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Disparity vergence is commonly viewed as being controlled by at least two mechanisms, an open-loop vergence-specific burst mechanism analogous to the ballistic drive of saccades, and a closed-loop feedback mechanism controlled by the... more
Disparity vergence is commonly viewed as being controlled by at least two mechanisms, an open-loop vergence-specific burst mechanism analogous to the ballistic drive of saccades, and a closed-loop feedback mechanism controlled by the disparity error. We show that human vergence dynamics for disparity jumps of a large textured field have a typical time course consistent with predominant control by the open-loop vergence-specific burst mechanism, although various subgroups of the population show radically different vergence behaviors. Some individuals show markedly slow divergence responses, others slow convergence responses, others slow responses in both vergence directions, implying that the two vergence directions have separate control mechanisms. The faster time courses usually had time-symmetric velocity waveforms implying open-loop burst control, while the slow response waveforms were usually time-asymmetric implying closed-loop feedback control. A further type of behavior seen in a distinct subpopulation was a compound anomalous divergence response consisting of an initial convergence movement followed by a large corrective divergence movement with time courses implying closed-loop feedback control. This analysis of the variety of human vergence responses thus contributes substantially to the understanding of the oculomotor control mechanisms underlying the generation of vergence movements.
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The study is an attempt to reveal the EEG frequency dynamic changes over sites covering areas reflecting the cognitive processes during movement imagery. Subjects were instructed to imagine a self-paced movement after listening to... more
The study is an attempt to reveal the EEG frequency dynamic changes over sites covering areas reflecting the cognitive processes during movement imagery. Subjects were instructed to imagine a self-paced movement after listening to randomized sentences differing in lack of object or instrument of action. EEG was recorded over frontal, sensorimotor and temporo-parietal areas in both hemispheres. Frequency dynamics was estimated using power spectra (PS), band-pass filtering and bispectra. Two types of frequency dynamics were established: (A) a linear one, up to 24 Hz, with most pronounced oscillations in 12-14 Hz and in 16-22 Hz, synchronized first in frontal and precentral areas; (B) a nonlinear one between 24 and 63 Hz, with fractal structure and self-similarity, characterized by fractal dimension of 1.7-1.9. The narrow band of 23-26 Hz in the boundary between linear and nonlinear regimes expressed obvious synchronization and time re-distribution of oscillations among sites and sentence-types.
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ABSTRACT
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Introduction:This study assessed whether basic spatial-cognitive abilities can be enhanced in people who are blind through transfer of learning from drawing training.Methods:Near-body spatial-cognitive performance was assessed through the... more
Introduction:This study assessed whether basic spatial-cognitive abilities can be enhanced in people who are blind through transfer of learning from drawing training.Methods:Near-body spatial-cognitive performance was assessed through the Cognitive Test for the Blind (CTB), which assesses a wide range of basic spatial-cognitive skills. The CTB was administered to 21 participants who are blind in two behavioral testing sessions separated by five days. For participants in the “trained” group, these intervening days were occupied by the Cognitive-Kinesthetic Drawing Training method, during which participants learned how to draw freehand from memory. The “control” participants were not trained.Results:The results showed significantly increased overall CTB performance in the trained but not in the control group, indicating that the drawing training effectively enhanced spatial-cognitive abilities. A three to six month follow-up session with a subset of trained participants suggested that these training-induced spatial-cognitive improvements might persist over time, at least for some tasks.Discussion:These findings demonstrate that learning to draw from memory without vision over just five sessions can lead to enhancement of basic spatial-cognitive abilities beyond the drawing task. This study is the first to examine the transfer of learning of cognitive ability in blind individuals.Implications for practitioners:This study sheds light on the Cognitive-Kinesthetic Drawing Training as an effective wide-range rehabilitation technique that could be used to enhance basic spatial-cognitive abilities in those who are blind.
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Attentional stances are particular ways in which the location of the source or seat of attention is situated within bodily experience. The goal of the study is to use this untapped cognitive resource to refine the construct of mindfulness... more
Attentional stances are particular ways in which the location of the source or seat of attention is situated within bodily experience. The goal of the study is to use this untapped cognitive resource to refine the construct of mindfulness by providing objective measurement and experimental control of these aspects of mindfulness. Location of the seat of attention, also described as self-location or egocenter, has been shown to have measurable impact on cognitive skill, emotional temperament, and selfconstrual, as well as social and moral attitudes. Our recent study has shown that the seat of attention can be volitionally self-regulated into various internal attentional stances that are stably associated with distinct patterns of cortical activation as measured with EEG. These results suggest that control of attentional stance should provide direct management of specific cognitive and emotional resources. Two specific global cognitive states associated with mindfulness are the positive emotional states of vipaśyanā and śamatha. The current study of the correlations of 11 attentional stances for with positive emotions reveal the association of vipaśyanā with a diffuse attentional stance centered on the abdomen, and śamatha with a focused attentional stance situated along the midline of the body. In addition to advancing denotation and differentiation of these two distinct elements of mindfulness, these results provide the opportunity for more efficient mindfulness training. Such opportunity would benefit anyone needing stress-reducing mindfulness training, and in particular, for underserved individuals in society who are most in need of stress management.
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This study provides evidence supporting the operation of a novel cognitive process of a somatic seat of attention, or ego-center, whose somatic location is under voluntary control and that provides access to differential emotional... more
This study provides evidence supporting the operation of a novel cognitive process of a somatic seat of attention, or ego-center, whose somatic location is under voluntary control and that provides access to differential emotional resources. Attention has typically been studied in terms of what it is directed toward, but it can also be associated with a localized representation in the body image that is experienced as the source or seat of attention—an aspect that has previously only been studied by subjective techniques. Published studies of this phenomenon under terms such as egocenter or self-location suggest that the seat of attention can be situated in various ways within the experienced body, resulting in what are here referred to as different attentional stances. These studies also provide evidence that changes in attentional stance are associated with differences in cognitive skill, emotional temperament, self-construal, and social and moral attitudes, as well as with access...
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Recently Mateeff and Hohnsbein (1996 Vision Research36 2873 – 2882) showed that the critical frequency for detection of modulated velocity of motion was invariant with respect to the viewing distance. The critical frequency was a function... more
Recently Mateeff and Hohnsbein (1996 Vision Research36 2873 – 2882) showed that the critical frequency for detection of modulated velocity of motion was invariant with respect to the viewing distance. The critical frequency was a function of the ratio between the mean velocity and the size of the aperture through which the motion was observed. In the present study we examined whether the velocity/aperture ratio affects velocity discrimination and detection of single velocity changes. Six subjects observed a random-dot pattern that could move within an invisible square aperture. In the discrimination task, two motions of 250 ms duration with slightly different velocities were presented with a 1 s interval between them. The subject had to report which of the motions was faster. In the change-detection task the same two motions were presented without an interval between them and the subject had to report whether the change was from a low to a high velocity or vice versa. Mean velocitie...
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The ultimate goal of functional brain imaging is to provide optimal estimates of the neural signals flowing through the long-range and local pathways mediating all behavioral performance and conscious experience. In functional MRI... more
The ultimate goal of functional brain imaging is to provide optimal estimates of the neural signals flowing through the long-range and local pathways mediating all behavioral performance and conscious experience. In functional MRI (Magnetic Resonance Imaging), despite its impressive spatial resolution, this goal has been somewhat undermined by the fact that the fMRI response is essentially a blood-oxygenation level dependent (BOLD) signal that only indirectly reflects the nearby neural activity. The vast majority of fMRI studies restrict themselves to describing the details of these BOLD signals and deriving non-quantitative inferences about their implications for the underlying neural activity. This Frontiers Research Topic welcomed empirical and theoretical contributions that focus on the explicit relationship of non-invasive brain imaging signals to the causative neural activity. The articles presented within this resulting eBook aim to both highlight the importance and improve the non-invasive estimation of neural signals in the human brain. To achieve this aim, the following issues are targeted: (1) The spatial limitations of source localization when using MEG/EEG. (2) The coupling of the BOLD signal to neural activity. Articles discuss how animal studies are fundamental in increasing our understanding of BOLD fMRI signals, analyze how non-neuronal cell types may contribute to the modulation of cerebral blood flow, and use modeling to improve our understanding of how local field potentials are linked to the BOLD signal. (3) The contribution of excitatory and inhibitory neuronal activity to the BOLD signal. (4) Assessment of neural connectivity through the use of resting state data, computational modeling and functional Diffusion Tensor Imaging (fDTI) approaches
Research Interests: Computer Science, Neuroimaging, Functional MRI, EEG, DTI, and 8 moreNeurovascular, MEG, Estimation, Human Brain, Connectivity, Rc, BOLD, and Q
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Abstract Introduction. Although a high proportion of the motion selective cells in non-human primate motion areas are disparity-selective, there is no convincing evidence for cells specific to stereomotion-in-depth, and the neural basis... more
Abstract Introduction. Although a high proportion of the motion selective cells in non-human primate motion areas are disparity-selective, there is no convincing evidence for cells specific to stereomotion-in-depth, and the neural basis of stereomotion processing remains obscure. However, recent fMRI studies in humans (Likova and Tyler, 2007) have revealed activity related to cyclopean stereomotion-in-depth (csMID; based entirely on temporal changes-in-disparity), with the earliest activation site in an occipito-temporal region ...
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While the brain network for Braille reading (BR) in the blind is well known, fMRI studies on Braille writing (BW) are lacking. Consequently, no comparative network analysis of BW vs. BR exists. Here, we report the first BW/BR study,... more
While the brain network for Braille reading (BR) in the blind is well known, fMRI studies on Braille writing (BW) are lacking. Consequently, no comparative network analysis of BW vs. BR exists. Here, we report the first BW/BR study, together with the effect of text familiarity on both. FMRI was conducted in a Siemens 3T Trio scanner. Our custom MRI-compatible drawing/writing tablet was further modified to provide for BR and BW. Each of five paragraphs of novel Braille text describing objects, faces and navigation sequences was read, then reproduced twice by writing from memory, then read a second time (20s/task). BR: During the initial reading (unfamiliar text), the tactually-sensed Braille letters strongly activated the classical grapheme area, but its activation was drastically reduced on the second reading (familiar text). Despite the lack of vision, visual areas (V1-3) were strongly activated during both readings. Interestingly, activation in key mirror neuron areas, including the anterior intraparietal sulcus (aIPS) and inferior frontal gyrus (IFG), significantly expanded as a function of the familiarity of the text, in contrast to the marked decrease in the grapheme area. Taken together, these patterns of activation imply a shift from detailed "visual" processing of Braille-letter forms to an embodied cognition interpretation of the same Braille text when familiar. BW: Braille writing engaged a significantly more extensive network than BR, particularly in the initial writing block. Also, in contrast to drawing in the blind (Likova, 2012), BW generated focal activation restricted to the most foveal part of V1, presumably reflecting the focal demands of such a precision task. This first study of the brain network for Braille writing-from-memory, its comparison to the Braille reading network, and the effects of text familiarity on them, further allows for comparison with visual writing/reading mechanisms. Meeting abstract presented at VSS 2015.