![]() ![]() Jones and colleagues ( Jones et al., 1998 Jones and Perez, 2001, 2002) reported that the ACC response could also be recorded in response to changes in pitch and/or timbre of synthesized music. ![]() ![]() They found that the ACC response could be reliably elicited by changes along these acoustic dimensions. In a series of studies, Martin and Boothroyd (1999, 2000) investigated the ACC responses evoked by changes in periodicity, intensity, and spectrum of long-duration, ongoing stimuli. The ACC response can only be evoked by long-duration, time-varying stimuli. It has been suggested that the ACC response represents a change detection response rather than a simple onset response even though the P1-N1-P2 complex elicited by a brief acoustic stimulus and the ACC response show similar general characteristics ( Martin et al., 2008). (1998) referred to the response elicited by the vowel /ei/ when presented in the context of an ongoing syllable /sei/ as the “N1-P2 acoustic change complex (ACC).” They suggested that the ACC response might indicate auditory discrimination capacity. They found that the response evoked by the speech token /sei/ consisted of two overlapping onset responses – one to the fricative /s/ and one to the vowel /ei/. (1998) recorded cortical potentials in response to three naturally produced speech tokens: /s/, /ei/, and /sei/ in eight normal hearing listeners. However, studies have shown that it can also be elicited by changes in a continuous stimulus or a stimulus with long duration. The P1-N1-P2 complex is typically recorded in response to brief acoustic stimuli, such as clicks, tones, and short-duration speech tokens. When recorded from adult listeners using a brief acoustic stimulus, the P1-N1-P2 complex consists of three peaks (two vertex positive, one vertex negative) that occur during the time window between 50 to 250 msec after stimulus onset. ![]() The P1-N1-P2 complex is an auditory evoked potential that can be recorded from surface electrodes placed on the scalp and is thought to reflect primarily cortical generators. Therefore, such measures can provide a non-behavioral means of investigating the auditory processing of sound, and may provide information about underlying physiological mechanisms. In addition, unlike psychophysical measures, electrophysiological assessment can be more objective and less affected by factors such as memory, motivation, task, and response criteria. Compared with behavioral tasks, many electrophysiological measures do not require active participation from listeners and can be reliably recorded from infants and very young children. This presents a challenge when trying to obtain similar, and reliable, behavioral responses from infants and young children. However, performing these measures requires a significant amount of linguistic experience and cognitive ability. Such psychophysical measures can provide useful information about a listener's auditory perception of a dynamic sound. Typically, auditory discrimination abilities in adult listeners are assessed using behavioral measures. Understanding daily conversation depends on the ability of the auditory system to detect ongoing changes in the spectral and temporal patterns of incoming signals. ![]()
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