Cephalometry

A total of five P. obtusospinosa colonies were reared in the lab from founding queens collected in Tucson, Arizona in mid-July 2004. All colonies were kept in constant darkness, humidity, and temperature (30°C). They were sampled for major workers once in either March or April 2005, well after worker size distributions had stabilized [∼8 to 9 months after colony founding (Huang and Wheeler, unpublished)]. For each colony, all major workers were isolated into a large Petri dish, and a sample of that subpopulation was taken by randomly placing a smaller Petri dish upside-down into the larger Petri dish. All majors lying within the small Petri dish were collected and measured. The number of majors collected for each colony ranged from 76 to 111 individuals. Minor workers from each colony were sampled on different dates from major workers; three colonies were sampled for minors in February 2005 while two colonies were sampled in both February and May 2005. During each sampling date, 15 to 16 minors were randomly collected directly from each colony. A total of 446 majors and 111 minors were measured for the five colonies sampled. Head width measurements were made for both minor and major workers by using a microscope reticle. Head width was obtained by measuring the distance between the two most widely separated points on the two sides of the head, as seen from the frontal view. A cluster analysis was performed on the worker size distribution (with the assumption that there were two modes) to determine where the cutoff of the large and small major worker ranges were. The statistical package JMP 5.1 was used.

MRI data were acquired at nine scanning sites. All sites operate Siemens scanners, including three TIM Trio systems, four Verio systems, one Skyra system, and one Prisma system.
The standard DELCODE MR protocol included a structural T1-weighted image, a resting state fMRI (including IR-EPI and a field map), a T2-weighted structural scan optimized for volumetric assessment of the medial temporal lobe acquired in oblique coronal orientation perpendicular to the longitudinal axis of the hippocampus, a task fMRI (scene novelty and encoding task), and a quantitative susceptibility weighted image. This protocol was used in eight out of the nine scanning sites. One of the sites did not have the provision to conduct the task fMRI and instead conducted a diffusion tensor imaging (DTI) protocol. At three sites participants also underwent an optional second day of scanning with DTI, a task fMRI to assess object and scene processing and mnemonic discrimination, and a T1-weighted FLASH sequence optimized to image the locus coeruleus.
For task fMRI, all sites were equipped with a high-resolution (1280 Px × 800 Px) 30-inch MR-compatible LCD screen (“Medres Optostim”). All monitors were calibrated and configured to maintain the distance, luminance, color, and contrast constant across sites. Responses during task fMRI were recorded at all sites with MR-compatible response buttons (CurrentDesign). All participants underwent vision correction with MR-compatible goggles (Medigoogle; Cambridge Research Systems) according to the same SOP for all MRI sites. Task fMRI scenario files were controlled with Presentation (Neurobehavioral Systems).
For quality assurance (QA) and assessment, the following steps were taken. The DZNE imaging network, headed by the Magdeburg DZNE site (iNET), qualified each MRI site with a traveling head measurement prior to the start of the study. DZNE iNET then provided every site with detailed SOPs for the implementation of each protocol. All radiographers who operate MRIs in the study underwent centralized training to implement the SOPs (i.e., subjects’ positioning in the MRI scanner, sequence preparation steps, image angulation, task-fMRI visual acuity checks and correction, participant instruction, and testing).
A small MRI-phantom built and designed by the American College of Radiology (ACR) is used to monitor the performance of the MR systems on a weekly basis. The phantom images are analyzed according to a published protocol [24 (link)]. A custom-built holder was designed to maximize reproducibility in phantom positioning across all nine MRI sites.
For QA, every scan underwent a quality check for SOP conformity and scan quality by the DZNE iNET team (Magdeburg). To establish inclusion/exclusion criteria based on data-driven quantitative metrics, a Bayesian-based strategy is being developed which will use the current manual/semi-automatic QA information for training after processing the images using the pcp-qa package (www.preprocessed-connectomes-project.org/quality-assessment-protocol/)). Details on individual MR sequences and the fMRI experiments will be reported together with results in subsequent publications.
Baseline MRI scans of 367 individuals were obtained from the initial 400 participants reported here. In addition, 117 datasets of the extended protocol were acquired.