Postural responses explored through classical conditioning

Abstract The purpose of the study was to determine whether the central nervous system (CNS) requires the sensory feedback generated by balance perturbations in order to trigger postural responses (PRs). In Experiment 1, twenty-one participants experienced toes-up support-surface tilts in two blocks....

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Bibliographic Details
Published in:	Neuroscience Vol. 164; no. 3; pp. 986 - 997
Main Authors:	Campbell, A.D, Dakin, C.J, Carpenter, M.G
Format:	Journal Article
Language:	English
Published:	Amsterdam Elsevier Ltd 15-12-2009 Elsevier
Subjects:	Acoustic Stimulation Adult balance Biological and medical sciences Conditioning (Psychology) - physiology Cues Electromyography Extinction, Psychological - physiology Feedback, Sensory - physiology Female Fundamental and applied biological sciences. Psychology Humans kinematics Male Muscle Contraction - physiology Muscle, Skeletal - innervation Muscle, Skeletal - physiology Neurology Neuropsychological Tests Postural Balance - physiology Posture - physiology posturography Reflex - physiology Reflex, Startle - physiology Vertebrates: nervous system and sense organs Young Adult PR posturography CNS stimulus onset asynchrony tibialis anterior SD conditioned stimulus balance UR EMG US SOA unconditioned response kinematics LMN TA central nervous system CS SOL unconditioned stimulus RF electromyography A/D rectus femoris lower motoneuron analog-to-digital postural response standard deviation soleus Electrophysiology Electromyography Classical conditioning
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Summary:	Abstract The purpose of the study was to determine whether the central nervous system (CNS) requires the sensory feedback generated by balance perturbations in order to trigger postural responses (PRs). In Experiment 1, twenty-one participants experienced toes-up support-surface tilts in two blocks. Control blocks involved unexpected balance perturbations whereas an auditory tone cued the onset of balance perturbations in Conditioning blocks. A single Cue-Only trial followed each block (Cue-OnlyControl and Cue-OnlyConditioning trials) in the absence of balance perturbations. Cue-OnlyConditioning trials were used to determine whether postural perturbations were required in order to trigger PRs. Counter-balancing the order of Control and Conditioning blocks allowed Cue-OnlyControl trials to examine both the audio–spinal/acoustic startle effects of the auditory cue and the carryover effects of the initial conditioning procedure. In Experiment 2, six participants first experienced five consecutive Tone-Only trials that were followed by twenty-five conditioning trials. After conditioning, five Tone-Only trials were again presented consecutively to first elicit and then extinguish the conditioned PRs. Surface electromyography (EMG) recorded muscle activity in soleus (SOL), tibialis anterior (TA) and rectus femoris (RF). EMG onset latencies and amplitudes were calculated together with the onset latency, peak and time-to-peak of shank angular accelerations. Results indicated that an auditory cue could be conditioned to initiate PRs in multiple muscles without balance-relevant sensory triggers generated by balance perturbations. Postural synergies involving excitation of TA and RF and inhibition of SOL were observed following the Cue-OnlyConditioning trials that resulted in shank angular accelerations in the direction required to counter the expected toes-up tilt. Postural synergies were triggered in response to the auditory cue even 15 min post-conditioning. Furthermore, conditioned PRs were quickly extinguished as participants became unresponsive by the third trial in extinction. In conclusion, our results reveal that the CNS does not require sensory feedback from postural perturbations in order to trigger PRs.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0306-4522 1873-7544
DOI:	10.1016/j.neuroscience.2009.07.042