Changes in processing of masked stimuli across early- and late-night sleep: a study on behavior and brain potentials

Sleep has proven to support the memory consolidation in many tasks including learning of perceptual skills. Explicit, conscious types of memory have been demonstrated to benefit particularly from slow-wave sleep (SWS), implicit, non-conscious types particularly from rapid eye movement (REM) sleep. By comparing the effects of early-night sleep, rich in SWS, and late-night sleep, rich in REM sleep, we aimed to separate the contribution of these two sleep stages in a metacontrast masking paradigm in which explicit and implicit aspects in perceptual learning could be assessed separately by stimulus identification and priming, respectively. We assumed that early sleep intervening between two sessions of task performance would specifically support stimulus identification, while late sleep would specifically support priming. Apart from overt behavior, event-related EEG potentials (ERPs) were measured to record the cortical mechanisms associated with behavioral changes across sleep. In contrast to our hypothesis, late-night sleep appeared to be more important for changes of behavior, both for stimulus identification, which tended to improve across late-night sleep, and for priming, with the increase of errors induced by masked stimuli correlating with the duration of REM sleep. ERP components proved sensitive to presence of target shapes in the masked stimuli and to their priming effects. Of these components, the N2 component, indicating processing of conflict, became larger across early-night sleep and was related to the duration of S4 sleep, the deepest substage of SWS containing particularly high portions of EEG slow waves. These findings suggest that sleep promotes perceptual learning primarily by its REM sleep portion, but indirectly also by way of improved action monitoring supported by deep slow-wave sleep.     

Prior knowledge enhances the category dimensionality effect

A study of the combined influence of prior knowledge and stimulus dimensionality on category learning was conducted. Subjects learned category structures with the same number of necessary dimensions but with more or fewer additional, redundant dimensions and with either knowledge-related or knowledge-unrelated features. Minimal-learning models predict that all subjects, regardless of condition, either should learn the same number of dimensions or should respond more slowly to each dimension. Despite similar learning rates and response times, subjects learned more features in the high-dimensional than in the low-dimensional condition. Furthermore, prior knowledge interacted with dimensionality, increasing what was learned, especially in the high-dimensional case. A second experiment confirmed that the participants did, in fact, learn more features during the training phase, rather than simply inferring them at test. These effects can be explained by direct associations among features (representing prior knowledge), combined with feedback between features and the category label, as was shown by simulations of the knowledge resonance, or KRES, model of category learning.     

Vision for perception and vision for action: normal and unusual development

Evidence suggests that visual processing is divided into the dorsal ('how') and ventral ('what') streams. We examined the normal development of these streams and their breakdown under neurological deficit by comparing performance of normally developing children and Williams syndrome individuals on two tasks: a visually guided action ('how') task, in which participants posted a card into an oriented slot, and a perception ('what') task, in which they matched a card to the slot's orientation. Results showed that all groups performed worse on the action task than the perception task, but the disparity was more pronounced in WS individuals and in normal 3-4-year-olds than in older children. These findings suggest that the 'how' system may be relatively slow to develop and more vulnerable to breakdown than the 'what' system.     

Attractiveness of blonde women in evolutionary perspective: studies with two Polish samples

An experimental study was undertaken to assess the phenomenon of male preference for blondes. In the first study, 360 Polish men ages 18 to 46 years were asked to assess the attractiveness of the presented stimuli using a 9-point scale. Stimuli were 9 different pictures of the same women whose ages (about 20, 30, and 40 years old) and hair colors (blonde, brown, and brunette) were manipulated. Pictures of blonde-haired women were generally rated as younger than the others. The attractiveness ratings of female faces changed with age and hair color. Still, only the 30-yr.-old woman with blonde hair was rated as significantly more attractive than those with brown or brunette hair. In a second study (the analysis of 500 Internet advertisements) mature women dyed their hair blonde more frequently. These results are analyzed with regard to the evolutionarily formed male preference for younger females.     

The effects of revisionism on remembered emotion: the valence of older,voluntary immigrants' pre‐migration autobiographical memories

Prior research on remembered emotion demonstrates effects of revisionism in memory. The positivity bias describes preferential recall for positive emotions and the fading affect bias describes greater fading of negative versus positive emotion over time. Such effects predict that older adults would remember childhood and youth more positively than later adulthood. However, economic immigrants, whose childhood and youth reflect experiences of poverty and unemployment, may not show the effects of such revisionism. This study examined the remembered emotion of immigrant and non‐immigrant older Puerto Ricans whose early years corresponded to hard times on the island. Multilevel modelling showed that both groups exhibited the effects of the positivity and fading affect biases, but immigrants remembered childhood and youth more negatively than non‐immigrants. This suggests both accurate memory for a more negative past as well the effects of additional revisionism whereby a valued and chosen present is preferentially compared to the past. Copyright © 2006 John Wiley & Sons, Ltd.     

Informed Consent Procedure for Clinical Trials in Emergency Settings: The Polish Perspective

Setting reasonable and fair limits of emergency research acceptability in ethical norms and legal regulations must still adhere to the premise of well-being of the research subject over the interests of science and society. Informed consent of emergency patients to be enrolled in clinical trials is a particularly difficult issue due to impaired competencies of patients’ to give consent, short diagnostic and therapeutic windows, as well as the requirement to provide detailed information to participants. Whereas the Declaration of Helsinki, Good Clinical Practice guideline, Additional Protocol to the European Bioethical Convention concerning Biomedical Research, as well as appropriate regulations adopted by the Food and Drugs Administration (USA) allow waivers from participants’ consent or deferred consent for emergency research, the regulations of most European Community countries following the Clinical Trial Directive (2001/20/EC) do not give space for a deferred consent or a waiver from consent for adult patients (unless surrogate consent is made use of). This is even more confusing in case of Poland, where conflicting regulations on a waiver from a participant’s consent in emergency research exist and the regulations on surrogate consent of temporarily incompetent adults are too restrictive and authorise only the guardianship courts to consent, which is not or hardly feasible in practice. European Community regulations need to be amended to allow for implementation of the deferred consent or waivers from consent for emergency research in order to enable ethical research of emergency conditions that should become a large part of important public health priorities.     

ELOPTA: A novel microcontroller-based operant device

Operant devices have been used for many years in animal behavior research, yet such devices a regenerally highly specialized and quite expensive. Although commercial models are somewhat adaptable and resilient, they are also extremely expensive and are controlled by difficult to learn proprietary software. As an alternative to commercial devices, we have designed and produced a fully functional, programmable operant device, using a PICmicro microcontroller (Microchip Technology, Inc.). The electronic operant testing apparatus (ELOPTA) is designed to deliver food when a study animal, in this case a bird, successfully depresses the correct sequence of illuminated keys. The device logs each keypress and can detect and log whenever a test animal i spositioned at the device. Data can be easily transferred to a computer and imported into any statistical analysis software. At about 3% the cost of a commercial device, ELOPTA will advance behavioral sciences, including behavioral ecology, animal learning and cognition, and ethology.     

The effect of nonmasking distractors on the priming of motor responses

Masked stimuli (primes) can affect the preparation of a motor response to subsequently presented target. In numerous studies, it has been shown that the compatibility effect is biphasic as it develops over time: positive (benefits for compatible trials and costs for incompatible trials) for short prime-target temporal distances and negative (benefits for incompatible trials and costs for compatible trials) for long ones. What triggers the 2nd phase is the matter of the current debate. According to the self-inhibition hypothesis, the motor response elicited by a prime is automatically followed by an inhibition phase. The object-updating and mask-triggered inhibition hypotheses assume that this phase is triggered by the mask, provided that it contains features calling for the alternative response. In the present study, the author shows that the compatibility effect is modulated on the temporal position of a nonmasking distractor presented after the prime and before the target. With a distractor possessing task-relevant features, the compatibility effect was found to be negative for short prime- distractor intervals and for moderate prime-target intervals. The consequences of these results for the 3 hypotheses are discussed.     

Interpolation in structure from motion.

We investigated surface interpolation in displays of structure from motion (SFM). To do so, we introduced a new method for measuring surface perception in dynamic displays--the SFM probe. An SFM probe is a dot that moves rigidly with the dots on a simulated surface, and whose distance from that surface can be adjusted with a joystick or similar control. The displays we studied were random-dot cylinders containing a vertical strip devoid of feature points (the gap). Subjects adjusted an SFM probe, presented in the gap, until the probe dot appeared to be on the surface. Variability in probe-dot placement decreased with increasing texture density on the cylinder and increased with increasing gap width. Subjects showed a consistent bias to place the probe dot outside the cylinder. This bias increased with increasing texture density for the SFM displays. (The opposite bias was found in a static two-dimensional interpolation task with an arc whose curvature matched that of the cylinder: Subjects placed the probe dot inside the arc.) This outside bias is inconsistent with several theoretical approaches to surface interpolation.