Eye movements and brain oscillations to symbolic safety signs with different comprehensibility

Background: The aim of this study was to investigate eye movements and brain oscillations to symbolic safety signs with different comprehensibility. Methods: Forty-two young adults participated in this study, and ten traffic symbols consisting of easy-to-comprehend and hard-to-comprehend signs were used as stimuli. During the sign comprehension test, real-time eye movements and spontaneous brain activity [electroencephalogram (EEG) data] were simultaneously recorded. Results: The comprehensibility level of symbolic traffic signs significantly affects eye movements and EEG spectral power. The harder to comprehend the sign is, the slower the blink rate, the larger the pupil diameter, and the longer the time to first fixation. Noticeable differences on EEG spectral power between easy-to-comprehend and hard-to-comprehend signs are observed in the prefrontal and visual cortex of the human brain. Conclusions: Sign comprehensibility has significant effects on real-time nonintrusive eye movements and brain oscillations. These findings demonstrate the potential to integrate physiological measures from eye movements and brain oscillations with existing evaluation methods in assessing the comprehensibility of symbolic safety signs.open

Task-related modulation of anterior theta and posterior alpha EEG reflects top-down preparation

<p>Abstract</p> <p>Background</p> <p>Prestimulus EEG alpha activity in humans has been considered to reflect ongoing top-down preparation for the performance of subsequent tasks. Since theta oscillations may be related to poststimulus top-down processing, we investigated whether prestimulus EEG theta activity also reflects top-down cognitive preparation for a stimulus.</p> <p>Results</p> <p>We recorded EEG data from 15 healthy controls performing a color and shape discrimination task, and used the wavelet transformation to investigate the time course and power of oscillatory activity in the signals. We observed a relationship between both anterior theta and posterior alpha power in the prestimulus period and the type of subsequent task.</p> <p>Conclusions</p> <p>Since task-differences were reflected in both theta and alpha activities prior to stimulus onset, both prestimulus theta (particularly around the anterior region) and prestimulus alpha (particularly around the posterior region) activities may reflect prestimulus top-down preparation for the performance of subsequent tasks.</p

A machine learning approach to predict perceptual decisions: an insight into face pareidolia

The perception of an external stimulus not only depends upon the characteristics of the stimulus but is also influenced by the ongoing brain activity prior to its presentation. In this work, we directly tested whether spontaneous electrical brain activities in prestimulus period could predict perceptual outcome in face pareidolia (visualizing face in noise images) on a trial-by-trial basis. Participants were presented with only noise images but with the prior information that some faces would be hidden in these images, while their electrical brain activities were recorded; participants reported their perceptual decision, face or no-face, on each trial. Using differential hemispheric asymmetry features based on large-scale neural oscillations in a machine learning classifier, we demonstrated that prestimulus brain activities could achieve a classification accuracy, discriminating face from no-face perception, of 75% across trials. The time–frequency features representing hemispheric asymmetry yielded the best classification performance, and prestimulus alpha oscillations were found to be mostly involved in predicting perceptual decision. These findings suggest a mechanism of how prior expectations in the prestimulus period may affect post-stimulus decision making

Right endometrioma is related with more extensive obliteration of the Douglas pouch

PubMed ID: 22198847Objective To investigate that endometrioma is an asymmetric disease with left lateral predisposition as compared to other benign ovarian cyst and also, whether endometrioma side is related with endometriosis severity. Methods Operative and histopathologic findings of 340 women who underwent cystectomy for treatment of endometriotic (n = 239) and nonendometriotic ovarian cysts (n = 101) by laparoscopy (n = 268) or laparotomy (n = 72) between January 2005 and August 2009 were evaluated retrospectively. We compared left and right sided distribution of endometriotic and nonendometriotic ovarian cysts, and we also investigated the extent of endometriotic foci, obliteration of pouch of Douglas and endometriosis stage according to the revised American Fertility Society classification of endometriosis to assess whether endometrioma side is related with the severity of endometriosis. Results Of 239 women with endometriosis, endometrioma was found in the left ovary (n = 109), right ovary (n = 58) and bilaterally (n = 72). Of 101 control group women functional and dermoid cysts were found in the left ovary (n = 48), right ovary (n = 43) and bilaterally (n = 10). Among women with unilateral ovarian endometrioma (n = 167) a left cyst (63.3%) was found more frequently than a right cyst (34.7%) (P < 0.0001). In women with a left ovarian endometrioma pouch of Douglas was open in 99 (90.8%) cases. However, it was partially obliterated in 3 (2.8%) and completely obliterated in 7 (6.4%) cases. On the other hand, in women with a right endometrioma it was open in 44 (75.9%) cases and partially obliterated in 2 (3.4%) and completely obliterated in 12 (20.7%) cases. In women with a right endometrioma, the possibility of the pouch of Douglas obliteration is significantly higher than the women with a left endometrioma (P = 0.006). Conclusion Moreover, we also showed that in women with a right endometrioma, incidence of the pouch of Douglas obliteration is higher and the endometriosis tends to be more severe compared to women with a left endometrioma. Our most relevant observation is obliteration of Douglas pouch which was found to be more extensive in women with right ovarian endometrioma. Our results showing left lateral predisposition of endometriomas are in agreement with the previous reports and highlight the retrograde menstruation theory for the pathogenesis of this enigmatic disorder. © Springer-Verlag 2011

Alpha rhythm of the EEG modulates visual detection performance in humans

The effects of the changes in the frequency spectrum of the electroencephalogram (EEG) on the perception of near-threshold visual stimuli and on the event-related potentials (ERPs) produced by these stimuli were investigated on 12 healthy volunteers. The stimulus intensity, at which each subject could detect 50% of the presented stimuli, was defined as the sensory threshold for that subject. Single ERP trials were separated into two groups: trials with detected and undetected stimuli. The ERPs and the average power spectra of the 1 s prestimulus periods were computed for both conditions. P300 amplitudes of the ERPs, and total power and relative band powers of the delta (0.5-4 Hz), theta (4-7.5 Hz), alpha (7.5-13 Hz), beta (13-30 Hz), and gamma (30-70 Hz) frequency bands of the prestimulus power spectra were measured. Between the two conditions, a specific difference was observed in the relative power of the alpha band, which was significantly lower before detected stimuli (p < 0.01) in line with significantly higher amplitudes of the ERPs (p < 0.001). These results show that short-lasting changes in brain's excitability state are reflected the relative alpha power of the EEG, which may explain significant variability in perceptual processes and ERP generation especially at boundary conditions such as sensory threshold. (C) 2004 Elsevier B.V. All rights reserved

Slow cortical potential shifts modulate P300 amplitude and topography in humans

Effects of the spontaneous slow cortical potential (SCP) shifts of the electroencephalogram (EEG) on the P300 response were investigated on ten healthy volunteers. P300 responses were recorded using an auditory oddball paradigm, where target stimuli were presented regularly after every four standard stimuli. Single event-related potential (ERP) sweeps exhibiting negative or positive SCP shifts were averaged separately. The P300 amplitude was significantly larger during negative SCP shifts. Furthermore, the topographies of P200 and P300 waves obtained during negative and positive SCP shifts showed significant differences. The results indicate that the SCP shifts in single ERP sweeps, which are considered to be correlated with the arousal or basic activity level of the cortex, explain at least part of the inter-trial variability of P300 response. (C) 1998 Elsevier Science ireland Ltd. All rights reserved