scholarly journals The Effect of Onset Age of Visual Deprivation on Visual Cortex Surface Area Across-Species

2018 ◽  
Vol 29 (10) ◽  
pp. 4321-4333 ◽  
Author(s):  
Adrian K Andelin ◽  
Jaime F Olavarria ◽  
Ione Fine ◽  
Erin N Taber ◽  
Daniel Schwartz ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Surface Area ◽  
Primary Visual Cortex ◽  
Final Analysis ◽  
Published Data ◽  
Brain Anatomy ◽  
Event Time ◽  
Longitudinal Measurements ◽  
Area Expansion ◽  
Reduced Surface

Abstract Blindness early in life induces permanent alterations in brain anatomy, including reduced surface area of primary visual cortex (V1). Bilateral enucleation early in development causes greater reductions in primary visual cortex surface area than at later times. However, the time at which cortical surface area expansion is no longer sensitive to enucleation is not clearly established, despite being an important milestone for cortical development. Using histological and MRI techniques, we investigated how reductions in the surface area of V1 depends on the timing of blindness onset in rats, ferrets and humans. To compare data across species, we translated ages of all species to a common neuro-developmental event-time (ET) scale. Consistently, blindness during early cortical expansion induced large (~40%) reductions in V1 surface area, in rats and ferrets, while blindness occurring later had diminishing effects. Longitudinal measurements on ferrets confirmed that early enucleation disrupted cortical expansion, rather than inducing enhanced pruning. We modeled the ET associated with the conclusion of the effect of blindness on surface area at maturity (ETc), relative to the normal conclusion of visual cortex surface area expansion, (ETdev). A final analysis combining our data with extant published data confirmed that ETc occurred well before ETdev.

Receptive field expansion in adult visual cortex is linked to dynamic changes in strength of cortical connections

1995 ◽  
Vol 74 (2) ◽  
pp. 779-792 ◽  
Author(s):  
A. Das ◽  
C. D. Gilbert
Keyword(s):  
Visual Cortex ◽  
Receptive Field ◽  
Primary Visual Cortex ◽  
Visual Space ◽  
Final Analysis ◽  
Before And After ◽  
On Line ◽  
Adult Cats ◽  
Visual Cortex Neurons ◽  
Cortical Connection

1. Receptive field (RF) sizes of neurons in adult primary visual cortex are dynamic, expanding and contracting in response to alternate stimulation outside and within the RF over periods ranging from seconds to minutes. The substrate for this dynamic expansion was shown to lie in cortex, as opposed to subcortical parts of the visual pathway. The present study was designed to examine changes in cortical connection strengths that could underlie this observed plasticity by measuring the changes in cross-correlation histograms between pairs of primary visual cortex neurons that are induced to dynamically change their RF sizes. 2. Visually driven neural activity was recorded from single units in the superficial layers of primary visual cortex in adult cats, with two independent electrodes separated by 0.1–5 mm at their tips, and cross-correlated on-line. The neurons were then conditioned by stimulation with an “artificial scotoma,” a field of flashing random dots filling the region of visual space around a blank rectangle enclosing the RFs of the recorded neurons. The neuronal RFs were tested for expansion and their visually driven output again cross-correlated. After this, the neurons were stimulated vigorously through their RF centers to induce the field to collapse, and the visually driven output from the collapsed RFs was again cross-correlated. Cross-correlograms obtained before and after conditioning, and after RF collapse, were normalized by their flanks to control for changes in peak size due solely to fluctuations in spike rate. 3. A total of 37 pairs of neurons that showed distinct cross-correlogram peaks, and whose RF borders were clearly discernible both before and after conditioning, were used in the final analysis. Of these neuron pairs, conditioning led to a clear expansion of RF boundaries in 28 pairs, whereas in 9 pairs the RFs did not expand. RFs that did expand showed no significant shifts in their orientation preference, orientation selectivity, or ocularity. 4. When the RFs of a pair of neurons expanded with conditioning, the area of the associated flank-normalized cross-correlogram peaks also increased (by a factor ranging from 0.84 up to 3.5). Correlograms returned to their preconditioning values when RFs collapsed.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Relationship Between the Visual Evoked Potential and Structure in the Primary Visual Cortex in Healthy Individuals and in Patients with Severe Mental Disorders

2021 ◽  
Author(s):  
Nora Berz Slapø ◽  
Kjetil Jørgensen ◽  
Torbjørn Elvsåshagen ◽  
Stener Nerland ◽  
Daniel Roelfs ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Mental Disorders ◽  
Structure Function ◽  
Surface Area ◽  
Primary Visual Cortex ◽  
Visual Evoked Potential ◽  
Evoked Potential ◽  
Healthy Individuals ◽  
Severe Mental Disorders ◽  
Function Relationship

Abstract Schizophrenia (SCZ) spectrum and bipolar disorder (BD) are severe mental disorders with unknown pathophysiology. Altered visual evoked potential (VEP), an electroencephalogram signal reflecting function in the primary visual cortex (V1), abnormal visual processing and visual hallucinations reported in these patients, all point towards V1 dysfunction. While the mechanisms contributing to V1 dysfunction remain unknown, structural alterations are possible candidates. Lack of insight into neural substrates of structure and functional in V1 has limited our ability to determine implications of altered V1 function. While combining VEP and magnetic resonance imaging has increased our understanding of the structure-function relationship in V1 in healthy individuals, no previous study has examined the same structure-function relationship in patients with SCZ spectrum and BD. Here, we aimed to confirm previous findings of a selective positive correlation between the amplitude of the P100 component of the VEP and V1 surface area (SA) in 307 healthy individuals and to examine whether this relationship was altered in patients with SCZ spectrum (n=30) and BD (n=45). The correlation between the P100 amplitude and the total, (r=0.16, p=0.006), right (r=0.14, p=0.013) and left V1 surface area (r=0.13, p=0.02) was significant in healthy individuals, but not in patients. The current results support previous findings of a selective relationship between P100 amplitude and V1 surface area in healthy individuals and suggests that other factors than V1 surface area or thickness explain V1 dysfunction reported in these patients.

scholarly journals STRUCTURAL CHANGES IN MICROCIRCULATORY VESSELS AND THEIR SURROUNDINGS IN THE PRIMARY VISUAL CORTEX OF 3- AND 18-MONTH-OLD RATS WITH RETINAL PHOTODAMAGE AND STRUCTURAL CHANGE CORRECTION

2020 ◽  
pp. 123-133
Author(s):  
Yu.O. Bakhareva ◽  
E.Yu. Varakuta ◽  
S.V. Logvinov ◽  
A.V. Potapov ◽  
A.A. Zhdankina ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Surface Area ◽  
Primary Visual Cortex ◽  
High Intensity ◽  
Light Exposure ◽  
Capillary Density ◽  
Male Rats ◽  
Capillary Surface ◽  
Glia Cells ◽  
Old Rats

Morphofunctional changes in microvasculature play an important role in the nerve cell plasticity, the ability to change their functional state under the influence of various factors. The aim of the research was to study the morphology of the microvasculature vessels, surrounding neurons and glia cells in the primary visual cortex of 3- and 18-month-old rats in norm and under stress caused by high-intensity twenty-four-hour light exposure, as well as under correction. Materials and Methods. The experiments were carried out on 60 Wistar male rats, aged 3- and 18-months. The authors used light and electron microscopy, and morphometry to evaluate: capillary surface area and density, surface area of altered vessels (due to stasis, sludge of formed elements and thrombosis) and unchanged ones, as well as the morphology of the surrounding cells. The Kruskal-Wallis test was used for multiple comparisons within age groups, while Mann-Whitney test was used for pair comparison. Results. The authors observed different capillary reactions to light exposure in 3- and 18-month-old rats. It resulted in an increase of capillary density in 3-month-old rats and in a decrease of capillary density in 18-month-old rats (p≤0.05). Destructive changes in neurons and glia cells were more evident in 18-month-old rats. P-tyrosol administration in 3- and 18-month-old rats with light exposure led to an increase in capillary density (p≤0.05). Under correction, young rats also demonstrated an increase in the capillary surface area, and the number of glia cells and capillaries by 1 neuron (p≤0.05). Conclusion Thus, p-tyrosol improved microvascularization in the primary visual cortex under high-intensity long-term light exposure. Keywords: microcirculation, p-tyrosol, stress, primary visual cortex. Морфофункциональные изменения микроциркуляторного русла играют важную роль в пластичности нервных клеток, их способности менять свое функциональное состояние при воздействии различных факторов. Целью исследования являлось изучение морфологии сосудов микроциркуляторного русла и окружающих их нейронов и глиоцитов в первичной зрительной коре 3- и 18-месячных крыс в норме и при стрессе, вызванном высокоинтенсивным круглосуточным световым воздействием, а также в условиях коррекции. Материалы и методы. Эксперименты выполнены на 60 крысах-самцах линии «Вистар». Возраст – 3 и 18 мес. Методами световой и электронной микроскопии, морфометрии оценивали удельную площадь и численную плотность капилляров, удельную площадь измененных (со стазом, сладжем форменных элементов и тромбозом) и неизмененных сосудов, а также морфологию клеток, их окружающих. Для множественных сравнений внутри возрастных групп использовали критерий Крускала–Уоллиса, для парных – Манна–Уитни. Результаты. У 3- и 18-месячных крыс обнаружена различная реакция капилляров на световое воздействие, что выражалось в увеличении численной плотности капилляров у 3-месячных крыс и снижении – у 18-месячных (р≤0,05). Деструктивные изменения нейронов и глиоцитов более выражены у 18-месячных крыс. Коррекция п-тирозолом у 3- и 18-месячных крыс со световым воздействием приводила к увеличению численной плотности капилляров (р≤0,05). У молодых крыс при коррекции также отмечалось увеличение удельной площади капилляров, количества глиоцитов и капилляров на 1 нейрон (р≤0,05). Заключение. Применение п-тирозола улучшало состояние микроваскуляризации в первичной зрительной коре в условиях высокоинтенсивного длительного светового воздействия. Ключевые слова: микроциркуляция, п-тирозол, стресс, первичная зрительная кора.

scholarly journals Structural changes to primary visual cortex in the congenital absence of cone input in achromatopsia

2021 ◽  
Author(s):  
Barbara Molz ◽  
Anne Herbik ◽  
Heidi A. Baseler ◽  
Pieter B. de Best ◽  
Richard Vernon ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Surface Area ◽  
Primary Visual Cortex ◽  
Structural Changes ◽  
Vision Loss ◽  
Time Window ◽  
Negative Impact ◽  
Congenital Absence ◽  
Grey Matter Volume ◽  
Multi Centre Study

Autosomal recessive Achromatopsia (ACHM) is a rare inherited disorder associated with dysfunctional cone photoreceptors resulting in a congenital absence of cone input to visual cortex. This might lead to distinct changes in cortical architecture with a negative impact on the success of gene augmentation therapies. To investigate the status of the visual cortex in these patients, we performed a multi-centre study focusing on the cortical structure of regions that normally receive predominantly cone input. Using high-resolution T1-weighted MRI scans and surface-based morphometry, we compared cortical thickness, surface area and grey matter volume in foveal, parafoveal and paracentral representations of primary visual cortex in 15 individuals with ACHM and 42 normally sighted, healthy controls (HC). In ACHM, surface area was reduced in all tested representations, while thickening of the cortex was found highly localized to the most central representation. These results were comparable to more widespread changes in brain structure reported in congenitally blind individuals, suggesting similar developmental processes, i.e., irrespective of the underlying cause and extent of vision loss. Our findings indicate that there may be an optimum time window for gene therapy to counteract developmental cortical changes related to the absence of sensory input.

Linking contrast sensitivity to cortical magnification in human primary visual cortex

2021 ◽  
Author(s):  
Marc M. Himmelberg ◽  
Jonathan Winawer ◽  
Marisa Carrasco
Keyword(s):  
Visual Cortex ◽  
Visual Perception ◽  
Contrast Sensitivity ◽  
Surface Area ◽  
Primary Visual Cortex ◽  
Fundamental Property ◽  
Polar Angle ◽  
Strongly Correlated ◽  
V1 Neurons ◽  
Cortical Magnification

ABSTRACTThe size and organization of primary visual cortex (V1) varies across individuals. Across neurotypical adults, V1 size varies more than twofold. Within individuals, surface area per unit of visual field – cortical magnification – varies with eccentricity and polar angle. Contrast sensitivity and cortical magnification covary with eccentricity, therefore it has been hypothesized that cortical magnification, specifically the number of activated V1 neurons, limits contrast sensitivity. Here, we quantify the relation between contrast sensitivity and V1 cortical magnification across observers and polar angle. We measured contrast sensitivity at four cardinal meridians in 29 observers. We then used fMRI to measure the size of V1 in the same observers, and the amount of surface area representing each of the four meridians (wedge-ROIs within 15° polar angle of the meridians, 1 to 8° eccentricity). We found that: First, an observer’s contrast sensitivity (averaged across polar angles) was predicted by the size of V1. Second, contrast sensitivity at each cardinal meridian was correlated with the surface area of the wedge-ROIs centered at the corresponding meridian. Third, increases in contrast sensitivity and cortical magnification at the horizontal compared to vertical meridian (horizontal-vertical anisotropy, ‘HVA’) were strongly correlated: a larger HVA in contrast sensitivity corresponded to a larger HVA in cortical magnification. These results reveal that contrast sensitivity and cortical magnification co-vary across observers and demonstrate a link between perceptual polar angle asymmetries and cortical anatomy. Broadly, the results show a link between visual perception and the idiosyncratic cortical organization of V1 in neurotypical observers.SIGNIFICANCE STATEMENTContrast sensitivity is a fundamental property of the human visual system, which indexes the limits of what one can detect or discriminate – the window of visibility. Contrast sensitivity varies with stimulus location on the retina and across observers. These variations are not well understood. Using psychophysics and magnetic resonance imaging, we tested the hypothesis that contrast sensitivity depends on the amount of responsive tissue in primary visual cortex (V1). Individuals with greater contrast sensitivity had a larger V1. Further, within observers, variation in contrast sensitivity across polar angle locations matched the variation in V1 surface area representing those locations. These findings demonstrate a tight link between visual perception and cortical anatomy, both within and among people.

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