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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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Bilateral Organization of the Song Motor Control SystemThis schematic is a simplified representation of the motor portion of the avian song system emphasizing its bilateral organization. Sound is produced in a bipartite vocal organ known as the syrinx. The syringeal muscles that make up each half of the vocal organ are innervated by motoneurons in the ipsilateral nXIIts. This nucleus receives its own motor commands from HVC and RA in the ipsilateral forebrain. Therefore, motor commands generated in the left hemisphere (highlighted in red) end up activating muscles on the left half of the syrinx, while those on the right side (highlighted in blue) activate syringeal muscles on the right side. Motor commands from each hemisphere are also sent to brainstem nuclei that form part of the bilaterally organized vocal-respiratory network (VRN), which is highly interconnected across the midline. The VRN sends motor commands to the muscles of respiration. This network also sends major projections back to the forebrain nucleus HVC via the intermediary of the thalamic relay nucleus uvaeformis (Uva). These bottom-up projections are thought to synchronize activity in both hemispheres and might play a role in the rapid hemispheric switching described by Wang et al.
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pbio-0060269-g002: Bilateral Organization of the Song Motor Control SystemThis schematic is a simplified representation of the motor portion of the avian song system emphasizing its bilateral organization. Sound is produced in a bipartite vocal organ known as the syrinx. The syringeal muscles that make up each half of the vocal organ are innervated by motoneurons in the ipsilateral nXIIts. This nucleus receives its own motor commands from HVC and RA in the ipsilateral forebrain. Therefore, motor commands generated in the left hemisphere (highlighted in red) end up activating muscles on the left half of the syrinx, while those on the right side (highlighted in blue) activate syringeal muscles on the right side. Motor commands from each hemisphere are also sent to brainstem nuclei that form part of the bilaterally organized vocal-respiratory network (VRN), which is highly interconnected across the midline. The VRN sends motor commands to the muscles of respiration. This network also sends major projections back to the forebrain nucleus HVC via the intermediary of the thalamic relay nucleus uvaeformis (Uva). These bottom-up projections are thought to synchronize activity in both hemispheres and might play a role in the rapid hemispheric switching described by Wang et al.

Mentions: In songbirds, each hemisphere contains a discrete set of brain structures that control song production in adult birds [24]. 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. One of these projections goes directly to the ipsilateral brainstem's hypoglossal nucleus (nXIIts, the tracheosyringeal part of the hypoglossal nucleus), a motor output structure that exclusively innervates the ipsilateral syringeal muscles. The other major projection from RA innervates a series of highly interconnected vocal-respiratory nuclei in the ipsilateral brainstem, several of which send projections to respiratory motoneurons in the spinal cord. These nuclei are highly interconnected across the midline and can therefore be thought of as a bilaterally organized vocal-respiratory network (VRN).


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

Schmidt MF - PLoS Biol. (2008)

Bilateral Organization of the Song Motor Control SystemThis schematic is a simplified representation of the motor portion of the avian song system emphasizing its bilateral organization. Sound is produced in a bipartite vocal organ known as the syrinx. The syringeal muscles that make up each half of the vocal organ are innervated by motoneurons in the ipsilateral nXIIts. This nucleus receives its own motor commands from HVC and RA in the ipsilateral forebrain. Therefore, motor commands generated in the left hemisphere (highlighted in red) end up activating muscles on the left half of the syrinx, while those on the right side (highlighted in blue) activate syringeal muscles on the right side. Motor commands from each hemisphere are also sent to brainstem nuclei that form part of the bilaterally organized vocal-respiratory network (VRN), which is highly interconnected across the midline. The VRN sends motor commands to the muscles of respiration. This network also sends major projections back to the forebrain nucleus HVC via the intermediary of the thalamic relay nucleus uvaeformis (Uva). These bottom-up projections are thought to synchronize activity in both hemispheres and might play a role in the rapid hemispheric switching described by Wang et al.
© Copyright Policy
Related In: Results  -  Collection

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

pbio-0060269-g002: Bilateral Organization of the Song Motor Control SystemThis schematic is a simplified representation of the motor portion of the avian song system emphasizing its bilateral organization. Sound is produced in a bipartite vocal organ known as the syrinx. The syringeal muscles that make up each half of the vocal organ are innervated by motoneurons in the ipsilateral nXIIts. This nucleus receives its own motor commands from HVC and RA in the ipsilateral forebrain. Therefore, motor commands generated in the left hemisphere (highlighted in red) end up activating muscles on the left half of the syrinx, while those on the right side (highlighted in blue) activate syringeal muscles on the right side. Motor commands from each hemisphere are also sent to brainstem nuclei that form part of the bilaterally organized vocal-respiratory network (VRN), which is highly interconnected across the midline. The VRN sends motor commands to the muscles of respiration. This network also sends major projections back to the forebrain nucleus HVC via the intermediary of the thalamic relay nucleus uvaeformis (Uva). These bottom-up projections are thought to synchronize activity in both hemispheres and might play a role in the rapid hemispheric switching described by Wang et al.
Mentions: In songbirds, each hemisphere contains a discrete set of brain structures that control song production in adult birds [24]. 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. One of these projections goes directly to the ipsilateral brainstem's hypoglossal nucleus (nXIIts, the tracheosyringeal part of the hypoglossal nucleus), a motor output structure that exclusively innervates the ipsilateral syringeal muscles. The other major projection from RA innervates a series of highly interconnected vocal-respiratory nuclei in the ipsilateral brainstem, several of which send projections to respiratory motoneurons in the spinal cord. These nuclei are highly interconnected across the midline and can therefore be thought of as a bilaterally organized vocal-respiratory network (VRN).

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