Chronic electromyographic analysis of circadian locomotor activity in crayfish

Abstract

Animals generally exhibit circadian rhythms of locomotor activity. They initiate locomotor behavior not only reflexively in response to external stimuli but also spontaneously in the absence of any specific stimulus. The neuronal mechanisms underlying circadian locomotor activity can, therefore, be based on the rhythmic changes in either reflexive efficacy or endogenous activity. In crayfish Procambarus clarkii, it can be determined by analyzing electromyographic (EMG) patterns of walking legs whether the walking behavior is initiated reflexively or spontaneously. In this study, we examined quantitatively the leg muscle activity that underlies the locomotor behavior showing circadian rhythms in crayfish. We newly developed a chronic EMG recording system that allowed the animal to freely behave under a tethered condition for more than 10 days. In the LD condition in which the animals exhibited LD entrainment, the rhythmic burst activity of leg muscles for stepping behavior was preceded by non-rhythmic tonic activation that lasted for 1323 ± 488 msec when the animal initiated walking. In DD and LL free-running conditions, the pre-burst activation lasted for 1779 ± 31 and 1517 ± 39 msec respectively. In the mechanical stimulus-evoked walking, the pre-burst activation ended within 79 ± 6 msec. These data suggest that periodic changes in the crayfish locomotor activity under the condition of LD entrainment or free-running are based on activity changes in the spontaneous initiation mechanism of walking behavior rather than those in the sensori-motor pathway connecting mechanoreceptors with leg movements.

Ecdysis behaviors and circadian rhythm of ecdysis in the stick insect, Carausius morosus

“…Given the relatively quiescent nature of the animals prior to actual ecdysis, the fairly immediate onset of ecdysis after mechanical stimulation may act as a form of defense, where the rhythmic motions may act as deterrents to predation. This is not surprising since many walking central pattern generators show both rhythmic and reflexive (to mechanical stimulation; Tomina et al, 2013) responses. Mechanical stimulation has been shown to induce premature eclosion in moths, even with no apparent adaptive value (Kammer and Kinnamon, 1977).…”

Electromyographic analysis of goal-directed grasping behavior in American lobster

“…Muscle activity has been used as an indicator of behavioral onset in previous studies (Kagaya and Takahata, 2010;Kagaya and Takahata, 2011). Electromyographic studies (Chikamoto et al, 2008;Tomina et al, 2013) revealed that the temporal pattern of leg muscle (merocarpodite flexor) activation is statistically different between spontaneously evoked and stimulus-evoked walking. In the current study, we made EMG recordings from the crusher claw muscles of lobster to characterize the motor program subserving spontaneous initiation of the grasping action by cheliped for manipulating foodstuff.…”

“…In the EMG studies using human subjects, it has been shown that EMG activity patterns are different in voluntary and stimulation-evoked muscle contraction (Hoffer et al, 1996). Previous studies using crayfish also successfully characterized EMG patterns in spontaneously initiated walking as different from those in mechanical stimulus-evoked walking (Chikamoto et al, 2008;Tomina et al, 2013). Those investigations revealed that a specific muscle of the walking leg was tonically activated prior to the onset of rhythmical stepping movements or bursting activity when the animal initiated walking spontaneously, and this pre-activation time was relatively shorter in the reflexive walking (Chikamoto et al, 2008;Tomina et al, 2013).…”

“…Previous studies using crayfish also successfully characterized EMG patterns in spontaneously initiated walking as different from those in mechanical stimulus-evoked walking (Chikamoto et al, 2008;Tomina et al, 2013). Those investigations revealed that a specific muscle of the walking leg was tonically activated prior to the onset of rhythmical stepping movements or bursting activity when the animal initiated walking spontaneously, and this pre-activation time was relatively shorter in the reflexive walking (Chikamoto et al, 2008;Tomina et al, 2013). The preceding activation of leg muscles prior to behavioral initiation of spontaneous walking can be interpreted as a revelation of central nervous mechanisms underlying initiation and control of stepping action.…”

“…The minimum Akaike information criterion (AIC) procedure was applied to the EMG data in order to find out the time onset of muscle activation objectively, as described previously (Chikamoto et al, 2008;Kagaya and Takahata, 2010;Tomina et al, 2013). We performed the procedure using R programming software (versions 2.15.1 and 3.02, R Development Core Team) and the TIMSAC package (version 1.2.7, Institute of Statistical Mathematics).…”