The brain-derived neurotrophic factor (BDNF) gene Val66Met polymorphism affects memory performance in older adults

Objective: Memory impairment is an important contributor to the reduction in quality of life experienced by older adults, and genetic risk factors seem to contribute to variance in age-related cognitive decline. Brain-derived neurotrophic factor (BDNF) is an important nerve growth factor linked with development and neural plasticity. The Val66Met polymorphism in the BDNF gene has been associated with impaired episodic memory in adults, but whether this functional variant plays a role in cognitive aging remains unclear. The purpose of this study was to investigate the effects of the BDNF Val66Met polymorphism on memory performance in a sample of elderly adults. Methods: Eighty-seven subjects aged 4 55 years were recruited using a community-based convenience sampling strategy in Porto Alegre, Brazil. The logical memory subset of the Wechsler Memory Scale-Revised was used to assess immediate verbal recall (IVR), delayed verbal recall (DVR), and memory retention rate. Results: BDNF Met allele carriers had lower DVR scores (p = 0.004) and a decline in memory retention (p = 0.017) when compared to Val/Val homozygotes. However, we found no significant differences in IVR between the two groups (p = 0.088). Conclusion: These results support the hypothesis of the BDNF Val66Met polymorphism as a risk factor associated with cognitive impairment, corroborating previous findings in young and older adults

BDNF polymorphisms are linked to poorer working memory performance, reduced cerebellar and hippocampal volumes and differences in prefrontal cortex in a Swedish elderly population

BACKGROUND: Brain-derived neurotrophic factor (BDNF) links learning, memory and cognitive decline in elderly, but evidence linking BDNF allele variation, cognition and brain structural differences is lacking. METHODS: 367 elderly Swedish men (n = 181) and women (n = 186) from Prospective Investigation of the Vasculature in Uppsala seniors (PIVUS) were genotyped and the BDNF functional rs6265 SNP was further examined in subjects who completed the Trail Making Task (TMT), verbal fluency task, and had a magnetic resonance imaging (MRI) scan. Voxel-based morphometry (VBM) examined brain structure, cognition and links with BDNF. RESULTS: The functional BDNF SNP (rs6265,) predicted better working memory performance on the TMT with positive association of the Met rs6265, and was linked with greater cerebellar, precuneus, left superior frontal gyrus and bilateral hippocampal volume, and reduced brainstem and bilateral posterior cingulate volumes. CONCLUSIONS: The functional BDNF polymorphism influences brain volume in regions associated with memory and regulation of sensorimotor control, with the Met rs6265 allele potentially being more beneficial to these functions in the elderly

Missense mutation of Brain Derived Neurotrophic Factor (BDNF) alters neurocognitive performance in patients with mild traumatic brain injury: a longitudinal study

The predictability of neurocognitive outcomes in patients with traumatic brain injury is not straightforward. The extent and nature of recovery in patients with mild traumatic brain injury (mTBI) are usually heterogeneous and not substantially explained by the commonly known demographic and injury-related prognostic factors despite having sustained similar injuries or injury severity. Hence, this study evaluated the effects and association of the Brain Derived Neurotrophic Factor (BDNF) missense mutations in relation to neurocognitive performance among patients with mTBI. 48 patients with mTBI were prospectively recruited and MRI scans of the brain were performed within an average 10.1 (SD 4.2) hours post trauma with assessment of their neuropsychological performance post full Glasgow Coma Scale (GCS) recovery. Neurocognitive assessments were repeated again at 6 months follow-up. The paired t-test, Cohen’s d effect size and repeated measure ANOVA were performed to delineate statistically significant differences between the groups [wildtype G allele (Val homozygotes) vs. minor A allele (Met carriers)] and their neuropsychological performance across the time point (T1 = baseline/ admission vs. T2 = 6th month follow-up). Minor A allele carriers in this study generally performed more poorly on neuropsychological testing in comparison wildtype G allele group at both time points. Significant mean differences were observed among the wildtype group in the domains of memory (M = -11.44, SD = 10.0, p = .01, d = 1.22), executive function (M = -11.56, SD = 11.7, p = .02, d = 1.05) and overall performance (M = -6.89 SD = 5.3, p = .00, d = 1.39), while the minor A allele carriers showed significant mean differences in the domains of attention (M = -11.0, SD = 13.1, p = .00, d = .86) and overall cognitive performance (M = -5.25, SD = 8.1, p = .01, d = .66).The minor A allele carriers in comparison to the wildtype G allele group, showed considerably lower scores at admission and remained impaired in most domains across the timepoints, although delayed signs of recovery were noted to be significant in the domains attention and overall cognition. In conclusion, the current study has demonstrated the role of the BDNF rs6265 Val66Met polymorphism in influencing specific neurocognitive outcomes in patients with mTBI. Findings were more detrimentally profound among Met allele carriers

BDNF Val66Met polymorphism interacts with sleep consolidation to predict ability to create new declarative memories

It is hypothesized that a fundamental function of sleep is to restore an individual's day-to-day ability to learn and to constantly adapt to a changing environment through brain plasticity. Brain-derived neurotrophic factor (BDNF) is among the key regulators that shape brain plasticity. However, advancing age and carrying the BDNF Met allele were both identified as factors that potentially reduce BDNF secretion, brain plasticity, and memory. Here, we investigated the moderating role of BDNF polymorphism on sleep and next-morning learning ability in 107 nondemented individuals who were between 55 and 84 years of age. All subjects were tested with 1 night of in-laboratory polysomnography followed by a cognitive evaluation the next morning. We found that in subjects carrying the BDNF Val66Val polymorphism, consolidated sleep was associated with significantly better performance on hippocampus-dependent episodic memory tasks the next morning (β-values from 0.290 to 0.434, p ≤ 0.01). In subjects carrying at least one copy of the BDNF Met allele, a more consolidated sleep was not associated with better memory performance in most memory tests (β-values from -0.309 to -0.392, p values from 0.06 to 0.15). Strikingly, increased sleep consolidation was associated with poorer performance in learning a short story presented verbally in Met allele carriers (β = -0.585, p = 0.005). This study provides new evidence regarding the interacting roles of consolidated sleep and BDNF polymorphism in the ability to learn and stresses the importance of considering BDNF polymorphism when studying how sleep affects cognition

COMT and DRD2/ANKK-1 gene-gene interaction account for resetting of gamma neural oscillations to auditory stimulus-driven attention

Attention capture by potentially relevant environmental stimuli is critical for human survival, yet it varies considerably among individuals. A large series of studies has suggested that attention capture may depend on the cognitive balance between maintenance and manipulation of mental representations and the flexible switch between goal-directed representations and potentially relevant stimuli outside the focus of attention; a balance that seems modulated by a prefrontostriatal dopamine pathway. Here, we examined inter-individual differences in the cognitive control of attention through studying the effects of two single nucleotide polymorphisms regulating dopamine at the prefrontal cortex and the striatum (i.e., COMTMet108/158Val and ANKK1/DRD2TaqIA) on stimulus-driven attention capture. Healthy adult participants (N = 40) were assigned to different groups according to the combination of the polymorphisms COMTMet108/158Val and ANKK1/DRD2TaqIA, and were instructed to perform on a well-established distraction protocol. Performance in individuals with a balance between prefrontal dopamine display and striatal receptor density was slowed down by the occurrence of unexpected distracting events, while those with a rather unbalanced dopamine activity were able maintain task performance with no time delay, yet at the expense of a slightly lower accuracy. This advantage, associated to their distinct genetic profiles, was paralleled by an electrophysiological mechanism of phase-resetting of gamma neural oscillation to the novel, distracting events. Taken together, the current results suggest that the epistatic interaction between COMTVal108/158Met and ANKK1/DRD2 TaqIa genetic polymorphisms lies at the basis of stimulus-driven attention capture

The Moderating Role of COMT and BDNF Polymorphisms on Transfer Effects Following Multi- and Single-Domain Cognitive Training Among Community-Dwelling Shanghainese Older Adults

Given the increase in research suggesting benefit following cognitive training in older adults, researchers have started to investigate the potential moderating role of genetic polymorphisms on transfer effects. The objective of this study was to evaluate the moderating effect of catechol-O-methyltransferase (COMT) and brain-derived neurotrophic factor (BDNF) polymorphisms on transfer effects following a single-domain or multi-domain training intervention in healthy community-dwelling older adults. A total of 104 men and women living in Shanghai were randomized to a multi-domain or a single-domain cognitive training (SDCT) group. COMT rs4818 SNP and the BDNF rs6265 SNP were analyzed from blood. At pre-intervention, post-intervention and at 6-month follow-up, participants completed the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), the Color-Word Stroop Test (CWST), the Trails Making Test (TMT) and the Visual Reasoning Test (VRT). COMT was found to moderate immediate memory transfer effects following single-domain training only, with G/- carriers displaying greater benefits than C/C carriers. BDNF was found to moderate attention and inhibition independent of the training, with Met/- carriers displaying better performance than Val/Val carriers. Overall, individualizing training methods with full consideration of genetic polymorphisms may promote the maximization of cognitive training benefits

Role of BDNF in the Ability of Exercise to Attenuate Dependence-Related Escalated Alcohol Drinking in C57BL/6J Mice

Alcohol use disorder (AUD) continues to be a burden to society. Currently, few efficacious treatments exist. In addition to behavioral therapy and support groups (e.g. Alcoholics Anonymous), there are only three FDA approved pharmacotherapies. The lack of treatment options for alcohol addiction denotes the need to discover and develop new strategies and pharmacological targets to improve abstinence, prevent relapse, and inhibit the development of alcohol addiction. Chronic alcohol exposure reduces brain-derived neurotrophic factor (BDNF) in the medial prefrontal cortex (mPFC). Reductions of BDNF in the mPFC drive alcohol-dependent drinking in mice and conversely, elevating BDNF in this region blocks alcohol dependence-related drinking. Therefore, enhancing TrkB (BDNF primary receptor) activity in the mPFC, by pharmacological activation or increased expression of BDNF via exercise, may provide a new treatment strategy for AUD. To engender alcohol dependence mice are exposed to repeated cycles of chronic intermittent ethanol (CIE) vapor, producing escalated alcohol drinking compared to Baseline and control (Air) mice. Additionally, deficits in Bdnf mRNA and protein are seen in the mPFC after CIE exposure. Exercise (wheel running) noninvasively induces BDNF expression in the dentate gyrus (DG) of rodents and in the blood of humans. This information led to the question of whether exercise could increase BDNF in the mPFC, reduce alcohol dependence-related drinking, and if this effect would occur through a BDNF-TrkB mediated mechanism. Studies tested the hypothesis that: Daily, limited (2-hr) voluntary wheel running would increase BDNF expression in the brain and through BDNF-TrkB signaling, attenuate CIE-induced escalated alcohol drinking. Following the Introduction, Chapter 2 demonstrates mice given limited access to a running wheel every day for several weeks, show increased Bdnf mRNA (qRT-PCR) and BDNF protein (ELISA) expression in the mPFC and DG. Building on these findings, Chapter 3 shows exercise attenuates CIE induced escalated alcohol drinking and mitigates reductions of BDNF mRNA in the mPFC caused by chronic alcohol exposure. Finally, in Chapter 4, using pharmacological inhibition of TrkB receptors, the ability of exercise to attenuate escalated alcohol intake is prevented. Taken together this study demonstrates exercise attenuates escalated alcohol intake in a model of dependence via BDNF-TrkB mediated signaling

Strategies that shape perception

In recent years there has been an increased focus on individual differences. Such differences have been observed in conditions where people display performance deficits, such as developmental prosopagnosia (McConachie, 1976), in conditions where subjects demonstrate enhanced skills, such as synesthesia (Terhune et al., 2013), as well as in neurotypical individuals, for instance, in the form of subtle individual differences in visual perception (Zelazny & Sørensen, 2020). Our interaction with the environment during brain maturation shapes how perceptual strategies are formed and prioritized. One of the principal tasks for the brain during this stage is to establish templates and context frames in long-term memory. These templates and context frames serve as the basis for various perceptual strategies used to interpret sensory information. Over time, these templates are updated in light of both sensory evidence and the perceptual strategies that have proven advantageous. Successful strategies thus have a greater likelihood of being used in the future, hence shaping our perceptual strategic preferences. In the well-known case of AB, who was afflicted with developmental prosopagnosia (McConachie, 1976), there is evidence to suggest that she prioritized peoples’ clothing as a strategy for recognition over the more common one of relying on facial features. Similarly, grapheme-color synesthesia may develop as a strategy for learning the alphabet. Here, a common strategy may be to associate the abstract letter shapes with previously established color categories in an attempt to aid letter recognition (Brogaard & Sørensen, in press). If this particular strategy is sufficiently prioritized, this may result in grapheme-color synesthesia (cf. Mannix & Sørensen, in press). Here, we argue that individual variability in visual perception reflects differences in perceptual strategies. An interesting consequence of this thesis is that perceptual experience is likely to vary considerably more across individuals than hitherto assumed