scholarly journals Diverse cortical codes for scene segmentation in primate auditory cortex

2015 ◽  
Vol 113 (7) ◽  
pp. 2934-2952 ◽  
Author(s):  
Brian J. Malone ◽  
Brian H. Scott ◽  
Malcolm N. Semple
Keyword(s):  
Spike Train ◽  
Cortical Neurons ◽  
Rhesus Macaques ◽  
Discrimination Performance ◽  
Duration Discrimination ◽  
Stimulus Onset ◽  
Cortical Response ◽  
Substantial Contribution ◽  
Response Patterns ◽  
Amplitude Fluctuations

The temporal coherence of amplitude fluctuations is a critical cue for segmentation of complex auditory scenes. The auditory system must accurately demarcate the onsets and offsets of acoustic signals. We explored how and how well the timing of onsets and offsets of gated tones are encoded by auditory cortical neurons in awake rhesus macaques. Temporal features of this representation were isolated by presenting otherwise identical pure tones of differing durations. Cortical response patterns were diverse, including selective encoding of onset and offset transients, tonic firing, and sustained suppression. Spike train classification methods revealed that many neurons robustly encoded tone duration despite substantial diversity in the encoding process. Excellent discrimination performance was achieved by neurons whose responses were primarily phasic at tone offset and by those that responded robustly while the tone persisted. Although diverse cortical response patterns converged on effective duration discrimination, this diversity significantly constrained the utility of decoding models referenced to a spiking pattern averaged across all responses or averaged within the same response category. Using maximum likelihood-based decoding models, we demonstrated that the spike train recorded in a single trial could support direct estimation of stimulus onset and offset. Comparisons between different decoding models established the substantial contribution of bursts of activity at sound onset and offset to demarcating the temporal boundaries of gated tones. Our results indicate that relatively few neurons suffice to provide temporally precise estimates of such auditory “edges,” particularly for models that assume and exploit the heterogeneity of neural responses in awake cortex.

Representation of Spectral and Temporal Envelope of Twitter Vocalizations in Common Marmoset Primary Auditory Cortex

2002 ◽  
Vol 87 (4) ◽  
pp. 1723-1737 ◽  
Author(s):  
Srikantan S. Nagarajan ◽  
Steven W. Cheung ◽  
Purvis Bedenbaugh ◽  
Ralph E. Beitel ◽  
Christoph E. Schreiner ◽  
...  
Keyword(s):  
Cortical Neurons ◽  
Social Contact ◽  
Primary Auditory Cortex ◽  
Common Marmoset ◽  
Spectral Envelope ◽  
Response Patterns ◽  
Temporal Envelope ◽  
Degraded Speech ◽  
Neurophysiological Data ◽  
Narrowband Channels

Cortical sensitivity in representations of behaviorally relevant complex input signals was examined in recordings from primary auditory cortical neurons (AI) in adult, barbiturate-anesthetized common marmoset monkeys ( Callithrix jacchus). We studied the robustness of distributed responses to natural and degraded forms of twitter calls, social contact vocalizations comprising several quasi-periodic phrases of frequency and AM. We recorded neuronal responses to a monkey's own twitter call (MOC), degraded forms of their twitter call, and sinusoidal amplitude modulated (SAM) tones with modulation rates similar to those of twitter calls. In spectral envelope degradation, calls with narrowband channels of varying bandwidths had the same temporal envelope as a natural call. However, the carrier phase was randomized within each narrowband channel. In temporal envelope degradation, the temporal envelope within narrowband channels was filtered while the carrier frequencies and phases remained unchanged. In a third form of degradation, noise was added to the natural calls. Spatiotemporal discharge patterns in AI both within and across frequency bands encoded spectrotemporal acoustic features in the call although the encoded response is an abstract version of the call. The average temporal response pattern in AI, however, was significantly correlated with the average temporal envelope for each phrase of a call. Response entrainment to MOC was significantly correlated with entrainment to SAM stimuli at comparable modulation frequencies. Sensitivity of the response patterns to MOC was substantially greater for temporal envelope than for spectral envelope degradations. The distributed responses in AI were robust to additive continuous noise at signal-to-noise ratios ≥10 dB. Neurophysiological data reflecting response sensitivity in AI to these forms of degradation closely parallel human psychophysical results on the intelligibility of degraded speech in quiet and noisy conditions.

scholarly journals Sound-identity processing in early areas of the auditory ventral stream in the macaque

2012 ◽  
Vol 107 (4) ◽  
pp. 1123-1141 ◽  
Author(s):  
Paweł Kuśmierek ◽  
Michael Ortiz ◽  
Josef P. Rauschecker
Keyword(s):  
Rhesus Macaques ◽  
Population Analysis ◽  
Activity Patterns ◽  
Dorsal Stream ◽  
Stimulus Onset ◽  
Ventral Stream ◽  
Underlying Mechanisms ◽  
Species Specific ◽  
Rostral Region ◽  
Identity Processing

Auditory cortical processing is thought to be accomplished along two processing streams. The existence of a posterior/dorsal stream dealing, among others, with the processing of spatial aspects of sound has been corroborated by numerous studies in several species. An anterior/ventral stream for the processing of nonspatial sound qualities, including the identification of sounds such as species-specific vocalizations, has also received much support. Originally discovered in anterolateral belt cortex, most recent work on the anterior/ventral pathway has been performed on far anterior superior temporal (ST) areas and on ventrolateral prefrontal cortex (VLPFC). Regions of the anterior/ventral stream near its origin in early auditory areas have been less explored. In the present study, we examined three early auditory regions with different anteroposterior locations (caudal, middle, and rostral) in awake rhesus macaques. We analyzed how well classification based on sound-evoked activity patterns of neuronal populations replicates the original stimulus categories. Of the three regions, the rostral region (rR), which included core area R and medial belt area RM, yielded the greatest classification success across all stimulus classes or between classes of natural sounds. Starting from ∼80 ms past stimulus onset, clustering based on the population response in rR became clearly more successful than clustering based on responses from any other region. Our study demonstrates that specialization for sound-identity processing can be found very early in the auditory ventral stream. Furthermore, the fact that this processing develops over time can shed light on underlying mechanisms. Finally, we show that population analysis is a more sensitive method for revealing functional specialization than conventional types of analysis.

Developmental Patterns of Duration Discrimination

1993 ◽  
Vol 36 (4) ◽  
pp. 842-849 ◽  
Author(s):  
Jill L. Elfenbein ◽  
Arnold M. Small ◽  
Julia M. Davis
Keyword(s):  
Standard Stimulus ◽  
Discrimination Performance ◽  
Noise Burst ◽  
Duration Discrimination ◽  
Broadband Noise ◽  
Developmental Patterns ◽  
Age Related ◽  
Perceptual Abilities

The purpose of this study was to determine whether the auditory perceptual abilities of children are characterized by an age-related improvement in duration discrimination. Forty children, ages 4 to 10 years, and 10 adults served as subjects. Difference limens were obtained using a 350-msec broadband noise burst as the standard stimulus in a three-interval forcedchoice paradigm. Data were characterized by significant differences between the performances of the 4-, 6-, and 8-year-olds and those of the adults. Acquisition of adult-like discrimination performance was demonstrated between the ages of 8 and 10 years.

Temporal Dynamics of Shape Analysis in Macaque Visual Area V2

2004 ◽  
Vol 92 (5) ◽  
pp. 3030-3042 ◽  
Author(s):  
Jay Hegdé ◽  
David C. Van Essen
Keyword(s):  
Cortical Neurons ◽  
Time Course ◽  
Temporal Dynamics ◽  
Visual Stimulation ◽  
Signal To Noise Ratio ◽  
Stimulus Onset ◽  
Visual Area ◽  
Response Modulation ◽  
Population Response ◽  
Area V2

The firing rate of visual cortical neurons typically changes substantially during a sustained visual stimulus. To assess whether, and to what extent, the information about shape conveyed by neurons in visual area V2 changes over the course of the response, we recorded the responses of V2 neurons in awake, fixating monkeys while presenting a diverse set of static shape stimuli within the classical receptive field. We analyzed the time course of various measures of responsiveness and stimulus-related response modulation at the level of individual cells and of the population. For a majority of V2 cells, the response modulation was maximal during the initial transient response (40–80 ms after stimulus onset). During the same period, the population response was relatively correlated, in that V2 cells tended to respond similarly to specific subsets of stimuli. Over the ensuing 80–100 ms, the signal-to-noise ratio of individual cells generally declined, but to a lesser degree than the evoked-response rate during the corresponding time bins, and the response profiles became decorrelated for many individual cells. Concomitantly, the population response became substantially decorrelated. Our results indicate that the information about stimulus shape evolves dynamically and relatively rapidly in V2 during static visual stimulation in ways that may contribute to form discrimination.

Auditory Cortical Response Patterns to Multiple Rhythms of AM Sound

2002 ◽  
Vol 23 (3) ◽  
pp. 254-265 ◽  
Author(s):  
Rossitza Draganova ◽  
Bernhard Ross ◽  
Christian Borgmann ◽  
Christo Pantev
Keyword(s):  
Cortical Response ◽  
Response Patterns

Taste responses of cortical neurons in freely ingesting rats

1989 ◽  
Vol 61 (6) ◽  
pp. 1244-1258 ◽  
Author(s):  
T. Yamamoto ◽  
R. Matsuo ◽  
Y. Kiyomitsu ◽  
R. Kitamura
Keyword(s):  
Cortical Neurons ◽  
Correlation Coefficients ◽  
Entropy Measure ◽  
Response Patterns ◽  
Gustatory System ◽  
Basic Taste ◽  
Quinine Hydrochloride ◽  
Excitatory Responses

1. Activities of 35 taste-responsive neurons in the cortical gustatory area were recorded with chronically implanted fine wires in freely ingesting Wistar rats. Quantitative analyses were performed on responses to distilled water, food solution, and four taste stimuli: sucrose, NaCl, HCl, and quinine hydrochloride. 2. Taste-responsive neurons were classified into type-1 and type-2 groups according to the response patterns to licking of the six taste stimuli. Type-1 neurons (n = 29) responded in excitatory or inhibitory directions to one or more of the taste stimuli. Type-2 neurons (n = 6) showed responses in different directions depending upon palatability of the liquids to rats: neurons showing excitatory (or inhibitory) responses to palatable stimuli exhibited inhibitory (or excitatory) responses to unpalatable stimuli. 3. Correlation coefficients of responses to pairs of stimuli across neurons suggested that palatable stimuli (water, food solution, sucrose, and NaCl) and unpalatable stimuli (HCl and quinine) elicited reciprocal (excitatory vs. inhibitory) responses in type-2 neurons, whereas type-1 neurons showed positively correlated responses to specific combinations of stimuli such as food solution and NaCl, sucrose and HCl, NaCl and quinine, and HCl and quinine. 4. A tendency toward equalization of effectiveness in eliciting responses among the four basic taste stimuli was detected on the cortex. The ratios of mean evoked responses in 29 type-1 neurons in comparison with spontaneous rate (4.4 spikes/s) were 1.7, 1.9, 1.8, and 1.9 for sucrose, NaCl, HCl, and quinine, respectively. 5. The breadth of responsiveness to the four basic taste stimuli was quantified by means of the entropy measure introduced by Smith and Travers (33). The mean entropy value was 0.540 for 29 type-1 neurons, which was similar to 0.588 previously reported for rat chorda tympani fibers, suggesting that breadth of tuning is not more narrowly tuned in a higher level of the gustatory system in the rat. 6. Convergent inputs of other sensory modalities were detected exclusively in type-1 neurons. Thirteen (45%) of 29 type-1 neurons also responded to cold and/or warm water, but none of 6 type-2 neurons responded to thermal stimuli. Two (7%) of 29 type-1 neurons responded to almond and acetic acid odors, but the 6 type-2 neurons did not. Two (13%) of 16 type-1 neurons responded to interperitoneal injection of LiCl, which is known to induce gastrointestinal disorders, with a latency of approximately 5 min, but 4 type-2 neurons tested were not responsive to this stimulation.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Emergence of an invariant representation of texture in primate somatosensory cortex

2019 ◽  
Author(s):  
Justin D. Lieber ◽  
Sliman J. Bensmaia
Keyword(s):  
Cortical Neurons ◽  
Rhesus Macaques ◽  
Scanning Speed ◽  
Nerve Fibers ◽  
Invariant Representation ◽  
Major Function ◽  
Neural Representations ◽  
Wide Range ◽  
Sensory Modalities ◽  
Exploratory Movements

ABSTRACTA major function of sensory processing is to achieve neural representations of objects that are stable across changes in context and perspective. Small changes in exploratory behavior can lead to large changes in signals at the sensory periphery, thus resulting in ambiguous neural representations of objects. Overcoming this ambiguity is a hallmark of human object recognition across sensory modalities. Here, we investigate how the perception of tactile texture remains stable across exploratory movements of the hand, including changes in scanning speed, despite the concomitant changes in afferent responses. To this end, we scanned a wide range of everyday textures across the fingertips of Rhesus macaques at multiple speeds and recorded the responses evoked in tactile nerve fibers and somatosensory cortical neurons. We found that individual cortical neurons exhibit a wider range of speed-sensitivities than do nerve fibers. The resulting representations of speed and texture in cortex are more independent than are their counterparts in the nerve and account for speed-invariant perception of texture. We demonstrate that this separation of speed and texture information is a natural consequence of previously described cortical computations.

scholarly journals The timing and magnitude of Stroop interference and facilitation in monolinguals and bilinguals

2012 ◽  
Vol 16 (2) ◽  
pp. 420-441 ◽  
Author(s):  
EMILY L. CODERRE ◽  
WALTER J. B. VAN HEUVEN ◽  
KATHY CONKLIN
Keyword(s):  
Lexical Access ◽  
Executive Control ◽  
Critical Factor ◽  
Stimulus Onset ◽  
Stroop Interference ◽  
Language Immersion ◽  
Response Patterns ◽  
Native Languages ◽  
Factors Affecting ◽  
Different Response

Executive control abilities and lexical access speed in Stroop performance were investigated in English monolinguals and two groups of bilinguals (English–Chinese and Chinese–English) in their first (L1) and second (L2) languages. Predictions were based on a bilingual cognitive advantage hypothesis, implicating cognitive control ability as the critical factor determining Stroop interference; and two bilingual lexical disadvantage hypotheses, focusing on lexical access speed. Importantly, each hypothesis predicts different response patterns in a Stroop task manipulating stimulus onset asynchrony (SOA). There was evidence for a bilingual cognitive advantage, although this effect was sensitive to a number of variables including proficiency, language immersion, and script. In lexical access speed, no differences occurred between monolinguals and bilinguals in their native languages, but there was evidence for a delay in L2 processing speed relative to the L1. Overall, the data highlight the multitude of factors affecting executive control and lexical access speed in bilinguals.

A sustained input to the direction-selective mechanism in cat striate cortex neurons

1994 ◽  
Vol 11 (6) ◽  
pp. 1083-1092 ◽  
Author(s):  
Curtis L. Baker ◽  
Max S. Cynader
Keyword(s):  
Cortical Neurons ◽  
Striate Cortex ◽  
Stimulus Onset ◽  
Direction Selectivity ◽  
Transient Nature ◽  
Front End ◽  
Prolonged Duration ◽  
Onset Asynchrony ◽  
Cat Striate Cortex ◽  
Selective Mechanism

AbstractDirection-selective neurons in cat striate cortex were tested with bar-shaped stimuli, sequentially flashed at spatially displaced positions chosen to elicit maximal direction selectivity. Temporally overlapping flash exposures of prolonged duration (400–1000 ms) were employed at a series of onset asynchronies to explore the nature of temporal tuning of the direction-selective mechanism. In most neurons studied, direction selectivity was found to be supported by a surprisingly broad range of stimulus onset asynchronies, which was greater for longer exposure durations. These findings imply the existence of a sustained input to the direction-selective mechanism, in spite of the relatively transient nature of most cortical neurons' step responses. A model is described to illustrate how different front-end temporal filters can affect the dependence of two-flash direction selectivity on stimulus onset asynchrony. The versions of the model which successfully predict the form of the observed responses are those which combine inputs from sustained and transient filters.

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