The aims of this study were to present a method for
The aims of this study were to present a method for developing a path analytic network model using data acquired from positron emission tomography. conducted. Results indicate that using a sample size of less than = 15 per group will produce parameter estimates exhibiting bias greater than 5% and statistical power below .80. Neuroscientists in the field of human functional brain mapping use imaging modalities such as positron emission tomography (PET), transcranial magnetic stimulation (TMS), and functional magnetic resonance imaging (fMRI) to indirectly detect neural activity simultaneously occurring in various regions across the entire brain through metabolic and blood-oxygenation measures. The neural activity occurring within these anatomical regions of interest (ROIs) and their associated causal pathways provide a framework for modeling the covariance structure within the collective system. During data acquisition, the brain is repeatedly imaged while the individual is presented with stimuli or required to perform a task. Spatial variations in signal intensity across the acquired neuroimages reflect differences in brain activity during the presented stimuli or task performance. Statistical analysis of this functional neuroimaging data attempts to establish relationships between the location of activated brain regions and the particular aspect of cognition, perception, or other type of brain functioning being manipulated by the task or stimuli. Generally, this process proceeds by transformation of the data into matrix format with subsequent analyses conducted according to the general linear model (Friston, Holmes, et al., 1995; Holmes, Poline, & Friston, 1997). Establishing these functionClocation relationships and uncovering areas of functional dissociation within the cortex has been a primary focus of research, Losmapimod manufacture but more investigators are progressing from simple identification of network nodes toward studying the interactions between brain regions. The aim is to understand how sets and subsets of networks function as a whole with the intent of accomplishing specific cognitive goals. Previous studies have analyzed both correlational and covariance structures between brain regions, and techniques for applying structural equation modeling (SEM) to neuroimaging data to investigate connections between brain regions have been under development since 1991 (McIntosh & Gonzales-Lima, 1991, 1994; McIntosh et al., 1994). Initial application of SEM techniques to functional neuroimaging data was limited to a handful of researchers with advanced statistical backgrounds. In recent years, interest in SEM has increased due to improvements in and accessibility of commercial software and an unavoidable pressing need for the development of methods to test network models and investigate effective connectivity between neuroanatomical regions. Previous studies have applied SEM methods to PET and fMRI data as a means to investigate simple sensory and action processing, such as Losmapimod manufacture vision (McIntosh et al., 1994), audition (Gon?alves, Hall, Johnsrude, & Haggard, 2001), and motor execution (Zhuang, LaConte, Peltier, Zhang, & Hu, 2005), as well as higher order cognitive processing, such as working memory (Glabus et al., 2003; Honey et al., 2002), language (Bullmore et al., 2000), and attention (Kondo, Osaka, & Osaka, 2004), and multiple sclerosis (Au Duong et al., 2005). The analytic strategies that researchers conducting these studies have used either posited starting path models a priori based on a single theory alone and then proceeded in a confirmatory manner or an exclusively Bayesian approach to generate optimally weighted network models using little or no prior information. Two shortcomings of these previous studies are that the analytic strategies lack the ability to distinguish from multiple other equally plausible network models, and they did not consider the impact of sample size and its effect on statistical power and parameter estimation bias. To address these issues, we present a two-step approach that uses quantitative activation likelihood estimation (ALE) meta-analysis (Brown, Ingham, Ingham, Laird, & Fox, 2005; Turkeltaub, Guinevere, Jones, & Zeffiro, 2002) for identification of ROIs specific to our research problem in combination with Bayesian SEM to generate a highly informed network model. After model development, we examined issues that previous SEM-based neuroimaging studies have failed to address: sample size, statistical power, and parameter estimation bias. Given that the cost of data acquisition in functional imaging research is very high Losmapimod manufacture (e.g., approximately $3,000 per participant), the question of the requisite sample size necessary to model the neural system in a statistically valid and reliable manner is crucial to the ongoing conduct of this work. The overall aim of functional brain mapping is to determine where and how various cognitive and perceptual processes are controlled in the normal and abnormal (diseased) human brain. In discussing the need for a comprehensive cognitive ontology, Price and Friston (2005) detailed a clear argument for the need for sophisticated network analysis tools. Because there are an immeasurably large number of thought processes that control cognition, perception, action, and interoception, and a finite number of brain regions involved in carrying out these processes, these regions must interact in a highly Mouse monoclonal to Caveolin 1 complex and organized fashion. Determining and characterizing these interactions is a natural and obvious application of SEM. There are advantages to applying SEM to data acquired in human.