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Using both sides of your brain: the case for rapid interhemispheric switching.

Schmidt MF - PLoS Biol. (2008)

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Institute for Neurological Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America. marcschm@sas.upenn.edu

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The vertebrate brain is symmetrically organized, with two identical-looking cerebral hemispheres and a brainstem that contains identically named nuclei on both sides of the midline... Figure 2 is a schematic of the main descending motor pathway showing the connection between the forebrain nuclei HVC (used as a proper name) and RA (robust nucleus of the arcopallium) and the two major projections of RA to the brainstem... Because the brainstem VRN provides, via its bilateral projections back up to HVC (Figure 2), the major way in which forebrain song nuclei are functionally connected, it is well positioned to serve a key function in synchronizing song-related motor activity in each hemisphere... In zebra finches, whose song is made up of a stereotyped sequence of syllables (known as a motif) that is repeated multiple times, this interruption is observed as a truncation of the ongoing syllable (with a delay of approximately 70 ms) followed either by the termination of the song or the start of a new motif... Using this technique, Wang and colleagues implanted electrodes in HVC of each hemisphere and found that stimulating HVC in one hemisphere caused song disruptions only when these short stimuli were delivered during certain portions of the motif... When the authors increased the amount of current, this effect disappeared and stimuli were effective at perturbing song temporal structure throughout the whole motif, suggesting that the threshold for perturbing syllable sequencing within a motif is what switches rapidly between hemispheres... The change in perturbation threshold in a given hemisphere does not necessarily imply that the “nondominant” hemisphere is inactive... Given the evidence for alternation between the left and right half of the syrinx, a critical question is whether the timing of hemispheric switching is synchronized to the switching observed in the syrinx... The authors did not directly measure syringeal dynamics, but they did compare switching patterns with the major acoustic transitions in the song... They did not find any obvious relationship between hemispheric switching and transitions in the song (e.g., syllable onset or offset) or acoustic feature transitions (e.g., pitch or amplitude)... This is plausible in the song system given known projections from the brainstem back up to the forebrain via the intermediary of the thalamus, and the direct influence that these brainstem areas have on neural activity in forebrain song control nuclei... For song production, the brainstem VRN is well placed to play a central role in hemispheric switching, but it is unlikely that it acts as a simple oscillating circuit, given that Wang and colleagues never observed any periodicity in the pattern of hemispheric switching... More generally, the purpose of interhemispheric switching may become clearer as more data are collected through the paradigm developed by the Wang lab, and similar experiments are performed in other motor systems... Functional specialization is found throughout the nervous system but requires communication among many different areas of the brain to result in cohesive activity.

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Songbirds Can Switch Rapidly between Sides When They SingMany songbirds will use both their left and right syrinx to produce song. In some cases, as illustrated here by the brown-headed cowbird, they can switch rapidly from producing sound in the left syrinx to producing sound in the right syrinx. In this example, a cluster of five short song elements is produced within a very short period of about 200 ms. The contribution of each syringeal side can be measured by implanting a small heated microbead thermistor in each primary bronchus. These measure the rate of airflow through each side of the syrinx. The bottom portion of the figure shows the airflow through each bronchus with airflow from the right side in blue and left side in red. Note that left airflow has been flipped upside down to better compare with the right side. From these measurements, one can infer the syringeal source of each song element. As shown in the sonogram, cowbirds rapidly alternate between producing a note with the left (red) and the right (blue) sides of the syrinx.(Based on recordings performed in the cowbird by Rod Suthers)
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pbio-0060269-g001: Songbirds Can Switch Rapidly between Sides When They SingMany songbirds will use both their left and right syrinx to produce song. In some cases, as illustrated here by the brown-headed cowbird, they can switch rapidly from producing sound in the left syrinx to producing sound in the right syrinx. In this example, a cluster of five short song elements is produced within a very short period of about 200 ms. The contribution of each syringeal side can be measured by implanting a small heated microbead thermistor in each primary bronchus. These measure the rate of airflow through each side of the syrinx. The bottom portion of the figure shows the airflow through each bronchus with airflow from the right side in blue and left side in red. Note that left airflow has been flipped upside down to better compare with the right side. From these measurements, one can infer the syringeal source of each song element. As shown in the sonogram, cowbirds rapidly alternate between producing a note with the left (red) and the right (blue) sides of the syrinx.(Based on recordings performed in the cowbird by Rod Suthers)

Mentions: Song production in passerine birds is one of the most striking and best characterized asymmetric behaviors at the peripheral level [20]. Each bird has a bipartite vocal organ, known as a syrinx, that is divided into left and right halves that each contain an independent membranous sound source [21]. The vocal output that one hears from a bird's beak is therefore the sum of the sounds generated from each “sound box.” In the majority of species studied, individual song syllables can be produced using a variety of different strategies. In some cases, sound can be generated in both syringeal halves at the same time, while in other cases, sound can be produced in one side at a time with air flow actively blocked in the non–sound producing syringeal half [22]. The strategies used to produce a given syllable can vary even within the same song, and there are many cases where alternations between sides can occur multiple times during the production of a single syllable (Figure 1). Switching between sides is so perfectly synchronized that the acoustic output is completely smooth across these transitions. It has been suggested that the ability of birds to use each syringeal half as a separately controlled “sound box” might be a strategy to increase the complexity of their songs [23].


Using both sides of your brain: the case for rapid interhemispheric switching.

Schmidt MF - PLoS Biol. (2008)

Songbirds Can Switch Rapidly between Sides When They SingMany songbirds will use both their left and right syrinx to produce song. In some cases, as illustrated here by the brown-headed cowbird, they can switch rapidly from producing sound in the left syrinx to producing sound in the right syrinx. In this example, a cluster of five short song elements is produced within a very short period of about 200 ms. The contribution of each syringeal side can be measured by implanting a small heated microbead thermistor in each primary bronchus. These measure the rate of airflow through each side of the syrinx. The bottom portion of the figure shows the airflow through each bronchus with airflow from the right side in blue and left side in red. Note that left airflow has been flipped upside down to better compare with the right side. From these measurements, one can infer the syringeal source of each song element. As shown in the sonogram, cowbirds rapidly alternate between producing a note with the left (red) and the right (blue) sides of the syrinx.(Based on recordings performed in the cowbird by Rod Suthers)
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2573940&req=5

pbio-0060269-g001: Songbirds Can Switch Rapidly between Sides When They SingMany songbirds will use both their left and right syrinx to produce song. In some cases, as illustrated here by the brown-headed cowbird, they can switch rapidly from producing sound in the left syrinx to producing sound in the right syrinx. In this example, a cluster of five short song elements is produced within a very short period of about 200 ms. The contribution of each syringeal side can be measured by implanting a small heated microbead thermistor in each primary bronchus. These measure the rate of airflow through each side of the syrinx. The bottom portion of the figure shows the airflow through each bronchus with airflow from the right side in blue and left side in red. Note that left airflow has been flipped upside down to better compare with the right side. From these measurements, one can infer the syringeal source of each song element. As shown in the sonogram, cowbirds rapidly alternate between producing a note with the left (red) and the right (blue) sides of the syrinx.(Based on recordings performed in the cowbird by Rod Suthers)
Mentions: Song production in passerine birds is one of the most striking and best characterized asymmetric behaviors at the peripheral level [20]. Each bird has a bipartite vocal organ, known as a syrinx, that is divided into left and right halves that each contain an independent membranous sound source [21]. The vocal output that one hears from a bird's beak is therefore the sum of the sounds generated from each “sound box.” In the majority of species studied, individual song syllables can be produced using a variety of different strategies. In some cases, sound can be generated in both syringeal halves at the same time, while in other cases, sound can be produced in one side at a time with air flow actively blocked in the non–sound producing syringeal half [22]. The strategies used to produce a given syllable can vary even within the same song, and there are many cases where alternations between sides can occur multiple times during the production of a single syllable (Figure 1). Switching between sides is so perfectly synchronized that the acoustic output is completely smooth across these transitions. It has been suggested that the ability of birds to use each syringeal half as a separately controlled “sound box” might be a strategy to increase the complexity of their songs [23].

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Institute for Neurological Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America. marcschm@sas.upenn.edu

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

The vertebrate brain is symmetrically organized, with two identical-looking cerebral hemispheres and a brainstem that contains identically named nuclei on both sides of the midline... Figure 2 is a schematic of the main descending motor pathway showing the connection between the forebrain nuclei HVC (used as a proper name) and RA (robust nucleus of the arcopallium) and the two major projections of RA to the brainstem... Because the brainstem VRN provides, via its bilateral projections back up to HVC (Figure 2), the major way in which forebrain song nuclei are functionally connected, it is well positioned to serve a key function in synchronizing song-related motor activity in each hemisphere... In zebra finches, whose song is made up of a stereotyped sequence of syllables (known as a motif) that is repeated multiple times, this interruption is observed as a truncation of the ongoing syllable (with a delay of approximately 70 ms) followed either by the termination of the song or the start of a new motif... Using this technique, Wang and colleagues implanted electrodes in HVC of each hemisphere and found that stimulating HVC in one hemisphere caused song disruptions only when these short stimuli were delivered during certain portions of the motif... When the authors increased the amount of current, this effect disappeared and stimuli were effective at perturbing song temporal structure throughout the whole motif, suggesting that the threshold for perturbing syllable sequencing within a motif is what switches rapidly between hemispheres... The change in perturbation threshold in a given hemisphere does not necessarily imply that the “nondominant” hemisphere is inactive... Given the evidence for alternation between the left and right half of the syrinx, a critical question is whether the timing of hemispheric switching is synchronized to the switching observed in the syrinx... The authors did not directly measure syringeal dynamics, but they did compare switching patterns with the major acoustic transitions in the song... They did not find any obvious relationship between hemispheric switching and transitions in the song (e.g., syllable onset or offset) or acoustic feature transitions (e.g., pitch or amplitude)... This is plausible in the song system given known projections from the brainstem back up to the forebrain via the intermediary of the thalamus, and the direct influence that these brainstem areas have on neural activity in forebrain song control nuclei... For song production, the brainstem VRN is well placed to play a central role in hemispheric switching, but it is unlikely that it acts as a simple oscillating circuit, given that Wang and colleagues never observed any periodicity in the pattern of hemispheric switching... More generally, the purpose of interhemispheric switching may become clearer as more data are collected through the paradigm developed by the Wang lab, and similar experiments are performed in other motor systems... Functional specialization is found throughout the nervous system but requires communication among many different areas of the brain to result in cohesive activity.

Show MeSH
Related in: MedlinePlus