ABSTRACT
We evaluated the effects, in rats, of single and multiple low-level inhalation exposures to sarin. Rats were trained on a variable-interval, 56 s (VI56) schedule of food reinforcement and then exposed to sarin vapor (1.7-4.0 mg/m(3) x 60 min) or air control. The exposures did not produce clinical signs of toxicity other than miosis. Subsequently, performance on the VI56 and acquisition of a radial-arm maze spatial memory task was evaluated over approximately 11 weeks. Single exposures did not affect performance on the VI56 and had little effect on acquisition of the radial-arm maze task. Multiple exposures (4.0 mg/m(3) x 60 min/day x 3) disrupted performance on the VI56 schedule during the initial post-exposure sessions. The disruption, however, resolved after several days. Multiple exposures also produced a deficit on the radial-arm maze task in that sarin-exposed rats tended to take it longer to complete the maze and to make more errors. The deficit, however, resolved during the first three weeks of acquisition. These results demonstrate that in rats, inhalation exposure to sarin at levels below those causing overt signs of clinical toxicity can produce cognitive and performance deficits. Furthermore, the observed deficits do not appear to be persistent.
Subject(s)
Behavior, Animal/drug effects , Chemical Warfare Agents/toxicity , Cholinesterase Inhibitors/toxicity , Sarin/toxicity , Acetylcholinesterase/blood , Administration, Inhalation , Animals , Butyrylcholinesterase/blood , Cholinesterase Inhibitors/administration & dosage , Cholinesterase Inhibitors/blood , Conditioning, Operant/drug effects , Data Interpretation, Statistical , Food , Male , Maze Learning/drug effects , Psychomotor Performance/drug effects , Rats , Rats, Sprague-Dawley , Reinforcement Schedule , Sarin/administration & dosage , Sarin/bloodABSTRACT
Previous work has demonstrated that the graded internal structure of phonetic categories is sensitive to a variety of contextual factors. One such factor is place of articulation: The best exemplars of voiceless stop consonants along auditory bilabial and velar voice onset time (VOT) continua occur over different ranges of VOTs (Volaitis & Miller, 1992). In the present study, we exploited the McGurk effect to examine whether visual information for place of articulation also shifts the best exemplar range for voiceless consonants, following Green and Kuhl's (1989) demonstration of effects of visual place of articulation on the location of voicing boundaries. In Experiment 1, we established that /p/ and /t/ have different best exemplar ranges along auditory bilabial and alveolar VOT continua. We then found, in Experiment 2, a similar shift in the best-exemplar range for /t/ relative to that for /p/ when there was a change in visual place of articulation, with auditory place of articulation held constant. These findings indicate that the perceptual mechanisms that determine internal phonetic category structure are sensitive to visual, as well as to auditory, information.
