Speech Processing In Individuals Research Articles

Music as a scaffold for listening to speech: Better neural phase-locking to song than speech

Neural activity synchronizes with the rhythmic input of many environmental signals, but the capacity of neural activity to entrain to the slow rhythms of speech is particularly important for successful communication. Compared to speech, song has greater rhythmic regularity, a more stable fundamental frequency, discrete pitch movements, and a metrical structure, this may provide a temporal framework that helps listeners neurally track information better than the rhythmically irregular rhythms of speech. The current study used EEG to examine whether entrainment to the syllable rate of linguistic utterances, as indexed by cerebro-acoustic phase coherence, was greater when listeners heard sung than spoken sentences. We assessed listeners phase-locking in both easy (no time compression) and hard (50% time-compression) utterance conditions. Adults phase-locked equally well to speech and song in the easy listening condition. However, in the time-compressed condition, phase-locking was greater for sung than spoken utterances in the theta band (3.67–5 ​Hz). Thus, the musical temporal and spectral characteristics of song related to better phase-locking to the slow phrasal and syllable information (4–7 ​Hz) in the speech stream. These results highlight the possibility of using song as a tool for improving speech processing in individuals with language processing deficits, such as dyslexia.

Auditory brainstem response to speech in children with high functional autism spectrum disorder.

Auditory brainstem response (ABR) provides useful information about the auditory brainstem pathway. However, there is little known about the subcortical speech processing in individuals with autism spectrum disorder (ASD). The aim of the present study was to investigate the subcortical speech processing in children with high functioning ASD. Twenty-eight children with ASD, with a mean age of 14.36 ± 1.86, and 28 typically developing (TD) children, with a mean age of 14.99 ± 1.92, were selected from Rofeydeh Rehabilitation Hospital (Tehran, Iran), and speech ABR (sABR) with a 40ms synthetic /da/ syllable stimulus was recorded. There was no significant difference between the two groups in terms of age and IQ. Latencies of all waves in sABR and duration of V-A complex were significantly longer in children with ASD than in TD children. It was concluded that patients with ASD have deficits in the temporal neural encoding of speech at the brainstem level. Further studies are needed to generalize this result.

Cortical processing of speech in individuals with auditory neuropathy spectrum disorder

Auditory neuropathy spectrum disorder (ANSD) is a condition where cochlear amplification function (involving outer hair cells) is normal but neural conduction in the auditory pathway is disordered. This study was done to investigate the cortical representation of speech in individuals with ANSD and to compare it with the individuals with normal hearing. Forty-five participants including 21 individuals with ANSD and 24 individuals with normal hearing were considered for the study. Individuals with ANSD had hearing thresholds ranging from normal hearing to moderate hearing loss. Auditory cortical evoked potentials-through odd ball paradigm-were recorded using 64 electrodes placed on the scalp for /ba/-/da/ stimulus. Onset cortical responses were also recorded in repetitive paradigm using /da/ stimuli. Sensitivity and reaction time required to identify the oddball stimuli were also obtained. Behavioural results indicated that individuals in ANSD group had significantly lower sensitivity and longer reaction times compared to individuals with normal hearing sensitivity. Reliable P300 could be elicited in both the groups. However, a significant difference in scalp topographies was observed between the two groups in both repetitive and oddball paradigms. Source localization using local auto regressive analyses revealed that activations were more diffuses in individuals with ANSD when compared to individuals with normal hearing sensitivity. Results indicated that the brain networks and regions activated in individuals with ANSD during detection and discrimination of speech sounds are different from normal hearing individuals. In general, normal hearing individuals showed more focused activations while in individuals with ANSD activations were diffused.

Can we Measure Speech Perception Ability Objectively in Young Children using Cochlear Implant?

Speech perception plays a significant role in the development of speech and language ability in children with hearing loss. There are various speech perception tests with the specific protocol to administer and score. Auditory evoked potential is an objective measure used for assessing hearing acuity in young children. Higher cortical evoked potential test provides an effective indication of the physiological status of auditory cortex. CEAP can be obtained in young children with assistive devices. The present research study aims to investigate whether latency and amplitude of aided cortical evoked potential can predict Speech perception score in cochlear implant users. 52 cochlear implant users and 102 typical children were tested. The mean age for children using cochlear implant was 8.05 years, standard deviation 1.4. The normal hearing group had a mean age of 8.12 years and standard deviation 1.46. Cochlear implant users were having at least 15 active electrodes. Speech stimulus was used with 100 ms duration, 20 ms rise/fall, 20 ms plateau tones. The inter-stimulus interval was kept at 1125 ms. During statistical analysis of data, CEAP P1 latencies and speech perception scores were found to be related. A further regression equation was obtained. The present study reveals speech stimuli can evoke distinct neural response patterns from auditory cortex. The present research study also helps in understanding the neural processing of speech in individuals with hearing impairment using Cochlear implant. Statistical analysis of data CEAP P1 latency and speech perception score regression equation were obtained. The result reveals that speech stimuli can evoke distinct neural response patterns from auditory cortex. CEAP finding support speech perception ability and auditory evoked potential help to the study of neural processing of speech in individuals with the cochlear implant. The evoked potential and speech perception ability has a significant relation between them.

The impact of parkinson's disease on the cortical mechanisms that support auditory-motor integration for voice control.

Several studies have shown sensorimotor deficits in speech processing in individuals with idiopathic Parkinson's disease (PD). The underlying neural mechanisms, however, remain poorly understood. In the present event-related potential (ERP) study, 18 individuals with PD and 18 healthy controls were exposed to frequency-altered feedback (FAF) while producing a sustained vowel and listening to the playback of their own voice. Behavioral results revealed that individuals with PD produced significantly larger vocal compensation for pitch feedback errors than healthy controls, and exhibited a significant positive correlation between the magnitude of their vocal responses and the variability of their unaltered vocal pitch. At the cortical level, larger P2 responses were observed for individuals with PD compared with healthy controls during active vocalization due to left-lateralized enhanced activity in the superior and inferior frontal gyrus, premotor cortex, inferior parietal lobule, and superior temporal gyrus. These two groups did not differ, however, when they passively listened to the playback of their own voice. Individuals with PD also exhibited larger P2 responses during active vocalization when compared with passive listening due to enhanced activity in the inferior frontal gyrus, precental gyrus, postcentral gyrus, and middle temporal gyrus. This enhancement effect, however, was not observed for healthy controls. These findings provide neural evidence for the abnormal auditory-vocal integration for voice control in individuals with PD, which may be caused by their deficits in the detection and correction of errors in voice auditory feedback. Hum Brain Mapp 37:4248-4261, 2016. © 2016 Wiley Periodicals, Inc.

Subcortical processing of speech in individuals with type 2 diabetes mellitus

The study was done to compare speech-evoked auditory brainstem response (ABR) in normal-hearing individuals without diabetes mellitus and normal-hearing individuals with type 2 diabetes mellitus (T2DM). A case-control study design was used to carry out the study. A total of 50 individuals were recruited in the study, divided into two groups. One group consisted of 25 individuals with type 2 diabetes mellitus with normal-hearing and the other group consisted of 25 individuals without diabetes with normal hearing as a control group. The results indicated that the mean latencies and amplitudes was significantly different in the type 2 diabetes mellitus group in comparison to the control group. The amplitude of the F0, F1, higher formants, and RMS values were higher in the control group when compared to the T2DM group. The present study concluded that there is problem in the encoding of speech at the brainstem level despite normal hearing in individuals with type 2 diabetes mellitus.

Binaural speech processing in individuals with auditory neuropathy

Auditory neuropathy disrupts the neural representation of sound and may therefore impair processes contingent upon inter-aural integration. The aims of this study were to investigate binaural auditory processing in individuals with axonal (Friedreich ataxia) and demyelinating (Charcot–Marie–Tooth disease type 1A) auditory neuropathy and to evaluate the relationship between the degree of auditory deficit and overall clinical severity in patients with neuropathic disorders.Twenty-three subjects with genetically confirmed Friedreich ataxia and 12 subjects with Charcot–Marie–Tooth disease type 1A underwent psychophysical evaluation of basic auditory processing (intensity discrimination/temporal resolution) and binaural speech perception assessment using the Listening in Spatialized Noise test. Age, gender and hearing-level-matched controls were also tested.Speech perception in noise for individuals with auditory neuropathy was abnormal for each listening condition, but was particularly affected in circumstances where binaural processing might have improved perception through spatial segregation. Ability to use spatial cues was correlated with temporal resolution suggesting that the binaural-processing deficit was the result of disordered representation of timing cues in the left and right auditory nerves. Spatial processing was also related to overall disease severity (as measured by the Friedreich Ataxia Rating Scale and Charcot–Marie–Tooth Neuropathy Score) suggesting that the degree of neural dysfunction in the auditory system accurately reflects generalized neuropathic changes.Measures of binaural speech processing show promise for application in the neurology clinic. In individuals with auditory neuropathy due to both axonal and demyelinating mechanisms the assessment provides a measure of functional hearing ability, a biomarker capable of tracking the natural history of progressive disease and a potential means of evaluating the effectiveness of interventions.

Audiovisual speech integration in autism spectrum disorders: ERP evidence for atypicalities in lexical-semantic processing.

In typically developing (TD) individuals, behavioral and event-related potential (ERP) studies suggest that audiovisual (AV) integration enables faster and more efficient processing of speech. However, little is known about AV speech processing in individuals with autism spectrum disorders (ASD). This study examined ERP responses to spoken words to elucidate the effects of visual speech (the lip movements accompanying a spoken word) on the range of auditory speech processing stages from sound onset detection to semantic integration. The study also included an AV condition, which paired spoken words with a dynamic scrambled face in order to highlight AV effects specific to visual speech. Fourteen adolescent boys with ASD (15-17 years old) and 14 age- and verbal IQ-matched TD boys participated. The ERP of the TD group showed a pattern and topography of AV interaction effects consistent with activity within the superior temporal plane, with two dissociable effects over frontocentral and centroparietal regions. The posterior effect (200-300 ms interval) was specifically sensitive to lip movements in TD boys, and no AV modulation was observed in this region for the ASD group. Moreover, the magnitude of the posterior AV effect to visual speech correlated inversely with ASD symptomatology. In addition, the ASD boys showed an unexpected effect (P2 time window) over the frontocentral region (pooled electrodes F3, Fz, F4, FC1, FC2, FC3, FC4), which was sensitive to scrambled face stimuli. These results suggest that the neural networks facilitating processing of spoken words by visual speech are altered in individuals with ASD.

Test-retest reliability of cortical evoked potentials using naturally produced speech sounds.

To determine if naturally produced speech stimuli evoke distinct neural response patterns that can be reliably recorded in individuals. Auditory cortical evoked potentials were obtained from seven normal-hearing young adults in response to four naturally produced speech tokens (/bi/, /pi/, /[U0283]i/, and /si/). Stimuli were tokens from the standardized UCLA version of the Nonsense Syllable Test (NST) ( Dubno & Schaefer, 1992). Using a repeated measures design, subjects were tested and then retested within an 8-day period. Auditory cortical evoked potentials elicited by naturally produced speech sounds were reliably recorded in individuals. Also, naturally produced speech tokens, representing different acoustic cues, evoked distinct neural response patterns. 1) Cortical evoked potentials elicited by naturally produced speech sounds can be reliably recorded in individuals. 2) Naturally produced speech tokens, representing different acoustic cues, evoke distinct neural response patterns. 3) Given the reliability of the response, this work has potential application to the study of neural processing of speech in individuals with communication disorders as well as changes over time after various types of auditory rehabilitation.