Muriah D Wheelock¹, Patricia Mansfield², Jeremy F Strain¹, Beau M Ances¹, Oliver Preische³, John C Morris¹, Randall J Bateman¹, Mathias Jucker³, Tammie L.S. Benzinger¹, Adam T Eggebrecht¹, and Brian A Gordon^1
1Washington University in St. Louis, St. Louis, MO, United States, ²St. Louis University, St. Louis, MO, United States, ³University of Tubingen, Tubingen, Germany

Research suggests that serum neurofilament light (NfL), an indirect measure of neuronal cell death, is associated with volumetric and white matter changes, and is predictive of cognitive decline in Alzheimer disease (AD). We report that NfL is associated with default mode network (DMN) functional connectivity as well as DMN connectivity with control networks. DMN connectivity with control networks is additionally associated with concurrent cognition. Hierarchical regression demonstrates NfL, DMN, and Aβ-amyloid each contribute to predicting cognition. These findings suggest NfL is an indirect marker of functional network degeneration and both NfL and DMN connectivity are distinct biomarkers of AD progression.

Lingxiao Cao¹, Hailong Li¹, Jing Liu¹, Xue Li², Suming Zhang¹, Xinyu Hu¹, Qiyong Gong¹, and Xiaoqi Huang^1
1Huaxi MR Research Center (HMRRC), Functional and molecular imaging Key Laboratory of Sichuan Province, Department of Radiology, West China Hospital, Sichuan University, Chengdu, China, ²Sichuan University, Chengdu, China

Using connectivity-based parcellation technique, we segmented thalamus into two distinct subdivisions comprising superior thalamus and inferior thalamus based on their similarity in resting-state functional connectivity properties. We then compared the functional connectivity profiles of each thalamic subdivisions between the obsessive-compulsive disorder (OCD) patients and healthy control (HC), and revealed the disturbances of the superior/inferior thalamo-cortical and inferior thalamo-cerebellar circuitry in OCD patients. These findings suggested that thalamus subdivisions play different role in motor, cognitive, affective processes in OCD, which may underlie the pathophysiology of the disorder.

Lincoln Kartchner¹, Linda Chang², Thomas Ernst², Huajun Liang², Yuangi Shang², and Peiying Liu^1
1Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States, ²Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, MD, United States

Human immunodeficiency virus (HIV) infection is associated with neurodegeneration, but its effect on cerebrovascular function is not well understood.  In a cohort of 160 participants, we investigated the effects of HIV and smoking on cerebrovascular reactivity (CVR) measured with standard resting-state blood oxygenation level dependent (BOLD)-fMRI. Across four participant groups (HIV+/HIV- x smokers/nonsmokers), both HIV-infection and smoking status altered CVR, but their effects were different across brain regions. Furthermore, lower nadir CD4 predicted lower thalamus CVR.

Xiaole Zhong¹ and J. Jean Chen^1,2
1Rotman Research Institute, Baycrest Health Sciences, Toronto, ON, Canada, ²Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada

Frequency features of the resting-state functional magnetic resonance imaging (rs-fMRI) signal can be crucial metrics that reveal patterns of brain aging. However, how the frequency shift during brain aging is still unclear. In this study, we examined the peak frequency and standard deviation of the rs-fMRI signal in healthy aging adults, divided into (0-0.1 Hz) and (0.1-0.3 Hz) bands. We found that in older adults, rs-fMRI fluctuation amplitude is lower but fluctuation frequency is higher in older adults, and these effects depend on the fMRI frequency range.

Faezeh Vedaei^1,2, Mahdi Alizadeh¹, Sara Thalheimer¹, Victor Romo³, Feroze Mohamed⁴, and Chengyuan Wu^1
1Department of Neurosurgery, Thomas Jefferson University, Philadelphia, PA, United States, ²Department of Bioengineering, Temple University, Philadelphia, PA, United States, ³Department of Anesthesiology, Thomas Jefferson University, Philadelphia, PA, United States, ⁴Department of Radiology, Thomas Jefferson University, Philadelphia, PA, United States

Resting-state fMRI suffers from poor test-retest reliability because of between-subject and within-subject variability. Scan duration is one the main factors affects the reliability of rs-fMRI studies. We showed that under anesthesia, the time needed to optimize ICC of rs-fMRI metrics including ALFF, fALFF, functional connectivity, and ReHo is lower compare with awake state. The optimum scan duration that satisfies good reliability is 14-20 min and 8-17 min in awake and under anesthesia, respectively. Also, variability of ICCs is lower under anesthesia than in awake.

Ying Xiong¹, Qiang Zhang², and Wenzhen Zhu^1
1Radiology, Tongji Hospital Tongji Medical College Huazhong University of Science and Technology, Wuhan, China, ²Neurology, Tongji Hospital Tongji Medical College Huazhong University of Science and Technology, Wuhan, China

The T2DM patients with cognitive impairment showed altered global efficiency(Eg), local efficiency(Eloc), clustering-coefficient(Cp), shortest-path-length(Lp) as well as nodal efficiencies in both structural and functional networks, compared to those with normal cognition and healthy controls. Some network metrics were correlated with neuropsychological assessments and disease severity. The disrupted topological organization of structural and functional connectomes (measured by Eg, Eloc, Cp and Lp) were found in T2DM with cognitive impairment, while these topological properties in T2DM with normal cognition were preserved equally to controls. The structural and functional connectomes research shows potential feasibility in characterizing intrinsic alterations of diabetic encephalopathy.

Christopher R. Kouyoumdjian¹, Kayley Marchena^2,3, Masud Hussain³, and Bradley J. MacIntosh^2,3
1University of Toronto, Scarborough, ON, Canada, ²Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada, ³Sunnybrook Research Institute, Toronto, ON, Canada

Glycated haemoglobin and body mass index (BMI) are implicated in neurodegeneration and diabetes. Diabetes-related changes in T2* estimates and fractional amplitude of low frequency fluctuations (fALFFs) are less understood. We investigated these neuroimaging estimates within the thalamic nuclei, hippocampi, and caudate nuclei of the UK Biobank-derived pre-diabetes and diabetes adult groups. Multiple regression analyses elucidated BMI as the robust predictor of hippocampal T2* estimates in both subgroups. These metrics extracted from two pulse sequences were helpful in understanding the brain and BMI associations, which is important in the assessment of diabetes and pre-diabetes as a risk factor for neurodegenerative disorders.

Lekai Luo¹, Qian Li¹, Wanfang You¹, Yuxia Wang¹, Yanchun Yang², Qiyong Gong¹, and Fei Li^1
1Huaxi MR Research Centre (HMRRC), Department of Radiology, West China Hospital of Sichuan University, Chengdu, China, ²Psychiatry, West China Hospital of Sichuan University, Chengdu, China

Dynamic functional connectivity (dFC) and dynamic topological analyses were used to investigate the whole brain resting-state dynamic property abnormalities in patients with obsessive-compulsive disorder (OCD). Our results provide evidence of clinically relevant aberrant dynamic brain activity in OCD. Increased functional segregation among networks and impaired functional flexibility in connections among brain regions in default mode network (DMN) and salience network (SAN) may play important roles in the neuropathology of OCD.

Russell W. Chan^1,2, Ji Won Bang², Vivek Trivedi², Peiying Liu³, Gadi Wollstein², Joel S. Schuman², and Kevin C. Chan^1,2,4
1Neuroscience Institue, New York University Grossman School of Medicine, New York, NY, United States, ²Department of Ophthalmology, New York University Grossman School of Medicine, New York, NY, United States, ³Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States, ⁴Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States

Cerebrovascular reactivity (CVR) is the response of cerebral blood vessels to vasoactive stimuli. Dampened CVR can precede and contribute to neuropathology. However, CVR assessments in glaucoma patients have been lacking at the whole-brain scale. Here, we applied relative CVR (rCVR) mapping using resting-state fMRI to investigate vascular reserve changes in glaucoma patients. Our results show that visual cortical rCVR decreases with severity and is coupled with clinical ophthalmic assessments. Interestingly, rCVR in both basal forebrain and hippocampus increase with severity indicating their involvements in glaucoma. Together, resting-state fMRI derived rCVR can potentially be used for studying, diagnosing and monitoring glaucoma.

Siqi Cai^1,2, Zhifeng Shi³, Yuchao Liang⁴, Chunxiang Jiang^1,2, Shihui Zhou^1,2, and Lijuan Zhang*^1
1Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, ²University of Chinese Academy of Sciences, Beijing, China, ³Huashan Hospital of Fudan University, Shanghai, China, ⁴Neurosurgery, Beijing Tiantan Hospital of Capital Medical University, Beijing, China

This study investigated the impact of cerebral glioma on the dynamic properties of functional connectivity (dFC). Cerebral gliomas induce alteration in dFC featuring more frequent strengthened connectivity and state transition between strong and sparse functional connectivity, indicating an extensive disturbance of functional segregation. As alterations in the dFC were reported to be associated with the progression of brain diseases, dFC variation induced by glioma may entail additional information to interpret the clinical profiles that are not ascribed to the lesion topology and serve as a new biomarker for the tumor characterization of glioma.