Poster B75, Tuesday, August 20, 2019, 3:15 – 5:00 pm, Restaurant Hall
Native-language experience reflected in low gamma, theta and delta frequency bands.
Monica Wagner1, Silvia Ortiz-Mantilla2, Valerie Shafer3, April Benasich2;1St. John's University, 2Rutgers University, 3The Graduate Center of the City University of New York
It has been proposed that discontinuities within the temporal structure of speech are tracked at multiple time scales in auditory cortex, with syllables of approximately 200 ms duration tracked at ~5 Hz and phonemes of approximately 25 ms duration tracked at faster rates at ~40 Hz. This processing is hierarchically nested, with delta oscillations modulating theta, which, in turn, regulates gamma activity. Phase locking in the theta band to discretized units associated with syllables has been demonstrated, however, phase locking to phoneme level segmentations has been elusive. It is possible that entrainment to phonological sequences is obscured by lexical level processing of meaningful spoken words. Thus, the aim of the study was to determine whether increased measures of inter-trial phase locking (ITPL) within the electroencephalogram (EEG) would be found in the low gamma (LG) frequency band ~40 Hz for native-language phonological sequences within nonwords, but not for non-native sequences. EEGs were obtained from 24 native-English monolingual and 24 native-Polish bilingual adults while they listened to same and different nonword pairs during two counterbalanced conditions, an attend and a passive listening condition. Nonwords within the pairs contained the phonological sequences onsets /sət/, /st/, /pət/ and /pt/ that occur in the Polish and English languages with the exception of /pt/, which never occurs in English in word onset. A three-dipole source model, fit at the time intervals for the N1 and P2 components, was created for the English and Polish groups, separately. The models, which identified sources in left auditory cortex (LAC), right auditory cortex (RAC) and an anterior-central (AC) source, explained 90% of the data variance for each group. Single-trial data segmented between -100 to 900 ms was transformed into the time-frequency domain between 2-90 Hz, using a 1 Hz wide frequency bin and 50 ms time resolution. Cluster analysis, in combination with permutation testing, was used to compare the language groups’ measures of temporal spectral evolution (TSE) and ITPL from the three sources. These measures of spectral power and phase synchrony were analyzed between 50 to 450 ms in LG (30-58 Hz) and the low-frequency range (2-30 Hz) for the attend and passive conditions to each word type (e.g., /sət/), separately. Increased ITPL values, without increases in power, were found for the Polish compared to the English group to the /pt/ onsets in nonwords in the LG subband ~30-40 Hz. These effects were found bilaterally in LAC and RAC. Language group differences in LG to /sət/, /st/, and /pət/ onsets that occur in both languages were not found. Thus, phase resetting to discontinuities within the acoustic structures that correspond to a phonological sequence may be a feasible mechanism for enhancing linguistic information in auditory cortical pathways. Also, increased ITPL values for the Polish listeners were observed in the delta-theta frequency band to all sequences in RAC and LAC with one notable exception; no differences were found to /pt/ in LAC. These results suggest that experience with phonological sequences modulates phase resetting in the LG, delta and theta frequency bands.
Themes: Speech Perception, Phonology and Phonological Working Memory
Method: Electrophysiology (MEG/EEG/ECOG)