196 research outputs found
Neuropsychological evidence for three distinct motion mechanisms
Published in final edited form as: Neurosci Lett. 2011 May 16; 495(2): 102–106. doi:10.1016/j.neulet.2011.03.048.We describe psychophysical performance of two stroke patients with lesions in distinct cortical regions in
the left hemisphere. Both patients were selectively impaired on direction discrimination in several local
and global second-order but not first-order motion tasks. However, only patient FD was impaired on a
specific bi-stable motion task where the direction of motion is biased by object similarity. We suggest
that this bi-stable motion task may be mediated by a high-level attention or position based mechanism
indicating a separate neurological substrate for a high-level attention or position-based mechanism.
Therefore, these results provide evidence for the existence of at least three motion mechanisms in the
human visual system: a low-level first- and second-order motion mechanism and a high-level attention
or position-based mechanism.Accepted manuscrip
Роман Ігоря Муратова “У сорочці народжений”: спроба аналізу
Ця стаття присвячена проблемі дослідження генезисних витоків та діалектиці
становлення центрального героя роману Ігоря Муратова “У сорочці народжений” Федора Коляди
та тих персонажів, які вплинули на розвиток його непересічного характеру. Відзначається високий
рівень майстерності письменника, що виражається у яскравих, індивідуальних образах. Також
розглядається короткий огляд тогочасного українського літературного процесу. Ґрунтовно
проаналізовано не тільки персонажів, але й назву роману та назви усіх п’яти розділів.
Ключові слова: час, місто, портрет, площина тексту, екстремальна ситуація, війна,
натура.Эта статья посвящается проблеме исследования генезисных истоков и диалектике
становления центрального героя романа Игоря Муратова “В сорочке рожденный” Федора Коляды
и тех персонажей, которые повлияли на развитие его незаурядного характера. Отмечается
высокий уровень мастерства писателя, что выражается в ярких, индивидуальных образах. Также
подается короткий обзор украинского литературного процесса того времени. Тщательно
проанализировано не только персонажи, а и название романа и названия всех пяти частей.
Ключевые слова: время, город, портрет, пространство текста, экстремальная ситуация,
война, натура.The article deals with the research of the genesis sources and development dialectics of Fedir
Kolyada – the main hero of the novel “Born with a silver spoon in his mouth” (“U sorotchtzi narodzheny”)
by Ihor Muratov – and other heroes, who influenced the progress of his outstanding character. The high
level writer’s skill, embodied in bright, individual images, is marked off. The paper presents a brief
review of the literary process of that period. It gives a deep analysis of not only the characters, but also
the titles of the novel and its five chapters.
Keywords: time, city, portrait, text level, extreme situation, war, nature
Gaze-contingent flicker pupil perimetry detects scotomas in patients with cerebral visual impairments or glaucoma
The pupillary light reflex is weaker for stimuli presented inside as compared to outside absolute scotomas. Pupillograph perimetry could thus be an objective measure of impaired visual processing. However, the diagnostic accuracy in detecting scotomas has remained unclear. We quantitatively investigated the accuracy of a novel form of pupil perimetry. The new perimetry method, termed gaze-contingent flicker pupil perimetry, consists of the repetitive on, and off flickering of a bright disk (2 hz; 320 cd/m; 4° diameter) on a gray background (160 cd/m) for 4 seconds per stimulus location. The disk evokes continuous pupil oscillations at the same rate as its flicker frequency, and the oscillatory power of the pupil reflects visual sensitivity. We monocularly presented the disk at a total of 80 locations in the central visual field (max. 15°). The location of the flickering disk moved along with gaze to reduce confounds of eye movements (gaze-contingent paradigm). The test lasted ~5 min per eye and was performed on 7 patients with cerebral visual impairment (CVI), 8 patients with primary open angle glaucoma (age >45), and 14 healthy, age/gender-matched controls. For all patients, pupil oscillation power (FFT based response amplitude to flicker) was significantly weaker when the flickering disk was presented in the impaired as compared to the intact visual field (CVI: 12%, AUC = 0.73; glaucoma: 9%, AUC = 0.63). Differences in power values between impaired and intact visual fields of patients were larger than differences in power values at corresponding locations in the visual fields of the healthy control group (CVI: AUC = 0.95; glaucoma: AUC = 0.87). Pupil sensitivity maps highlighted large field scotomas and indicated the type of visual field defect (VFD) as initially diagnosed with standard automated perimetry (SAP) fairly accurately in CVI patients but less accurately in glaucoma patients. We provide the first quantitative and objective evidence of flicker pupil perimetry's potential in detecting CVI-and glaucoma-induced VFDs. Gaze-contingent flicker pupil perimetry is a useful form of objective perimetry and results suggest it can be used to assess large VFDs with young CVI patients whom are unable to perform SAP
Gaze-Contingent Flicker Pupil Perimetry Detects Scotomas in Patients With Cerebral Visual Impairments or Glaucoma
Background: The pupillary light reflex is weaker for stimuli presented inside as compared to outside absolute scotomas. Pupillograph perimetry could thus be an objective measure of impaired visual processing. However, the diagnostic accuracy in detecting scotomas has remained unclear. We quantitatively investigated the accuracy of a novel form of pupil perimetry.Methods: The new perimetry method, termed gaze-contingent flicker pupil perimetry, consists of the repetitive on, and off flickering of a bright disk (2 hz; 320 cd/m2; 4° diameter) on a gray background (160 cd/m2) for 4 seconds per stimulus location. The disk evokes continuous pupil oscillations at the same rate as its flicker frequency, and the oscillatory power of the pupil reflects visual sensitivity. We monocularly presented the disk at a total of 80 locations in the central visual field (max. 15°). The location of the flickering disk moved along with gaze to reduce confounds of eye movements (gaze-contingent paradigm). The test lasted ~5 min per eye and was performed on 7 patients with cerebral visual impairment (CVI), 8 patients with primary open angle glaucoma (age >45), and 14 healthy, age/gender-matched controls.Results: For all patients, pupil oscillation power (FFT based response amplitude to flicker) was significantly weaker when the flickering disk was presented in the impaired as compared to the intact visual field (CVI: 12%, AUC = 0.73; glaucoma: 9%, AUC = 0.63). Differences in power values between impaired and intact visual fields of patients were larger than differences in power values at corresponding locations in the visual fields of the healthy control group (CVI: AUC = 0.95; glaucoma: AUC = 0.87). Pupil sensitivity maps highlighted large field scotomas and indicated the type of visual field defect (VFD) as initially diagnosed with standard automated perimetry (SAP) fairly accurately in CVI patients but less accurately in glaucoma patients.Conclusions: We provide the first quantitative and objective evidence of flicker pupil perimetry's potential in detecting CVI-and glaucoma-induced VFDs. Gaze-contingent flicker pupil perimetry is a useful form of objective perimetry and results suggest it can be used to assess large VFDs with young CVI patients whom are unable to perform SAP
Point-spread function of the BOLD response across columns and cortical depth in human extra-striate cortex
Columns and layers are fundamental organizational units of the brain. Well known examples of cortical columns are the ocular dominance columns (ODCs) in primary visual cortex and the column-like stripe-based arrangement in the second visual area V2.
The spatial scale of columns and layers is beyond the reach of conventional neuroimaging, but the advent of high field magnetic resonance imaging (MRI) scanners (UHF, 7 Tesla and above) has opened the possibility to acquire data at this spatial scale, in-vivo and non-invasively in humans.
The most prominent non-invasive technique to measure brain function is blood oxygen level dependent (BOLD) fMRI, measuring brain activity indirectly, via changes in hemodynamics. A key determinant of the ability of high-resolution BOLD fMRI to accurately resolve columns and layers is the point-spread function (PSF) of the BOLD response in relation to the spatial extent of neuronal activity.
In this study we take advantage of the stripe-based arrangement present in visual area V2, coupled with sub-millimetre anatomical and gradient-echo BOLD (GE BOLD) acquisition at 7 T to obtain PSF estimates and along cortical depth in human participants.
Results show that the BOLD PSF is maximal in the superficial part of the cortex (1.78 mm), and it decreases with increasing cortical depth (0.83 mm close to white matter)
Linear systems analysis for laminar fMRI: evaluating BOLD amplitude scaling for luminance contrast manipulations
A fundamental assumption of nearly all functional magnetic resonance imaging (fMRI) analyses is that the relationship between local neuronal activity and the blood oxygenation level dependent (BOLD) signal can be described as following linear systems theory. With the advent of ultra-high field (7T and higher) MRI scanners, it has become possible to perform sub-millimeter resolution fMRI in humans. A novel and promising application of sub-millimeter fMRI is measuring responses across cortical depth, i.e. laminar imaging. However, the cortical vasculature and associated directional blood pooling towards the pial surface strongly influence the cortical depth-dependent BOLD signal, particularly for gradient-echo BOLD. This directional pooling may potentially affect BOLD linearity across cortical depth. Here we assess whether the amplitude scaling assumption for linear systems theory holds across cortical depth. For this, we use stimuli with different luminance contrasts to elicit different BOLD response amplitudes. We find that BOLD amplitude across cortical depth scales with luminance contrast, and that this scaling is identical across cortical depth. Although nonlinearities may be present for different stimulus configurations and acquisition protocols, our results suggest that the amplitude scaling assumption for linear systems theory across cortical depth holds for luminance contrast manipulations in sub-millimeter laminar BOLD fMRI
Cortical depth dependent population receptive field attraction by spatial attention in human V1
Visual spatial attention concentrates neural resources at the attended location. Recently, we demonstrated that voluntary spatial attention attracts population receptive fields (pRFs) toward its location throughout the visual hierarchy. Theoretically, both a feed forward or feedback mechanism could underlie pRF attraction in a given cortical area. Here, we use sub-millimeter ultra-high field functional MRI to measure pRF attraction across cortical depth and assess the contribution of feed forward and feedback signals to pRF attraction. In line with previous findings, we find consistent attraction of pRFs with voluntary spatial attention in V1. When assessed as a function of cortical depth, we find pRF attraction in every cortical portion (deep, center and superficial), although the attraction is strongest in deep cortical portions (near the gray-white matter boundary). Following the organization of feed forward and feedback processing across V1, we speculate that a mixture of feed forward and feedback processing underlies pRF attraction in V1. Specifically, we propose that feedback processing contributes to the pRF attraction in deep cortical portions
Size constancy affects the perception and parietal neural representation of object size
Humans and animals rely on accurate object size perception to guide behavior. Object size is judged from visual input, but the relationship between an object's retinal size and its real-world size varies with distance. Humans perceive object sizes to be relatively constant when retinal size changes. Such size constancy compensates for the variable relationship between retinal size and real-world size, using the context of recent retinal sizes of the same object to bias perception towards its likely real-world size. We therefore hypothesized that object size perception may be affected by the range of recently viewed object sizes, attracting perceived object sizes towards recently viewed sizes. We demonstrate two systematic biases: a central tendency attracting perceived size towards the average size across all trials, and a serial dependence attracting perceived size towards the size presented on the previous trial. We recently described topographic object size maps in the human parietal cortex. We therefore hypothesized that neural representations of object size here would be attracted towards recently viewed sizes. We used ultra-high-field (7T) functional MRI and population receptive field modeling to compare object size representations measured with small (0.05-1.4°diameter) and large objects sizes (0.1-2.8°). We found that parietal object size preferences and tuning widths follow this presented range, but change less than presented object sizes. Therefore, perception and neural representation of object size are attracted towards recently viewed sizes. This context-dependent object size representation reveals effects on neural response preferences that may underlie context dependence of object size perception
Стилі керівництва як моделі вербальної поведінки у корпоративному дискурсі
Статья посвящена анализу лингвистических особенностей директивного и
демократического стилей руководства как распространенных моделей вербального поведения в корпоративном дискурсе. Внимание уделяется также
гендерному фактору, который учитывается при авторитарном коммуникативном поведении.Стаття присвячена аналізові лінгвістичних особливостей директивного та
демократичного стилів керівництва як поширених моделей вербальної поведінки у корпоративному дискурсі. Увага приділяється також гендерному фактору, який враховується в авторитарній комунікативній поведінці.The article is dedicated to the analysis of linguistic peculiarities of the directive
and democratic management styles as models of the verbal behaviour in the corporate
discourse. Attention is also paid to the gender factor, which is considered in the
authoritarian communicative behaviour
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