Biology subjects

Kovach, C. K.

Publications and source records attributed to Kovach, C. K..

18 recordsLinked to original sources

bioRxiv2026

Genuinely Blind Identification of Sleep Spindles through Trispectral Modulation Analysis

Sleep spindles, transient 11-16 Hz oscillatory bursts, are a defining electrographic feature of non-rem (NREM) sleep and a key biomarker of sleep physiology. A need for efficient and reliable identification of spindles motivates a large literature on automated detection algorithms. In this literature, annotation by trained sleep specialists remains the gold standard against which automated methods are trained, tuned and evaluated. However, inter-scorer agreement among experts is modest, which leaves a significant role for subjective judgment in the definition of a spindle. Finding objective, scorer-independent, criteria for identifying spindles remains an unresolved challenge. We report here a robust, highly specific, and previously unrecognized signature of spindle activity in the fourth-order spectrum (trispectrum), from which we identify the presence of spindles, characterize their waveforms, and obtain an optimal detection filter through a decomposition of the trispectrum (HOSD). Although it is a strictly blind, data-driven method, HOSD-based spindle identification and detection agrees well with expert annotation (median AUROC ~0.9), yet identifies many more events at the native threshold than both human scorers and comparison detectors. Many of these additional detections are confirmed as meeting AASM spindle criteria by four blinded specialists, demonstrating that spindle-like oscillatory bursting is prevalent below conventional human and automated detection thresholds. We observe that N2 sleep is distinguished principally by high-amplitude bursts, while low-amplitude bursting persists throughout NREM sleep, being globally suppressed only in REM sleep. We also describe robust identification of recording-specific spindle waveform properties such as frequency deceleration.

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bioRxiv2025

Distinct Temporal Patterns of Human Neural Firing in the Subthalamic Nucleus During Speech and Orofacial Movement

Clinical studies, along with electrophysiological findings, provide evidence that the subthalamic nucleus (STN) contributes to speech production. These studies have reported that the STN encodes diverse aspects of speech, comprising speech motor planning and execution, timing, and linguistic features such as phonetic content. However, none of these studies have included an orofacial non-speech motor task to evaluate speech-specificity of STN activity. Here, we examined the modulation of STN neurons while participants engaged in two speech tasks (sentence repetition and syllable repetition) as well as two non-speech orofacial movement tasks (jaw movement and tongue protrusion) in awake patients with Parkinsons disease undergoing deep brain stimulation implantation surgery. A total of 51 single- and multi-unit neural clusters were captured. A Poisson generalized linear model (GLM) was implemented to understand the temporal dynamics of STN activity. A larger proportion of clusters was modulated during speech (22%) than during orofacial movement (12%) and a substantial subset of STN neural clusters responded to overlapping speech and orofacial tasks (27%). The findings suggest that STN can encode both motor and linguistic aspects of speech production. Graphical abstractThe subthalamic nucleus (STN) shows neural modulation during speech production, a process which requires motor planning, execution, and phonological functions. By comparing STN spiking activity during speech tasks (sentence and syllable repetition) and non-speech orofacial tasks (jaw movement and tongue protrusion), we identified task-specific modulation patterns in STN neurons. The STN contains distinct neural populations engaged during speech and orofacial movements. Among all recorded clusters, 22% responded exclusively to speech, 12% exclusively to orofacial movements, 27% to both, and 39% were non-responsive. We demonstrated that STN activity at single- and multi-unit levels is specific to speech production and is influenced by task-specific motor and linguistic demands, highlighting a role for STN in integrating motor control and speech production. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=108 SRC="FIGDIR/small/693637v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@1ec3c60org.highwire.dtl.DTLVardef@6fe46forg.highwire.dtl.DTLVardef@1fe733corg.highwire.dtl.DTLVardef@3f736b_HPS_FORMAT_FIGEXP M_FIG C_FIG

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bioRxiv2025

Brain-wide single-neuron bases of working memory for sounds in humans

In order to understand the constantly changing acoustic world our brains must maintain elements of auditory scenes in memory. The neural mechanisms for this fundamental process remain unclear. Here, we report human intracranial recordings of 1269 single neurons while participants performed a non-verbal auditory working memory task that required adjustment of a tone frequency to match a target. We found neurons within hippocampus, insula and cingulate cortex, for which firing rates were modulated at different phases of the task, particularly during maintenance and adjustment. For the majority of the neurons modulated during maintenance there was a striking suppression of activity rather than increased activity. Across the entire neuronal population, state-space analysis demonstrated attractor-like states corresponding to different task phases. Behaviorally, more neurons were modulated at the beginning of the maintenance phase in trials when participants performed better. State-space analysis was consistent with greater attractor-like activity during the adjustment phase supporting better performance. These data support the existence of a widely distributed neural code for auditory working memory that determines related behavior based on attractor-like states.

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bioRxiv2025

Neural activity flows through cortical subnetworks during speech production

Speech production entails several processing steps that encode linguistic and articulatory structure, but whether these computations correspond to spatiotemporally discrete patterns of neural activity is unclear. To address this issue, we used electrocorticography to directly measure the brains of neurosurgical participants performing an interactive speech paradigm. We observed a broad range of cortical modulation profiles, and subsequent clustering analyses established that responses comprised distinct classes associated with sensory perception, planning, motor execution, and task-related suppression. These activity classes were also localized to separate neural substrates, indicating their status as specialized networks. We then parsed dynamics in the planning and motor networks using unsupervised dimensionality reduction, which revealed subnetworks that were sequentially active throughout preparation and articulation. These results therefore support and extend a localizationist model of speech production where cortical activity flows within and across discrete pathways during language use.

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bioRxiv2023

Sensing, Feeling, and Regulating: Investigating the Association of Focal Brain Damage with Voluntary Respiratory and Motor Control

Breathing is a complex, vital function that can be modulated to influence physical and mental well-being. However, the role of cortical and subcortical brain regions in voluntary control of human respiration is underexplored. Here we investigated the influence of damage to human frontal, temporal, or limbic regions on the sensation and regulation of breathing patterns. Participants performed a respiratory regulation task across regular and irregular frequencies ranging from 6 to 60 breaths per minute (bpm), with a counterbalanced hand motor control task. Interoceptive and affective states induced by each condition were assessed via questionnaire and autonomic signals were indexed via skin conductance. Participants with focal lesions to the bilateral frontal lobe, right insula/basal ganglia, and left medial temporal lobe showed reduced performance than individually matched healthy comparisons during the breathing and motor tasks. They also reported significantly higher anxiety during the 60-bpm regular and irregular breathing trials, with anxiety correlating with difficulty in rapid breathing specifically within this group. This study demonstrates that damage to frontal, temporal, or limbic regions is associated with abnormal voluntary respiratory and motor regulation and tachypnea-related anxiety, highlighting the role of the forebrain in affective and motor responses during breathing. HighlightsO_LIImpaired human respiratory regulation is associated with cortical/subcortical brain lesions C_LIO_LIFrontolimbic/temporal regions contribute to rhythmic breathing and hand motor control C_LIO_LIFrontolimbic/temporal damage is associated with anxiety during tachypnea/irregular breathing C_LIO_LIThe human forebrain is vital for affective and interoceptive experiences during breathing C_LI

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bioRxiv2023

Activity-induced gene expression in the human brain

Direct electrical stimulation (eSTIM) is widely used clinically, from neurosurgical mapping to therapeutic interventions for neurological and neuropsychiatric disorders1-10. Despite over a century of application, its molecular and cellular underpinnings remain unknown. Here, using state-of-the-art single-nuclei multiomic profiling, we map changes in cell-type-specific gene expression and chromatin accessibility in vivo in the human cortex following eSTIM of neurosurgery patients. eSTIM impacts a network of cells that extends beyond excitatory neurons to include inhibitory neurons, astrocytes, oligodendrocytes and microglia. We observed an upregulation of canonical immediate-early genes (IEGs: FOS, NPAS4, EGR4) in excitatory and inhibitory neurons and induction of cytokine-related genes CCL3 and CCL4 in microglia. The cross-species conservation of this gene signature, together with our examination of a cohort of both epilepsy and cancer patients, underscores the fundamental role of these changes in stimulation-driven plasticity while controlling for disease and environmental confounds. Our study of changes in chromatin accessibility reveals a common code that involves a cell-type specific signature of transcription factor binding motifs for members of the EGR family. By addressing these previously unexplored questions about activity-induced gene expression in vivo in the human brain, our findings challenge the long-standing neuron-centric view of eSTIM, highlighting the broader role of non-neuronal cells, including microglia, in mediating the impact of brain stimulation.

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bioRxiv2023

Identifying critical language planning regions with direct electrical brain stimulation

Many brain areas exhibit activity correlated with language planning1-9, but the impact of these dynamics on spoken interaction remains unclear. Here we use direct electrical stimulation to transiently perturb cortical function in neurosurgical patient-volunteers performing a question-answer task10. Stimulating structures involved in speech motor function evoked diverse articulatory deficits, while perturbations of caudal inferior and middle frontal gyri - which exhibit preparatory activity during conversational turn-taking - led to response errors. Perturbation of the same planning-related frontal regions slowed inter-speaker timing, while faster responses could result from stimulation of sites located in other areas. Taken together, these findings further indicate that caudal inferior and middle frontal gyri constitute a critical planning network essential for interactive language use1.

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bioRxiv2023

Exercise modulates human hippocampal-cortical ripple dynamics

Physical exercise acutely improves hippocampus-dependent memory. Whereas animal studies have offered cellular- and synaptic-level accounts of these effects, human neuroimaging studies show that exercise improves hippocampal-cortical connectivity at the macroscale level. However, the neurophysiological basis of exercise-induced effects on hippocampal-cortical circuits remains unknown. Experimental evidence supports that hippocampal sharp wave-ripples (SWR) play a critical role in learning and memory. Coupling between SWRs in the hippocampus and neocortex may reflect modulations in inter-regional connectivity required by mnemonic processes. Here, we examine the hypothesis that exercise modulates hippocampal-cortical ripple dynamics in the human brain. We performed intracranial recordings in epilepsy patients undergoing pre-surgical evaluation, during awake resting state, before and after an exercise session. Exercise increased ripple rate in the hippocampus. Exercise also enhanced the coupling and phase-synchrony between cortical ripples in the limbic and the default mode (DM) cortical networks and hippocampal SWRs. Further, higher heart rate during exercise, reflecting exercise intensity, was related to a subsequent increase in resting state ripples across specific cortical networks including the DMN. These results offer the first direct evidence that a single exercise session elicits changes in ripple events, a well-established neurophysiological marker of mnemonic processing. The characterization and anatomical distribution of the described modulation points to hippocampal ripples as a potential mechanism by which exercise elicits its reported short-term effects in cognition.

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bioRxiv2023

Temporally organized representations of reward and risk in the human brain

AO_SCPLOWBSTRACTC_SCPLOWThe value and uncertainty associated with choice alternatives constitute critical features along which decisions are made. While the neural substrates supporting reward and risk processing have been investigated, the temporal organization by which these computations are encoded remains elusive. Here we leverage the high spatiotemporal precision of intracranial electroencephalography (iEEG) to uncover how representations of decision-related computations unfold in time. We present evidence of locally distributed representations of reward and risk variables that are temporally organized across multiple regions of interest. Reward outcome representations across wide-spread regions follow a temporally cascading order along the anteroposterior axis of the brain. In contrast, expected value can be decoded from multiple regions at the same time, and error signals in both reward and risk domains reflect a mixture of sequential and parallel encoding. We highlight the role of the anterior insula in generalizing between reward prediction error (RePE) and risk prediction error (RiPE), within which the encoding of RePE in the distributed iEEG signal predicts RiPE. Together our results emphasize the utility of uncovering temporal dynamics in the human brain for understanding how computational processes critical for value-based decisions under uncertainty unfold.

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bioRxiv2022

Consciousness is indexed by analogous cortical reorganization during sleep and anesthesia

Although sleep and anesthesia are predicted to share common neural signatures of transitions into and out of unconsciousness, supportive evidence has been elusive. We identified these signatures using intracranial electroencephalography in neurosurgical patients. We applied diffusion map embedding to map cortical location into a space where proximity indicates functional similarity using a normalized connectivity ( diffusion) matrix, itself a rich source of information about network properties. During reduced consciousness, diffusion matrices exhibited decreased effective dimensionality, reflecting reduced network entropy. Furthermore, functional brain regions exhibited tighter clustering in embedding space with greater distances between regions, corresponding to decreased differentiation and functional integration. These changes were not region-specific, suggesting global network reorganization. These results strongly suggest common neural substrates for loss and recovery of consciousness during anesthesia and sleep, providing a systems-level mechanistic understanding within an intuitive geometric context and laying the foundation for evaluation of cortical state transitions in clinical settings.

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bioRxiv2022

Immediate neural network impact after the loss of a semantic hub

The human brain extracts meaning from the world using an extensive neural system for semantic knowledge. Whether such broadly distributed systems1-3 crucially depend on or can compensate for the loss of one of their highly interconnected hubs4-6 is controversial4. The strongest level of causal evidence for the role of a brain hub is to evaluate its acute network-level impact following disconnection and any rapid functional compensation that ensues. We report rare neurophysiological data from two patients who underwent awake intracranial recordings during a speech prediction task immediately before and after neurosurgical treatment that required disconnection of the left anterior temporal lobe (ATL), a crucial hub for semantic knowledge4-6. Informed by a predictive coding framework, we tested three sets of hypotheses including diaschisis causing disruption in interconnected sites7 and incomplete or complete compensation by other language-critical and speech processing sites8-10. Immediately after ATL disconnection, we observed highly specific neurophysiological alterations in the recorded fronto-temporal network, including abnormally magnified high gamma responses to the speech sounds in auditory cortex. We also observed evidence for rapid compensation, seen as focal increases in effective connectivity involving language-critical sites in the inferior frontal gyrus and speech processing sites in auditory cortex. However, compensation was incomplete, in part because after ATL disconnection speech prediction signals were depleted in auditory cortex. This study provides direct causal evidence for a semantic hub in the human brain and shows striking neural impact and a rapid attempt at compensation in a neural network after the loss of one of its hubs.

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bioRxiv2022

Functional geometry of auditory cortical resting state networks derived from intracranial electrophysiology

Understanding central auditory processing critically depends on defining underlying auditory cortical networks and their relationship to the rest of the brain. We addressed these questions using resting state functional connectivity derived from human intracranial electroencephalography. Mapping recording sites into a low-dimensional space where proximity represents functional similarity revealed a hierarchical organization. At fine scale, a group of auditory cortical regions excluded several higher order auditory areas and segregated maximally from prefrontal cortex. On mesoscale, the proximity of limbic structures to auditory cortex suggested a limbic stream that parallels the classically described ventral and dorsal auditory processing streams. Identities of global hubs in anterior temporal and cingulate cortex depended on frequency band, consistent with diverse roles in semantic and cognitive processing. On a macro scale, observed hemispheric asymmetries were not specific for speech and language networks. This approach can be applied to multivariate brain data with respect to development, behavior, and disorders. BlurbWe describe the organization of human neocortex on multiple spatial scalesbased on resting state intracranial electrophysiology. We focus on cortical regions involved in auditory processing and examine inter-regional hierarchical relationships, network topology, and hemispheric lateralization. This work introduces a powerful analytical tool to examine mechanisms of altered arousal states, brain development, and neuropsychiatric disorders.

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bioRxiv2021

Distribution of multi-unit pitch responses recorded intracranially from human auditory cortex

The perception of pitch requires the abstraction of stimulus properties related to the spectrotemporal structure of sound. Previous studies utilizing both animal electrophysiology and human imaging have indicated the presence of a center for pitch representation in the auditory cortex. Recent data from our own group - examining local field potentials (LFPs) in humans - indicate more widely distributed pitch-associated responses within the auditory cortex (Gander et al., 2019). To probe this with greater spatial resolution, we examined multi-unit activity related to three different auditory stimuli, in seven epilepsy patients who were implanted with high-impedance electrodes in auditory cortex for the clinical purpose of localizing seizures. The stimuli were regular-interval noise (RIN) with a pitch strength that is related to the temporal regularity, and pitch value determined by repetition rate, and harmonic complexes with missing fundamentals. We demonstrated increases in spiking activity in 69 of 104 (66%) responsive multiunit activity in auditory cortex due to pitch-associated stimuli. Importantly, these responses were distributed across the entire extent of Heschls gyrus (HG), in both primary and non-primary areas, rather than isolated to a specific region, and this finding was evident regardless of the stimulus presented. These findings are the first multi-unit pitch responses recorded from humans, and align with a recent study in macaques (Kikuchi et al., 2019) demonstrating that both local field potential and unit responses to pitch-inducing stimuli are distributed throughout auditory cortex. Significance StatementThe perception of pitch is a fundamental acoustic attribute that is mediated by the auditory system. Despite its importance, there is still debate as to the precise areas responsible for its encoding, which may be due to differences in the recording measures and choices of stimuli used in previous studies. Here, we present the first study to measure multi-unit pitch responses in the auditory cortices of intracranially-implanted humans. Importantly, we demonstrate reliable responses to three different pitch-inducing paradigms that are distributed throughout Heschls gyrus, rather than being localized to a particular region. These data provide a bridge across animal and human studies, and aid in our understanding of the processing of a critical attribute of acoustic stimuli.

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bioRxiv2020

Differential causal involvement of human auditory and frontal cortices in vocal motor control

Speech motor control requires integration of sensory and motor information. Bidirectional communication between frontal and auditory cortices is crucial for speech production, self-monitoring and motor control. We used cortical direct electrical stimulation (DES) to functionally dissect audio-motor interactions underlying speech production and motor control. Eleven neurosurgical patients performed a visually cued vocal task in which a short auditory feedback perturbation was introduced during vocalization. We evaluated the effect of DES on vocal initiation, voice fundamental frequency (F0) and feedback-dependent motor control. DES of frontal sites modulated vocal onset latencies. Stimulation of different inferior frontal gyrus sites elicited either shortening or prolongation of vocal latencies. DES distinctly modulated voice F0 at different vocalization stages. Frontal and temporal areas played an important role in setting voice F0 in the first 250 ms of an utterance, while Heschls gyrus was involved later when auditory input is available for self-monitoring. Vocal responses to pitch-shifted auditory feedback were mostly reduced by DES of non-core auditory cortices. Overall, we demonstrate that vocal planning and initiation are driven by frontal cortices, while feedback-dependent control relies predominantly on non-core auditory cortices. Our findings represent direct evidence of the role played by different auditory and frontal regions in vocal motor control.

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bioRxiv2020

Focal cortical surface cooling is a novel and safe method for intraoperative functional brain mapping

ObjectiveElectrical cortical stimulation (ECS) has been the gold standard for intraoperative functional mapping in neurosurgery, yet it carries the risk of induced seizures. Here we assess the safety of focal cortical cooling (CC) as a potential alternative to ECS for functional brain mapping. MethodsWe retrospectively reviewed 40 consecutive subjects (n=13 tumor, 27 mesial temporal lobe epilepsy (MTLE) resection) who underwent intraoperative CC during craniotomy at the University of Iowa Hospital and Clinics from 2007 through 2019 (CC group). Thirty-eight of the 40 subjects had ECS performed along with CC during the same procedure. To assess the safety of CC, intra- and post-operative seizure incidence and post-operative neurological deficits were collected together with new post-operative radiographic findings not related to the surgical procedure itself (i.e. non-mapping portions). As a control cohort, we collected 55 consecutive subjects (n=21 MTLE, 34 tumor/vascular pathology) who underwent awake ECS mapping without CC between 2006 and 2019 (ECS-alone group). To evaluate potential long term effects of mapping techniques (CC and/or ECS), we separately collected another 25 consecutive subjects who underwent anterior temporal lobectomy(ATL) without CC nor ECS between 2007 and 2019 (No ECS/No CC-ATL group). ResultsA total of 79 brain sites were cooled in the 40 CC subjects, including inferior frontal gyrus (44%), precentral gyrus (39%), postcentral gyrus (6%), subcentral gyrus (4%) and superior temporal gyrus (6%). No intraoperative seizures were reported in the CC group, whereas 3.6% of ECS-alone group had intraoperative seizures. The incidence of seizure(s) within the first post-operative week did not significantly differ amongst CC (7.9%), ECS-alone (9.0%) and No ECS/No CC-ATL groups (12%). There was no significante difference in the incidence of postoperative radiographic change between CC (7.5%) and ECS-alone groups (5.5 %). The long term seizure outcome for MTLE subjects did not statistically differ regarding good outcomes (Engel I+II): CC group (80%), ECS-alone (83.3%) and No ECS/No CC-ATL group (83.3%). ConclusionsCortical cooling when used as an intraoperative mapping technique is safe, and may complement traditional electrical cortical stimulation.

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bioRxiv2020

Common Fronto-temporal Effective Connectivity in Humans and Monkeys

Cognitive pathways supporting human language and declarative memory are thought to have uniquely evolutionarily differentiated in our species. However, cross-species comparisons are missing on site-specific effective connectivity between regions important for cognition. We harnessed a new approach using functional imaging to visualize the impact of direct electrical brain stimulation in human neurosurgery patients. Applying the same approach with macaque monkeys, we found remarkably comparable patterns of effective connectivity between auditory cortex and ventro-lateral prefrontal cortex (vlPFC) and parahippocampal cortex in both species. Moreover, in humans electrical tractography revealed rapid evoked potentials in vlPFC from stimulating auditory cortex and speech sounds drove vlPFC, consistent with prior evidence in monkeys of direct projections from auditory cortex to vocalization responsive regions in vlPFC. The results identify a common effective connectivity signature that from auditory cortex is equally direct to vlPFC and indirect to the hippocampus (via parahippocampal cortex) in human and nonhuman primates. HighlightsO_LIPrivileged human auditory to inferior frontal connectivity, linked to monkeys C_LIO_LICommon auditory to parahippocampal effective connectivity in both species C_LIO_LIGreater lateralization in human effective connectivity, more symmetrical in monkeys C_LIO_LIHuman fronto-temporal network function rooted in evolutionarily conserved signature C_LI eTOC short summaryFunctional connectivity between regions crucial for language and declarative memory is thought to have substantially differentiated in humans. Using a new technique to similarly visualize directional effective connectivity in humans and monkeys, we found remarkably comparable connectivity patterns in both species between fronto-temporal regions crucial for cognition.

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bioRxiv2019

Cortical functional connectivity indexes arousal state during sleep and anesthesia

Disruption of cortical connectivity likely contributes to loss of consciousness (LOC) during both sleep and general anesthesia, but the degree of overlap in the underlying mechanisms is unclear. Both sleep and anesthesia comprise states of varying levels of arousal and consciousness, including states of largely maintained consciousness (sleep: N1, REM; anesthesia: sedated but responsive) as well as states of substantially reduced consciousness (sleep: N2/N3; anesthesia: unresponsive). Here, we tested the hypotheses that (1) cortical connectivity will reflect clear changes when transitioning into states of reduced consciousness, and (2) these changes are similar for arousal states of comparable levels of consciousness during sleep and anesthesia. Using intracranial recordings from five neurosurgical patients, we compared resting state cortical functional connectivity (as measured by weighted phase lag index) in the same subjects across arousal states during natural sleep [wake (WS), N1, N2, N3, REM] and propofol anesthesia [pre-drug wake (WA), sedated/responsive (S) and unresponsive (U)]. In wake states WS and WA, alpha-band connectivity within and between temporal, parietal and occipital regions was dominant. This pattern was largely unchanged in N1, REM and S. Transitions into states of reduced consciousness N2, N3 and U were characterized by dramatic and strikingly similar changes in connectivity, with dominant connections shifting to frontal cortex. We suggest that shifts from temporo-parieto-occipital to frontal cortical connectivity may reflect impaired sensory processing in states of reduced consciousness. The data indicate that functional connectivity can serve as a biomarker of arousal state and suggest common mechanisms of LOC in sleep and anesthesia.

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bioRxiv2019

A sound-sensitive source of alpha oscillations in human non-primary auditory cortex

The functional organization of human auditory cortex can be probed by characterizing responses to various classes of sound at different anatomical locations. Along with histological studies this approach has revealed a primary field in posteromedial Heschls gyrus (HG) with pronounced induced high-frequency (70-150 Hz) activity and short-latency responses that phase-lock to rapid transient sounds. Low-frequency neural oscillations are also relevant to stimulus processing and information flow, however their distribution within auditory cortex has not been established. Alpha activity (7-14 Hz) in particular has been associated with processes that may differentially engage earlier versus later levels of the cortical hierarchy, including functional inhibition and the communication of sensory predictions. These theories derive largely from the study of occipitoparietal sources readily detectable in scalp electroencephalography. To characterize the anatomical basis and functional significance of less accessible temporal-lobe alpha activity we analyzed responses to sentences in seven human adults (four female) with epilepsy who had been implanted with electrodes in superior temporal cortex. In contrast to primary cortex in posteromedial HG, a non-primary field in anterolateral HG was characterized by high spontaneous alpha activity that was strongly suppressed during auditory stimulation. Alpha-power suppression decreased with distance from anterolateral HG throughout superior temporal cortex, and was more pronounced for clear compared to degraded speech. This suppression could not be accounted for solely by a change in the slope of the power spectrum. The differential manifestation and stimulus-sensitivity of alpha oscillations across auditory fields should be accounted for in theories of their generation and function.\n\nSignificance StatementTo understand how auditory cortex is organized in support of perception, we recorded from patients implanted with electrodes for clinical reasons. This allowed measurement of activity in brain regions at different levels of sensory processing. Oscillations in the alpha range (7-14 Hz) have been associated with functions including sensory prediction and inhibition of regions handling irrelevant information, but their distribution within auditory cortex is not known. A key finding was that these oscillations dominated in one particular non-primary field, anterolateral Heschls gyrus, and were suppressed when subjects listened to sentences. These results build on our knowledge of the functional organization of auditory cortex and provide anatomical constraints on theories of the generation and function of alpha oscillations.

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