КЛІНІЧНИЙ ВИПАДОК МОЖЛИВОЇ МІГРЕНІ З АУРОЮ, УСКЛАДНЕНОЇ МІГРЕНОЗНИМ ІНФАРКТОМ

We present a clinical case of ischemic stroke in a man with a new-onset migraine attack. Clinical case. A 25-year-old man was admitted to the acute cerebrovascular department due to severe throbbing headache in the left temporal area, vomiting, impaired vision on the right and numbness of the right leg. Complaints appeared abruptly in the form of scotoma in the right visual field. 20 minutes later, severe throbbing headache, nausea and numbness of the right leg developed. The event was preceded by sleep deprivation for 2 days. The patient’s mother has migraine with aura. Previously, the patient never had such attacks. On examination: right-sided homonymous upper-quadrant hemianopsia, hypoesthesia of the right leg. Brain MRI - focal hyperintensity at T2 and DWI in the left occipital region (acute ischemic stroke). The patient took aspirin at a dose of 300 mg for the first day, then 100 mg per day and valproic acid at a dose of 1200 mg per day. Two days after hospitalization, the patient experienced recovery of sensitivity in the right leg and regression of right-sided homonymous upper quadrant hemianopsia to small scotoma. The patient was discharged on the 5th day with a small right scotoma. It is recommended to continue taking aspirin 100 mg/day and valproic acid 1200 mg/day for the secondary prevention of migraine attacks and stroke. Discussion. The peculiarities of this case include the lack of history of migraine (at least 5 or more migrainous headache attacks) and the development of severe migraine attack with prolonged aura symptoms, which was triggered by sleep deprivation and eventually evolved into ischemic stroke. Conclusions. It is necessary to consider the possibility of ischemic stroke even in the cases of a new-onset migraine attack. If migrainous aura duration exceeds 60 minutes, it is necessary to perform a brain MRI to detect the early signs of cerebral ischemia.

Optimizing a left and right visual field biphasic stimulation paradigm for SSVEP-based BCIs with hairless region behind the ear

Objective. Steady-state visual evoked potential (SSVEP) based brain-computer interface (BCI) has the characteristics of fast communication speed, high stability, and wide applicability, thus it has been widely studied. With the rapid development in paradigm, algorithm, and system design, SSVEP-BCI is gradually applied in clinical and real-life scenarios. In order to improve the ease of use of the SSVEP-BCI system, many studies have been focusing on developing it on the hairless area, but due to the lack of redesigning the stimulation paradigm to better adapt to the new area, the EEG response in the hairless area is worse than occipital region. Approach. This study first proposed a phase difference estimation method based on stimulating the left and right visual field separately, then developed and optimized a left and right visual field biphasic stimulation paradigm for SSVEP-based BCIs with hairless region behind the ear. Main results. In the 12-target online experiment, after a short model estimation training, all sixteen subjects used their best stimulus condition. The paradigm designed in this study can increase the proportion of applicable subjects for the behind-ear SSVEP-BCI system from 58.3% to 75% and increase the accuracy from 74.6±20.0% (the existing best SSVEP stimulus with hairless region behind the ear) to 84.2±14.7%, and the ITR from 14.2±6.4bits/min to 17.8±5.7bits/min. Significance. These results demonstrated that the proposed paradigm can effectively improve the BCI performance using the signal from the hairless region behind the ear, compared with the standard SSVEP stimulation paradigm.

Spatial attention in encoding letter combinations

Reading requires the correct identification of letters and letter positions within words. Selective attention is, therefore, required to select chunks of the text for sequential processing. Despite the extensive literature on visual attention, the well-known effects of spatial cues in simple perceptual tasks cannot inform us about the role of attention in a task as complex as reading. Here, we systematically manipulate spatial attention in a multi-letter processing task to understand the effects of spatial cues on letter encoding in typical adults. Overall, endogenous (voluntary) cue benefits were larger than exogenous (reflexive). We show that cue benefits are greater in the left than in the right visual field and larger for the most crowded letter positions. Endogenous valid cues reduced errors due to confusing letter positions more than misidentifications, specifically for the most crowded letter positions. Therefore, shifting endogenous attention along a line of text is likely an important mechanism to alleviate the effects of crowding on encoding letters within words. Our results help set the premise for constructing theories about how specific mechanisms of attention support reading development in children. Understanding the link between reading development and attention mechanisms has far-reaching implications for effectively addressing the needs of children with reading disabilities.

The spotlight of attention turns from rhythmic exploration-exploitation to a stable exploitation state

While traditional studies claim that visuospatial attention stays fixed at one location at a time, recent research has rather shown that attention rhythmically fluctuates between different locations at rates of prominent brain rhythms. However, little is known about the temporal dynamics of this fluctuation and, particularly, whether it changes over time. Thus, we addressed this question by investigating how visuospatial attention behaves over space and time. We recorded electroencephalographic activity of twenty-seven human participants while they performed a visuospatial cueing task, where attention was covertly oriented to the left or right visual field. In order to decode the spatial locus of attention from neural activity, we trained and tested a classifier on every timepoint of the orienting period, from the attentional cue to stimulus onset. This resulted in one temporal generalization matrix per participant, which was time-frequency decomposed to identify the sampling rhythm. Finally, a searchlight analysis was conducted to reveal the brain regions responsible for attention allocation. Our results show a dynamic evolution of the attentional spotlight, distinguishing between two states. In an early time window, attention explored both cued and uncued hemifield rhythmically at ~10 Hz. In a later time window attention focused on the cued hemifield. Classification was driven by occipital sources, while frontal regions exclusively became involved just before the spotlight settled onto the cued location. Together, our results define attentional sampling as a quasi-rhythmic dynamic process characterized by an initial rhythmic exploration-exploitation state, which is followed by a stable exploitation state.

The Role of Emotional Content in the Control of Eye Movements

<p>The anti-saccade paradigm has been a favourite among researchers of attention and the control of eye movements. Most pro/anti-saccade studies have utilized meaningless stimuli, though stimulus meaning is known to have an impact on looking behaviour in free viewing conditions. Here, we explore the role of content in the control of pro/antisaccades by contrasting two alternative views on the impact of emotional stimuli. One view supports an "informativeness" hypothesis, where visual processing is directed towards threatening stimuli, suggesting that RT should be particularly large for negative, high arousal pictures in an antisaccade task. An alternative view emphasizes approach and withdrawal behaviours. Here negative images are thought to encourage avoidance behaviours, causing faster RTs for antisaccades; whereas positive pictures encourage approach behaviours, causing faster RTs for prosaccades. Participants performed an antisaccade task in which they were presented with an image to the left or right visual field and instructed to look at or away from the image. The experimental design included five groups of images, with a factorial combination of valence (positive or negative) and arousal (high or low), and a neutral condition. In Experiments one and two the instruction was given 200 ms before the picture was presented and did not produce any effects of emotional content. Thus, if participants are given advanced notice of the upcoming saccade, the initiation of that saccade is not influenced by the emotional content of the target image. In experiments three and four, the cue was presented 200 ms after the onset of the target image. This change of SOA provided an effect of emotional content was observed in experiments three and four which was illustrated by slowed RTs for both pro- and anti-saccades. However erotic images appeared to slow down latencies across both saccades which were accompanied by high error rates.</p>

The Role of Emotional Content in the Control of Eye Movements

<p>The anti-saccade paradigm has been a favourite among researchers of attention and the control of eye movements. Most pro/anti-saccade studies have utilized meaningless stimuli, though stimulus meaning is known to have an impact on looking behaviour in free viewing conditions. Here, we explore the role of content in the control of pro/antisaccades by contrasting two alternative views on the impact of emotional stimuli. One view supports an "informativeness" hypothesis, where visual processing is directed towards threatening stimuli, suggesting that RT should be particularly large for negative, high arousal pictures in an antisaccade task. An alternative view emphasizes approach and withdrawal behaviours. Here negative images are thought to encourage avoidance behaviours, causing faster RTs for antisaccades; whereas positive pictures encourage approach behaviours, causing faster RTs for prosaccades. Participants performed an antisaccade task in which they were presented with an image to the left or right visual field and instructed to look at or away from the image. The experimental design included five groups of images, with a factorial combination of valence (positive or negative) and arousal (high or low), and a neutral condition. In Experiments one and two the instruction was given 200 ms before the picture was presented and did not produce any effects of emotional content. Thus, if participants are given advanced notice of the upcoming saccade, the initiation of that saccade is not influenced by the emotional content of the target image. In experiments three and four, the cue was presented 200 ms after the onset of the target image. This change of SOA provided an effect of emotional content was observed in experiments three and four which was illustrated by slowed RTs for both pro- and anti-saccades. However erotic images appeared to slow down latencies across both saccades which were accompanied by high error rates.</p>

Direct comparison of contralateral bias and face/scene selectivity in human occipitotemporal cortex

Human visual cortex is organised broadly according to two major principles: retinotopy (the spatial mapping of the retina in cortex) and category-selectivity (preferential responses to specific categories of stimuli). Historically, these principles were considered anatomically separate, with retinotopy restricted to the occipital cortex and category-selectivity emerging in the lateral-occipital and ventral-temporal cortex. However, recent studies show that category-selective regions exhibit systematic retinotopic biases, for example exhibiting stronger activation for stimuli presented in the contra- compared to the ipsilateral visual field. It is unclear, however, whether responses within category-selective regions are more strongly driven by retinotopic location or by category preference, and if there are systematic differences between category-selective regions in the relative strengths of these preferences. Here, we directly compare contralateral and category preferences by measuring fMRI responses to scene and face stimuli presented in the left or right visual field and computing two bias indices: a contralateral bias (response to the contralateral minus ipsilateral visual field) and a face/scene bias (preferred response to scenes compared to faces, or vice versa). We compare these biases within and between scene- and face-selective regions and across the lateral and ventral surfaces of the visual cortex more broadly. We find an interaction between surface and bias: lateral surface regions show a stronger contralateral than face/scene bias, whilst ventral surface regions show the opposite. These effects are robust across and within subjects, and appear to reflect large-scale, smoothly varying gradients. Together, these findings support distinct functional roles for the lateral and ventral visual cortex in terms of the relative importance of the spatial location of stimuli during visual information processing.

Impairment of emotional expression detection after unilateral medial temporal structure resection

Detecting emotional facial expressions is an initial and indispensable component of face-to-face communication. Neuropsychological studies on the neural substrates of this process have shown that bilateral amygdala lesions impaired the detection of emotional facial expressions. However, the findings were inconsistent, possibly due to the limited number of patients examined. Furthermore, whether this processing is based on emotional or visual factors of facial expressions remains unknown. To investigate this issue, we tested a group of patients (n = 23) with unilateral resection of medial temporal lobe structures, including the amygdala, and compared their performance under resected- and intact-hemisphere stimulation conditions. The participants were asked to detect normal facial expressions of anger and happiness, and artificially created anti-expressions, among a crowd with neutral expressions. Reaction times for the detection of normal expressions versus anti-expressions were shorter when the target faces were presented to the visual field contralateral to the intact hemisphere (i.e., stimulation of the intact hemisphere; e.g., right visual field for patients with right hemispheric resection) compared with the visual field contralateral to the resected hemisphere (i.e., stimulation of the resected hemisphere). Our findings imply that the medial temporal lobe structures, including the amygdala, play an essential role in the detection of emotional facial expressions, according to the emotional significance of the expressions.

Research of the Gaze during Perception of Textbook’s Page Elements in Bulgarian

A study about perception of a page from a textbook of Bulgarian is presented in the article. Participants in the experiment are 30 students of age 15 to 19 from high schools in Sofia. The study is realized through an eye tracking system. For the purposes of the study 8 stimuli (textbook pages) were constructed, containing the components as follows: “text”, “image”, and “diagram”. In each stimulus the quantity of the components differs. All possible pairs in a combination in the left and in the right field of view are presented in the stimuli. The goal of the research is to be examined the fixation of the gaze on each elements of a textbook page. To assess the characteristic of the gaze was calculated the number of saccades in the left and right visual field of the slides. The data are organized in spreadsheets. Statistical analysis is performed in two-group t-test (two samples with different variances). Mean number of saccades, standard deviation, standard error, critical ratio are calculated.

Lateralization of Color Discrimination Performance and Lexical Effects in Patients With Chronic Schizophrenia

Introduction: Patients with schizophrenia experience various visual disturbances. However, information regarding color perception in these patients is rare. In this study, we used a lateralized color search task to investigate whether difference in color name affects color recognition in patients with schizophrenia.Methods: In a color search task, we controlled the position of the target that emerged from the left visual field (LVF) or right visual field (RVF) as well as the color category. In this task, both the target and the distractors had the same or different color name (e.g., blue or green).Results: Patients with schizophrenia showed faster performance in the color search task with different color names for target-distractors when the target emerged from the LVF than when it emerged from the RVF. However, the same laterality was not observed in healthy controls. This finding indicates that semantic processing for color name differences influenced visual discrimination performance in patients with schizophrenia more profoundly in the LVF than in the RVF.Conclusion: This lateralized performance could imply the failure of the left hemisphere language processing dominance in schizophrenia. A search paradigm combining target position and category may indicate that automatic language processing depends on imbalanced hemispheric function in schizophrenia.