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The telemetered electromyographic activity (EMG) of select hindlimb muscles of unrestrained cats during standing, walking, trotting, and galloping have been recorded. Simultaneous cinematographic records permitted close correlation of muscle activity and locomotor behavior. In general, the pattern of extensor activity of the ankle, knee, and hip during locomotion is fairly consistent, while that of the flexors is more variable.Changes in basic EMG patterns from walk, to trot, t o gallop are most evident in the two-jointed muscles associated with the knee and hip. Progressively greater variation of activity onset and cessation can be seen among extensor muscle groups from the walk, to trot, to gallop. Co-activation of the joint extensors and flexors, especially of the hip, a t the end of the stance phase (E3) is slight in the walk, moderate in the trot, and considerable in the gallop. These EMG changes are necessary to meet the demands imposed upon the musculature a t the faster gaits, particularly galloping, which include limb rigidity as related t o loading, momentum as related to the limb's directional change from the stance phase to the swing phase, and lower spinal movements.The peroneal muscles of the ankle and the gluteal muscles of the hip show extensor activity and act as joint stabilizers during locomotion. Both biceps femoris anterior muscle and biceps femoris posterior muscle show consistent hip extensor patterns a t all gaits. During quiet standing, extensor activity about the knee, ankle, and metatarsophalangeal joints is evident; but the hip extensor and flexor musculature is remarkably silent.EMG data for unrestrained cats are compared t o those of dogs on a treadmill (Tokuriki, '73a,b, '74; Wentink, '76) and those recorded fromdecerebrate cats (mesencephalic preparation) during controlled locomotion (Gambaryan et al., '71). The EMG patterns from decerebrate cats are more consistent at the walk and gallop within functional groups of muscles a t the ankle, knee, and hip than the EMG patterns observed in unrestrained cats or animals moving on a treadmill. Muscular contraction produces the force by which animals position and rhythmically move their limbs. This simple idea becomes complicated when one considers the number of muscles in each limb, and the coordination of force and timing of muscular contraction necessary to produce a smooth locomotor act. The nervous system directs this coordination, and electromyograms (EMGs) record the resulting electrical activity of the muscles.Engberg ('64) study the activity of hindlimb muscles in cats during unrestrained locomotion. This excellent study resulted in data that have been used for several years in interpreting the demands imposed on the nervous system to direct peripheral events in locomotion. The present study, designed to compliment and expand that work, presents averaged EMGs from select hindlimb muscles of unrestrained cats during standing, walking, trotting, and gal-'

individuals experience barriers to accessing many types of health care in the United States, resulting in substantial health care disparities. To improve health care in this patient population, it is important to recognize and study the potential factors limiting access to care. OBJECTIVE To examine deep brain stimulation (DBS) use in Parkinson disease (PD) to determine which factors, among a variety of demographic, clinical, and socioeconomic variables, drive DBS use in the United States. DESIGN, SETTING, AND PARTICIPANTS We queried the Nationwide Inpatient Sample in combination with neurologist and neurological surgeon countywide density data from the Area Resource File. We used International Classification of Diseases, Ninth Revision codes to identify discharges of patients at multicenter, all-payer, nonfederal hospitals in the United States diagnosed with PD (code 332.0) who were admitted for implantation of intracranial neurostimulator lead(s) (code 02.39), DBS. MAIN OUTCOMES AND MEASURES We analyzed factors predicting DBS use in PD using a hierarchical logistic regression analysis including patient and hospital characteristics. Patient characteristics included age, sex, comorbidity score, race, income quartile of zip code, and insurance type. Hospital characteristics included teaching status, size, regional location, urban vs rural setting, experience with DBS discharges, year, and countywide density of neurologists and neurological surgeons. RESULTS Query of the Nationwide Inpatient Sample yielded 2 408 302 PD discharges from 2002 to 2009; 18 312 of these discharges were for DBS. Notably, 4.7% of all PD discharges were African American, while only 0.1% of DBS for PD discharges were African American. A number of factors in the hierarchical multivariate analysis predicted DBS use including younger age, male sex, increasing income quartile of patient zip code, large hospitals, teaching hospitals, urban setting, hospitals with higher number of annual discharges for PD, and increased countywide density of neurologists (P < .05). Predictors of nonuse included African American race (P < .001), Medicaid use (P < .001), and increasing comorbidity score (P < .001). Countywide density of neurological surgeons and Hispanic ethnicity were not significant predictors. CONCLUSIONS AND RELEVANCE Despite the fact that African American patients are more often discharged from hospitals with characteristics predicting DBS use (ie, urban teaching hospitals in areas with a higher than average density of neurologists), these patients received disproportionately fewer DBS procedures compared with their non-African American counterparts. Increased reliance on Medicaid in the African American population may predispose to the DBS use disparity. Various other factors may be responsible, including disparities in access to care, cultural biases or beliefs, and/or socioeconomic status.