Slide Slam D12
How much is enough: Atypical gamma responses in children with phonological disorders
Alycia Cummings1, Ying Wu2, Diane Ogiela1; 1Idaho State University - Meridian, 2University of California, San Diego
Introduction It is unknown what underlying mechanisms might account for the problems children with phonological disorders (PD) encounter during speech production. One possible explanation is poorly specified phonological representations. We previously examined phonological specification of place of articulation features in /bɑ/ ([labial]) and /dɑ/ ([coronal]) in typically developing (TD) versus PD children using an event-related potential (ERP) paradigm (Cummings et al., 2020). PD children exhibited less mature ERP responses relative to their TD counterparts. The present study examined neural oscillation patterns to specified and underspecified phonemes using the same EEG data of Cummings et al. 2020. The goal was to examine developmental differences in theta and/or low gamma event-related spectral perturbation responses in TD and PD children. As ERPs elicited by /bɑ/ and /dɑ/ differed between groups, it was predicted that the neural oscillation patterns underlying those responses would also be distinct. Methods Participants. Twenty-four native English-speaking children participated: 12 typically developing (TD) children (9 male, 4.58-6.92 years) and 12 children with phonological disorders (PD) (6 male, 4.00-6.92 years). Stimuli and Procedure. Two oddball stimulus sets, each containing four consonant-vowel (CV) syllables - one standard (/bɑ/ or /dɑ/) and three deviants (/bɑ/ or /dɑ/, /pɑ/, /gɑ/) - were presented in five blocks. Sixty-six channels of continuous EEG were recorded at 256 Hz. EEG Analyses. Event-related spectral perturbation (ERSP) analyses examined theta (4-7 Hz) and low gamma (25-35 Hz) band activity elicited by /bɑ/ and /dɑ/ standard and deviant syllable stimuli. ERSPs were computed from time-series data from 16 electrodes. Theta was measured in one window from 100-300 ms, while low gamma was measured in five 50 ms windows (50-300 ms). Phoneme-related differences were examined in Group (TD, PD) x Phoneme (/bɑ/, /dɑ/) repeated measures ANOVAs. Results ERSP Low Gamma Band Power. Between groups, TD children demonstrated greater low gamma activation in response to /bɑ/ standards as compared to PD children (F(1,22) = 4.330, p < .05, 2 = .164). PD children demonstrated greater low gamma activation to /dɑ/ standards than did TD children (F(1,22) = 2.970, p = .099, 2 = .119). Within the PD children, greater low gamma activation to /dɑ/ standards than /bɑ/ standards (F(1,11) = 4.834, p = .050, 2 = .305) was observed. Discussion The cortical systems mediating phonological processing in PD children exhibited a different pattern of engagement from that observed in TD counterparts. PD children demonstrated excessive synchronization in response to /dɑ/, suggesting their phonological representations were less detailed than those of TD children (Lehongre et al., 2011). Conversely, PD children demonstrated arguably excessive desynchronization in response to /bɑ/, suggesting they were processing too much information and not attending to the phoneme’s distinctive features (Hanslmayr et al., 2012). This atypical pattern of cortical response to acoustic-phonological information in PD children might underlie their inability to accurately produce phonemes (Goswami, 2011). That is, these processing patterns might result in PD children storing imprecise, excessive, and/or inaccurate feature details in their phonological representations, which when accessed during speech production, would result in incorrect productions.