Pre-conference workshop: Visual mismatch negativity
Tuesday, Sep 8, 2015
10:00-17:00
SKH Z005
„What is it?” and „Where is it going?” Two questions in the language of the brain: the additivity issue of the visual mismatch negativity
Institute of Cognitive Neuroscience and Psychology, RCNS HAS, Budapest, Hungary
sulykos.istvan@ttk.mta.hu
We investigated the relationships of visual mismatch negativity (vMMN) generators during the processing of double deviancies in case of various elementary features. Theories of independent, modular mechanisms suppose that vMMN signal is aggregated to multiple deviants. This is because the deviant-related response was generated by independent brain electrical activities to the single deviations. In contrast, interactive processes would result in super- or sub-additive responses. In a series of five experiments, we compared the effects of two separate deviant features with the joint effect of the two features. The stimulus dimensions were orientation (O), movement direction (MD) and spatial frequency (SP). The stimuli (patterns of Gabor-patches) were delivered in passive oddball paradigms. O-SF double deviant elicited sub-additive vMMN irrespective of whether the stimulation were static (Experiment 1) or dynamic (Experiment 2). Contrarily, MD-O double deviant elicited additive vMMN (Experiment 3). However, in the latter experiment, the onsets of O and MD deviancies were asynchronous (the O deviancy preceded the MD deviancy) while in Experiment 1 and 2, the deviancies occurred simultaneously. Therefore, the following two experiments were designed in such a way that the MD deviancy was either concurrent with (Experiment 4) or followed by (Experiment 5) the SF deviancy. In both cases, the vMMN to double deviants were additive again. As the robust results of the studies show, deviant-related processing of movement direction is independent of the deviant-related processings of orientation and spatial frequency, while the latter two are mutually dependent.