Anatomical correlates of the neuropsychiatric symptoms in Alzheimer's disease.

The current study aimed to assess the relationship between the neuropsychiatric symptoms in Alzheimer's disease (AD) and the regional grey matter (GM) volume using voxel based morphometry (VBM). Data of 85 AD patients, 208 subjects with mild cognitive impairment (MCI), and 131 healthy controls were selected from the Alzheimer's Disease Neuroimaging Initiative. Individual VBM models across the entire sample for each items of the Neuropsychiatric Inventory Questionnaire as variables of interest were specified with four nuisance covariates, including age, sex, total intracranial volume (TIV), and Mini-Mental State Examination (MMSE) score. Agitation was related to the GM atrophy in the left inferior frontal/insula and bilateral retrosplenial cortices. Aberrant motor behavior (AMB) was related to the GM reductions in the right basal ganglia. The VBM models were recalculated by specifying three nuisance covariates (age, sex, TIV), and by excluding voxels related to AD severity by applying a MMSE mask. This procedure confirmed the first results, and additionally revealed associations between depression and GM atrophy in the left middle frontal cortex, between agitation and the GM atrophy in the left middle frontal cortex, and between AMB and GM reduction in the right inferior frontal cortex. Hierarchical multiple regression analyses using extracted mean GM value in these additional regions confirmed these associations. Finally, VBM analyses within a subgroup (85 AD patients and 41 MCI converters) largely confirmed the results. Our results suggest that specific patterns of GM atrophy within AD related neurodegeneration predispose to certain neuropsychiatric symptoms, suggesting distinct neurobiological mechanisms.

Does excessive play of violent first-person-shooter-video-games dampen brain activity in response to emotional stimuli?

The present case-control study investigated the processing of emotional pictures in excessive first-person-shooter-video-players and control persons. All participants of the fMRI experiment were confronted with pictures from four categories including pleasant, unpleasant, neutral content and pictures from the first-person-shooter-video-game 'Counterstrike'. Compared to controls, gamers showed a significantly lower activation of the left lateral medial frontal lobe while processing negative emotions. Another interesting finding of the study represents the higher activation of frontal and temporal brain areas in gamers when processing screen-shots from the first-person-shooter-video-game 'Counterstrike'. Higher brain activity in the lateral prefrontal cortex could represent a protection mechanism against experiencing negative emotions by down-regulating limbic brain activity. Due to a frequent confrontation with violent scenes, the first-person-shooter-video-gamers might have habituated to the effects of unpleasant stimuli resulting in lower brain activation. Individual differences in brain activations of the contrast Counterstrike>neutral pictures potentially resemble the activation of action-scripts related to the video-game.

The BDNF Val66Met polymorphism affects amygdala activity in response to emotional stimuli: evidence from a genetic imaging study.

Mounting evidence shows that the brain derived neurotrophic factor (BDNF) plays a crucial role in synaptic plasticity. Due to its potential involvement in psychiatric diseases like depression and anxiety disorders BDNF lately became a major target in research. A functional variant of the BDNF gene--the BDNF Val66Met polymorphism--is of particular interest, because it influences the BDNF secretion which is followed by signaling at the TrkB receptor leading to dendritic growth of neurons. Findings from genetic association studies in humans yield heterogenous results with respect to the question of which allele represents a potential risk factor for an affective disorder. Although structural MRT studies revealed that the 66Met variant is associated with smaller hippocampi and could therefore present the risk allele, fMRI studies investigating the processing of emotion with respect to the BDNF Val66Met polymorphism are lacking. N=37 healthy female subjects participated in an fMRI experiment with an affective startle reflex paradigm. Carriers of the 66Met variant showed stronger amygdala activation in the right hemisphere in response to emotional stimuli compared to neutral stimuli. The results of this study add to growing literature, showing that it is the 66Met, which is associated with higher trait anxiety.