Motor interference does not impair the memory consolidation of imagined movements

The present study aimed to investigate whether an interference task might impact the sleep-dependent consolidation process of a mentally learned sequence of movements. Thirty-two participants were subjected to a first training session through motor imagery (MI) or physical practice (PP) of a finger sequence learning task. After 2 h, half of the participants were requested to perform a second interfering PP task (reversed finger sequence). All participants were finally re-tested following a night of sleep on the first finger sequence. The main findings revealed delayed performance gains following a night of sleep in the MI group, i.e. the interfering task did not alter the consolidation process, by contrast to the PP group. These results confirm that MI practice might result in less retroactive interference than PP, and further highlight the relevance of the first night of sleep for the consolidation process following MI practice. These data might thus contribute to determine in greater details the practical implications of mental training in motor learning and rehabilitation.     

Chronic, severe hypertension does not impair spatial learning and memory in Sprague-Dawley rats

This study tested the hypothesis that long-term hypertension impairs spatial learning and memory in rats. In 6-wk-old Sprague-Dawley rats, chronic hypertension was induced by placing one of three sizes of stainless steel clips around the descending aorta (above the renal artery), resulting in a 20–80-mm Hg increase of arterial pressure in all arteries above the clip, that is, the upper trunk and head. Ten months later, the rats were tested for 5 d in a repeated-acquisition water maze task, and on the fifth day, they were tested in a probe trial; that is, there was no escape platform present. At the end of the testing period, the nonsurgical and sham control groups had similar final escape latencies (16±4 sec and 23±9 sec, respectively) that were not significantly different from those of the three hypertensive groups. Rats with mild hypertension (140–160 mm Hg) had a final escape latency of 25±6 sec, whereas severely hypertensive rats (170–199 mm Hg) had a final escape latency of 21±7 sec and extremely hypertensive rats (>200 Hg) had a final escape latency of 19±5 sec. All five groups also displayed a similar preference for the correct quadrant in the probe trial. Together, these data suggest that sustained, severe hypertension for over 10 mo is not sufficient to impair spatial learning and memory deficits in otherwise normal rats.     

Dissociation and memory fragmentation: experimental effects on meta-memory but not on actual memory performance

The relation between state dissociation and fragmentary memory was investigated by assessing both actual memory performance and meta-memory. From a sample of 330 normal subjects, two subsamples were selected on basis of trait dissociation, as measured by the Dissociative Experience Scale. Twenty subjects scoring above 30 and 20 subjects scoring below 10 were selected. Subjects watched an extremely aversive film, after which state dissociation was measured by the Peri-traumatic Dissociative Experience Scale. Four hours later memory fragmentation was assessed in two ways. Actual fragmentation was measured by a sequential memory task, and perceived fragmentation (meta-memory) was measured using a visual analogue scale. Subjects who tended to dissociate during the film judged their recollections of the film as more fragmentary. Although this finding is in line with clinical reports given by trauma victims, it was not sustained by objective evidence. That is, no effect was observed of state dissociation on the sequential memory task. The present findings suggest that the claim that dissociation induces memory fragmentation may have to be confined to meta-memory. Implications of this divergence between actual memory and meta-memory are discussed.     

Playing counter-strike versus running: The impact of leisure time activities and cortisol on intermediate-term memory in male students

The everyday life of students is characterized by hours of learning in order to pass exams. After learning they tend to opt for an occupation that provides them with a great deal of entertainment. It is obvious that it would be advantageous if the chosen activity had a positive impact on memory consolidation. Due to the circumstance that such activities can lead to stress and that memory is affected by stress we wanted to look at these coherences. We examined the effect of two different common leisure time activities on cortisol and memory to be able to formulate recommendations for society. For this purpose, a group was tested before and after playing a violent computer game while the second group was tested before and after running. In addition, a control group was set up. Salivary cortisol was measured at the beginning, during, and at the end of the experiment.Our data demonstrates that running increases cortisol levels and, performed immediately after a learning period, facilitates memorization of neutral information. In contrast, playing a violent computer game tends to impair memorization.The results of the present study have practical implications for the choice of recreational activities in the context of learning.     

Resource depletion does not influence prospective memory in college students

This paper reports an experiment designed to investigate the potential influence of prior acts of self-control on subsequent prospective memory performance. College undergraduates (n = 146) performed either a cognitively depleting initial task (e.g., mostly incongruent Stroop task) or a less resource-consuming version of that task (e.g., all congruent Stroop task). Subsequently, participants completed a prospective memory task that required attentionally demanding monitoring processes. The results demonstrated that prior acts of self-control do not impair the ability to execute a future intention in college-aged adults. We conceptually replicated these results in three additional depletion and prospective memory experiments. This research extends a growing number of studies demonstrating the boundary conditions of the resource depletion effect in cognitive tasks.     

Repeated checking causes distrust in memory but not in attention and perception

Repeated checking to reduce memory distrust seems to be counterproductive: it increases memory distrust. Obsessive-compulsive (OC) patients tend to be uncertain about other cognitive domains as well, like attention and perception. In an experiment with 70 healthy participants, we tested whether perseverative checking induces distrust not only in memory, but also in attention and perception. Participants were administered a computer task in which they had to activate, deactivate, and check threat-irrelevant stimuli, and rate their confidence in memory, attention, and perception in a pre-test and post-test. In between these tests, the relevant checking group performed 20 checks of the same stimuli used in the pre- and post-test. The irrelevant checking group performed 20 checks of different stimuli. Although memory accuracy improved in both groups, repeated checking reduced confidence in memory, vividness, and detail in the relevant checking group, but not in the irrelevant checking group. A trend was found towards a decline in attentional confidence in the relevant checking group only. Perception was not affected by repetitive checking. A replication study revealed similar results of relevant checking on meta-memory, however, the trend for attentional distrust was not confirmed. The results suggest that perseveration may be domain specific, i.e., only the cognitive processes that are subject to perseveration are affected.     

Enhanced perceived responsibility decreases metamemory but not memory accuracy in obsessive-compulsive disorder (OCD)

Mixed findings have been obtained in prior research with respect to the presence and severity of memory and metamemory deficits in obsessive-compulsive disorder (OCD). We tested the hypothesis that experimentally induced increments of subjective responsibility would lead to a disproportionately strong decline of memory confidence and enhanced response latencies in OCD while leaving memory accuracy unaffected. Twenty-eight OCD patients and 28 healthy controls were presented a computerized memory test framed with two different scenarios. In the neutral scenario, the participant was requested to imagine purchasing 15 items from a do-it-yourself store. In the recognition phase, the 15 needed items were presented along with 15 distractor items. The participant was asked to decide whether items were on his or her shopping list or not, graded by subjective confidence. In the responsibility scenario, the general experimental setup was analogous except that the participant now had to envision that he or she was a helper in a region recently struck by an earthquake, dispatched to provide 15 urgently needed goods from a nearby town. In line with prior work by our group, samples did not differ in either condition on memory accuracy in a subsequent recognition task. As hypothesized, OCD participants were less certain in their responses for the high responsibility condition than controls. Whereas patients and controls did not differ in their subjective estimates for memorized items, patients expressed stronger doubt that their earthquake mission was successful. The findings indicate that low memory confidence in OCD may only be elicited in situations where perceived responsibility is high and that patients may share higher performance standards ("good is not good enough") than controls when perceived responsibility is inflated.     

A categorical recall strategy does not explain animacy effects in episodic memory

Animate stimuli are better remembered than matched inanimate stimuli in free recall. Three experiments tested the hypothesis that animacy advantages are due to a more efficient use of a categorical retrieval cue. Experiment 1 developed an “embedded list” procedure that was designed to disrupt participants’ ability to perceive category structure at encoding; a strong animacy effect remained. Experiments 2 and 3 employed animate and inanimate word lists consisting of tightly constrained categories (four-footed animals and furniture). Experiment 2 failed to find an animacy advantage when the categorical structure was readily apparent, but the advantage returned in Experiment 3 when the embedded list procedure was employed using the same target words. These results provide strong evidence against an organizational account of the animacy effect, indicating that the animacy effect in episodic memory is probably due to item-specific factors related to animacy.     

Word order does not constrain phonological activation in single word production

It has recently been claimed that the canonical word order of a given language constrains phonological activation processes even in single word production (Janssen, Alario, & Caramazza, 2008). This hypothesis predicts for languages with canonical adjective–noun word order that naming an object (i.e., noun production) is facilitated if the task-irrelevant colour of the object (i.e., adjective) is phonologically similar to the object name (e.g., blue–boat as compared to red–boat). By contrast, there should be no corresponding effect in naming the colour of the object (i.e., adjective production). In an experiment with native speakers of German, however, we observed exactly the opposite pattern. Phonological congruency facilitated colour naming but had no effect on object naming. Together with extant data from other languages our results suggest that object colour naming is affected by the phonology of the object name but not vice versa, regardless of the canonical word order in the given language.     

An experimental study on mother-infant skin-to-skin contact in full-terms

In premature infants, daily skin-to-skin contact (SSC) has various beneficial effects on the health of the infant and the mother. These beneficial effects might extend to full-term infants. This experimental within-subject study examines the immediate effects of SSC on full-terms’ cortisol physiology during SSC and subsequent physiological and behavioral reactions to a mild stressor (a bathing session). Additionally, the effects of SSC on the quality of maternal behavior are examined.Between 5 and 7 weeks postpartum, 17 full-term infant-mother dyads were visited at home twice. During one home visit, a bathing session was proceeded by 50 min of mother-infant SSC, while during the other visit the bathing session was proceeded by 50 min of the infant resting alone. The order of the home visits was counterbalanced. Infant salivary cortisol measures were taken to measure the cortisol response to the experimental condition (SSC versus solitary resting) and the bathing session. Furthermore, infant behavioral distress and the quality of maternal behavior during the bathing session were scored from videotapes.Two-way within-subject repeated measures ANOVA’s showed that, when compared to solitary resting, full-terms’ cortisol concentrations significantly decreased during SSC, followed by higher cortisol reactivity in response to the subsequent bathing session. No effects of SSC on infant behavioral distress and maternal caregiving behavior were found. Apparently, a single session of mother-infant SSC can affect infant cortisol physiology in full-term infants. Future SSC research is needed to investigate the neurobiological mechanisms and dose-response relations in full-term infants.     

Education does not protect against age-related decline of switching focal attention in working memory

In this experimental study, effects of age and education on switching focal attention in working memory were investigated among 44 young (20-30 years) and 40 middle-aged individuals (50-60 years). To this end, a numeric n-back task comprising two lag conditions (1- and 2-back) was administered within groups. The results revealed a comparable increase of reaction time as a function of lag across age groups, but a disproportionate decrease of accuracy in the middle-aged relative to the young group. The latter effect did not interact with education, which challenges the cognitive reserve hypothesis. Moreover, the high-educated middle-aged participants showed a greater increase of reaction time as a function of lag than their low-educated counterparts. Apparently, they were not able to sustain their relatively high response speed across conditions. These results suggest that education does not protect against age-related decline of switching focal attention in working memory.     

Chimpanzees (Pan troglodytes) do not develop contingent reciprocity in an experimental task

Chimpanzees provide help to unrelated individuals in a broad range of situations. The pattern of helping within pairs suggests that contingent reciprocity may have been an important mechanism in the evolution of altruism in chimpanzees. However, correlational analyses of the cumulative pattern of interactions over time do not demonstrate that helping is contingent upon previous acts of altruism, as required by the theory of reciprocal altruism. Experimental studies provide a controlled approach to examine the importance of contingency in helping interactions. In this study, we evaluated whether chimpanzees would be more likely to provide food to a social partner from their home group if their partner had previously provided food for them. The chimpanzees manipulated a barpull apparatus in which actors could deliver rewards either to themselves and their partners or only to themselves. Our findings indicate that the chimpanzees’ responses were not consistently influenced by the behavior of their partners in previous rounds. Only one of the 11 dyads that we tested demonstrated positive reciprocity. We conclude that contingent reciprocity does not spontaneously arise in experimental settings, despite the fact that patterns of behavior in the field indicate that individuals cooperate preferentially with reciprocating partners.     

An action sequence held in memory can interfere with response selection of a target stimulus,but does not interfere with response activation of noise stimuli

Withholding an action plan in memory for later execution can delay execution of another action if the actions share a similar (compatible) action feature (e.g., response hand). We investigated whether this phenomenon, termed compatibility interference (CI), occurs for responses associated with a target as well as responses associated with distractors in a visual selection task. Participants planned and withheld a sequence of keypress responses (with their right or left hand), according to the identity of a stimulus (A), and then immediately executed a keypress response (with their right or left hand) to a second stimulus (B), according to the identity of a target letter appearing alone or among distractor letters. Distractor letters were either response compatible or incompatible with the target and appeared either simultaneously with the target (Experiments 1A and 2) or 100 msec before the target (Experiment 1B). Also, stimulus-response mapping was either 1:1 (Experiment 1) or 2:1 (Experiment 2). Results showed that the response to the Stimulus B target was delayed when it required the same response hand as Stimulus A, as opposed to a different hand. Also, the target reaction time for Stimulus B was greater when the target was flanked by incompatible distractors than when it was flanked by compatible distractors. Moreover, the degree of CI was consistent across the compatible-, incompatible-, and no-distractor conditions, indicating that CI generalizes to responses associated with a target, but not to those associated with distractors. Thus, CI occurs at a response selection, not at a response activation stage. Implications for the code occupation account for CI (e.g., Stoet & Hommel, 1999, 2002) and an alternative account for CI are discussed.     

Amygdala upregulation of NCAM polysialylation induced by auditory fear conditioning is not required for memory formation, but plays a role in fear extinction

There is much interest to understand the mechanisms leading to the establishment, maintenance, and extinction of fear memories. The amygdala has been critically involved in the processing of fear memories and a number of molecular changes have been implicated in this brain region in relation to fear learning. Although neural cell adhesion molecules (NCAMs) have been hypothesized to play a role, information available about their contribution to fear memories is scarce. We investigate here whether polysialylated NCAM (PSA-NCAM) contributes to auditory fear conditioning in the amygdala. First, PSA-NCAM expression was evaluated in different amygdala nuclei after auditory fear conditioning at two different shock intensities. Results showed that PSA-NCAM expression was increased 24 h post-training only in animals subjected to the highest shock intensity (1mA). Second, PSA-NCAM was cleaved in the basolateral amygdaloid complex through micro-infusions of the enzyme endoneuraminidase N, and the consequences of such treatment were investigated on the acquisition, consolidation, remote memory expression, and extinction of conditioned fear memories. Intra-amygdaloid cleavage of PSA-NCAM did not affect acquisition, consolidation or expression of remote fear memories. However, intra-amygdaloid PSA-NCAM cleavage enhanced fear extinction processes. These results suggest that upregulation of PSA-NCAM is a correlate of fear conditioning that is not necessary for the establishment of fear memory in the amygdala, but participates in mechanisms precluding fear extinction. These findings point out PSA-NCAM as a potential target for the treatment of psychopathologies that involve impairment in fear extinction.     

Conducting extinction in multiple contexts does not necessarily attenuate the renewal of shock expectancy in a fear-conditioning procedure with humans

The renewal of Pavlovian-conditioned responses may provide a model for the relapse of fear following extinction-based treatments for anxiety disorders. Renewal can be observed if conditional stimulus (CS) and unconditional stimulus (US) pairings are given in one context, extinction trials of CS presentations in a second context, prior to test trials of CS presentations in the original acquisition context (ABA renewal). We examined ABA renewal in humans by using a fear-conditioning procedure with an unpleasant shock US. A renewal of rated shock expectancy was demonstrated with this procedure. Conducting extinction treatment in multiple contexts was expected to attenuate the renewal effect. However, the renewal of shock expectancy persisted when extinction treatment was given across three or five different contexts. With the current renewal design, learning task, and measure of conditioned behaviour, extinction treatment does not appear to readily generalise to the test context. The use of multiple extinction treatments in a clinical setting may not necessarily reduce the likelihood of relapse via a renewal effect.     

Beliefs about memory among psychology students and their professors in psychodynamic clinical and experimental study programs

IntroductionResearch has shown that lay people, and even psychologists, may have distorted knowledge about memory functioning. May different study programs in psychology influence their ideas?Objective(s)The study was aimed at evaluating psychology students’ and psychology professors’ knowledge about memory and factors potentially affecting the accuracy of episodic memory reports in clinical and legal contexts.MethodA questionnaire was administered to introductory and advanced students of psychology enrolled at different curricula – experimental psychology and clinical psychology with a psychoanalytical orientation – and to professors teaching the courses in the same curricula.ResultsResults showed that advanced students and professors in experimental psychology have higher general knowledge of factors influencing memory performance than their peers, including memory issues of particular relevance to clinical psychology; no difference between the curricula was found for the introductory students.ConclusionThe results are discussed in terms of the risks that the lack of knowledge on memory functioning of the psychologists with a psychodynamic orientation may have in producing wrong reports in forensic contexts.     

Effects of peripheral immune activation on social behavior and adrenocortical activity in aggressive mice: Genotype-environment interactions

To explore genetic-developmental differences in the biobehavioral effects of induced illness, males from two lines of mice selectively bred for high or low levels of aggressive behavior were injected with endotoxin (Escherichia coli, LPS: 0.25 mg/kg, 1.25 mg/kg, or 2.5 mg, i.p.) or saline. Body temperature, weight, and locomotor activity were monitored immediately before and 8 and 24 hr after injection. Twenty-four hours after injection, social behaviors were assessed in a 10-min dyadic test, and hypothalamus, spleen, and serum were collected. In both lines, endotoxin treatment increased behavioral immobility ("freezing") and decreased social exploration. Other effects showed line differences: Males from the high-aggressive line had a lower threshold to endotoxin-induced effects on body temperature, weight loss, spleen weight, and corticosterone. Social reactivity (startle response to mild social investigation) increased in the high-aggressive line and decreased in the low-aggressive line after treatment. In the high-aggressive line only, endotoxin decreased attack frequency and increased latency to attack. The interactions between selected line (genotype) and endotoxin treatment (environment) demonstrate that genetic-developmental differences in social and aggressive behavior may indicate the extent to which immune stimuli (e.g., bacteria, viruses, cytokines) function as "biobehavioral stressors." Aggr. Behav. 23:93–105, 1997.© 1997 Wiley-Liss, Inc.