Influence of proprioception on map of cortical responses

Abstract

Many investigators have prepared maps of motor cortex responses to stimulation at different sites, but hitherto none has attempted to demonstrate the alterations that occur in cortical maps when the peripheral conditions (such as the initial position of the responding limb) are altered. That this position may alter the response to stimulation of a particular cortical site has been demonstrated by Gelihorn (1948Gelihorn ( , 1949 and Gelihorn & Johnson (1950a); the influence of proprioceptive conditions on a map of cortical sites has not been shown, however. Since proprioceptive reinforcement will make subthreshold cortical stimuli effective for a particular muscle group and reduce or abolish the reactivity of the antagonistic group it seemed possible that variations in the degree of proprioceptive activity would induce changes in the size of the cortical area from which a certain muscle or group of muscles can be activated at a given intensity of stimulation.In the present paper examples of such maps will be given and described, and certain features of these maps will be discussed (see also Hyde, 1950). METHODIn a series of eleven monkeys (nine macaques, two Cynemolgi) a number of cortical sites were stimulated and electromyographic responses recorded in six muscles at a time, with the contralateral leg fixated in the two conditions of (a) knee flexed and ankle dorsi-flexed as compared with (b) knee extended and ankle plantarflexed, the hip being fixated in a neutral position and toes being free throughout. The methods of stimulation (repetitive condenser discharges from a Goodwin stimulator) and recording were the same as in earlier publications from this laboratory.In order to be sure that the cortex was relatively stable throughout the mapping, a number of different procedures were tried, of which the following was most satisfactory and was used in most if not all experiments of the present paper: four or five sites were stimulated with the leg in flexion, the same sites were then stimulated with the leg extended, and as a check the first of the sites would again be stimulated with the leg in flexion. If the first and last records of this (series) were quite similar, the series was considered valid. 24-2

Differential Effects of Abnormal Tactile Experience on Shaping Representation Patterns in Developing and Adult Motor Cortex

“…The adult-trimmed group displayed some similar changes, although of much lesser magnitude, consistent with previous conclusions that mature M1 representations retain a capacity for functional modification under the influence of changing sensory feedback (Gellhorn and Hyde, 1953;Sanes et al, 1992). The basis for such effects could be long-term changes in synapse number as a result of altered experience (K leim et al, 1996) or changes in synaptic efficacies of preexisting connections (Diamond et al, 1993;Donoghue et al, 1996) through long-term, activitydependent changes in neurochemical levels.…”

“…The functional properties of M1 neurons are strongly influenced by somatosensory feedback (Lemon and Porter, 1976;Zarzecki, 1989), and stimulation-evoked output from M1 can change on readjustments of limb position, a manipulation that presumably changes proprioceptive feedback (Gellhorn and Hyde, 1953;Sanes et al, 1992). Corresponding parts of representational maps in S1 and M1 are topographically linked by dense corticocortical connections (Jones et al, 1978;Izraeli and Porter, 1995); such connectivity is critical for learning new motor skills (Pavlides et al, 1993) and can display activity-dependent changes in functional efficacy (Sakamoto et al, 1987).…”

Cortical Representation and Functional Significance of the Corticomotoneuronal System

“…A further discussion of the phasic fluctua¬ tion of the amplitude of the monosynaptic response will be postponed until after the presentation of the different mapping experiments. In this connection, it should only be pointed out that from the experiments described a stimulus frequency of 20 to 25 per second is most convenient for the mapping experiments because these stimulation frequencies are the most effective for the building up of the monosynap¬ tic response, as shown by the short latency and high amplitude of the first phase of 15,17,20,25,30, and 35 per second) plotted against time from the beginning of the repetitive cortical stimulation. The amplitude values are given in per cent of the highest value obtained (100% in curve with a frequency of 25 per second).…”

Contribution to the Physiology of Willed Movements Based on the Analysis of Symmetrical Movements in a Case of Hemiplegia

“…p ro duce selectiv e ty p e s of fa c ilita tio n in m uscles w hich are fu n c tio n a lly a sso c ia te d w ith th e s tre tc h e d m uscle [9,13]. T he fa c ilita to ry actio n of th e se p ro p rio c e p tiv e im p u lses is fu rth e r illu s tra te d b y th e fa c t t h a t th e c o rtic a l a re a fro m w hich th e c o n tra c tio n of a m uscle can be elicited b y a given stim u lu s is in creased if th a t m uscle is s tre tc h e d a n d fix a te d [12]. I t is, th e re fo re , n o t su rp risin g t h a t th e A -m o v em en t o f th e le ft a rm th r o u g h its p ro p rio c e p tiv e a c tiv ity e x e rts a facilitato r y in flu en ce on th e n e u ro n s w h ich in n e rv a te th e fingers of th e left h a n d .…”

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T h a t v o lu n ta ry , skilled m o v e m en ts in th e ir enorm ous v a rie ty a n d a d a p ta b ility are th e re su lt of sen so ri-m o to r in te g ra tio n has been stre sse d b y n u m e ro u s a u th o rs [9,12,19,21,26,28]. T he chief re a sons a re : 1.

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