Sparse Coding in Temporal Association Cortex Improves Complex Sound Discriminability

AbstractThe mouse auditory cortex is comprised of several auditory fields spanning the dorso-ventral axis of the temporal lobe. The ventral most auditory field is the temporal association cortex (TeA), which remains largely unstudied. Using Neuropixels probes, we simultaneously recorded from primary auditory cortex (AUDp), secondary auditory cortex (AUDv) and TeA, characterizing neuronal responses to pure tones and frequency modulated (FM) sweeps in awake head-restrained mice. As compared to primary and secondary auditory cortices, single unit responses to pure tones in TeA were sparser, delayed and prolonged. Responses to FMs were also sparser. Population analysis showed that the sparser responses in TeA render it less sensitive to pure tones, yet more sensitive to FMs. When characterizing responses to pure tones under anesthesia, the distinct signature of TeA was changed considerably as compared to that in awake mice, implying that responses in TeA are strongly modulated by non-feedforward connections. Together with the known connectivity profile of TeA, these findings suggest that sparse representation of sounds in TeA supports selectivity to higher-order features of sounds and more complex auditory computations.

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Auditory-Somatosensory Multisensory Processing in Auditory Association Cortex: An fMRI Study

Journal of Neurophysiology ◽

10.1152/jn.2002.88.1.540 ◽

2002 ◽

Vol 88 (1) ◽

pp. 540-543 ◽

Cited By ~ 244

Author(s):

John J. Foxe ◽

Glenn R. Wylie ◽

Antigona Martinez ◽

Charles E. Schroeder ◽

Daniel C. Javitt ◽

...

Keyword(s):

Auditory Cortex ◽

Multisensory Integration ◽

Multisensory Processing ◽

Primary Auditory Cortex ◽

Superior Temporal Gyrus ◽

Brain Regions ◽

Association Cortex ◽

Convergence Region ◽

Auditory Cortices ◽

Auditory Association Cortex

Using high-field (3 Tesla) functional magnetic resonance imaging (fMRI), we demonstrate that auditory and somatosensory inputs converge in a subregion of human auditory cortex along the superior temporal gyrus. Further, simultaneous stimulation in both sensory modalities resulted in activity exceeding that predicted by summing the responses to the unisensory inputs, thereby showing multisensory integration in this convergence region. Recently, intracranial recordings in macaque monkeys have shown similar auditory-somatosensory convergence in a subregion of auditory cortex directly caudomedial to primary auditory cortex (area CM). The multisensory region identified in the present investigation may be the human homologue of CM. Our finding of auditory-somatosensory convergence in early auditory cortices contributes to mounting evidence for multisensory integration early in the cortical processing hierarchy, in brain regions that were previously assumed to be unisensory.

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Heterogeneous Neuronal Responses to Frequency-Modulated Tones in the Primary Auditory Cortex of Awake Cats

Journal of Neurophysiology ◽

10.1152/jn.90364.2008 ◽

2008 ◽

Vol 100 (3) ◽

pp. 1622-1634 ◽

Cited By ~ 17

Author(s):

Ling Qin ◽

JingYu Wang ◽

Yu Sato

Keyword(s):

Receptive Field ◽

Auditory Cortex ◽

Response Pattern ◽

Primary Auditory Cortex ◽

Neuronal Responses ◽

Discrete Response ◽

A Cell ◽

Pure Tones ◽

Awake Cats ◽

Sweep Speed

Previous studies in anesthetized animals reported that the primary auditory cortex (A1) showed homogenous phasic responses to FM tones, namely a transient response to a particular instantaneous frequency when FM sweeps traversed a neuron's tone-evoked receptive field (TRF). Here, in awake cats, we report that A1 cells exhibit heterogeneous FM responses, consisting of three patterns. The first is continuous firing when a slow FM sweep traverses the receptive field of a cell with a sustained tonal response. The duration and amplitude of FM response decrease with increasing sweep speed. The second pattern is transient firing corresponding to the cell's phasic tonal response. This response could be evoked only by a fast FM sweep through the cell's TRF, suggesting a preference for fast FM. The third pattern was associated with the off response to pure tones and was composed of several discrete response peaks during slow FM stimulus. These peaks were not predictable from the cell's tonal response but reliably reflected the time when FM swept across specific frequencies. Our A1 samples often exhibited a complex response pattern, combining two or three of the basic patterns above, resulting in a heterogeneous response population. The diversity of FM responses suggests that A1 use multiple mechanisms to fully represent the whole range of FM parameters, including frequency extent, sweep speed, and direction.

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Functional Organization of Squirrel Monkey Primary Auditory Cortex: Responses to Pure Tones

Journal of Neurophysiology ◽

10.1152/jn.2001.85.4.1732 ◽

2001 ◽

Vol 85 (4) ◽

pp. 1732-1749 ◽

Cited By ~ 75

Author(s):

Steven W. Cheung ◽

Purvis H. Bedenbaugh ◽

Srikantan S. Nagarajan ◽

Christoph E. Schreiner

Keyword(s):

Receptive Field ◽

Auditory Cortex ◽

Squirrel Monkey ◽

Spatial Organization ◽

Functional Organization ◽

Primary Auditory Cortex ◽

Complex Sound ◽

Sound Coding ◽

Field Gradients ◽

Pure Tones

The spatial organization of response parameters in squirrel monkey primary auditory cortex (AI) accessible on the temporal gyrus was determined with the excitatory receptive field to pure tone stimuli. Dense, microelectrode mapping of the temporal gyrus in four animals revealed that characteristic frequency (CF) had a smooth, monotonic gradient that systematically changed from lower values (0.5 kHz) in the caudoventral quadrant to higher values (5–6 kHz) in the rostrodorsal quadrant. The extent of AI on the temporal gyrus was ∼4 mm in the rostrocaudal axis and 2–3 mm in the dorsoventral axis. The entire length of isofrequency contours below 6 kHz was accessible for study. Several independent, spatially organized functional response parameters were demonstrated for the squirrel monkey AI. Latency, the asymptotic minimum arrival time for spikes with increasing sound pressure levels at CF, was topographically organized as a monotonic gradient across AI nearly orthogonal to the CF gradient. Rostral AI had longer latencies (range = 4 ms). Threshold and bandwidth co-varied with the CF. Factoring out the contribution of the CF on threshold variance, residual threshold showed a monotonic gradient across AI that had higher values (range = 10 dB) caudally. The orientation of the threshold gradient was significantly different from the CF gradient. CF-corrected bandwidth, residual Q10, was spatially organized in local patches of coherent values whose loci were specific for each monkey. These data support the existence of multiple, overlying receptive field gradients within AI and form the basis to develop a conceptual framework to understand simple and complex sound coding in mammals.

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Dissociable influences of primary auditory cortex and the posterior auditory field on neuronal responses in the dorsal zone of auditory cortex

Journal of Neurophysiology ◽

10.1152/jn.00682.2014 ◽

2015 ◽

Vol 113 (2) ◽

pp. 475-486

Author(s):

Melanie A. Kok ◽

Daniel Stolzberg ◽

Trecia A. Brown ◽

Stephen G. Lomber

Keyword(s):

Auditory Cortex ◽

Receptive Fields ◽

Primary Auditory Cortex ◽

Population Level ◽

Noise Burst ◽

Hierarchical Organization ◽

Neuronal Responses ◽

Tone Frequency ◽

Hierarchical Processing ◽

Auditory Field

Current models of hierarchical processing in auditory cortex have been based principally on anatomical connectivity while functional interactions between individual regions have remained largely unexplored. Previous cortical deactivation studies in the cat have addressed functional reciprocal connectivity between primary auditory cortex (A1) and other hierarchically lower level fields. The present study sought to assess the functional contribution of inputs along multiple stages of the current hierarchical model to a higher order area, the dorsal zone (DZ) of auditory cortex, in the anaesthetized cat. Cryoloops were placed over A1 and posterior auditory field (PAF). Multiunit neuronal responses to noise burst and tonal stimuli were recorded in DZ during cortical deactivation of each field individually and in concert. Deactivation of A1 suppressed peak neuronal responses in DZ regardless of stimulus and resulted in increased minimum thresholds and reduced absolute bandwidths for tone frequency receptive fields in DZ. PAF deactivation had less robust effects on DZ firing rates and receptive fields compared with A1 deactivation, and combined A1/PAF cooling was largely driven by the effects of A1 deactivation at the population level. These results provide physiological support for the current anatomically based model of both serial and parallel processing schemes in auditory cortical hierarchical organization.

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A weighted graph of the projections to mouse auditory cortex

10.1101/228726 ◽

2017 ◽

Author(s):

Nuno Macarico da Costa ◽

Kevan A.C. Martin ◽

Franziska D. Sägesser

Keyword(s):

Auditory Cortex ◽

Primary Auditory Cortex ◽

Weighted Graph ◽

Hierarchical Level ◽

Temporal Association ◽

Cortical Areas ◽

Deep Layers ◽

Medial Geniculate ◽

Subcortical Regions ◽

Auditory Cortices

AbstractThe projections to individual cortical areas from extrinsic sources are a major determinant of the area’s function, but we lack comprehensive quantitative input maps even for primary sensory areas in most model species. To quantify all input sources to the mouse primary auditory cortex (Au1), we made localized injections of modified rabies virus (SADΔG-mCherry) into Au1 of five C57BL/6 mice and identified all the cortical and subcortical areas containing retrogradely labeled cells. Of all neurons projecting to Au1 from extrinsic areas, 27 % were located in the ipsilateral cortex, 14 % in the contralateral cortex, and 58 % in subcortical regions (almost exclusively ipsilateral, predominantly in the medial geniculate nucleus). Although 90 % of the labeled cells in the ipsilateral cortex were located within 1 mm of Au1, most cortical areas projected to Au1, including visual, somatosensory, motor, rhinal, cingulate and piriform cortices. The hierarchical relations of the cortical areas projecting to Au1 were determined based on the proportion of cell bodies in superficial versus deep layers. Feedback projections (from deep layers 5/6) dominated, but temporal association and auditory cortices were on the same hierarchical level, providing input from both superficial and deep layers. Au1 is embedded in a densely connected network that involves a high degree of cross-modal integration.

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Reciprocal connectivity between secondary auditory cortical field and amygdala in mice

Scientific Reports ◽

10.1038/s41598-019-56092-9 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 4

Author(s):

Hiroaki Tsukano ◽

Xubin Hou ◽

Masao Horie ◽

Hiroki Kitaura ◽

Nana Nishio ◽

...

Keyword(s):

Auditory Cortex ◽

Primary Auditory Cortex ◽

The Other ◽

Axon Terminals ◽

Reciprocal Connections ◽

Cholera Toxin Subunit B ◽

Auditory Field ◽

Subunit B ◽

Cortical Field ◽

Feedback Pathway

AbstractRecent studies have examined the feedback pathway from the amygdala to the auditory cortex in conjunction with the feedforward pathway from the auditory cortex to the amygdala. However, these connections have not been fully characterized. Here, to visualize the comprehensive connectivity between the auditory cortex and amygdala, we injected cholera toxin subunit b (CTB), a bidirectional tracer, into multiple subfields in the mouse auditory cortex after identifying the location of these subfields using flavoprotein fluorescence imaging. After injecting CTB into the secondary auditory field (A2), we found densely innervated CTB-positive axon terminals that were mainly located in the lateral amygdala (La), and slight innervations in other divisions such as the basal amygdala. Moreover, we found a large number of retrogradely-stained CTB-positive neurons in La after injecting CTB into A2. When injecting CTB into the primary auditory cortex (A1), a small number of CTB-positive neurons and axons were visualized in the amygdala. Finally, we found a near complete absence of connections between the other auditory cortical fields and the amygdala. These data suggest that reciprocal connections between A2 and La are main conduits for communication between the auditory cortex and amygdala in mice.

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