RESUMEN
OBJECTIVE: To elaborate the recent theory of prediction models of the brain in light of actual neural activities, it is important to investigate the cross-modal interactions in the context of prediction construction. To this end, in this study, we assessed whether cross-modal disturbances would result in the attenuation of mismatch negativity in anesthetized animal models. METHODS: A surface electrode array recorded neural activities from the visual and auditory cortices of rats under isoflurane anesthesia, during an auditory oddball paradigm over the course of three audiovisual sequences. In the audiovisual sequences, the visual stimuli were simultaneously presented with the first, second, or third standard before the deviants. RESULTS: The interrupting visual stimuli decrease the amplitude of mismatch negativity in the auditory and visual cortices. In addition, the correlation coefficients between the amplitude of middle-latency potential for the interrupting visual stimuli and the amplitude of mismatch negativity to the following auditory deviant stimuli were smaller when the visual stimuli were presented alongside the third standards from the deviants. CONCLUSION: Such attenuation in mismatch negativity has been often associated with a top-down mechanism and the present anesthesia selectively attenuates top-down transmission. Taken together, our study's findings indicate that the cross-modal disturbances on prediction and deviation detection may also be mediated by bottom-up mechanisms, as well as previously reported top-down mechanisms.
Asunto(s)
Corteza Auditiva , Electroencefalografía , Estimulación Acústica , Animales , Encéfalo , Electrodos , Potenciales Evocados Auditivos , RatasRESUMEN
When the brain tries to acquire an elaborate model of the world, multisensory integration should contribute to building predictions based on the various pieces of information, and deviance detection should repeatedly update these predictions by detecting "errors" from the actual sensory inputs. Accumulating evidence such as a hierarchical organization of the deviance-detection system indicates that the deviance-detection system can be interpreted in the predictive coding framework. Herein, we targeted mismatch negativity (MMN) as a type of prediction-error signal and investigated the relationship between multisensory integration and MMN. In particular, we studied whether and how cross-modal information processing affected MMN in rodents. We designed a new surface microelectrode array and simultaneously recorded visual and auditory evoked potentials from the visual and auditory cortices of rats under anesthesia. Then, we mapped MMNs for five types of deviant stimuli: single-modal deviants in (i) the visual oddball and (ii) auditory oddball paradigms, eliciting single-modal MMN; (iii) congruent audio-visual deviants, (iv) incongruent visual deviants, and (v) incongruent auditory deviants in the audio-visual oddball paradigm, eliciting cross-modal MMN. First, we demonstrated that visual MMN exhibited deviance detection properties and that the first-generation focus of visual MMN was localized in the visual cortex, as previously reported in human studies. Second, a comparison of MMN amplitudes revealed a non-linear relationship between single-modal and cross-modal MMNs. Moreover, congruent audio-visual MMN exhibited characteristics of both visual and auditory MMNs-its latency was similar to that of auditory MMN, whereas local blockage of N-methyl-D-aspartic acid receptors in the visual cortex diminished it as well as visual MMN. These results indicate that cross-modal information processing affects MMN without involving strong top-down effects, such as those of prior knowledge and attention. The present study is the first electrophysiological evidence of cross-modal MMN in animal models, and future studies on the neural mechanisms combining multisensory integration and deviance detection are expected to provide electrophysiological evidence to confirm the links between MMN and predictive coding theory.