Evidence suggests that precise cognitive and attentional demands of a task might be critical determinants of neuronal response to emotional faces, both in region-specific fMRI analysis (35) and effective connectivity modeling (51).
To determine causal influences among brain regions and more directly assess theoretical anatomical models requires testing of "effective connectivity," with models that embody causal connections such as structural equation modeling (29) or generative models such as dynamic causal modeling (DCM) (30,31).
This enables the parameters of the neuronal model (i.e., effective connectivity) and spatial model (i.e., dipole orientations) to be estimated from observed data using a Bayesian scheme.
In the future, functional and effective connectivity methods and models may further elucidate the neural underpinnings of synaesthetic colour experiences.
At its inception, effective connectivity referred to models; in the sense of the simplest possible circuit diagrams that explain observed responses [ 14].
Thus, unlike functional connectivity, effective connectivity is not model-free, but it requires the specification of a causal model which includes structural parameters.
Namely, the emergence of pathological beta oscillations in Parkinson's disease (PD) and their characterisation with intracortical and non-invasive methods to examine the underlying directed functional connectivity (Granger causality) and effective connectivity (dynamic causal modelling).
This hypothesis requires models of effective connectivity, in which connection strengths vary as a function of the associative strength predicted by the learning model.
There are different approaches for modelling effective connectivity from functional MRI, which include structural equation modelling (SEM), vector-autoregression models and DCM [35].
Regional responses at these maxima are reported in Table 2. Dynamic causal modeling was used to examine the effect of rMDD on effective connectivity with a set of models specified in SPM8, following methods recommended by Stephan et al. (30,43), which have reliably detected between-group differences in connectivity (38).
