scholarly journals Temporal Nonlinearity During Recovery From Sequential Inhibition by Neurons in the Cat Primary Auditory Cortex

2006 ◽  
Vol 95 (3) ◽  
pp. 1897-1907 ◽  
Author(s):  
Kyle T. Nakamoto ◽  
Jiping Zhang ◽  
Leonard M. Kitzes
Keyword(s):  
Auditory Cortex ◽  
Recovery Rate ◽  
Primary Auditory Cortex ◽  
Auditory Stimuli ◽  
Time Interval ◽  
Large Set ◽  
Strong Response ◽  
Preceding Stimulus ◽  
Sequential Inhibition ◽  
Response Area

Auditory stimuli occur most often in sequences rather than in isolation. It is therefore necessary to understand how responses to sounds occurring in sequences differ from responses to isolated sounds. Cells in primary auditory cortex (AI) respond to a large set of binaural stimuli when presented in isolation. The set of responses to such stimuli presented at one frequency comprises a level response area. A preceding binaural stimulus can reduce the size and magnitude of level response areas of AI cells. The present study focuses on the effects of the time interval between a preceding stimulus and the stimuli of a level response area in pentobarbital-anesthetized cats. After the offset of a preceding stimulus, the ability of AI cells to respond to succeeding stimuli varies dynamically in time. At short interstimulus intervals (ISI), a preceding stimulus can completely inhibit responses to succeeding stimuli. With increasing ISIs, AI cells respond first to binaural stimuli that evoke the largest responses in the control condition, i.e., not preceded by a stimulus. Recovery rate is nonlinear across the level response area; responses to these most-effective stimuli recover to 70% of control on average 187 ms before responses to other stimuli recover to 70% of their control sizes. During the tens to hundreds of milliseconds that a level response area is reduced in size and magnitude, the selectivity of AI cells is increased for stimuli that evoke the largest responses. This increased selectivity results from a temporal nonlinearity in the recovery of the level response area which protects responses to the most effective binaural stimuli. Thus in a sequence of effective stimuli, a given cell will respond selectively to only those stimuli that evoke a strong response when presented alone.

Modulation of Level Response Areas and Stimulus Selectivity of Neurons in Cat Primary Auditory Cortex

2005 ◽  
Vol 94 (4) ◽  
pp. 2263-2274 ◽  
Author(s):  
Jiping Zhang ◽  
Kyle T. Nakamoto ◽  
Leonard M. Kitzes
Keyword(s):  
Auditory Cortex ◽  
Conditioning Stimulus ◽  
Primary Auditory Cortex ◽  
Response Magnitude ◽  
Absolute Level ◽  
Preceding Stimulus ◽  
Dynamic Modulation ◽  
Acoustic Stimuli ◽  
Static Level ◽  
Response Area

Sounds commonly occur in sequences, such as in speech. It is therefore important to understand how the occurrence of one sound affects the response to a subsequent sound. We approached this question by determining how a conditioning stimulus alters the response areas of single neurons in the primary auditory cortex (AI) of barbiturate-anesthetized cats. The response areas consisted of responses to stimuli that varied in level at the two ears and delivered at the characteristic frequency of each cell. A binaural conditioning stimulus was then presented ≥50 ms before each of the stimuli comprising the level response area. An effective preceding stimulus alters the shape and severely reduces the size and response magnitude of the level response area. This ability of the preceding stimulus depends on its proximity in the level domain to the level response area, not on its absolute level or on the size of the response it evokes. Preceding stimuli evoke a nonlinear inhibition across the level response area that results in an increased selectivity of a cortical neuron for its preferred binaural stimuli. The selectivity of AI neurons during the processing of a stream of acoustic stimuli is likely to be restricted to a portion of their level response areas apparent in the tone-alone condition. Thus rather than being static, level response areas are fluid; they can vary greatly in extent, shape and response magnitude. The dynamic modulation of the level response area and level selectivity of AI neurons might be related to several tasks confronting the central auditory system.

Auditory Imagery Modulates Frequency-specific Areas in the Human Auditory Cortex

2013 ◽  
Vol 25 (2) ◽  
pp. 175-187 ◽  
Author(s):  
Jihoon Oh ◽  
Jae Hyung Kwon ◽  
Po Song Yang ◽  
Jaeseung Jeong
Keyword(s):  
Auditory Cortex ◽  
High Frequency ◽  
Low Frequency ◽  
Primary Auditory Cortex ◽  
Auditory Imagery ◽  
Neural Responses ◽  
Top Down ◽  
Visual Areas ◽  
Control Functional ◽  
Response Area

Neural responses in early sensory areas are influenced by top–down processing. In the visual system, early visual areas have been shown to actively participate in top–down processing based on their topographical properties. Although it has been suggested that the auditory cortex is involved in top–down control, functional evidence of topographic modulation is still lacking. Here, we show that mental auditory imagery for familiar melodies induces significant activation in the frequency-responsive areas of the primary auditory cortex (PAC). This activation is related to the characteristics of the imagery: when subjects were asked to imagine high-frequency melodies, we observed increased activation in the high- versus low-frequency response area; when the subjects were asked to imagine low-frequency melodies, the opposite was observed. Furthermore, we found that A1 is more closely related to the observed frequency-related modulation than R in tonotopic subfields of the PAC. Our findings suggest that top–down processing in the auditory cortex relies on a mechanism similar to that used in the perception of external auditory stimuli, which is comparable to early visual systems.

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.

Time course of tonal frequency-response-area of primary auditory cortex neurons in alert cats

2003 ◽  
Vol 46 (2) ◽  
pp. 145-152 ◽  
Author(s):  
Ling Qin ◽  
Toshihiro Kitama ◽  
Sohei Chimoto ◽  
Shuichi Sakayori ◽  
Yu Sato
Keyword(s):  
Auditory Cortex ◽  
Frequency Response ◽  
Time Course ◽  
Primary Auditory Cortex ◽  
Tonal Frequency ◽  
Alert Cats ◽  
Response Area

scholarly journals Lack of tonotopic organization of the auditory cortex in schizophrenia

2014 ◽  
Author(s):  
Thomas Ragole ◽  
Erin Slason ◽  
Peter Teale ◽  
Martin Reite ◽  
Donald C. Rojas
Keyword(s):  
Magnetic Field ◽  
Auditory Cortex ◽  
Cognitive Processes ◽  
Spatial Organization ◽  
Primary Auditory Cortex ◽  
Auditory Stimuli ◽  
Healthy Controls ◽  
Equivalent Current Dipole ◽  
Current Dipole ◽  
Tonotopic Organization

Background: Disorganization of tonotopy in the auditory cortex has been described in schizophrenia. Subjects with schizophrenia show little to no spatial organization of responses to different tone frequencies in the auditory cortex. Previous studies have called into question the use of MEG and the M100 response to assess tonotopy. This study seeks to replicate prior results of tonotopic disorganization in schizophrenia compared to healthy controls. Methods: The tonotopic organization for 400 Hz and 4,000 Hz sound in 19 patients with schizophrenia and 11 comparison subjects was determined using MEG by examining the M100 auditory-evoked magnetic field dipole in primary auditory cortex. The equivalent current dipole locations were then mapped and compared. Results: The previous result of a lack of tonotopy in subjects with schizophrenia was partly replicated. In control subjects, the 400 Hz tone auditory evoked field was found anterior to the 4000 Hz in the primary auditory cortex. Conclusions: The lack of tonotopic organization of the auditory cortex is replicable in patients with schizophrenia and suggests that the architecture underlying tonotopy in the auditory cortex is disordered. This result suggests possible alteration in the organization of the auditory cortex, which may in turn influence higher order cognitive processes by altering the perception of incoming auditory stimuli.

scholarly journals Lack of tonotopic organization of the auditory cortex in schizophrenia

2014 ◽  
Author(s):  
Thomas Ragole ◽  
Erin Slason ◽  
Peter Teale ◽  
Martin Reite ◽  
Donald C. Rojas
Keyword(s):  
Magnetic Field ◽  
Auditory Cortex ◽  
Cognitive Processes ◽  
Spatial Organization ◽  
Primary Auditory Cortex ◽  
Auditory Stimuli ◽  
Healthy Controls ◽  
Equivalent Current Dipole ◽  
Current Dipole ◽  
Tonotopic Organization

Background: Disorganization of tonotopy in the auditory cortex has been described in schizophrenia. Subjects with schizophrenia show little to no spatial organization of responses to different tone frequencies in the auditory cortex. Previous studies have called into question the use of MEG and the M100 response to assess tonotopy. This study seeks to replicate prior results of tonotopic disorganization in schizophrenia compared to healthy controls. Methods: The tonotopic organization for 400 Hz and 4,000 Hz sound in 19 patients with schizophrenia and 11 comparison subjects was determined using MEG by examining the M100 auditory-evoked magnetic field dipole in primary auditory cortex. The equivalent current dipole locations were then mapped and compared. Results: The previous result of a lack of tonotopy in subjects with schizophrenia was partly replicated. In control subjects, the 400 Hz tone auditory evoked field was found anterior to the 4000 Hz in the primary auditory cortex. Conclusions: The lack of tonotopic organization of the auditory cortex is replicable in patients with schizophrenia and suggests that the architecture underlying tonotopy in the auditory cortex is disordered. This result suggests possible alteration in the organization of the auditory cortex, which may in turn influence higher order cognitive processes by altering the perception of incoming auditory stimuli.

scholarly journals Amplitude modulation encoding in auditory cortex: Comparisons between the primary and middle lateral belt regions

2020 ◽  
Author(s):  
Jeffrey S. Johnson ◽  
Mamiko Niwa ◽  
Kevin N. O’Connor ◽  
Mitchell L. Sutter
Keyword(s):  
Auditory Cortex ◽  
Firing Rate ◽  
Amplitude Modulation ◽  
Single Unit ◽  
Modulation Depth ◽  
Phase Locking ◽  
Primary Auditory Cortex ◽  
Auditory Stimuli ◽  
Phase Lock ◽  
Basic Properties

ABSTRACTIn macaques, the middle lateral auditory cortex (ML) is a belt region adjacent to primary auditory cortex (A1) and believed to be at a hierarchically higher level. Although ML single-unit responses have been studied for several auditory stimuli, the ability of ML cells to encode amplitude modulation (AM) – an ability which has been widely studied in A1 – has not yet been characterized. Here we compare the responses of A1 and ML neurons to amplitude modulated (AM) noise in awake macaques. While several of the basic properties of A1 and ML responses to AM noise are similar, we found several key differences. ML neurons do not phase lock as strongly, are less likely to phase lock, and are more likely to respond in a non-synchronized fashion than A1 cells, consistent with a temporal-to-rate transformation as information ascends the auditory hierarchy. ML neurons tend to have lower temporally (phase-locking) based best modulation frequencies than A1. At the level of ML, neurons that decrease firing rate with increasing modulation depth become more common than in A1. In both A1 and ML we find a prevalent class of neurons with excitatory rate responses at lower modulation frequencies and suppressed rate responses relative to the unmodulated carrier at middle modulation frequencies.

scholarly journals Flexible reset and entrainment of delta oscillations in primate primary auditory cortex: modeling and experiment

2019 ◽  
Author(s):  
David A. Stanley ◽  
Arnaud Y. Falchier ◽  
Benjamin R. Pittman-Polletta ◽  
Peter Lakatos ◽  
Miles A. Whittington ◽  
...  
Keyword(s):  
Auditory Cortex ◽  
Speech Processing ◽  
Primary Auditory Cortex ◽  
Auditory Stimuli ◽  
Input Stimulus ◽  
Long Duration ◽  
Starting Point ◽  
Wide Range ◽  
Delta Oscillations

AbstractSalient auditory stimuli typically exhibit rhythmic temporal patterns. A growing body of evidence suggests that, in primary auditory cortex (A1), attention is associated with entrainment of delta rhythms (1 – 4 Hz) by these auditory stimuli. It is thought that this entrainment involves phase reset of ongoing spontaneous oscillations in A1 by thalamus matrix afferents, but precise mechanisms are unknown. Furthermore, naturalistic stimuli can vary widely in terms of their rhythmicity: some cycles can be longer than others and frequency can drift over time. It is not clear how the auditory system accommodates this natural variability. We show that in rhesus macaque monkey A1 in vivo, bottom-up gamma (40 Hz) click trains influence ongoing spontaneous delta rhythms by inducing an initial delta-timescale transient response, followed by entrainment to gamma and suppression of delta. We then construct a computational model to reproduce this effect, showing that transient thalamus matrix activation can reset A1 delta oscillations by directly activating deep (layer 5) IB cells, promoting bursting, and beginning a new delta cycle. In contrast, long duration gamma-rhythmic input stimuli induce a steady-state containing entrainment of superficial RS and FS cells at gamma, and suppression of delta oscillations. This suppression is achieved in the model by two complementary pathways. First, long-duration thalamus matrix input causes IB cells to switch from bursting to sparse firing, which disrupts the IB bursts associated with delta. Second, thalamus core input activates deep FS cells (by way of layer 4), which fire at gamma frequency and actively inhibit the delta oscillator. Together, these two fundamental operations of reset and suppression can respectively advance and delay the phase of the delta oscillator, allowing it to follow rhythms exhibiting the type of variability found in the natural environment. We discuss these findings in relation to functional implications for speech processing.Author summaryNeurons organize their firing into synchronous, rhythmic patterns. These neural oscillations have been shown to entrain to rhythmic stimuli in the external world, such as patterns of speech or patterns of movement. By entraining to a particular input stimulus, these oscillations are thought to help us attend to that stimulus and to exclude others. To understand how this synchronization emerges, we constructed a physiologically detailed mathematical model of the primary auditory cortex. By fitting this model to a variety of experimental data, we suggest fundamental mechanisms by which neurons of the auditory cortex can synchronize their activity to rhythmic external stimuli. This result will be useful for understanding the mechanism and limitations of oscillatory entrainment, which are thought to underlie the processing of naturalistic auditory inputs like speech or music. Furthermore, this model, though simplified, was shown to generalize and reproduce a wide range of experimental results, and can thus be used as a starting point for building more complex models of auditory cortex.

scholarly journals Organization of response areas in ferret primary auditory cortex

1993 ◽  
Vol 69 (2) ◽  
pp. 367-383 ◽  
Author(s):  
S. A. Shamma ◽  
J. W. Fleshman ◽  
P. R. Wiser ◽  
H. Versnel
Keyword(s):  
Auditory Cortex ◽  
Low Frequency ◽  
Primary Auditory Cortex ◽  
Asymmetry Index ◽  
Spectral Energy ◽  
Directional Sensitivity ◽  
Similar Response ◽  
Differential Distribution ◽  
The Asymmetry ◽  
Response Area

1. We studied the topographic organization of the response areas obtained from single- and multiunit recordings along the isofrequency planes of the primary auditory cortex in the barbiturate-anesthetized ferret. 2. Using a two-tone stimulus, we determined the excitatory and inhibitory portions of the response areas and then parameterized them in terms of an asymmetry index. The index measures the balance of excitatory and inhibitory influences around the best frequency (BF). 3. The sensitivity of responses to the direction of a frequency-modulated (FM) tone was tested and found to correlate strongly with the asymmetry index of the response areas. Specifically, cells with strong inhibition from frequencies above the BF preferred upward sweeps, and those from frequencies below the BF preferred downward sweeps. 4. Responses to spectrally shaped noise were also consistent with the asymmetry of the response areas. For instance, cells that were strongly inhibited by frequencies higher than the BF responded best to stimuli that contained least spectral energy above the BF, i.e., stimuli with the opposite asymmetry. 5. Columnar organization of the response area types was demonstrated in 66 single units from 16 penetrations. Consistent with this finding, it was also shown that response area asymmetry measured from recordings of a cluster of cells corresponded closely with those measured from its single-unit constituents. Thus, in a local region, most cells exhibited similar response area types and other response features, e.g., FM directional sensitivity. 6. The distribution of the asymmetry index values along the isofrequency planes revealed systematic changes in the symmetry of the response areas. At the center, response areas with narrow and symmetric inhibitory sidebands predominated. These gave way to asymmetric inhibition, with high-frequency inhibition (relative to the BF) becoming more effective caudally and low-frequency inhibition more effective rostrally. These response types tended to cluster along repeated bands that paralleled the tonotopic axis. 7. Response features that correlated with the response area types were also mapped along the isofrequency planes. Thus, in four animals, a map of FM directional sensitivity was shown to be superimposed on the response area map. Similarly, it was demonstrated in six animals that the spectral gradient of the most effective noise stimulus varied systematically along the isofrequency planes. 8. One functional implication of the response area organization is that cortical responses encode the locally averaged gradient of the acoustic spectrum by their differential distribution along the isofrequency planes. This enhances the representation of such features as the symmetry of spectral peaks and edges and the spectral envelope.(ABSTRACT TRUNCATED AT 400 WORDS)

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