Parkinson’s disease (PD) chronic L-Dopa treatment often triggers motor complications, such as L-Dopa-induced dyskinesias (LID). LID are reported to be associated with abnormal glutamatergic activity between the striatum and primary motor cortex (M1), resulting in M1 hyperactivation. Beneficial noninvasive brain stimulation (NIBS) paradigms were reported to normalize glutamatergic activity. The objective of the present study was thus to set up a NIBS paradigm in parkinsonian monkeys to investigate motor behavior under basal conditions and with L-Dopa treatment-inducing dyskinesias.

Motor behavior was investigated in five 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) dyskinetic female Macaca fascicularis monkey models of PD, allowing us to monitor the administration of NIBS and drugs. NIBS used were inhibitory protocols, that is, cathodal transcranial direct current stimulation (c-tDCS) and continuous theta-burst stimulation (cTBS). A procedure of three weeks was developed to progressively acclimate animals to the experimental conditions, equipment and noise of c-tDCS and cTBS before stimulating them with either vehicle or L-Dopa.

One session of c-tDCS with L-Dopa yielded no effect, whereas five sessions briefly reduced LID but decreased the duration of L-Dopa anti-PD effects. cTBS alone improved (decreased) parkinsonian scores as compared to sham stimulation or vehicle alone. Two sessions of cTBS with L-Dopa decreased LID without affecting L-Dopa anti-PD effects.

This is the first study testing c-tDCS and cTBS on the motor behavior of MPTP dyskinetic monkeys. As compared to medicated patients, MPTP monkeys offer the opportunity to evaluate NIBS after-effects in drug-free and LID conditions, which are critical in the search for new PD treatment.

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) improves motor outcomes in Parkinson’s disease (PD) but may have adverse long-term effects on specific cognitive domains. The aim of this study was to investigate the association between total electrical energy (TEED) delivered by DBS and postoperative changes in verbal fluency.

Seventeen PD patients undergoing bilateral STN-DBS were assessed with the Alternate Verbal Fluency Battery (AVFB), which includes phonemic (PVF), semantic (SVF), and alternate verbal fluency (AVF) tests, before surgery (T0) and after 6 (T1) and 12 months (T2). Bilateral TEED and average TEEDM were recorded at T1 and T2. For each AVFB measurement, changes from T0 to T1 (Δ-01) and from T0 to T2 (Δ-02) were calculated.

At T1, PVF (p = 0.007) and SVF scores (p = 0.003) decreased significantly. TEED measures at T1 and T2 were unrelated to Δ-01 and Δ-02 scores, respectively. However, an inverse, marginally significant association was detected between the TEEDM and Δ-01 scores for the AVF (p = 0.041, against an αadjusted = 0.025).

In conclusion, the present reports provide preliminary evidence that TEED may not be responsible or only slightly responsible for the decline in VF performance after STN-DBS in PD.

This systematic review primarily aims to identify the optimal physiotherapeutic intervention to improve hand dexterity in Parkinson’s Disease (PD) patients. The secondary objectives were to identify the hand dexterity physiotherapeutic interventions available for PD patients, and to determine the quality of these interventions.

Eight electronic databases were systematically searched to identify relevant randomized controlled trial full-text articles using the established search strategy. The primary outcomes of interest were measurements for hand dexterity and activities of daily living (ADL).

A total of 11 studies comprising 647 participants with PD were included. Most studies had a high risk of performance bias and an unclear risk of selection bias. The intervention training period ranged from a single session to 12 weeks. Compared to their respective control group, eight out of 11 studies revealed significant results in hand dexterity, two out of three studies reported positive effects on ADL, four of seven studies showed significant improvements in upper limb motor performance, and two studies perceived positive benefits in terms of overall quality of life. Five out of 11 studies that recorded the occurrence of adverse events reported no adverse events post-intervention.

The dearth of evidence made it difficult to support any one intervention as the best intervention when compared to the other PD treatments in upper limb rehabilitation. Regardless, a home-based dexterity rehabilitation programme is still a promising approach to enhance dexterity-related functional abilities.

We aimed to evaluate the effect of yoga on motor and non-motor symptoms and cortical excitability in patients with Parkinson’s disease (PD).

We prospectively evaluated 17 patients with PD at baseline, after one month of conventional care, and after one month of supervised yoga sessions. The motor and non-motor symptoms were evaluated using the Unified Parkinson’s disease Rating Scale (motor part III), Hoehn and Yahr stage, Montreal Cognitive Assessment, Hamilton depression rating scale, Hamilton anxiety rating scale, non-motor symptoms questionnaire and World Health Organization quality of life questionnaire. Transcranial magnetic stimulation was used to record resting motor threshold, central motor conduction time, ipsilateral silent period (iSP), contralateral silent period (cSP), short interval intracortical inhibition (SICI), and intracortical facilitation.

The mean age of the patients was 55.5 ± 10.8 years, with a mean duration of illness of 4.0 ± 2.5 years. The postural stability of the patients significantly improved following yoga (0.59 ± 0.5 to 0.18 ± 0.4, p = 0.039). There was a significant reduction in the cSP from baseline (138.07 ± 27.5 ms) to 4 weeks of yoga therapy (116.94 ± 18.2 ms, p = 0.004). In addition, a significant reduction in SICI was observed after four weeks of yoga therapy (0.22 ± 0.10) to (0.46 ± 0.23), p = 0.004).

Yoga intervention can significantly improve postural stability in patients with PD. A significant reduction of cSP and SICI suggests a reduction in GABAergic neurotransmission following yoga therapy that may underlie the improvement observed in postural stability.

CTRI/2019/02/017564

Impaired motor and cognitive function can make travel cumbersome for People with Parkinson’s disease (PwPD). Over 50% of PwPD cared for at the University of Arkansas for Medical Sciences (UAMS) Movement Disorders Clinic reside over 30 miles from Little Rock. Improving access to clinical care for PwPD is needed.

To explore the feasibility of remote clinic-to-clinic telehealth research visits for evaluation of multi-modal function in PwPD.

PwPD residing within 30 miles of a UAMS Regional health center were enrolled and clinic-to-clinic telehealth visits were performed. Motor and non-motor disease assessments were administered and quantified. Results were compared to participants who performed at-home telehealth visits using the same protocols during the height of the COVID pandemic.

Compared to the at-home telehealth visit group (n = 50), the participants from regional centers (n = 13) had similar age and disease duration, but greater disease severity with higher total Unified Parkinson’s disease rating scale scores (Z = −2.218, p = 0.027) and lower Montreal Cognitive Assessment scores (Z = −3.350, p < 0.001). Regional center participants had lower incomes (Pearson’s chi = 21.3, p < 0.001), higher costs to attend visits (Pearson’s chi = 16.1, p = 0.003), and lived in more socioeconomically disadvantaged neighborhoods (Z = −3.120, p = 0.002). Prior research participation was lower in the regional center group (Pearson’s chi = 4.5, p = 0.034) but both groups indicated interest in future research participation.

Regional center research visits in PwPD in medically underserved areas are feasible and could help improve access to care and research participation in these traditionally underrepresented populations.

Early-onset Parkinson’s disease (EOPD) refers to patients with Parkinson’s disease (PD) whose age at disease onset is less than 50 years. Literature on the non-motor symptoms (NMS) in these patients is very limited in the Indian context. We aimed to study the NMS in patients with EOPD and its impact on the quality of life (QoL).

We included 124 patients with EOPD with a mean age at disease onset between 21 and 45 years and 60 healthy controls (HC). NMS were assessed using validated scales, and the QoL domains were evaluated using the PD QoL–39 scale (PDQ-39).

The mean age at disease onset in EOPD patients was 37.33 ± 6.36 years. Majority of the patients were male (66.12%). The average disease duration was 6.62 ± 5.3 years. EOPD patients exhibited a significantly higher number of NMS per patient (7.97 ± 4.69) compared to HC (1.3 ± 1.39; p < 0.001). The most common NMS reported were urinary dysfunction, body pain, poor sleep quality, constipation, anxiety, depression, cognitive impairment, and REM sleep behavior disorder. The total NMS burden correlated with the QoL measures. Distinctive patterns of QoL subdomain involvement were identified, with sleep/fatigue, mood/cognition, and urinary dysfunction independently influencing QoL metrics.

Our study provides valuable insights into the NMS profile and its impact on QoL in patients with EOPD, addressing an important knowledge gap in the Indian context. By understanding the specific NMS and their influence on QoL, healthcare professionals can develop targeted interventions to address these symptoms and improve the overall QoL.

Parkinson’s disease (PD) is a neurodegenerative disorder affecting over 10 million people worldwide. PD is characterized by both motor (e.g., tremor, rigidity, and bradykinesia) and non-motor (including cognitive impairment and neuropsychiatric symptoms such as apathy, disinhibition, executive dysfunction) symptoms. Caregiver burden is prevalent in those providing care for patients with PD and can result in negative health complications. Past work shows associations between motor symptoms, cognitive impairment, neuropsychiatric symptoms, and caregiver burden in PD. However, their relative contributions are poorly understood. This study examined these relationships, hypothesizing that while motor symptoms, cognitive impairment, and neuropsychiatric symptoms would all affect caregiver burden, neuropsychiatric symptoms would predict burden above and beyond the contribution of the other factors

Participants were 42 people living with PD who were assessed at a hospital-based tertiary movement disorders specialty clinic for deep brain stimulation (DBS) candidacy evaluation with their caregiver. Motor exam was assessed by a PD specialist using the Unified Parkinson’s Disease Rating Scale (UPDRS). The Mini Mental State Examination (MMSE) assessed global cognition. Frontal Systems Behavior Scale (FrSBe) Family Form captured caregiver ratings of neuropsychiatric symptoms under 3 subscales: apathy, disinhibition, and executive dysfunction. The Multidimensional Caregiver Strain Index (MCSI) captured caregiver burden. Linear regression analyses examined relationships between caregiver burden (MCSI) and motor symptoms (UPDRS), cognitive impairment (MMSE), and neuropsychiatric symptoms (FrSBe).

Using linear regression analyses, cognitive impairment (R2=0.08, F(1,41)=4.42, p=0.04) and neuropsychiatric symptoms (R2=0.35, F(1, 41)=21.0, p<0.01) predicted caregiver burden but motor symptoms did not (R2=0.03, F(1,41)=1.30, p=0.26). Hierarchical linear regression revealed that neuropsychiatric symptoms predicted caregiver burden above and beyond the contribution of cognitive impairment (AR2=0.28, AF(1)=12.7, p=0.001), accounting for an additional 28% of the variance in caregiver burden. Follow-up linear regression to examine the relationships between caregiver burden and the FrSBe subscales indicated that apathy (p<0.001), versus disinhibition (p=0.16) and dysexecutive behaviors (p=0.80), was the driver of the significant relationship.

Consistent with our hypothesis, results revealed that cognitive impairment and neuropsychiatric symptoms (specifically apathy) were independent predictors of caregiver burden, with neuropsychiatric symptoms predicting caregiver burden above and beyond the contribution of cognitive impairment. Somewhat surprisingly, motor symptoms were not a predictor of caregiver burden contrary to some previous research, though findings are mixed. Results highlight the importance of assessing for neuropsychiatric symptoms in PD, which may be overlooked by care providers relative to motor or cognitive symptoms, but which appear stressful to caregivers. Future directions include reexamining results in a larger more heterogenous sample including people living with PD at different disease stages (i.e., everyone in the present sample had severe enough symptoms to be considering DBS). Cognitive measures of executive functioning (which are more specific to PD than measures of global cognition) should also be included in future works. Development of supportive caregiver interventions specifically targeting apathy in PD may be useful. Longitudinal designs would be helpful to reexamine relationships following DBS surgery, as there are some reports of increased neuropsychiatric symptoms following the procedure.

Laterality of motor symptom onset in Parkinson’s disease (PD) is well-known and under-appreciated. It is still unclear though if this laterality might have an influence on other symptoms. Specifically, REM sleep behavior disorder has been shown to be a factor that has a high probability to be lined to PD. In this study we analyzed the longitudinal effect of REM symptomatology on brain lateralization in PD.

We used the baseline and 3-year visit data of 116 participants (67 without REM (PD-non-REM), 49 with REM (PD-REM)) aged 37-81 years from the Parkinson’s Progression Markers Initiative (PPMI) dataset. Statistical 3T MRI data (cortical thicknesses, areas, foldings of cortical Desikan atlas and volumes of subcortical regions) were obtained via FreeSurfer 7.1.1. Lateralization was computed using the formula: (left-right)/(lef +right). Mixed ANOVAs were performed on each region of interest.

Our findings showed an increased right asymmetry of the paracentral lobule area and of the pars orbitalis area and volume in PD-REM. There was a reduced right asymmetry of the parietal inferior volume at baseline in PD-REM, whereas REM symptomatology had a stable effect at the 3 years visit. At baseline, there was an increased left asymmetry of the thickness of the caudal anterior cingulate, pars orbitalis and pars triangularis regions in PD-REM. After 3 years, there was an increased right asymmetry in those regions. The precentral, frontal superior and transversal temporal gyri showed inverse results: an increased right asymmetry of the thickness at baseline and an increased left asymmetry after 3 years. Finally, REM symptomatology is associated with more significant increases of the left asymmetry of the frontal superior gyrus volume and of the right asymmetry of the supramarginal gyrus volume after 3 years than at baseline.

These results provide evidence of the modulating effect of the disease progression on the relationship between REM symptoms and brain lateralization in PD.

Apathy is a primary lack of motivation that is frequently reported in Parkinson’s disease (PD) and often misdiagnosed as depression. In PD, apathy worsens over time with motor symptom progression. Evidence over the past 15 years has documented that use of selective serotonin reuptake inhibitors (SSRIs) is associated with increased apathy in patients with depression, including individuals with PD. In PD, this appears to be related to downregulation of dopaminergic systems by serotonin. Despite increasing evidence, SSRIs continue to be heavily prescribed in individuals with PD— potentially worsening apathy and decreasing quality of life for these individuals. This study is an update, re-examining the relationship between apathy and the use of SSRIs and other antidepressants in a large cohort of individuals with PD.

Participants included a convenience sample of 387 nondemented individuals with idiopathic PD who were in their mid-60's (mean age=64.9+8.72 years), well-educated (mean=14.95+2.78 years), predominantly male (72.4%), non-Hispanic white (94.5%), and in mid-stage of disease severity (on medication Unified Parkinson Disease Rating Scale motor score=25.3+10.1). All scored above clinical cutoff for dementia on a cognitive screener (Dementia Rating Scale-2 (DRS) > 125). Medications, cognitive, mood, and clinical data were extracted from chart review. Depression and apathy were measured using the Beck Depression Inventory-II (BDI-Il) and the Apathy Scale (AS). Antidepressant medications were grouped into SSRIs, serotonin and norepinephrine reuptake inhibitors (SNRIs) and other. Analyses included bootstrapped Pearson’s correlations, Pearson’s chi-square, and linear regressions

Among 387 individuals with PD, 41.3% (N=160) were taking antidepressant medications. Of these 160, 61.3% were on SSRIs, 24.4% on SNRIs, and the remainder on other antidepressants. Approximately 36.9% of the 387 PD patients exceeded recommended clinical cutoffs for apathy (AS >14) and 23.5% for depression (BDI-II >14) (Starkstein et al., 1992; Beck et al., 1996). Individuals taking SSRIs (N=98, x2=5.14, p=0.023) or SNRIs (N=39; x2=5.43, p=0.020) were more likely to be clinically apathetic than those taking other depression medications (N=23; x2=1.28, p=0.26). Results of a multiple regression with age, education, disease duration, motor severity, DRS-2, BDI-II, and all psychotropic medications (anti-depressants, anti-anxiety, anti-psychotics) as independent variables explained 42.8% of the variance in total apathy scores (F[17,285]=12.550, p<0.001). SSRIs were the only medication to significantly predict greater AS scores (ß=0.110, p=0.020) in this model. Less education (ß=-0.119, p=0.017) worse cognition (ß=-0.128, p=0.009), and greater depressive symptoms (ß=0.561, p<0.001) were also significant predictors of apathy.

These findings suggest that use of SSRIs, but not other antidepressants, is associated with greater apathy in PD. Given the interactive relationship between serotonin and dopamine, the current findings highlight the importance of considering apathy as a potential adverse effect when determining which anti-depressants to prescribe to individuals with PD. Similarly, switching a SSRI for an alternative anti-depressant in individuals with PD who are apathetic may be a potential treatment for apathy that needs further study. Longitudinal studies are also needed to elucidate the relationship of apathy and anti-depressant use over time, specifically to determine potential causality of this observed association. Funding: T32-NS082168

Autonomic dysfunction is an important non-motor symptom of Parkinson’s disease (PD), with point prevalence estimates of approximately 50-70%. Common presentations include cardiovascular dysregulation, gastrointestinal dysfunction, impaired thermoregulation, and sexual dysfunction. In the present study, we sought to examine whether autonomic symptoms would predict trajectories of change in depression and anxiety over a 5-year period in newly diagnosed individuals with PD. Given that alterations in autonomic nervous system functioning (e.g., reduced heart rate variability, lower autonomic arousal) are frequently observed in individuals who have anxiety and depression, as well as the negative influence these symptoms can have on quality of life/functioning, we predicted that greater autonomic symptoms would be related to increased mood symptoms over time.

Participants included 414 individuals from the Parkinson’s Progression Markers Initiative, a prospective study of newly diagnosed and untreated individuals with PD. The PD participants (mean age=61.6+9.7, mean education=15.6+3.0, 92.5% non-Hispanic White) were followed annually for up to five years. Self-reported autonomic symptoms were measured using the Scales for Outcomes in Parkinson’s Disease-Autonomic Dysfunction (SCOPA-AUT), which consists of a total score and 6 subdomain scores (gastrointestinal, urinary, cardiovascular, thermoregulatory, pupillomotor, sexual). Mood measures included the Geriatric Depression Scale (GDS) and State-Trait Anxiety Inventory (STAI). Motor severity was assessed using the Unified Parkinson’s Disease Rating Scale (UPDRS) Part III. Bootstrapped linear regressions were performed to evaluate the relationship between autonomic symptoms (subdomains) and mood using data from the last visit (year 5). For longitudinal analyses, bootstrapped multilevel modeling was used to examine a) changes in SCOPA-AUT total over time (unconditional growth model only) and b) the relationship between mood and SCOPA-AUT total score over time, controlling for age/sex and motor severity.

Autonomic symptoms explained 28.2% of the total variance in trait anxiety, with unique predictors of gastrointestinal (/3=.266, p<.001) and thermoregulatory (ß=.202, p=.004) symptoms. For depression, autonomic symptoms explained 27.9% of the total variance, with unique predictors of gastrointestinal (ß=.225, p=.012), thermoregulatory (ß=.178, p=.013), and cardiovascular (ß=.154, p=.012) symptoms. There was a gradual linear increase in total autonomic symptoms over time (b=0.86, p<.001). Greater total autonomic symptoms were associated with higher average trait anxiety (b=0.54, p<.001), slightly greater increase in trait anxiety over time (b=0.04, p<.05), and occasion-to-occasion fluctuations in trait anxiety (b=0.24, p<.001). Similarly, increased total autonomic symptoms were associated with higher average depressive symptoms (b=0.14, p<.001), minimally greater increase in depressive symptoms over time (b=0.01, p<.05), and occasion-to-occasion fluctuations in depressive symptoms (b=0.08, p<.001). Motor severity did not explain individual differences or trajectories of change in depression or trait anxiety.

Autonomic symptoms, particularly gastrointestinal, cardiovascular, and thermoregulatory dysfunction, were related to increased mood symptoms in PD patients and predicted increases in depression/anxiety over time. Our findings do not distinguish between two theoretical possibilities - whether autonomic symptoms lead to depression/anxiety versus involvement of co-occurring neural systems underlying both. Regardless, our study highlights the importance of treating autonomic dysfunction in early PD, and future work should incorporate additional measures of autonomic dysfunction (e.g., physiological probes).

Among individuals with Parkinson’s Disease (PD), visual hallucinations (VH) and mild cognitive impairment (MCI) are highly prevalent and often co-occur. Atrophy in similar brain regions [e.g. cholinergic basal forebrain (BF) nuclei] as well as specific cognitive difficulties (e.g. posterior-cortical abilities such as semantic fluency and visuoperception) have been associated with the presentation of each symptom type. While there are separate lines of evidence implicating BF volume in MCI and VH, no study to date has examined BF integrity in patients with concurrent MCI and VH symptomology. Furthermore, no prior studies examining BF integrity in MCI and VH have accounted for the potential confounding effects of dopaminergic medications which are known to exacerbate both symptom types. The aims of this study were to harmonize or bridge the two bodies of literature to determine the common neural substrate of PD-VH and PD-MCI (with an emphasis on the BF), to examine the confounding effects of dopaminergic pharmacotherapy, and to examine whether nondopaminergic “posterior” cognitive abilities differ between PD-MCI with versus without VH.

This study used a clinical chart review and MRI data to examine the associations between BF volume in a large group (n=296) of advanced PD patients (∼10 years disease duration) with and without each VH and MCI, covarying the effect of dopaminergic therapy. A two-way ANCOVA was run on total and regional BF volumes (i.e., total BF volume, and four nuclei including Ch4, Ch4p, Ch1-2, Ch3) using VH and MCI as independent variables, while covarying for dopaminergic medication. Using Mann-Whitney U tests, we compared the performance of individuals with MCI-VH versus that of individuals with MCI-noVH on tasks of semantic verbal fluency and of visuoperceptual skills (e.g., judgement of line orientation, object decision, and silhouettes).

There were two major findings: (1) atrophy of the Ch4 region in the BF was associated with MCI with VH while Ch1-2 was associated with MCI regardless of VH status, and (2) patients with both MCI and VH had poorer performance than individuals with MCI without VH on tasks measuring object recognition but not on tasks of visuospatial perception or semantic verbal fluency. These results remained stable regardless of whether or not dopaminergic medication was included in the model.

PD is a heterogeneous disease with different subtypes reflecting both dopaminergic and cholinergic dysfunction. Our findings suggest further dissociations within the cholinergic system. First, atrophy in Ch4, which projects to the cortical mantle, was preferentially associated with VH symptoms and object-based visuoperception deficits. This is consistent with proposals that VH are real-world manifestations of visuoperceptual deficits. Second, Ch1-2 atrophy, which projects primarily to the hippocampus, was associated with MCI regardless of VH. Future research will extend this work to other cognitive abilities such as memory, to analyses of brain networks that implicate the BF, and to the investigation of the relationship between anti-cholinergic medications and symptom presentation in PD.

Cognitive dysfunction is a common non-motor symptom of Parkinson’s disease (PD). Cognitive decline in PD is likely associated with dysfunction in the cholinergic system, which is affected by synuclein pathology early in the disease course. Recent studies have shown an association between reduced integrity of the basal forebrain (BF), which provides cholinergic innervation to most of cortex, and diminished cognitive functioning in PD. Specifically, those with PD and reduced cholinergic innervation also have higher rates of cognitive impairment. However, no study has directly investigated the relationship between basal forebrain integrity and cortical cholinergic levels. In the present study, we examined this relationship through measures of basal forebrain microstructural integrity and cholinergic nerve terminal density in cortical and subcortical gray matter.

Participants included 92 non-demented individuals with idiopathic PD (M:F=64:28; Age=67.0±7.1 yrs) who underwent structural MRI, diffusion MRI, and [18F] fluoroethoxybenzovesamicol (FEOBV) cholinergic PET imaging. We used a basal forebrain and region of interest defined by AssemblyNet, which uses ensembles of pretrained convolutional neural networks to create a full brain segmentation. Bilateral putamen from this atlas was also included as a control region. We measured microstructural integrity using free water fraction (FWF), a diffusion MRI-derived metric of extracellular water that associates with cellular density and neuroinflammation. For PET data, we computed the distribution volume ratio (DVR) by regions as defined by FreeSurfer. A factor analysis of DVR in all 88 FreeSurfer ROIs resulted in seven clusters of ROIs covering 1) widespread bilateral cortical regions (PC1); 2) subcortical and limbic regions (PC2); 3) bilateral cingulate regions (PC3); 4) left frontal regions (PC4); 5) right frontal and temporal regions (PC5); 6) cerebellum (PC6); and 7) bilateral entorhinal cortex and left temporal cortex (PC7). We performed seven separate regression analyses per ROI (controlling for age and disease duration) to evaluate the association between BF FWF and cholinergic levels in these regions. To determine if these ROIs showed unique associations with BF FWF, we then entered ROIs with a significant association with BF FWF as independent variables in a stepwise regression with forward selection with BF FWF as the dependent variable.

BF FWF was significantly and negatively associated with cholinergic levels in PC1 (AR2=.042, ß=-0.208, p=.04), PC3 (AR2=.044, ß=-0.206, p=.03), PC4 (AR2=.056, ß=-0.239, p=.02), and PC7 (ß=-0.215, p=.04). BF FWF trended towards a negative association with cholinergic levels in PC5 (AR2=.045, ß=-0.168, p=.09) and PC6 (ß=-0.188, p=.09). Putamen FWF did not significantly associate with any of the ROIs. In the follow-up stepwise regression, only PC4 contributed significantly to the overall model (AR2=.061, ß=-0.261, p=.02).

Basal forebrain FWF was inversely related to cholinergic levels in regions that are directly innervated by the basal forebrain (e.g., cingulate cortex, left frontal cortex, and bilateral entorhinal cortex). Future research should directly investigate the relationship between basal forebrain integrity, cortical cholinergic levels, and cognition. Separating the basal forebrain into specific nuclei would also be beneficial, as different nuclei may have differing associations with specific hemispheric cholinergic pathways and cognition.