Object-based grouping benefits without integrated feature representations in visual working memory

Visual working memory (VWM) is typically considered to represent complete objects—that is, separate parts of an object are maintained as bound objects. Yet it remains unclear whether and how the features of disparate parts are integrated into a whole-object memory representation. Using a change detection paradigm, the present study investigated whether VWM performance varies as a function of grouping strength for features that either determine the grouped object (orientation) or that are not directly grouping relevant (color). Our results showed a large grouping benefit for grouping-relevant orientation features and, additionally, a much smaller, albeit reliable, benefit for grouping-irrelevant color features when both were potentially task relevant. By contrast, when color was the only task-relevant feature, no grouping benefit from the orientation feature was revealed both under lower or relatively high demands for precision. Together, these results indicate that different features of an object are stored independently in VWM; and an emerging, higher-order grouping structure does not automatically lead to an integrated representation of all available features of an object. Instead, an object benefit depends on the specific task demands, which may generate a linked, task-dependent representation of independent features.

Preparatory Template Activation during Search for Alternating Targets

Visual search is guided by representations of target-defining features (attentional templates). We tracked the time course of template activation processes during the preparation for search in a task where the identity of color-defined search targets switched across successive trials (ABAB). Task-irrelevant color probes that matched either the upcoming relevant target color or the previous now-irrelevant target color were presented every 200 msec during the interval between search displays. N2pc components (markers of attentional capture) were measured for both types of probes at each time point. A reliable probe N2pc indicates that the corresponding color template is active at the time when the probe appears. N2pcs of equal size emerged from 1000 msec before search display onset for both relevant-color and irrelevant-color probes, demonstrating that both color templates were activated concurrently. Evidence for color-selective attentional control was found only immediately before the arrival of the search display, where N2pcs were larger for relevant-color probes. These results reveal important limitations in the executive control of search preparation in tasks where two targets alternate across trials. Although the identity of the upcoming target is fully predictable, both task-relevant and task-irrelevant target templates are coactivated. Knowledge about target identity selectively biases these template activation processes in a temporally discrete fashion, guided by temporal expectations about when the target template will become relevant.

Color Intensity of Architectural Concrete Depending on the Type of Cement

In this paper, the influence of the cement type on the final coloring of the concrete with colored powdered inorganic pigments used currently with increasing tendency in construction and modern architecture is presented. In the experimental testing, the difference in intensity/saturation of the color of the concrete containing white cement (CEM I 52.5 R - SR 5 white), which is preferred when using color pigments, and gray (conventional) Portland cement (CEM I 52.5 R) from the same manufacturer has been measured and compared. Three colored inorganic powder pigments (red, green and yellow pigment) containing iron oxides (Fe2O3) have been used to color the concrete mixture. Objectivity of measurement, comparison, and subsequent analysis of individual resulting shades has been ensured by measuring exact RGB values at several places of the concrete cured surface by means of the Colorimeter Colorcatch nanodevice which automatically eliminates all irrelevant color shades, shadows, and impurities. This eliminated the subjective color impression which is usually always biased by external circumstances. Comparison of the color intensity of six experimental samples, including three pigment colors and two types of cement (white/grey), is conclusively related to the color efficiency ratio, the resulting costs, and the ecological footprint arising from the production of the cements above.

Study of interhemispheric interaction by the indices of event-related potentials

The study used a combined Stroop test involving a spatial feature. Stimuli (the words "green", "red", "blue" and "yellow", written in relevant or irrelevant color) were presented to the right or left of the center of the screen. In the case of coincidence of the color of the word and its semantic meaning, it was necessary to press the button with the ipsilateral hand (answer "yes", congruent stimulus), discrepancies – with the contralateral hand (answer "no", incongruent stimulus). According to the results obtained earlier, it was suggested that it is easier to transfer information from the left hemisphere to the right than in the opposite direction, and the dominance of the left hemisphere when performing this type of cognitive task. To study this hypothesis, records of event-related potentials (ERP) were obtained when subjects performed this test. The subjects were 7 men, right-handed, aged 20 ± 1,13 years. The most informative was the registration from Cz, for which the components N450 and late positive complex (LPC) were obtained when stimulated by incongruent stimuli from the right side. The N450 component is associated with anterior cingulate cortex activity and is considered a reliable marker of conflict present in the experimental paradigm of this test. LPC is probably a component specific to the Stroop task and corresponds to the level of conflict of stimuli. Recording ERPs from the central lead does not allow to determine in this case the source of their origin. However, a comparison of ERP of incongruent stimuli from the right and left indicates differences in response to stimuli from different halves of the screen. The appearance of these components for incongruent stimuli exposed on the right side of the screen probably means their association with the functions of the left hemisphere, and confirms the previous hypothesis of metacontrol by the left hemisphere in this type of cognitive task.

Enhancement and Suppression Flexibly Guide Attention

Previous research suggests that observers can suppress salient-but-irrelevant stimuli in a top-down manner. However, one question left unresolved is whether such suppression is, in fact, solely due to distractor-feature suppression or whether it instead also reflects some degree of target-feature enhancement. The present study ( N = 60) addressed this issue. On search trials (70% of trials), participants searched for a shape target when an irrelevant color singleton was either present or absent; performance was better when a color singleton was present. On interleaved probe trials (30% of trials), participants searched for a letter target. Responses were faster for the letter on a target-colored item than on a neutral-colored item, whereas responses were slower for the letter on a distractor-colored item than on a neutral-colored item. The results demonstrate that target-feature enhancement and distractor-feature suppression contribute to attentional guidance independently; enhancement and suppression flexibly guide attention as the occasion demands.

Task-Irrelevant Features in Visual Working Memory Influence Covert Attention: Evidence from a Partial Report Task

Selecting a target based on a representation in visual working memory (VWM) affords biasing covert attention towards objects with memory-matching features. Recently, we showed that even task-irrelevant features of a VWM template bias attention. Specifically, when participants had to saccade to a cued shape, distractors sharing the cue’s search-irrelevant color captured the eyes. While a saccade always aims at one target location, multiple locations can be attended covertly. Here, we investigated whether covert attention is captured similarly as the eyes. In our partial report task, each trial started with a shape-defined search cue, followed by a fixation cross. Next, two colored shapes, each including a letter, appeared left and right from fixation, followed by masks. The letter inside that shape matching the preceding cue had to be reported. In Experiment 1, either target, distractor, both, or no object matched the cue’s irrelevant color. Target-letter reports were most frequent in target-match trials and least frequent in distractor-match trials. Irrelevant cue and target color never matched in Experiment 2. Still, participants reported the distractor more often to the target’s disadvantage, when cue and distractor color matched. Thus, irrelevant features of a VWM template can influence covert attention in an involuntarily object-based manner when searching for trial-wise varying targets.

Dissociating Reward- and Attention-driven Biasing of Global Feature-based Selection in Human Visual Cortex

Objects that promise rewards are prioritized for visual selection. The way this prioritization shapes sensory processing in visual cortex, however, is debated. It has been suggested that rewards motivate stronger attentional focusing, resulting in a modulation of sensory selection in early visual cortex. An open question is whether those reward-driven modulations would be independent of similar modulations indexing the selection of attended features that are not associated with reward. Here, we use magnetoencephalography in human observers to investigate whether the modulations indexing global color-based selection in visual cortex are separable for target- and (monetary) reward-defining colors. To assess the underlying global color-based activity modulation, we compare the event-related magnetic field response elicited by a color probe in the unattended hemifield drawn either in the target color, the reward color, both colors, or a neutral task-irrelevant color. To test whether target and reward relevance trigger separable modulations, we manipulate attention demands on target selection while keeping reward-defining experimental parameters constant. Replicating previous observations, we find that reward and target relevance produce almost indistinguishable gain modulations in ventral extratriate cortex contralateral to the unattended color probe. Importantly, increasing attention demands on target discrimination increases the response to the target-defining color, whereas the response to the rewarded color remains largely unchanged. These observations indicate that, although task relevance and reward influence the very same feature-selective area in extrastriate visual cortex, the associated modulations are largely independent.

Relation of success in study of foreign language with speed of interhemispheric transfer of information

Bilingual speakers seem to outreach monolingual speakers in performing non-verbal tasks for testing executive functions, such as Simon, Flanker and Stroop tasks, as well as in capacity of working memory. Other researchers have doubts about these cognitive benefits of bilinguals and multilinguals. The study used a combined test with the tasks of the Stroop, Poffenberger, Sperry in native (Ukrainian) and foreign (English) languages. Schoolboys of lyceum were the subjects surveyed (14-15 years old). Stimuli (the word "Green" or "Red", "Blue" or "Yellow" written in relevant or irrelevant color) were exposed on the right or left from the center of the screen. In the case of congruence the word and its semantic meaning should press one button by the ipsilateral hand ("yes"), while in the case of mismatch – the other button by the contralateral one ("no"). Latent periods of response to stimuli, which reflect the speed of the interhemispheric transfer of information, were taken into account. Correlation analysis of the success in study in the nine subjects of the three blocks (humanities, natural and formal disciplines) reveal a direct correlation of speed of reaction when performing the complex Stroop test in both the native and English languages with the success in the learning English language, what may indicate on special dependence of the success from interhemispheric interaction. In order for the foreign language to be automated and become "all the more native", it is need the fast access of the executive structures of the brain, such as the front-parietal neural network, to the linguistic neural networks, presented in both hemispheres. According to literature, the inhibitory control mechanism from the dorsolateral prefrontal cortex as the key structure of the front-parietal brain system may be one of several mechanisms underlying bilingual superiority. The results obtained by us complement this conception, indicating the importance of the speed of interhemispheric interaction.