The effects of stimulus deviance and novelty on cerebral lateralization in event-related potentials during auditory and visual continuous performance tasks
McCabe, Danielle C
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Stimulus deviance, or novelty, has been defined as difference from either immediate context (episodic deviance) which engages anterior brain regions, or from long-term experiences (generic deviance) which recruits a distributed network including posterior brain regions for in-depth assessment. Deviance detection and novelty are commonly studied using oddball paradigms with startling novel stimuli. The N2 event-related potential (ERP) component has been associated with both passive/pre-attentive and active discrimination of unpredictable changes (deviance) in stimuli. The P3 is considered an index of cognitive processes; Novelty P3/P3a is associated with novelty detection and orienting. The N2/P3a is associated with CNS orienting processes, reflecting gating mechanisms for resources allocated to investigating novel/deviant stimuli. The current study examined the effects of a non-startling novel stimulus embedded in parallel auditory and visual continuous performance tasks (CPT) on the N2 and P3 ERP components. The CPT, a sustained attention task with different letters creating a continuously deviant stream of stimuli, allows for the examination of different cognitive functions including target detection, response inhibition, and novelty detection. Participants were 23 college students ages 17 to 26. The results indicated a modality difference for the Novel condition. The auditory novel had delayed response latency for both N2 and P3 components, visual did not. Hemispheric differences in N2 amplitude were only seen for the auditory novel condition. The P3 response showed hemispheric differences for Go, NoGo and other conditions, but not for Novelty in either modality, suggesting P3 may be more sensitive to language aspects of the CPT than N2. Region, especially anterior, was more important than hemisphere for deviance detection for both N2 and P3. The latency of the N2/P3a complex was sensitive to deviance detection in the anterior region, and sensitive to time spent evaluating novel stimuli in the posterior region. The N2 amplitude was sensitive to expectancy mismatch in the CPT. Males responded differently to expectancy mismatch than females (generally higher N2 amplitude for NoGo) in both modalities. N2 was shown to be a sensitive to deviance detection within a CPT, while N2/P3a latency was shown to be the most sensitive index of differences between deviance and non-startling novelty.