The role of color in transsaccadic object correspondence

With each saccade, visual information is disrupted, and the visual system is tasked with establishing object correspondence between the presaccadic and postsaccadic representations of the saccade target. There is substantial evidence that the visual system consults spatiotemporal continuity when determining object correspondence across saccades. The evidence for surface feature continuity, however, is mixed. Surface features that are integral to the saccade target object's identity (e.g., shape and contrast polarity) are informative of object continuity, but features that may only imply the state of the object (e.g., orientation) are ignored. The present study tested whether color information is consulted to determine transsaccadic object continuity. We used two variations of the intrasaccadic target displacement task. In Experiments 1 and 2, participants reported the direction of the target displacement. In Experiments 3 and 4, they instead reported whether they detected any target movement. In all experiments, we manipulated the saccade target's continuity by removing it briefly (i.e., blanking) and by changing its color. We found that large color changes can disrupt stability and increase sensitivity to displacements for both direction and movement reports, although not as strongly as long blank durations (250 ms). Interestingly, even smaller color changes, but not blanking, reduced response biases. These results indicate that disrupting surface feature continuity may impact the process of transsaccadic object correspondence more strongly than spatiotemporal disruptions by both increasing the sensitivity and decreasing the response bias.

A Multi-Method Approach to Addressing the Toddler Data Desert in Attention Research

Visual attention skills undergo robust development change during infancy and continue to co-develop with other cognitive processes in early childhood. Despite this, this is a general disconnect between measures of the earliest foundations of attention during infancy and later development of attention in relation to executive functioning during the toddler years. To examine associations between these different measures of attention, the current study administered an oculomotor task (infant orienting with attention, IOWA) and a manual response (Flanker) task with a group of toddlers. We collected simultaneous neural recordings (using functional near-infrared spectroscopy), eye-tracking, and behavioral responses in 2.5- and 3.5-year-olds to examine the neural and behavioral associations between these skills. Results revealed that oculomotor facilitation in the IOWA task was negatively associated with accuracy on neutral trials in the Flanker task. Second, conflict scores between the two tasks were positively associated. At the neural level, however, the tasks showed distinct patterns of activation. Left frontal cortex was engaged during the Flanker task whereas right frontal and parietal cortex was engaged during the IOWA task. Activation during the IOWA task differed based on how well children could control oculomotor behavior during the task. Children with high levels of stimulus reactivity activated parietal cortex more strongly, but children with more controlled oculomotor behavior activated frontal cortex more strongly.

Tracking flanker task dynamics: Evidence for continuous attentional selectivity

Understanding the dynamics of selective attention has been a central research goal in the cognitive sciences. One account proposes that attention is unitary and increases in selectivity continuously over time. An alternative account proposes that attention switches from a low to a high state of selectivity at a discrete point in time when a distinct selective attention mechanism is engaged. Despite posing fundamentally different theoretical perspectives on selective attention, both accounts have successfully explained outcome-based data, such as reaction time. Here, we used mouse-tracking, which provides high temporal resolution to record movement trajectories in a flanker task. We examined spatial and temporal movement dynamics for characteristics of continuous and discrete shifts in attentional selectivity. Our results showed that attentional selectivity increases gradually over time, rather than abruptly, demonstrating a continuous process of selective attention. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Object-mediated overwriting across saccades

How are visual sensory representations that are acquired peripherally from a saccade target related to sensory representations generated foveally after the saccade? We tested the hypothesis that, when the two representations are perceived to belong to the same object, the post-saccadic value tends to overwrite the pre-saccadic value. Participants executed a saccade to a colored target object, which sometimes changed during the saccade by ±15°, 30°, or 45° in color space. They were post-cued to report either the pre-saccadic or post-saccadic color in a continuous report procedure. Substantial overwriting of the pre-saccadic color by the post-saccadic color was observed. Moreover, the introduction of a brief post-saccadic blank interval (which disrupted the perception of object correspondence) led to a substantial reduction in overwriting. The results provide the first direct evidence for an object-mediated overwriting mechanism across saccades, in which post-saccadic values automatically replace pre-saccadic values.

Age-related decline in visual working memory: The effect of nontarget objects during a delayed estimation task

Visual working memory (VWM) is an essential aspect of cognitive functioning that becomes compromised in older adults. A canonical probe of VWM is the change detection task in which participants compare a visually presented stimulus with items being maintained in VWM. Older adults show a decreased ability to detect changes between a stimulus and the contents of VWM compared with younger adults. Previously, we used a dynamic neural field (DNF) model to explore changes in neural connectivity that can explain this pattern of decline in performance. These simulations suggest that older adults have cortical interactions that are more diffuse compared to younger adults. In the current article, we examined the precision of representations in VWM using the delayed-estimation task. Participants are first presented with a memory array. After a delay, a location is cued, and participants click on a color wheel to indicate which color was at that location. The model predicted that older adults should show increased guessing rates and decreased precision (defined as the variability of color responses around the target location) relative to younger adults. The model also predicted that presenting the nontarget items during test should improve the precision of responses for older adults but not for younger adults. Results from two experiments supported these predictions of the model. These findings further advance an emerging theory of the neurocognitive decline of VWM and illustrate how older adults' VWM representations are influenced by the context in which information is being recalled. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

The relationship between visual attention and visual working memory encoding: A dissociation between covert and overt orienting

There is substantial debate over whether visual working memory (VWM) and visual attention constitute a single system for the selection of task-relevant perceptual information or whether they are distinct systems that can be dissociated when their representational demands diverge. In the present study, we focused on the relationship between visual attention and the encoding of objects into VWM. Participants performed a color change-detection task. During the retention interval, a secondary object, irrelevant to the memory task, was presented. Participants were instructed either to execute an overt shift of gaze to this object (Experiments 1-3) or to attend it covertly (Experiments 4 and 5). Our goal was to determine whether these overt and covert shifts of attention disrupted the information held in VWM. We hypothesized that saccades, which typically introduce a memorial demand to bridge perceptual disruption, would lead to automatic encoding of the secondary object. However, purely covert shifts of attention, which introduce no such demand, would not result in automatic memory encoding. The results supported these predictions. Saccades to the secondary object produced substantial interference with VWM performance, but covert shifts of attention to this object produced no interference with VWM performance. These results challenge prevailing theories that consider attention and VWM to reflect a common mechanism. In addition, they indicate that the relationship between attention and VWM is dependent on the memorial demands of the orienting behavior. (PsycINFO Database Record

An object-mediated updating account of insensitivity to transsaccadic change

Recent evidence has suggested that relatively precise information about the location and visual form of a saccade target object is retained across a saccade. However, this information appears to be available for report only when the target is removed briefly, so that the display is blank when the eyes land. We hypothesized that the availability of precise target information is dependent on whether a post-saccade object is mapped to the same object representation established for the presaccade target. If so, then the post-saccade features of the target overwrite the presaccade features, a process of object mediated updating in which visual masking is governed by object continuity. In two experiments, participants' sensitivity to the spatial displacement of a saccade target was improved when that object changed surface feature properties across the saccade, consistent with the prediction of the object-mediating updating account. Transsaccadic perception appears to depend on a mechanism of object-based masking that is observed across multiple domains of vision. In addition, the results demonstrate that surface-feature continuity contributes to visual stability across saccades.

The Role of Surface Feature Continuity in Object-based Inhibition of Return

The contribution of surface feature continuity to object-based inhibition of return (IOR) was tested in three experiments. Participants executed a saccade to a previously fixated or unfixated colored disk after the object had moved to a new location. Object-based IOR was observed as lengthened saccade latency to a previously fixated object. The consistency of surface feature (color) and spatiotemporal information was manipulated to examine the feature used to define the persisting objects to which inhibition is assigned. If the two objects traded colors during motion, object-based IOR was reliably reduced (Experiment 2), suggesting a role for surface feature properties in defining the objects of object-based IOR. However, if the two objects changed to new colors during motion, object-based IOR was preserved (Experiment 1), and color consistency was not sufficient to support object continuity across a salient spatiotemporal discontinuity (Experiment 3). These results suggest that surface feature consistency plays a significant role in defining object persistence for the purpose of IOR, although surface features may be weighted less strongly than spatiotemporal features in this domain.

Preparation of porous apatite granules from calcium phosphate cement

A versatile method for preparing spherical, micro- and macroporous (micro: 2-10 and macro: 150-550 microm pores), carbonated apatitic calcium phosphate (Ap-CaP) granules (2-4 mm in size) was developed by using NaCl crystals as the porogen. The entire granule production was performed between 21 and 37 degrees C. A CaP cement powder, comprising alpha-Ca3(PO4)2 (61 wt.%), CaHPO4 (26%), CaCO3 (10%) and precipitated hydroxyapatite, Ca10(PO4)6(OH)2 (3%), was dry mixed with NaCl crystals varying in size from 420 microm to 1 mm. Cement powder (35 wt.%) and NaCl (65 wt.%) mixture was kneaded with an ethanol-Na2HPO4 initiator solution, and the formed dough was immediately agitated on an automatic sieve shaker for a few minutes to produce the spherical granules. Embedded NaCl crystals were then leached out of the granules by soaking them in deionized water. CaP granules were micro- and macroporous with a total porosity of 50% or more. Granules were composed of carbonated, poorly crystallized, apatitic CaP phase. These were the first spherical and porous CaP granules ever produced from a self-setting calcium phosphate cement. The granules reached their final handling strength at the ambient temperature through the cement setting reaction, without having a need for sintering.

Formation of apatitic calcium phosphates in a Na-K-phosphate solution of pH 7.4

Poorly crystalline, apatitic calcium phosphate powders have been synthesized by slowly adding a Na- and K-containing reference phosphate solution with a pH value of 7.4 to an aqueous calcium nitrate solution at 37 degrees C. Nano-particulated apatitic powders obtained were shown to contain small amounts of Na and K, which render them more similar in chemical composition to that of the bone mineral. Precipitated and dried powders were found to exhibit self-hardening cement properties when kneaded in a mortar with a sodium citrate- and sodium phosphate-containing starter solution. The same phosphate solution used in powder synthesis was found to be able to partially convert natural, white and translucent marble pieces of calcite (CaCO3) into calcium-deficient hydroxyapatite upon aging the samples in that solution for 3 days at 60 degrees C. Sample characterization was performed by using scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, inductively-coupled plasma atomic emission spectroscopy, and simultaneous thermogravimetry and differential thermal analysis.

Synthesis of biomimetic Ca-hydroxyapatite powders at 37 degrees C in synthetic body fluids

An important inorganic phase for synthetic bone applications, calcium hydroxyapatite (HA, Ca10(PO4)6(OH)2), was prepared as a nano-sized (approximately 50 nm), homogeneous and high-purity ceramic powder from calcium nitrate tetrahydrate and diammonium hydrogen phosphate salts dissolved in modified synthetic body fluid (SBF) solutions at 37 degrees C and pH of 7.4 using a novel chemical precipitation technique. The synthesized precursors were found to easily reach a phase purity >99% after 6 h of calcination in air atmosphere at 90 degrees C, following oven drying at 80 degrees C. There was observed, surprisingly, no decomposition of HA into the undesired beta-TCP phase even after heating at 1,600 degrees C in air for 6 h. This observation showed the superior high-temperature stability of such 'biomimetic' HA powders as compared to those reported in previous studies. The former powders were also found to contain trace amounts of Na and Mg ions, originating from the use of SBF solutions instead of pure water during their synthesis. Characterization and chemical analysis of the synthesized powders were performed by X-ray powder diffraction, energy-dispersive X-ray spectroscopy, Fourier-transform infra-red spectroscopy, scanning electron microscopy, and inductively coupled plasma atomic emission spectroscopy.

Characterization of virus infected cell cultures by pyrolysis/direct chemical ionization mass spectrometry

The supernatants of Vero cell cultures after infection with a herpes simplex virus or a poliomyelitis virus as well as a blank were analysed by pyrolysis/direct chemical ionization mass spectrometry (Py/DCI MS). Informative pyrogrammes were obtained and used for characterization of viral proteins by applying pattern recognition methods. Differentiation of viral proteins was evaluated by analysing 'blind' samples. Herpes viruses could be classified correctly but the observed differences between the blank and the polio virus supernatants were too small for reliable classification of the polio viruses. Purification of the samples seems to be a prerequisite for further studies. The potential value of Py/DCI MS as a rapid non-invasive diagnostic method for viral meningoencephalitis is stressed.

Direct chemical ionization-mass spectrometric profiling of urine in premenstrual syndrome

In search of the pathophysiological background of premenstrual syndrome, direct chemical ionization-mass spectrometric profiling was applied to urine samples from 17 patients and 18 control subjects, collected on days 11 and 25 of the menstrual cycle. Oestrogenic compounds and hippuric acid were found to be involved in differences between these groups. Quotient profiles calculated for each subject from their profiles of days 11 and 25 showed cycle day-dependent group differences. Masses accounting for these differences between patients and control subjects indicate the involvement of unsaturated heterocyclic compounds in premenstrual syndrome.

Direct chemical ionization-pattern recognition: characterization of bacteria and body fluid profiling

Direct chemical ionization is ideally suited for profiling purposes because it is a relatively soft ionization method, easy to operate, reproducible and with a high sample throughput. Moreover, for non-volatile matrices the method combines pyrolysis with an optimal pyrolysate transfer to the ionization region enabling the detection of high molecular weight compounds. Application of the technique to urine analysis of women with a premenstrual syndrome and characterization of Salmonella bacteria illustrates its usefulness. Optimal information extraction from the profiles is, because of their complex nature, only possible using pattern recognition techniques. A new approach based on the data analysis of trend spectra is discussed.

LC/MS determination of bromazepam, clopenthixol, and reserpine in serum of a non-fatal case of intoxication

Combined liquid chromatography and mass spectrometry (LC/MS) with a moving belt interface can be used as a rapid method for the determination of bromazepam, clopenthixol, and reserpine in serum samples obtained from cases of acute overdoses with combinations of these drugs. Low resolution detection limits are about 100 pg for the three drugs, while in high resolution mode the detection limit for bromazepam is shown to be at least 35 pg. Accurate masses were obtained in a serum sample within 5 ppm using high voltage scanning over a narrow mass range for about 10 ng of bromazepam and clopenthixol, respectively. Chemical deactivation of the belt was shown to effectively reduce memory effects and to improve the desorption characteristics of the belt leading to higher yields of evaporated intact molecules.

Derivatization and mass spectrometric behaviour of catecholamines and their 3-O-methylated metabolites

A method has been developed for the derivatization of both catecholamines (dopamine, noradrenaline and adrenaline) and their 3-O-methylated metabolites (3-methoxytyramine, normetanephrine and metanephrine) in a single run. The compounds were first incubated with methanolic hydrochloric acid to methylate those compounds that contain a benzylic hydroxyl group and were subsequently converted into their pentafluoropropionyl derivatives. The derivatives thus prepared, showed good gas chromatographic and electron-impact mass spectrometric properties and can be analysed in a single gas chromatographic run. The effect of the derivatization on exchange reactions in the aromatic ring was investigated because standard compounds with deuterium label in that part of the molecule are often used in isotope dilution measurements. The exchange of deuterium for hydrogen in the aromatic ring under derivatization conditions was found to be limited.

The early recognition of the 21-hydroxylase deficiency variety of congenital adrenal hyperplasia

The urinary steroids excreted by three newborn infants with 21-hydroxylase deficiency and by 15 healthy newborns aged two days have been compared after analysis by gas liquid chromatography (GLC). The identity of each steroid was carefully checked by gas chromatography/mass spectroscopy (GC-MS). The enzyme deficiency leads to the elevated excretion of urinary precursor metabolites, mainly 3alpha,17alpha,20alpha-trihydroxy-5beta-pregnan, 3alpha,17alpha,20alpha-trihydroxy-5beta-pregnan-11-one and 3alpha,17alpha-dihydroxy-5beta-pregnan-20-one. In the search for a quick and firm confirmation of suspected 21-hydroxylase deficiency in a newborn baby by means of a GLC-profile of urinary steroids, most attention has up to now been paid to 3alpha,17alpha,20alpha-trihydroxy-5beta-pregnan. However, 3alpha,17alpha-dihydroxy-5beta-pregnan-20-one is a better indicator, as it enables one to confirm the existence of this disease soon after birth directly from the GLC-profile without further analyses by GC-MS.

Formation of odorous compounds from hydrogen sulphide and 2-butenal

Strongly odorous compounds may be formed upon addition of hydrogen sulphide to unsaturated carbonyl compounds. The reaction between hydrogen sulphide and 2-butenal was studied, and the characteristics of the flavour, the structure and some of the physical chemical characteristics of the reaction products were determined. The influence of the pH on the type of components formed in dilute aqueous solution was investigated.

Reaction of hydrogen sulphide with 2-alkenals

Depending on the types of solvent and catalyst, different products are formed in the reaction of hydrogen sulphide with 2-alkenals. The structures of many of these products have been elucidated, and the reaction sequences leading to them are proposed.