Wacongne et al. (2012) feature the existence of an internal model of temporal dependencies linking the transition probabilities of successive stimuli within a short time window in sensory memory. According to this model, the amplitude of the peak of synaptic strength coincides with the (regular) temporal interval between successive sounds and is proportional to the conditional probability of observing a given stimulus at a given latency (higher for standard, lower for deviant). In this perspective, isochrony in stimulus presentation would favor sensory learning/storage of first-order regularities by facilitating synaptic plasticity (Masquelier mTOR inhibitor et al., 2009). Our results suggest reformulating

such stance, as first-order prediction error appears to NVP-BKM120 predominantly depend on stimulus feature mismatch, with no significant contribution of temporal regularity. Instead, temporal information facilitates higher-order, contextual predictions. Thus, temporal regularity may help ‘memory neurons’ to evaluate the relevance of contextually valid sequential rules. One possible mechanism for this to happen is the unification of successive

events. In their original work, Sussman & Winkler (2001) proposed that highly probable deviant tone pairs are unified into a single perceptual event (‘perceptual’ unification). In our experiment, highly probable deviant repetitions in isochronous sequences yielded a clear MMN, accounting for a perceptually distinct event. However, there is evidence that the brain did not process them as ‘separate’ events. Both the attenuation of current density sinks (Fig. 3) and the inverse solution results (Figs 4 and 5, left side panels) suggest that

highly probable deviant repetitions activated a limited set of brain regions compared with less probable repetitions. More specifically, less probable repetitions included posterior STG structures, which are more likely to be devoted to low-level auditory processing (Brugge et al., 2003). For example, activity in the postcentral gyrus has been correlated with obligatory auditory N1 response peak amplitude (Mayhew et al., 2010), and the supramarginal gyrus is involved in auditory target detection tasks (Celsis et al., 1999), and short-term memory for pitch (change) information (Vines et al., 2006). If we ADAM7 assume that the successful extraction and application of temporal as well as formal regularities reduces the informativeness or surprise levels of predictable deviant repetitions, then it is reasonable to expect a concurrent diminution in the activity of brain structures deputy to low-level processing/short-term memory storage (Borst & Theunissen, 1999). This would favor the emergence of a more cognitive type of unification, linking individually perceived events into higher-order, two-tone units via predictive associations. An important question pertains to how temporal jitter may affect predictive processing.