FKBP5 polymorphisms influence pre‐learning stress‐induced alterations of learning and memory

FK506 binding protein 51 (FKBP5) is a co‐chaperone of heat shock protein 90 and significantly influences glucocorticoid receptor sensitivity. Single nucleotide polymorphisms (SNPs) in the FKBP5 gene are associated with altered hypothalamus–pituitary–adrenal (HPA) axis function, changes in the structure and function of several cognitive brain areas, and increased susceptibility to post‐traumatic stress disorder, major depression, bipolar disorder and suicidal events. The mechanisms underlying these associations are largely unknown, but it has been speculated that the influence of these SNPs on emotional memory systems may play a role. In the present study, 112 participants were exposed to the socially evaluated cold pressor test (stress) or control (no stress) conditions immediately prior to learning a list of 42 words. Participant memory was assessed immediately after learning (free recall) and 24 h later (free recall and recognition). Participants provided a saliva sample that enabled the genotyping of three FKBP5 polymorphisms: rs1360780, rs3800373 and rs9296158. Results showed that stress impaired immediate recall in risk allele carriers. More importantly, stress enhanced long‐term recall and recognition memory in non‐carriers of the risk alleles, effects that were completely absent in risk allele carriers. Follow‐up analyses revealed that memory performance was correlated with salivary cortisol levels in non‐carriers, but not in carriers. These findings suggest that FKBP5 risk allele carriers may possess a sensitized stress response system, perhaps specifically for stress‐induced changes in corticosteroid levels, which might aid our understanding of how SNPs in the FKBP5 gene confer increased risk for stress‐related psychological disorders and their related phenotypes.     

Precuneus degeneration in nondemented elderly individuals with APOE ɛ4: Evidence from structural and functional MRI analyses

Neurodegenerative diseases such as Alzheimer's disease (AD) have been recognized to exhibit disease‐specific brain vulnerability patterns. Apolipoprotein E (APOE ) ?4 allele imparts a high genetic risk of developing AD. Whether the APOE ?4 allele damages the brain when cognitive functions are still intact is important to understand, especially for possible early detection and intervention. This study aimed to examine the selective degeneration pattern associated with the APOE ?4 allele in the brains of cognitively normal elderly subjects. We enrolled 35 cognitively healthy ?4 carriers and 40 non‐carriers (53 to 81 years old) to evaluate group differences in cortical thickness and brain activation during a memory‐encoding task. We also assessed the functional connectivity of the brain regions with both structural and functional damages. The results from the neuropsychological tests showed that the performances of ?4 carriers and non‐carriers were comparable. Primarily, we found that the precuneus exhibited thinner cortical thickness and decreased deactivation during memory encoding. Furthermore, the connectivity analyses show that carriers exhibited damaged connectivity of the precuneus to several regions in the default mode network and the attention/executive control network. Our study reveals the degeneration pattern of the ?4 allele, which could be used as a potential biomarker for early detection for possible interventions and treatments. Hum Brain Mapp 38:271–282, 2017 . © 2016 Wiley Periodicals, Inc.     

Motor timing intraindividual variability in amnestic mild cognitive impairment and cognitively intact elders at genetic risk for Alzheimer’s disease

Introduction: Intraindividual variability (IIV) in motor performance has been shown to predict future cognitive decline. The apolipoprotein E-epsilon 4 (APOE-ε4) allele is also a well-established risk factor for memory decline. Here, we present novel findings examining the influence of the APOE-ε4 allele on the performance of asymptomatic healthy elders in comparison to individuals with amnestic MCI (aMCI) on a fine motor synchronization, paced finger-tapping task (PFTT).

Method: Two Alzheimer’s disease (AD) risk groups, individuals with aMCI (n = 24) and cognitively intact APOE-ε4 carriers (n = 41), and a control group consisting of cognitively intact APOE-ε4 noncarriers (n = 65) completed the Rey Auditory Verbal Learning Test and the PFTT, which requires index finger tapping in synchrony with a visual stimulus (interstimulus interval = 333 ms).

Results: Motor timing IIV, as reflected by the standard deviation of the intertap interval (ITI), was greater in the aMCI group than in the two groups of cognitively intact elders; in contrast, all three groups had statistically equivalent mean ITI. No significant IIV differences were observed between the asymptomatic APOE-ε4 carriers and noncarriers. Poorer episodic memory performance was associated with greater IIV, particularly in the aMCI group.

Conclusions: Results suggest that increased IIV on a fine motor synchronization task is apparent in aMCI. This IIV measure was not sensitive in discriminating older asymptomatic individuals at genetic risk for AD from those without such a genetic risk. In contrast, episodic memory performance, a well-established predictor of cognitive decline in preclinical AD, was able to distinguish between the two cognitively intact groups based on genetic risk.     

An obesity‐associated risk allele within the FTO gene affects human brain activity for areas important for emotion,impulse control and reward in response to food images

Understanding how genetics influences obesity, brain activity and eating behaviour will add important insight for developing strategies for weight‐loss treatment, as obesity may stem from different causes and as individual feeding behaviour may depend on genetic differences. To this end, we examined how an obesity risk allele for the FTO gene affects brain activity in response to food images of different caloric content via functional magnetic resonance imaging (fMRI). Thirty participants homozygous for the rs9939609 single nucleotide polymorphism were shown images of low‐ or high‐calorie food while brain activity was measured via fMRI. In a whole‐brain analysis, we found that people with the FTO risk allele genotype (AA) had increased activity compared with the non‐risk (TT) genotype in the posterior cingulate, cuneus, precuneus and putamen. Moreover, higher body mass index in the AA genotype was associated with reduced activity to food images in areas important for emotion (cingulate cortex), but also in areas important for impulse control (frontal gyri and lentiform nucleus). Lastly, we corroborate our findings with behavioural scales for the behavioural inhibition and activation systems. Our results suggest that the two genotypes are associated with differential neural processing of food images, which may influence weight status through diminished impulse control and reward processing.     

The impact of dystrobrevin‐binding protein 1 (DTNBP1) on neural correlates of episodic memory encoding and retrieval

Episodic memory impairment is a frequently reported symptom in schizophrenia. It has been shown to be associated with reduced neural activity of the hippocampus and prefrontal cortex. Given the high heritability of schizophrenia the question arises if alterations in brain activity are modulated by susceptibility genes and might be detectable in healthy risk allele carriers. The present study investigated the effect of the single nucleotide polymorphism (SNP) rs1018381 (P1578) of the dystrobrevin‐binding protein 1 (DTNBP1) on brain activity in 84 healthy subjects assessed by functional magnetic resonance imaging (fMRI) while they performed an episodic memory task comprising encoding and retrieval of faces. During encoding, the group of risk allele carriers (n = 29) showed enhanced neural activity in the left middle frontal gyrus (BA 11) and bilaterally in the cuneus (BA 17, 7) when compared with the nonrisk carrier group (n = 55). During retrieval, the risk group (compared to the non risk group) showed increased right hemispheric neural activity comprising the medial frontal gyrus (BA 9), inferior frontal gyrus (BA 9), and inferior parietal lobule (BA 40). Since there were no behavioral performance differences, increased neural activity of the risk group might be interpreted as a correlate of higher effort or differing cognitive strategies in order to compensate for a genetically determined slight cognitive deficit. Interestingly, the laterality of increased prefrontal activity is in accordance with the well known hemispheric encoding/retrieval asymmetry (HERA) model of episodic memory. Hum Brain Mapp, 2010. © 2009 Wiley‐Liss, Inc.     

Ipsilateral hippocampal atrophy is associated with long‐term memory dysfunction after ischemic stroke in young adults

Memory impairment after stroke in young adults is poorly understood. In elderly stroke survivors memory impairments and the concomitant loss of hippocampal volume are usually explained by coexisting neurodegenerative disease (e.g., amyloid pathology) in interaction with stroke. However, neurodegenerative disease, such as amyloid pathology, is generally absent at young age. Accumulating evidence suggests that infarction itself may cause secondary neurodegeneration in remote areas. Therefore, we investigated the relation between long‐term memory performance and hippocampal volume in young patients with first‐ever ischemic stroke. We studied all consecutive first‐ever ischemic stroke patients, aged 18–50 years, admitted to our academic hospital center between 1980 and 2010. Episodic memory of 173 patients was assessed using the Rey Auditory Verbal Learning Test and the Rey Complex Figure and compared with 87 stroke‐free controls. Hippocampal volume was determined using FSL‐FIRST, with manual correction. On average 10 years after stroke, patients had smaller ipsilateral hippocampal volumes compared with controls after left‐hemispheric stroke (5.4%) and right‐hemispheric stroke (7.7%), with most apparent memory dysfunctioning after left‐hemispheric stroke. A larger hemispheric stroke was associated with a smaller ipsilateral hippocampal volume (b=?0.003, P<0.0001). Longer follow‐up duration was associated with smaller ipsilateral hippocampal volume after left‐hemispheric stroke (b=?0.028 ml, P=0.002) and right‐hemispheric stroke (b=?0.015 ml, P=0.03). Our results suggest that infarction is associated with remote injury to the hippocampus, which may lower or expedite the threshold for cognitive impairment or even dementia later in life. Hum Brain Mapp 36:2432–2442, 2015. © 2015 Wiley Periodicals, Inc.     

Genetic polymorphisms of low density lipoprotein receptor can modify stroke presentation

Abstract

Low density lipoprotein is transcytosed across the blood–brain barrier mediated by low density lipoprotein receptor (LDLR). LDLR in the brain is mainly expressed on capillary endothelial cells and is therefore considered to be an important susceptibility gene in modifying the stroke presentation. A HapMap-based haplotype-tagging single nucleotide polymorphism association study was conducted in an isolated Taiwanese population. Two hundred and ninety-two unrelated patients with cerebral infarction, 76 patients with small vessel occlusion (SVO) disorder and 216 with non-SVO disorder were enrolled. For rs2738446, under the dominant model, the odds ratios (ORs) associated with the CC genotype were computed, with GG + CG carriers considered as the reference group. Homozygote CC carriers had a two-fold increased risk of SVO disorder [OR=2·0, 95% confidence interval (CI)=1·08–3.70, p=0·025). For rs2738450, under the dominant model, the ORs associated with the CC genotype were computed, with AA + AC carriers considered as the reference group. Homozygote CC carriers had a 1·85-fold increased risk of SVO disorder (OR=1·85, 95% CI=1·01–3.33, p=0·04). When analysing the association between the haplotype related to rs2738446 and rs2738450 and SVO disorder, the most common haplotype allele CC was used as the reference, and the GA haplotype allele was associated with a 48% decreased risk of SVO disorder (OR=0·52; 95% CI=0·29–0.93, p=0·029). Haplotype-based analysis of LDLR in Taiwanese patients with cerebral infarction provided preliminary evidence suggesting that genetic polymorphisms of LDLR can modify the stroke presentation.     

Cognitive endophenotypes in a family with bipolar disorder with a risk locus on chromosome 4

Objectives: We studied cognitive function in high‐risk relatives belonging to a single extended family showing linkage of bipolar disorder to a locus on chromosome 4. High‐risk relatives were defined as those that carried the risk haplotype of polymorphic markers, identified in a previous linkage study. This family provided a rare opportunity to characterize a neuropsychological endophenotype in a homogeneous sample of relatives with a common genetic risk factor. Methods: Fifteen family members carrying the risk haplotype (eight diagnosed with bipolar disorder or depression and seven with no psychiatric diagnosis), unrelated patients with bipolar disorder (n = 36) and major depressive disorder (n = 40), and healthy control subjects (n = 33) were administered the California Verbal Learning Test, Verbal Fluency Test, Hayling Sentence Completion Test, and Brixton Spatial Anticipation Test to assess verbal memory, verbal fluency, and executive function. Results: Compared with healthy controls, family members carrying the risk haplotype were impaired in indices of memory and executive function. There were no significant differences between unaffected and affected haplotype‐carrying family members in any cognitive measure. Pronounced deficits in the encoding stage of verbal memory and category verbal fluency were evident in individuals with the risk haplotype. Conclusions: Verbal learning and semantic verbal fluency impairments may represent a cognitive endophenotype for both bipolar disorder and major depression in relatives of bipolar disorder patients, as impairment was also present in high‐risk relatives who had not developed any affective disorder symptoms. These findings suggest that impairment in semantic organization may be linked to the genetic aetiology of bipolar disorder.     

Association of CETP polymorphisms with the risk of vascular dementia and white matter lesions

Cholesteryl ester transfer protein (CETP), a component of the high density lipoprotein (HDL), plays a central role in reverse cholesterol transport. We investigated the association of two putative functional CETP polymorphisms (C-629A and I405V) with the risk of vascular dementia (VD) and tested if this association is influenced by the presence of APOE4 allele. Our study included 163 VD patients (mean age: 74.25 ± 7.9 years) and 452 cognitively healthy probands (mean age: 70.81 ± 7.9 years). As a biological correlate, the association of CETP gene variants with white matter lesion (WML) load was investigated. Neither the C-629A (P = 0.169) nor the I405V (P = 0.840) polymorphism was associated with VD risk in the whole sample. However, in non-carriers of the APOE4 allele, homozygote carriers of the CETP C-629A A allele presented with an increased risk of VD (P = 0.01). Whereas in APOE4 carriers, no association of CETP polymorphisms with VD risk was detected. In addition, carriers of the CETP C-629A AA genotype presented with decreased WML load in the frontal brain (P = 0.009). Our results suggest that CETP gene polymorphisms might influence WML load and the risk of VD, the latter in non-carriers of the APOE4 allele.     

From gene to brain to behavior: schizophrenia‐associated variation in AMBRA1 alters impulsivity‐related traits

Recently, genome‐wide association between schizophrenia and an intronic variant in AMBRA1 (rs11819869) was reported. Additionally, in a reverse genetic approach in adult healthy subjects, risk allele carriers showed a higher medial prefrontal cortex blood oxygen level‐dependent (BOLD) response during a flanker task examining motor inhibition as an aspect of impulsivity. To test whether this finding can be expanded to further aspects of impulsivity, we analysed the effects of the rs11819869 genotype on impulsivity‐related traits on a behavioral, temperament and neural level in a large sample of healthy adolescents. We consider this reverse genetic approach specifically suited for use in a healthy adolescent sample, as these individuals comprise those who will eventually develop mental disorders in which impulsivity is implicated. Healthy adolescents from the IMAGEN study were included in the neuropsychological analysis (n = 848) and a functional magnetic resonance imaging (fMRI) task (n = 512). Various aspects of impulsivity were assessed using the Temperament and Character Inventory‐Revised, the Substance Use Risk Profile Scale, the Cambridge Cognition Neuropsychological Test Automated Battery, and the Stop Signal Task (SST) in the fMRI paradigm. On a behavioral level, increased delay aversion was observed in risk allele carriers. Furthermore, risk allele carriers showed a higher BOLD response in an orbito‐frontal target region during the SST, which declined to trend status after Family Wise Error correction. Our findings support the hypothesis that the schizophrenia‐related risk variant of rs11819869 is involved in various aspects of impulsivity, and that this involvement occurs on a behavioral as well as an imaging genetics level.     

Neuropsychological performance is related to current social and occupational functioning in veterans with posttraumatic stress disorder

Background: Several studies have reported deficits in both immediate and delayed recall of verbal memory in patients with posttraumatic stress disorder (PTSD). However, most of these studies had several methodological disadvantages. None of these studies assessed parameters related to social or occupational functioning. Methods: Fifty Dutch veterans of UN peacekeeping missions (25 with PTSD and 25 without PTSD) were assessed with a comprehensive neuropsychological test battery consisting of four subtests of the Wechsler Adult Intelligence Scale‐III, California Verbal‐Learning Test, and the Rey Auditory Verbal‐Learning Test. Veterans with PTSD were free of medication and substance abuse. Results: Veterans with PTSD had similar total intelligence quotient scores compared to controls, but displayed deficits of figural and logical memory. Veterans with PTSD also performed significantly lower on measures of learning and immediate and delayed verbal memory. Memory performance accurately predicted current social and occupational functioning. Conclusions: Deficits of memory performance were displayed in a sample of medication‐ and substance abuse‐free veterans with PTSD. Deficits in memory performance were not related to intelligence quotient, length of trauma exposure, or time since trauma exposure. This study showed that cognitive performance accurately predicted current social and occupational functioning in veterans with PTSD. Depression and Anxiety, 2009. © 2008 Wiley‐Liss, Inc.     

Neuropeptide S receptor gene variation and neural correlates of cognitive emotion regulation

The neuropeptide S (NPS) and its receptor NPSR have captured attention in the pathogenesis of anxiety disorders. Here, a functional polymorphism in the NPSR1 gene has been linked to deviant cortico–limbic interactions in response to negative stimuli. While healthy T allele carriers exhibited increased amygdala and prefrontal cortex activity, panic disorder patients carrying the T risk allele displayed hypofrontality possibly reflecting insufficient prefrontal inhibition of limbic reactivity. In order to study multi-level effects of genotype and anxiety, prefrontal cortex activity during an emotional n-back task was measured in 66 volunteers genotyped for the NPSR1 rs324981 A/T variant (AA homozygotes vs. T allele carriers) by means of functional near-infrared spectroscopy. For a high working memory load (3-back), T allele carriers showed a signal increase to negative pictures in the dorsolateral and medial prefrontal cortex while AA homozygotes displayed a signal decrease. Since groups did not differ on skin conductance level and behavioral parameters, this effect in the risk group in line with results from fMRI studies is speculated to represent an adaptive mechanism to compensate for presumably increased subcortical activity driven by an overactive NPS system. However, anxiety sensitivity correlated negatively with prefrontal activity in T allele carriers possibly suggesting a decompensation of the adaptive compensatory upregulation.     

C677T polymorphism of methylenetetrahydrofolate reductase gene affects plasma homocysteine level and is a genetic factor of late-onset Alzheimer's disease

Background: Elevated plasma homocysteine levels are known as a risk for atherosclerotic vascular disease and venous thrombosis and have been shown as a risk for late‐onset Alzheimer's disease (LOAD). Method: To examine the effect of genetic factors predisposing to elevated plasma homocysteine levels on the occurrence of LOAD, we determined the genotype of a C677T polymorphism of methylenetetrahydrofolate reductase (MTHFR) gene and a variable number tandem repeat (VNTR) spanning exon 13–intron 13 boundary of cystathionine β‐synthase (CBS) gene in patients with LOAD and community‐based control subjects. Results: Logistic regression indicated that the MTHFR‐T allele was a risk for LOAD (P < 0.05), independently from apolipoprotein E‐?4 (APOE‐?4) allele. Kaplan–Meier tests showed that in APOE‐?4 non‐carriers, individuals with the MTHFR‐TT genotype have occurences of LOAD earlier than those with the MTHFR‐CC genotype (P < 0.05). Multiple regression analysis indicates that MTHFR‐T allele increases plasma homocysteine levels (P = 0.0002), while the number of X chromosomes decreases (P = 0.01). Plasma homocysteine level was not correlated with age, plasma albumin reflecting nutritional condition, and the dose of APOE‐?4 allele. The CBS‐20 VNTR allele showed the same trend to increase plasma homocysteine level as the MTHFR‐T allele, but a risk effect for LOAD was not evident. Conclusion: A genetic propensity for elevated plasma homocysteine levels, explained by the MTHFR‐T allele encoding defective enzymatic function, is involved in the development of LOAD, particularly in APOE‐?4 non‐carriers, and that homocysteine metabolism could be a preventive target to LOAD in the elderly.     

Influences of a DRD2 polymorphism on updating of long‐term memory representations and caudate BOLD activity: Magnification in aging

A number of genetic polymorphisms are related to individual differences in cognitive performance. Striatal dopamine (DA) functions, associated with cognitive performance, are linked to the TaqIA polymorphism of the DRD2/ANKK1 gene. In humans, presence of an A1 allele of the DRD2/ANKK1‐TaqIA polymorphism is related to reduced density of striatal DA D2 receptors. The resource‐modulation hypothesis assumes that aging‐related losses of neurochemical and structural brain resources modulate the extent to which genetic variations affect cognitive functioning. Here, we tested this hypothesis using functional MRI during long‐term memory (LTM) updating in younger and older carriers and noncarriers of the A1‐allele of the TaqIa polymorphism. We demonstrate that older A1‐carriers have worse memory performance, specifically during LTM updating, compared to noncarriers. Moreover, A1‐carriers exhibited less blood oxygen level‐dependent (BOLD) activation in left caudate nucleus, a region critical to updating. This effect was only seen in older adults, suggesting magnification of genetic effects on functional brain activity in aging. Further, a positive relationship between caudate BOLD activation and updating performance among non‐A1 carriers indicated that caudate activation was behaviorally relevant. These results demonstrate a link between the DRD2/ANKK1‐TaqIA polymorphism and neurocognitive deficits related to LTM updating, and provide novel evidence that this effect is magnified in aging. Hum Brain Mapp 36:1325–1334, 2015. © 2014 Wiley Periodicals, Inc.     

Cardiovascular fitness is associated with altered cortical glucose metabolism during working memory in ɛ4 carriers

BackgroundThe possibility that ɛ4 may modulate the effects of fitness in the brain remains controversial. The present exploratory FDG-PET study aimed to better understand the relationship among ɛ4, fitness, and cerebral metabolism in 18 healthy aged women (nine carriers, nine noncarriers) during working memory.MethodsParticipants were evaluated using maximal level of oxygen consumption, California Verbal Learning Test, and FDG-PET, which were collected at rest and during completion of the Sternberg working memory task.ResultsResting FDG-PET did not differ between carriers and noncarriers. Significant effects of fitness on FDG-PET during working memory were noted in the ɛ4 carriers only. High fit ɛ4 carriers had greater glucose uptake in the temporal lobe than the low fit ɛ4 carriers, but low fit ɛ4 carriers had greater glucose uptake in the frontal and parietal lobes.ConclusionsWe demonstrate that fitness differentially affects cerebral metabolism in ɛ4 carriers only, consistent with previous findings that the effects of fitness may be more pronounced in populations genetically at risk for cognitive decline.     

Association of cognitive performance with interleukin-6 receptor Asp358Ala polymorphism in healthy adults

Wechsler adult intelligence scale-revised was performed in 576 healthy adults to examine whether a functional polymorphism (Asp358Ala) of the IL-6 receptor (IL-6R) gene is associated with cognitive performance. Verbal intelligence quotient in Asp homozygotes was significantly higher compared to Ala carriers (P = 0.005). Compared to Ala carriers, Asp homozygotes performed better in the verbal subtests requiring long-term memory stores. Elevated IL-6 and soluble IL-6R levels in Ala carriers may have negative impact on acquiring verbal cognitive ability requiring long-term memory.     

A genome‐wide supported psychiatric risk variant in NCAN influences brain function and cognitive performance in healthy subjects

The A allele of the single nucleotide polymorphism (SNP) rs1064395 in the NCAN gene has recently been identified as a susceptibility factor for bipolar disorder and schizophrenia. NCAN encodes neurocan, a brain‐specific chondroitin sulfate proteoglycan that is thought to influence neuronal adhesion and migration. Several lines of research suggest an impact of NCAN on neurocognitive functioning. In the present study, we investigated the effects of rs1064395 genotype on neural processing and cognitive performance in healthy subjects. Brain activity was measured with functional magnetic resonance imaging (fMRI) during an overt semantic verbal fluency task in 110 healthy subjects who were genotyped for the NCAN SNP rs1064395. Participants additionally underwent comprehensive neuropsychological testing. Whole brain analyses revealed that NCAN risk status, defined as AA or AG genotype, was associated with a lack of task‐related deactivation in a large left lateral temporal cluster extending from the middle temporal gyrus to the temporal pole. Regarding neuropsychological measures, risk allele carriers demonstrated poorer immediate and delayed verbal memory performance when compared to subjects with GG genotype. Better verbal memory performance was significantly associated with greater deactivation of the left temporal cluster during the fMRI task in subjects with GG genotype. The current data demonstrate that common genetic variation in NCAN influences both neural processing and cognitive performance in healthy subjects. Our study provides new evidence for a specific genetic influence on human brain function. Hum Brain Mapp, 36:378–390, 2015. © 2014 Wiley Periodicals, Inc.     

Intact working memory in non‐manifesting LRRK2 carriers – an fMRI study

Cognitive impairments are prevalent in patients with Parkinson's disease. Mutations in the leucine‐rich repeat kinase 2 (LRRK2) gene are the most common cause of genetic Parkinsonism. Non‐manifesting carriers of the G2019S mutation in the LRRK2 gene were found to have lower executive functions as measured by the Stroop task. This exploratory study aimed to assess whether the cognitive impairment in non‐manifesting carriers is specific for executive functions or includes other cognitive domains such as working memory. We recruited 77 non‐manifesting first‐degree relatives of Parkinson's disease patients (38 carriers). A block‐design fMRI N‐back task, with 0‐back, 2‐back and 3‐back conditions, was used in order to assess working memory. Participants were well matched on the Montreal Cognitive Assessment, University of Pennsylvania Smell Identification Test, Unified Parkinson's Disease Rating Scale part III, digit span, age, gender and Beck Depression Inventory. The task achieved the overall expected effect in both groups with longer reaction times and lower accuracy rates with increasing task demands. However, no whole‐brain or region‐of‐interest between‐groups differences were found on any of the task conditions. These results indicate that non‐manifesting carriers of the G2019S mutation in the LRRK2 gene have a specific cognitive profile with executive functions, as assessed by the Stroop task, demonstrating significant impairment but with working memory, as assessed with the N‐back task, remaining relatively intact. These finding shed light on the pre‐motor cognitive changes in this unique ‘at risk’ population and should enable more focused cognitive assessments of these cohorts.     

Effect of rs1063843 in the CAMKK2 gene on the dorsolateral prefrontal cortex

Recently, a single nucleotide polymorphism (SNP) in the CAMKK2 gene (rs1063843) was found to be associated with lower expression of the gene in the dorsolateral prefrontal cortex (DLPFC) and with schizophrenia (SCZ) and deficits in working memory and executive function. However, the brain mechanism underlying this association is poorly understood. A functional magnetic resonance imaging (fMRI) study (N = 84 healthy volunteers) involving multiple cognitive tasks, including a Stroop task (to measure attentional executive control), an N‐back task (to measure working memory), and a delay discounting task (to measure decision making) to identify the brain regions affected by rs1063843 was performed. Across all three tasks, it was found that carriers of the risk allele consistently exhibited increased activation of the left DLPFC. In addition, the risk allele carriers also exhibited increased activation of the right DLPFC and the left cerebellum during the Stroop task and of the left caudate nucleus during the N‐back task. These findings helped to elucidate the role of CAMKK2 in cognitive functions and in the etiology of SCZ. Hum Brain Mapp 37:2398–2406, 2016. © 2016 Wiley Periodicals, Inc .