Gradient of adaptability in four different motor systems performing the same learned motor task in cats.
The ability of four different brainstem motoneuron pools to perform a newly acquired motor task was studied in alert cats. A classical conditioning of eyelid responses was carried out in (i). unoperated animals, and in animals with (ii). transection, 180 degrees rotation, and re-suture of the zygomatic facial nerve branch, (iii). a crossed anastomosis of the buccal to the zygomatic facial nerve branch and (iv). a hypoglossal-facial nerve anastomosis. Animals were conditioned with a delay paradigm using a tone (350 ms, 600 Hz, 90 dB) as conditioned stimulus, followed 250 ms later by an air puff (100 ms, 3 kg/cm2) as unconditioned stimulus. Animals with zygomatic nerve rotation performed conditioned responses (CRs) at control rate, with significantly larger amplitude, area and velocity, but a de-synchronized oscillatory pattern. Animals with buccal-zygomatic anastomosis acquired CRs at control rate, but these CRs had significantly smaller amplitude than those of controls and a de-synchronized pattern. Animals with a hypoglossal-facial anastomosis were unable to perform CRs. The trigeminal hyper-reflexia triggered by the axotomy was probably the origin of the large CRs after zygomatic nerve rotation. Trigeminal hyper-reflexia could also contribute to generation of the small CRs recorded after buccal-zygomatic anastomosis. Although trigeminal hyper-reflexia was also present following hypoglossal-facial anastomosis, hypoglossal motoneurons did not reach their firing threshold to perform CRs. In accordance with the embryonic origin of involved motoneurons, animals with buccal-zygomatic and hypoglossal-facial anastomoses moved the ipsilateral eyelid synchronously to mouth-related activities. It is suggested that there is a gradient of adaptability in motoneuron pools forced to perform new motor tasks through foreign muscles, which depends on their embryological origins and functional properties.
Gruart
Agnès
A
Laboratorio Andaluz de Biología, Universidad Pablo de Olavide, 41013-Sevilla, Spain.
Streppel
Michael
M
Guntinas-Lichius
Orlando
O
Angelov
Doychin N
DN
Neiss
Wolfram F
WF
Delgado-García
José M
JM
D000161:Acoustic Stimulation; D000714:Anastomosis, Surgical / Q000379:methods; D000818:Animals; D001522:Behavior, Animal; D001767:Blinking / Q000502:physiology*; D002415:Cats; D003214:Conditioning, Classical / Q000502:physiology*; D003215:Conditioning, Eyelid; D004525:Efferent Pathways / Q000502:physiology*; D004576:Electromyography; D005154:Facial Nerve / Q000502:physiology; D005260:Female; D007839:Functional Laterality; D007002:Hypoglossal Nerve / Q000502:physiology; D007700:Kinetics; D009055:Mouth / Q000502:physiology; D009801:Oculomotor Muscles / Q000502:physiology; D010812:Physical Stimulation; D011930:Reaction Time; D013997:Time Factors