Sensorimotor cortical representation in the rat and the role of the cortex in the production of sensory myoclonic jerks.

Abstract

SUMMARY1. After administration of 1,2-dihydroxybenzene (catechol) to anaesthetized rats, rabbits and cats, a reflex jerk consisting of three distinct components was evoked in the limb muscles by peripheral stimulation. The second component of the jerk in the forelimb muscles of all three animals was specifically abolished by lesions confined to the contralateral forelimb sensorimotor cortex.2. These lesions had no effect on the second response in either the hind limbs or in the forelimb ipsilateral to the lesion. The first and third responses were also unaffected.3. Lesions in the cat hind-limb cortex abolished the contralateral hind-limb second response, but not the ipsilateral hind-limb or forelimb response.4. In the rat and rabbit, unilateral hind-limb sensorimotor lesions were ineffective in completely abolishing the second response in the contralateral hind-leg muscles, and in addition, reduced the probability of occurrence of the response in the ipsilateral hind leg. Bilateral lesions abolished the response.5. Re-investigation of the sensory and motor representation of the hind limb in the rat cortex revealed that this is bilateral in nature. Shortlatency cortical responses (ca. 7*0 msec) could be evoked in one cortex by stimulation of either hind paw. The geometric centre of the cortical area from which these responses could be recorded was identical for each hind paw.6. After catechol injection, stimulation of the cortical surface with single anodal shocks of threshold strength produced responses at similar latency (ca. 8f0 msec) in both hind limbs.7. The behaviour of the second response after cortical lesions corresponds A. ANGEL AND R. N. LEMON closely with the pattern of the somatosensorimotor cortical representation. The latency of the response is such as to allow its production by a long-loop cortical reflex, and this possibility is discussed.

Electrocorticographic activity over sensorimotor cortex and motor function in awake behaving rats

“…The SEP over SMC after nerve stimulation is characterized by two pairs of biphasic peaks (i.e., P1-N1 and P2-N2) (Angel and Lemon 1975;Misiaszek and Brooke 2001;Nelson et al 2001). We examined SEPs in 34 animals with the reference electrode over the olfactory bulb.…”

Demonstrations

“…These responses were not totally abolished by acute section of the medullary pyramids, suggesting that other pathways are involved. Since the pyramidal tract is completely crossed in the rat, and since it appears to exert only weak effects on hind-limb motoneurones, it may be that such pathways are predominant in the production of the bilateral hind-limb responses evoked by unilateral stimulation of the hind-limb sensorimotor cortex in the rat (Angel & Lemon, 1975). Rats were anaesthetized with urethane (1.0 g/kg) intraperitoneally, after premeditation with trichloroethylene, and the medulla and left cortex exposed.…”

“…In the case of the muscular jerk evoked by auditory stimulation, the activation of x-motoneurones could be via the y system above. It has been shown in a previous study that the convulsant 1,2-dihydroxy-benzene (catechol) exerts powerful effects on descending motor pathways (Angel & Lemon, 1975). In the anaesthetized rat, single anodal shocks (strength 0-6-1-5 mA, duration 1 0 msec) applied to the cortical surface just rostral to the forepaw receiving area evoke short-latency responses in contralateral forelimb muscles.…”

“…response were capable of facilitating the polysynaptic reflex that can be set up in forelimb muscles by a test percutaneous shock applied to the forepaw (Angel & Lemon, 1973).…”

Some characteristics of the long‐latency component of the evoked muscle response induced by administration of catechol to the anaesthetized rat: a neurophysiological and neuropharmacological investigation

“…The reflex pathways giving rise to the two early components (Ml and M2) have been described previously (Angel & Lemon, 1973a, b;Angel & Dewhurst, 1978). It has been suggested that the third, long-latency component (M3) is a spinobulbo-spinal reflex (Angel & Lemon, 1973 a, b;1975). This component has some characteristics in common with spinobulbospinal (SBS) reflexes since both are abolished by transection of the spinal cord, unaffected by decerebration and they have similar latencies (Lemon, 1971;Shimamura, 1973).…”