The functional anatomy of the MMN: a DCM study of the roving paradigm.

Using dynamic causal modelling (DCM), we have presented provisional evidence to suggest: (i) the mismatch negativity (MMN) is generated by self-organised interactions within a hierarchy of cortical sources [Garrido, M.I., Kilner, J.M., Kiebel, S.J., Stephan, K.E., Friston, K.J., 2007. Dynamic causal modelling of evoked potentials: a reproducibility study. NeuroImage 36, 571-580] and (ii) the MMN rests on plastic change in both extrinsic (between-source) and intrinsic (within source) connections (Garrido et al., under review). In this work we re-visit these two key issues in the context of the roving paradigm. Critically, this paradigm allows us to discount any differential response to differences in the stimuli per se, because the standards and oddballs are physically identical. We were able to confirm both the hierarchical nature of the MMN generation and the conjoint role of changes in extrinsic and intrinsic connections. These findings are consistent with a predictive coding account of repetition-suppression and the MMN, which gracefully accommodates two important mechanistic perspectives; the model-adjustment hypothesis [Winkler, I., Karmos, G., Näätänen, R., 1996. Adaptive modelling of the unattended acoustic environment reflected in the mismatch negativity event-related potential. Brain Res. 742, 239-252; Näätänen, R., Winkler, I., 1999. The concept of auditory stimulus representation in cognitive neuroscience. Psychol Bull 125, 826-859; Sussman, E., Winkler, I., 2001. Dynamic sensory updating in the auditory system. Brain Res. Cogn Brain Res. 12, 431-439] and the adaptation hypothesis [May, P., Tiitinen, H., Ilmoniemi, R.J., Nyman, G., Taylor, J.G., Näätänen, R., 1999. Frequency change detection in human auditory cortex. J. Comput. Neurosci. 6, 99-120; Jääskeläinen, I.P., Ahveninen, J., Bonmassar, G., Dale, A.M., Ilmoniemi, R.J., Levänen, S., Lin, F.H., May, P., Melcher, J., Stufflebeam, S., Tiitinen, H., Belliveau, J.W., 2004. Human posterior auditory cortex gates novel sounds to consciousness. Proc. Natl. Acad. Sci. U. S. A. 101, 6809-6814].