Task-switching paradigms produce a highly consistent age-related increase in mixing cost [longer response time (RT) on repeat trials in mixed-task than single-task blocks] but a less consistent age effect on switch cost (longer RT on switch than repeat trials in mixed-task blocks). We use two approaches to examine the adult lifespan trajectory of control processes contributing to mixing cost and switch cost: latent variables derived from an evidence accumulation model of choice, and event-related potentials (ERP) that temporally differentiate proactive (cue-driven) and reactive (target-driven) control processes. Under highly practiced and prepared task conditions, aging was associated with increasing RT mixing cost but reducing RT switch cost. Both effects were largely due to the same cause: an age effect for mixed-repeat trials. In terms of latent variables, increasing age was associated with slower non-decision processes, slower rate of evidence accumulation about the target, and higher response criterion. Age effects on mixing costs were evident only on response criterion, the amount of evidence required to trigger a decision, whereas age effects on switch cost were present for all three latent variables. ERPs showed age-related increases in preparation for mixed-repeat trials, anticipatory attention, and post-target interference. Cue-locked ERPs that are linked to proactive control were associated with early emergence of age differences in response criterion. These results are consistent with age effects on strategic processes controlling decision caution. Consistent with an age-related decline in cognitive flexibility, younger adults flexibly adjusted response criterion from trial-to-trial on mixed-task blocks, whereas older adults maintained a high criterion for all trials.

Todd J, Provost A, Whitson LR, Cooper G, Heathcote A. Not so primitive: context-sensitive meta-learning about unattended sound sequences. J Neurophysiol 109: 99 -105, 2013. First published October 17, 2012 doi:10.1152/jn.00581.2012, an evoked response potential elicited when a "deviant" sound violates a regularity in the auditory environment, is integral to auditory scene processing and has been used to demonstrate "primitive intelligence" in auditory short-term memory. Using a new multiplecontext and -timescale protocol we show that MMN magnitude displays a context-sensitive modulation depending on changes in the probability of a deviant at multiple temporal scales. We demonstrate a primacy bias causing asymmetric evidence-based modulation of predictions about the environment, and we demonstrate that learning how to learn about deviant probability (meta-learning) induces context-sensitive variation in the accessibility of predictive long-term memory representations that underpin the MMN. The existence of the bias and meta-learning are consistent with automatic attributions of behavioral salience governing relevance-filtering processes operating outside of awareness. mismatch negativity; perceptual inference; salience; learning; auditory evoked potential HUMANS ARE ACCOMPLISHED at finding patterns in event sequences, an ability that is supported by automatic novelty detection mechanisms. In audition, automatic novelty detection is indexed by mismatch negativity (MMN), a fronto-central event-related potential (ERP) peaking 100 -200 ms after a novel event. The MMN, which is primarily generated in the auditory cortex, was first described by Näätänen, Gaillard, and Mäntysalo (1978) in an auditory oddball paradigm (e.g., a series of standard longer tones containing an occasional shorter oddball or deviant tone) through the use of deviant-standard difference waveforms. MMN is elicited automatically and is usually measured while participants attend to another modality (e.g., while reading or watching a silent movie), as it does not require attention but can be masked by attention-related ERPs. MMN amplitude is proportional to the difference between deviant and standard and is inversely proportional to the probability of the deviant. Early interpretations of the MMN (e.g., Näätänen and Michie 1979) were in terms of a mismatch between low-level auditory sensory memory traces of the standard and the deviant. However, mounting evidence has implicated much more sophisticated processing, leading Näätänen, Tervaniemi, Sussman, Paavilainen, and Winkler (2001) to characterize the MMN as a marker of "primitive intelligence" in the auditory cortex.Primitive intelligence is revealed by phenomena usually associated with higher-order cognition ranging from prediction and simple concept formation to mnemonic characteristics more associated with long-term memory than short-term sensory memory. For example, MMNs indicative of a left hemisphere specialization in extracting abstract rules are associated with violations of contingencies e...

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The role in which two tones are first encountered in an unattended oddball sequence affects how deviance detection, reflected by mismatch negativity, treats them later when the roles reverse: a "primacy bias." We tested whether this effect is modulated by previous behavioral relevance assigned to the two tones. To this end, sequences in which the roles of the two tones alternated were preceded by a go/no-go task in which tones were presented with equal probability. Half of the participants were asked to respond to the short sounds, the other half to long sounds. Primacy bias was initially abolished but returned dependent upon the go-stimulus that the participant was assigned. Results demonstrate a long-term impact of prior learning on deviance detection, and that even when prior importance/equivalence is learned, the bias ultimately returns. Results are discussed in terms of persistent go-stimulus specific changes in responsiveness to sound.

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