Neurophysiological indices of attention to speech in children with specific language impairment

Abstract

Objective-The aim was to determine whether children with Specific Language Impairment (SLI) differed from children with typical language development (TLD) in their allocation of attention to speech sounds.Methods-Event-related potentials were recorded to nontarget speech sounds in two tasks (passivewatch a video and attend to target tones among speech sounds) in two experiments, one using 50-ms duration vowels and the second using 250-ms vowels. The difference in ERPs across tasks was examined in the latency range of the early Negative difference wave (Nd) found in adults. Analyses of the data using selected superior and inferior sites were compared to those using electrical field power (i.e., global field power or GFP). The topography of the ERP at the maximum GFP was also examined.Results-A negative difference, comparable to the adult Nd, was observed in the attend compared to the passive task for both types of analysis, suggesting allocation of attentional resources to processing the speech stimuli in the attend task. Children with TLD also showed greater negativity than those with SLI in the passive task for the long vowels, suggesting that they allocated more attentional resources to processing the speech in this task than the SLI group. This effect was only significant using the GFP analysis and was seen as smaller GFP for the TLD than SLI group. The SLI group also showed significantly later latency than the TLD group in reaching the maximum GFP. In addition, a significantly greater proportion of children with SLI compared to those with typical language showed left-greater-than-right fronto-central amplitude at the latency determined from each child's maximum GFP peak.Conclusions-Children generally showed greater attention to speech sounds when attention is directed to the auditory modality compared to the visual modality. However, children with TLD, unlike SLI, also appear to devote some attentional resources to speech even in a task in which they are instructed to attend to visual information and ignore the speech.Significance-These findings suggest that children with SLI have limited attentional resources, that they are poorer at dividing attention, or that they are less automatic in allocating resources to speech compared to children with typically developing language skills.

The maturation of human evoked brain potentials to sounds presented at different stimulus rates

“…In the current study, the N1 component was not present in the pediatric waveforms as a discrete component; rather, it appeared as a negative deflection within the positive waveform. The biphasic positive component of the child waveform is consistent with other reports using stimulus rates faster than 1 s (e.g., Ponton et al, 2000;Shafer et al, 2007;Sharma et al, 1997Sharma et al, , 2005. (2) The N2 has been observed in previous studies at a consistent latency of 250 ms, when ISIs were over 1 s, and therefore has often been called the "N250" (Shafer et al, 2000;Vidal et al, 2005).…”

“…To provide data unbiased by analysis at a single electrode site, component identification was initially performed using GFP analysis Skrandies, 1980,1984;Michel et al, 2004;Shafer et al, 2007). Table 2 reports the GFP peak latency for each component in each condition and age group.…”

Maturation of Speech Discrimination in 4- to 7-Yr-Old Children as Indexed by Event-Related Potential Mismatch Responses

“…The greater interstimulus interval between deviants resulted in greater recovery from refractoriness to the deviants, and thus a larger positivity. The onset of the P100 is argued to mature into the adult P1 and the offset into the mature P2 (Ponton et al 1996;Shafer et al 2007). The N1b is absent from children's waveforms at fast rates of stimulation (Ͻ1 sec), because it is highly refractory in children and infants (Ponton et al 2000;Gilley et al 2005;Sussman et al 2008).…”

Speech perception and lexical effects in specific language impairment

“…/ba/, /da/) and stressed and unstressed multi-syllable pairs (e.g. /dabida/, /dabuda/) differing by transition duration, inter-stimulus intervals, and vowel steady state durations have revealed temporal impairments (Bradlow et al, 1999; Burlingame, Sussman, Gillam, & Hay, 2005; Elliott & Hammer, 1988; Frumkin & Rapin, 1980; Leonard et al, 1992; McArthur & Bishop, 2004; Shafer, Ponton, Datta, Morr, & Schwartz, 2007; Stark & Heinz, 1996; Tallal & Stark, 1981; Tallal et al, 1980). The relative duration of neighboring segments and syllables (Leonard et al, 1992; Tallal & Piercy, 1975) also appears to affect identification accuracy.…”