NEURAL-NETWORK CLASSIFICATIONS AND CORRELATION-ANALYSIS OF EEG AND MEG ACTIVITY ACCOMPANYING SPONTANEOUS REVERSALS OF THE NECKER CUBE

It has recently been suggested that reentrant connections are essentia l in systems that process complex information [A. Damasio, H. Damasio, Cortical systems for the retrieval of concrete knowledge: the converg ence zone framework, in: C. Koch, J.L. Davis (Eds.), Large Scale Neuro nal Theories of the Brain, The MIT Press, Cambridge, 1995, pp. 61-74; G. Edelman, The Remembered Present, Basic Books, New York, 1989; M.I. Posner, M. Rothbart, Constructing neuronal theories of mind, in: C. Ko ch, J.L. Davis (Eds.), Large Scale Neuronal Theories of the Brain, The MIT Press, Cambridge, 1995, pp. 183-199; C. von der Malsburg, W. Schn eider, A neuronal cocktail party processor, Biol. Cybem., 54 (1986) 29 -40]. Reentry is not feedback, but parallel signalling in the time dom ain between spatially distributed maps, similar to a process of correl ation between distributed systems. Accordingly, it was expected that d uring spontaneous reversals of the Necker cube, complex patterns of co rrelations between distributed systems would be present in the cortex. The present study included EEG (n = 4) and MEG recordings (n = 5). Tw o experimental questions were posed: (1) Can distributed cortical patt erns present during perceptual reversals be classified differently usi ng a generalised regression neural network (GRNN) compared to processi ng of a two-dimensional figure? (2) Does correlated cortical activity increase significantly during perception of a Necker cube reversal? On e-second duration single trials of EEG and MEG data were analysed usin g the GRNN. Electrode/sensor pairings based on cortico-cortical connec tions were selected to assess correlated activity in each condition. T he GRNN significantly classified single trials recorded during Necker cube reversals as different from single trials recorded during percept ion of a two-dimensional figure for both EEG and MEG. In addition, cor related cortical activity increased significantly in the Necker cube r eversal condition for EEG and MEG compared to the perception of a non- reversing stimulus. Coherent MEG activity observed over occipital, par ietal and temporal regions is believed to represent neural systems rel ated to the perception of Necker cube reversals. (C) 1998 Elsevier Sci ence B.V.