Deep Learning Neural Networks as a Model of Saccadic Generation
Top-down guidance of visual search is an issue of continuous discussions (e.g. Wolfe, Horowitz, 2017). However, it’s still unclear when guidance emerges in the course of individual development, and whether the fronto-parietal brain network, which underpins attentional control, is necessary for the attentional guidance. Although there were a number of experiments studying visual search in children, to our knowledge no study directly confronted conditions, under which adults do and do not demonstrate guided search, in younger populations. In our experiment, we compared feature search, guided conjunction search and unguided conjunction search in 20 young adults (university students, mean age 18.5) and 20 junior schoolchildren (7.5–9.5 years old, mean age 8.5). The two groups performed three randomized blocks of the standard visual search task, searching for a target “fox’s house” among distractor houses and receiving feedback after each trial. The target house differed from distractors only in color (feature search), in color and shape (conjunction search), or was defined as a specific combination of two colors (conjunction search with no possibility of top-down guidance). Set sizes of 4, 7, and 10 stimuli were used, with only a half of the trials containing a target. Our hypothesis was that in adults we would observe top-down regulation of the conjunction search, whereas in children the search besides the feature search condition will be equally inefficient, because of the fron-to-parietal network immaturity (e.g. Astle et al., 2015). Surprisingly, the overall pattern of results in all three conditions was the same in children and adults, with pronouncedly more efficient conjunction search as compared to the unguided search, although children were significantly (and proportionally) slower in all types of search. This allows concluding that top-down attentional guidance is already fully present in junior schoolchildren.
MEG evidence for surround suppression effect in human early visual cortex during illusory contour processing
Microsaccadic eye movements belong to the category of micromovements, such as tremor and drift, though their functional purpose is still debated. Spatial cueing paradigms typically require fixational control, but this does not eliminate all oculomotor activity associated with the preparation of saccades in the cued direction. During the antisaccade task, planning and execution are separate processes and we therefore hypothesise that we may notice reduced microsaccade behaviour during the execution of antisaccade tasks as compared to saccade trials. The study is based on an eyetracking experiment involving 22 participants asked to perform saccades and antisaccades in blocked or mixed sets of trials. Each participant contributed to three main blocks: 50 trials in the fixed saccade block, 50 trials in the fixed antisaccade block, and 200 trials in the mixed saccade — antisaccade condition. In the saccade trials, a green fixation cross is displayed at the centre of the screen, whereas during the antisaccade trials the fixation cross is red, allowing participants to prepare the appropriate response (but not direction) prior to the target. The results of the study imply a strong latency cost of antisaccades as compared to prosaccades and an additional cost of mixed blocks, though these two effects did not interact. Crucially, in the blocked antisaccade trials, we predict that a supressed oculomotor system would lead to a lower occurrence of microsaccades initiated by the participants, in particular the trials where observers did not make erroneous prosaccades. We believe this may be due to participants having enough time to prepare the top-down control of the oculomotor system, which leads to a predictable pattern for each participant, where they either suppress microsaccadic movements completely or do not throughout the entire block. We also predict that in the mixed block participants have less time to prepare the top-down microsaccade suppression and we will test this by comparing data between the saccade, the antisaccade and mixed blocks
The distractive effects on attentional task performance in different paradigms are analyzed in this paper. I demonstrate how distractors may negatively affect (interference effect), positively (redundancy effect) or neutrally (null effect). Distractor effects described in literature are classified in accordance with their hypothetical source. The general rule of the theory is also introduced. It contains the formal prediction of the particular distractor effect, based on entropy and redundancy measures from the mathematical theory of communication (Shannon, 1948). Single- vs dual-process frameworks are considered for hypothetical mechanisms which underpin the distractor effects. Distractor profiles (DPs) are also introduced for the formalization and simple visualization of experimental data concerning the distractor effects. Typical shapes of DPs and their interpretations are discussed with examples from three frequently cited experiments. Finally, the paper introduces hierarchical hypothesis that states the level-fashion modulating interrelations between distractor effects of different classes.
This article describes the expierence of studying factors influencing the social well-being of educational migrants as mesured by means of a psychological well-being scale (A. Perrudet-Badoux, G.A. Mendelsohn, J.Chiche, 1988) previously adapted for Russian by M.V. Sokolova. A statistical analysis of the scale's reliability is performed. Trends in dynamics of subjective well-being are indentified on the basis the correlations analysis between the condbtbions of adaptation and its success rate, and potential mechanisms for developing subjective well-being among student migrants living in student hostels are described. Particular attention is paid to commuting as a factor of adaptation.