title: Motor correlates of phototaxis and associative learning in Hermissenda crassicornis.
abstract: Motor correlates of Hermissenda phototactic behavior and their modification by associative training were examined. Anatomical studies indicated the posterior three-fourths of the foot to be innervated by nerve P1 while the anterior portion was innervated by nerve P2. Bilateral lesions of either P1 or P2 pedal nerves in untrained animals reduced phototactic behavior. Extracellular recordings of pedal nerves from untrained animals revealed significant increases in total multi-unit activity (MUA) during a light presentation. Prominent components of nerve P2 activity were synchronous bursts apparent in peri-stimulus time (PST) histograms. Burst frequency was increased by light. Associative training resulted in significant decreases in light-evoked MUA frequency in P1 and light-evoked burst frequency in P2. Intracellular recordings were obtained from three classes of putative motoneurons with axons in P2. These were located using cobalt backfills and verified for each preparation by simultaneous extracellular recording from P2. The characteristic pattern of activity of these cells in the dark and its modulation by light was established.
authors: Department of Psychology, Princeton University, NJ 08544.
authors: W G
authors: WG
authors: Richards
authors: J
authors: J
authors: Farley
mesh_terms: D000818:Animals; D001245:Association Learning / Q000502:physiology*; D004594:Electrophysiology; D005110:Extracellular Space / Q000502:physiology; D007425:Intracellular Membranes / Q000502:physiology; D007858:Learning / Q000502:physiology*; D008027:Light; D008974:Mollusca / Q000502:physiology*; D009043:Motor Activity / Q000528:radiation effects*; D009420:Nervous System / Q000033:anatomy & histology / Q000473:pathology; D010805:Physical Conditioning, Animal