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1.
Elife ; 102021 10 08.
Artigo em Inglês | MEDLINE | ID: mdl-34622779

RESUMO

The brain has a remarkable capacity to acquire and store memories that can later be selectively recalled. These processes are supported by the hippocampus which is thought to index memory recall by reinstating information stored across distributed neocortical circuits. However, the mechanism that supports this interaction remains unclear. Here, in humans, we show that recall of a visual cue from a paired associate is accompanied by a transient increase in the ratio between glutamate and GABA in visual cortex. Moreover, these excitatory-inhibitory fluctuations are predicted by activity in the hippocampus. These data suggest the hippocampus gates memory recall by indexing information stored across neocortical circuits using a disinhibitory mechanism.


Assuntos
Hipocampo/fisiologia , Rememoração Mental , Neocórtex/fisiologia , Inibição Neural , Plasticidade Neuronal , Estimulação Acústica , Associação , Vias Auditivas/fisiologia , Percepção Auditiva , Mapeamento Encefálico , Sinais (Psicologia) , Feminino , Ácido Glutâmico/metabolismo , Hipocampo/diagnóstico por imagem , Hipocampo/metabolismo , Humanos , Imageamento por Ressonância Magnética , Espectroscopia de Ressonância Magnética , Masculino , Neocórtex/diagnóstico por imagem , Neocórtex/metabolismo , Estimulação Luminosa , Fatores de Tempo , Vias Visuais/fisiologia , Percepção Visual , Adulto Jovem , Ácido gama-Aminobutírico/metabolismo
2.
PLoS Comput Biol ; 17(8): e1009251, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34339409

RESUMO

In the auditory system, tonotopy is postulated to be the substrate for a place code, where sound frequency is encoded by the location of the neurons that fire during the stimulus. Though conceptually simple, the computations that allow for the representation of intensity and complex sounds are poorly understood. Here, a mathematical framework is developed in order to define clearly the conditions that support a place code. To accommodate both frequency and intensity information, the neural network is described as a space with elements that represent individual neurons and clusters of neurons. A mapping is then constructed from acoustic space to neural space so that frequency and intensity are encoded, respectively, by the location and size of the clusters. Algebraic operations -addition and multiplication- are derived to elucidate the rules for representing, assembling, and modulating multi-frequency sound in networks. The resulting outcomes of these operations are consistent with network simulations as well as with electrophysiological and psychophysical data. The analyses show how both frequency and intensity can be encoded with a purely place code, without the need for rate or temporal coding schemes. The algebraic operations are used to describe loudness summation and suggest a mechanism for the critical band. The mathematical approach complements experimental and computational approaches and provides a foundation for interpreting data and constructing models.


Assuntos
Córtex Auditivo/fisiologia , Percepção Auditiva/fisiologia , Modelos Neurológicos , Estimulação Acústica , Animais , Vias Auditivas/fisiologia , Biologia Computacional , Simulação por Computador , Potenciais Evocados Auditivos/fisiologia , Humanos , Percepção Sonora/fisiologia , Rede Nervosa/fisiologia , Redes Neurais de Computação , Percepção da Altura Sonora/fisiologia , Transmissão Sináptica/fisiologia
3.
Elife ; 102021 07 12.
Artigo em Inglês | MEDLINE | ID: mdl-34250904

RESUMO

Activity in each brain region is shaped by the convergence of ascending and descending axonal pathways, and the balance and characteristics of these determine the neural output. The medial olivocochlear (MOC) efferent system is part of a reflex arc that critically controls auditory sensitivity. Multiple central pathways contact MOC neurons, raising the question of how a reflex arc could be engaged by diverse inputs. We examined functional properties of synapses onto brainstem MOC neurons from ascending (ventral cochlear nucleus, VCN) and descending (inferior colliculus, IC) sources in mice using an optogenetic approach. We found that these pathways exhibited opposing forms of short-term plasticity, with the VCN input showing depression and the IC input showing marked facilitation. By using a conductance-clamp approach, we found that combinations of facilitating and depressing inputs enabled firing of MOC neurons over a surprisingly wide dynamic range, suggesting an essential role for descending signaling to a brainstem nucleus.


Assuntos
Cóclea/fisiologia , Núcleo Coclear/fisiologia , Plasticidade Neuronal/fisiologia , Neurônios Eferentes/fisiologia , Estimulação Acústica/métodos , Animais , Vias Auditivas/fisiologia , Axônios/fisiologia , Tronco Encefálico/fisiologia , Nervo Coclear/fisiologia , Colículos Inferiores/fisiologia , Camundongos , Núcleo Olivar/fisiologia , Optogenética/métodos , Sinapses/fisiologia
4.
PLoS Comput Biol ; 17(7): e1009130, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-34242210

RESUMO

Sound localization relies on minute differences in the timing and intensity of sound arriving at both ears. Neurons of the lateral superior olive (LSO) in the brainstem process these interaural disparities by precisely detecting excitatory and inhibitory synaptic inputs. Aging generally induces selective loss of inhibitory synaptic transmission along the entire auditory pathways, including the reduction of inhibitory afferents to LSO. Electrophysiological recordings in animals, however, reported only minor functional changes in aged LSO. The perplexing discrepancy between anatomical and physiological observations suggests a role for activity-dependent plasticity that would help neurons retain their binaural tuning function despite loss of inhibitory inputs. To explore this hypothesis, we use a computational model of LSO to investigate mechanisms underlying the observed functional robustness against age-related loss of inhibitory inputs. The LSO model is an integrate-and-fire type enhanced with a small amount of low-voltage activated potassium conductance and driven with (in)homogeneous Poissonian inputs. Without synaptic input loss, model spike rates varied smoothly with interaural time and level differences, replicating empirical tuning properties of LSO. By reducing the number of inhibitory afferents to mimic age-related loss of inhibition, overall spike rates increased, which negatively impacted binaural tuning performance, measured as modulation depth and neuronal discriminability. To simulate a recovery process compensating for the loss of inhibitory fibers, the strength of remaining inhibitory inputs was increased. By this modification, effects of inhibition loss on binaural tuning were considerably weakened, leading to an improvement of functional performance. These neuron-level observations were further confirmed by population modeling, in which binaural tuning properties of multiple LSO neurons were varied according to empirical measurements. These results demonstrate the plausibility that homeostatic plasticity could effectively counteract known age-dependent loss of inhibitory fibers in LSO and suggest that behavioral degradation of sound localization might originate from changes occurring more centrally.


Assuntos
Envelhecimento/fisiologia , Neurônios , Localização de Som/fisiologia , Complexo Olivar Superior , Animais , Vias Auditivas/fisiologia , Tronco Encefálico/fisiologia , Gatos , Biologia Computacional , Sinais (Psicologia) , Humanos , Camundongos , Modelos Neurológicos , Neurônios/citologia , Neurônios/fisiologia , Ratos , Complexo Olivar Superior/citologia , Complexo Olivar Superior/fisiologia
5.
PLoS One ; 16(6): e0253229, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34133461

RESUMO

OBJECTIVE: This study aimed to look for a possible relationship between thyrotropin (TSH) values from neonatal bloodspot screening testing and newborn lower auditory pathway myelinization evaluated using the brainstem evoked response audiometry (ABR) test. METHODS: Sixty-two healthy full-term newborns without perinatal problems were enrolled in the study. TSH results were collected from neonatal bloodspot screening data and were below the test cut-off level (15µUI/mL). The TSH test was performed between three and seven days, and the ABR test was performed in the first 28 days of life. The newborns were divided into two groups: Group 1 (n = 35), TSH between 0 and 5µUI/mL, and group 2 (n = 27), TSH between 5 and 15µUI/mL. Data are presented as mean ± SD, median, or percentage, depending on the variable. RESULTS: Wave latency and interpeak interval values for Groups 1 and 2 were as follows: Wave I: 1.8 ± 0.1 and 1.7 ± 0.1; Wave III: 4.4 ± 0.1 and 4.4 ± 0.1; Wave V: 6.9 ± 0.1 and 6.9 ± 0.1; interval I-III: 2.6 ± 0.1 and 2.6 ± 0.1; interval I-V: 5.1 ± 0.1 and 5.1 ± 0.1; interval III-V: 2.4 ± 0.1 and 2.4 ± 0.1. There were no significant differences in ABR parameters between groups 1 and 2 (p > 0.05). Multiple regression analysis showed a slight significant negative correlation between TSH and wave I values (standardized ß = -0.267; p = 0.036), without observing any relationship with the other ABR waves recorded. CONCLUSIONS: This study investigated the relationship of TSH and auditory myelinization evaluated by ABR. It did not show a significant change in lower auditory pathway myelinization according to TSH levels in newborns with TSH screening levels lower than 15 µUI/mL.


Assuntos
Vias Auditivas , Tireotropina/sangue , Adulto , Audiometria de Resposta Evocada , Vias Auditivas/crescimento & desenvolvimento , Vias Auditivas/fisiologia , Hipotireoidismo Congênito/sangue , Hipotireoidismo Congênito/fisiopatologia , Estudos Transversais , Feminino , Humanos , Recém-Nascido , Masculino
6.
Elife ; 102021 05 24.
Artigo em Inglês | MEDLINE | ID: mdl-34028350

RESUMO

The mechanisms that govern thalamocortical transmission are poorly understood. Recent data have shown that sensory stimuli elicit activity in ensembles of cortical neurons that recapitulate stereotyped spontaneous activity patterns. Here, we elucidate a possible mechanism by which gating of patterned population cortical activity occurs. In this study, sensory-evoked all-or-none cortical population responses were observed in the mouse auditory cortex in vivo and similar stochastic cortical responses were observed in a colliculo-thalamocortical brain slice preparation. Cortical responses were associated with decreases in auditory thalamic synaptic inhibition and increases in thalamic synchrony. Silencing of corticothalamic neurons in layer 6 (but not layer 5) or the thalamic reticular nucleus linearized the cortical responses, suggesting that layer 6 corticothalamic feedback via the thalamic reticular nucleus was responsible for gating stochastic cortical population responses. These data implicate a corticothalamic-thalamic reticular nucleus circuit that modifies thalamic neuronal synchronization to recruit populations of cortical neurons for sensory representations.


Assuntos
Córtex Auditivo/fisiologia , Vias Auditivas/fisiologia , Percepção Auditiva , Sincronização Cortical , Audição , Filtro Sensorial , Transmissão Sináptica , Núcleos Talâmicos/fisiologia , Estimulação Acústica , Animais , Córtex Auditivo/metabolismo , Vias Auditivas/metabolismo , Estimulação Elétrica , Potenciais Evocados Auditivos , Feminino , Masculino , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Inibição Neural , Núcleos Talâmicos/metabolismo , Fatores de Tempo
7.
Nat Commun ; 12(1): 2438, 2021 04 26.
Artigo em Inglês | MEDLINE | ID: mdl-33903596

RESUMO

Cortical and limbic brain areas are regarded as centres for learning. However, how thalamic sensory relays participate in plasticity upon associative learning, yet support stable long-term sensory coding remains unknown. Using a miniature microscope imaging approach, we monitor the activity of populations of auditory thalamus (medial geniculate body) neurons in freely moving mice upon fear conditioning. We find that single cells exhibit mixed selectivity and heterogeneous plasticity patterns to auditory and aversive stimuli upon learning, which is conserved in amygdala-projecting medial geniculate body neurons. Activity in auditory thalamus to amygdala-projecting neurons stabilizes single cell plasticity in the total medial geniculate body population and is necessary for fear memory consolidation. In contrast to individual cells, population level encoding of auditory stimuli remained stable across days. Our data identifies auditory thalamus as a site for complex neuronal plasticity in fear learning upstream of the amygdala that is in an ideal position to drive plasticity in cortical and limbic brain areas. These findings suggest that medial geniculate body's role goes beyond a sole relay function by balancing experience-dependent, diverse single cell plasticity with consistent ensemble level representations of the sensory environment to support stable auditory perception with minimal affective bias.


Assuntos
Vias Auditivas/fisiologia , Plasticidade Celular/fisiologia , Aprendizagem/fisiologia , Plasticidade Neuronal/fisiologia , Tálamo/fisiologia , Estimulação Acústica , Tonsila do Cerebelo/citologia , Tonsila do Cerebelo/fisiologia , Animais , Percepção Auditiva/fisiologia , Condicionamento Clássico/fisiologia , Medo/fisiologia , Corpos Geniculados/citologia , Corpos Geniculados/fisiologia , Camundongos Endogâmicos C57BL , Neurônios/fisiologia , Tálamo/citologia
8.
Nat Commun ; 12(1): 2449, 2021 04 27.
Artigo em Inglês | MEDLINE | ID: mdl-33907194

RESUMO

In the developing auditory system, spontaneous activity generated in the cochleae propagates into the central nervous system to promote circuit formation. The effects of peripheral firing patterns on spontaneous activity in the central auditory system are not well understood. Here, we describe wide-spread bilateral coupling of spontaneous activity that coincides with the period of transient efferent modulation of inner hair cells from the brainstem medial olivocochlear system. Knocking out α9/α10 nicotinic acetylcholine receptors, a requisite part of the efferent pathway, profoundly reduces bilateral correlations. Pharmacological and chemogenetic experiments confirm that the efferent system is necessary for normal bilateral coupling. Moreover, auditory sensitivity at hearing onset is reduced in the absence of pre-hearing efferent modulation. Together, these results demonstrate how afferent and efferent pathways collectively shape spontaneous activity patterns and reveal the important role of efferents in coordinating bilateral spontaneous activity and the emergence of functional responses during the prehearing period.


Assuntos
Vias Auditivas/fisiologia , Cóclea/fisiologia , Vias Eferentes/fisiologia , Retroalimentação Fisiológica , Receptores Nicotínicos/genética , Estimulação Acústica , Animais , Vias Auditivas/citologia , Cóclea/citologia , Lateralidade Funcional/fisiologia , Expressão Gênica , Células Ciliadas Auditivas Internas/citologia , Células Ciliadas Auditivas Internas/fisiologia , Colículos Inferiores/citologia , Colículos Inferiores/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Núcleo Olivar/citologia , Núcleo Olivar/fisiologia , Receptores Nicotínicos/deficiência
9.
PLoS Biol ; 19(4): e3000751, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33848299

RESUMO

Across many species, scream calls signal the affective significance of events to other agents. Scream calls were often thought to be of generic alarming and fearful nature, to signal potential threats, with instantaneous, involuntary, and accurate recognition by perceivers. However, scream calls are more diverse in their affective signaling nature than being limited to fearfully alarming a threat, and thus the broader sociobiological relevance of various scream types is unclear. Here we used 4 different psychoacoustic, perceptual decision-making, and neuroimaging experiments in humans to demonstrate the existence of at least 6 psychoacoustically distinctive types of scream calls of both alarming and non-alarming nature, rather than there being only screams caused by fear or aggression. Second, based on perceptual and processing sensitivity measures for decision-making during scream recognition, we found that alarm screams (with some exceptions) were overall discriminated the worst, were responded to the slowest, and were associated with a lower perceptual sensitivity for their recognition compared with non-alarm screams. Third, the neural processing of alarm compared with non-alarm screams during an implicit processing task elicited only minimal neural signal and connectivity in perceivers, contrary to the frequent assumption of a threat processing bias of the primate neural system. These findings show that scream calls are more diverse in their signaling and communicative nature in humans than previously assumed, and, in contrast to a commonly observed threat processing bias in perceptual discriminations and neural processes, we found that especially non-alarm screams, and positive screams in particular, seem to have higher efficiency in speeded discriminations and the implicit neural processing of various scream types in humans.


Assuntos
Percepção Auditiva/fisiologia , Discriminação Psicológica/fisiologia , Medo/psicologia , Reconhecimento de Voz/fisiologia , Adulto , Vias Auditivas/diagnóstico por imagem , Vias Auditivas/fisiologia , Encéfalo/diagnóstico por imagem , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Reconhecimento Fisiológico de Modelo/fisiologia , Reconhecimento Psicológico/fisiologia , Caracteres Sexuais , Adulto Jovem
10.
Neuroimage ; 235: 118014, 2021 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-33794356

RESUMO

Perceiving speech-in-noise (SIN) demands precise neural coding between brainstem and cortical levels of the hearing system. Attentional processes can then select and prioritize task-relevant cues over competing background noise for successful speech perception. In animal models, brainstem-cortical interplay is achieved via descending corticofugal projections from cortex that shape midbrain responses to behaviorally-relevant sounds. Attentional engagement of corticofugal feedback may assist SIN understanding but has never been confirmed and remains highly controversial in humans. To resolve these issues, we recorded source-level, anatomically constrained brainstem frequency-following responses (FFRs) and cortical event-related potentials (ERPs) to speech via high-density EEG while listeners performed rapid SIN identification tasks. We varied attention with active vs. passive listening scenarios whereas task difficulty was manipulated with additive noise interference. Active listening (but not arousal-control tasks) exaggerated both ERPs and FFRs, confirming attentional gain extends to lower subcortical levels of speech processing. We used functional connectivity to measure the directed strength of coupling between levels and characterize "bottom-up" vs. "top-down" (corticofugal) signaling within the auditory brainstem-cortical pathway. While attention strengthened connectivity bidirectionally, corticofugal transmission disengaged under passive (but not active) SIN listening. Our findings (i) show attention enhances the brain's transcription of speech even prior to cortex and (ii) establish a direct role of the human corticofugal feedback system as an aid to cocktail party speech perception.


Assuntos
Atenção/fisiologia , Audição/fisiologia , Ruído , Percepção da Fala/fisiologia , Estimulação Acústica , Adolescente , Vias Auditivas/fisiologia , Percepção Auditiva , Tronco Encefálico/fisiologia , Córtex Cerebral/fisiologia , Conectoma , Eletroencefalografia , Feminino , Humanos , Masculino , Mascaramento Perceptivo
11.
Mol Cell Neurosci ; 112: 103609, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33662542

RESUMO

Sound information encoding within the initial synapses in the auditory brainstem requires reliable and precise synaptic transmission in response to rapid and large fluctuations in action potential (AP) firing rates. The magnitude and location of Ca2+ entry through voltage-gated Ca2+ channels (CaV) in the presynaptic terminal are key determinants in triggering AP-mediated release. In the mammalian central nervous system (CNS), the CaV2.1 subtype is the critical subtype for CNS function, since it is the most efficient CaV2 subtype in triggering AP-mediated synaptic vesicle (SV) release. Auditory brainstem synapses utilize CaV2.1 to sustain fast and repetitive SV release to encode sound information. Therefore, understanding the presynaptic mechanisms that control CaV2.1 localization, organization and biophysical properties are integral to understanding auditory processing. Here, we review our current knowledge about the control of presynaptic CaV2 abundance and organization in the auditory brainstem and impact on the regulation of auditory processing.


Assuntos
Tronco Encefálico/fisiologia , Canais de Cálcio Tipo N/fisiologia , Potenciais Evocados Auditivos do Tronco Encefálico/fisiologia , Ativação do Canal Iônico/fisiologia , Proteínas do Tecido Nervoso/fisiologia , Terminações Pré-Sinápticas/fisiologia , Animais , Vias Auditivas/fisiologia , Cálcio/metabolismo , Canais de Cálcio Tipo N/química , Humanos , Transporte de Íons , Mamíferos/fisiologia , Proteínas do Tecido Nervoso/química , Domínios Proteicos , Subunidades Proteicas , Transmissão Sináptica/fisiologia , Vesículas Sinápticas/metabolismo
12.
J Neurosci ; 41(18): 4073-4087, 2021 05 05.
Artigo em Inglês | MEDLINE | ID: mdl-33731448

RESUMO

There is much debate about the existence and function of neural oscillatory mechanisms in the auditory system. The frequency-following response (FFR) is an index of neural periodicity encoding that can provide a vehicle to study entrainment in frequency ranges relevant to speech and music processing. Criteria for entrainment include the presence of poststimulus oscillations and phase alignment between stimulus and endogenous activity. To test the hypothesis of entrainment, in experiment 1 we collected FFR data for a repeated syllable using magnetoencephalography (MEG) and electroencephalography in 20 male and female human adults. We observed significant oscillatory activity after stimulus offset in auditory cortex and subcortical auditory nuclei, consistent with entrainment. In these structures, the FFR fundamental frequency converged from a lower value over 100 ms to the stimulus frequency, consistent with phase alignment, and diverged to a lower value after offset, consistent with relaxation to a preferred frequency. In experiment 2, we tested how transitions between stimulus frequencies affected the MEG FFR to a train of tone pairs in 30 people. We found that the FFR was affected by the frequency of the preceding tone for up to 40 ms at subcortical levels, and even longer durations at cortical levels. Our results suggest that oscillatory entrainment may be an integral part of periodic sound representation throughout the auditory neuraxis. The functional role of this mechanism is unknown, but it could serve as a fine-scale temporal predictor for frequency information, enhancing stability and reducing susceptibility to degradation that could be useful in real-life noisy environments.SIGNIFICANCE STATEMENT Neural oscillations are proposed to be a ubiquitous aspect of neural function, but their contribution to auditory encoding is not clear, particularly at higher frequencies associated with pitch encoding. In a magnetoencephalography experiment, we found converging evidence that the frequency-following response has an oscillatory component according to established criteria: poststimulus resonance, progressive entrainment of the neural frequency to the stimulus frequency, and relaxation toward the original state on stimulus offset. In a second experiment, we found that the frequency and amplitude of the frequency-following response to tones are affected by preceding stimuli. These findings support the contribution of intrinsic oscillations to the encoding of sound, and raise new questions about their functional roles, possibly including stabilization and low-level predictive coding.


Assuntos
Córtex Auditivo/fisiologia , Estimulação Acústica , Adulto , Vias Auditivas/fisiologia , Percepção Auditiva , Eletroencefalografia , Feminino , Humanos , Magnetoencefalografia , Masculino , Percepção da Altura Sonora/fisiologia , Adulto Jovem
13.
Commun Biol ; 4(1): 322, 2021 03 10.
Artigo em Inglês | MEDLINE | ID: mdl-33692502

RESUMO

In the adult vertebrate brain, enzymatic removal of the extracellular matrix (ECM) is increasingly recognized to promote learning, memory recall, and restorative plasticity. The impact of the ECM on translaminar dynamics during cortical circuit processing is still not understood. Here, we removed the ECM in the primary auditory cortex (ACx) of adult Mongolian gerbils using local injections of hyaluronidase (HYase). Using laminar current-source density (CSD) analysis, we found layer-specific changes of the spatiotemporal synaptic patterns with increased cross-columnar integration and simultaneous weakening of early local sensory input processing within infragranular layers Vb. These changes had an oscillatory fingerprint within beta-band (25-36 Hz) selectively within infragranular layers Vb. To understand the laminar interaction dynamics after ECM digestion, we used time-domain conditional Granger causality (GC) measures to identify the increased drive of supragranular layers towards deeper infragranular layers. These results showed that ECM degradation altered translaminar cortical network dynamics with a stronger supragranular lead of the columnar response profile.


Assuntos
Córtex Auditivo/fisiologia , Percepção Auditiva , Potenciais Evocados Auditivos , Matriz Extracelular/fisiologia , Animais , Córtex Auditivo/efeitos dos fármacos , Córtex Auditivo/metabolismo , Vias Auditivas/fisiologia , Percepção Auditiva/efeitos dos fármacos , Potenciais Evocados Auditivos/efeitos dos fármacos , Matriz Extracelular/efeitos dos fármacos , Matriz Extracelular/metabolismo , Gerbillinae , Audição , Hialuronoglucosaminidase/administração & dosagem , Injeções , Masculino , Fatores de Tempo
14.
PLoS Comput Biol ; 17(3): e1008787, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33657098

RESUMO

Frequency modulation (FM) is a basic constituent of vocalisation in many animals as well as in humans. In human speech, short rising and falling FM-sweeps of around 50 ms duration, called formant transitions, characterise individual speech sounds. There are two representations of FM in the ascending auditory pathway: a spectral representation, holding the instantaneous frequency of the stimuli; and a sweep representation, consisting of neurons that respond selectively to FM direction. To-date computational models use feedforward mechanisms to explain FM encoding. However, from neuroanatomy we know that there are massive feedback projections in the auditory pathway. Here, we found that a classical FM-sweep perceptual effect, the sweep pitch shift, cannot be explained by standard feedforward processing models. We hypothesised that the sweep pitch shift is caused by a predictive feedback mechanism. To test this hypothesis, we developed a novel model of FM encoding incorporating a predictive interaction between the sweep and the spectral representation. The model was designed to encode sweeps of the duration, modulation rate, and modulation shape of formant transitions. It fully accounted for experimental data that we acquired in a perceptual experiment with human participants as well as previously published experimental results. We also designed a new class of stimuli for a second perceptual experiment to further validate the model. Combined, our results indicate that predictive interaction between the frequency encoding and direction encoding neural representations plays an important role in the neural processing of FM. In the brain, this mechanism is likely to occur at early stages of the processing hierarchy.


Assuntos
Córtex Auditivo/fisiologia , Vias Auditivas/fisiologia , Modelos Neurológicos , Percepção da Fala/fisiologia , Adulto , Biologia Computacional , Feminino , Humanos , Masculino , Adulto Jovem
15.
PLoS Comput Biol ; 17(2): e1008138, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33577553

RESUMO

Skilled behavior often displays signatures of Bayesian inference. In order for the brain to implement the required computations, neuronal activity must carry accurate information about the uncertainty of sensory inputs. Two major approaches have been proposed to study neuronal representations of uncertainty. The first one, the Bayesian decoding approach, aims primarily at decoding the posterior probability distribution of the stimulus from population activity using Bayes' rule, and indirectly yields uncertainty estimates as a by-product. The second one, which we call the correlational approach, searches for specific features of neuronal activity (such as tuning-curve width and maximum firing-rate) which correlate with uncertainty. To compare these two approaches, we derived a new normative model of sound source localization by Interaural Time Difference (ITD), that reproduces a wealth of behavioral and neural observations. We found that several features of neuronal activity correlated with uncertainty on average, but none provided an accurate estimate of uncertainty on a trial-by-trial basis, indicating that the correlational approach may not reliably identify which aspects of neuronal responses represent uncertainty. In contrast, the Bayesian decoding approach reveals that the activity pattern of the entire population was required to reconstruct the trial-to-trial posterior distribution with Bayes' rule. These results suggest that uncertainty is unlikely to be represented in a single feature of neuronal activity, and highlight the importance of using a Bayesian decoding approach when exploring the neural basis of uncertainty.


Assuntos
Modelos Neurológicos , Rede Nervosa/fisiologia , Localização de Som/fisiologia , Incerteza , Animais , Vias Auditivas/fisiologia , Teorema de Bayes , Comportamento Animal/fisiologia , Biologia Computacional , Humanos , Colículos Inferiores/fisiologia , Neurônios/fisiologia , Estrigiformes/fisiologia , Colículos Superiores/fisiologia
16.
Neuroimage ; 231: 117866, 2021 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-33592244

RESUMO

The frequency-following response (FFR) to periodic complex sounds has gained recent interest in auditory cognitive neuroscience as it captures with great fidelity the tracking accuracy of the periodic sound features in the ascending auditory system. Seminal studies suggested the FFR as a correlate of subcortical sound encoding, yet recent studies aiming to locate its sources challenged this assumption, demonstrating that FFR receives some contribution from the auditory cortex. Based on frequency-specific phase-locking capabilities along the auditory hierarchy, we hypothesized that FFRs to higher frequencies would receive less cortical contribution than those to lower frequencies, hence supporting a major subcortical involvement for these high frequency sounds. Here, we used a magnetoencephalographic (MEG) approach to trace the neural sources of the FFR elicited in healthy adults (N = 19) to low (89 Hz) and high (333 Hz) frequency sounds. FFRs elicited to the high and low frequency sounds were clearly observable on MEG and comparable to those obtained in simultaneous electroencephalographic recordings. Distributed source modeling analyses revealed midbrain, thalamic, and cortical contributions to FFR, arranged in frequency-specific configurations. Our results showed that the main contribution to the high-frequency sound FFR originated in the inferior colliculus and the medial geniculate body of the thalamus, with no significant cortical contribution. In contrast, the low-frequency sound FFR had a major contribution located in the auditory cortices, and also received contributions originating in the midbrain and thalamic structures. These findings support the multiple generator hypothesis of the FFR and are relevant for our understanding of the neural encoding of sounds along the auditory hierarchy, suggesting a hierarchical organization of periodicity encoding.


Assuntos
Estimulação Acústica/métodos , Córtex Auditivo/fisiologia , Vias Auditivas/fisiologia , Percepção Auditiva/fisiologia , Potenciais Evocados Auditivos/fisiologia , Magnetoencefalografia/métodos , Adulto , Eletroencefalografia/métodos , Feminino , Humanos , Masculino , Adulto Jovem
17.
J Neurophysiol ; 125(3): 887-902, 2021 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-33534648

RESUMO

The configuration of lizard ears, where sound can reach both surfaces of the eardrums, produces a strongly directional ear, but the subsequent processing of sound direction by the auditory pathway is unknown. We report here on directional responses from the first stage, the auditory nerve. We used laser vibrometry to measure eardrum responses in Tokay geckos and in the same animals recorded 117 auditory nerve single fiber responses to free-field sound from radially distributed speakers. Responses from all fibers showed strongly lateralized activity at all frequencies, with an ovoidal directivity that resembled the eardrum directivity. Geckos are vocal and showed pronounced nerve fiber directionality to components of the call. To estimate the accuracy with which a gecko could discriminate between sound sources, we computed the Fisher information (FI) for each neuron. FI was highest just contralateral to the midline, front and back. Thus, the auditory nerve could provide a population code for sound source direction, and geckos should have a high capacity to differentiate between midline sound sources. In brain, binaural comparisons, for example, by IE (ipsilateral excitatory, contralateral inhibitory) neurons, should sharpen the lateralized responses and extend the dynamic range of directionality.NEW & NOTEWORTHY In mammals, the two ears are unconnected pressure receivers, and sound direction is computed from binaural interactions in the brain, but in lizards, the eardrums interact acoustically, producing a strongly directional response. We show strongly lateralized responses from gecko auditory nerve fibers to directional sound stimulation and high Fisher information on either side of the midline. Thus, already the auditory nerve provides a population code for sound source direction in the gecko.


Assuntos
Estimulação Acústica/métodos , Vias Auditivas/fisiologia , Nervo Coclear/fisiologia , Localização de Som/fisiologia , Vibração , Animais , Feminino , Lagartos , Masculino
18.
Neurosci Lett ; 746: 135664, 2021 02 16.
Artigo em Inglês | MEDLINE | ID: mdl-33497718

RESUMO

Scalp-recorded frequency-following responses (FFRs) reflect a mixture of phase-locked activity across the auditory pathway. FFRs have been widely used as a neural barometer of complex listening skills, especially speech-in noise (SIN) perception. Applying individually optimized source reconstruction to speech-FFRs recorded via EEG (FFREEG), we assessed the relative contributions of subcortical [auditory nerve (AN), brainstem/midbrain (BS)] and cortical [bilateral primary auditory cortex, PAC] source generators with the aim of identifying which source(s) drive the brain-behavior relation between FFRs and SIN listening skills. We found FFR strength declined precipitously from AN to PAC, consistent with diminishing phase-locking along the ascending auditory neuroaxis. FFRs to the speech fundamental (F0) were robust to noise across sources, but were largest in subcortical sources (BS > AN > PAC). PAC FFRs were only weakly observed above the noise floor and only at the low pitch of speech (F0≈100 Hz). Brain-behavior regressions revealed (i) AN and BS FFRs were sufficient to describe listeners' QuickSIN scores and (ii) contrary to neuromagnetic (MEG) FFRs, neither left nor right PAC FFREEG related to SIN performance. Our findings suggest subcortical sources not only dominate the electrical FFR but also the link between speech-FFRs and SIN processing in normal-hearing adults as observed in previous EEG studies.


Assuntos
Estimulação Acústica/métodos , Córtex Auditivo/fisiologia , Vias Auditivas/fisiologia , Audição/fisiologia , Ruído/efeitos adversos , Percepção da Fala/fisiologia , Adulto , Eletroencefalografia/métodos , Potenciais Evocados Auditivos do Tronco Encefálico/fisiologia , Feminino , Humanos , Masculino , Adulto Jovem
19.
J Neurosci ; 41(1): 73-88, 2021 01 06.
Artigo em Inglês | MEDLINE | ID: mdl-33177068

RESUMO

The capacity for sensory systems to encode relevant information that is invariant to many stimulus changes is central to normal, real-world, cognitive function. This invariance is thought to be reflected in the complex spatiotemporal activity patterns of neural populations, but our understanding of population-level representational invariance remains coarse. Applied topology is a promising tool to discover invariant structure in large datasets. Here, we use topological techniques to characterize and compare the spatiotemporal pattern of coactive spiking within populations of simultaneously recorded neurons in the secondary auditory region caudal medial neostriatum of European starlings (Sturnus vulgaris). We show that the pattern of population spike train coactivity carries stimulus-specific structure that is not reducible to that of individual neurons. We then introduce a topology-based similarity measure for population coactivity that is sensitive to invariant stimulus structure and show that this measure captures invariant neural representations tied to the learned relationships between natural vocalizations. This demonstrates one mechanism whereby emergent stimulus properties can be encoded in population activity, and shows the potential of applied topology for understanding invariant representations in neural populations.SIGNIFICANCE STATEMENT Information in neural populations is carried by the temporal patterns of spikes. We applied novel mathematical tools from the field of algebraic topology to quantify the structure of these temporal patterns. We found that, in a secondary auditory region of a songbird, these patterns reflected invariant information about a learned stimulus relationship. These results demonstrate that topology provides a novel approach for characterizing neural responses that is sensitive to invariant relationships that are critical for the perception of natural stimuli.


Assuntos
Córtex Auditivo/fisiologia , Fenômenos Eletrofisiológicos , Aves Canoras/fisiologia , Estorninhos/fisiologia , Estimulação Acústica , Algoritmos , Animais , Vias Auditivas/citologia , Vias Auditivas/fisiologia , Condicionamento Operante , Potenciais Evocados Auditivos/fisiologia , Feminino , Masculino , Modelos Neurológicos , Neostriado/citologia , Neostriado/fisiologia , Neurônios/fisiologia , Vocalização Animal/fisiologia
20.
J Neurosci ; 41(4): 674-688, 2021 01 27.
Artigo em Inglês | MEDLINE | ID: mdl-33268542

RESUMO

The medial nucleus of trapezoid body (MNTB) is a major source of inhibition in auditory brainstem circuitry. The MNTB projects well-timed inhibitory output to principal sound-localization nuclei in the superior olive (SOC) as well as other computationally important centers. Acoustic information is conveyed to MNTB neurons through a single calyx of Held excitatory synapse arising from the cochlear nucleus. The encoding efficacy of this large synapse depends on its activity rate, which is primarily determined by sound intensity and stimulus frequency. However, MNTB activity rate is additionally influenced by inhibition and possibly neuromodulatory inputs, albeit their functional role is unclear. Happe and Morley (2004) discovered prominent expression of α7 nAChRs in rat SOC, suggesting possible engagement of ACh-mediated modulation of neural activity in the MNTB. However, the existence and nature of this putative modulation have never been physiologically demonstrated. We probed nicotinic cholinergic influences on acoustic responses of MNTB neurons from adult gerbils (Meriones unguiculatus) of either sex. We recorded tone-evoked MNTB single-neuron activity in vivo using extracellular single-unit recording. Piggyback multibarrel electrodes enabled pharmacological manipulation of nAChRs by reversibly applying antagonists to two receptor types, α7 and α4ß2. We observed that tone-evoked responses are dependent on ACh modulation by both nAChR subtypes. Spontaneous activity was not affected by antagonist application. Functionally, we demonstrate that ACh contributes to sustaining high discharge rates and enhances signal encoding efficacy. Additionally, we report anatomic evidence revealing novel cholinergic projections to MNTB arising from pontine and superior olivary nuclei.SIGNIFICANCE STATEMENT This study is the first to physiologically probe how acetylcholine, a pervasive neuromodulator in the brain, influences the encoding of acoustic information by the medial nucleus of trapezoid body, the most prominent source of inhibition in brainstem sound-localization circuitry. We demonstrate that this cholinergic input enhances neural discrimination of tones from noise stimuli, which may contribute to processing important acoustic signals, such as speech. Additionally, we describe novel anatomic projections providing cholinergic input to the MNTB. Together, these findings shed new light on the contribution of neuromodulation to fundamental computational processes in auditory brainstem circuitry and to a more holistic understanding of modulatory influences in sensory processing.


Assuntos
Estimulação Acústica , Sistema Nervoso Parassimpático/fisiologia , Corpo Trapezoide/fisiologia , Acetilcolina/fisiologia , Animais , Vias Auditivas/fisiologia , Feminino , Gerbillinae , Masculino , Neurônios/fisiologia , Núcleo Olivar/fisiologia , Ponte/fisiologia , Receptores Nicotínicos/fisiologia , Som , Receptor Nicotínico de Acetilcolina alfa7/fisiologia
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