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Neural mechanisms of auditory categorization: from across brain areas to within local microcircuits.

Tsunada J, Cohen YE - Front Neurosci (2014)

Bottom Line: We propose different neural transformations across different scales of neural organization in auditory categorization.Along the ascending auditory system in the ventral pathway, there is a progression in the encoding of categories from simple acoustic categories to categories for abstract information.On the other hand, in local microcircuits, different classes of neurons differentially compute categorical information.

View Article: PubMed Central - PubMed

Affiliation: Department of Otorhinolaryngology-Head and Neck Surgery, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA, USA.

ABSTRACT
Categorization enables listeners to efficiently encode and respond to auditory stimuli. Behavioral evidence for auditory categorization has been well documented across a broad range of human and non-human animal species. Moreover, neural correlates of auditory categorization have been documented in a variety of different brain regions in the ventral auditory pathway, which is thought to underlie auditory-object processing and auditory perception. Here, we review and discuss how neural representations of auditory categories are transformed across different scales of neural organization in the ventral auditory pathway: from across different brain areas to within local microcircuits. We propose different neural transformations across different scales of neural organization in auditory categorization. Along the ascending auditory system in the ventral pathway, there is a progression in the encoding of categories from simple acoustic categories to categories for abstract information. On the other hand, in local microcircuits, different classes of neurons differentially compute categorical information.

No MeSH data available.


Related in: MedlinePlus

Categorical neural activity in the monkey lateral belt during categorization of speech sounds. (A) An example of the activity of a lateral belt neuron. The speech sounds were two human-speech sounds (“bad” and “dad”) and their morphs. Neural activity is color-coded by morphing percentage of the stimulus as shown in the legend. The raster plots and histograms are aligned relative to onset of the stimulus. (B) Temporal dynamics of the category index at the population level. Category-index values >0 indicate that neurons categorically represent speech sounds (Freedman et al., 2001; Tsunada et al., 2011). The thick line represents the mean value and the shaded area represents the bootstrapped 95%-confidence intervals of the mean. The two vertical lines indicate stimulus onset and offset, respectively, whereas the horizontal line indicates a category-index value of 0. The figure is adopted, with permission, from Tsunada et al. (2011).
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Figure 2: Categorical neural activity in the monkey lateral belt during categorization of speech sounds. (A) An example of the activity of a lateral belt neuron. The speech sounds were two human-speech sounds (“bad” and “dad”) and their morphs. Neural activity is color-coded by morphing percentage of the stimulus as shown in the legend. The raster plots and histograms are aligned relative to onset of the stimulus. (B) Temporal dynamics of the category index at the population level. Category-index values >0 indicate that neurons categorically represent speech sounds (Freedman et al., 2001; Tsunada et al., 2011). The thick line represents the mean value and the shaded area represents the bootstrapped 95%-confidence intervals of the mean. The two vertical lines indicate stimulus onset and offset, respectively, whereas the horizontal line indicates a category-index value of 0. The figure is adopted, with permission, from Tsunada et al. (2011).

Mentions: Categorical representations of speech sounds at the level of the single neuron or local populations of neurons appear to occur at the next stage of auditory processing in the ventral auditory pathway, the lateral-belt regions. Several recent studies have noted that neural activity in the monkey lateral-belt and human superior temporal gyrus encodes speech-sound categories (Chang et al., 2010; Steinschneider et al., 2011; Tsunada et al., 2011; Steinschneider, 2013). For example, our group found that, when monkeys categorized two prototypes of speech sounds (“bad” and “dad”) and their morphed versions, neural activity in the lateral belt discretely changed at the category boundary, suggesting that these neurons encoded the auditory category rather than smoothly varying acoustic features (Figure 2).


Neural mechanisms of auditory categorization: from across brain areas to within local microcircuits.

Tsunada J, Cohen YE - Front Neurosci (2014)

Categorical neural activity in the monkey lateral belt during categorization of speech sounds. (A) An example of the activity of a lateral belt neuron. The speech sounds were two human-speech sounds (“bad” and “dad”) and their morphs. Neural activity is color-coded by morphing percentage of the stimulus as shown in the legend. The raster plots and histograms are aligned relative to onset of the stimulus. (B) Temporal dynamics of the category index at the population level. Category-index values >0 indicate that neurons categorically represent speech sounds (Freedman et al., 2001; Tsunada et al., 2011). The thick line represents the mean value and the shaded area represents the bootstrapped 95%-confidence intervals of the mean. The two vertical lines indicate stimulus onset and offset, respectively, whereas the horizontal line indicates a category-index value of 0. The figure is adopted, with permission, from Tsunada et al. (2011).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4060728&req=5

Figure 2: Categorical neural activity in the monkey lateral belt during categorization of speech sounds. (A) An example of the activity of a lateral belt neuron. The speech sounds were two human-speech sounds (“bad” and “dad”) and their morphs. Neural activity is color-coded by morphing percentage of the stimulus as shown in the legend. The raster plots and histograms are aligned relative to onset of the stimulus. (B) Temporal dynamics of the category index at the population level. Category-index values >0 indicate that neurons categorically represent speech sounds (Freedman et al., 2001; Tsunada et al., 2011). The thick line represents the mean value and the shaded area represents the bootstrapped 95%-confidence intervals of the mean. The two vertical lines indicate stimulus onset and offset, respectively, whereas the horizontal line indicates a category-index value of 0. The figure is adopted, with permission, from Tsunada et al. (2011).
Mentions: Categorical representations of speech sounds at the level of the single neuron or local populations of neurons appear to occur at the next stage of auditory processing in the ventral auditory pathway, the lateral-belt regions. Several recent studies have noted that neural activity in the monkey lateral-belt and human superior temporal gyrus encodes speech-sound categories (Chang et al., 2010; Steinschneider et al., 2011; Tsunada et al., 2011; Steinschneider, 2013). For example, our group found that, when monkeys categorized two prototypes of speech sounds (“bad” and “dad”) and their morphed versions, neural activity in the lateral belt discretely changed at the category boundary, suggesting that these neurons encoded the auditory category rather than smoothly varying acoustic features (Figure 2).

Bottom Line: We propose different neural transformations across different scales of neural organization in auditory categorization.Along the ascending auditory system in the ventral pathway, there is a progression in the encoding of categories from simple acoustic categories to categories for abstract information.On the other hand, in local microcircuits, different classes of neurons differentially compute categorical information.

View Article: PubMed Central - PubMed

Affiliation: Department of Otorhinolaryngology-Head and Neck Surgery, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA, USA.

ABSTRACT
Categorization enables listeners to efficiently encode and respond to auditory stimuli. Behavioral evidence for auditory categorization has been well documented across a broad range of human and non-human animal species. Moreover, neural correlates of auditory categorization have been documented in a variety of different brain regions in the ventral auditory pathway, which is thought to underlie auditory-object processing and auditory perception. Here, we review and discuss how neural representations of auditory categories are transformed across different scales of neural organization in the ventral auditory pathway: from across different brain areas to within local microcircuits. We propose different neural transformations across different scales of neural organization in auditory categorization. Along the ascending auditory system in the ventral pathway, there is a progression in the encoding of categories from simple acoustic categories to categories for abstract information. On the other hand, in local microcircuits, different classes of neurons differentially compute categorical information.

No MeSH data available.


Related in: MedlinePlus