Supplementary Information
Supplementary Methods
Participants: recruitment, inclusion and exclusion criteria.
Fifty-two participants were recruited through local media outlets and mental health providers.
Subjects were excluded for a number of medical conditions that might confound study
interpretation as confirmed by medical history, laboratory testing, electrocardiogram and
physical exam. Patients were excluded for uncontrolled cardiovascular, endocrinologic,
hematologic, hepatic, renal, or neurologic disease, autoimmune conditions (i.e. rheumatoid
arthritis, inflammatory bowel disease, multiple sclerosis, lupus), chronic infection (i.e. HIV,
hepatitis B or C), history of liver abnormalities, or evidence of infection within one month of
screening that required antibiotic or antiviral therapy. Participants were also excluded for a
history of cancer, pregnancy or lactation; a history of schizophrenia (determined by SCID-IV); 1
active psychotic symptoms of any type; substance abuse and/or dependence within the past 6
months (determined by SCID-IV);1 an active eating disorder or obsessive compulsive disorder;
active suicidal ideation determined by a score of 3 or higher on item #3 of the 17-item Hamilton
Depression Rating Scale (HAM-D);2 and/or a score of less than 28 on the Mini-Mental State
Examination.3 Blood was collected at two screening visits spaced 1 to 4 weeks apart for analysis
of CRP at the Emory University Hospital Clinical Laboratory. Any measurement >10 mg/L was
repeated at ~2-week intervals to ensure stable levels of CRP over time, and in combination with
laboratory tests and physical examination, to exclude participants with active infections or other
acute or unstable medical conditions. The fMRI data from one participant had excessive head
motion (see fMRI analysis below), and three participants did not complete the study visit; data
was analyzed from a final sample of 48 subjects who completed fMRI, clinical and
neurocognitive assessments, and plasma collection for measurement of inflammatory
biomarkers.
BOLD fMRI data acquisition.
Neuroimaging data was acquired on a 3T Magnetom Trio scanner (Siemens Medical Solutions
USA) with a 32-channel head coil at the Emory-GA Tech BME Biomedical Imaging Technology
Center in the afternoon (3PM 2 hours). Anatomic images were obtained using a T1 weighted,
magnetization prepared rapid gradient echo (MPRAGE) sequence as 176 1-mm-thick sagittal
slices with the following parameters: field of view (FOV)=256x256 mm, repetition time (TR)=
2300 ms, echo time (TE)=3.02 ms, and flip angle (FA)=8°. Wakeful resting-state fMRI images
were acquired using a Z-saga pulse sequence for recovering ventral-frontal signal losses
regularly seen in gradient-echo BOLD fMRI.4 Z-saga images were acquired at 3.4x3.4x4 mm
resolution in 30 4-mm-thick axial slices with the following parameters: FOV 220×220 mm, TR
2950 ms, TE1/TE2 30/67 ms, FA 90° for 150 acquisitions over 7.4 min. During the resting-state
scan, participants were instructed to lie passively with central eye fixation and to refrain from
thinking about anything specific. Subjects were not allowed to eat or consume caffeine 3 hours
prior or to smoke cigarettes 1 hour prior to the scan and all subjects reported compliance.
BOLD fMRI analysis: head motion.
The threshold for head motion was <3.4 mm/degree in translation/rotation, consistent with
previous studies.5,6 The maximum and mean ( SD) head motion for all included subjects was
1.21, 0.30 (0.22); 2.51, 0.79 (0.63); 0.82, 0.27 (0.16); 2.17, 0.64 (0.48); 0.90, 0.29 (0.20); and
1.45, 0.51 (0.27) for Roll, Pitch, Yaw, dS, dL, and dP, respectively.
Self-report measures.
To assess anhedonia, The Snaith-Hamilton Pleasure Scale (SHAPS)7 was administered as well as
a subscale of the Inventory of Depressive Symptomatology - Self-Report (IDS-SR).8 The IDSSR is comprised of 30 questions encompassing a range of symptom severity scored 0-3. This
anhedonia subscale consisted of the sum of responses to 3 questions previously demonstrated to
be highly correlated with the both the self-administered and clinician administered SHAPS,9 an
instrument used to assess hedonic tone.7 This subscale included items #9 “response of mood to
good or desired events,” #19 “general interest,” and #21 “capacity for pleasure or enjoyment.”
Objective measures of psychomotor performance.
Finger Tapping Test: To assess motor speed, this task uses a specially adapted tapper that the
subject is asked to tap as fast as possible using the index finger. The subject is given 5
consecutive 10-second trials for both the preferred and non-preferred hands. The finger tapping
score is the mean of the 5 trials and is computed for each hand. A higher score corresponds to
better performance. Performance norms have been established, and scores have been shown to be
stable over time.10 The FTT is design to assess subtle motor impairment and has been found to be
altered in subjects with basal ganglia disorders and lesions.11
Trail Making Test A: Trail Making Test Part A is a timed task that provides information on
psychomotor processing speed.12,13 Trail Making Test A requires an individual to draw lines
sequentially connecting 25 encircled numbers distributed on a sheet of paper.10 A lower score
indicates better performance. Performance on the Trail Making Test A has been associated with
age-related decreases in the striatal dopamine system.14,15
Laboratory assays: plasma collection.
Blood was obtained in the morning (10AM1 hour) in EDTA tubes through an indwelling
catheter after participants had at least 30 minutes of rest. Blood was immediately centrifuged
(1000g for 15 minutes at 4°C), and plasma was removed and stored at −80°C until batched assay.
Laboratory assays: multi-analyte profiling (MAP) assays.
Plasma levels of cytokines and their soluble receptors were quantified using a Magpix
Instrument (Luminex), xPonent (Luminex) and Analyst (Millipore) software, and a fiveparameter curve fit. Cytokines were quantified by means of high sensitivity magnetic bead-based
multiplex immunoassays (Performance High Sensitivity Human MAP; R&D Systems,
Minneapolis, MN),16,17 and soluble cytokine receptors were quantified by means of regular
sensitivity multiplex assays (Screening Sensitivity Human MAP: R&D). Multiplex assays were
performed as recommended by the manufacturer’s protocol. The R&D Systems multiplex assays
have been shown to have excellent intra- and interassay reproducibility for interleukin (IL)-6 and
tumor necrosis factor (TNF) in a recent temporal stability study of circulating cytokine levels18
and very strong correlations (r=0.94) across a wide range of concentrations with high-sensitivity
ELISA Kits from the same manufacturer.19 The quantification of soluble cytokine receptors
using the regular sensitivity assay were further tested in our laboratory and concentrations of IL6 (IL-6sr) and TNF (sTNFR2) found to have similarly strong correlations (r=0.93 and 0.91,
respectively) with data previously published using Quantikine ELISA Kits from the same
manufacturer.20 See Supplementary Table 2 for CVs and MDLs for all analytes.
Statistics: mediation analysis.
Formal mediation analysis was conducted to assess whether functional connectivity mediates
relationships between inflammation (CRP) and behavior. Functional connectivity relationships
that were the most significant predictors of clinical variables that exhibited significant
associations with CRP (see Table 1) were examined. Therefore, left inferior ventral striatum
(iVS) to ventromedial prefrontal cortex (vmPFC) connectivity was examined as a potential
mediator of the relationship between CRP and anhedonia (as measured by the subscale of IDSSR), and right dorsal caudal putamen (dcP) to vmPFC connectivity was examined as a potential
mediator of the relationship between CRP and motor slowing (as measured by the Finger
Tapping Test) (Supplementary Figure 1). Supplementary Table 3 includes the results of the
mediation analysis and the  values that were used to calculate significance of the mediation
models using Sobel tests.21-23 Of note, we also conducted mediation analyses to determine
whether inflammation (CRP) mediated relationships between left iVS to vmPFC connectivity
and anhedonia, and right dcP to vmPFC connectivity and motor slowing, both of which were not
significant (Z=-0.59, S.E.=0.93, p=0.555 and Z=0.07, S.E.=8.96, p=0.941, respectively).
Supplementary Figure Legends
Supplementary Figure 1. Mediation models testing the hypothesis that functional
connectivity mediates the relationship between CRP and behavior. Behaviors that were
significantly associated with CRP (i.e. exhibited a significant overall effect, path c) and the
corticostriatal functional connectivity relationships that were most significantly associated with
the behaviors of interest were tested. Therefore, the first model examined whether (iVS) to
ventromedial prefrontal cortex (vmPFC) connectivity was a significant mediator of the
relationship between CRP and anhedonia. The second model examined whether right dorsal
caudal putamen (dcP) to vmPFC connectivity was a significant mediator of the relationship
between CRP and motor slowing.
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