Dataset Information

Neural mechanisms supporting robust discrimination of spectrally and temporally degraded speech.

ABSTRACT: Cochlear implants provide good speech discrimination ability despite highly limited amount of information they transmit compared with normal cochlea. Noise vocoded speech, simulating cochlear implants in normal hearing listeners, have demonstrated that spectrally and temporally degraded speech contains sufficient cues to provide accurate speech discrimination. We hypothesized that neural activity patterns generated in the primary auditory cortex by spectrally and temporally degraded speech sounds will account for the robust behavioral discrimination of speech. We examined the behavioral discrimination of noise vocoded consonants and vowels by rats and recorded neural activity patterns from rat primary auditory cortex (A1) for the same sounds. We report the first evidence of behavioral discrimination of degraded speech sounds by an animal model. Our results show that rats are able to accurately discriminate both consonant and vowel sounds even after significant spectral and temporal degradation. The degree of degradation that rats can tolerate is comparable to human listeners. We observed that neural discrimination based on spatiotemporal patterns (spike timing) of A1 neurons is highly correlated with behavioral discrimination of consonants and that neural discrimination based on spatial activity patterns (spike count) of A1 neurons is highly correlated with behavioral discrimination of vowels. The results of the current study indicate that speech discrimination is resistant to degradation as long as the degraded sounds generate distinct patterns of neural activity.

SUBMITTER: Ranasinghe KG

PROVIDER: S-EPMC3387312 | biostudies-literature | 2012 Aug

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Neural mechanisms supporting robust discrimination of spectrally and temporally degraded speech.

Ranasinghe Kamalini G KG Vrana William A WA Matney Chanel J CJ Kilgard Michael P MP

Journal of the Association for Research in Otolaryngology : JARO 20120502 4

Cochlear implants provide good speech discrimination ability despite highly limited amount of information they transmit compared with normal cochlea. Noise vocoded speech, simulating cochlear implants in normal hearing listeners, have demonstrated that spectrally and temporally degraded speech contains sufficient cues to provide accurate speech discrimination. We hypothesized that neural activity patterns generated in the primary auditory cortex by spectrally and temporally degraded speech sound ...[more]

PMID: 22549175

Similar Datasets

Project description:IntroductionCochlear implants (CIs) are the treatment of choice for severe to profound hearing loss. Variability in CI outcomes remains despite advances in technology and is attributed in part to differences in cortical processing. Studying these differences in CI users is technically challenging. Spectrally degraded stimuli presented to normal-hearing individuals approximate input to the central auditory system in CI users. This study used intracranial electroencephalography (iEEG) to investigate cortical processing of spectrally degraded speech.MethodsParticipants were adult neurosurgical epilepsy patients. Stimuli were utterances /aba/ and /ada/, spectrally degraded using a noise vocoder (1-4 bands) or presented without vocoding. The stimuli were presented in a two-alternative forced choice task. Cortical activity was recorded using depth and subdural iEEG electrodes. Electrode coverage included auditory core in posteromedial Heschl's gyrus (HGPM), superior temporal gyrus (STG), ventral and dorsal auditory-related areas, and prefrontal and sensorimotor cortex. Analysis focused on high gamma (70-150 Hz) power augmentation and alpha (8-14 Hz) suppression.ResultsChance task performance occurred with 1-2 spectral bands and was near-ceiling for clear stimuli. Performance was variable with 3-4 bands, permitting identification of good and poor performers. There was no relationship between task performance and participants demographic, audiometric, neuropsychological, or clinical profiles. Several response patterns were identified based on magnitude and differences between stimulus conditions. HGPM responded strongly to all stimuli. A preference for clear speech emerged within non-core auditory cortex. Good performers typically had strong responses to all stimuli along the dorsal stream, including posterior STG, supramarginal, and precentral gyrus; a minority of sites in STG and supramarginal gyrus had a preference for vocoded stimuli. In poor performers, responses were typically restricted to clear speech. Alpha suppression was more pronounced in good performers. In contrast, poor performers exhibited a greater involvement of posterior middle temporal gyrus when listening to clear speech.DiscussionResponses to noise-vocoded speech provide insights into potential factors underlying CI outcome variability. The results emphasize differences in the balance of neural processing along the dorsal and ventral stream between good and poor performers, identify specific cortical regions that may have diagnostic and prognostic utility, and suggest potential targets for neuromodulation-based CI rehabilitation strategies.

Project description:ObjectivesNormally-hearing (NH) listeners rely more on prosodic cues than on lexical-semantic cues for emotion perception in speech. In everyday spoken communication, the ability to decipher conflicting information between prosodic and lexical-semantic cues to emotion can be important: for example, in identifying sarcasm or irony. Speech degradation in cochlear implants (CIs) can be sufficiently overcome to identify lexical-semantic cues, but the distortion of voice pitch cues makes it particularly challenging to hear prosody with CIs. The purpose of this study was to examine changes in relative reliance on prosodic and lexical-semantic cues in NH adults listening to spectrally degraded speech and adult CI users. We hypothesized that, compared with NH counterparts, CI users would show increased reliance on lexical-semantic cues and reduced reliance on prosodic cues for emotion perception. We predicted that NH listeners would show a similar pattern when listening to CI-simulated versions of emotional speech.DesignSixteen NH adults and 8 postlingually deafened adult CI users participated in the study. Sentences were created to convey five lexical-semantic emotions (angry, happy, neutral, sad, and scared), with five sentences expressing each category of emotion. Each of these 25 sentences was then recorded with the 5 (angry, happy, neutral, sad, and scared) prosodic emotions by 2 adult female talkers. The resulting stimulus set included 125 recordings (25 Sentences × 5 Prosodic Emotions) per talker, of which 25 were congruent (consistent lexical-semantic and prosodic cues to emotion) and the remaining 100 were incongruent (conflicting lexical-semantic and prosodic cues to emotion). The recordings were processed to have 3 levels of spectral degradation: full-spectrum, CI-simulated (noise-vocoded) to have 8 channels and 16 channels of spectral information, respectively. Twenty-five recordings (one sentence per lexical-semantic emotion recorded in all five prosodies) were used for a practice run in the full-spectrum condition. The remaining 100 recordings were used as test stimuli. For each talker and condition of spectral degradation, listeners indicated the emotion associated with each recording in a single-interval, five-alternative forced-choice task. The responses were scored as proportion correct, where "correct" responses corresponded to the lexical-semantic emotion. CI users heard only the full-spectrum condition.ResultsThe results showed a significant interaction between hearing status (NH, CI) and congruency in identifying the lexical-semantic emotion associated with the stimuli. This interaction was as predicted, that is, CI users showed increased reliance on lexical-semantic cues in the incongruent conditions, while NH listeners showed increased reliance on the prosodic cues in the incongruent conditions. As predicted, NH listeners showed increased reliance on lexical-semantic cues to emotion when the stimuli were spectrally degraded.ConclusionsThe present study confirmed previous findings of prosodic dominance for emotion perception by NH listeners in the full-spectrum condition. Further, novel findings with CI patients and NH listeners in the CI-simulated conditions showed reduced reliance on prosodic cues and increased reliance on lexical-semantic cues to emotion. These results have implications for CI listeners' ability to perceive conflicts between prosodic and lexical-semantic cues, with repercussions for their identification of sarcasm and humor. Understanding instances of sarcasm or humor can impact a person's ability to develop relationships, follow conversation, understand vocal emotion and intended message of a speaker, following jokes, and everyday communication in general.

Project description:Non-fluent speech is one of the most common impairments in post-stroke aphasia. The rehabilitation of non-fluent speech in aphasia is particularly challenging as patients are rarely able to produce and practice fluent speech production. Speech entrainment is a behavioural technique that enables patients with non-fluent aphasia to speak fluently. However, its mechanisms are not well understood and the level of improved fluency with speech entrainment varies among individuals with non-fluent aphasia. In this study, we evaluated the behavioural and neuroanatomical factors associated with better speech fluency with the aid of speech entrainment during the training phase of speech entrainment. We used a lesion-symptom mapping approach to define the relationship between chronic stroke location on MRI and the number of different words per second produced during speech entrainment versus picture description spontaneous speech. The behavioural variable of interest was the speech entrainment/picture description ratio, which, if ≥1, indicated an increase in speech output during speech entrainment compared to picture description. We used machine learning (shallow neural network) to assess the statistical significance and out-of-sample predictive accuracy of the neuroanatomical model, and its regional contributors. We observed that better assisted speech (higher speech entrainment/picture description ratio) was achieved by individuals who had preservation of the posterior middle temporal gyrus, inferior fronto-occipital fasciculus and uncinate fasciculus, while exhibiting lesions in areas typically associated with non-fluent aphasia, such as the superior longitudinal fasciculus, precentral, inferior frontal, supramarginal and insular cortices. Our findings suggest that individuals with dorsal stream damage but preservation of ventral stream structures are more likely to achieve more fluent speech with the aid of speech entrainment compared to spontaneous speech. This observation provides insight into the mechanisms of non-fluent speech in aphasia and has potential implications for future research using speech entrainment for rehabilitation of non-fluent aphasia.

Dataset Information

Neural mechanisms supporting robust discrimination of spectrally and temporally degraded speech.

Publications

Neural mechanisms supporting robust discrimination of spectrally and temporally degraded speech.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets