Investigation of the neural discrimination of acoustic characteristics of speech sounds in normal-hearing individuals through Frequency-following Response (FFR)

Rocha-Muniz, Caroline Nunes; Schochat, Eliane

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Sumário

Original Article • CoDAS 33 (1) • 2021 • https://doi.org/10.1590/2317-1782/20202018324 copy

Investigation of the neural discrimination of acoustic characteristics of speech sounds in normal-hearing individuals through Frequency-following Response (FFR)

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

Purpose

To evaluate how the auditory pathways encode and discriminate the plosive syllables [ga], [da] and [ba] using the auditory evoked Frequency-following Response (FFR) in children with typical development.

Methods

Twenty children aged 6-12 years were evaluated using the FFR for the [ga], [da] and [ba] stimuli. The stimuli were composed of six formants and were differentiated in the F2 to F3 transition (transient portion). The other formants were identical in the three syllables (sustained portion). The latencies of the 16 waves of the transient portion (<70ms) and of the 21 waves of the sustained portion (90-160ms) of the stimuli were analyzed in the neural responses obtained for each of the syllables.

Results

The transient portion latencies were different in the three syllables, indicating a distinction in the acoustic characteristics of these syllables through their neural representations. In addition, the transient portion latencies progressively increased in the following order: [ga] <[da] <[ba], whereas no significant differences were observed in the sustained portion.

Conclusion

The FFR proved to be an efficient tool to investigate the subcortical acoustic differences in speech sounds, since it demonstrated different electrophysiological responses for the three evoked syllables. Changes in latency were observed in the transient portion (consonants) but not in the sustained portion (vowels) for the three stimuli. These results indicate the neural ability to distinguish between acoustic characteristics of the [ga], [da] and [ba] stimuli.

Keywords
Audiology; Electrophysiology; Auditory Pathways; Auditory Perception; Speech Perception

Stimulus Formant Frequencies
	F_o	F₁		F₂		F₃		F₄	F₅	F₆
	Flat	Onset	Steady-state	Onset	Steady-state l	Onset	Steady-state	Flat	Flat	Flat
[ga]	100	400	720	3000	1240	3100	2500	3300	3750	4900
[da]	100	400	720	1700	1240	2580	2500	3300	3750	4900
[ba]	100	400	720	900	1240	2400	2500	3300	3750	4900

		1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16
Peak latency (ms)
[ga]	Mean	8.10	9.00	21.27	22.48	24.26	31.53	32.70	34.50	41.79	43.11	44.58	51.75	53.19	54.82	62.10	63.39
	SD	0.43	0.78	0.49	0.66	0.79	0.45	0.56	0.69	0.50	0.71	0.84	0.66	1.21	0.90	0.82	0.97
	N	20	19	20	20	18	20	20	14	20	20	15	20	20	15	20	20
[da]	Mean	8.03	9.25	21.78	22.81	24.57	31.78	32.96	34.90	41.72	42.91	44.78	51.83	53.12	55.02	61.94	63.23
	SD	0.38	0.59	0.82	0.82	1.19	0.51	0.59	0.87	0.51	0.55	0.93	0.84	0.97	0.91	0.97	1.10
	N	20	20	20	20	17	20	20	16	20	20	15	20	20	18	20	20
[ba]	Mean	8.24	9.57	22.04	23.19	25.07	32.21	33.43	35.23	42.00	43.31	45.24	52.00	53.24	55.28	62.01	63.39
	SD	0.50	0.49	0.99	0.86	0.91	0.47	0.47	0.85	0.48	0.56	0.81	1.00	1.06	1.10	0.98	1.09
	N	20	20	18	19	15	20	20	13	20	20	19	20	20	17	20	20

Waves	p-value
Waves	/ga/ vs. /ba/		/da/ vs. /ba/		/ga/ vs. /da/
	t	p	t	p	t	p
3	-4.54	<0.001*	-1.49	0.154	4.35	<0.001 ^* * Statistically significant;
4	-4.71	<0.001*	-2.40	0.002*	3.17	0.005*
6	-8.852	<0.001*	-6.981	<0.001*	0.432	0.007*
7	-8.713	<0.001*	-3.708	0.001*	2.358	0.03*
9	-3.203	0.005*	-5.653	<0.001*	-1.172	0.26*
10	-1.478	0.16	-4.693	<0.001*	-1.803	0.09^# # Marginally significant;
12	-1.355	0.19	-2.492	0.02*	0.481	0.64
13	-0.223	0.83	-1.39	0.18	-0.302	0.77

Waves	p-value
Waves	/ga/ vs. /ba/		/da/ vs. /ba/		/ga/ vs. /da/
	t	p	t	p	t	p
5	-4.71	<0.001*	-2.40	0.027 ^* * Statistically significant; t = t-value; p= p=value	3.17	0.005*
8	-5.01	0.001*	-1.42	0.19	1.74	0.1
11	-4.45	0.001*	-2.51	0.026*	0.88	0.40
14	-2.73	0.019*	-3.34	0.005*	1.91	0.08

Waves	p-value
Waves	/ga/ vs. /ba/		/da/ vs. /ba/		/ga/ vs. /da/
	t	p	t	p	t	p
15	1.68	0.11	-2.38	0.03 ^* * Statistically significant; t = t-value; p= p=value	-2.811	0.01*
16	0.03	0.97	-2.33	0.03*	-2.58	0.02*

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[1] Conflict of interests: nothing to declare.