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1.
Temporally overlapping, spatially separated visual stimuli were used for studying perception of simultaneity and temporal order. Pairs of flashes each of 100 ms duration were presented with stimulus onset asynchronies of 0, 30, 50, and 70 ms. Three spatial arrangements of flash presentation were tested: 1) both flashes were presented foveally; 2) one flash was presented foveally and the other at 9 deg in the left visual hemifield; 3) one flash was presented foveally and the other at 8 deg in the right visual hemifield. Onset asynchronies of 30 and 50 ms were not sufficient for correct identification of temporal order although the flashes were not perceived as simultaneous. Analysis of the response distributions suggests the existence of two-independent mechanisms for evaluating temporal interrelations: one for detecting simultaneity and the other for identifying temporal order. A better detection of simultaneity was found when synchroneous flashes were presented together with pairs of flashes separated by larger onset asynchronies. Reading habits may explain only part of the left-right asymmetries of the response distributions. The possible lateralization of the two suggested mechanisms within the cerebral hemispheres is discussed. 相似文献
2.
Visual motion information from dynamic environments is important in multisensory temporal perception. However, it is unclear how visual motion information influences the integration of multisensory temporal perceptions. We investigated whether visual apparent motion affects audiovisual temporal perception. Visual apparent motion is a phenomenon in which two flashes presented in sequence in different positions are perceived as continuous motion. Across three experiments, participants performed temporal order judgment (TOJ) tasks. Experiment 1 was a TOJ task conducted in order to assess audiovisual simultaneity during perception of apparent motion. The results showed that the point of subjective simultaneity (PSS) was shifted toward a sound-lead stimulus, and the just noticeable difference (JND) was reduced compared with a normal TOJ task with a single flash. This indicates that visual apparent motion affects audiovisual simultaneity and improves temporal discrimination in audiovisual processing. Experiment 2 was a TOJ task conducted in order to remove the influence of the amount of flash stimulation from Experiment 1. The PSS and JND during perception of apparent motion were almost identical to those in Experiment 1, but differed from those for successive perception when long temporal intervals were included between two flashes without motion. This showed that the result obtained under the apparent motion condition was unaffected by the amount of flash stimulation. Because apparent motion was produced by a constant interval between two flashes, the results may be accounted for by specific prediction. In Experiment 3, we eliminated the influence of prediction by randomizing the intervals between the two flashes. However, the PSS and JND did not differ from those in Experiment 1. It became clear that the results obtained for the perception of visual apparent motion were not attributable to prediction. Our findings suggest that visual apparent motion changes temporal simultaneity perception and improves temporal discrimination in audiovisual processing. 相似文献
3.
Orekhov IuV Golikova ZhV Strelets VB 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》2004,54(5):612-619
We analyzed the spectral power of EEG rhythms and some psychological features in patients with depression (first episode) and in healthy subjects. In the control group, the distributions of the spectral power of the alpha3 and gamma rhythms was symmetrical. In reproducing joy, the power of the alpha3 rhythm increased in the occipital and that of the gamma rhythm increased in the temporal areas of the left hemisphere. In depressive patients, predominant activation of the left posterior cortical quadrant in the alpha3 band was observed both in the baseline activity and during reproducing emotions of both valences. In these patients, the gamma rhythm predominated in the anterior regions of the right hemisphere during rest. The mental reproduction of joy and grief in depressive patients shifted the maximal gamma rhythm spectral power to the occipital cortical regions. Thus, in depressive patients, any emotional load, regardless of its valence, results in a decrease in the pathologic gamma activity and makes the distribution of cortical electric activity more close to that of healthy subjects. 相似文献
4.
Strelets VB Garakh ZhB Novototskiĭ-Vlasov VIu Magomedov RA 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》2005,55(4):496-504
The work is aimed at the study of correlations between the measures of spectral power and cortical interactions of EEG rhythms in healthy subjects and schizophrenic patients ("acute" and chronic cases). All brain rhythms in healthy subjects appeared to be symmetrical and synchronous both in phase and frequency. In "acute" schizophrenics, opposite to healthy subjects, the distribution of cortical activity is asymmetrical, and in the chronic cases, the spectral power of most cortical rhythms is decreased as compared to healthy subjects. In the "acute" patients, interhemispheric connections are absent in all rhythms but alpha. In the chronic patients, the number of cortical connections is slightly higher than in the acute patients; and they are located in the posterior areas in the gamma rhythm. These neurophysiological aberrations evidently underlie the multiple mental activity disorders in schizophrenic patients. Thus, the correspondence between the brain rhythms and their synchronization is a necessary condition for normal perception, emotions and cognition evidently influencing behavior and consciousness. 相似文献
5.
The work is aimed at the study of neurophysiological mechanisms of examination stress in subjects with different levels of cortical activation. Spectral power and typical cortical connections of EEG rhythms were studied in students under conditions of stress before and immediately after examination as well as during usual academic semester. Students with relatively higher and relatively lower baseline alpha rhythm, i.e., with different levels of cortical activation revealed both similar and different EEG reactions. Before examination, in both groups of subjects the spectral power of EEG activity in the delta and thetal bands increased, and the number of connections in the bands of the alpha and beta 1 rhythms decreased as compared to usual baseline conditions. However, the EEG reactions in the theta 2 band in the two groups were oppositely directed. Significant changes in the beta 2 power were observed only in the group of subjects with higher baseline level of cortical activation. 相似文献
6.
O M Grindel' O B Sazonova S B Zhirov 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》1992,42(3):491-499
EEG study was conducted in the state of relative rest in 15 healthy subjects with predominance of the alpha rhythm. Data processing was performed on neuromapper ("Neuroscience", Great Britain). Principal attention was paid to the dynamics of spatial-temporal relations of the alpha rhythm. Cyclic changes were shown of the alpha-rhythm amplitude, proceeding with change of high and low amplitudes during seconds, varying in time in various individuals. Three types of spatial distribution of the alpha rhythm over the cortex at the relative rest were obtained: 1) generalized distribution over the cortex with the wavy shift of the frequency fields; 2) formation of delimited local zones of the alpha rhythm, differing by the frequency from the rhythm in other cortical areas; 3) local zone of the low-frequency alpha rhythm in the visual projection zone (18 and 19 fields). Change of the distribution types of the alpha rhythm in the state of rest takes place in the seconds of time intervals, corresponding, according to the literature data, to the proceeding of elementary mental processes. 相似文献
7.
The relative timing of presynaptic and postsynaptic spikes plays a critical role in activity-induced synaptic modification. Here we examined whether plasticity of orientation selectivity in the visual cortex depends on stimulus timing. Repetitive pairing of visual stimuli at two orientations induced a shift in orientation tuning of cat cortical neurons, with the direction of the shift depending on the temporal order of the pair. Induction of a significant shift required that the interval between the pair fall within +/-40 ms, reminiscent of the temporal window for spike timing-dependent synaptic plasticity. Mirroring the plasticity found in cat visual cortex, similar conditioning also induced a shift in perceived orientation by human subjects, further suggesting functional relevance of this phenomenon. Thus, relative timing of visual stimuli can play a critical role in dynamic modulation of adult cortical function, perhaps through spike timing-dependent synaptic plasticity. 相似文献
8.
E. A. Umryukhin T. D. Dzhebrailova I. I. Korobeinikova N. A. Karatygin 《Human physiology》2008,34(5):574-580
EEG correlates of individual differences in decision-making time were studied in subjects performing the task of memorizing and subsequently reproducing, on a monitor screen, a sequence of signals. Forty-six students were volunteers in the study, carried out with the use of an original computer-aided technique. Pioneering data on the individual specificity of physiological processes underlying human mental activity were obtained. Individual differences in EEG characteristics related to differences in the temporal parameters of the decision-making stage were found. In a situation directly preceding the activity, subjects characterized by a short decision-making time exhibited higher powers of the Δ (in the occipital, parietal, and central cortical areas) and θ-(in both the central and the right frontal and temporal areas) EEG rhythms. The subjects with a short decision-making time differed from those with a long decision-making time in a higher power of the θ rhythm in the right temporal area during memorization and an increased θ rhythm power in the frontal areas during reproduction of a signal sequence. 相似文献
9.
Bark ED Tokareva IuA Shevelev IA 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》2002,88(3):309-317
Dynamic study of the equivalent current dipoles (ECDs) of alpha rhythm in the human brain was performed in a one-dipole model. The number of ECDs was shown to be dependent on the time course of visual stimulation, on the phase shift of triggering of flickers with alpha-rhythm frequency from alpha-wave, as well as on the type of visual illusions produced in subjects by this stimulation. The data are discussed in accordance with the "scanning hypothesis" that predict a certain functional meaning of the spreading alpha-wave for cortical processing of sensory information in the human brain. 相似文献
10.
Kostandov EA Kurova NS Cheremushkin EA Petrenko NE 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》2007,57(1):33-42
Coherence function of the EEG in the bands of 8-13 (alpha rhythm) and 14-25 Hz (beta rhythm) was analyzed in 35 healthy adult subjects during formation and testing of a visual cognitive set to pictures of faces with different emotional expressions. The intra- and interhemispheric coherences of the potentials in the frontal area and coherence between the right frontal and temporal derivation were shown to increase at the stage of set actualization. The results of the analysis confirm the suggestion that the frontal cortical areas are predominantly involved in formation and actualization of the set to facial emotional expression. The conclusion is based on the idea that the spatial synchronization of the brain electrical potentials is an index of the functional relations between the corresponding cortical areas and their cooperative involvement in a certain kind of activity (their simultaneous activation). 相似文献
11.
Irene Bollig 《Planta》1977,135(2):137-142
The phase shifting effect of red light on both the leaf movement rhythm, and on the rhythm of responsiveness of photoperiodic flower induction towards short light breaks (10 min red light), has been studied in Pharbitis nil, strain Violet, and comparisons between the two rhythms have been made. The phase angle differences between the rhythms after a phase shift with 2 or 6 h of red light given at different times during a long dark period were not constant. The results indicate the involvement of two different clocks controlling leaf movement and photoperiodic flower induction.Abbreviations DD
continuous darkness
-
l:D x:y
light/dark cycles with x hours of light and y hours of darkness
- PPR
rhythm of photoperiodic responsiveness towards light break 相似文献
12.
Gerard J. Boer Henriëtte A. Griffioen Hans Duindam Tjitske P. van der Woude Wop J. Rietveld 《Biological Rhythm Research》2013,44(2):118-136
Summary Suprachiasmatic nucleus (SCN)‐lesioned rats which had received a fetal SCN graft were kept in constant red light for three months. After this period it was examined whether those rats that showed a recovered free‐running circadian rhythm could be entrained to light/dark cycles. To this end, they were subjected to a 12 h light/12 h dark schedule, followed by a 12 h light shift and again to dark conditions. In addition, the same regime was imposed on SCN‐grafted rats without recovered circadian rhythms and on sham‐grafted animals with a lesion, which were studied as controls. The presence of an SCN graft was identified immunocytochemically by the presence of vasopressin, vasoactive intestinal polypeptide and somatostatin cells. Drinking, eating and wheel‐running rhythms were found to synchronize to the light/dark cycles in all rats, not with standing the presence of an SCN graft was. A 12 h light shift was immediately followed by a shift in the three rhythms. Under final dark conditions, free‐running patterns reappeared in rhythm‐recovered animals, without any convincing evidence for entrainment of the rhythms in the pattern of transition. Behavioral rhythms in SCN‐lesioned rats are apparently masked by 12 h light/dark schedules via other visual pathways than the direct projection from the retina to the SCN. 相似文献
13.
E. I. Rodríguez-Martínez F. J. Ruiz-Martínez C. I. Barriga Paulino Carlos M. Gómez 《Cognitive neurodynamics》2017,11(1):23-33
It has been described that the frequency ranges at which theta, mu and alpha rhythms oscillate is increasing with age. The present report, by analyzing the spontaneous EEG, tries to demonstrate whether there is an increase with age in the frequency at which the cortical structures oscillate. A topographical approach was followed. The spontaneous EEG of one hundredand seventy subjects was recorded. The spectral power (from 0.5 to 45.5 Hz) was obtained by means of the Fast Fourier Transform. Correlations of spatial topographies among the different age groups showed that older groups presented the same topographical maps as younger groups, but oscillating at higher frequencies. The results suggest that the same brain areas oscillate at lower frequencies in children than in older groups, for a broad frequency range. This shift to a higher frequency with age would be a trend in spontaneous brain rhythm development. 相似文献
14.
The functional interrelationships of the brain structures of freely moving cats in generation of rhythmic EEG activity during the states of drowsiness and light sleep were evaluated using the claster analysis of mean values indexes of rhythms in different structures as well as correlation coefficients between them in time. It was shown that according these parameters visual cortical areas and lateral geniculate body appeared in different clusters. Lateral geniculate body suggested not to be the only pacemaker of EEG rhythms in visual cortex. The wide convergence of subcortical inputs to the visual cortex and possibility of autonomic generation of EEG rhythms at the cortical level are discussed as putative mechanisms of dissociation of EEG activities in visual cortex and thalamus. 相似文献
15.
To judge causality, organisms must determine the temporal order of their actions and sensations. However, this judgment may be confounded by changing delays in sensory pathways, suggesting the need for dynamic temporal recalibration. To test for such a mechanism, we artificially injected a fixed delay between participants' actions (keypresses) and subsequent sensations (flashes). After participants adapted to this delay, flashes at unexpectedly short delays after the keypress were often perceived as occurring before the keypress, demonstrating a recalibration of motor-sensory temporal order judgments. When participants experienced illusory reversals, fMRI BOLD signals increased in anterior cingulate cortex/medial frontal cortex (ACC/MFC), a brain region previously implicated in conflict monitoring. This illusion-specific activation suggests that the brain maintains not only a recalibrated representation of timing, but also a less-plastic representation against which to compare it. 相似文献
16.
We studied correlations between the frequency of background impulse activity (BIA) of dopaminergic (DAergic) neurons of the
ventral tegmentum (VT) and spectral power (SP) of the frequency components of EEG samples recorded in awake cats. The EEG
was recorded monopolarly (electrodes were fixed in the cranial bones) from the frontal, occipital, and right and left temporal
regions of the cortex. In a great majority of the cases, the BIA frequency of VT DA-ergic neurons demonstrated significant
positive correlations with changes in the SPs of the alpha and beta EEG rhythms. The closest correlations of the spiking frequency
of DA-ergic cells with the SP of the alpha rhythm was observed in the occipital region, while those with the beta SP were
found in the frontal area. Correlations of the activity of DA-ergic neurons with the SPs of the alpha and beta rhythms in
the left temporal cortical zone were closer, as compared with those in the symmetrical right zone. Correlations of the SPs
of the delta, theta, and gamma EEG components with the discharge frequency of VT DA neurons were of opposite directions, and
in most cases such correlations did not reach the level of significance. The results of this study show that, in some cases,
specific EEG patterns can be considered indicators of the state of the cerebral VT DA-ergic system.
Neirofiziologiya/Neurophysiology, Vol. 40, No. 4, pp. 359–367, July–August, 2008. 相似文献
17.
The filamentous fungus Neurospora crassa has frequently served as a model organism for the study of circadian rhythms through its ability to form conidial spores on a daily basis. This phenomenon leaves a spatial pattern of conidiation bands along a solid surface of agar after several days of growth. Using time-lapse video, the authors have quantified the rate of conidiation. They have found that conidia do not form at a specified lag time after the growth front is laid down, but rather the band region tends to simultaneously develop over a short time frame. This produces a sharp peak when the conidiation rate is plotted against time. In addition, the authors used time-lapse video to assay growth rate with greater accuracy than previously reported. It is usually assumed that Neurospora's rate of growth is constant, and this assumption of linear growth has been used extensively to determine period and phase of the conidiation circadian rhythm. The authors have confirmed an earlier report of nonlinear growth rate and have shown that the growth rate varies by a factor of about 2 with each circadian cycle. They have demonstrated that the errors in calculating times of conidiation peaks are maximally 1 to 2 h if linearity is assumed. The conidiation rate and growth rate rhythms are not apparent under conditions (using mutants or high or low temperatures) where the spatial banding rhythm is not observed. In light/dark entraining conditions, the conidiation rate and growth rate rhythms maintain the same phase relationship in different T-cycles. These data are consistent with the hypothesis that the growth rate rhythm is a consequence of the conidiation rate rhythm. 相似文献
18.
Background
The timing at which sensory input reaches the level of conscious perception is an intriguing question still awaiting an answer. It is often assumed that both visual and auditory percepts have a modality specific processing delay and their difference determines perceptual temporal offset.Methodology/Principal Findings
Here, we show that the perception of audiovisual simultaneity can change flexibly and fluctuates over a short period of time while subjects observe a constant stimulus. We investigated the mechanisms underlying the spontaneous alternations in this audiovisual illusion and found that attention plays a crucial role. When attention was distracted from the stimulus, the perceptual transitions disappeared. When attention was directed to a visual event, the perceived timing of an auditory event was attracted towards that event.Conclusions/Significance
This multistable display illustrates how flexible perceived timing can be, and at the same time offers a paradigm to dissociate perceptual from stimulus-driven factors in crossmodal feature binding. Our findings suggest that the perception of crossmodal synchrony depends on perceptual binding of audiovisual stimuli as a common event. 相似文献19.
Dietmar Weinert Heike Eimert Hans G. Erkert Ulrich Schneyer 《Chronobiology international》1994,11(4):222-231
Most of the extensive literature concerning the resynchronization of circadian rhythms after a Zeitgeber shift is devoted to the dependence of resynchronization on the mode of the shift and the strength of the Zeitgeber, as well as on the circadian function investigated. Ontogenetic influences have rarely been investigated. Therefore, we studied the resynchronization of several circadian rhythms in juvenile and adult female laboratory mice. We present here the results concerning the corticosterone rhythm. The daily rhythms were determined as transverse profiles (2-h intervals) before as well as 3, 7, and 14 days after an 8-h phase delay of the light/dark cycle produced by a single prolongation of dark time. The corticosterone concentration in serum was determined radioimmunologically. In the control animals the daily patterns were bimodal, with main maxima at the end of the light time and secondary ones just after lights on. Ontogenetic differences were small. In adult mice the amplitude was slightly increased due to an increase in the maximum values, and the time of highest hormone concentrations was slightly phase advanced. In juvenile mice, a distinct daily pattern with a phase position in relation to the light/dark cycle corresponding to that of control animals was present on the 3rd day after the Zeitgeber shift. The daily mean as well as the minimum and maximum values increased initially and reached the values of control animals during the second week. In adult animals, a pronounced daily rhythm with the normal phase position was present only at the 7th postshift day. The amplitude, daily mean, and maximum values were decreased, and the minimum values were increased. The initial values were not reached even after 2 weeks. The results show that resynchronization was faster in juvenile mice compared with adult mice. As a possible cause for the observed age-related differences, a not yet stabilized phase-coupling between various circadian rhythms is supposed. 相似文献
20.
Effects of constant darkness and constant light on circadian organization and reproductive responses in the ram 总被引:2,自引:0,他引:2
The relationship between circadian rhythms in the blood plasma concentrations of melatonin and rhythms in locomotor activity was studied in adult male sheep (Soay rams) exposed to 16-week periods of short days (8 hr of light and 16 hr of darkness; LD 8:16) or long days (LD 16:8) followed by 16-week periods of constant darkness (dim red light; DD) or constant light (LL). Under both LD 8:16 and LD 16:8, there was a clearly defined 24-hr rhythm in plasma concentrations of melatonin, with high levels throughout the dark phase. Periodogram analysis revealed a 24-hr rhythm in locomotor activity under LD 8:16 and LD 16:8. The main bouts of activity occurred during the light phase. A change from LD 8:16 to LD 16:8 resulted in a decrease in the duration of elevated melatonin secretion (melatonin peak) and an increase in the duration of activity corresponding to the changes in the ratio of light to darkness. In all rams, a significant circadian rhythm of activity persisted over the first 2 weeks following transfer from an entraining photoperiod to DD, with a mean period of 23.77 hr. However, the activity rhythms subsequently became disorganized, as did the 24-hr melatonin rhythms. The introduction of a 1-hr light pulse every 24 hr (LD 1:23) for 2 weeks after 8 weeks under DD reinduced a rhythm in both melatonin secretion and activity: the end of the 1-hr light period acted as the dusk signal, producing a normal temporal association of the two rhythms. Under LL, the 24-hr melatonin rhythms were disrupted, though several rams still showed periods of elevated melatonin secretion. Significant activity rhythms were either absent or a weak component occurred with a period of 24 hr. The introduction of a 1-hr dark period every 24 hr for 2 weeks after 8 weeks under LL (LD 23:1) failed to induce or entrain rhythms in either of the parameters. The occurrence of 24-hr activity rhythm in some rams under LL may indicate nonphotoperiodic entrainment signals in our experimental facility. Reproductive responses to the changes in photoperiod were also monitored. After pretreatment with LD 8:16, the rams were sexually active; exposure to LD 16:8, DD, or LL resulted in a decline in all measures of reproductive function. The decline was slower under DD than LD 16:8 or LL.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献