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1
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The role of lines and corners of geometric figures in recognition performance

100%
Shevelev I. A., Kamenkovich V. m., Sharaev G. A.
Acta Neurobiologiae Experimentalis
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2003
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vol. 63
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issue 4
361-368
EN
A relative role of lines and corners of images of outline geometric figures in recognition performance was studied psychophysically. Probability of correct response to the shape of the whole figure (control) and figures with lines or corners masked to a different extent was compared. Increase in the extent of masking resulted in a drop of recognition performance that was significantly lower for figures without corners, than for figures without part of their lines. The whole 3D figures were recognized better than 2D ones, whereas the opposite relations were observed under conditions of masking. Significant gender difference in a recognition performance was found: men recognize entire and partly masked figures better than women. Possible mechanisms of relatively better recognition of figures with corners than with lines are discussed in connection with finding of high sensitivity of many neurons in the primary visual cortex to line crossing and branching.
2
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The role of the thalamic reticular neurons in alpha- and gamma-oscillations in neocortex: a mechanism for selective perception and stimulus binding

80%
Skinner J. E., Molnar M., Kowalik Z. J.
Acta Neurobiologiae Experimentalis
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2000
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vol. 60
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issue 1
123-142
EN
The long-term objective is to understand how large masses of neurons in the brain process information during various learning and memory paradigms. Both time- and space-dependent processes have been identified in animals through computer-based analytic quantifications of event-related extracellular potentials. New nonlinear analyses have been introduced that presume that the fine-grain variation in the signal is determined and patterned in phase-space. Some neurons in the primary visual cortex manifest gamma-band oscillations. These cells show both a nonspecific phase-alignment (response synchrony) and a specific tuning (orientation tuning) when stimuli are presented to their receptive fields. This dual regulation of the sensory cells is proposed to underlie stimulus binding, a theoretical mechanism for 'object' perception. Nonlinear analytic results from gamma-activities in a simple model neuropil (olfactory bulb) suggest that neuroplasticity may arise through self-organization, a process in which a nonlinear change in the dynamics of the oscillatory field potentials is the hallmark. This self-organization may follow simple dynamical laws in which global cooperativity among the neurons is transiently brought about that, over trials, results in enduring changes in the nonlinear dynamics of some neurons. In conclusion, the sculpturing of the synaptic throughput in the sensory cortex (stimulus binding) may be associated with the irregular phases of the gamma-activities and may result from both specific and nonspecific systems operating together in a nonlinear self-organizing manner.
3
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Oscillatory cortical activities in the gamma band in the human EEG induced by visual stimuli - representation of the stimulus?

80%
Muller M. M.
Acta Neurobiologiae Experimentalis
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2000
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vol. 60
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issue 1
49-65
EN
The present work presents three experiments investigating cortical activities in the gamma band in humans. On the basis of theoretical models and animal experiments, synchronized oscillatory neuronal activity is discussed as the key mechanism by which the brain binds information processesed in different cortical areas to form a percept. Using an identical stimulation design - the same as used in animal studies - it was shown that induced gamma band responses in the EEG resemble the same features as those found in the intracortical recordings of animals. In addition, the present work demonstrates that these cortical activities are not higher harmonics of the alpha band and that they are senstive to the features of the stimulus. These results support the notion that gamma band activity is not just a by-product of neuronal activity and that alpha- and gamma band activies most certainly represent different cortical funtional states.
4
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Auditory perception of temporal order in centenarians in comparison with young and elderly subjects

80%
Kolodziejczyk I., Szelag E.
Acta Neurobiologiae Experimentalis
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2008
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vol. 68
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issue 3
373-381
EN
Temporal information processing controls many aspects of human mental activity and may be assessed by examining perception of temporal order in the tens of milliseconds time range. Although existing studies suggest an age-related decline in mental abilities, the data on the deterioration of temporal order perception seems inconsistent. Moreover, any evidence on subjects aged over 70 years is lacking. The present experiment aimed to extend the existing data to extremely old people. Temporal order judgment (TOJ) for auditory stimuli was tested across the life span of approx. 80 years, i.e. in young (mean age 22 years), elderly (66 years) and very old (101 years) subjects. Age-related deterioration of performance was observed, with slight changes in elderly subjects and significant deterioration in centenarians which was more distinct in women than in men. The results confirm age-related decrease in temporal resolution which may be explained by slowing of information processing or of a hypothetical internal-timing mechanism. These effects may be influenced by different strategies used in particular age groups.
5
Content available remote

Variability analysis of visual evoked potentials in humans by pattern recognition in phase domain

70%
Achimowicz J. Z.
Acta Neurobiologiae Experimentalis
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1995
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vol. 55
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issue 3
177-191
EN
A novel approach to single trial visually evoked potentials (VEP) variability analysis based on a new model of post-stimulus brain electrical activity is presented.The convolution model introduced by the autor is experimentally verified by the analysis of flash stimulus effects of EEG amplitude and phase spectra.Pattern recognition in the signal phase domain is proposed for detection of any time locked transient signals.This is illustrated by an application of a clustering algorithm in two-dimensional unwrapped phase of EEG Fourier transform space for occipitally recorded VEPs in human subjects.
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