Some researchers have claimed that fragment completion tasks are dependent primarily on datadriven processing and are insensitive to conceptually driven processing. In this article we present four experiments demonstrating that conceptually driven processing affects fragment completion by showing that under appropriate conditions, studied words can facilitate identification of their picture and word fragments. We examine two theoretical explanations of this effect. First, we consider the possibility that subjects explicitly retrieve episodic representations in fragment completion. Analyses of correlations between priming and recall performance across items and subjects do not support this explanation. The alternative explanation is that there are two separate conceptual representations in memory. The first is assumed to mediate conceptual priming in fragment completion; the second is assumed to mediate free recall performance. A final experiment supports this view by demonstrating that even when differences between experimental conditions are made to disappear in fragment completion, they remain in free recall. Further applications of the notion of two semantic representations are discussed in the General Discussion.Discovering the relation between implicit and explicit memory tests has become a central issue in memory theory (Richardson-Klavehn & Bjork, 1988;Schacter, 1987). Operationally, explicit memory tests, such as recall and recognition, can be distinguished from implicit memory tests, such as fragment completion and perceptual identification, because instructions on an explicit memory tasks refer to an episode in the subject's past, whereas instructions on an implicit memory task do not. Explaining the relation between implicit and explicit memory has assumed a central role in memory theory because of the many demonstrations indicating that performance on the two types of memory tests is dissociated.We will begin this article by reviewing some of these dissociations. Following this we will describe Roediger's (Roediger & Blaxton, 1987;Weldon & Roediger, 1987; Weldon, Roediger, & Chalks, 1989) influential theoretical approach to the explanation of the dissociations between implicit and explicit memory. We will then present several experiments that demonstrate, contrary to the claims of Roediger and his colleagues, that conceptual or semantic information can play a role in fragment completion. The latter sections of the article are then devoted to explaining this novel result.

Posttraumatic stress disorder (PTSD) is a complex, heterogeneous disorder that develops following trauma and often includes perceptual, cognitive, affective, physiological, and psychological features. PTSD is characterized by hyperarousal, intrusive thoughts, exaggerated startle response, flashbacks, nightmares, sleep disturbances, emotional numbness, and persistent avoidance of trauma-associated stimuli. The efficacy of available treatments for PTSD may result in part from relief of associated depressive and anxiety-related symptoms in addition to treatment of core symptoms that derive from reexperiencing, numbing, and hyperarousal. Diverse, heterogeneous mechanisms of action and the ability to act broadly or very locally may enable brain stimulation devices to address PTSD core symptoms in more targeted ways. To achieve this goal, specific theoretical bases derived from novel, well-designed research protocols will be necessary. Brain stimulation devices include both long-used and new electrical and magnetic devices. Electroconvulsive therapy (ECT) and Cranial electrotherapy stimulation (CES) have both been in use for decades; transcranial magnetic stimulation (TMS), magnetic seizure therapy (MST), deep brain stimulation (DBS), transcranial Direct Current Stimulation (tDCS), and vagus nerve stimulation (VNS) have been developed recently, over approximately the past twenty years. The efficacy of brain stimulation has been demonstrated as a treatment for psychiatric and neurological disorders such as anxiety (CES), depression (ECT, CES, rTMS, VNS, DBS), obsessive-compulsive disorder (OCD) (DBS), essential tremor, dystonia (DBS), epilepsy (DBS, VNS), Parkinson Disease (DBS), pain (CES), and insomnia (CES). To date, limited data on brain stimulation for PTSD offer only modest guidance. ECT has shown some efficacy in reducing comorbid depression in PTSD patients but has not been demonstrated to improve most core PTSD symptoms. CES and VNS have shown some efficacy in reducing anxiety, findings that may suggest possible utility in relieving PTSD-associated anxiety. Treatment of animal models of PTSD with DBS suggests potential human benefit. Additional research and novel treatment options for PTSD are urgently needed. The potential usefulness of brain stimulation in treating PTSD deserves further exploration.

Objective. Autoimmune-prone B-cell activating factor transgenic mice, a mouse model of systemic lupus erythematosus and Sjögren's syndrome exhibit neuroinflammation, anxiety-like phenotype, deficit in adult hippocampal neurogenesis and impaired neurogenesis-dependent and neurogenesis-independent dentate gyrus long-term potentiation. Given that n−3 polyunsaturated fatty acids regulate hippocampal plasticity and inflammatory responses, we investigated whether n−3 polyunsaturated fatty acids-enriched diet might prevent age-dependent hippocampal changes in B-cell activating factor transgenic mice.Methods. B-cell activating factor transgenic mice were fed for 12 weeks with either n−3 polyunsaturated fatty acids-enriched or control diet and we tested the effect of this dietary supplementation on hippocampal inflammation, progenitor cell proliferation and neurogenesis-dependent and neurogenesis-independent long-term potentiation.Results. Dietary supplementation with n−-3 polyunsaturated fatty acids significantly decreased hippocampal microglial activation and increased the density of bromodeoxyuridine and doublecortin-positive newly-formed cells in the subventricular zone of hippocampus. Furthermore, B-cell activating factor transgenic mice fed with n-3 polyunsaturated fatty acids-enriched diet displayed normal long-term potentiation at the medial perforant pathway/dentate gyrus connections.Conclusions. The results indicate that n-3 fatty acids prevent neuroinflammation and deficits of hippocampal plasticity in B-cell activating factor transgenic mice and suggest that increased n-3 fatty acids intake might represent a potential therapeutic option to prevent neuropsychiatric symptoms associated with autoimmune diseases.

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