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  • 1
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 15 March 2011, Vol.108(11), pp.4506-11
    Description: Perceptual learning not only improves sensitivity, but it also changes our subjective experience. However, the question of how these two learning effects relate is largely unexplored. Here we investigate how subjects learn to see initially indiscriminable metacontrast-masked shapes. We find that sensitivity and subjective awareness increase with training. However, sensitivity and subjective awareness dissociate in space: Learning effects on performance are lost when the task is performed at an untrained location in another quadrant, whereas learning effects on subjective awareness are maintained. This finding indicates that improvements in shape sensitivity involve visual areas up to V4, whereas changes in subjective awareness involve other brain regions. Furthermore, subjective awareness dissociates from sensitivity in time: In an early phase of perceptual learning, subjects perform above chance on trials that they rate as subjectively invisible. Later, this phenomenon disappears. Subjective awareness is thus neither necessary nor sufficient for achieving above-chance objective performance.
    Keywords: Learning -- Physiology ; Space Perception -- Physiology
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 2
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 2011, Vol.108(11), pp.4506-4511
    Description: Perceptual learning not only improves sensitivity, but it also changes our subjective experience. However, the question of how these two learning effects relate is largely unexplored. Here we investigate how subjects learn to see initially indiscriminable metacontrast-masked shapes. We find that sensitivity and subjective awareness increase with training. However, sensitivity and subjective awareness dissociate in space: Learning effects on performance are lost when the task is performed at an untrained location in another quadrant, whereas learning effects on subjective awareness are maintained. This finding indicates that improvements in shape sensitivity involve visual areas up to V4, whereas changes in subjective awareness involve other brain regions. Furthermore, subjective awareness dissociates from sensitivity in time: In an early phase of perceptual learning, subjects perform above chance on trials that they rate as subjectively invisible. Later, this phenomenon disappears. Subjective awareness is thus neither necessary nor sufficient for achieving above-chance objective performance. ; p. 4506-4511.
    Keywords: Space And Time ; Learning ; Brain
    ISSN: 0027-8424
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  • 3
    Article
    Article
    Language: English
    In: Trends in Cognitive Sciences, December 2013, Vol.17(12), pp.616-626
    Description: Recent discoveries on the organisation of the cortical connectome together with novel data on the dynamics of neuronal interactions require an extension of classical concepts on information processing in the cerebral cortex. These new insights justify considering the brain as a complex, self-organised system with nonlinear dynamics in which principles of distributed, parallel processing coexist with serial operations within highly interconnected networks. The observed dynamics suggest that cortical networks are capable of providing an extremely high-dimensional state space in which a large amount of evolutionary and ontogenetically acquired information can coexist and be accessible to rapid parallel search.
    Keywords: Cerebral Cortex ; Nonlinear Dynamics ; Oscillations ; Synchrony ; Reservoir Computing ; Computer Science ; Anatomy & Physiology ; Psychology
    ISSN: 1364-6613
    E-ISSN: 1879-307X
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  • 4
    Language: English
    In: Neuron, 2011, Vol.69(2), pp.191-193
    Description: The cerebral cortex consists of numerous, densely interconnected, functionally specialized areas that need to cooperate in ever-changing constellations depending on the actual cognitive or executive task. One way to achieve this dynamic coordination could be phase-locking of synchronized oscillatory activity. In this issue of , Hipp et al. provide supportive evidence by analyzing EEG signals associated with an ambiguous audiovisual discrimination task.
    Keywords: Biology ; Anatomy & Physiology
    ISSN: 0896-6273
    E-ISSN: 1097-4199
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  • 5
    Language: English
    In: International Journal of Psychophysiology, September 2012, Vol.85(3), pp.279-279
    Keywords: Anatomy & Physiology ; Psychology
    ISSN: 0167-8760
    E-ISSN: 1872-7697
    Source: ScienceDirect Journals (Elsevier)
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  • 6
    Language: English
    In: Biological Psychiatry, 15 June 2015, Vol.77(12), pp.1001-1009
    Description: A considerable body of work over the last 10 years combining noninvasive electrophysiology (electroencephalography/magnetoencephalography) in patient populations with preclinical research has contributed to the conceptualization of schizophrenia as a disorder associated with aberrant neural dynamics and disturbances in excitation/inhibition balance. This complements previous research that has largely focused on the identification of abnormalities in circumscribed brain regions and on disturbances of dopaminergic mechanisms as a cause of positive symptoms and executive deficits. In the current review, we provide an update on studies focusing on aberrant neural dynamics. First, we discuss the role of rhythmic activity in neural dynamics and in the coordination of distributed neuronal activity into organized neural states. This is followed by an overview on the current evidence for impaired neural oscillations and synchrony in schizophrenia and associated abnormalities in gamma-aminobutyric acidergic and glutamatergic neurotransmission. Finally, we discuss the distinction between fundamental symptoms, which are reflected in cognitive deficits, and psychotic, accessory symptoms, the latter likely constituting a compensatory response for aberrant neuronal dynamics.
    Keywords: Cognition ; Development ; Dynamics ; Neural Oscillations ; Schizophrenia ; Translational Research ; Medicine ; Biology ; Chemistry
    ISSN: 0006-3223
    E-ISSN: 1873-2402
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  • 7
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 13 March 2012, Vol.109(11), pp.4302-7
    Description: Gamma-band synchronization adjusts the timing of excitatory and inhibitory inputs to a neuron. Neurons in the visual cortex are selective for stimulus orientation because of dynamic interactions between excitatory and inhibitory inputs. We hypothesized that these interactions and hence also orientation selectivity vary during the gamma cycle. We determined for each spike its phase relative to the gamma cycle. As a function of gamma phase, we then determined spike rates and their orientation selectivity. Orientation selectivity was modulated by gamma phase. The firing rate of spiking activity that occurred close to a neuron's mean gamma phase of firing was most orientation selective. This stimulus-selective signal could best be conveyed to postsynaptic neurons if it were not corrupted by noise correlations. Noise correlations between firing rates were modulated by gamma phase such that they were not statistically detectable for the spiking activity occurring close to a neuron's mean gamma phase of firing. Thus, gamma-band synchronization produces spiking activity that carries maximal stimulus selectivity and minimal noise correlation in its firing rate, and at the same time synchronizes this spiking activity for maximal impact on postsynaptic targets.
    Keywords: Noise ; Cortical Synchronization -- Physiology ; Haplorhini -- Physiology ; Orientation -- Physiology ; Visual Cortex -- Physiology ; Wakefulness -- Physiology
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 8
    Language: English
    In: Trends in Cognitive Sciences, June 2015, Vol.19(6), pp.329-338
    Description: In animal models the neural basis of cognitive and executive processes has been studied extensively at various hierarchical levels from microcircuits to distributed functional networks. This work already provides compelling evidence that diverse cognitive functions are based on similar basic neuronal mechanisms. More recent data suggest that even cognitive functions realized only in human brains rely on these canonical neuronal mechanisms. Here we argue that language, like other cognitive functions, depends on distributed computations in specialized cortical areas forming large-scale dynamic networks and examine to what extent empirical results support this view.
    Keywords: Language ; Oscillation ; Neural Networks ; Computer Science ; Anatomy & Physiology ; Psychology
    ISSN: 1364-6613
    E-ISSN: 1879-307X
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  • 9
    Language: English
    In: Trends in Cognitive Sciences, February 2013, Vol.17(2), pp.54-55
    Description: Gamma oscillations in the brain should not be conceptualized as a sine wave with constant oscillation frequency. Rather, these oscillations serve to concentrate neuronal discharges to particular phases of the oscillation cycle and thereby provide the substrate for various, functionally relevant synchronization phenomena.
    Keywords: Computer Science ; Anatomy & Physiology ; Psychology
    ISSN: 1364-6613
    E-ISSN: 1879-307X
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  • 10
    Language: English
    In: Current Biology, 2011, Vol.21(17), pp.1494-1499
    Description: The right and left visual hemifields are represented in different cerebral hemispheres and are bound together by connections through the corpus callosum. Much has been learned on the functions of these connections from split-brain patients [ ], but little is known about their contribution to conscious visual perception in healthy humans. We used diffusion tensor imaging and functional magnetic resonance imaging to investigate which callosal connections contribute to the subjective experience of a visual motion stimulus that requires interhemispheric integration. The “motion quartet” is an ambiguous version of apparent motion that leads to perceptions of either horizontal or vertical motion [ ]. Interestingly, observers are more likely to perceive vertical than horizontal motion when the stimulus is presented centrally in the visual field [ ]. This asymmetry has been attributed to the fact that, with central fixation, perception of horizontal motion requires integration across hemispheres whereas perception of vertical motion requires only intrahemispheric processing [ ]. We are able to show that the microstructure of individually tracked callosal segments connecting motion-sensitive areas of the human MT/V5 complex (hMT/V5+; [ ]) can predict the conscious perception of observers. Neither connections between primary visual cortex (V1) nor other surrounding callosal regions exhibit a similar relationship. ► Individual characteristics of interhemispheric motion processing are stable over time ► Characteristics of transcallosal hMT/V5+ connections predict subjective experience
    Keywords: Biology
    ISSN: 0960-9822
    E-ISSN: 1879-0445
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