Dimitri Ryczko | Université de Sherbrooke (original) (raw)

Papers by Dimitri Ryczko

Research paper thumbnail of A descending dopamine pathway conserved from basal vertebrates to mammals

Dopamine neurons are classically known to modulate locomotion indirectly through ascending projec... more Dopamine neurons are classically known to modulate locomotion indirectly through ascending projections to the basal ganglia that project down to brainstem locomotor networks. Their loss in Parkinson’s disease is devastating. In lampreys, we recently showed that brainstem networks also receive direct descending dopaminergic inputs that potentiate locomotor output. Here, we provide evidence that this descending dopaminergic pathway is conserved to higher vertebrates, including mammals. In salamanders, dopamine neurons projecting to the striatum or brainstem locomotor networks were partly intermingled. Stimulation of the dopaminergic region evoked dopamine release in brainstem locomotor networks and concurrent reticulospinal activity. In rats, some dopamine neurons projecting to the striatum also innervated the pedunculopontine nucleus, a known locomotor center, and stimulation of the dopaminergic region evoked pedunculopontine dopamine release in vivo. Finally, we found dopaminergic fibers in the human pedunculopontine nucleus. The conservation of a descending dopaminergic pathway across vertebrates warrants re-evaluating dopamine’s role in locomotion.

Research paper thumbnail of Dynamique de l'organisation fonctionnelle des réseaux locomoteurs chez la salamandre : du module rythmogène à une palette de modes locomoteurs

Research paper thumbnail of Faculty of 1000 evaluation for Separate microcircuit modules of distinct v2a interneurons and motoneurons control the speed of locomotion

F1000 - Post-publication peer review of the biomedical literature, 2015

Research paper thumbnail of Faculty of 1000 evaluation for Lhx3-chx10 reticulospinal neurons in locomotor circuits

F1000 - Post-publication peer review of the biomedical literature, 2014

Research paper thumbnail of Gait transitions between swimming and walking in salamander: lessons from numerical modeling and robotics

Research paper thumbnail of Dynamics of the axial locomotor network in the isolated spinal cord of the salamander

Research paper thumbnail of Dynamics of the axial locomotor network in intact, freely moving salamanders

Research paper thumbnail of Faculty of 1000 evaluation for Identification of a brainstem circuit regulating visual cortical state in parallel with locomotion

F1000 - Post-publication peer review of the biomedical literature, 2000

Research paper thumbnail of Faculty of 1000 evaluation for Deep brain stimulation of the midbrain locomotor region improves paretic hindlimb function after spinal cord injury in rats

F1000 - Post-publication peer review of the biomedical literature, 2000

Research paper thumbnail of Faculty of 1000 evaluation for A non-human primate model of bipedal locomotion under restrained condition allowing gait studies and single unit brain recordings

F1000 - Post-publication peer review of the biomedical literature, 2000

Research paper thumbnail of Faculty of 1000 evaluation for Cholinergic mesencephalic neurons are involved in gait and postural disorders in Parkinson disease

F1000 - Post-publication peer review of the biomedical literature, 2000

Research paper thumbnail of Faculty of 1000 evaluation for Evolutionary conservation of the basal ganglia as a common vertebrate mechanism for action selection

F1000 - Post-publication peer review of the biomedical literature, 2000

Research paper thumbnail of Faculty of 1000 evaluation for A structural and functional ground plan for neurons in the hindbrain of zebrafish

F1000 - Post-publication peer review of the biomedical literature, 2000

Research paper thumbnail of Faculty of 1000 evaluation for Principles governing recruitment of motoneurons during swimming in zebrafish

F1000 - Post-publication peer review of the biomedical literature, 2000

Research paper thumbnail of Faculty of 1000 evaluation for Optogenetic dissection reveals multiple rhythmogenic modules underlying locomotion

F1000 - Post-publication peer review of the biomedical literature, 2000

Research paper thumbnail of Faculty of 1000 evaluation for Regulation of parkinsonian motor behaviours by optogenetic control of basal ganglia circuitry

F1000 - Post-publication peer review of the biomedical literature, 2000

Research paper thumbnail of The mesencephalic locomotor region sends a bilateral glutamatergic drive to hindbrain reticulospinal neurons in a tetrapod.

Research paper thumbnail of Flexibility of the axial central pattern generator network for locomotion in the salamander.

Ryczko D, Knüsel J, Crespi A, Lamarque S, Mathou A, Ijspeert AJ, Cabelguen JM. Flexibility of the... more Ryczko D, Knüsel J, Crespi A, Lamarque S, Mathou A, Ijspeert AJ, Cabelguen JM. Flexibility of the axial central pattern generator network for locomotion in the salamander. In tetrapods, limb and axial movements are coordinated during locomotion. It is well established that inter-and intralimb coordination show considerable variations during ongoing locomotion. Much less is known about the flexibility of the axial musculoskeletal system during locomotion and the neural mechanisms involved. Here we examined this issue in the salamander Pleurodeles waltlii, which is capable of locomotion in both aquatic and terrestrial environments. Kinematics of the trunk and electromyograms from the mid-trunk epaxial myotomes were recorded during four locomotor behaviors in freely moving animals. A similar approach was used during rhythmic struggling movements since this would give some insight into the flexibility of the axial motor system. Our results show that each of the forms of locomotion and the struggling behavior is characterized by a distinct combination of mid-trunk motor patterns and cycle durations. Using in vitro electrophysiological recordings in isolated spinal cords, we observed that the spinal networks activated with bath-applied N-methyl-D-aspartate could generate these axial motor patterns. In these isolated spinal cord preparations, the limb motor nerve activities were coordinated with each mid-trunk motor pattern. Furthermore, isolated mid-trunk spinal cords and hemicords could generate the mid-trunk motor patterns. This indicates that each side of the cord comprises a network able to generate coordinated axial motor activity. The roles of descending and sensory inputs in the behavior-related changes in axial motor coordination are discussed. axial system; central pattern generator; locomotor flexibility; salamander

Research paper thumbnail of Forebrain dopamine neurons project down to a brainstem region controlling locomotion

Proceedings of the National Academy of Sciences of the United States of America, 2013

The contribution of dopamine (DA) to locomotor control is traditionally attributed to ascending d... more The contribution of dopamine (DA) to locomotor control is traditionally attributed to ascending dopaminergic projections from the substantia nigra pars compacta and the ventral tegmental area to the basal ganglia, which in turn project down to the mesencephalic locomotor region (MLR), a brainstem region controlling locomotion in vertebrates. However, a dopaminergic innervation of the pedunculopontine nucleus, considered part of the MLR, was recently identified in the monkey. The origin and role of this dopaminergic input are unknown. We addressed these questions in a basal vertebrate, the lamprey. Here we report a functional descending dopaminergic pathway from the posterior tuberculum (PT; homologous to the substantia nigra pars compacta and/or ventral tegmental area of mammals) to the MLR. By using triple labeling, we found that dopaminergic cells from the PT not only project an ascending pathway to the striatum, but send a descending projection to the MLR. In an isolated brain preparation, PT stimulation elicited excitatory synaptic inputs into patch-clamped MLR cells, accompanied by activity in reticulospinal cells. By using voltammetry coupled with electrophysiological recordings, we demonstrate that PT stimulation evoked DA release in the MLR, together with the activation of reticulospinal cells. In a semi-intact preparation, stimulation of the PT elicited reticulospinal activity together with locomotor movements. Microinjections of a D1 antagonist in the MLR decreased the locomotor output elicited by PT stimulation, whereas injection of DA had an opposite effect. It appears that this descending dopaminergic pathway has a modulatory role on MLR cells that are known to receive glutamatergic projections and promotes locomotor output.

Research paper thumbnail of The multifunctional mesencephalic locomotor region

Current pharmaceutical design, 2013

In 1966, Shik, Severin and Orlovskii discovered that electrical stimulation of a region at the ju... more In 1966, Shik, Severin and Orlovskii discovered that electrical stimulation of a region at the junction between the midbrain and hindbrain elicited controlled walking and running in the cat. The region was named Mesencephalic Locomotor Region (MLR). Since then, this locomotor center was shown to control locomotion in various vertebrate species, including the lamprey, salamander, stingray, rat, guinea-pig, rabbit or monkey. In human subjects asked to imagine they are walking, there is an increased activity in brainstem nuclei corresponding to the MLR (i.e. pedunculopontine, cuneiform and subcuneiform nuclei). Clinicians are now stimulating (deep brain stimulation) structures considered to be part of the MLR to alleviate locomotor symptoms of patients with Parkinson's disease. However, the anatomical constituents of the MLR still remain a matter of debate, especially relative to the pedunculopontine, cuneiform and subcuneiform nuclei. Furthermore, recent studies in lampreys have revealed that the MLR is more complex than a simple relay in a serial descending pathway activating the spinal locomotor circuits. It has multiple functions. Our goal is to review the current knowledge relative to the anatomical constituents of the MLR, and its physiological role, from lamprey to man. We will discuss these results in the context of the recent clinical studies involving stimulation of the MLR in patients with Parkinson's disease.

Research paper thumbnail of A descending dopamine pathway conserved from basal vertebrates to mammals

Dopamine neurons are classically known to modulate locomotion indirectly through ascending projec... more Dopamine neurons are classically known to modulate locomotion indirectly through ascending projections to the basal ganglia that project down to brainstem locomotor networks. Their loss in Parkinson’s disease is devastating. In lampreys, we recently showed that brainstem networks also receive direct descending dopaminergic inputs that potentiate locomotor output. Here, we provide evidence that this descending dopaminergic pathway is conserved to higher vertebrates, including mammals. In salamanders, dopamine neurons projecting to the striatum or brainstem locomotor networks were partly intermingled. Stimulation of the dopaminergic region evoked dopamine release in brainstem locomotor networks and concurrent reticulospinal activity. In rats, some dopamine neurons projecting to the striatum also innervated the pedunculopontine nucleus, a known locomotor center, and stimulation of the dopaminergic region evoked pedunculopontine dopamine release in vivo. Finally, we found dopaminergic fibers in the human pedunculopontine nucleus. The conservation of a descending dopaminergic pathway across vertebrates warrants re-evaluating dopamine’s role in locomotion.

Research paper thumbnail of Dynamique de l'organisation fonctionnelle des réseaux locomoteurs chez la salamandre : du module rythmogène à une palette de modes locomoteurs

Research paper thumbnail of Faculty of 1000 evaluation for Separate microcircuit modules of distinct v2a interneurons and motoneurons control the speed of locomotion

F1000 - Post-publication peer review of the biomedical literature, 2015

Research paper thumbnail of Faculty of 1000 evaluation for Lhx3-chx10 reticulospinal neurons in locomotor circuits

F1000 - Post-publication peer review of the biomedical literature, 2014

Research paper thumbnail of Gait transitions between swimming and walking in salamander: lessons from numerical modeling and robotics

Research paper thumbnail of Dynamics of the axial locomotor network in the isolated spinal cord of the salamander

Research paper thumbnail of Dynamics of the axial locomotor network in intact, freely moving salamanders

Research paper thumbnail of Faculty of 1000 evaluation for Identification of a brainstem circuit regulating visual cortical state in parallel with locomotion

F1000 - Post-publication peer review of the biomedical literature, 2000

Research paper thumbnail of Faculty of 1000 evaluation for Deep brain stimulation of the midbrain locomotor region improves paretic hindlimb function after spinal cord injury in rats

F1000 - Post-publication peer review of the biomedical literature, 2000

Research paper thumbnail of Faculty of 1000 evaluation for A non-human primate model of bipedal locomotion under restrained condition allowing gait studies and single unit brain recordings

F1000 - Post-publication peer review of the biomedical literature, 2000

Research paper thumbnail of Faculty of 1000 evaluation for Cholinergic mesencephalic neurons are involved in gait and postural disorders in Parkinson disease

F1000 - Post-publication peer review of the biomedical literature, 2000

Research paper thumbnail of Faculty of 1000 evaluation for Evolutionary conservation of the basal ganglia as a common vertebrate mechanism for action selection

F1000 - Post-publication peer review of the biomedical literature, 2000

Research paper thumbnail of Faculty of 1000 evaluation for A structural and functional ground plan for neurons in the hindbrain of zebrafish

F1000 - Post-publication peer review of the biomedical literature, 2000

Research paper thumbnail of Faculty of 1000 evaluation for Principles governing recruitment of motoneurons during swimming in zebrafish

F1000 - Post-publication peer review of the biomedical literature, 2000

Research paper thumbnail of Faculty of 1000 evaluation for Optogenetic dissection reveals multiple rhythmogenic modules underlying locomotion

F1000 - Post-publication peer review of the biomedical literature, 2000

Research paper thumbnail of Faculty of 1000 evaluation for Regulation of parkinsonian motor behaviours by optogenetic control of basal ganglia circuitry

F1000 - Post-publication peer review of the biomedical literature, 2000

Research paper thumbnail of The mesencephalic locomotor region sends a bilateral glutamatergic drive to hindbrain reticulospinal neurons in a tetrapod.

Research paper thumbnail of Flexibility of the axial central pattern generator network for locomotion in the salamander.

Ryczko D, Knüsel J, Crespi A, Lamarque S, Mathou A, Ijspeert AJ, Cabelguen JM. Flexibility of the... more Ryczko D, Knüsel J, Crespi A, Lamarque S, Mathou A, Ijspeert AJ, Cabelguen JM. Flexibility of the axial central pattern generator network for locomotion in the salamander. In tetrapods, limb and axial movements are coordinated during locomotion. It is well established that inter-and intralimb coordination show considerable variations during ongoing locomotion. Much less is known about the flexibility of the axial musculoskeletal system during locomotion and the neural mechanisms involved. Here we examined this issue in the salamander Pleurodeles waltlii, which is capable of locomotion in both aquatic and terrestrial environments. Kinematics of the trunk and electromyograms from the mid-trunk epaxial myotomes were recorded during four locomotor behaviors in freely moving animals. A similar approach was used during rhythmic struggling movements since this would give some insight into the flexibility of the axial motor system. Our results show that each of the forms of locomotion and the struggling behavior is characterized by a distinct combination of mid-trunk motor patterns and cycle durations. Using in vitro electrophysiological recordings in isolated spinal cords, we observed that the spinal networks activated with bath-applied N-methyl-D-aspartate could generate these axial motor patterns. In these isolated spinal cord preparations, the limb motor nerve activities were coordinated with each mid-trunk motor pattern. Furthermore, isolated mid-trunk spinal cords and hemicords could generate the mid-trunk motor patterns. This indicates that each side of the cord comprises a network able to generate coordinated axial motor activity. The roles of descending and sensory inputs in the behavior-related changes in axial motor coordination are discussed. axial system; central pattern generator; locomotor flexibility; salamander

Research paper thumbnail of Forebrain dopamine neurons project down to a brainstem region controlling locomotion

Proceedings of the National Academy of Sciences of the United States of America, 2013

The contribution of dopamine (DA) to locomotor control is traditionally attributed to ascending d... more The contribution of dopamine (DA) to locomotor control is traditionally attributed to ascending dopaminergic projections from the substantia nigra pars compacta and the ventral tegmental area to the basal ganglia, which in turn project down to the mesencephalic locomotor region (MLR), a brainstem region controlling locomotion in vertebrates. However, a dopaminergic innervation of the pedunculopontine nucleus, considered part of the MLR, was recently identified in the monkey. The origin and role of this dopaminergic input are unknown. We addressed these questions in a basal vertebrate, the lamprey. Here we report a functional descending dopaminergic pathway from the posterior tuberculum (PT; homologous to the substantia nigra pars compacta and/or ventral tegmental area of mammals) to the MLR. By using triple labeling, we found that dopaminergic cells from the PT not only project an ascending pathway to the striatum, but send a descending projection to the MLR. In an isolated brain preparation, PT stimulation elicited excitatory synaptic inputs into patch-clamped MLR cells, accompanied by activity in reticulospinal cells. By using voltammetry coupled with electrophysiological recordings, we demonstrate that PT stimulation evoked DA release in the MLR, together with the activation of reticulospinal cells. In a semi-intact preparation, stimulation of the PT elicited reticulospinal activity together with locomotor movements. Microinjections of a D1 antagonist in the MLR decreased the locomotor output elicited by PT stimulation, whereas injection of DA had an opposite effect. It appears that this descending dopaminergic pathway has a modulatory role on MLR cells that are known to receive glutamatergic projections and promotes locomotor output.

Research paper thumbnail of The multifunctional mesencephalic locomotor region

Current pharmaceutical design, 2013

In 1966, Shik, Severin and Orlovskii discovered that electrical stimulation of a region at the ju... more In 1966, Shik, Severin and Orlovskii discovered that electrical stimulation of a region at the junction between the midbrain and hindbrain elicited controlled walking and running in the cat. The region was named Mesencephalic Locomotor Region (MLR). Since then, this locomotor center was shown to control locomotion in various vertebrate species, including the lamprey, salamander, stingray, rat, guinea-pig, rabbit or monkey. In human subjects asked to imagine they are walking, there is an increased activity in brainstem nuclei corresponding to the MLR (i.e. pedunculopontine, cuneiform and subcuneiform nuclei). Clinicians are now stimulating (deep brain stimulation) structures considered to be part of the MLR to alleviate locomotor symptoms of patients with Parkinson's disease. However, the anatomical constituents of the MLR still remain a matter of debate, especially relative to the pedunculopontine, cuneiform and subcuneiform nuclei. Furthermore, recent studies in lampreys have revealed that the MLR is more complex than a simple relay in a serial descending pathway activating the spinal locomotor circuits. It has multiple functions. Our goal is to review the current knowledge relative to the anatomical constituents of the MLR, and its physiological role, from lamprey to man. We will discuss these results in the context of the recent clinical studies involving stimulation of the MLR in patients with Parkinson's disease.