Biology subjects

Hamilton, L. S.

Publications and source records attributed to Hamilton, L. S..

8 recordsLinked to original sources

bioRxiv2026

Perspectives in conducting task-based research in pediatric surgical epilepsy patients

ObjectivePediatric epilepsy patients undergoing stereo-electroencephalography (sEEG) for ictal onset evaluation provide a rare window to study the developing brain. While methodological frameworks for task-based sEEG research are well-established in adults, pediatric-specific guidance remains underdeveloped. Furthermore, many pediatric epilepsy patients have comorbidities that might typically exclude them from participating in research. We examine factors that influence research participation and discuss considerations for conducting sEEG research in children. MethodsHere, we present a retrospective analysis of task-based research participation patterns from an NIH-funded study of speech and language representations (1R01DC018579) in 66 patients (ages 4-24) undergoing sEEG monitoring at Texas Childrens Hospital to determine whether specific comorbidities influenced research participation. ResultsEighty-nine percent (n=66) of patients approached for consent agreed to participate in the study. Despite high rates of comorbidities including neurocognitive disorder (66.67%), language delay (31.75%), global developmental delay (23.81%), mood disorders (33.33%), ADHD (46.03%), autism spectrum disorder (14.29%) or other cognitive/intellectual disabilities (36.51%), all participants engaged in at least one task. While the majority of these diagnoses did not appear to influence subject participation, global developmental delay was associated with a significant reduction in time spent on active tasks. DiscussionDespite high prevalence of neuropsychological comorbidities among participants, our evidence suggests that these participants contribute meaningfully to studies investigating important developmental questions. We suggest strategies for tailoring task-based research to accommodate the unique needs of individuals in this population. Such practices are important for ensuring that research studies reflect the true diversity of the population.

neuroscience↗

bioRxiv2026

Human auditory cortex preferentially tracks speech over music without explicit attention

Our brains constantly filter incoming sounds to understand our environment. While extensively studied in adults, how this ability develops across childhood remains unclear. We recorded intracranial brain activity from 54 participants aged 4-21 while they watched movie clips containing simultaneous speech and music. We used deep neural networks to separate the mixed audio into isolated speech and music streams, then built encoding models to determine which stream best predicted neural responses in the auditory cortex. Although participants heard only the original mixture with no instruction to attend to either stream, higher-order auditory regions including the superior temporal gyrus (STG), superior temporal sulcus (STS) and middle temporal gyrus (MTG), responded preferentially to speech. This speech-bias strengthened with age in STG, suggesting that this region progressively sharpens its representation of socially relevant sound across development. These findings indicate that speech prioritization in the developing brain emerges automatically, without directed attention.

neuroscience↗

bioRxiv2024

Processing of auditory feedback in perisylvian and insular cortex

When we speak, we not only make movements with our mouth, lips, and tongue, but we also hear the sound of our own voice. Thus, speech production in the brain involves not only controlling the movements we make, but also auditory and sensory feedback. Auditory responses are typically suppressed during speech production compared to perception, but how this manifests across space and time is unclear. Here we recorded intracranial EEG in seventeen pediatric, adolescent, and adult patients with medication-resistant epilepsy who performed a reading/listening task to investigate how other auditory responses are modulated during speech production. We identified onset and sustained responses to speech in bilateral auditory cortex, with a selective suppression of onset responses during speech production. Onset responses provide a temporal landmark during speech perception that is redundant with forward prediction during speech production. Phonological feature tuning in these "onset suppression" electrodes remained stable between perception and production. Notably, the posterior insula responded at sentence onset for both perception and production, suggesting a role in multisensory integration during feedback control.

neuroscience↗

bioRxiv2023

A comparison of EEG encoding models using audiovisual stimuli and their unimodal counterparts

Communication in the real world is inherently multimodal. When having a conversation, typically sighted and hearing people use both auditory and visual cues to understand one another. For example, objects may make sounds as they move in space, or we may use the movement of a persons mouth to better understand what they are saying in a noisy environment. Still, many neuroscience experiments rely on unimodal stimuli (visual only or auditory only) to understand encoding of sensory features in the brain. The extent to which visual information may influence encoding of auditory information and vice versa in natural environments is thus unclear. Here, we addressed this question by recording scalp electroencephalography (EEG) in 11 subjects as they listened to and watched movie trailers in audiovisual (AV), visual (V) only, and audio (A) only conditions. We then fit linear encoding models that described the relationship between the brain responses and the acoustic, phonetic, and visual information in the stimuli. We also compared whether auditory and visual feature tuning was the same when stimuli were presented in the original AV format versus when visual or auditory information was removed. We found that auditory feature tuning was similar in the AV and A-only conditions, and similarly, tuning for visual information was similar when stimuli were presented with the audio present (AV) and when the audio was removed (V only). In a cross prediction analysis, we investigated whether models trained on AV data predicted responses to A or V only test data as well as using the unimodal conditions for training. Overall, prediction performance using AV training and V test sets was similar to using V training and V test sets, suggesting that the auditory information has a relatively smaller effect on EEG. In contrast, prediction performance using AV training and A only test set was slightly worse than using matching A only training and test sets. This suggests the visual information has a stronger influence on EEG, though this makes no qualitative difference in the derived feature tuning. In effect, our results show that researchers may benefit from the richness of multimodal datasets, which can then be used to answer more than one research question.

neuroscience↗

bioRxiv2022

Speaker-induced suppression in EEG during a naturalistic reading and listening task

Speaking elicits a suppressed neural response when compared to listening to others speech, a phenomenon known as speaker-induced suppression (SIS). Previous research has focused on investigating SIS at constrained levels of linguistic representation, such as the individual phoneme and word level. Here we present scalp EEG data from a dual speech perception and production task where participants read sentences aloud then listened to playback of themselves reading those sentences. Playback was separated into predictable repetition of the previous trial and unpredictable, randomized repetition of a former trial to investigate the role predictive processing plays in SIS. Concurrent EMG was recorded to control for movement artifact during speech production. In line with previous research, event-related potential analyses at the sentence level demonstrated suppression of early auditory components of the EEG for production compared to perception. To evaluate whether specific neural representations contribute to SIS (in contrast with a global gain change), we fit linear encoding models that predicted scalp EEG based on phonological features, EMG activity, and task condition. We found that phonological features were encoded similarly between production and perception. However, this similarity was only observed when controlling for movement by using the EMG response as an additional regressor. Our results suggest SIS is at the representational level a global gain change between perception and production, not the suppression of specific characteristics of the neural response. We also detail some important considerations when analyzing EEG during continuous speech production.

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bioRxiv2021

Generalizable EEG encoding models with naturalistic audiovisual stimuli

In natural conversations, listeners must attend to what others are saying while ignoring extraneous background sounds. Recent studies have used encoding models to predict electroencephalography (EEG) responses to speech in noise-free listening situations, sometimes referred to as "speech tracking" in EEG. Researchers have analyzed how speech tracking changes with different types of background noise. It is unclear, however, whether neural responses from noisy and naturalistic environments can be generalized to more controlled stimuli. If encoding models for noisy, naturalistic stimuli are generalizable to other tasks, this could aid in data collection from populations who may not tolerate listening to more controlled, less-engaging stimuli for long periods of time. We recorded non-invasive scalp EEG while participants listened to speech without noise and audiovisual speech stimuli containing overlapping speakers and background sounds. We fit multivariate temporal receptive field (mTRF) encoding models to predict EEG responses to pitch, the acoustic envelope, phonological features, and visual cues in both noise-free and noisy stimulus conditions. Our results suggested that neural responses to naturalistic stimuli were generalizable to more controlled data sets. EEG responses to speech in isolation were predicted accurately using phonological features alone, while responses to noisy speech were more accurate when including both phonological and acoustic features. These findings may inform basic science research on speech-in-noise processing. Ultimately, they may also provide insight into auditory processing in people who are hard of hearing, who use a combination of audio and visual cues to understand speech in the presence of noise. Significance StatementUnderstanding spoken language in natural environments requires listeners to parse acoustic and linguistic information in the presence of other distracting stimuli. However, most studies of auditory processing rely on highly controlled stimuli with no background noise, or with background noise inserted at specific times. Here, we compare models where EEG data are predicted based on a combination of acoustic, phonetic, and visual features in highly disparate stimuli - sentences from a speech corpus, and speech embedded within movie trailers. We show that modeling neural responses to highly noisy, audiovisual movies can uncover tuning for acoustic and phonetic information that generalizes to simpler stimuli typically used in sensory neuroscience experiments.

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bioRxiv2020

Topography of speech-related acoustic and phonological feature encoding throughout the human core and parabelt auditory cortex

Speech perception involves the extraction of acoustic and phonological features from the speech signal. How those features map out across the human auditory cortex is unknown. Complementary to noninvasive imaging, the high spatial and temporal resolution of intracranial recordings has greatly contributed to recent advances in our understanding. However, these approaches are typically limited by piecemeal sampling of the expansive human temporal lobe auditory cortex. Here, we present a functional characterization of local cortical encoding throughout all major regions of the primary and non-primary human auditory cortex. We overcame previous limitations by using rare direct recordings from the surface of the temporal plane after surgical microdissection of the deep Sylvian fissure between the frontal and temporal lobes. We recorded neural responses using simultaneous high-density direct recordings over the left temporal plane and the lateral superior temporal gyrus, while participants listened to natural speech sentences and pure tone stimuli. We found an anatomical separation of simple spectral feature tuning, including tuning for pure tones and absolute pitch, on the superior surface of the temporal plane, and complex tuning for phonological features, relative pitch and speech amplitude modulations on lateral STG. Broadband onset responses are unique to posterior STG and not found elsewhere in auditory cortices. This onset region is functionally distinct from the rest of STG, with latencies similar to primary auditory areas. These findings reveal a new, detailed functional organization of response selectivity to acoustic and phonological features in speech throughout the human auditory cortex.

neuroscience↗

bioRxiv2016

Parallel streams define the temporal dynamics of speech processing across human auditory cortex

To derive meaning from speech, we must extract multiple dimensions of concurrent information from incoming speech signals, including phonetic and prosodic cues. Equally important is the detection of acoustic cues that give structure and context to the information we hear, such as sentence boundaries. How the brain organizes this information processing is unknown. Here, using data-driven computational methods on an extensive set of high-density intracranial recordings, we reveal a large-scale partitioning of the entire human speech cortex into two spatially distinct regions that detect important cues for parsing natural speech. These caudal (Zone 1) and rostral (Zone 2) regions work in parallel to detect onsets and prosodic information, respectively, within naturally spoken sentences. In contrast, local processing within each region supports phonetic feature encoding. These findings demonstrate a fundamental organizational property of the human auditory cortex that has been previously unrecognized.

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