scholarly journals Role of Mammalian Auditory Cortex in the Perception of Elementary Sound Properties

2001 ◽  
Vol 85 (6) ◽  
pp. 2350-2358 ◽  
Author(s):  
Sanjiv K. Talwar ◽  
Pawel G. Musial ◽  
George L. Gerstein
Keyword(s):  
Auditory Cortex ◽  
Time Course ◽  
Auditory Evoked Potentials ◽  
Mammalian Species ◽  
Sound Intensity ◽  
Primary Auditory Cortex ◽  
Normal Hearing ◽  
Auditory Task ◽  
Experimental Conditions

Studies in several mammalian species have demonstrated that bilateral ablations of the auditory cortex have little effect on simple sound intensity and frequency-based behaviors. In the rat, for example, early experiments have shown that auditory ablations result in virtually no effect on the rat's ability to either detect tones or discriminate frequencies. Such lesion experiments, however, typically examine an animal's performance some time after recovery from ablation surgery. As such, they demonstrate that the cortex is not essential for simple auditory behaviors in the long run. Our study further explores the role of cortex in basic auditory perception by examining whether the cortex is normally involved in these behaviors. In these experiments we reversibly inactivated the rat primary auditory cortex (AI) using the GABA agonist muscimol, while the animals performed a simple auditory task. At the same time we monitored the rat's auditory activity by recording auditory evoked potentials (AEP) from the cortical surface. In contrast to lesion studies, the rapid time course of these experimental conditions preclude reorganization of the auditory system that might otherwise compensate for the loss of cortical processing. Soon after bilateral muscimol application to their AI region, our rats exhibited an acute and profound inability to detect tones. After a few hours this state was followed by a gradual recovery of normal hearing, first of tone detection and, much later, of the ability to discriminate frequencies. Surface muscimol application, at the same time, drastically altered the normal rat AEP. Some of the normal AEP components vanished nearly instantaneously to unveil an underlying waveform, whose size was related to the severity of accompanying behavioral deficits. These results strongly suggest that the cortex is directly involved in basic acoustic processing. Along with observations from accompanying multiunit experiments that related the AEP to AI neuronal activity, our results suggest that a critical amount of activity in the auditory cortex is necessary for normal hearing. It is likely that the involvement of the cortex in simple auditory perceptions has hitherto not been clearly understood because of underlying recovery processes that, in the long-term, safeguard fundamental auditory abilities after cortical injury.

scholarly journals Cell-specific gain modulation by synaptically released zinc in cortical circuits of audition

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Charles T Anderson ◽  
Manoj Kumar ◽  
Shanshan Xiong ◽  
Thanos Tzounopoulos
Keyword(s):  
Auditory Cortex ◽  
Ex Vivo ◽  
Gain Control ◽  
Sound Intensity ◽  
Primary Auditory Cortex ◽  
Synaptic Activity ◽  
Excitatory Synapses ◽  
Excitatory Neurotransmission

In many excitatory synapses, mobile zinc is found within glutamatergic vesicles and is coreleased with glutamate. Ex vivo studies established that synaptically released (synaptic) zinc inhibits excitatory neurotransmission at lower frequencies of synaptic activity but enhances steady state synaptic responses during higher frequencies of activity. However, it remains unknown how synaptic zinc affects neuronal processing in vivo. Here, we imaged the sound-evoked neuronal activity of the primary auditory cortex in awake mice. We discovered that synaptic zinc enhanced the gain of sound-evoked responses in CaMKII-expressing principal neurons, but it reduced the gain of parvalbumin- and somatostatin-expressing interneurons. This modulation was sound intensity-dependent and, in part, NMDA receptor-independent. By establishing a previously unknown link between synaptic zinc and gain control of auditory cortical processing, our findings advance understanding about cortical synaptic mechanisms and create a new framework for approaching and interpreting the role of the auditory cortex in sound processing.

Role of the primary auditory cortex in auditory selective attention studied by whole-head neuromagnetometer

1998 ◽  
Vol 7 (2) ◽  
pp. 99-109 ◽  
Author(s):  
Naohito Fujiwara ◽  
Takashi Nagamine ◽  
Makoto Imai ◽  
Tomohiro Tanaka ◽  
Hiroshi Shibasaki
Keyword(s):  
Selective Attention ◽  
Auditory Cortex ◽  
Primary Auditory Cortex ◽  
Auditory Selective Attention

scholarly journals The Role of Adaptation in Generating Monotonic Rate Codes in Auditory Cortex

2019 ◽  
Author(s):  
Jong Hoon Lee ◽  
Xiaoqin Wang ◽  
Daniel Bendor
Keyword(s):  
Auditory Cortex ◽  
Single Unit ◽  
Discharge Rate ◽  
Primary Auditory Cortex ◽  
Stimulus Presentation ◽  
Single Neurons ◽  
Short Term ◽  
Acoustic Stimuli ◽  
Biophysical Mechanism

AbstractIn primary auditory cortex, slowly repeated acoustic events are represented temporally by phase-locked activity of single neurons. Single-unit studies in awake marmosets (Callithrix jacchus) have shown that a sub-population of these neurons also monotonically increase or decrease their average discharge rate during stimulus presentation for higher repetition rates. Building on a computational single-neuron model that generates phase-locked responses with stimulus evoked excitation followed by strong inhibition, we find that stimulus-evoked short-term depression is sufficient to produce synchronized monotonic positive and negative responses to slowly repeated stimuli. By exploring model robustness and comparing it to other models for adaptation to such stimuli, we conclude that short-term depression best explains our observations in single-unit recordings in awake marmosets. Using this model, we emulated how single neurons could encode and decode multiple aspects of an acoustic stimuli with the monotonic positive and negative encoding of a given stimulus feature. Together, our results show that a simple biophysical mechanism in single neurons can allow a more complex encoding and decoding of acoustic stimuli.

scholarly journals Time Course of Forward Masking Tuning Curves in Cat Primary Auditory Cortex

1997 ◽  
Vol 77 (2) ◽  
pp. 923-943 ◽  
Author(s):  
Michael Brosch ◽  
Christoph E. Schreiner
Keyword(s):  
Receptive Field ◽  
Auditory Cortex ◽  
Stimulus Onset Asynchrony ◽  
Time Course ◽  
Tuning Curve ◽  
Primary Auditory Cortex ◽  
Stimulus Onset ◽  
Cortical Cells ◽  
Tuning Curves ◽  
Onset Asynchrony

Brosch, Michael and Christoph E. Schreiner. Time course of forward masking tuning curves in cat primary auditory cortex. J. Neurophysiol. 77: 923–943, 1997. Nonsimultaneous two-tone interactions were studied in the primary auditory cortex of anesthetized cats. Poststimulatory effects of pure tone bursts (masker) on the evoked activity of a fixed tone burst (probe) were investigated. The temporal interval from masker onset to probe onset (stimulus onset asynchrony), masker frequency, and intensity were parametrically varied. For all of the 53 single units and 58 multiple-unit clusters, the neural activity of the probe signal was either inhibited, facilitated, and/or delayed by a limited set of masker stimuli. The stimulus range from which forward inhibition of the probe was induced typically was centered at and had approximately the size of the neuron's excitatory receptive field. This “masking tuning curve” was usually V shaped, i.e., the frequency range of inhibiting masker stimuli increased with the masker intensity. Forward inhibition was induced at the shortest stimulus onset asynchrony between masker and probe. With longer stimulus onset asynchronies, the frequency range of inhibiting maskers gradually became smaller. Recovery from forward inhibition occurred first at the lower- and higher-frequency borders of the masking tuning curve and lasted the longest for frequencies close to the neuron's characteristic frequency. The maximal duration of forward inhibition was measured as the longest period over which reduction of probe responses was observed. It was in the range of 53–430 ms, with an average of 143 ± 71 (SD) ms. Amount, duration and type of forward inhibition were weakly but significantly correlated with “static” neural receptive field properties like characteristic frequency, bandwidth, and latency. For the majority of neurons, the minimal inhibitory masker intensity increased when the stimulus onset asynchrony became longer. In most cases the highest masker intensities induced the longest forward inhibition. A significant number of neurons, however, exhibited longest periods of inhibition after maskers of intermediate intensity. The results show that the ability of cortical cells to respond with an excitatory activity depends on the temporal stimulus context. Neurons can follow higher repetition rates of stimulus sequences when successive stimuli differ in their spectral content. The differential sensitivity to temporal sound sequences within the receptive field of cortical cells as well as across different cells could contribute to the neural processing of temporally structured stimuli like speech and animal vocalizations.

Single-Neuron Responses to Rapidly Presented Temporal Sequences in the Primary Auditory Cortex of the Awake Macaque Monkey

2007 ◽  
Vol 97 (2) ◽  
pp. 1726-1737 ◽  
Author(s):  
M. L. Phan ◽  
G. H. Recanzone
Keyword(s):  
Auditory Cortex ◽  
Cortical Neurons ◽  
Primary Auditory Cortex ◽  
Macaque Monkey ◽  
Auditory Task ◽  
Single Neurons ◽  
Animal Vocalizations ◽  
Early Processing ◽  
The Individual ◽  
Temporal Rate

One fundamental process of the auditory system is to process rapidly occurring acoustic stimuli, which are fundamental components of complex stimuli such as animal vocalizations and human speech. Although the auditory cortex is known to subserve the perception of acoustic temporal events, relatively little is currently understood about how single neurons respond to such stimuli. We recorded the responses of single neurons in the primary auditory cortex of alert monkeys performing an auditory task. The stimuli consisted of four tone pips with equal duration and interpip interval, with the first and last pip of the sequence being near the characteristic frequency of the neuron under study. We manipulated the rate of presentation, the frequency of the middle two tone pips, and the order by which they were presented. Our results indicate that single cortical neurons are ineffective at responding to the individual tone pips of the sequence for pip durations of <12 ms, but did begin to respond synchronously to each pip of the sequence at 18-ms durations. In addition, roughly 40% of the neurons tested were able to discriminate the order that the two middle tone pips were presented in at durations of ≥24 ms. These data place the primate primary auditory cortex at an early processing stage of temporal rate discrimination.

scholarly journals Competition for neuronal resources: how hallucinations make themselves heard

2007 ◽  
Vol 190 (1) ◽  
pp. 57-62 ◽  
Author(s):  
Daniela Hubl ◽  
Thomas Koenig ◽  
Werner K. Strik ◽  
Lester Melie Garcia ◽  
Thomas Dierks
Keyword(s):  
Auditory Cortex ◽  
Evoked Potentials ◽  
Auditory Evoked Potentials ◽  
Primary Auditory Cortex ◽  
Auditory Attention ◽  
Auditory Hallucinations ◽  
Auditory Stimuli ◽  
Simultaneous Occurrence ◽  
Auditory Verbal Hallucinations ◽  
External Stimuli

BackgroundHallucinations are perceptions in the absence of a corresponding external sensory stimulus. However, during auditory verbal hallucinations, activation of the primary auditory cortex has been described.AimsThe objective of this study was to investigate whether this activation of the auditory cortex contributes essentially to the character of hallucinations and attributes them to alien sources, or whether the auditory activation is a sign of increased general auditory attention to external sounds.MethodThe responsiveness of the auditory cortex was investigated by auditory evoked potentials (N100) during the simultaneous occurrence of hallucinations and external stimuli. Evoked potentials were computed separately for periods with and without hallucinations; N100 power, topography and brain electrical sources were analysed.ResultsHallucinations lowered the N100 amplitudes and changed the topography, presumably due to a reduced left temporal responsivity.ConclusionsThis finding indicates competition between auditory stimuli and hallucinations for physiological resources in the primary auditory cortex. The abnormal activation of the primary auditory cortex may thus be a constituent of auditory hallucinations.

scholarly journals Spectral Resolution of Monkey Primary Auditory Cortex (A1) Revealed With Two-Noise Masking

2006 ◽  
Vol 96 (3) ◽  
pp. 1105-1115 ◽  
Author(s):  
Yonatan I. Fishman ◽  
Mitchell Steinschneider
Keyword(s):  
Auditory Cortex ◽  
Spectral Resolution ◽  
Goodness Of Fit ◽  
Auditory Evoked Potentials ◽  
Current Source ◽  
Primary Auditory Cortex ◽  
Frequency Separation ◽  
Frequency Resolution ◽  
Noise Masking ◽  
Neural Populations

An important function of the auditory nervous system is to analyze the frequency content of environmental sounds. The neural structures involved in determining psychophysical frequency resolution remain unclear. Using a two-noise masking paradigm, the present study investigates the spectral resolution of neural populations in primary auditory cortex (A1) of awake macaques and the degree to which it matches psychophysical frequency resolution. Neural ensemble responses (auditory evoked potentials, multiunit activity, and current source density) evoked by a pulsed 60-dB SPL pure-tone signal fixed at the best frequency (BF) of the recorded neural populations were examined as a function of the frequency separation (ΔF) between the tone and two symmetrically flanking continuous 80-dB SPL, 50-Hz-wide bands of noise. ΔFs ranged from 0 to 50% of the BF, encompassing the range typically examined in psychoacoustic experiments. Responses to the signal were minimal for ΔF = 0% and progressively increased with ΔF, reaching a maximum at ΔF = 50%. Rounded exponential functions, used to model auditory filter shapes in psychoacoustic studies of frequency resolution, provided excellent fits to neural masking functions. Goodness-of-fit was greatest for response components in lamina 4 and lower lamina 3 and least for components recorded in more superficial cortical laminae. Physiological equivalent rectangular bandwidths (ERBs) increased with BF, measuring nearly 15% of the BF. These findings parallel results of psychoacoustic studies in both monkeys and humans, and thus indicate that a representation of perceptual frequency resolution is available at the level of A1.

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