Timo Giesbrecht

Caffeine as an attention enhancer: reviewing existing assumptions

RationaleDespite the large number of studies on the behavioural effects of caffeine, an unequivocal conclusion had not been reached. In this review, we seek to disentangle a number of questions.ObjectiveWhereas there is a general consensus that caffeine can improve performance on simple tasks, it is not clear whether complex tasks are also affected, or if caffeine affects performance of the three attention networks (alerting, orienting and executive control). Other questions being raised in this review are whether effects are more pronounced for higher levels of caffeine, are influenced by habitual caffeine use and whether there effects are due to withdrawal reversal.MethodLiterature review of double-blind placebo controlled studies that assessed acute effects of caffeine on attention tasks in healthy adult volunteers.ResultsCaffeine improves performance on simple and complex attention tasks, and affects the alerting, and executive control networks. Furthermore, there is inconclusive evidence on dose-related performance effects of caffeine, or the influence of habitual caffeine consumption on the performance effects of caffeine. Finally, caffeine’s effects cannot be attributed to withdrawal reversal.ConclusionsEvidence shows that caffeine has clear beneficial effects on attention, and that the effects are even more widespread than previously assumed.

Stress selectively and lastingly promotes learning of context-related high arousing information

The secretion of adrenal stress hormones in response to acute stress is known to affect learning and memory, particularly for emotionally arousing memory material. Here, we investigated whether stress-induced modulation of learning and memory performance depends on (i) the conceptual relatedness between the material to be learned/remembered and the stressor and (ii) the timing of stress exposure versus learning phase. Participants learned stressor-related and stressor-unrelated words of varying arousal 1h prior to, immediately following, or 2h after exposure to the Trier Social Stress Test (all groups n=16). Twenty-four hours later, delayed free recall was assessed. Cortisol and alpha-amylase were sampled to evaluate if concurrent stress-induced raised glucocorticoid levels and high adrenergic activity are implicated in modulating learning performance. Our results demonstrate that immediate and delayed post-stress learning selectively enhanced the learning and delayed recall of stressor-related high arousing words. This enhancing effect was strongly associated with concurrent stress-induced cortisol and sympathetic activity. Our data suggest that when to-be-learned information is conceptually related to a stressor and considered important (i.e., arousing) by the individual, learning under stressful circumstances results in improved memorability afterwards.

Context-dependent enhancement of declarative memory performance following acute psychosocial stress

Studies on how acute stress affects learning and memory have yielded inconsistent findings, with some studies reporting enhancing effects while others report impairing effects. Recently, Joëls et al. [Joëls, M., Pu, Z., Wiegert, O., Oitzl, M.S., Krugers, H.J., 2006. Learning under stress: how does it work? Trends in Cognitive Sciences, 10, 152-158] argued that stress will enhance memory only when the memory acquisition phase and stressor share the same spatiotemporal context (i.e., context-congruency). The current study tested this hypothesis by looking at whether context-congruent stress enhances declarative memory performance. Undergraduates were assigned to a personality stress group (n=16), a memory stress group (n=18), or a no-stress control group (n=18). While being exposed to the acute stressor or a control task, participants encoded personality- and memory-related words and were tested for free recall 24h later. Relative to controls, stress significantly enhanced recall of context-congruent words, but only for personality words. This suggests that acute stress may strengthen the consolidation of memory material when the stressor matches the to-be-remembered information in place and time.

De-constructing depersonalization: Further evidence for symptom clusters

Depersonalization disorder is defined in the DSM-IV-TR using a single symptom criterion, which does not do justice to the phenomenological complexity of the disorder. In 394 affected adults, the Cambridge Depersonalization Scale yielded five factors (numbing, unreality of self, perceptual alterations, unreality of surroundings, and temporal disintegration), put forth as symptom criteria for a better diagnosis of depersonalization disorder.

Dissociation and Dissociative Disorders Challenging Conventional Wisdom

Conventional wisdom holds that dissociation is a coping mechanism triggered by exposure to intense stressors. Drawing on recent research from multiple laboratories, we challenge this prevailing posttraumatic model of dissociation and dissociative disorders. Proponents of this model hold that dissociation and dissociative disorders are associated with (a) intense objective stressors (e.g., childhood trauma), (b) serious cognitive deficits that impede processing of emotionally laden information, and (c) an avoidant information-processing style characterized by a tendency to forget painful memories. We review findings that contradict these widely accepted assumptions and argue that a sociocognitive model better accounts for the extant data. We further propose a perspective on dissociation based on a recently established link between a labile sleep–wake cycle and memory errors, cognitive failures, problems in attentional control, and difficulties in distinguishing fantasy from reality. We conclude that this perspective may help to reconcile the posttraumatic and sociocognitive models of dissociation and dissociative disorders.

Dissociation in undergraduate students: disruptions in executive functioning

The concept of dissociation refers to disruptions in attentional control. Attentional control is an executive function. Few studies have addressed the link between dissociation and executive functioning. Our study investigated this relationship in a sample of undergraduate students (N = 185) who completed the Dissociative Experiences Scale and the Random Number Generation Task. We found that minor disruptions in executive functioning were related to a subclass of dissociative experiences, notably dissociative amnesia and the Dissociative Experiences Scale Taxon. However, the two other subscales of the Dissociative Experiences Scale, measuring depersonalization and absorption, were unrelated to executive functioning. Our findings suggest that a failure to inhibit previous responses might contribute to the pathological memory manifestations of dissociation.

The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness

Abstract The non-proteinic amino acid L-theanine and caffeine, a methylxanthine derivative, are naturally occurring ingredients in tea. The present study investigated the effect of a combination of 97 mg L-theanine and 40 mg caffeine as compared to placebo treatment on cognitive performance, alertness, blood pressure, and heart rate in a sample of young adults (n = 44). Cognitive performance, self-reported mood, blood pressure, and heart rate were measured before L-theanine and caffeine administration (i.e. at baseline) and 20 min and 70 min thereafter. The combination of moderate levels of L-theanine and caffeine significantly improved accuracy during task switching and self-reported alertness (both P < 0.01) and reduced self-reported tiredness (P < 0.05). There were no significant effects on other cognitive tasks, such as visual search, choice reaction times, or mental rotation. The present results suggest that 97 mg of L-theanine in combination with 40 mg of caffeine helps to focus attention during a demanding cognitive task.

Why dissociation and schizotypy overlap: the joint influence of fantasy proneness, cognitive failures, and childhood trauma.

A number of studies have noted that dissociative symptoms (e.g., feelings of derealization, depersonalization, memory complaints, absorption) overlap with the tendency to report psychotic-like experiences (i.e., schizotypy). The question arises as to what may account for the shared variance between dissociation and schizotypy. The present study investigated whether fantasy proneness, cognitive failures, and childhood trauma may jointly explain the dissociation-schizotypy link. To this end, we administered the Dissociative Experiences Scale, the Schizotypal Personality Scale, the Creative Experiences Questionnaire, the Cognitive Failures Questionnaire, and the Childhood Trauma Questionnaire to a sample of undergraduates (N = 185). Fantasy proneness, cognitive failures, and childhood trauma together explained substantial part (58%) of the dissociation-schizotypy link. The present study succeeded in explaining a considerate part of the shared variance between dissociation and schizotypy.

The Trauma Model of Dissociation: Inconvenient Truths and Stubborn Fictions. Comment on Dalenberg Et Al. (2012)

Dalenberg et al. (2012) argued that convincing evidence (a) supports the longstanding trauma model (TM), which posits that early trauma plays a key role in the genesis of dissociation; and (b) refutes the fantasy model (FM), which posits that fantasy proneness, suggestibility, cognitive failures, and other variables foster dissociation. We review evidence bearing on Dalenberg et al.s 8 predictions and find them largely wanting in empirical support. We contend that the authors repeat errors committed by many previous proponents of the TM, such as attributing a central etiological role to trauma in the absence of sufficient evidence. Specifically, Dalenberg et al. leap too quickly from correlational data to causal conclusions, do not adequately consider the lack of corroboration of abuse in many studies, and underestimate the relation between dissociation and false memories. Nevertheless, we identify points of agreement between the TM and FM regarding potential moderators and mediators of dissociative symptoms (e.g., family environment, biological vulnerabilities) and the hypothesis that dissociative identity disorder is a disorder of self-understanding. We acknowledge that trauma may play a causal role in dissociation but that this role is less central and specific than Dalenberg et al. contend. Finally, although a key assumption of the TM is dissociative amnesia, the notion that people can encode traumatic experiences without being able to recall them lacks strong empirical support. Accordingly, we conclude that the field should now abandon the simple trauma-dissociation model and embrace multifactorial models that accommodate the diversity of causes of dissociation and dissociative disorders.

Cognitive Functioning in Depersonalization Disorder

Depersonalization disorder (DPD) is a dissociative disorder characterized by a subjective sense of unreality and detachment, and has been associated with deficits in perception and short-term memory. In this study, 21 DPD and 17 healthy comparison participants free of psychiatric disorders were administered a comprehensive neuropsychologic battery. The groups did not differ in full-scale, verbal, and performance IQ (Wechsler Adult Intelligence Scale), in working memory (Paced Auditory Serial Addition Test), or in selective attention (Digit Span with Distracters). The DPD group performed significantly worse on immediate visual and verbal recall (Wechsler Memory Scale, Revised), but not on delayed recall. Dissociation severity was significantly correlated with processing slowness and distractibility. We conclude that DPD is associated with cognitive disruptions in early perceptual and attentional processes.