382 research outputs found
Altered processing of food stimuli in adolescents with loss of control eating
Loss of control eating (LOC) constitutes a common eating pathology in childhood and adolescence. Models developed for adult patients stress a biased processing of food-related stimuli as an important maintaining factor. To our knowledge, however, no EEG study to date investigated the processing of visual food stimuli in children or adolescents with LOC. Adolescents with at least one self-reported episode of LOC in the last four weeks and a matched control group completed a modified Go/NoGo task, with a numerical target or non-target stimulus being presented on one side of the screen and an irrelevant high-calorie food or neutral stimulus being presented on the opposite side. Mean P3 amplitudes were analyzed. In Go trials, the LOC group’s mean P3 amplitudes were comparable irrespective of distractor category, while for NoGo trials, mean P3 amplitudes were significantly higher when the distractor was a high-calorie food stimulus. This pattern was reversed in the control group. Results are interpreted in light of Gray’s reinforcement sensitivity theory. They might reflect altered processes of behavioral inhibition in adolescents with LOC upon confrontation with visual food stimuli
Electrophysiological activation by masked primes: Independence of prime-related and target-related activities
Visual stimuli that are made invisible by metacontrast masking (primes) have a
marked influence on behavioral and psychophysiological measures such as reaction
time (RT) and the lateralized readiness potential (LRP). 4 experiments are
reported that shed light on the effects that masked primes have on the LRP.
Participants had a go-nogo task in which the prime was associated with 1 of 2
responses even if the target required participants to refrain from responding.
To analyze the electrophysiological responses, we computed the LRP and applied
an averaging method separating the activation due to the prime and the target.
The results demonstrated that (a) masked primes activate responses even in a
nogo situation, (b) this prime-related activation is independent of masking, (c)
and is also independent of whether prime and target require the same responses
(congruent condition) or different responses (incongruent condition)
Top-down contingent feature-specific orienting with and without awareness of the visual input
In the present article, the role of endogenous feature-specific orienting for
conscious and unconscious vision is reviewed. We start with an overview of
orienting. We proceed with a review of masking research, and the definition of
the criteria of experimental protocols that demonstrate endogenous and exogenous
orienting, respectively. Against this background of criteria, we assess studies
of unconscious orienting and come to the conclusion that so far studies of
unconscious orienting demonstrated endogenous feature-specific orienting. The
review closes with a discussion of the role of unconscious orienting in action
control
Follow the sign! Top-down contingent attentional capture of masked arrow cues
Arrow cues and other overlearned spatial symbols automatically orient attention
according to their spatial meaning. This renders them similar to exogenous cues
that occur at stimulus location. Exogenous cues trigger shifts of attention even
when they are presented subliminally. Here, we investigate to what extent the
mechanisms underlying the orienting of attention by exogenous cues and by arrow
cues are comparable by analyzing the effects of visible and masked arrow cues on
attention. In Experiment 1, we presented arrow cues with overall 50% validity.
Visible cues, but not masked cues, lead to shifts of attention. In Experiment 2,
the arrow cues had an overall validity of 80%. Now both visible and masked
arrows lead to shifts of attention. This is in line with findings that
subliminal exogenous cues capture attention only in a top-down contingent
manner, that is, when the cues fit the observer’s intentions
The costs of switching attentional sets
People prioritize those aspects of the visual environment that match their attentional set. In the present study, we investigated whether switching from one attentional set to another is associated with a cost. We asked observers to sequentially saccade toward two color-defined targets, one on the left side of the display, the other on the right, each among a set of heterogeneously colored distractors. The targets were of the same color (no attentional set switch required) or of different colors (switch of attentional sets necessary), with each color consistently tied to a side, to allow observers to maximally prepare for the switch. We found that saccades were less accurate and slower in the switch condition than in the no-switch condition. Furthermore, whenever one of the distractors had the color associated with the other attentional set, a substantial proportion of saccades did not end on the target, but on this distractor. A time course analysis revealed that this distractor preference turned into a target preference after about 250–300 ms, suggesting that this is the time required to switch attentional sets
Neuro-cognitive mechanisms of conscious and unconscious visual perception: From a plethora of phenomena to general principles
Psychological and neuroscience approaches have promoted much progress in
elucidating the cognitive and neural mechanisms that underlie phenomenal visual
awareness during the last decades. In this article, we provide an overview of
the latest research investigating important phenomena in conscious and
unconscious vision. We identify general principles to characterize conscious and
unconscious visual perception, which may serve as important building blocks for
a unified model to explain the plethora of findings. We argue that in particular
the integration of principles from both conscious and unconscious vision is
advantageous and provides critical constraints for developing adequate
theoretical models. Based on the principles identified in our review, we outline
essential components of a unified model of conscious and unconscious visual
perception. We propose that awareness refers to consolidated
visual representations, which are accessible to the entire brain and therefore
globally available. However, visual awareness not only depends
on consolidation within the visual system, but is additionally the result of a
post-sensory gating process, which is mediated by higher-level cognitive control
mechanisms. We further propose that amplification of visual representations by
attentional sensitization is not exclusive to the domain of conscious
perception, but also applies to visual stimuli, which remain unconscious.
Conscious and unconscious processing modes are highly interdependent with
influences in both directions. We therefore argue that exactly this
interdependence renders a unified model of conscious and unconscious visual
perception valuable. Computational modeling jointly with focused experimental
research could lead to a better understanding of the plethora of empirical
phenomena in consciousness research
Dipeptidyl peptidase IV of human lymphocytes. Evidence for specific hydrolysis of glycylproline p-nitroanilide in T-lymphocytes
The power of the feed-forward sweep
Vision is fast and efficient. A novel natural scene can be categorized (e.g. does
it contain an animal, a vehicle?) by human observers in less than 150 ms, and
with minimal attentional resources. This ability still holds under strong
backward masking conditions. In fact, with a stimulus onset asynchrony of about
30 ms (the time between the scene and mask onset), the first 30 ms of selective
behavioral responses are essentially unaffected by the presence of the mask,
suggesting that this type of “ultra-rapid” processing can rely on a sequence of
swift feed-forward stages, in which the mask information never “catches up” with
the scene information. Simulations show that the feed-forward propagation of the
first wave of spikes generated at stimulus onset may indeed suffice for crude
re-cognition or categorization. Scene awareness, however, may take significantly
more time to develop, and probably requires feed-back processes. The main
implication of these results for theories of masking is that pattern or
metacontrast (backward) masking do not appear to bar the progression of visual
information at a low level. These ideas bear interesting similarities to
existing conceptualizations of priming and masking, such as Direct Parameter
Specification or the Rapid Chase theory
An antibody against secretogranin I (chromogranin B) is packaged into secretory granules.
Preoperative biliary drainage by plastic or self-expandable metal stents in patients with periampullary tumors: results of a randomized clinical study
Background and study aims Preoperative biliary drainage in patients with periampullary tumors and jaundice has been popularized to improve the quality of life and minimize the risks associated with subsequent radical surgery. The aim of this study was to investigate the possible superiority of self-expandable metal stents (SEMS) over plastic stents, by comparing the amount of bacteria in intraoperatively collected bile and using this variable as a proxy for the efficacy of the respective biliary drainage modalities. Patients and methods In this randomized clinical trial, 92 patients with obstructive jaundice were enrolled; 45 were allocated to the plastic stent group and 47 to the SEMS group. The primary outcome was the extent and magnitude of biliary bacterial growth at the time of surgical exploration. Secondary outcomes were: macroscopic grading of inflammation of the stented bile ducts, occurrence of adverse events after stenting, stent dysfunction, recognized surgical complexities, and incidence of postoperative complications. Results The patients were well matched regarding clinical and disease-specific characteristics. At surgery, there were no group differences in the bacterial amount and composition of the bile cultures or the perceived difficulty of surgical dissection. During the preoperative biliary drainage period, more instances of stent dysfunction requiring stent replacement were recorded in the plastic stent group (19 % vs. 0 %; P = 0.03). Postoperative complications in patients who underwent curative surgery were more common in patients with plastic stents (72 % vs. 52 %), among which clinically significant leakage from the pancreatic anastomoses seemed to predominate (12 % vs. 3.7 %); however, none of these differences in postoperative adverse events reached statistical significance. Conclusion This randomized clinical study was unable to demonstrate any superiority of SEMS in the efficacy of preoperative bile drainage, as assessed by the amount of bacteria in the intraoperatively collected bile. However, some data in favor of SEMS were observed among the clinical secondary outcomes variables (preoperative stent exchange rates) without increases in local inflammatory reactions
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