Electrophysiological properties of the somatotopic organization of the vestibulospinal system in the frog.
In experiments on the preparation of a frog perfused brain (Rana ridibunda), field and intracellular potentials were recorded from neurons of the vestibular nuclear complex following stimulation of the ipsilateral vestibular nerve and different levels of the spinal cord. Stimulation of the vestibular nerve evoked mono- and polysynaptic excitatory postsynaptic potentials and orthodromic action potentials. In parallel, an antidromic activation of vestibular neurons sending their axons to the labyrinth was recorded. Vestibulospinal neurons sending their axons to the cervical (C neurons) and lumbar (L neurons) enlargements of the spinal cord were identified by their antidromic activation. A rather high conduction velocity along vestibulospinal fibres (mean 15.47 m/s) was observed. A somatotopic arrangement of the vestibulospinal system was established in spite of extremely large overlapping zones for the fore- and hindlimb representations in the vestibular nuclear complex. The hindlimbs were represented more poorly than the forelimbs. Antidromic potentials of C and L neurons were recorded in the medial, descending and with the highest density in the lateral vestibular nuclei (Deiters' nucleus). C neurons were evenly distributed in the other vestibular nuclei studied, while L neurons were located predominantly in the caudal parts of the vestibular nuclear complex. The multiplicity of the origin of the vestibulospinal axons was established. Peculiarities of the functional correlation between the vestibular input and vestibulospinal system are discussed.
Fanardjian
V V
VV
L.A. Orbeli Institute of Physiology, National Academy of Sciences of Armenia, Yerevan, Republic of Armenia. vvfanar@pnas.sci.am
Manvelyan
L R
LR
Zakarian
V L
VL
Pogossian
V I
VI
Nasoyan
A M
AM
D000818:Animals; D001369:Axons / Q000502:physiology; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D007758:Ear, Inner / Q000294:innervation / Q000502:physiology; D004558:Electric Stimulation; D005071:Evoked Potentials; D019706:Excitatory Postsynaptic Potentials; D007839:Functional Laterality; D008564:Membrane Potentials; D009474:Neurons / Q000502:physiology*; D011895:Rana ridibunda; D011930:Reaction Time; D013116:Spinal Cord / Q000502:physiology*; D014725:Vestibular Nerve / Q000502:physiology*; D014726:Vestibular Nuclei / Q000502:physiology*