TY - JOUR T1 - Diurnal H-reflex variation in mice. JF - Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale Y1 - 2006 A1 - Jonathan S. Carp A1 - Tennissen, Ann M. A1 - Xiang Yang Chen A1 - Jonathan Wolpaw KW - circadian rhythm KW - Electromyography KW - implanted electrodes KW - Monosynaptic KW - Reflex KW - Spinal Cord AB - Mice exhibit diurnal variation in complex motor behaviors, but little is known about diurnal variation in simple spinally mediated functions. This study describes diurnal variation in the H-reflex (HR), a wholly spinal and largely monosynaptic reflex. Six mice were implanted with tibial nerve cuff electrodes and electrodes in the soleus and gastrocnemius muscles, for recording of ongoing and nerve-evoked electromyographic activity (EMG). Stimulation and recording were under computer control 24 h/day. During a 10-day recording period, HR amplitude varied throughout the day, usually being larger in the dark than in the light. This diurnal HR variation could not be attributed solely to differences in the net ongoing level of descending and segmental excitation to the spinal cord or stimulus intensity. HRs were larger in the dark than in the light even after restricting the evoked responses to subsets of trials having similar ongoing EMG and M-responses. The diurnal variation in the HR was out of phase with that reported previously for rats, but was in phase with that observed in monkeys. These data, supported by those in other species, suggest that the supraspinal control of the excitability of the HR pathway varies throughout the day in a species-specific pattern. This variation should be taken into account in experimental and clinical studies of spinal reflexes recorded at different times of day. VL - 168 UR - http://www.ncbi.nlm.nih.gov/pubmed/16151781 ER - TY - JOUR T1 - Long-term spinal reflex studies in awake behaving mice. JF - Journal of neuroscience methods Y1 - 2005 A1 - Jonathan S. Carp A1 - Tennissen, Ann M. A1 - Xiang Yang Chen A1 - Gerwin Schalk A1 - Jonathan Wolpaw KW - Electromyography KW - implanted electrodes KW - Monosynaptic KW - Spinal Cord AB - The increasing availability of genetic variants of mice has facilitated studies of the roles of specific molecules in specific behaviors. The contributions of such studies could be strengthened and extended by correlation with detailed information on the patterns of motor commands throughout the course of specific behaviors in freely moving animals. Previously reported methodologies for long-term recording of electromyographic activity (EMG) in mice using implanted electrodes were designed for intermittent, but not continuous operation. This report describes the fabrication, implantation, and utilization of fine wire electrodes for continuous long-term recordings of spontaneous and nerve-evoked EMG in mice. Six mice were implanted with a tibial nerve cuff electrode and EMG electrodes in soleus and gastrocnemius muscles. Wires exited through a skin button and traveled through an armored cable to an electrical commutator. In mice implanted for 59-144 days, ongoing EMG was monitored continuously (i.e., 24 h/day, 7 days/week) by computer for 18-92 days (total intermittent recording for 25-130 days). When the ongoing EMG criteria were met, the computer applied the nerve stimulus, recorded the evoked EMG response, and determined the size of the M-response (MR) and the H-reflex (HR). It continually adjusted stimulation intensity to maintain a stable MR size. Stable recordings of ongoing EMG, MR, and HR were obtained typically 3 weeks after implantation. This study demonstrates the feasibility of long-term continuous EMG recordings in mice for addressing a variety of neurophysiological and behavioral issues. VL - 149 UR - http://www.ncbi.nlm.nih.gov/pubmed/16026848 ER -