Circumplex Models with Multivariate Time Series: An Idiographic Approach

The circumplex model posits a circular representation of affect and some personality traits. There is an increasing need to examine the viability of the circumplex model with multivariate time series data collected on the same individuals due to the development of new data collection methods such as smartphone applications and wearable sensors. Estimating the circumplex model with time series data is more complex than with cross-sectional data because scores at nearby time points tend to be correlated. We adapt Browne’s circumplex model to accommodate time series data. We illustrate the proposed method with an empirical data set of daily affect ratings of an individual over 70 days. We conducted a simulation study to explore the statistical properties of the proposed method. The results show that the method provides more satisfactory confidence intervals and test statistics than a method that treats time series data as if they were cross-sectional data.</p

Multiple Local Solutions and Geomin Rotation

<p>In exploratory factor analysis, factor rotation is conducted to improve model interpretability. A promising and increasingly popular factor rotation method is geomin rotation. Geomin rotation, however, frequently encounters multiple local solutions. We report a simulation study that explores the frequency of local solutions in geomin rotation and the implications of such phenomena. The findings include: (1) multiple local solutions exist for geomin rotation in a variety of situations; (2) ϵ = .01 provides satisfactory rotated factor loadings in most situations; (3) 100 random starts appear sufficient to examine the multiple solution phenomenon; and (4) a population global solution may correspond to a sample local solution rather than the sample global solution.</p

CSF Biomarkers and Its Associations with ¹⁸F-AV133 Cerebral VMAT2 Binding in Parkinson’s Disease—A Preliminary Report

<div><p>Objective</p><p>Cerebrospinal fluid (CSF) biomarkers, such as α-synuclein (α-syn), amyloid beta peptide 1–42 (Aβ_1–42), phosphorylated tau (181P) (p-tau), and total tau (t-tau), have long been associated with the development of Parkinson disease (PD) and other neurodegenerative diseases. In this investigation, we reported the assessment of CSF biomarkers and their correlations with vesicular monoamine transporter 2 (VMAT2) bindings measured with ¹⁸F-9-fluoropropyl-(+)-dihydrotetrabenazine (¹⁸F-AV133) that is being developed as a biomarker for PD. We test the hypothesis that monoaminergic degeneration was correlated with CSF biomarker levels in untreated PD patients.</p><p>Methods</p><p>The available online data from the Parkinson’s Progression Markers Initiative study (PPMI) project were collected and analyzed, which include demographic information, clinical evaluations, CSF biomarkers (α-syn, Aβ_1–42, p-tau, and t-tau), ¹⁸F-AV133 brain PET, and T1 weighted MRIs. Region of interest (ROI) and voxel-wise Pearson correlation between standardized uptake value ratio (SUVR) and CSF biomarkers were calculated.</p><p>Results</p><p>Our major findings are: 1) Compared with controls, CSF α-syn and tau levels decreased significantly in PD; 2) α-syn was closely correlated with Aβ_1–42 and tau in PD, especially in early-onset patients; and 3) hypothesis-driven ROI analysis found a significant negative correlation between CSF Aβ_1–42 levels and VMAT2 densities in post cingulate, left caudate, left anterior putamen, and left ventral striatum in PDs. CSF t-tau and p-tau levels were significantly negatively related to VMAT2 SUVRs in substantia nigra and left ventral striatum, respectively. Voxel-wise analysis showed that left caudate, parahippocampal gyrus, insula and temporal lobe were negatively correlated with Aβ_1–42. In addition, superior frontal gyrus and transverse temporal gyrus were negatively correlated with CSF p-tau levels.</p><p>Conclusion</p><p>These results suggest that monoaminergic degeneration in PD is correlated with CSF biomarkers associated with cognitive impairment in neurodegenerative diseases including Alzheimer’s disease. The association between loss of dopamine synaptic function and pathologic protein accumulations in PD indicates an important role of CSF biomarkers in PD development.</p></div

Comparisons of the clinical outcomes and CSF tau levels in PDs with possible cognitive deficit.

<p>There was a significant difference of the mean age among the patients of Parkinson’s disease with, or without cognitive decline (PD-D, or PD-ND) (60.90±9.52 <i>vs</i>. 64.24±9.44 yr, p = 0.004), which further proved the vital role aging plays in the cognitive decline in PD development. As we expected, the motor severity increased with the cognitive decline in the patients (22.10±8.92 <i>vs</i>. 24.37±9.51, p = 0.05). The t-tau and p-tau levels increased simultaneously with the cognitive deficit progression in PD. The p-tau and t-tau levels increased from 15.43±10.11 and 44.05±17.62 pg/ml in PD-ND, to 16.47±9.74 and 46.96±20.30 pg/ml in PD-D, though the difference did not reach significance (p>0.1).</p

Comparison of the clinical measurements and CSF biomarker levels between early-onset and late-onset PDs.

<p>Comparison of the clinical measurements and CSF biomarker levels between early-onset and late-onset PDs.</p

Representative ¹⁸F-AV133 SUVR images of PD patients with different CSF tau levels.

<p>A: a 60.7-y-old female with t-tau/p-tau of 23.8/6.5 pg/mL. B: a 58.9-y-old male with t-tau/p-tau of 29.8/13.9 pg/mL. The motor scale/MoCA score for the patient A and B were 10/30 and 35/25, respectively. ¹⁸F-AV133 ROI SUVRs of patient A and B were: caudate, 1.86 and 1.79; left putamen, 1.74 and 1.30; right putamen, 2.36 and 1.61; ventral striatum, 2.39 and 2.11; raphe nuclei, 1.50 and 1.73; and substantia nigra, 1.48 and 1.42, respectively.</p

Correlations of CSF α-syn, Aβ_1–42, t-tau, and p-tau levels in patients of Parkinson’s disease.

<p>Correlations among cerebrospinal fluid (CSF) α-syn (α-synuclein), amyloid beta 1–42 (Aβ_1–42), total tau (t-tau) and phosphorylated tau 181P (p-tau) in Parkinson disease (PD) participants evaluated at baseline (n = 409). A significant positive correlation was found between CSF levels of α-syn and Aβ _1–42 (A), and tau (B). Because interpretation of α-syn might be confounded by blood contamination of CSF samples, 78 subjects with Hgb levels above the 200 ng/ml were excluded from α-syn analysis. Lines indicate trends within each group as determined by linear regression.</p

Demographic characteristics and clinical outcomes of HCs and Parkinson’s disease patients with CSF indicators at baseline.

<p>Demographic characteristics and clinical outcomes of HCs and Parkinson’s disease patients with CSF indicators at baseline.</p

Linear correlation between CSF biomarkers and ¹⁸F-AV133 VMAT2 densities in Parkinson disease patients (n = 22).

<p>Typical linear plots showed that t-tau and p-tau levels were significantly correlated with ¹⁸F-AV133 SUVRs in the left caudate, left anterior putamen and left ventral striatum (A-C). ROI based analysis also showed linear correlations between CSF Aβ_1–42 levels and SUVRs in substantia nigra and left ventral striatum (D).</p

SPM map.

<p>Significant negative correlations between cerebral VMAT2 density and CSF Aβ_1–42 (A) and p-tau (B) levels normalized scores with adjustment for age and sex of the PD patients. Significant clusters are displayed with slices of MRI templates in axial, coronal and sagittal orientations. p-value < 0.001 at the voxel level for clusters>50 contiguous voxels (corrected for cluster volume).</p