Developmental changes of sleep spindles and their impact on sleep‐dependent memory consolidation and general cognitive abilities: A longitudinal approach

Sleep spindles are related to sleep‐dependent memory consolidation and general cognitive abilities. However, they undergo drastic maturational changes during adolescence. Here we used a longitudinal approach (across 7 years) to explore whether developmental changes in sleep spindle density can explain individual differences in sleep‐dependent memory consolidation and general cognitive abilities. Ambulatory polysomnography was recorded during four nights in 34 healthy subjects (24 female) with two nights (baseline and experimental) at initial recording (age range 8–11 years) and two nights at follow‐up recording (age range 14–18 years). For declarative learning, participants encoded word pairs with a subsequent recall before and after sleep. General cognitive abilities were measured by the Wechsler Intelligence Scale. Higher slow (11–13 Hz) than fast (13–15 Hz) spindle density at frontal, central, and parietal sites during initial recordings, followed by a shift to higher fast than slow spindle density at central and parietal sites during follow‐up recordings, suggest that mature spindle topography develops throughout adolescence. Fast spindle density increases from baseline to experimental night were positively related to sleep‐dependent memory consolidation. In addition, we found that the development of fast spindles predicted the improvement in memory consolidation across the two longitudinal measurements, a finding that underlines a crucial role for mature fast spindles for sleep‐dependent memory consolidation. Furthermore, slow spindle changes across adolescence were related to general cognitive abilities, a relationship that could indicate the maturation of frontal networks relevant for efficient cognitive processing. A video abstract of this article can be viewed at: https://www.youtube.com/watch?v=7NXJzm8HbIw and https://www.youtube.com/watch?v=iuMQY1OIJ0s     

Differential relational encoding of categorical information in memory for action events

Memory for action phrases is better if the actions are enacted in subject-performed tasks (SPTs) than if they are only listened to in verbal tasks (VTs). This effect is ascribed to better item-specific encoding of SPTs than of VTs. The role of interitem relational information is controversial, and the findings of clustering with categorically structured lists are inconsistent (see Engelkamp, 1998). The present study contributes to clarifying these effects by demonstrating that intentional relational encoding can be used more efficiently in VTs than in SPTs and influences the degree of clustering. If the list structure is not obvious, inducing intentional encoding by presenting the category labels prior to list presentation and asking subjects to use this preinformation increases clustering in VTs but not in SPTs. Without preinformation, clustering scores of VTs and SPTs did not differ, with preinformation, clustering of VTs was stronger than that of SPTs. The authors suggest how the inconsistent findings with regard to clustering effects can be explained.     

Memory for actions: Item and relational information in categorized lists

Enacting action phrases in subject-performed tasks (SPTs) leads to better free recall than hearing or reading the same materials in verbal tasks (VTs). This enactment effect is usually explained by better item-specific information in SPTs than in VTs. The role of relational information is controversial. In the present paper, we will take the multiple recall approach to study the role of item and relational information in memory for actions by computing the number of item gains and the number of item losses over trials. This approach has previously been applied to lists of unrelated action phrases. We applied it to categorically related lists, also allowing a measure of relational information by clustering scores. It was found that SPTs produced more item gains than VTs. This finding confirmed the assumption that SPTs provide better item-specific information than VTs. The number of item losses did not differ between VTs and SPTs. This finding suggests that relational information is equally provided by VTs and SPTs. However, the organizational scores showed a more differentiated picture. Clustering was greater in SPTs than in VTs with randomly presented lists, but not with blocked lists. We suggested that these results, as well as other findings from the literature, could be explained by distinguishing automatic and strategic processes and the types of item associations that are addressed by these processes.     

The item-order hypothesis reconsidered: The role of order information in free recall

According to the item-order approach of free recall, in pure short lists the free recall of unrelated items is organized according to their order of presentation in the study list. The approach was applied in the present study to experimenter-performed tasks (EPTs) and subject-performed tasks (SPTs). It claims that EPTs provide better serial order information than SPTs. Consequently, free recall of EPTs should be more organized along the presentation order of the items than the free recall of SPTs. In three experiments, some specific aspects of this approach were studied. Firstly, it was demonstrated that serial retrieval is not strongly used spontaneously and that its use is overestimated in the literature because it is usually evoked by an order reconstruction test which follows free recall testing. Secondly, a serial retrieval strategy in free recall can be encouraged by explicit instructions. Finally, the present experiments showed that a serial output strategy alone does not allow one to predict performance in free recall. The implications of these findings for the item-order approach will be discussed.     

Staff members' feelings toward psychiatric patients related to their own and the patient's self-image and gender

The relation between staff members' feelings toward a patient and their own and the patient's self-image in different gender combination groups was studied. Staff at 16 psychiatric treatment homes for patients with severe psychopathology reported their feelings toward their patients on a number of occasions. At the start of treatment, both staff members and patients rated their self-images using the Structural Analysis of Social Behavior (SASB). Male staff seemed less influenced by the patient, with their feelings relating mainly to aspects of their own self-image, while the feelings of the female staff were more related to the patient's self-image. The patient's diagnosis was less important for a staff member's feelings than that member's self-image. Generally, the relation between feelings and self-image was stronger for negative feelings. The results point to the importance of understanding more about the influence of staff members' self-structure on their negative feelings toward their patients and how this relates to both the staff member's and patient's gender.     

Dissociation of oxytocin effects on body weight in two variants of female Sprague-Dawley rats

As a counterpoint to studies that make a case for the use of oxytocin in short-term inhibition of food intake, the aim of the present study was to determine whether the peptide facilitates weight gain in female rats in a more long-term perspective. Two different variants of female Sprague-Dawley rats were used. The two variants differed in daily weight gain (0.38 g/day vs. 1.41 g/day during 28 days), and were designated slowly and rapidly growing rats (SGR and RGR) respectively. Oxytocin 1 mg/kg given s.c. to SGR for a five-day period increased weight gain significantly in comparison to a previous five-day period with NaCl-treatment (18.0 g/5 days versus 5.0 g/5 days; p<0.01). In a separate study, oxytocin 1 mg/kg given for four days increased weight gain significantly in SGR versus saline-treated controls (7.5 g/4 days versus 1.6 g/4 days; p<0.05). The weight-difference persisted six days later (p<0.001). The weight increase of oxytocin occurred only during estrus (p<0.05) and was not accompanied by any measurable increase in food intake. In RGR, oxytocin-treatment decreased food intake significantly (p<0.001) and tended to decrease weight gain, although not significantly. The SGR and RGR also had different endocrine profiles with, for example, twice as high oxytocin (p<0.01) and insulin levels (p<0.01) in RGR compared to the SGR. These data suggest that oxytocin influences weight gain and food intake differently in the two variants of Sprague-Dawley rats, perhaps depending on factors such as endocrine profile and oxytocin sensitivity.     

A COMPARISON BETWEEN CHILDREN AND ADULTS IN A PRISONERS' DILEMMA GAME

S jöberg , L., B okander , I., D encik , L. & L indbom , K. A comparison between children and adults in a prisoner's dilemma game. Scand. J. Psychol ., 1969, 10 , 158–166.— A comparative study using three different stooge strategies. The game was played for a total of 67 trials. Children (4–6 years old) exhibited more cooperation than adults, and a stronger tendency to make a cooperative move after own defection, regardless of outcome. Both the frequency of cooperative moves and the state-conditioned propensities showed some stability over time and similar intercorrelations for adults and children.     

Confirmatory Validation and Measurement Equivalence of the Eating Loss of Control Scale in Binge Eating and Non-Clinical Samples

Although Loss of Control (LOC) is a transdiagnostic factor in eating pathology, there are few standalone assessments of LOC. The objective of this study was to evaluate the uni-dimensionality and measurement equivalence of the Eating Loss of Control Scale (ELOCS). Confirmatory factor analyses were used to achieve a well-fitting uni-dimensional model in clinical (N?=?226) and non-clinical (N?=?476) samples. Measurement equivalence was tested in a factor analytic framework, and effect sizes were computed to evaluate the impact of non-equivalence. A well-fitting model was achieved in both samples after the removal of 4 items. The instrument showed configural equivalence but not metric equivalence. Results suggest that the ELOCS is a reliable and valid measure of LOC in clinical and non-clinical samples. However, while the nature of the LOC construct is similar across binge eating and non-clinical participants, comparisons of ELOCS across these groups are affected by measurement non-equivalence. This research also revealed novel insights into the relative sensitivity of model fitting and effect size approaches to investigating measurement equivalence.     

Binding of multidimensional context information as a distinctive characteristic of remember judgments

This research investigated the cognitive processes underlying remember-know judgments in terms of contextual binding in multidimensional source memory. Stochastic dependence between the retrieval of different context attributes, which formed the empirical criterion of binding, was observed for remembered items but not for known items. Experiment 1 showed that the qualitative difference in the stochastic relation holds even if quantitative source-memory performance is equated for items with remember and know judgments. Experiment 2 generalized the findings to context information from different modalities, and Experiment 3 ruled out a spurious stochastic dependence due to interindividual differences. Supporting recent dual-process models of remember-know judgments, the findings show that remember and know judgments differ with respect to binding processes that correspond to episodic recollection.     

Does depression interfere with effort mobilization? Effects of dysphoria and task difficulty on cardiovascular response

On the basis of predictions of the mood-behavior model (G. H. E. Gendolla, 2000) and motivational intensity theory (J. W. Brehm & E. A. Self, 1989), the authors conducted 2 studies that critically tested the common assumption that dysphoria is associated with a motivational deficit. Dysphoric and nondysphoric undergraduates performed a cognitive task that was either easy or difficult. Effort intensity (i.e., resource mobilization) was assessed as performance-related cardiovascular reactivity. In support of the authors' predictions and in contrast to the popular view of a general motivational deficit, both studies found a crossover interaction between dysphoria and task difficulty: In the difficult condition, nondysphoric participants indeed showed stronger systolic blood pressure reactivity than dysphoric participants. But in the easy condition, dysphoric participants showed stronger systolic reactivity than nondysphoric participants. The findings are discussed with respect to motivational deficits in depression and possible underlying mechanisms.