Limits...
Roles for multifunctional and specialized spinal interneurons during motor pattern generation in tadpoles, zebrafish larvae, and turtles.

Berkowitz A, Roberts A, Soffe SR - Front Behav Neurosci (2010)

Bottom Line: These specialized neurons can contribute by changing the way central pattern generator (CPG) activity is initiated and by altering CPG composition and operation.The combined use of multifunctional and specialized neurons is now established as a principle of organization across a range of vertebrates.Future research may reveal common patterns of multifunctionality and specialization among interneurons controlling diverse movements and whether similar mechanisms exist in higher-order brain circuits that select among a wider array of complex movements.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, University of Oklahoma Norman, OK, USA.

ABSTRACT
The hindbrain and spinal cord can produce multiple forms of locomotion, escape, and withdrawal behaviors and (in limbed vertebrates) site-specific scratching. Until recently, the prevailing view was that the same classes of central nervous system neurons generate multiple kinds of movements, either through reconfiguration of a single, shared network or through an increase in the number of neurons recruited within each class. The mechanisms involved in selecting and generating different motor patterns have recently been explored in detail in some non-mammalian, vertebrate model systems. Work on the hatchling Xenopus tadpole, the larval zebrafish, and the adult turtle has now revealed that distinct kinds of motor patterns are actually selected and generated by combinations of multifunctional and specialized spinal interneurons. Multifunctional interneurons may form a core, multipurpose circuit that generates elements of coordinated motor output utilized in multiple behaviors, such as left-right alternation. But, in addition, specialized spinal interneurons including separate glutamatergic and glycinergic classes are selectively activated during specific patterns: escape-withdrawal, swimming and struggling in tadpoles and zebrafish, and limb withdrawal and scratching in turtles. These specialized neurons can contribute by changing the way central pattern generator (CPG) activity is initiated and by altering CPG composition and operation. The combined use of multifunctional and specialized neurons is now established as a principle of organization across a range of vertebrates. Future research may reveal common patterns of multifunctionality and specialization among interneurons controlling diverse movements and whether similar mechanisms exist in higher-order brain circuits that select among a wider array of complex movements.

No MeSH data available.


Related in: MedlinePlus

Example of a T neuron, a morphological type of turtle spinal interneuron that is rhythmically activated during all three forms of ipsilateral scratching, as well as forward swimming. Int, interneuron; KE, knee extensor; HF, hip flexor; HE, hip extensor; Stim., stimulus; arrows indicate scratch stimulus onset/offset. Modified from Berkowitz (2008), with permission of the American Physiological Society.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2903196&req=5

Figure 7: Example of a T neuron, a morphological type of turtle spinal interneuron that is rhythmically activated during all three forms of ipsilateral scratching, as well as forward swimming. Int, interneuron; KE, knee extensor; HF, hip flexor; HE, hip extensor; Stim., stimulus; arrows indicate scratch stimulus onset/offset. Modified from Berkowitz (2008), with permission of the American Physiological Society.

Mentions: Within the set of scratch/swim interneurons is a morphologically defined group called transverse interneurons, or T neurons (Berkowitz et al., 2006). T neurons have dendrites that are elongated within the transverse plane but relatively short along the rostrocaudal axis. T neurons are strongly and rhythmically activated during all forms of scratching and are also activated during forward swimming (Figure 7), and usually during ipsilateral limb withdrawal as well (Berkowitz et al., 2006; Berkowitz, 2008). T neurons are good candidates to contribute to rhythm/pattern generation and/or to be last-order premotor interneurons, because T neurons as a group have larger scratch membrane potential oscillations and reach higher peak firing rates during scratching than other scratch-activated interneurons. T neurons as a group also have briefer action potentials and afterhyperpolarizations than other scratch-activated interneurons. T neurons can also have axons that terminate within the ventral horn of the hindlimb enlargement, consistent with their having relatively direct effects on hindlimb motor output.


Roles for multifunctional and specialized spinal interneurons during motor pattern generation in tadpoles, zebrafish larvae, and turtles.

Berkowitz A, Roberts A, Soffe SR - Front Behav Neurosci (2010)

Example of a T neuron, a morphological type of turtle spinal interneuron that is rhythmically activated during all three forms of ipsilateral scratching, as well as forward swimming. Int, interneuron; KE, knee extensor; HF, hip flexor; HE, hip extensor; Stim., stimulus; arrows indicate scratch stimulus onset/offset. Modified from Berkowitz (2008), with permission of the American Physiological Society.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2903196&req=5

Figure 7: Example of a T neuron, a morphological type of turtle spinal interneuron that is rhythmically activated during all three forms of ipsilateral scratching, as well as forward swimming. Int, interneuron; KE, knee extensor; HF, hip flexor; HE, hip extensor; Stim., stimulus; arrows indicate scratch stimulus onset/offset. Modified from Berkowitz (2008), with permission of the American Physiological Society.
Mentions: Within the set of scratch/swim interneurons is a morphologically defined group called transverse interneurons, or T neurons (Berkowitz et al., 2006). T neurons have dendrites that are elongated within the transverse plane but relatively short along the rostrocaudal axis. T neurons are strongly and rhythmically activated during all forms of scratching and are also activated during forward swimming (Figure 7), and usually during ipsilateral limb withdrawal as well (Berkowitz et al., 2006; Berkowitz, 2008). T neurons are good candidates to contribute to rhythm/pattern generation and/or to be last-order premotor interneurons, because T neurons as a group have larger scratch membrane potential oscillations and reach higher peak firing rates during scratching than other scratch-activated interneurons. T neurons as a group also have briefer action potentials and afterhyperpolarizations than other scratch-activated interneurons. T neurons can also have axons that terminate within the ventral horn of the hindlimb enlargement, consistent with their having relatively direct effects on hindlimb motor output.

Bottom Line: These specialized neurons can contribute by changing the way central pattern generator (CPG) activity is initiated and by altering CPG composition and operation.The combined use of multifunctional and specialized neurons is now established as a principle of organization across a range of vertebrates.Future research may reveal common patterns of multifunctionality and specialization among interneurons controlling diverse movements and whether similar mechanisms exist in higher-order brain circuits that select among a wider array of complex movements.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, University of Oklahoma Norman, OK, USA.

ABSTRACT
The hindbrain and spinal cord can produce multiple forms of locomotion, escape, and withdrawal behaviors and (in limbed vertebrates) site-specific scratching. Until recently, the prevailing view was that the same classes of central nervous system neurons generate multiple kinds of movements, either through reconfiguration of a single, shared network or through an increase in the number of neurons recruited within each class. The mechanisms involved in selecting and generating different motor patterns have recently been explored in detail in some non-mammalian, vertebrate model systems. Work on the hatchling Xenopus tadpole, the larval zebrafish, and the adult turtle has now revealed that distinct kinds of motor patterns are actually selected and generated by combinations of multifunctional and specialized spinal interneurons. Multifunctional interneurons may form a core, multipurpose circuit that generates elements of coordinated motor output utilized in multiple behaviors, such as left-right alternation. But, in addition, specialized spinal interneurons including separate glutamatergic and glycinergic classes are selectively activated during specific patterns: escape-withdrawal, swimming and struggling in tadpoles and zebrafish, and limb withdrawal and scratching in turtles. These specialized neurons can contribute by changing the way central pattern generator (CPG) activity is initiated and by altering CPG composition and operation. The combined use of multifunctional and specialized neurons is now established as a principle of organization across a range of vertebrates. Future research may reveal common patterns of multifunctionality and specialization among interneurons controlling diverse movements and whether similar mechanisms exist in higher-order brain circuits that select among a wider array of complex movements.

No MeSH data available.


Related in: MedlinePlus