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Y. Uchino - One of the best experts on this subject based on the ideXlab platform.

  • properties and axonal trajectories of posterior semicircular canal nerve activated Vestibulospinal neurons
    Experimental Brain Research, 2008
    Co-Authors: Keisuke Kushiro, Naoharu Kitajima, Rishu Bai, Akemi Sugitakitajima, Y. Uchino
    Abstract:

    We studied the axonal projections of Vestibulospinal neurons activated from the posterior semicircular canal. The axonal projection level, axonal pathway, and location of the Vestibulospinal neurons originating from the PC were investigated in seven decerebrated cats. Selective electrical stimulation was applied to the PC nerve, and extracellular recordings in the vestibular nuclei were performed. The properties of the PC nerve-activated Vestibulospinal neurons were then studied. To estimate the neural pathway in the spinal cord, floating electrodes were placed at the ipsilateral (i) and contralateral (c) lateral Vestibulospinal Tract (LVST) and Medial Vestibulospinal Tract (MVST) at the C1/C2 junction. To elucidate the projection level, floating electrodes were placed at i-LVST and MVST at the C3, T1, and L3 segments in the spinal cord. Collision block test between orthodromic inputs from the PC nerve and antidromic inputs from the spinal cord verified the existence of the Vestibulospinal neurons in the vestibular nuclei. Most (44/47) of the PC nerve-activated Vestibulospinal neurons responded to orthodromic stimulation to the PC nerve with a short (<1.4 ms) latency, indicating that they were second-order Vestibulospinal neurons. The rest (3/47) responded with a longer (≥1.4 ms) latency, indicating the existence of polysynaptic connections. In 36/47 PC nerve-activated Vestibulospinal neurons, the axonal pathway was histologically verified to lie in the spinal cord. The axons of 17/36 Vestibulospinal neurons projected to the i-LVST, whereas 14 neurons projected to the MVST, and 5 to the c-LVST. The spinal segment levels of projection of these neurons elucidated that the axons of most (15/17) of Vestibulospinal neurons passing through the i-LVST reached the L3 segment level; none (0/14) of the neurons passing through the MVST extended to the L3 segment level; most (13/14) of them did not descend lower than the C3 segment level. In relation to the latency and the pathway, 33/36 PC nerve-activated Vestibulospinal neurons were second-order neurons, whereas the remaining three were polysynaptic neurons. Of these, 33 second-order Vestibulospinal neurons, 16 passed through the i-LVST, while 13 and 4 descended through the MVST and c-LVST, respectively. The remaining three were polysynaptic neurons. Histological analysis showed that most of the PC nerve-activated Vestibulospinal neurons were located within a specific area in the Medial part of the lateral vestibular nucleus and the rostral part of the descending vestibular nucleus. In conclusion, it was suggested that PC nerve-activated Vestibulospinal neurons that were located within a focal area of the vestibular nuclei have strong connections with the lower segments of the spinal cord and are related to postural stability that is maintained by the short latency Vestibulospinal reflex.

  • Otolith and canal integration on single vestibular neurons in cats
    Experimental Brain Research, 2005
    Co-Authors: Y. Uchino, M. Sasaki, H Sato, Eiichi Kawamoto
    Abstract:

    In this review, based primarily on work from our laboratory, but related to previous studies, we summarize what is known about the convergence of vestibular afferent inputs onto single vestibular neurons activated by selective stimulation of individual vestibular nerve branches. Horizontal semicircular canal (HC), anterior semicircular canal (AC), posterior semicircular canal (PC), utricular (UT), and saccular (SAC) nerves were selectively stimulated in decerebrate cats. All recorded neurons were classified as either projection neurons, which consisted of Vestibulospinal (VS), vestibulo-oculospinal (VOS), vestibulo-ocular (VO) neurons, or non-projection neurons, which we simply term “vestibular″ (V) neurons. The first three types could be successfully activated antidromically from oculomotor/trochlear nuclei and/or spinal cord, and the last type could not be activated antidromically from either site. A total of 1228 neurons were activated by stimulation of various nerve pair combinations. Convergent neurons were located in the caudoventral part of the lateral, the rostral part of the descending, and the Medial vestibular nuclei. Otolith-activated vestibular neurons in the superior vestibular nucleus were extremely rare. A high percentage of neurons received excitatory inputs from two nerve pairs, a small percentage received reciprocal convergent inputs and even fewer received inhibitory inputs from both nerves. More than 30% of vestibular neurons received convergent inputs from vertical semicircular canal/otolith nerve pairs. In contrast, only half as many received convergent inputs from HC/otolith-nerve pairs, implying that convergent input from vertical semicircular canal and otolith-nerve pairs may play a more important role than that played by inputs from horizontal semicircular canal and otolith-nerve pairs. Convergent VS neurons projected through the ipsilateral lateral Vestibulospinal Tract (i-LVST) and the Medial Vestibulospinal Tract (MVST). Almost all the VOS neurons projected through the MVST. Convergent neurons projecting to the oculomotor/trochlear nuclei were much fewer in number than those projecting to the spinal cord. Some of the convergent neurons that receive both canal and otolith input may contribute to the short-latency pathway of the vestibulocollic reflex. The functional significance of these convergences is discussed.

  • Convergence of the anterior semicircular canal and otolith afferents on cat single vestibular neurons
    Experimental Brain Research, 2002
    Co-Authors: M. Sasaki, Midori Imagawa, H Sato, H Meng, Y. Uchino
    Abstract:

    The convergence between the anterior semicircular canal (AC) and utricular (UT) inputs, as well as the convergence between the AC and saccular (SAC) inputs in single vestibular neurons of decerebrated cats were investigated. Postsynaptic potentials were recorded intracellularly after selective stimulation of each pair of vestibular nerves AC/UT or AC/SAC. Neurons were recorded from the central parts of the vestibular nuclei, where the otolith afferents mainly terminate. Of a total of 105 neurons that were activated after stimulation of the AC and UT nerves, 42 received convergent inputs. Thirty-eight of these neurons received excitatory inputs from both afferents. Convergent neurons were further classified into Vestibulospinal ( n =28) and vestibulooculospinal ( n =6) neurons by antidromic activation from the border between the C1 and C2 spinal cord and the oculomotor or trochlear nucleus. Eight neurons that were not antidromically activated from either site were classified as vestibular neurons. Forty three percent of the convergent Vestibulospinal neurons and most of the convergent vestibulooculospinal neurons projected to the spinal cord through the Medial Vestibulospinal Tract. The remaining Vestibulospinal and vestibulooculospinal neurons descended through the ipsilateral lateral Vestibulospinal Tract. Of a total of 118 neurons that were activated after stimulation of the AC and/or SAC nerves, 51 received convergent inputs (27 Vestibulospinal, 4 vestibulooculospinal, 5 vestibuloocular and 15 vestibular neurons). Forty-two of the convergent neurons received excitatory inputs from both afferents. Thirty seven percent of the convergent Vestibulospinal neurons and all of the convergent vestibulooculospinal neurons projected to the spinal cord through the Medial Vestibulospinal Tract. The remaining Vestibulospinal and vestibulooculospinal neurons descended through the ipsilateral lateral Vestibulospinal Tract.

  • Properties of utricular-activated vestibular neurons that project to the contralateral vestibular nuclei in the cat
    Experimental Brain Research, 2002
    Co-Authors: R. Bai, Midori Imagawa, M. Sasaki, H Sato, H Meng, Y. Uchino
    Abstract:

    The properties of utricular (UT)-activated vestibular neurons that send axons to the contralateral vestibular nuclei (commissural neurons) were investigated intracellularly or extracellularly in decerebrate cats. A total of 27 vestibular neurons were orthodromically activated by stimulation of UT nerves and antidromically activated by stimulation of the contralateral vestibular nuclei. All neurons tested were classified as Vestibulospinal (VS), vestibulooculospinal (VOS), vestibuloocular (VO), and unidentified vestibular neurons (V) after antidromic stimulation of the spinal cord and oculomotor/trochlear nuclei. Most UT-activated commissural neurons (20/27) received monosynaptic inputs. Twelve of 27 commissural neurons were located in the Medial vestibular nucleus, 5 were in the lateral vestibular nucleus, 10 were in the descending vestibular nucleus, and no commissural neurons were recorded in the superior vestibular nucleus. Seven of 27 neurons were commissural VS neurons, 9 of 27 were commissural VOS neurons, and 11 of 27 were commissural V neurons. No commissural VO neurons were found. All VOS neurons and 3 VS neurons issued descending axons via the Medial Vestibulospinal Tract. We also studied convergent inputs from the posterior semicircular canal (PC) nerve onto UT-activated commissural neurons. Five of 27 UT-activated commissural neurons received converging inputs from the PC nerves.

  • Convergence of the horizontal semicircular canal and otolith afferents on cat single vestibular neurons
    Experimental Brain Research, 2001
    Co-Authors: Mohammad Zakir, H Sato, H Meng, Y. Uchino
    Abstract:

    We studied the convergence of two afferent pairs of single vestibular neurons by selective stimulation of the horizontal semicircular canal (HC) and saccular (SAC) nerves, and the HC and utricular (UT) nerves in decerebrate cats. All recorded neurons were classified as Vestibulospinal (VS), vestibulo-oculospinal (VOS) or vestibulo-ocular (VO), by antidromic stimulation from the oculomotor/trochlear nuclei and the spinal cord: neurons that could not be activated from any test sites were classified as vestibular (V) neurons. Of a total of 125 neurons activated by stimulation of the HC/SAC nerves, 21(17%) received convergent inputs. Twelve of 21 neurons received monosynaptic excitatory inputs from both nerves. About half (9/21, 43%) of the convergent neurons were classified as VS neurons, the majority of which descended through the ipsilateral lateral Vestibulospinal Tract (i-LVST). The HC/SAC convergent neurons were located in the rostral part of the descending, the Medial and the caudal-ventral part of the lateral vestibular nucleus. In 80 neurons studied by stimulation of the HC/UT nerves, both inputs converged in 12 (15%) neurons, more than half of which were VS neurons. Eight of 12 convergent neurons received excitatory inputs followed by inhibition from both the HC and UT nerves. A few convergent neurons (3/12) projected to the oculomotor/trochlear nucleus. Half of the convergent and non-convergent VS neurons descended to the spinal cord through the i-LVST, and the only one VOS convergent neuron via the Medial Vestibulospinal Tract. Most of the convergent neurons were located in the lateral, the rostral part of the descending and Medial vestibular nucleus. The percentages of HC/SAC and HC/UT convergence were half those of the posterior semicircular canal (PC), PC/SAC (33%) and PC/UT (33%) convergence, respectively. The convergent neurons receiving the HC and otolith inputs may contribute at least partly to the vestibulocollic reflex.

H Sato - One of the best experts on this subject based on the ideXlab platform.

  • Otolith and canal integration on single vestibular neurons in cats
    Experimental Brain Research, 2005
    Co-Authors: Y. Uchino, M. Sasaki, H Sato, Eiichi Kawamoto
    Abstract:

    In this review, based primarily on work from our laboratory, but related to previous studies, we summarize what is known about the convergence of vestibular afferent inputs onto single vestibular neurons activated by selective stimulation of individual vestibular nerve branches. Horizontal semicircular canal (HC), anterior semicircular canal (AC), posterior semicircular canal (PC), utricular (UT), and saccular (SAC) nerves were selectively stimulated in decerebrate cats. All recorded neurons were classified as either projection neurons, which consisted of Vestibulospinal (VS), vestibulo-oculospinal (VOS), vestibulo-ocular (VO) neurons, or non-projection neurons, which we simply term “vestibular″ (V) neurons. The first three types could be successfully activated antidromically from oculomotor/trochlear nuclei and/or spinal cord, and the last type could not be activated antidromically from either site. A total of 1228 neurons were activated by stimulation of various nerve pair combinations. Convergent neurons were located in the caudoventral part of the lateral, the rostral part of the descending, and the Medial vestibular nuclei. Otolith-activated vestibular neurons in the superior vestibular nucleus were extremely rare. A high percentage of neurons received excitatory inputs from two nerve pairs, a small percentage received reciprocal convergent inputs and even fewer received inhibitory inputs from both nerves. More than 30% of vestibular neurons received convergent inputs from vertical semicircular canal/otolith nerve pairs. In contrast, only half as many received convergent inputs from HC/otolith-nerve pairs, implying that convergent input from vertical semicircular canal and otolith-nerve pairs may play a more important role than that played by inputs from horizontal semicircular canal and otolith-nerve pairs. Convergent VS neurons projected through the ipsilateral lateral Vestibulospinal Tract (i-LVST) and the Medial Vestibulospinal Tract (MVST). Almost all the VOS neurons projected through the MVST. Convergent neurons projecting to the oculomotor/trochlear nuclei were much fewer in number than those projecting to the spinal cord. Some of the convergent neurons that receive both canal and otolith input may contribute to the short-latency pathway of the vestibulocollic reflex. The functional significance of these convergences is discussed.

  • Convergence of the anterior semicircular canal and otolith afferents on cat single vestibular neurons
    Experimental Brain Research, 2002
    Co-Authors: M. Sasaki, Midori Imagawa, H Sato, H Meng, Y. Uchino
    Abstract:

    The convergence between the anterior semicircular canal (AC) and utricular (UT) inputs, as well as the convergence between the AC and saccular (SAC) inputs in single vestibular neurons of decerebrated cats were investigated. Postsynaptic potentials were recorded intracellularly after selective stimulation of each pair of vestibular nerves AC/UT or AC/SAC. Neurons were recorded from the central parts of the vestibular nuclei, where the otolith afferents mainly terminate. Of a total of 105 neurons that were activated after stimulation of the AC and UT nerves, 42 received convergent inputs. Thirty-eight of these neurons received excitatory inputs from both afferents. Convergent neurons were further classified into Vestibulospinal ( n =28) and vestibulooculospinal ( n =6) neurons by antidromic activation from the border between the C1 and C2 spinal cord and the oculomotor or trochlear nucleus. Eight neurons that were not antidromically activated from either site were classified as vestibular neurons. Forty three percent of the convergent Vestibulospinal neurons and most of the convergent vestibulooculospinal neurons projected to the spinal cord through the Medial Vestibulospinal Tract. The remaining Vestibulospinal and vestibulooculospinal neurons descended through the ipsilateral lateral Vestibulospinal Tract. Of a total of 118 neurons that were activated after stimulation of the AC and/or SAC nerves, 51 received convergent inputs (27 Vestibulospinal, 4 vestibulooculospinal, 5 vestibuloocular and 15 vestibular neurons). Forty-two of the convergent neurons received excitatory inputs from both afferents. Thirty seven percent of the convergent Vestibulospinal neurons and all of the convergent vestibulooculospinal neurons projected to the spinal cord through the Medial Vestibulospinal Tract. The remaining Vestibulospinal and vestibulooculospinal neurons descended through the ipsilateral lateral Vestibulospinal Tract.

  • Properties of utricular-activated vestibular neurons that project to the contralateral vestibular nuclei in the cat
    Experimental Brain Research, 2002
    Co-Authors: R. Bai, Midori Imagawa, M. Sasaki, H Sato, H Meng, Y. Uchino
    Abstract:

    The properties of utricular (UT)-activated vestibular neurons that send axons to the contralateral vestibular nuclei (commissural neurons) were investigated intracellularly or extracellularly in decerebrate cats. A total of 27 vestibular neurons were orthodromically activated by stimulation of UT nerves and antidromically activated by stimulation of the contralateral vestibular nuclei. All neurons tested were classified as Vestibulospinal (VS), vestibulooculospinal (VOS), vestibuloocular (VO), and unidentified vestibular neurons (V) after antidromic stimulation of the spinal cord and oculomotor/trochlear nuclei. Most UT-activated commissural neurons (20/27) received monosynaptic inputs. Twelve of 27 commissural neurons were located in the Medial vestibular nucleus, 5 were in the lateral vestibular nucleus, 10 were in the descending vestibular nucleus, and no commissural neurons were recorded in the superior vestibular nucleus. Seven of 27 neurons were commissural VS neurons, 9 of 27 were commissural VOS neurons, and 11 of 27 were commissural V neurons. No commissural VO neurons were found. All VOS neurons and 3 VS neurons issued descending axons via the Medial Vestibulospinal Tract. We also studied convergent inputs from the posterior semicircular canal (PC) nerve onto UT-activated commissural neurons. Five of 27 UT-activated commissural neurons received converging inputs from the PC nerves.

  • Convergence of the horizontal semicircular canal and otolith afferents on cat single vestibular neurons
    Experimental Brain Research, 2001
    Co-Authors: Mohammad Zakir, H Sato, H Meng, Y. Uchino
    Abstract:

    We studied the convergence of two afferent pairs of single vestibular neurons by selective stimulation of the horizontal semicircular canal (HC) and saccular (SAC) nerves, and the HC and utricular (UT) nerves in decerebrate cats. All recorded neurons were classified as Vestibulospinal (VS), vestibulo-oculospinal (VOS) or vestibulo-ocular (VO), by antidromic stimulation from the oculomotor/trochlear nuclei and the spinal cord: neurons that could not be activated from any test sites were classified as vestibular (V) neurons. Of a total of 125 neurons activated by stimulation of the HC/SAC nerves, 21(17%) received convergent inputs. Twelve of 21 neurons received monosynaptic excitatory inputs from both nerves. About half (9/21, 43%) of the convergent neurons were classified as VS neurons, the majority of which descended through the ipsilateral lateral Vestibulospinal Tract (i-LVST). The HC/SAC convergent neurons were located in the rostral part of the descending, the Medial and the caudal-ventral part of the lateral vestibular nucleus. In 80 neurons studied by stimulation of the HC/UT nerves, both inputs converged in 12 (15%) neurons, more than half of which were VS neurons. Eight of 12 convergent neurons received excitatory inputs followed by inhibition from both the HC and UT nerves. A few convergent neurons (3/12) projected to the oculomotor/trochlear nucleus. Half of the convergent and non-convergent VS neurons descended to the spinal cord through the i-LVST, and the only one VOS convergent neuron via the Medial Vestibulospinal Tract. Most of the convergent neurons were located in the lateral, the rostral part of the descending and Medial vestibular nucleus. The percentages of HC/SAC and HC/UT convergence were half those of the posterior semicircular canal (PC), PC/SAC (33%) and PC/UT (33%) convergence, respectively. The convergent neurons receiving the HC and otolith inputs may contribute at least partly to the vestibulocollic reflex.

  • Convergence patterns of the posterior semicircular canal and utricular inputs in single vestibular neurons in cats
    Experimental Brain Research, 2000
    Co-Authors: Mohammad Zakir, Keisuke Kushiro, H Sato, Y. Ogawa, Y. Uchino
    Abstract:

    The convergence of the posterior semicircular canal (PC) and utricular (UT) inputs in single vestibular nuclei neurons was studied intracellularly in decerebrate cats. A total of 160 vestibular neurons were orthodromically activated by selective stimulation of the PC and the UT nerve and classified according to whether or not they were antidromically activated from the spinal cord and oculomotor nuclei into Vestibulospinal (VS), vestibulooculospinal (VOS), vestibuloocular (VO), and unidentified vestibular neurons. Fifty-three (33%) of 160 vestibular neurons received convergent inputs from both the PC and UT nerves. Seventy-nine (49%) vestibular neurons responded to PC inputs alone, and 28 (18%) neurons received inputs only from the UT nerve. Of 53 convergent neurons, 8 (15%) were monosynaptically excited from both nerves. Thirty-five (66%) received monosynaptic excitatory inputs from the PC nerve and polysynaptic excitatory or inhibitory inputs from the UT nerve, or vice versa. Approximately one-third of VS and VOS neurons received convergent inputs. A majority of the VS neurons descended to the spinal cord through the lateral Vestibulospinal Tract, while almost all the VOS neurons descended to the spinal cord through the Medial Vestibulospinal Tract. The convergent neurons were found in all vestibular nuclei but more in the lateral nucleus and descending nucleus. The VS neurons were more numerous than VO neurons or VOS neurons.

Barry W. Peterson - One of the best experts on this subject based on the ideXlab platform.

  • Interdependence of Spatial Properties and Projection Patterns of Medial Vestibulospinal Tract Neurons in the Cat
    Journal of Neurophysiology, 1998
    Co-Authors: S. I. Perlmutter, Y. Iwamoto, James F. Baker, Barry W. Peterson
    Abstract:

    Perlmutter, S. I., Y. Iwamoto, J. F. Baker, and B. W. Peterson. Interdependence of spatial properties and projection patterns of Medial Vestibulospinal Tract neurons in the cat. J. Neurophysiol. 79: 270–284, 1998. Activity of vestibular nucleus neurons with axons in the ipsi- or contralateral Medial Vestibulospinal Tract was studied in decerebrate cats during sinusoidal, whole-body rotations in many planes in three-dimensional space. Antidromic activation of axon collaterals distinguished between neurons projecting only to neck segments from those with collaterals to C6 and/or oculomotor nucleus. Secondary neurons were identified by monosynaptic activation after labyrinth stimulation. A three-dimensional maximum activation direction vector (MAD) summarized the spatial properties of 151 of 169 neurons. The majority of secondary neurons (71%) terminated above the C6 segment. Of these, 43% had ascending collaterals to the oculomotor nucleus (VOC neurons), and 57% did not (VC neurons). The majority of VOC and VC neurons projected contralaterally and ipsilaterally, respectively. Most C6-projecting neurons could not be activated from oculomotor nucleus (V-C6 neurons) and projected primarily ipsilaterally. All VO-C6 neurons projected contralaterally. The distributions of MADs for secondary neurons with different projection patterns were different. Most VOC (84%) and contralaterally projecting VC (91%) neurons had MADs close to the activation vector of a semicircular canal pair, compared with 54% of ipsilaterally projecting VC (i-VC) and 39% of V-C6 neurons. Many i-VC (44%) and V-C6 (48%) neurons had responses suggesting convergent input from horizontal and vertical canal pairs. Horizontal and vertical gains were comparable for some, making it difficult to assign a primary canal input. MADs consistent with vertical-vertical canal pair convergence were less common. Type II yaw or type II roll responses were seen for 22% of the i-VC neurons, 68% of the V-C6 neurons, and no VOC cells. VO-C6 neurons had spatial properties between those of VOC and V-C6 neurons. These results suggest that secondary VOC neurons convey semicircular canal pair signals to both ocular and neck motor centers, perhaps linking eye and head movements. Secondary VC and V-C6 neurons carry more processed signals, possibly to drive neck and forelimb reflexes more selectively. Two groups of secondary i-VC neurons exhibited vertical-horizontal canal convergence similar to that present on neck muscles. The vertical-vertical canal convergence present on many neck muscles, however, was not present on Medial Vestibulospinal neurons. Spatial transformations achieved by the vestibulocollic reflex may occur in part on secondary neurons but further combination of canal signals must take place to generate compensatory muscle activity.

  • Interdependence of Spatial Properties and Projection Patterns of Medial Vestibulospinal Tract Neurons in the Cat
    Journal of neurophysiology, 1998
    Co-Authors: S. I. Perlmutter, Y. Iwamoto, James F. Baker, Barry W. Peterson
    Abstract:

    Perlmutter, S. I., Y. Iwamoto, J. F. Baker, and B. W. Peterson. Interdependence of spatial properties and projection patterns of Medial Vestibulospinal Tract neurons in the cat. J. Neurophysiol. 79...

  • Relation Between Axon Morphology in C1 Spinal Cord and Spatial Properties of Medial Vestibulospinal Tract Neurons in the Cat
    Journal of Neurophysiology, 1998
    Co-Authors: S. I. Perlmutter, Y. Iwamoto, James F. Baker, L. F. Barke, Barry W. Peterson
    Abstract:

    Perlmutter, S. I., Y. Iwamoto, L. F. Barke, J. F. Baker, and B. W. Peterson. Relation between axon morphology in C1 spinal cord and spatial properties of Medial Vestibulospinal Tract neurons in the...

S. I. Perlmutter - One of the best experts on this subject based on the ideXlab platform.

  • Interdependence of Spatial Properties and Projection Patterns of Medial Vestibulospinal Tract Neurons in the Cat
    Journal of Neurophysiology, 1998
    Co-Authors: S. I. Perlmutter, Y. Iwamoto, James F. Baker, Barry W. Peterson
    Abstract:

    Perlmutter, S. I., Y. Iwamoto, J. F. Baker, and B. W. Peterson. Interdependence of spatial properties and projection patterns of Medial Vestibulospinal Tract neurons in the cat. J. Neurophysiol. 79: 270–284, 1998. Activity of vestibular nucleus neurons with axons in the ipsi- or contralateral Medial Vestibulospinal Tract was studied in decerebrate cats during sinusoidal, whole-body rotations in many planes in three-dimensional space. Antidromic activation of axon collaterals distinguished between neurons projecting only to neck segments from those with collaterals to C6 and/or oculomotor nucleus. Secondary neurons were identified by monosynaptic activation after labyrinth stimulation. A three-dimensional maximum activation direction vector (MAD) summarized the spatial properties of 151 of 169 neurons. The majority of secondary neurons (71%) terminated above the C6 segment. Of these, 43% had ascending collaterals to the oculomotor nucleus (VOC neurons), and 57% did not (VC neurons). The majority of VOC and VC neurons projected contralaterally and ipsilaterally, respectively. Most C6-projecting neurons could not be activated from oculomotor nucleus (V-C6 neurons) and projected primarily ipsilaterally. All VO-C6 neurons projected contralaterally. The distributions of MADs for secondary neurons with different projection patterns were different. Most VOC (84%) and contralaterally projecting VC (91%) neurons had MADs close to the activation vector of a semicircular canal pair, compared with 54% of ipsilaterally projecting VC (i-VC) and 39% of V-C6 neurons. Many i-VC (44%) and V-C6 (48%) neurons had responses suggesting convergent input from horizontal and vertical canal pairs. Horizontal and vertical gains were comparable for some, making it difficult to assign a primary canal input. MADs consistent with vertical-vertical canal pair convergence were less common. Type II yaw or type II roll responses were seen for 22% of the i-VC neurons, 68% of the V-C6 neurons, and no VOC cells. VO-C6 neurons had spatial properties between those of VOC and V-C6 neurons. These results suggest that secondary VOC neurons convey semicircular canal pair signals to both ocular and neck motor centers, perhaps linking eye and head movements. Secondary VC and V-C6 neurons carry more processed signals, possibly to drive neck and forelimb reflexes more selectively. Two groups of secondary i-VC neurons exhibited vertical-horizontal canal convergence similar to that present on neck muscles. The vertical-vertical canal convergence present on many neck muscles, however, was not present on Medial Vestibulospinal neurons. Spatial transformations achieved by the vestibulocollic reflex may occur in part on secondary neurons but further combination of canal signals must take place to generate compensatory muscle activity.

  • Interdependence of Spatial Properties and Projection Patterns of Medial Vestibulospinal Tract Neurons in the Cat
    Journal of neurophysiology, 1998
    Co-Authors: S. I. Perlmutter, Y. Iwamoto, James F. Baker, Barry W. Peterson
    Abstract:

    Perlmutter, S. I., Y. Iwamoto, J. F. Baker, and B. W. Peterson. Interdependence of spatial properties and projection patterns of Medial Vestibulospinal Tract neurons in the cat. J. Neurophysiol. 79...

  • Relation Between Axon Morphology in C1 Spinal Cord and Spatial Properties of Medial Vestibulospinal Tract Neurons in the Cat
    Journal of Neurophysiology, 1998
    Co-Authors: S. I. Perlmutter, Y. Iwamoto, James F. Baker, L. F. Barke, Barry W. Peterson
    Abstract:

    Perlmutter, S. I., Y. Iwamoto, L. F. Barke, J. F. Baker, and B. W. Peterson. Relation between axon morphology in C1 spinal cord and spatial properties of Medial Vestibulospinal Tract neurons in the...

Keisuke Kushiro - One of the best experts on this subject based on the ideXlab platform.

  • Properties and axonal trajectories of posterior semicircular canal nerve-activated Vestibulospinal neurons
    Experimental Brain Research, 2008
    Co-Authors: Keisuke Kushiro, Naoharu Kitajima, Akemi Sugita-kitajima, Yoshio Uchino
    Abstract:

    We studied the axonal projections of Vestibulospinal neurons activated from the posterior semicircular canal. The axonal projection level, axonal pathway, and location of the Vestibulospinal neurons originating from the PC were investigated in seven decerebrated cats. Selective electrical stimulation was applied to the PC nerve, and extracellular recordings in the vestibular nuclei were performed. The properties of the PC nerve-activated Vestibulospinal neurons were then studied. To estimate the neural pathway in the spinal cord, floating electrodes were placed at the ipsilateral (i) and contralateral (c) lateral Vestibulospinal Tract (LVST) and Medial Vestibulospinal Tract (MVST) at the C1/C2 junction. To elucidate the projection level, floating electrodes were placed at i-LVST and MVST at the C3, T1, and L3 segments in the spinal cord. Collision block test between orthodromic inputs from the PC nerve and antidromic inputs from the spinal cord verified the existence of the Vestibulospinal neurons in the vestibular nuclei. Most (44/47) of the PC nerve-activated Vestibulospinal neurons responded to orthodromic stimulation to the PC nerve with a short (

  • properties and axonal trajectories of posterior semicircular canal nerve activated Vestibulospinal neurons
    Experimental Brain Research, 2008
    Co-Authors: Keisuke Kushiro, Naoharu Kitajima, Rishu Bai, Akemi Sugitakitajima, Y. Uchino
    Abstract:

    We studied the axonal projections of Vestibulospinal neurons activated from the posterior semicircular canal. The axonal projection level, axonal pathway, and location of the Vestibulospinal neurons originating from the PC were investigated in seven decerebrated cats. Selective electrical stimulation was applied to the PC nerve, and extracellular recordings in the vestibular nuclei were performed. The properties of the PC nerve-activated Vestibulospinal neurons were then studied. To estimate the neural pathway in the spinal cord, floating electrodes were placed at the ipsilateral (i) and contralateral (c) lateral Vestibulospinal Tract (LVST) and Medial Vestibulospinal Tract (MVST) at the C1/C2 junction. To elucidate the projection level, floating electrodes were placed at i-LVST and MVST at the C3, T1, and L3 segments in the spinal cord. Collision block test between orthodromic inputs from the PC nerve and antidromic inputs from the spinal cord verified the existence of the Vestibulospinal neurons in the vestibular nuclei. Most (44/47) of the PC nerve-activated Vestibulospinal neurons responded to orthodromic stimulation to the PC nerve with a short (<1.4 ms) latency, indicating that they were second-order Vestibulospinal neurons. The rest (3/47) responded with a longer (≥1.4 ms) latency, indicating the existence of polysynaptic connections. In 36/47 PC nerve-activated Vestibulospinal neurons, the axonal pathway was histologically verified to lie in the spinal cord. The axons of 17/36 Vestibulospinal neurons projected to the i-LVST, whereas 14 neurons projected to the MVST, and 5 to the c-LVST. The spinal segment levels of projection of these neurons elucidated that the axons of most (15/17) of Vestibulospinal neurons passing through the i-LVST reached the L3 segment level; none (0/14) of the neurons passing through the MVST extended to the L3 segment level; most (13/14) of them did not descend lower than the C3 segment level. In relation to the latency and the pathway, 33/36 PC nerve-activated Vestibulospinal neurons were second-order neurons, whereas the remaining three were polysynaptic neurons. Of these, 33 second-order Vestibulospinal neurons, 16 passed through the i-LVST, while 13 and 4 descended through the MVST and c-LVST, respectively. The remaining three were polysynaptic neurons. Histological analysis showed that most of the PC nerve-activated Vestibulospinal neurons were located within a specific area in the Medial part of the lateral vestibular nucleus and the rostral part of the descending vestibular nucleus. In conclusion, it was suggested that PC nerve-activated Vestibulospinal neurons that were located within a focal area of the vestibular nuclei have strong connections with the lower segments of the spinal cord and are related to postural stability that is maintained by the short latency Vestibulospinal reflex.

  • Convergence patterns of the posterior semicircular canal and utricular inputs in single vestibular neurons in cats
    Experimental Brain Research, 2000
    Co-Authors: Mohammad Zakir, Keisuke Kushiro, H Sato, Y. Ogawa, Y. Uchino
    Abstract:

    The convergence of the posterior semicircular canal (PC) and utricular (UT) inputs in single vestibular nuclei neurons was studied intracellularly in decerebrate cats. A total of 160 vestibular neurons were orthodromically activated by selective stimulation of the PC and the UT nerve and classified according to whether or not they were antidromically activated from the spinal cord and oculomotor nuclei into Vestibulospinal (VS), vestibulooculospinal (VOS), vestibuloocular (VO), and unidentified vestibular neurons. Fifty-three (33%) of 160 vestibular neurons received convergent inputs from both the PC and UT nerves. Seventy-nine (49%) vestibular neurons responded to PC inputs alone, and 28 (18%) neurons received inputs only from the UT nerve. Of 53 convergent neurons, 8 (15%) were monosynaptically excited from both nerves. Thirty-five (66%) received monosynaptic excitatory inputs from the PC nerve and polysynaptic excitatory or inhibitory inputs from the UT nerve, or vice versa. Approximately one-third of VS and VOS neurons received convergent inputs. A majority of the VS neurons descended to the spinal cord through the lateral Vestibulospinal Tract, while almost all the VOS neurons descended to the spinal cord through the Medial Vestibulospinal Tract. The convergent neurons were found in all vestibular nuclei but more in the lateral nucleus and descending nucleus. The VS neurons were more numerous than VO neurons or VOS neurons.

  • Convergence of posterior semicircular canal and saccular inputs in single vestibular nuclei neurons in cats
    Experimental Brain Research, 2000
    Co-Authors: H Sato, Midori Imagawa, Keisuke Kushiro, Mohammad Zakir, Y. Uchino
    Abstract:

    Convergence between posterior canal (PC) and saccular (SAC) inputs in single vestibular nuclei neurons was investigated in decerebrated cats. Postsynaptic potentials were recorded intracellularly after selective stimulation of the SAC and PC nerves. Stimulation of either the SAC or PC nerve orthodromically activated 143 vestibular nuclei neurons. Of these, 61 (43%) were antidromically activated by stimulation of the C1–C2 junction, 14 (10%) were antidromically activated by stimulation of the oculomotor or trochlear nucleus, and 14 (10%) were antidromically activated by stimulation of both the oculomotor or trochlear nucleus and the spinal cord. Fifty-four (38%) neurons were not activated by stimulation of either or both. We named these neurons Vestibulospinal (VS), vestibulo-ocular (VO), vestibulo-oculo-spinal (VOS) and vestibular (V) neurons, respectively. Both PC and SAC inputs converged in 47 vestibular nuclei neurons (26 VS, 2 VO, 6 VOS and 13 V neurons). Of these, 19 received monosynaptic excitatory inputs from both nerves. This input pattern was frequently seen in VS neurons. Approximately half of the convergent VS neurons descended to the spinal cord through the lateral Vestibulospinal Tract. The remaining half and all the convergent VOS neurons descended to the spinal cord through the Medial Vestibulospinal Tract. Most of the convergent neurons were located in the lateral nucleus or descending nucleus.

  • Saccular and utricular inputs to sternocleidomastoid motoneurons of decerebrate cats
    Experimental Brain Research, 1999
    Co-Authors: Keisuke Kushiro, Mohammad Zakir, H Sato, Y. Ogawa, Y. Uchino
    Abstract:

     Connections from the otolithic organs to sternocleidomastoid (SCM) motoneurons were studied in 20 decerebrate cats. The electrical stimulation was selective for the saccular or the utricular nerves. Postsynaptic potentials were recorded from antidromically identified SCM motoneurons; these muscles participate mainly in neck rotation and flexion. Partial transections of the brainstem at the level of the obex were performed to identify the possible pathway from the otolithic organs to the SCM motoneurons. Saccular or utricular nerve stimulation mainly evoked inhibitory postsynaptic potentials (IPSPs) in the ipsilateral SCM motoneurons. Some of the sacculus-induced IPSPs were preceded by small-amplitude excitatory PSPs (EPSPs). The latencies of the PSPs ranged from 1.8 to 3.1 ms after saccular nerve stimulation and from 1.7 to 2.8 ms after utricular nerve stimulation, indicating that most of the ipsilateral connections were disynaptic. In the contralateral SCM motoneurons, saccular nerve stimulation had no or faint effects, whereas utricular nerve stimulation evoked EPSPs in about two-thirds of neurons, and no visible PSPs in about one-third of neurons. The latencies of the EPSPs ranged from 1.5 to 2.0 ms, indicating the disynaptic connection. Thus, the results suggest a difference between the two otolithic innervating patterns of SCM motoneurons. After transection of the Medial Vestibulospinal Tract (MVST), saccular nerve stimulation did not evoke IPSPs at all in ipsilateral SCM motoneurons, but some (11/40) neurons showed small-amplitude EPSPs. Most (24/33) of the utricular-activated IPSPs disappeared after transection, whereas the other 9 neurons still indicated IPSPs. In the contralateral SCM motoneurons, no utricular-activated EPSPs were recorded after transection. These MVST transection results suggest that most of the otolith-SCM pathways are located in the MVST at the obex level. However, the results also suggest the possibility that other otolith-SCM pathways exist at the obex level.