Event-related potentials induced by somatosensory and after auditory stimulation or bilateral somatosensory stimulation in young adults were studied, aiming to evaluate interactions of cognitive processing of somatosensory and auditory information. In experiment 1, event-related potentials were elicited by four stimulus conditions which were randomly presented with an interstimulus interval of 20 +/- 3 milliseconds: electric stimuli delivered to the right median nerve (Con 1), auditory stimuli delivered to both ears (Con 2), electric and subsequent auditory stimuli (Con 3), and electric stimuli delivered to the bilateral median nerve (Con 4). In experiment 2, Con 2 was changed to electric stimulation of the left median nerve. The subtraction of grand averaged event-related potentials of Con 1 and Con 2 from those of Con 3 demonstrated a positive-negative peak complex with a positive peak at approximately 165 to 170 milliseconds after stimuli and a negative peak with a mean latency of 372 milliseconds in experiment 1. In experiment 2, the subtraction of event-related potentials in Con 1 and 2 from those in Con 4 revealed positive and negative peaks resembling those in experiment 1, but the distribution or latencies of the peaks differed from those in experiment 1. We speculate that the subtracted positive and negative peaks reflect different cognitive processing of bimodal and bifocal sensory information.
Social norms, including values, beliefs and even perceptions about the world, are preserved and created through repeated interactions between individuals. However, whereas neuro-cognitive research on social norms has used the “unilateral influence” paradigm focusing on people’s reactions to extant standards, little is known about how our basic perceptions and judgments are shaped as new norms through bilateral interaction. Here, using a simple estimation task, we investigated the formation of perceptual norms using two experiments coupled with computational modeling. In the behavioral experiment, participants in dyads repeatedly estimated the number of dots on a screen and viewed each other’s answers. In the fMRI experiment, we manipulated the interaction process by pairing each participant with a computer agent which adjusted its estimations reciprocally to participants’ estimations (bilateral agent) or did not (unilateral). The results indicated that only the bilateral interaction yielded convergence of participants’ covert psychophysical functions (relations between subjective estimations and the actual number of dots) as well as overt behavioral responses within a pair. Bilateral interaction also increased the stability (reliability) of the covert function within each individual after interaction. Neural activity in the mentalizing network (right temporoparietal junction and dorsomedial prefrontal cortex) during interaction modulated the stabilization of the psychophysical function. These results imply that bilateral interaction helps people to cognitively anchor their views with each other. Such spontaneous perspective sharing can yield a shared covert “generative model” that enables endogenous agreement on totally new targets ― one of the key features of social norms.
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