The role of KIBRA in reconstructive episodic memory

In order to retrieve episodic past events, the missing information needs to be reconstructed using information stored in semantic memory. Failures in these reconstructive processes are expressed as false memories. KIBRA single nucleotide polymorphism (rs17070145) has been linked to episodic memory performance as well as an increased risk of Alzheimer’s disease and post-traumatic stress disorder (PTSD). Here, the role of KIBRA rs17070145 polymorphism (male and female CC vs. CT/TT carriers) in reconstructive episodic memory in the Deese-Roediger-McDermott (DRM) paradigm was investigated in N = 219 healthy individuals. Female participants outperformed males in the free recall condition. Furthermore, a trend towards a gender x genotype interaction was found for false recognition rates. Female CT/TT carriers exhibited a lower proportion of false recognition rates for associated critical lures as compared to male CT/TT. Additionally, an association between KIBRA rs17070145 genotype, familiarity and recollection based recognition performance was found. In trials with correct recognition of listed items CT/TT carriers showed more “remember”, but fewer “know” responses as compared to CC carriers. Our findings suggest that the T-allele of KIBRA rs17070145 supports recollection based episodic memory retrieval and contributes to memory accuracy in a gender dependent manner. Findings are discussed in the context of the specific contribution of KIBRA related SNPs to reconstructive episodic memory and its implications for cognitive and emotional symptoms in dementia and PTS

Effects of appraisal training on responses to a distressing autobiographical event

Dysfunctional appraisals are a key factor suggested to be involved in the development and maintenance of PTSD. Research has shown that experimental induction of a positive or negative appraisal style following a laboratory stressor affects analogue posttraumatic stress symptoms. This supports a causal role of appraisal in the development of traumatic stress symptoms and the therapeutic promise of modifying appraisals to reduce PTSD symptoms. The present study aimed to extend previous findings by investigating the effects of experimentally induced appraisals on reactions to a naturally occurring analogue trauma and by examining effects on both explicit and implicit appraisals. Participants who had experienced a distressing life event were asked to imagine themselves in the most distressing moment of that event and then received either a positive or negative Cognitive Bias Modification training targeting appraisals (CBM-App). The CBM-App training induced training-congruent appraisals, but group differences in changes in appraisal over training were only seen for explicit and not implicit appraisals. However, participants trained positively reported less intrusion distress over the subsequent week than those trained negatively, and lower levels of overall posttraumatic stress symptoms. These data support the causal relationship between appraisals and trauma distress, and further illuminate the mechanisms linking the two

The dopamine D2 receptor mediates approach-avoidance tendencies in smokers

Dopamine D2 receptors (DRD2) have been strongly implicated in reward processing of natural stimuli and drugs. By using the Approach-Avoidance Task (AAT), we recently demonstrated that smokers show an increased approach bias toward smoking-related cues but not toward naturally-rewarding stimuli. Here we examined the contribution of the DRD2 Taq1B polymorphism to smokers’ and non-smokers’ responsivity toward smoking versus naturally-rewarding stimuli in the AAT. Smokers carrying the minor B1 allele of the DRD2 Taq1B polymorphism showed reduced approach behavior for food-related pictures compared to non-smokers with the same allele. In the group of smokers, a higher approach-bias toward smoking-related compared to food-related pictures was found in carriers of the B1 allele. This pattern was not evident in smokers homozygous for the B2 allele. Additionally, smokers with the B1 allele reported fewer attempts to quit smoking relative to smokers homozygous for the B2 allele. This is the first study demonstrating that behavioral shifts in response to smoking relative to natural rewards in smokers are mediated by the DRD2 Taq1B polymorphism. Our results indicate a reduced natural-reward brain reactivity in smokers with a genetically determined decrease in dopaminergic activity (i.e., reduction of DRD2 availability). It remains to be determined whether this pattern might be related to a different outcome after psychological cessation interventions, i.e. AAT modification paradigms, in smokers

Pathologic and Phenotypic Alterations in a Mouse Expressing a Connexin47 Missense Mutation That Causes Pelizaeus-Merzbacher–Like Disease in Humans

Gap junction channels are intercellular conduits that allow diffusional exchange of ions, second messengers, and metabolites. Human oligodendrocytes express the gap junction protein connexin47 (Cx47), which is encoded by the GJC2 gene. The autosomal recessive mutation hCx47M283T causes Pelizaeus-Merzbacher–like disease 1 (PMLD1), a progressive leukodystrophy characterized by hypomyelination, retarded motor development, nystagmus, and spasticity. We introduced the human missense mutation into the orthologous position of the mouse Gjc2 gene and inserted the mCx47M282T coding sequence into the mouse genome via homologous recombination in embryonic stem cells. Three-week-old homozygous Cx47M282T mice displayed impaired rotarod performance but unchanged open-field behavior. 10-15-day-old homozygous Cx47M282T and Cx47 null mice revealed a more than 80% reduction in the number of cells participating in glial networks after biocytin injections into oligodendrocytes in sections of corpus callosum. Homozygous expression of mCx47M282T resulted in reduced MBP expression and astrogliosis in the cerebellum of ten-day-old mice which could also be detected in Cx47 null mice of the same age. Three-month-old homozygous Cx47M282T mice exhibited neither altered open-field behavior nor impaired rotarod performance anymore. Adult mCx47M282T expressing mice did not show substantial myelin alterations, but homozygous Cx47M282T mice, additionally deprived of connexin32, which is also expressed in oligodendrocytes, died within six weeks after birth and displayed severe myelin defects accompanied by astrogliosis and activated microglia. These results strongly suggest that PMLD1 is caused by the loss of Cx47 channel function that results in impaired panglial coupling in white matter tissue

(PREPRINT) Plank & Zlomuzica, 2024, coherence in social media posts

The extraction of linguistic markers from social media posts which are indicative of the onset and course of mental disorders offers great potential to mental healthcare. In the present study, we extracted over one million posts from the popular social media platform reddit to analyze speech coherence which reflects formal thought disorder and is a characteristic feature of schizophrenia and associated psychotic disorders. Natural language processing (NLP) models were used to perform an automated quantification of speech coherence. While controlling for the emotional tone and subjectivity, we demonstrated that posts made in forums geared towards disorders with a higher degree of psychotic and formal thought disorder symptoms tend to show a lower level of coherence. The lowest coherence scores were detected in posts made in forums on dissociative identity disorder, schizophrenia and bipolar disorder followed by a medium level of coherence in posts submitted to a forum on autism and post-traumatic stress disorder. In contrast, a relatively high level of coherence was detected in posts related to obsessive compulsive disorder, depression, anxiety and attention-deficit hyperactivity disorder. Our findings provide promising first evidence for a possible utility of NLP-based coherence analyses for the early detection and prevention of psychosis on the basis of posts gathered from publicly available social media data. This opens new avenues for large-scale prevention programs aimed at high-risk populations

The role of self-efficacy in specific fears.

Low self-efficacy for threatening stimuli and situations has been proposed as an important etiological factor in the development and maintenance of specific phobias. The present study examined the relationships between general self-efficacy (GSE), specific self-efficacy (SSE) and specific fears in a representative sample (n = 717). While GSE was associated with higher self-reported fear and avoidance, SSE (e.g. SSE in the presence of animal-related fear) was more related to specific fears. SSE turned out to be a significant predictor of specific fear even after controlling for trait anxiety, age and gender. Interestingly, the association between SSE and specific fear differed across the different fear categories. Fear and avoidance of blood/injection/injuries showed the highest associations with SSE. In contrast, the association between natural environment-related fear and avoidance and GSE or SSE together was only modest. Exploratory analyses revealed a gender-specific effect on the strength of the association between SSE and specific fears. Women scored higher in animal-related fears and SSE. Our findings support the self-efficacy hypothesis of anxiety disorder development and provide a more detailed insight into the role of GSE and SSE in specific fears and phobias

Progress in Episodic Memory Research

Episodic memory refers to the ability to remember personal experiences in terms of what happened and where and when it happened. Humans are also able to remember the specific perceptions, emotions and thoughts they had during a particular experience. This highly sophisticated and unique memory system is extremely sensitive to cerebral aging, neurodegenerative and neuropsychiatric diseases. The field of episodic memory research is a continuously expanding and fascinating area that unites a broad spectrum of scientists who represent a variety of research disciplines including neurobiology, medicine, psychology and philosophy. Nevertheless, important questions still remain to be addressed. This research topic on the Progress in Episodic Memory Research covers past and current directions in research dedicated to the neurobiology, neuropathology, development, measurement and treatment of episodic memory