Modelling Trial-by-Trial Changes in the Mismatch Negativity
Figure 3
Structure of free-energy based models of the MMN.
Our free-energy models of trial-wise MMN amplitudes ( in Figure 2) are cast within the general dynamic state-space framework formulated in Equation (1). In contrast to the phenomenological models, the internal states (
) represent probabilistic beliefs about the environment and evolve according to approximate Bayesian inference by free-energy minimization (
). All of these models share the Bayesian observer defined by the evolution function
and the probabilistic mental model
, but differ in their response functions
. The graph in the innermost box shows the mental model
as a probabilistic graphical model (with arrows indicating conditional dependencies). The random variables in circles are sensory inputs (
), tone categories (
), and transition probabilities (
). This mental model determines how subjects perceive, learn about and predict tone sequences. Please see Table 2 for an explanation of the mathematical notation.