Browsing by Author "Simon, Jonathan Z."
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Item Data from: Rapid Transformation from Auditory to Linguistic Representations of Continuous Speech(2018) Brodbeck, Christian; Hong, L. Elliot; Simon, Jonathan Z.; Hong, L. Elliot; Simon, Jonathan Z.Magnetoencephalography (MEG) data and predictor variables from the article titled: Transformation from auditory to linguistic representations across auditory cortex is rapid and attention dependent for continuous speechItem Functional significance of spectrotemporal response functions obtained using magnetoencephalography(2017) Cervantes Constantino, Francisco; Villafañe-Delgado, Marisel; Camenga, Elizabeth; Dombrowski, Katya; Walsh, Benjamin; Simon, Jonathan Z.The spectrotemporal response function (STRF) model of neural encoding quantitatively associates dynamic auditory neural (output) responses to a spectrogram-like representation of a dynamic (input) stimulus. STRFs were experimentally obtained via whole-head human cortical responses to dynamic auditory stimuli using magnetoencephalography (MEG). The stimuli employed consisted of unpredictable pure tones presented at a range of rates. The predictive power of the estimated STRFs was found to be comparable to those obtained from the cortical single and multiunit activity literature. The STRFs were also qualitatively consistent with those obtained from electrophysiological studies in animal models; in particular their local-field-potential-generated spectral distributions and multiunit-activity-generated temporal distributions. Comparison of these MEG STRFs with others obtained using natural speech and music stimuli reveal a general structure consistent with common baseline auditory processing, including evidence for a transition in low-level neural representations of natural speech by 100 ms, when an appropriately chosen stimulus representation was used. It is also demonstrated that MEG-based STRFs contain information similar to that obtained using classic auditory evoked potential based approaches, but with extended applications to long-duration, non-repeated stimuliItem High Frequency Cortical Processing of Continuous Speech in Younger and Older Listeners - Dataset(2019) Kulasingham, Joshua; Brodbeck, Christian; Presacco, Alessandro; Kuchinsky, Stefanie E.; Anderson, Samira; Simon, Jonathan Z.Neural processing along the ascending auditory pathway is often associated with a progressive reduction in characteristic processing rates. For instance, the well-known frequency-following response (FFR) of the auditory midbrain, as measured with electroencephalography (EEG), is dominated by frequencies from ~100 Hz to several hundred Hz, phase-locking to the stimulus waveform at those frequencies. In contrast, cortical responses, whether measured by EEG or magnetoencephalography (MEG), are typically characterized by frequencies of a few Hz to a few tens of Hz, time-locking to acoustic envelope features. In this study we investigated a crossover, cortically generated responses time-locked to continuous speech features at FFR-like rates. Using MEG, we analyzed high-frequency responses (70-300 Hz) to continuous speech using neural source-localized reverse correlation and its corresponding temporal response functions (TRFs). Continuous speech stimuli were presented to 40 subjects (17 younger, 23 older adults) with clinically normal hearing and their MEG responses were analyzed in the 70-300 Hz band. Consistent with the insensitivity of MEG to many subcortical structures, the spatiotemporal profile of these response components indicated a purely cortical origin with ~40 ms peak latency and a right hemisphere bias. TRF analysis was performed using two separate aspects of the speech stimuli: a) the 70-300 Hz band of the speech waveform itself, and b) the 70-300 Hz temporal modulations in the high frequency envelope (300-4000 Hz) of the speech stimulus. The response was dominantly driven by the high frequency envelope, with a much weaker contribution from the waveform (carrier) itself. Age-related differences were also analyzed to investigate a reversal previously seen along the ascending auditory pathway, whereby older listeners show weaker midbrain FFR responses than younger listeners, but, paradoxically, have stronger cortical low frequency responses. In contrast to both these earlier results, this study does not find clear age-related differences in high frequency cortical responses. Finally, these results suggest that EEG high (FFR-like) frequency responses have distinct and separable contributions from both subcortical and cortical sources. Cortical responses at FFR-like frequencies share some properties with midbrain responses at the same frequencies and with cortical responses at much lower frequencies.Item Improving Auditory CAPTCHA Security(2008-11-05) Bohr, Sonja; Shome, Andrea; Simon, Jonathan Z.; Simon, Jonathan Z.CAPTCHAs are tests used by resource-rich websites to ensure that humans, but not malicious automated programs, have access to their resources. Most CAPTCHAs are visual tests (e.g. identifying distorted text), but auditory versions are necessary to provide access to the visually impaired, and are currently deployed at commonly used websites such as Google and Facebook. To be effective at deterring automated programs, they must be at least as secure as their visual counterparts. Assuming that the attacks against auditory CAPTCHAs will depend on automatic speech recognition systems (ASRs), we undertook the project of designing auditory CAPTCHAs that would take advantage of the weaknesses in ASRs as compared to the human auditory system. Examples of such weaknesses of ASRs, relative to humans, include impeded recognition in the presence of broadband and time-varying noise such as multiple simultaneous speakers. Results show that a combination of such disruptive noise types can outperform currently employed techniques while still maintaining human intelligibility.Item Linear stimulus-invariant processing and spectrotemporal reverse correlation in primary auditory cortex(2003) Klein, David J.; Simon, Jonathan Z.; Depireux, Didier A.; Shamma, Shihab A.; Shamma, Shihab A.; ISR; CAARThe spectrotemporal receptive field (STRF) provides a versatile and integrated (spectral and temporal) functional characterization of single cells in primary auditory cortex (AI). We explore in this paper the origin and relationship between several different ways of measuring and analyzing the STRF. Specifically, we demonstrate that STRFs measured using a spectrotemporally diverse array of broadband stimuli --- such as dynamic ripples, spectrotemporally white noise (STWN), and temporally orthogonal ripple combinations (TORCs) --- are very similar, confirming earlier findings that the STRF is a robust linear descriptor of the cell. We also present a new deterministic analysis framework that employs the Fourier series to describe the spectrotemporal modulation frequency content of the stimuli and responses. Additional insights into the STRF measurements, including the nature and interpretation of measurement errors, is presented using the Fourier transform, coupled to singular-value decomposition (SVD), and variability analyses including bootstrap. The results promote the utility of the STRF as a core functional descriptor of neurons in AI.Item The neural representation of missing speech and the influence of prior knowledge on cortical fidelity and latency(2018) Cervantes Constantino, Francisco; Simon, Jonathan Z.In naturally noisy listening conditions, for example at a cocktail party, noise disruptions may completely mask significant parts of a sentence, and yet listeners may still perceive the missing speech as being present. Here we demonstrate that dynamic speech-related auditory cortical activity, as measured by magnetoencephalography (MEG), which can ordinarily be used to directly reconstruct to the physical speech stimulus, can also be used to “reconstruct” acoustically missing speech. The extent to which this occurs depends on the extent that listeners are familiar with the missing speech, which is consistent with this neural activity being a dynamic representation of perceived speech even if acoustically absence. Our findings are two-fold: first, we find that when the speech is entirely acoustically absent, the acoustically absent speech can still be reconstructed with performance up to 25% of that of acoustically present speech without noise; and second, that this same expertise facilitates faster processing of natural speech by approximately 5 ms. Both effects disappear when listeners have no or very little prior experience with a given sentence. Our results suggest adaptive mechanisms of consolidation of detailed representations about speech, and the enabling of strong expectations this entails, as identifiable factors assisting automatic speech restoration over ecologically relevant timescales.