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Evidence from retractor bulbi EMG for linearized motor control of conditioned nictitating membrane responses

Lepora, NF; Mavritsaki, E; Porrill, J; Yeo, CH; Evinger, C; Dean, P; (2007) Evidence from retractor bulbi EMG for linearized motor control of conditioned nictitating membrane responses. J NEUROPHYSIOL , 98 (4) 2074 - 2088. 10.1152/jn.00210.2007.

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Abstract

Classical conditioning of nictitating membrane (NM) responses in rabbits is a robust model learning system, and experimental evidence indicates that conditioned responses (CRs) are controlled by the cerebellum. It is unknown whether cerebellar control signals deal directly with the complex nonlinearities of the plant (blink-related muscles and peripheral tissues) or whether the plant is linearized to ensure a simple relation between cerebellar neuronal firing and CR profile. To study this question, the retractor bulbi muscle EMG was recorded with implanted electrodes during NM conditioning. Pooled activity in accessory abducens motoneurons was estimated from spike trains extracted from the EMG traces, and its temporal profile was found to have an approximately Gaussian shape with peak amplitude linearly related to CR amplitude. The relation between motoneuron activity and CR profiles was accurately fitted by a first-order linear filter, with each spike input producing an exponentially decaying impulse response with time constant of order 0.1 s. Application of this first-order plant model to CR data from other laboratories suggested that, in these cases also, motoneuron activity had a Gaussian profile, with time-of-peak close to unconditioned stimulus (US) onset and SD proportional to the interval between conditioned stimulus and US onsets. These results suggest that for conditioned NM responses the cerebellum is presented with a simplified "virtual" plant that is a linearized version of the underlying nonlinear biological system. Analysis of a detailed plant model suggests that one method for linearising the plant would be appropriate recruitment of motor units.

Type: Article
Title: Evidence from retractor bulbi EMG for linearized motor control of conditioned nictitating membrane responses
DOI: 10.1152/jn.00210.2007
Keywords: CS-US INTERVAL, CEREBELLAR INTERPOSITUS NUCLEUS, RABBIT ORYCTOLAGUS-CUNICULUS, ACCESSORY ABDUCENS NUCLEUS, EYELID RESPONSES, NEURONAL-ACTIVITY, INTERSTIMULUS INTERVAL, SIGNAL DECOMPOSITION, OCULOMOTOR PLANT, UNIT-ACTIVITY
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences > Neuro, Physiology and Pharmacology
URI: http://discovery.ucl.ac.uk/id/eprint/130852
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