course of the total proportion of SMI-32-labeling shows the general increase in the accumulation of heavy-chain neurofilaments. This parameter showed a different time course for cortical layer development; the maximal increment in the total labeling in layer V occurred between the second and fifth postnatal weeks and in layers II-III and VI after the fifth postnatal week. In addition, the delay in accumulation of SMI-32-labeling was shown in layer V of the area 17 periphery representation during the first two postnatal weeks. (ii) The density of SMI-32-labeled neurons decreased in all layers of area 18, but was increased, decreased, or had a transient peak in layers II-III, V, and VI of area 17, respectively. The transient peak is in good correspondence with some transient neurochemical features previously revealed for different classes of cortical and thalamic neurons and reflects the time course of the early development of the thalamocortical circuitry. Some similarities between the time courses for the development of SMI-32-labeling in areas 17/18 and in A- and C-laminae of the LGNd allow us to propose heterochronous postnatal development of two Y sub-channels.
Collapse
Affiliation(s)
- A A Mikhalkin
- Pavlov Institute of Physiology, Russian Academy of Sciences, St. Petersburg, Russia
| | - N I Nikitina
- Pavlov Institute of Physiology, Russian Academy of Sciences, St. Petersburg, Russia
| | - N S Merkulyeva
- Pavlov Institute of Physiology, Russian Academy of Sciences, St. Petersburg, Russia
| |
Collapse
|
3
|
Merkulyeva N, Mikhalkin A. Transient expression of heavy-chain neurofilaments in the perigeniculate nucleus of cats. Brain Struct Funct 2024; 229:489-495. [PMID: 38265459 DOI: 10.1007/s00429-023-02752-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2023] [Accepted: 12/12/2023] [Indexed: 01/25/2024]
Abstract
The perigeniculate nucleus (PGN) is a visual part of the thalamic reticular nucleus modulating the information transfer between the lateral geniculate nucleus and the visual cortex. This study focused on the postnatal development of the PGN in cats, using the SMI-32 antibody, which recognizes non-phosphorylated heavy-chain neurofilaments responsible for neuronal structural maturation and is also used as a marker for motion processing, or Y, stream. We questioned whether transient neuronal populations exist in the PGN and can they possibly be related to the Y processing stream. We uncovered a transient, robust SMI-32 staining in the PGN of kittens aged 0-34 days with the significant decline in the cellular density of labeled cells in older animals. According to the double-labeling, in all examined age groups, perigeniculate SMI-32-immunopositive cells are part of the main parvalbumin-positive population. The maximal cellular density of the double-stained cells appeared in animals aged 10-28 days. We also revealed that the most significant growth of perigeniculate cells's soma occurred at three postnatal weeks. The possible link of our data to the development of the Y visual processing stream and to the heterogeneity of the perigeniculate neuronal population is also discussed.
Collapse
Affiliation(s)
- Natalia Merkulyeva
- Pavlov Institute of Physiology RAS, Makarov Nab., 6, Saint-Petersburg, Russia, 199034.
| | - Aleksandr Mikhalkin
- Pavlov Institute of Physiology RAS, Makarov Nab., 6, Saint-Petersburg, Russia, 199034
| |
Collapse
|
4
|
Henneberry JM, Elgallad J, Smith S, Duffy KR. Early monocular deprivation reduces the capacity for neural plasticity in the cat visual system. Cereb Cortex Commun 2023; 4:tgad017. [PMID: 37675436 PMCID: PMC10477708 DOI: 10.1093/texcom/tgad017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 07/26/2023] [Accepted: 07/30/2023] [Indexed: 09/08/2023] Open
Abstract
Obstruction of vision to one eye during early postnatal development elicits neural modifications in the visual system that can last a lifetime. Research in rodents has revealed that an early and transient monocular deprivation (MD) can produce an enduring alteration to the framework of neural connections within visual cortex. This lasting trace of early MD enables an enhanced effect of a second MD imposed on the same eye in adulthood. In the current study, we examined whether the modification of plasticity potential was bidirectional by assessing whether the effect of early and brief MD attenuated the impact of a subsequent MD when applied to the fellow eye. Results were clear in showing that animals with an early MD exhibited a smaller response to later visual deprivation of the fellow eye. Compared to controls, animals with a history of MD exhibited less atrophy of neurons, and a smaller loss of neurofilament labeling within the dorsal lateral geniculate nucleus. The shift in cortical ocular dominance elicited by MD was also smaller in animals with a prior MD. These results indicate that early MD elicits abiding and eye-specific neural modifications that can selectively alter plasticity potential in the visual system.
Collapse
Affiliation(s)
- Jonathon Mark Henneberry
- Department of Psychology and Neuroscience, Dalhousie University, 1355 Oxford St., Halifax, NS B3H 4R2, Canada
| | - Joseph Elgallad
- Department of Psychology and Neuroscience, Dalhousie University, 1355 Oxford St., Halifax, NS B3H 4R2, Canada
| | - Seth Smith
- Department of Psychology and Neuroscience, Dalhousie University, 1355 Oxford St., Halifax, NS B3H 4R2, Canada
| | - Kevin R Duffy
- Department of Psychology and Neuroscience, Dalhousie University, 1355 Oxford St., Halifax, NS B3H 4R2, Canada
| |
Collapse
|
5
|
Aronitz EM, Kamermans BA, Duffy KR. Development of parvalbumin neurons and perineuronal nets in the visual cortex of normal and dark-exposed cats. J Comp Neurol 2021; 529:2827-2841. [PMID: 33576496 DOI: 10.1002/cne.25127] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 02/07/2021] [Accepted: 02/08/2021] [Indexed: 11/06/2022]
Abstract
During development, the visual system maintains a high capacity for modification by expressing characteristics permissive for plasticity, enabling neural circuits to be refined by visual experience to achieve their mature form. This period is followed by the emergence of characteristics that stabilize the brain to consolidate for lifetime connections that were informed by experience. Attenuation of plasticity potential is thought to derive from an accumulation of plasticity-inhibiting characteristics that appear at ages beyond the peak of plasticity. Perineuronal nets (PNNs) are molecular aggregations that primarily surround fast-spiking inhibitory neurons called parvalbumin (PV) cells, which exhibit properties congruent with a plasticity inhibitor. In this study, we examined the development of PNNs and PV cells in the primary visual cortex of a highly visual mammal, and assessed the impact that 10 days of darkness had on both characteristics. Here, we show that labeling for PV expression emerges earlier and reaches adult levels sooner than PNNs. We also demonstrate that darkness, a condition known to enhance plasticity, significantly reduces the density of PNNs and the size of PV cell somata but does not alter the number of PV cells in the visual cortex. The darkness-induced reduction of PV cell size occurred irrespective of whether neurons were surrounded by a PNN, suggesting that PNNs have a restricted capacity to inhibit plasticity. Finally, we show that PV cells surrounded by a PNN were significantly larger than those without one, supporting the view that PNNs may mediate trophic support to the cells they surround.
Collapse
Affiliation(s)
- Elise M Aronitz
- Department of Psychology and Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Braden A Kamermans
- Department of Psychology and Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Kevin R Duffy
- Department of Psychology and Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
| |
Collapse
|
6
|
Mikhalkin A, Nikitina N, Merkulyeva N. Heterochrony of postnatal accumulation of nonphosphorylated heavy‐chain neurofilament by neurons of the cat dorsal lateral geniculate nucleus. J Comp Neurol 2020; 529:1430-1441. [DOI: 10.1002/cne.25028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 08/24/2020] [Accepted: 09/02/2020] [Indexed: 12/18/2022]
Affiliation(s)
- Aleksandr Mikhalkin
- lab Neuromorphology Pavlov Institute of Physiology RAS Makarov emb, 6 Saint‐Petersburg Russia
| | - Nina Nikitina
- lab Neuromorphology Pavlov Institute of Physiology RAS Makarov emb, 6 Saint‐Petersburg Russia
| | - Natalia Merkulyeva
- lab Neuromorphology Pavlov Institute of Physiology RAS Makarov emb, 6 Saint‐Petersburg Russia
| |
Collapse
|
7
|
Modification of Peak Plasticity Induced by Brief Dark Exposure. Neural Plast 2019; 2019:3198285. [PMID: 31565047 PMCID: PMC6745115 DOI: 10.1155/2019/3198285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 05/13/2019] [Accepted: 05/22/2019] [Indexed: 11/29/2022] Open
Abstract
The capacity for neural plasticity in the mammalian central visual system adheres to a temporal profile in which plasticity peaks early in postnatal development and then declines to reach enduring negligible levels. Early studies to delineate the critical period in cats employed a fixed duration of monocular deprivation to measure the extent of ocular dominance changes induced at different ages. The largest deprivation effects were observed at about 4 weeks postnatal, with a steady decline in plasticity thereafter so that by about 16 weeks only small changes were measured. The capacity for plasticity is regulated by a changing landscape of molecules in the visual system across the lifespan. Studies in rodents and cats have demonstrated that the critical period can be altered by environmental or pharmacological manipulations that enhance plasticity at ages when it would normally be low. Immersion in complete darkness for long durations (dark rearing) has long been known to alter plasticity capacity by modifying plasticity-related molecules and slowing progress of the critical period. In this study, we investigated the possibility that brief darkness (dark exposure) imposed just prior to the critical period peak can enhance the level of plasticity beyond that observed naturally. We examined the level of plasticity by measuring two sensitive markers of monocular deprivation, namely, soma size of neurons and neurofilament labeling within the dorsal lateral geniculate nucleus. Significantly larger modification of soma size, but not neurofilament labeling, was observed at the critical period peak when dark exposure preceded monocular deprivation. This indicated that the natural plasticity ceiling is modifiable and also that brief darkness does not simply slow progress of the critical period. As an antecedent to traditional amblyopia treatment, darkness may increase treatment efficacy even at ages when plasticity is at its highest.
Collapse
|
8
|
Fast Recovery of the Amblyopic Eye Acuity of Kittens following Brief Exposure to Total Darkness Depends on the Fellow Eye. Neural Plast 2019; 2019:7624837. [PMID: 31178904 PMCID: PMC6507257 DOI: 10.1155/2019/7624837] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Accepted: 03/12/2019] [Indexed: 11/18/2022] Open
Abstract
Recent studies conducted on kittens have revealed that the reduced visual acuity of the deprived eye following a short period of monocular deprivation imposed in early life is reversed quickly following a 10-day period spent in total darkness. This study explored the contribution of the fellow eye to the darkness-induced recovery of the acuity of the deprived eye. Upon emergence of kittens from darkness, the fellow eye was occluded for different lengths of time in order to investigate its effects on either the speed or the extent of the recovery of acuity of the deprived eye. Occlusion of the fellow eye for even a day immediately following the period spent in darkness blocked any recovery of the acuity of the deprived eye. Moreover, occlusion of the fellow eye two days after the period of darkness blocked any further visual recovery beyond that achieved in the short period when both eyes were open. The results imply that the darkness-induced recovery of the acuity of the deprived eye depends upon, and is guided by, neural activity in the mature neural connections previously established by the fellow eye.
Collapse
|
9
|
Duffy KR, Fong MF, Mitchell DE, Bear MF. Recovery from the anatomical effects of long-term monocular deprivation in cat lateral geniculate nucleus. J Comp Neurol 2017; 526:310-323. [PMID: 29023717 DOI: 10.1002/cne.24336] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 10/05/2017] [Accepted: 10/06/2017] [Indexed: 11/06/2022]
Abstract
Monocular deprivation (MD) imposed early in postnatal life elicits profound structural and functional abnormalities throughout the primary visual pathway. The ability of MD to modify neurons within the visual system is restricted to a so-called critical period that, for cats, peaks at about one postnatal month and declines thereafter so that by about 3 months of age MD has little effect. Recovery from the consequences of MD likewise adheres to a critical period that ends by about 3 months of age, after which the effects of deprivation are thought to be permanent and without capacity for reversal. The attenuation of plasticity beyond early development is a formidable obstacle for conventional therapies to stimulate recovery from protracted visual deprivation. In the current study we examined the efficacy of dark exposure and retinal inactivation with tetrodotoxin to promote anatomical recovery in the dorsal lateral geniculate nuclues (dLGN) from long-term MD started at the peak of the critical period. Whereas 10 days of dark exposure or binocular retinal inactivation were not better at promoting recovery than conventional treatment with reverse occlusion, inactivation of only the non-deprived (fellow) eye for 10 days produced a complete restoration of neuron soma size, and also reversed the significant loss of neurofilament protein within originally deprived dLGN layers. These results reveal a capacity for neural plasticity and recovery that is larger than anything previously observed following protracted MD in cat, and they highlight a possibility for alternative therapies applied at ages thought to be recalcitrant to recovery.
Collapse
Affiliation(s)
- Kevin R Duffy
- Department of Psychology & Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Ming-Fai Fong
- Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Donald E Mitchell
- Department of Psychology & Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Mark F Bear
- Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts
| |
Collapse
|
10
|
Kirkcaldie MTK, Dwyer ST. The third wave: Intermediate filaments in the maturing nervous system. Mol Cell Neurosci 2017; 84:68-76. [PMID: 28554564 DOI: 10.1016/j.mcn.2017.05.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Revised: 05/10/2017] [Accepted: 05/25/2017] [Indexed: 01/16/2023] Open
Abstract
Intermediate filaments are critical for the extreme structural specialisations of neurons, providing integrity in dynamic environments and efficient communication along axons a metre or more in length. As neurons mature, an initial expression of nestin and vimentin gives way to the neurofilament triplet proteins and α-internexin, substituted by peripherin in axons outside the CNS, which physically consolidate axons as they elongate and find their targets. Once connection is established, these proteins are transported, assembled, stabilised and modified, structurally transforming axons and dendrites as they acquire their full function. The interaction between these neurons and myelinating glial cells optimises the structure of axons for peak functional efficiency, a property retained across their lifespan. This finely calibrated structural regulation allows the nervous system to maintain timing precision and efficient control across large distances throughout somatic growth and, in maturity, as a plasticity mechanism allowing functional adaptation.
Collapse
Affiliation(s)
- Matthew T K Kirkcaldie
- School of Medicine, Wicking Dementia Research and Education Centre, Faculty of Health, University of Tasmania, Australia.
| | - Samuel T Dwyer
- School of Medicine, Wicking Dementia Research and Education Centre, Faculty of Health, University of Tasmania, Australia
| |
Collapse
|
11
|
Duffy KR, Lingley AJ, Holman KD, Mitchell DE. Susceptibility to monocular deprivation following immersion in darkness either late into or beyond the critical period. J Comp Neurol 2016; 524:2643-53. [PMID: 26878686 DOI: 10.1002/cne.23985] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Revised: 02/06/2016] [Accepted: 02/08/2016] [Indexed: 01/04/2023]
Abstract
An extended duration of darkness starting near the time of birth preserves immature neuronal characteristics and prolongs the accentuated plasticity observed in young animals. Brief periods of complete darkness have emerged as an effective means of restoring a high capacity for neural plasticity and of promoting recovery from the effects of monocular deprivation (MD). We examined whether 10 days of darkness imposed in adulthood or beyond the peak of the critical period could rejuvenate the ability of MD to reduce the size of neuron somata within deprived layers of the cat dorsal lateral geniculate nucleus (dLGN). For adult cats subjected to 10 days of darkness before 7 days of MD, we observed no alteration in neuron size or neurofilament labeling within the dLGN. At 12 weeks of age, MD that followed immediately after 10 days of darkness produced an enhanced reduction of neuron soma size within deprived dLGN layers. For this age we observed that 10 days of darkness also enhanced the loss of neurofilament protein within deprived dLGN layers. These results indicate that, although 10 days of darkness in adulthood does not enhance the susceptibility to 7 days of MD, darkness imposed near the trailing edge of the critical period can restore a heightened susceptibility to MD more typical of an earlier developmental stage. The loss of neurofilament in juveniles exposed to darkness prior to MD suggests that the enhanced capacity for structural plasticity is partially rooted in the ability of darkness to modulate molecules that inhibit plasticity. J. Comp. Neurol. 524:2643-2653, 2016. © 2016 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Kevin R Duffy
- Department of Psychology and Neuroscience, Dalhousie University Life Sciences Centre, Halifax, Nova Scotia, Canada, B3H 4R2
| | - Alexander J Lingley
- Department of Psychology and Neuroscience, Dalhousie University Life Sciences Centre, Halifax, Nova Scotia, Canada, B3H 4R2
| | - Kaitlyn D Holman
- Department of Psychology and Neuroscience, Dalhousie University Life Sciences Centre, Halifax, Nova Scotia, Canada, B3H 4R2
| | - Donald E Mitchell
- Department of Psychology and Neuroscience, Dalhousie University Life Sciences Centre, Halifax, Nova Scotia, Canada, B3H 4R2
| |
Collapse
|
12
|
Mitchell DE, MacNeill K, Crowder NA, Holman K, Duffy KR. Recovery of visual functions in amblyopic animals following brief exposure to total darkness. J Physiol 2015; 594:149-67. [PMID: 26449521 DOI: 10.1113/jp270981] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Accepted: 09/20/2015] [Indexed: 12/19/2022] Open
Abstract
KEY POINTS Occlusion of one eye of kittens (monocular deprivation) results in a severe and permanent loss of visual acuity in that eye, which parallels closely the vision loss characteristic of human amblyopia. We extended earlier work to demonstrate that amblyopic vision loss can be either blocked or erased very fast by a 10 day period of total darkness following a period of monocular deprivation that begins near birth and extends to at least 8 weeks of age. The parameters of darkness were strict because no visual recovery was observed after 5 days of darkness. In addition, short periods of light introduced each day during an otherwise 10 day period of darkness obliterated the benefits. Despite recovery of normal visual acuity, only one-quarter of the animals showed evidence of having attained normal stereoscopic vision. A period of total darkness may catalyse and improve treatment outcomes in amblyopic children. A 10 day period of total darkness has been shown to either block or erase the severe effects on vision of a prior short period of monocular deprivation (MD) in kittens depending on whether darkness is contiguous or is delayed with respect to the period of MD. We have extended these earlier findings from kittens for which the period of MD began at 1 month and lasted for 1 week to more clinically relevant situations where MD began near birth and lasted for ≥ 6 weeks. Despite the far longer MD and the absence of prior binocular vision, all animals recovered normal visual acuity in the previously deprived eye. As before, when the period of darkness followed immediately after MD, the vision of both eyes was initially very poor but, subsequently, the acuity of each eye increased gradually and equally to attain normal levels in ∼ 7 weeks. By contrast, when darkness was introduced 8 weeks after MD, the visual acuity of the deprived eye recovered quickly to normal levels in just 1 week without any change in the vision of the fellow (non-deprived) eye. Short (15 or 30 min) periods of illumination each day during an otherwise 10 day period of darkness obliterated all the benefits for vision, and a 5 day period of darkness was also completely ineffective. Measurements of depth perception indicated that, despite possessing normal visual acuity in both eyes, only about one-quarter of the animals showed evidence of having attained normal stereoscopic vision.
Collapse
Affiliation(s)
- Donald E Mitchell
- Department of Psychology and Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Katelyn MacNeill
- Department of Psychology and Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada.,Department of Orthoptics, IWK Hospital, Halifax, Nova Scotia, Canada.,Hospital for Sick Children, Toronto, Ontario, Canada
| | - Nathan A Crowder
- Department of Psychology and Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Kaitlyn Holman
- Department of Psychology and Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Kevin R Duffy
- Department of Psychology and Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
| |
Collapse
|