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High-Field Functional Imaging of Pitch Processing in Auditory Cortex of the Cat.

Butler BE, Hall AJ, Lomber SG - PLoS ONE (2015)

Bottom Line: Rather, cortical areas surrounding the posterior ectosylvian sulcus responded preferentially to the IRN stimulus when compared to narrowband noise, with group analyses revealing bilateral activity centred in the posterior auditory field (PAF).This study demonstrates that fMRI is useful for identifying pitch-related processing in cat cortex, and identifies cortical areas that warrant further investigation.Moreover, we have taken the first steps in identifying a useful animal model for the study of pitch perception.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada; Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada.

ABSTRACT
The perception of pitch is a widely studied and hotly debated topic in human hearing. Many of these studies combine functional imaging techniques with stimuli designed to disambiguate the percept of pitch from frequency information present in the stimulus. While useful in identifying potential "pitch centres" in cortex, the existence of truly pitch-responsive neurons requires single neuron-level measures that can only be undertaken in animal models. While a number of animals have been shown to be sensitive to pitch, few studies have addressed the location of cortical generators of pitch percepts in non-human models. The current study uses high-field functional magnetic resonance imaging (fMRI) of the feline brain in an attempt to identify regions of cortex that show increased activity in response to pitch-evoking stimuli. Cats were presented with iterated rippled noise (IRN) stimuli, narrowband noise stimuli with the same spectral profile but no perceivable pitch, and a processed IRN stimulus in which phase components were randomized to preserve slowly changing modulations in the absence of pitch (IRNo). Pitch-related activity was not observed to occur in either primary auditory cortex (A1) or the anterior auditory field (AAF) which comprise the core auditory cortex in cats. Rather, cortical areas surrounding the posterior ectosylvian sulcus responded preferentially to the IRN stimulus when compared to narrowband noise, with group analyses revealing bilateral activity centred in the posterior auditory field (PAF). This study demonstrates that fMRI is useful for identifying pitch-related processing in cat cortex, and identifies cortical areas that warrant further investigation. Moreover, we have taken the first steps in identifying a useful animal model for the study of pitch perception.

No MeSH data available.


Related in: MedlinePlus

Hemodynamic time courses for bilateral PAF activity averaged across animals.The mean percent signal change in voxels within a 1mm sphere of the peak voxels are plotted for each volume in response to IRN (red) and NBN (green) stimuli. Error bars indicate the standard error of the mean. Points where an individual time course differs significantly from zero are marked by an asterisk while points where the two time courses significantly differ from each other are indicated by shading.
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pone.0134362.g004: Hemodynamic time courses for bilateral PAF activity averaged across animals.The mean percent signal change in voxels within a 1mm sphere of the peak voxels are plotted for each volume in response to IRN (red) and NBN (green) stimuli. Error bars indicate the standard error of the mean. Points where an individual time course differs significantly from zero are marked by an asterisk while points where the two time courses significantly differ from each other are indicated by shading.

Mentions: A group-level analysis was also performed to identify the locus of pitch processing across animals. The IRN-NBN contrast revealed large, significant clusters of BOLD activity centered bilaterally over PAF (Fig 3). The extracted BOLD signal time course for a 1 mm sphere surrounding the maximally significant voxel for this contrast are presented in Fig 4 for the left (panel A) and right (panel B) hemispheres. While a majority of pitch imaging studies in humans have employed this contrast (IRN-NBN), it has been suggested that this contrast is insufficient to truly image pitch-specific regions since the process involved in generating IRN stimuli introduces modulations of signal strength that are unrelated to the pitch percept, and which are not present in filtered Gaussian noise [11]. In an attempt to further isolate pitch-related information, BOLD signal changes in response to an IRN stimulus were contrasted against the response to a no-pitch IRN stimulus (IRNo) in which phase components are randomized to remove the pitch percept, but preserve the slowly changing signal modulations. This contrast (IRN-IRNo) revealed some auditory cortex activity bilaterally, but this failed to reach significance (data not shown).


High-Field Functional Imaging of Pitch Processing in Auditory Cortex of the Cat.

Butler BE, Hall AJ, Lomber SG - PLoS ONE (2015)

Hemodynamic time courses for bilateral PAF activity averaged across animals.The mean percent signal change in voxels within a 1mm sphere of the peak voxels are plotted for each volume in response to IRN (red) and NBN (green) stimuli. Error bars indicate the standard error of the mean. Points where an individual time course differs significantly from zero are marked by an asterisk while points where the two time courses significantly differ from each other are indicated by shading.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4520558&req=5

pone.0134362.g004: Hemodynamic time courses for bilateral PAF activity averaged across animals.The mean percent signal change in voxels within a 1mm sphere of the peak voxels are plotted for each volume in response to IRN (red) and NBN (green) stimuli. Error bars indicate the standard error of the mean. Points where an individual time course differs significantly from zero are marked by an asterisk while points where the two time courses significantly differ from each other are indicated by shading.
Mentions: A group-level analysis was also performed to identify the locus of pitch processing across animals. The IRN-NBN contrast revealed large, significant clusters of BOLD activity centered bilaterally over PAF (Fig 3). The extracted BOLD signal time course for a 1 mm sphere surrounding the maximally significant voxel for this contrast are presented in Fig 4 for the left (panel A) and right (panel B) hemispheres. While a majority of pitch imaging studies in humans have employed this contrast (IRN-NBN), it has been suggested that this contrast is insufficient to truly image pitch-specific regions since the process involved in generating IRN stimuli introduces modulations of signal strength that are unrelated to the pitch percept, and which are not present in filtered Gaussian noise [11]. In an attempt to further isolate pitch-related information, BOLD signal changes in response to an IRN stimulus were contrasted against the response to a no-pitch IRN stimulus (IRNo) in which phase components are randomized to remove the pitch percept, but preserve the slowly changing signal modulations. This contrast (IRN-IRNo) revealed some auditory cortex activity bilaterally, but this failed to reach significance (data not shown).

Bottom Line: Rather, cortical areas surrounding the posterior ectosylvian sulcus responded preferentially to the IRN stimulus when compared to narrowband noise, with group analyses revealing bilateral activity centred in the posterior auditory field (PAF).This study demonstrates that fMRI is useful for identifying pitch-related processing in cat cortex, and identifies cortical areas that warrant further investigation.Moreover, we have taken the first steps in identifying a useful animal model for the study of pitch perception.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada; Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada.

ABSTRACT
The perception of pitch is a widely studied and hotly debated topic in human hearing. Many of these studies combine functional imaging techniques with stimuli designed to disambiguate the percept of pitch from frequency information present in the stimulus. While useful in identifying potential "pitch centres" in cortex, the existence of truly pitch-responsive neurons requires single neuron-level measures that can only be undertaken in animal models. While a number of animals have been shown to be sensitive to pitch, few studies have addressed the location of cortical generators of pitch percepts in non-human models. The current study uses high-field functional magnetic resonance imaging (fMRI) of the feline brain in an attempt to identify regions of cortex that show increased activity in response to pitch-evoking stimuli. Cats were presented with iterated rippled noise (IRN) stimuli, narrowband noise stimuli with the same spectral profile but no perceivable pitch, and a processed IRN stimulus in which phase components were randomized to preserve slowly changing modulations in the absence of pitch (IRNo). Pitch-related activity was not observed to occur in either primary auditory cortex (A1) or the anterior auditory field (AAF) which comprise the core auditory cortex in cats. Rather, cortical areas surrounding the posterior ectosylvian sulcus responded preferentially to the IRN stimulus when compared to narrowband noise, with group analyses revealing bilateral activity centred in the posterior auditory field (PAF). This study demonstrates that fMRI is useful for identifying pitch-related processing in cat cortex, and identifies cortical areas that warrant further investigation. Moreover, we have taken the first steps in identifying a useful animal model for the study of pitch perception.

No MeSH data available.


Related in: MedlinePlus