Behavioural brain research
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The aim of this experiment was to investigate the effects of nicotinic acetylcholine receptor (nAChR) agonism and antagonism on learning. Eyeblink classical conditioning (750ms delay procedure) was tested for 15 daily sessions in a total of 82 young rabbits: 58 rabbits were tested in the paired procedure when the conditioned stimulus (CS) was always followed by the unconditioned stimulus (US), and 24 rabbits were tested in the explicitly unpaired procedure in which CS and US presentations were independent. We used the nAChR agonists nicotine and GTS-21 (a selective alpha7 nAChR partial agonist that antagonizes alpha4beta2 nAChRs) and the relatively nonselective nAChR antagonist, mecamylamine. ⋯ Both GTS-21 and nicotine reversed the deleterious effect of mecamylamine on the acquisition of conditioned responses. Combinations of GTS-21 or nicotine and mecamylamine did not cause sensitization or habituation in the unpaired condition. Reversal of mecamylamine-induced learning deficits by nicotine and GTS-21 suggests that nAChR agonists may have efficacy in ameliorating deficits caused by the loss of some types of nAChRs in diseases such as AD.
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The ability to voluntarily transit from one whole-body movement to another is based on the multisensory integration of visual, vestibular, and somatosensory information. The role of functional sensory ranges and mechanical constraints on the ability to voluntarily transit between whole-body movements was studied by requiring subjects to switch from a head-fixed-to-surface to head-fixed-in-space postural pattern (and vice versa). The head-fixed-to-surface pattern required an erect stance characterized by an in-phase relationship between center of pressure (CoP) and platform motion. ⋯ These findings demonstrate separate control processes for upper- and lower-body motion and that functional sensory ranges and mechanical constraints can facilitate or inhibit voluntary production of whole-body movements based on these control processes. The results are discussed in reference to neurological substrates that may be involved in the planning and execution of motor set-switching. The experimental protocol we employ may also have application as a diagnostic tool for the evaluation of postural deficits.