Erik Barry Erhardt, PhD

On Jan 20th, 2009, I joined the Medical Image Analysis Laboratory (MIALab) as a research assistant (RA) at the MIND institute at UNM.  This position will transition to a 2-3 year postdoc upon the completion of my PhD this May.

Vince Calhoun, Edward Bedrick (my stat advisor), Jeremy Bockholt, and I compose the Biostatistics & NeuroInformatics Core (STATNI) on UNM’s Center of Biomedical Research Excellence (COBRE) grant funded by the National Center for Research Resources (NCRR), a part of the National Institutes of Health (NIH).  STATNI serves as a centralized resource for biostatistical consulting for a number of scientific projects. My role will be in the development of statistical methods and programming numerical and statistical methods to address the aims of the projects.  Specifically, the development of a Bayesian ICA model for fMRI data.

There are five aims to the project that will ultimately extend the ability to incorporate prior information to move beyond the semi-blind ICA approach. [from the project summary] First, we will extend our semi-blind ICA (sbICA) framework to provide a general framework for incorporating prior information from multiple spatial and temporal sources. In the second aim we will focus upon statistical inference and develop a framework for integrating the relevant functional components. In the third aim, we will validate the algorithms in aims 1 and 2, including using fMRI data collected on multiple days from a variety of paradigms. In this aim we develop a decision mechanism for selecting the best combination of methods given a particular problem. For the fourth aim, we will apply our methods to data collected during four well-studied paradigms in healthy controls and patients with schizophrenia. Our final aim involves the continuing development of our GIFT toolbox, and incorporation of the above algorithms, constraint selection mechanisms, and visual interfaces into the software. The successful completion of this research will provide a powerful set of tools for the research community to increase the sensitivity and specificity of BOLD analysis methods by drawing upon the strengths of both model-based and data-driven approaches. These tools will also provide a way to study the inter-relationship among functional networks in a flexible manner.

This is an ideal position for me because the modeling is similar to work I have done in my dissertation, I continue to work closely with my advisor, Ed, who I continue to learn so much from, I get to learn and work with Vince who has many ideas and is very prolific, and all of this in the hot area of fMRI.  I also have family and friends in Albuquerque who I want to stay close with for a little longer and this position allows me to stay put.

MIND

Christopher P. Bickford, Nate G. Mcdowell, Erik Barry Erhardt, Heath H. Powers, David T. Hanson. (2009)
“High frequency field measurements of diurnal carbon isotope discrimination and internal conductance in a semi-arid species, Juniperus monosperma“.
Plant, Cell & Environment, In print (1/28/09).

Chris Bickford, PhD candidate UNM Biology, and I met when we attended Iso-Camp at Jim Ehleringer’s lab at U Utah Summer 2008.  On the flight home we started discussing a challenge he was facing in his first of three dissertation papers. He studies details of plant photosynthesis.  He had complicated expressions for leaf carbon isotope discrimination and internal conductance based on CO concentrations of CO isotopologues and . He needed to propigate the variation of the CO measurements into his variables of interest, and .  He also needed to compare his accurate and precise measurements using tunable diode laser spectroscopy (TDL) to predictions from three models.

There were a number of statistical issues.  One was how to make model and observation comparisons.  I suggested using RMSE since it includes both variance and bias in the single measurement.  The main issue was the incorporation of variation from the CO measurements into the quantities of interest.  The bootstrap allowed us to do this.  There were a number of programming sessions in R to write functions and scripts to do all the calculations, create plots, output spreadsheets of results, and so on.  Chris has become a convert from Excel to R over the course of this project.  These methods implemented on this paper will likely flow into later pubs for both Chris and Dave.

Chris has taken a postdoc in New Zealand, where he and his wife, Karen, will spend the next two years with their dog.  He defends his dissertation on April 13th.

stable isotopes