Search

Maturation of excitatory drive onto fast-spiking interneurons (FS INs) in the visual cortex has been implicated in the control of the timing of the critical period for ocular dominance plasticity. However, the mechanisms that regulate the strength of these synapses over cortical development are not understood. Here we use a mouse model to show that neuregulin (NRG) and the receptor tyrosine kinase erbB4 regulate the timing of the critical period. NRG1 enhanced the strength of excitatory synapses onto FS INs, which inhibited ocular dominance plasticity during the critical period but rescued plasticity in transgenics with hypoexcitable FS INs. Blocking the effects of endogenous neuregulin via inhibition of erbBs rescued ocular dominance plasticity in postcritical period adults, allowing recovery from amblyopia induced by chronic monocular deprivation. Thus, the strength of excitation onto FS INs is a key determinant of critical period plasticity and is maintained at high levels by NRG--erbB4 signaling to constrain plasticity in adulthood. [ABSTRACT FROM AUTHOR]

The primary visual cortex (V1) is widely used to study brain plasticity, which is not only crucial for normal brain function, such as learning and memory, but also for recovery after brain injuries such as stroke. In standard cage (SC) raised mice, experiencedependent ocular dominance (OD) plasticity in V1 declines with age and is compromised by a lesion in adjacent and distant cortical regions. In contrast, mice raised in an enriched environment (EE), exhibit lifelong OD plasticity and are protected from losing OD plasticity after a stroke-lesion in the somatosensory cortex. Since SC mice with an access to a running wheel (RW) displayed preserved OD plasticity during aging, we investigated whether physical exercise might also provide a plasticity promoting effect after a cortical stroke. To this end, we tested if adult RW-raised mice preserved OD plasticity after stroke and also if short-term running after stroke restored OD plasticity to SC mice. Indeed, unlike mice without a RW, adult RW mice continued to show OD plasticity even after stroke, and a 2 weeks RW experience after stroke already restored lost OD plasticity. Additionally, the experience-enabled increase of the spatial frequency and contrast threshold of the optomotor reflex of the open eye, normally lost after a stroke, was restored in both groups of RWmice. Our data suggest that physical exercise alone can not only preserve visual plasticity into old age, but also restore it after a cortical stroke. [ABSTRACT FROM AUTHOR]

In this paper, we analyzed the effect of ocular dominance on touch positions when users touched a three-dimensional (3D) object on a two-dimensional (2D) touch panel while watching a 3D display. We performed a psychophysical experiment where eight subjects (four right-eye-dominant and four left-eye-dominant) participated. When touching 3D objects with uncrossed disparities, touch positions were mainly influenced by ocular dominance and depth of the 3D image (P < 10^-189). For crossed disparities, touch positions were mainly influenced by ocular dominance (P < 10^-18). However, the depth of the 3D image had no significant effect on touch positions $(P = 0.783)$. Our findings can help to design more accurate and comfortable interfaces for 3D systems with touch feedback. [ABSTRACT FROM PUBLISHER]

Summary The primary visual cortex (V1) encodes a diverse set of visual features, including orientation, ocular dominance (OD), and spatial frequency (SF), whose joint organization must be precisely structured to optimize coverage within the retinotopic map. Prior experiments have only identified efficient coverage based on orthogonal maps. Here we used two-photon calcium imaging to reveal an alternative arrangement for OD and SF maps in macaque V1; their gradients run parallel but with unique spatial periods, whereby low-SF regions coincide with monocular regions. Next we mapped receptive fields and found surprisingly precise micro-retinotopy that yields a smaller point-image and requires more efficient inter-map geometry, thus underscoring the significance of map relationships. While smooth retinotopy is constraining, studies suggest that it improves both wiring economy and the V1 population code read downstream. Altogether, these data indicate that connectivity within V1 is finely tuned and precise at the level of individual neurons. [ABSTRACT FROM AUTHOR]

How the brain combines the neural representations of features that comprise an object in order to activate a coherent object memory is poorly understood, especially when the features are presented in different modalities (visual vs. auditory) and domains (verbal vs. nonverbal). We examined this question using three versions of a modified Semantic Object Retrieval Test, where object memory was probed by a feature presented as a written word, a spoken word, or a picture, followed by a second feature always presented as a visual word. Participants indicated whether each feature pair elicited retrieval of the memory of a particular object. Sixteen subjects completed one of the three versions (N = 48 in total) while their EEG were recorded simultaneously. We analyzed EEG data in four separate frequency bands (delta: 1–4 Hz, theta: 4–7 Hz; alpha: 8–12 Hz; beta: 13–19 Hz) using a multivariate data-driven approach. We found that alpha power time-locked to response was modulated by both cross-modality (visual vs. auditory) and cross-domain (verbal vs. nonverbal) probing of semantic object memory. In addition, retrieval trials showed greater changes in all frequency bands compared to non-retrieval trials across all stimulus types in both response-locked and stimulus-locked analyses, suggesting dissociable neural subcomponents involved in binding object features to retrieve a memory. We conclude that these findings support both modality/domain-dependent and modality/domain-independent mechanisms during semantic object memory retrieval. [ABSTRACT FROM AUTHOR]

Monocular deprivation evokes a prominent shift of neuronal responses in the visual cortex toward the open eye, accompanied by functional and structural synaptic rearrangements.This shift is reversible, but it is unknown whether the recovery happens at the level of individual neurons or whether it reflects a population effect.We used ratiometric Ca2+ imaging to follow the activity of the same excitatory layer 2/3 neurons in the mouse visual cortex over months during repeated episodes of ocular dominance (OD) plasticity.We observed robust shifts toward the open eye in most neurons. Nevertheless, these cells faithfully returned to their predeprivation OD during binocular recovery. Moreover, the initial network correlation structure was largely recovered, suggesting that functional connectivity may be regained despite prominent experience-dependent plasticity. [ABSTRACT FROM AUTHOR]

The extent to which brain structure is influenced by sensory input during development is a critical but controversial question. A paradigmatic system for studying this is the mammalian visual cortex. Maps of orientation preference (OP) and ocular dominance (OD) in the primary visual cortex of ferrets, cats and monkeys can be individually changed by altered visual input. However, the spatial relationship between OP and OD maps has appeared immutable. Using a computational model we predicted that biasing the visual input to orthogonal orientation in the two eyes should cause a shift of OP pinwheels towards the border of OD columns. We then confirmed this prediction by rearing cats wearing orthogonally oriented cylindrical lenses over each eye. Thus, the spatial relationship between OP and OD maps can be modified by visual experience, revealing a previously unknown degree of brain plasticity in response to sensory input. [ABSTRACT FROM AUTHOR]

In standard cage (SC)-raised mice, ocular dominance (OD) plasticity of the primary visual cortex (V1) induced by monocular deprivation (MD) is maximal in juveniles, declines in adults, and is absent beyond postnatal day (PD) 110. Raising mice in an enriched environment (EE) preserved a juvenile-like OD plasticity after 7 days of MD until at least PD196, mediated by reductions of deprived eye responses in V1. Whether the sensitive phase for OD plasticity can be prolonged into older age and whether long-term EE modifies visual abilities was not yet known. Here, we demonstrate that EE raising enables lifelong OD plasticity. In contrast to PD200 EE-mice, the preserved OD shift in both >PD400 and >PD700 EE-mice was mediated by increases in open eye responses in V1 (adult OD plasticity). When SC-mice were transferred to EE after PD110, OD plasticity was restored until PD922. Moreover, visual abilities tested by both optomotry and the visual water task and interindividual variability were not different between PD700 SC- and EE-mice. Taken together, EE raising enabled a lifelong OD plasticity but did not affect basic visual performance. [ABSTRACT FROM AUTHOR]

During an early phase of enhanced sensitivity called the critical period (CP), monocular deprivation causes a shift in the response of visual cortex binocular neurons in favor of the nondeprived eye, a process named ocular dominance (OD) plasticity. While the time course of the CP for OD plasticity can be modulated by genetic/pharmacological interventions targeting GABAergic inhibition, whether an increased sensory-motor experience can affect this major plastic phenomenon is not known. We report that exposure to environmental enrichment (EE) accelerated the closure of the CP for OD plasticity in the rat visual cortex. Histone H3 acetylation was developmentally regulated in primary visual cortex, with enhanced levels being detectable early in enriched pups, and chromatin immunoprecipitation revealed an increase at the level of the BDNF P3 promoter. Administration of the histone deacetylase inhibitor SAHA (suberoylanilide hydroxamic acid) to animals reared in a standard cage mimicked the increase in H3 acetylation observed in the visual cortex and resulted in an accelerated decay of OD plasticity. Finally, exposure to EE in adulthood upregulated H3 acetylation and was paralleled by a reopening of the CP. These findings demonstrate a critical involvement of the epigenetic machinery as a mediator of visual cortex developmental plasticity and of the impact of EE on OD plasticity. [ABSTRACT FROM AUTHOR]

Two incongruent images viewed by the two eyes cause binocular rivalry, during which observers perceive continuous alternations between these two visual images. Previous studies in both humans and monkeys have shown that the primary visual cortex (V1) plays a critical role in the rivalry perception. However, it is unclear whether the rivalry activity observed in VI relies on conscious influences. Here, we examine the responses of VI in monkeys under general anesthesia. With intrinsic signal optical imaging and single-trial analysis, alternating activation of ocular dominance columns in V1 was observed during binocularly incongruent stimulation. Left- and right-eye columns exhibited counterphase activation, which were modulated by stimulus features in ways similar to those found in conscious human observers. These observations indicated that binocular rivalry occurs in V1 without consciousness, suggesting that the low-level automatic mechanisms play a more important role than previously believed in handling visual ambiguities [ABSTRACT FROM AUTHOR]

Neuronal plasticity is essential to enable rehabilitation when the brain suffers from injury, such as following a stroke. One of the most established models to study cortical plasticity is ocular dominance (OD) plasticity in the primary visual cortex (V1) of the mammalian brain induced by monocular deprivation (MD). We have previously shown that OD-plasticity in adult mouse V1 is absent after a photothrombotic (PT) stroke lesion in the adjacent primary somatosensory cortex (S1). Exposing lesioned mice to conditions which reduce the inhibitory tone in V1, such as raising animals in an enriched environment or short-term dark exposure, preserved OD-plasticity after an S1-lesion. Here we tested whether modification of excitatory circuits can also be beneficial for preserving V1-plasticity after stroke. Mice lacking postsynaptic density protein-95 (PSD-95), a signaling scaffold present at mature excitatory synapses, have lifelong juvenile-like OD-plasticity caused by an increased number of AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) -silent synapses in V1 but unaltered inhibitory tone. In fact, using intrinsic signal optical imaging, we show here that OD-plasticity was preserved in V1 of adult PSD-95 KO mice after an S1-lesion but not in PSD-95 wildtype (WT)-mice. In addition, experience-enabled enhancement of the optomotor reflex of the open eye after MD was compromised in both lesioned PSD-95 KO and PSD-95 WT mice. Basic V1-activation and retinotopic map quality were, however, not different between lesioned PSD-95 KO mice and their WT littermates. The preserved OD-plasticity in the PSD-95 KO mice indicates that V1-plasticity after a distant stroke can be promoted by either changes in excitatory circuitry or by lowering the inhibitory tone in V1 as previously shown. Furthermore, the present data indicate that an increased number of AMPA-silent synapses preserves OD-plasticity not only in the healthy brain, but also in another experimental paradigm of cortical plasticity, namely the long-range influence on V1-plasticity after an S1-lesion. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the characteristics of macular ganglion cell-inner plexiform layer (GCIPL) thickness profiles associated with ocular dominance. Setting: Private practice, Seoul, Republic of Korea. Design: Comparative case-control study. Methods: Both eyes of 199 participants with no ophthalmic abnormalities were included. Participants were imaged by spectral-domain optical coherence tomography, and underwent dominant eye testing using a hole-in-a-card test (sighting dominance) at the same visit. Macular GCIPL, as well as circumpapillary retinal nerve fiber layer (RNFL) thickness were compared for individual patients, according to ocular dominance. Results: Ocular dominance occurred predominantly in the right eye (right vs. left: 72.36 vs. 27.60%; P < 0.001). In the comparison of macular GCIPL thickness, the average (81.27±5.01 μm vs. 80.66±6.31 μm in dominant vs. non-dominant eyes), inferonasal (81.39±5.47μm vs. 80.33±6.82μm, and inferior sectors (77.95±6.05μm vs. 76.97±8.15μm) were significantly different between dominant and non-dominant eyes (P = 0.040, 0.005, and 0.032, respectively). Significant predictors of average GCIPL thickness were spherical equivalent (β = 1.37, P<0.001), astigmatic power (β = 1.44, P = 0.009), disc area (β = 3.90, P < 0.001), average RNFL thickness (β = 0.22, P<0.001), average cup-to-disc ratio (β = 5.74, P = 0.002), difference between the inferior and superior quadrant RNFL thicknesses (β = 0.08, P = 0.024), and ocular dominance (β = 2.10, P = 0.020). On multivariate regression analysis, ocular dominance was correlated with average GCIPL thickness after adjusting for potential confounders (β = 1.63, P = 0.048). Conclusions: Dominant eyes accompanied significantly thicker average macular GCIPL. This information suggests that macular GCIPL thickness may provide an indicator of the relative dominance of an eye. [ABSTRACT FROM AUTHOR]

The distribution of callosal neurons in the cortical layers was studied in intact ( n = 7) and experimental cats with strabismus ( n = 10) or monocular deprivation ( n = 5) after microiontophoretic administration of horseradish peroxidase into the eye dominance columns of fields 17 and 18 and the fields 17/18 transitional zone. Callosal neurons in cats with impairments to binocular vision were located more deeply in layers II/III and more shallowly in layer IV than in intact cats. In addition, the proportion of callosal neurons in layer IV increased and the proportion in layer II/III decreased in cats with impaired binocular vision, as compared with intact cats, and these changes were more marked in monocular deprivation. These data point to the important role of sensory information in the formation of the laminar distribution of callosal neurons. [ABSTRACT FROM AUTHOR]

Purpose: To compare the ocular monochromatic higher‑order aberration (HOA) profile in normal refractive surgery candidates of Arab and South Asian origin. Methods: This cross‑sectional, observational, comparative study was performed in the cornea department of a specialty hospital. Normal refractive surgery candidates with no ocular morbidity except refractive error were recruited. Refractive surgery candidates underwent a preoperative evaluation, including wavefront aberrometry with the iDesign aberrometer (AMO, Inc., Santa Ana, California, United States). The HOA from right eyes were analyzed for HOA signed, absolute, and polar Zernike coefficients. Results: Two hundred Arab participants (group 1) and 200 participants of South‑Asian origin (group 2) comprised the study sample. The age and refractive status were comparable between groups. The mean of the HOA root mean square (RMS) was 0.36 ± 17 μ and 0.38 ± 18 μ for Arab and South‑Asian eyes, respectively (P < 0.05, rank sum test [RST]). Of the 22 higher order signed Zernike modes, only Z3−3, Z3−1, Z3 1, Z4−4, Z4−2, Z4 0, Z44, and Z5−5 were significantly different from zero (one sample t‑test, P < 0.002, with a Bonferroni correction of 0.05/22). All the signed and absolute Zernike terms were comparable between groups (RST, P > 0.002 [0.05/22]). The polar coefficients for coma, trefoil, spherical aberration, and tetrafoil were comparable between groups (P > 0.05, RST). Combined RMS values of third, fourth, fifth, and sixth order also were comparable between groups (P > 0.05, RST). Conclusions: Preoperative whole eye HOA were similar for refractive surgery candidates of Arab and South‑Asian origin. The values were comparable to historical data for Caucasian eyes and were lower than Asian (Chinese) eyes. These findings may aid in refining refractive nomograms for wavefront ablations [ABSTRACT FROM AUTHOR]

Introduction and Purpose: Anisometropia, a relative difference in the refractive state of the two eyes, is common in hyperopic patients. We investigated the association between ocular dominance (sighting dominance) and refractive asymmetry in patients with hyperopia. Methods: This retrospective study included 223 hyperopic patients with a mean age of 10.1 ± 3.6 years (range 3 to 21 years). Refractive error was measured with cycloplegic refraction, and axial length was measured with IOLMaster® (Carl Zeiss Meditec, Dublin, CA). Ocular dominance was assessed with the hole-in-the-card test. The amount of hyperopic anisometropia was subdivided into four groups: less than 0.50 D, 0.50-0.99 D, 1.00-1.99 D, and 2.00 D or greater. Results: Ocular dominance of the right and left eye was seen in 66% and 34% of the patients, respectively. The nondominant eye had higher hyperopia, astigmatism, and shorter axial length than the dominant eye (P < 0.001). In the group with spherical equivalent anisometropia of ⩾0.50 D in particular, the nondominant eye was significantly more hyperopic and had shorter axial length than the dominant eye (both P < 0.001). Conclusions: The current study revealed that the nondominant eye had a greater hyperopic refractive error and shorter axial length than the dominant eye, in patients who had a high degree of anisometropia in particular. [ABSTRACT FROM AUTHOR]

Maturation of cortical inhibition just after eye opening is a necessary precedent for the emergence of competitive, experience-dependent ocular dominance plasticity in the visual cortex. What inhibition is doing in this context, though, is not clear. Here I outline new hypotheses on the roles of somatic and dendritic inhibition in the opening and closure of critical periods, and their roles in the competitive processes therein. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study is to assess whether eye dominance may change after cataract surgery. Methods: This is a prospective case series. Cataract surgery candidates were examined prior to surgery for best-corrected visual acuity, eye dominance, and handedness. Patients with ocular conditions that may affect visual acuity were excluded from the study. A month following surgery, best-corrected visual acuity and eye dominance examinations were repeated. Results: The study included 33 patients with a mean age of 70.5±9.4 years. Eighteen patients (54.5%) had right eye dominance. Following surgery, seven patients (21.2%) had a change in eye dominance. The change in dominance was linked to improved visual acuity in the operated eye and to a younger age, although with no statistical significance. Conclusion: This is the first study reported in the literature to show that ocular dominance is a plastic characteristic following cataract surgeries. The results may change the importance given to eye dominance measurement prior to surgeries that rely on this examination, such as monovision surgeries. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the effect of upper blepharoplasty on eyebrow height, accounting for ocular dominance, fat excision, change in MRD1, and degree of dermatochalasis. Methods: Retrospective review of patients undergoing upper blepharoplasty between January 2013 and July 2014. Patients with a prior history of ocular trauma, disease, and surgery were excluded. Digital photographs were analyzed using NIH ImageJ software to measure pre and postoperative eyebrow height at the medial, central, and lateral positions, MRD1, and dermatochalasis. Univariable comparisons of brow height and MRD1 were performed. A multivariate analysis was used to assess for the effect of percentage change in MRD1 and dermatochalasis and of ocular dominance and fat excision in mean percentage change of eyebrow height. Results: Charts of 19 patients were reviewed. Mean age was 73.2 years (SD = 8.86). There were 9 male (47.4%) and 10 female (52.6%) patients. There were 11 right eye dominant (57.9%) and 8 left eye dominant (42.1%) patients. Then 13 patients (68.4%) underwent fat removal. A univariable comparison found insufficient evidence to suggest a significant change from 0 postoperatively in brow height at all positions. A multivariable comparison found insufficient evidence to suggest MRD1, ocular dominance, or dermatochalasis were significantly associated with mean percentage change in brow height at all positions with or without fat excision. Conclusion: Upper blepharoplasty does not change eyebrow height at the medial, central, or lateral positions, after accounting for any impact of ocular dominance, fat excision, change in MRD1, or degree of dermatochalasis. [ABSTRACT FROM AUTHOR]

Manipulation of the trunk midline has been shown to improve visuospatial performance in patients with unilateral visual neglect. The goal of the present study was to disentangle motor and perceptual components of egocentric midline manipulations and to investigate the contribution of individual hand preference. Two versions of visual temporal order judgment (TOJ) tasks were tested in healthy right- and left-handed subjects while trunk rotation was varied. In the congruent version, subjects were required to execute a saccade to the first of two horizontal stimuli presented with different stimulus onset asynchronies (SOA). In the incongruent version, subjects were required to perform a vertical saccade to a pre-learned color target, thereby dissociating motor response from the perceptual stimulus location. The main findings of this study are a trunk rotation and response direction specific impact on temporal judgments in form of a prior entry bias for right hemifield stimuli during rightward trunk rotation, but only in the congruent task. This trunk rotation-induced spatial bias was most pronounced in left-handed participants but had the same sign in the right-handed group. Results suggest that egocentric midline shifts in healthy subjects induce a spatially-specific motor, but not a perceptual, bias and underline the importance of taking individual differences in functional laterality such as handedness and mode of perceptual report into account when evaluating effects of trunk rotation in either healthy subjects or neurological patients. [ABSTRACT FROM AUTHOR]