In the same studies results for

In the same studies, results for N2 amplitude were similarly variable. N2 was smaller (Čeponienė et al., 2001) or equal in size (Bruder et al., 2011) for vowels and simple tones when compared to complex tones, but larger for syllables than nonspeech analogues (Čeponienė et al., 2005, 2008). Since the amplitude of N2 elicited by tone pips was found to increase with repetition in nine-year-olds (Karhu et al., 1997), larger N2s to complex sounds than vowels were interpreted as memory-trace build-up for the unfamiliar stimuli (Čeponienė et al., 2001). In the studies using syllables, N2 and N4 behaved similarly, and were suggested to reflect higher-order sound analysis, such as the content recognition of syllables, scanning for access to semantic representations, or short-term memory retrieval (Čeponienė et al., 2001, 2005, 2008). As N4 was also larger for vowels than simple or complex tones, it KY 02111 manufacturer is the only component, which has consistently had larger amplitude for speech than nonspeech sounds, and was thus interpreted as an index of sound “speechness” (Čeponienė et al., 2001, 2005, 2008). A few studies of preschool children with clinical groups also stress the usefulness of ERPs as indexes of language development. For example, Lovio et al. (2010) reported diminished P1 peaks to syllables in 6-year-old children at risk for dyslexia, whereas Hämäläinen et al. (2013) reported abnormally large N2s to a short pseudo-word and its nonspeech counterpart in 6-year-old children who three years later had reading problems. Furthermore, in a longitudinal study, Espy et al. (2004) presented syllables and sinusoidal tones with long, 2.5-4.0s inter-stimulus intervals (ISI), which produces the child N1 in addition to the P1-N2-N4 complex. Increased N1 amplitudes to both speech and nonspeech stimuli between ages 1 and 4 years were related to poorer pseudo-word reading at school, whereas decreased N2 amplitudes to nonspeech stimuli between ages 4 and 8 years predicted poorer word reading at school. Here, our goal was to fill a gap in research by contrasting speech and nonspeech sound processing in preschoolers, using syllables and nonspeech stimuli that were carefully matched for acoustic properties with the speech stimuli. As, to our knowledge, there are no such previous studies in six-year-olds, our hypotheses are only tentative. If sound detection quality processing in preschoolers is akin to school-aged children, we will observe smaller P1 but larger N2 and N4 responses to syllables than nonspeech sounds (Bruder et al., 2011; Čeponienė et al., 2001, 2005, 2008). We will also analyze the relationship between cortical responses and neurocognitive task performance, expecting P1 amplitude to be associated with better phonological skills (Bruder et al., 2011), and larger speech than nonspeech N2/N4s to be associated with better cognitive functioning.
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Conflict of interest
Acknowledgments We thank the children and families for participating, and Pirita Uuskoski, Piia Turunen, Lilli Kimppa, Saila Seppänen, Henna Markkanen, and Roope Heikkilä for their help in data collection, as well as Prof. Paavo Alku for his comments on the stimuli. This work was supported by the Academy of Finland (grants number 128840 and 1276414), the Finnish Cultural Foundation, Ella and Georg Ehrnrooth Foundation, Emil Aaltonen Foundation, Kone Foundation, Lundbeck Foundation, and Jane and Aatos Erkko Foundation.
Introduction Intra-subject variation in reaction time (ISVRT) is a measure of a subject’s consistency in responding to stimuli across a task, often quantified as the standard deviation of RT across a task epoch; higher ISVRT, reflected in larger standard deviations, is associated with greater variability, or inconsistency, of responses. ISVRT is a developmentally-important phenomenon; it decreases from childhood through young adulthood (Williams et al., 2005, 2007; Dykiert et al., 2012; Li et al., 2009, 2004; Tamnes et al., 2012), paralleling the behavioral development of executive functions such as attention and self-regulation (Gomez-Guerrero et al., 2011), as well as structural brain development within the frontal lobes (Marsh et al., 2008; Giedd, 2004; Gogtay et al., 2004). Further, atypical ISVRT is associated with developmental disorders of executive control linked to atypical brain development (Bora et al., 2006; Leth-Steensen et al., 2000; Kaiser et al., 2008; Adleman et al., 2014, 2012; Brotman et al., 2009; Castellanos et al., 2005; Epstein et al., 2011). Thus, determining how the relationship between ISVRT and brain activity supporting executive functions varies with age may ultimately inform our understanding of both normal and atypical cognitive development.