TDP-43 pathology in anterior temporal pole cortex in aging and Alzheimer's disease

TDP-43 pathology was investigated in the anterior temporal pole cortex (ATPC) and orbital frontal cortex (OFC), regions often degenerated in frontotemporal lobar degenerations (FTLD), in aging and Alzheimer's disease (AD). Diagnosis of dementia in the 1160 autopsied participants from 3 studies of community-dwelling elders was based on clinical evaluation and cognitive performance tests which were used to create summary measures of the five cognitive domains. Neuronal and glial TDP-43 cytoplasmic inclusions were quantitated in 8 brain regions by immunohistochemistry, and used in ANOVA and regression analyses. TDP-43 pathology was present in 547 (49.4%) participants in whom ATPC (41.9%) was the most frequently involved neocortical region and in 15.5% of these cases, ATPC was the only neocortical area with TDP-43 pathology suggesting not only that ATPC is involved early by TDP-43 but that ATPC may represent an intermediate stage between mesial temporal lobe involvement by TDP-43 and the last stage with involvement of other neocortical areas. To better study this intermediary neocortical stage, and to integrate with other staging schemes, our previous 3 stage distribution of TDP-43 pathology was revised to a 5 stage distribution scheme with stage 1 showing involvement of the amygdala only; stage 2 showed extension to hippocampus and/or entorhinal cortex; stage 3 showed extension to the ATPC; stage 4 - showed extension to the midtemporal cortex and/or OFC and finally in stage 5, there was extension to the midfrontal cortex. Clinically, cases in stages 2 to 5 had impaired episodic memory, however, stage 3 was distinct from stage 2 since stage 3 cases had significantly increased odds of dementia. The proportion of cases with hippocampal sclerosis increased progressively across the stages with stage 5 showing the largest proportion of hippocampal sclerosis cases. Stage 5 cases differed from other stages by having impairment of semantic memory and perceptual speed, in addition to episodic memory impairment. These data suggest that of the regions studied, TDP-43 pathology in the ATPC is an important early neocortical stage of TDP-43 progression in aging and AD while extension of TDP-43 pathology to the midfrontal cortex is a late stage associated with more severe and global cognitive impairment.

Play fighting and the development of the social brain: The rat's tale

The benefits gained by young animals engaging in play fighting have been a subject of conjecture for over a hundred years. Progress in understanding the behavioral development of play fighting and the underlying neurobiology of laboratory rats has produced a coherent model that sheds light on this matter. Depriving rats of typical peer-peer play experience during the juvenile period leads to adults with socio-cognitive deficiencies and these are correlated with physiological and anatomical changes to the neurons of the prefrontal cortex, especially the medial prefrontal cortex. Detailed analysis of juvenile peer play has shown that using the abilities needed to ensure that play fighting is reciprocal is critical for attaining these benefits. Therefore, unlike that which was posited by many earlier hypotheses, play fighting does not train specific motor actions, but rather, improves a skill set that can be applied in many different social and non-social contexts. There are still gaps in the rat model that need to be understood, but the model is well-enough developed to provide a framework for broader comparative studies of mammals from diverse lineages that engage in play fighting.

Bullying victimization in typically developing and clinical high risk (CHR) adolescents: A multimodal imaging study

BACKGROUND

Bullying has been shown to increase the risk of developing a psychotic disorder. To date, no studies have examined brain behavior relationships within the context of bullying victimization in clinical high-risk (CHR) youth, a group characterized by both gray and white matter abnormalities. The present study employed multimodal neuroimaging to examine possible neural mechanisms associated with bullying victimization.

METHODS

CHR and healthy volunteers underwent clinical interviews, parent reports and MRI scans. Regions of interest (ROIs) were picked based on sensitivity to environmental stress, including hippocampal, amygdala, and orbitofrontal cortex (OFC) structural ROIs, and uncinate fasciculus white matter integrity.

RESULTS

CHR individuals were more exposed to bullying victimization than healthy volunteers, and bullying was associated with depressive symptoms across the whole sample. CHR individuals exhibited smaller volumes in OFC, but not in other ROIs. Increased bullying exposure was associated with lower medial OFC volumes in CHR and HV groups independently. Results ought to be interpreted as preliminary, as they did not survive correction at the whole brain level.

DISCUSSION

Bullying victimization may affect or be affected by volumetric OFC differences in both healthy and CHR individuals. However, given CHR showed greater exposure to bullying as well as underlying vulnerability (e.g. lower volumes), results also point to etiological clues and novel intervention targets, though future replication is needed in better powered samples.

Neurons in rat orbitofrontal cortex and medial prefrontal cortex exhibit distinct responses in reward and strategy-update in a risk-based decision-making task

The orbitofrontal cortex (OFC) and the medial prefrontal cortex (mPFC) are known to participate in risk-based decision-making. However, whether neuronal activities of these two brain regions play similar or differential roles during different stages of risk-based decision-making process remains unknown. Here we conducted multi-channel in vivo recordings in the OFC and mPFC simultaneously when rats were performing a gambling task. Rats were trained to update strategy as the task was shifted in two stages. Behavioral testing suggests that rats exhibited different risk preferences and response latencies to food rewards during stage-1 and stage-2. Indeed, the firing patterns and numbers of non-specific neurons and nosepoking-predicting neurons were similar in OFC and mPFC. However, there were no reward-expecting neurons and significantly more reward-excitatory neurons (fired as rats received rewards) in the mPFC. Further analyses suggested that nosepoking-predicting neurons may encode the overall value of reward and strategy, whereas reward-expecting neurons show more intensive firing to a big food reward in the OFC. Nosepoking-predicting neurons in mPFC showed no correlation with decision-making strategy updating, whereas the response of reward-excitatory neurons in mPFC, which were barely observed in OFC, were inhibited during nosepoking, but were enhanced in the post-nosepoking period. These findings indicate that neurons in the OFC and mPFC exhibit distinct responses in decision-making process during reward consumption and strategy updating. Specifically, OFC encodes the overall value of a choice and is thus important for learning and strategy updating, whereas mPFC plays a key role in monitoring and execution of a strategy.

Relationship between self-defeating humor and the Gray matter volume in the orbital frontal cortex: the moderating effect of divergent thinking

The self-defeating humor style is characterized by the excessive use of self-mockery, fawning over others and ineffective denial of negative emotions. The differences in brain structures responsible for self-defeating humor and the role of divergent thinking (DT) in this relationship have not been directly investigated in a large sample. Using voxel-based morphometry (VBM), we identified the association between regional gray matter volume (GMV) and self-defeating humor (assessed by the Humor Style Questionnaire) in 284 participants. Then, the role of DT (assessed by the Torrance Tests of Creative Thinking, TTCT) in the relationship between humor and the related brain regions was examined in the participants (N = 280). The results showed that self-defeating humor was significantly positively associated with the regional GMV in the left orbital frontal cortex (OFC) and that DT had a moderating effect on this relationship. Among the individuals with higher DT, a strong positive correlation was observed between self-defeating humor and the OFC, but among individuals with lower DT, this correlation was weaker. These results reveal that the interaction between brain structures and DT plays an important role in humor, thus providing new evidence enhancing our understanding of the mechanism of humor.

Investigating the neural substrate variations between easy and challenging creative association tasks during product design within an fMRI scanner

In practice, individuals strive to develop highly original and valuable creative products within specific limitations. However, previous functional Magnetic Resonance Imaging (fMRI) studies focused on divergent-thinking tasks without considering the "valuableness" of an idea. Additionally, different types of creative tasks (e.g., the easier association vs. the harder association task) may engage distinct cognitive processes. This study aimed to investigate the underlying neural mechanisms associated with different types of creative thinking, specifically focusing on the generation of the most original and valuable creative product within an fMRI scanner. Twenty-one college students participated in a block design study. During each trial, participants were instructed to draw the most original and valuable product inspired by a given figure. The findings revealed that, in comparison to the harder association task, the easier association task led to broader activation across multiple brain regions. However, this broader activation resulted in inefficient thinking and poorer creative performance. Notably, the orbitofrontal cortex exhibited activation across various creativity tasks and displayed connectivity with several seed brain regions, highlighting the importance of decision-making when only one original and valuable product design is allowed. Furthermore, the complex functional connectivity observed between different brain networks reflects the intricate nature of creative thinking. To conclude, widespread activation of brain regions does not necessarily indicate superior creativity. Instead, optimal creative performance within constraints is achieved through an efficient utilization of association for generating innovative ideas, inhibition for suppressing unoriginal ideas, and decision-making to select the most creative idea.