Biomedical subjects

Jeffery A Jones

Publications and source records attributed to Jeffery A Jones.

10 recordsLinked to original sources

PubMed2006

Multisensory integration of speech signals: the relationship between space and time.

Integrating audiovisual cues for simple events is affected when sources are separated in space and time. By contrast, audiovisual perception of speech appears resilient when either spatial or temporal disparities exist. We investigated whether speech perception is sensitive to the combination of spatial and temporal inconsistencies. Participants heard the bisyllable /aba/ while seeing a face produce the incongruent bisyllable /ava/. We tested the level of visual influence over auditory perception when the sound was asynchronous with respect to facial motion (from -360 to +360 ms) and emanated from five locations equidistant to the participant. Although an interaction was observed, it was not related to participants' perception of synchrony, nor did it indicate a linear relationship between the effect of spatial and temporal discrepancies. We conclude that either the complexity of the signal or the nature of the task reduces reliance on spatial and temporal contiguity for audiovisual speech perception.

Acoustic Stimulation↗

PubMed2006

Expression of matrix metalloproteinases and endogenous inhibitors within ascending aortic aneurysms of patients with Marfan syndrome.

BACKGROUND: Marfan syndrome (MFS) is known to cause ascending thoracic aortic aneurysms (ATAAs). Transforming growth factor beta (TGF-beta) has recently been implicated in this process. Imbalances between the matrix metalloproteinases (MMPs) and their endogenous inhibitors (TIMPs) have also been shown to contribute to aneurysm formation. Whether and to what degree MMP, TIMP, and TGF-beta signaling profiles are altered in ATAAs in MFS compared with non-MFS patients remains unknown. METHODS AND RESULTS: ATAA samples taken during aortic replacement from age-matched MFS (n=9) and non-MFS (n=18) patients were assessed for representative subtypes of all MMP classes, all 4 known TIMPs, and type 2 TGF-beta receptors (TGFBR2). Results were expressed as a percentage (mean+/-SEM) of reference control samples (100%; n=18) obtained from patients without ATAA. In MFS, decreased MMP-2 (76+/-7; P<0.05 versus control), increased MMP-12 (161+/-27% versus control; P<0.05), and increased MT1-MMP (248+/-64% versus 91+/-21 non-MFS and control; P<0.05) were observed. TIMP-3 (74+/-23%) was reduced compared with control values (P<0.05) and TIMP-2 was elevated (128+/-31%) compared with non-MFS (73+/-19%; P<0.05). In non-MFS samples, MMP-1 (70+/-16%), MMP-3 (77+/-18%), MMP-8 (75+/-11%), MMP-9 (69+/-14%), and MMP-12 (85+/-15%) were decreased compared with control (P<0.05). TIMPs 1 to 3 were reduced in non-MFS compared with control values (P<0.05). TGFBR2 were increased in MFS (193+/-32%) compared with non-MFS (95+/-16%) and controls (P<0.05). CONCLUSIONS: A unique MMP and TIMP portfolio was observed in ATAAs from MFS compared with non-MFS patients. In addition, MFS samples showed evidence of increased TGF-beta signaling. These differences suggest disparate mechanisms of extracellular matrix remodeling between these 2 groups of patients.

Adult↗

PubMed2006

Temporal disparity in the induction of matrix metalloproteinases and tissue inhibitors of metalloproteinases after thoracic aortic aneurysm formation.

BACKGROUND: An important component of matrix remodeling during thoracic aortic aneurysm progression is the balance between matrix metalloproteinases and their endogenous inhibitors (tissue inhibitors of metalloproteinases). However, whether and to what degree matrix metalloproteinase/tissue inhibitor of metalloproteinases profiles change over time with an evolving thoracic aortic aneurysm remains unclear. METHODS: Descending thoracic aortic aneurysms were induced in mice (FVB strain, 15 minutes of 0.5 mol/L CaCl2 exposure) and followed for 24 hours, 72 hours, 1 week, 2 weeks, 4 weeks, or 8 weeks (each group, n = 13). Thoracic aortic aneurysm size was determined by means of video micrometry, and immunoblotting was used to measure aortic matrix metalloproteinase 2, 8, 9, and 12 and tissue inhibitor of metalloproteinases 1 and 4 levels (expressed as a percentage of control values, n = 13). RESULTS: Increased aortic diameter was detected by 72 hours and reached a maximal size at 4 weeks (135% +/- 4% increase from baseline, P < .05), which is consistent with thoracic aortic aneurysm progression. Active matrix metalloproteinase 8 (collagenase) levels increased at 72 hours (178% +/- 49%, P < .05 from control), and active matrix metalloproteinase 12 (elastase) levels increased by 24 hours (138% +/- 11%, P < .05), whereas active matrix metalloproteinase 2 levels increased at 72 hours and 1 week after thoracic aortic aneurysm induction (72 hours: 158% +/- 12%, 1 week: 162% +/- 19%; P < .05). At 1 week after thoracic aortic aneurysm induction, active matrix metalloproteinase 9 and 12 levels decrease (matrix metalloproteinase 9: 55% +/- 5%; matrix metalloproteinase 12: 63% +/- 5%; P < .05); however, matrix metalloproteinase 9 and 12 levels were increased from these values at 4 and 8 weeks (P < .05). Tissue inhibitor of metalloproteinases 1 levels were decreased at 1 week (52% +/- 15%, P < .05) and later returned to control values, whereas tissue inhibitor of metalloproteinases 4 levels increased at the late thoracic aortic aneurysm time points (4 weeks: 278% +/- 46%; 8 weeks: 213% +/- 40%; P < .05). CONCLUSIONS: These findings show 2 phases of matrix metalloproteinase abundance during murine thoracic aortic aneurysm formation. The late tissue inhibitor of metalloproteinases 4 increase might explain prevention of further aortic dilation past 4 weeks. Unique matrix metalloproteinase/tissue inhibitor of metalloproteinases temporal relationships occurred during the natural history of thoracic aortic aneurysm progression that might hold both diagnostic and therapeutic relevance.

Animals↗

PubMed2005

Remapping auditory-motor representations in voice production.

Evidence regarding visually guided limb movements suggests that the motor system learns and maintains neural maps between motor commands and sensory feedback. Such systems are hypothesized to be used in a feed-forward control strategy that permits precision and stability without the delays of direct feedback control. Human vocalizations involve precise control over vocal and respiratory muscles. However, little is known about the sensorimotor representations underlying speech production. Here, we manipulated the heard fundamental frequency of the voice during speech to demonstrate learning of auditory-motor maps. Mandarin speakers repeatedly produced words with specific pitch patterns (tone categories). On each successive utterance, the frequency of their auditory feedback was increased by 1/100 of a semitone until they heard their feedback one full semitone above their true pitch. Subjects automatically compensated for these changes by lowering their vocal pitch. When feedback was unexpectedly returned to normal, speakers significantly increased the pitch of their productions beyond their initial baseline frequency. This adaptation was found to generalize to the production of another tone category. However, results indicate that a more robust adaptation was produced for the tone that was spoken during feedback alteration. The immediate aftereffects suggest a global remapping of the auditory-motor relationship after an extremely brief training period. However, this learning does not represent a complete transformation of the mapping; rather, it is in part target dependent.

Acoustic Stimulation↗

PubMed2004

Phonetic perceptual identification by native- and second-language speakers differentially activates brain regions involved with acoustic phonetic processing and those involved with articulatory-auditory/orosensory internal models.

This experiment investigates neural processes underlying perceptual identification of the same phonemes for native- and second-language speakers. A model is proposed implicating the use of articulatory-auditory and articulatory-orosensory mappings to facilitate perceptual identification under conditions in which the phonetic contrast is ambiguous, as in the case of second-language speakers. In contrast, native-language speakers are predicted to use auditory-based phonetic representations to a greater extent for perceptual identification than second-language speakers. The English /r-l/ phonetic contrast, although easy for native English speakers, is extremely difficult for native Japanese speakers who learned English as a second language after childhood. Twenty-two native English and twenty-two native Japanese speakers participated in this study. While undergoing event-related fMRI, subjects were aurally presented with syllables starting with a /r/, /l/, or a vowel and were required to rapidly identify the phoneme perceived by pushing one of three buttons with the left thumb. Consistent with the proposed model, the results show greater activity for second- over native-language speakers during perceptual identification of /r/ and /l/ relative to vowels in brain regions implicated with instantiating forward and inverse articulatory-auditory articulatory-orosensory models [Broca's area, anterior insula, anterior superior temporal sulcus/gyrus (STS/G), planum temporale (PT), superior temporal parietal area (Stp), SMG, and cerebellum]. The results further show that activity in brain regions implicated with instantiating these internal models is correlated with better /r/ and /l/ identification performance for second-language speakers. Greater activity found for native-language speakers especially in the anterior STG/S for /r/ and /l/ perceptual identification is consistent with the hypothesis that native-language speakers use auditory phonetic representations more extensively than second-language speakers.

Adult↗

PubMed2004

Visual prosody and speech intelligibility: head movement improves auditory speech perception.

People naturally move their heads when they speak, and our study shows that this rhythmic head motion conveys linguistic information. Three-dimensional head and face motion and the acoustics of a talker producing Japanese sentences were recorded and analyzed. The head movement correlated strongly with the pitch (fundamental frequency) and amplitude of the talker's voice. In a perception study, Japanese subjects viewed realistic talking-head animations based on these movement recordings in a speech-in-noise task. The animations allowed the head motion to be manipulated without changing other characteristics of the visual or acoustic speech. Subjects correctly identified more syllables when natural head motion was present in the animation than when it was eliminated or distorted. These results suggest that nonverbal gestures such as head movements play a more direct role in the perception of speech than previously known.

Adult↗

PubMed2004

Multisensory integration sites identified by perception of spatial wavelet filtered visual speech gesture information.

Perception of speech is improved when presentation of the audio signal is accompanied by concordant visual speech gesture information. This enhancement is most prevalent when the audio signal is degraded. One potential means by which the brain affords perceptual enhancement is thought to be through the integration of concordant information from multiple sensory channels in a common site of convergence, multisensory integration (MSI) sites. Some studies have identified potential sites in the superior temporal gyrus/sulcus (STG/S) that are responsive to multisensory information from the auditory speech signal and visual speech movement. One limitation of these studies is that they do not control for activity resulting from attentional modulation cued by such things as visual information signaling the onsets and offsets of the acoustic speech signal, as well as activity resulting from MSI of properties of the auditory speech signal with aspects of gross visual motion that are not specific to place of articulation information. This fMRI experiment uses spatial wavelet bandpass filtered Japanese sentences presented with background multispeaker audio noise to discern brain activity reflecting MSI induced by auditory and visual correspondence of place of articulation information that controls for activity resulting from the above-mentioned factors. The experiment consists of a low-frequency (LF) filtered condition containing gross visual motion of the lips, jaw, and head without specific place of articulation information, a midfrequency (MF) filtered condition containing place of articulation information, and an unfiltered (UF) condition. Sites of MSI selectively induced by auditory and visual correspondence of place of articulation information were determined by the presence of activity for both the MF and UF conditions relative to the LF condition. Based on these criteria, sites of MSI were found predominantly in the left middle temporal gyrus (MTG), and the left STG/S (including the auditory cortex). By controlling for additional factors that could also induce greater activity resulting from visual motion information, this study identifies potential MSI sites that we believe are involved with improved speech perception intelligibility.

Adult↗

PubMed2003

Neural processes underlying perceptual enhancement by visual speech gestures.

This fMRI study explores brain regions involved with perceptual enhancement afforded by observation of visual speech gesture information. Subjects passively identified words presented in the following conditions: audio-only, audiovisual, audio-only with noise, audiovisual with noise, and visual only. The brain may use concordant audio and visual information to enhance perception by integrating the information in a converging multisensory site. Consistent with response properties of multisensory integration sites, enhanced activity in middle and superior temporal gyrus/sulcus was greatest when concordant audiovisual stimuli were presented with acoustic noise. Activity found in brain regions involved with planning and execution of speech production in response to visual speech presented with degraded or absent auditory stimulation, is consistent with the use of an additional pathway through which speech perception is facilitated by a process of internally simulating the intended speech act of the observed speaker.

Acoustic Stimulation↗

PubMed2003

Brain activity during audiovisual speech perception: an fMRI study of the McGurk effect.

fMRI was used to assess the relationship between brain activation and the degree of audiovisual integration of speech information during a phoneme categorization task. Twelve subjects heard a speaker say the syllable /aba/ paired either with video of the speaker saying the same consonant or a different one (/ava/). In order to manipulate the degree of audiovisual integration, the audio was either synchronous or +/- 400 ms out of phase with the visual stimulus. Subjects reported whether they heard the consonant /b/ or another consonant; fewer /b/ responses when the audio and visual stimuli were mismatched indicated higher levels of visual influence on speech perception (McGurk effect). Active brain regions during presentation of the incongruent stimuli included the superior temporal and inferior frontal gyrus, as well as extrastriate, premotor and posterior parietal cortex. A regression analysis related the strength of the McGurk effect to levels of brain activation. Paradoxically, higher numbers of /b/ responses were positively correlated with activation in the left occipito-temporal junction, an area often associated with processing visual motion. This activation suggests that auditory information modulates visual processing to affect perception.

Acoustic Stimulation↗

PubMed2003

Learning to produce speech with an altered vocal tract: the role of auditory feedback.

Modifying the vocal tract alters a speaker's previously learned acoustic-articulatory relationship. This study investigated the contribution of auditory feedback to the process of adapting to vocal-tract modifications. Subjects said the word /tas/ while wearing a dental prosthesis that extended the length of their maxillary incisor teeth. The prosthesis affected /s/ productions and the subjects were asked to learn to produce "normal" /s/'s. They alternately received normal auditory feedback and noise that masked their natural feedback during productions. Acoustic analysis of the speakers' /s/ productions showed that the distribution of energy across the spectra moved toward that of normal, unperturbed production with increased experience with the prosthesis. However, the acoustic analysis did not show any significant differences in learning dependent on auditory feedback. By contrast, when naive listeners were asked to rate the quality of the speakers' utterances, productions made when auditory feedback was available were evaluated to be closer to the subjects' normal productions than when feedback was masked. The perceptual analysis showed that speakers were able to use auditory information to partially compensate for the vocal-tract modification. Furthermore, utterances produced during the masked conditions also improved over a session, demonstrating that the compensatory articulations were learned and available after auditory feedback was removed.

Adult↗