Whole-head magnetoencephalographic (MEG) responses to repeating standard tones and to infrequent slightly higher deviant tones and complex novel sounds were recorded together with event-related brain potentials (ERPs). Deviant tones and novel sounds elicited the mismatch negativity (MMN) component of the ERP and its MEG counterpart (MMNm) both when the auditory stimuli were attended to and when they were ignored. MMNm generators were located bilateral to the superior planes of the temporal lobes where preattentive auditory discrimination appears to occur. A subsequent positive P3a component was elicited by deviant tones and with a larger amplitude by novel sounds even when the sounds were to be ignored. Source localization for the MEG counterpart of P3a (P3am) suggested that the auditory cortex in the superior temporal plane is involved in the neural network of involuntary attention switching to changes in the acoustic environment.

Although the generality of dyslexia and its devastating effects on the individual's life are widely acknowledged, its precursors and associated neural mechanisms are poorly understood. One of the two major competing views maintains that dyslexia is based primarily on a deficit in linguistic processing, whereas the other view suggests a more general processing deficit, one involving the perception of temporal information. Here we present evidence in favor of the latter view by showing that the neural discrimination of temporal information within complex tone patterns fails in dyslexic adults. This failure can be traced to early cortical mechanisms that process auditory information independently of attention.

This chapter describes how auditory and visual attention can be studied using event‐related potentials (ERPs). In audition, the mismatch negativity (MMN), a component of the ERP elicited by any discriminable change in an auditory stimulus stream, provides an excellent index of attention‐independent auditory processing: MMN data convincingly show that accurate central sound representations emerge even in the absence of attention. ERPs also index the two principal brain mechanisms that are involved in involuntary attention switch to unattended auditory stimulation, with the N1 component being related to attention switch to sound onset and the MMN as well as P3a components reflecting attention switch to sound change. Furthermore, the newly discovered reorienting negativity (RON) component seems to be related to the focusing of attention to task‐relevant aspects of stimulation following distraction. The processing negativity (PN), in turn, provides an on‐line index of auditory selective attention. In the visual modality, several ERP components are modulated by selective attention, the earliest effect being caused by visuo‐spatial attention which even affected the P1 generated in extrastriate cortex with a onset latency of about 70 ms post‐stimulus. The subsequent N1 component may also tap into attentional functions and, in addition, slow, PN‐type of selection negativities and positivities can be obtained, depending on the selection criteria (e.g., color or form) and the attentional demands.

Language and learning disabilities occur in almost half of individuals with oral clefts. The characteristics of these cognitive dysfunctions vary according to the cleft type, and the mechanisms underlying the relation between cleft type, cognitive dysfunction, and cleft-caused middle-ear disease are unknown. This study investigates preattentive auditory discrimination, which plays a significant role in language acquisition and usage, in infants with different cleft types. A mismatch negativity (MMN) component of brain evoked potentials, which indexes preconscious sound discrimination, and brain responses to rare sine-wave tones were recorded in 12 healthy infants and 32 infants with oral clefts at the ages of 0 and 6 months. Infants with clefts were subdivided into two categories: those with cleft lip and palate (CLP) (n=11 at birth, n=6 at the age of 6 months) and those with cleft palate only (CPO) (n=17 at birth, n=8 at the age of 6 months). At both ages, brain responses to rare sounds tended to be smaller in both cleft subgroups than in healthy peers. However, in the latency range of 300 to 500 ms, the MMN was significantly smaller in infants with CPO. In infants with CLP, the MMN was comparable to that of healthy infants. Differences in auditory discrimination between infants with CLP and CPO, as reflected by MMN, were detectable at birth and persisted into later infancy. This pattern parallels known behavioural differences between children with these cleft types. Brain responses to rare sounds, in contrast, had no differentiative power with respect to the cleft type.