Speech-induced suppression of evoked auditory fields in children who stutter

Abstract

Auditory responses to speech sounds that are self-initiated are suppressed compared to responses to the same speech sounds during passive listening. This phenomenon is referred to as speech-induced suppression, a potentially important feedback-mediated speech-motor control process. In an earlier study, we found that both adults who do and do not stutter demonstrated a reduced amplitude of the auditory M50 and M100 responses to speech during active production relative to passive listening. It is unknown if auditory responses to self-initiated speech-motor acts are suppressed in children or if the phenomenon differs between children who do and do not stutter. As stuttering is a developmental speech disorder, examining speech-induced suppression in children may identify possible neural differences underlying stuttering close to its time of onset. We used magnetoencephalography to determine the presence of speech-induced suppression in children and to characterize the properties of speech-induced suppression in children who stutter. We examined the auditory M50 as this was the earliest robust response reproducible across our child participants and the most likely to reflect a motor-to-auditory relation. Both children who do and do not stutter demonstrated speech-induced suppression of the auditory M50. However, children who stutter had a delayed auditory M50 peak latency to vowel sounds compared to children who do not stutter indicating a possible deficiency in their ability to efficiently integrate auditory speech information for the purpose of establishing neural representations of speech sounds.

Figure 1

(A) Group averaged source images of the auditory evoked magnetic fields in response to a 1kHz tone overlaid on the MNI canonical brain. The associated MNI coordinates are listed in Table 2. (B) Group averaged source magnitude variations from 200ms prestimulus to 800 ms post stimulus corresponding to those sources. (C) A detailed view of the early components. The solid and dotted lines represent the control participants and children who stutter respectively. nAm = nanoAmpere*meters; ms = milliseconds; Blue = left hemisphere (LH); Red = right hemisphere (RH).

Figure 2

The results of the listen tone task (A) amplitude and (B) latency analyses. No differences were found in the amplitude or latency of the M50 in response to a 1kHz tone in children who stutter relative to the control participants. Error bars represent the 95% confidence interval.

Figure 3

(A) Group averaged source images of the auditory evoked magnetic fields for the listen vowel task overlaid on the MNI canonical brain. The associated MNI coordinates are listed in Table 2. (B) Group averaged source magnitude variations from 200ms prestimulus to 800 ms post stimulus corresponding to those sources and (C) a detailed view of the early components.

Figure 4

(A) Group averaged source images of the auditory evoked magnetic fields for the speak vowel task overlaid on the MNI canonical brain. The associated MNI coordinates are listed in Table 2. (B) Group averaged source magntiude variations from 200ms prestimulus to 800 ms post stimulus corresponding to those sources and (C) a detailed view of the early components.

Figure 5

The results of the listen vowel and speak vowel amplitude analysis. On average, the control participants and children who stutter demonstrated a 59% reduction in M50 amplitude for the speak vowel condition relative to the listen vowel condition. Error bars represent the 95% confidence interval.

Figure 6

For children who stutter, left hemisphere amplitude for the speak task had a negative correlation with stuttering severity as measured with the SSI-3.

Figure 7

The results of the listen and speak vowel task latency analysis. The children who stutter had delayed M50 peak latencies for the listen vowel and speak vowel tasks relative to the control participants. Error bars represent the 95% confidence interval.

Fig. 8

The children who stutter had a 9.92 ms delay in M50 peak latency for vowel tasks relative to the control participants. Error bars represent the 95% confidence interval.