SUMMARY1. We recorded from 239 neurons located in the magnocellular division of the red nucleus of four alert macaque monkeys. At the same time, we recorded electromyographic (EMG) signals from as many as twenty electrodes chronically implanted on muscles of the shoulder, arm, forearm and hand. We recorded EMG signals for periods ranging from several months to a year.2. The monkeys were trained to perform three free-form food retrieval tasks, each of which activated all of the recorded muscles and most of the neurons. The 'prehension' task required simply that the monkey grasp a piece of food from a fixed point in space. The 'barrier' task required the monkey to reach around a small barrier to obtain the food, and the 'Kluver' task required that food be removed from small holes. During the prehension task, we found approximately equal numbers of neurons that were strongly active while the hand was being moved toward the target (70% of units), and while the food was being grasped (60%). Relatively few units were active as the hand was returned to the mouth (15%).3. Data files of 1-2 min duration were collected while the monkey performed a single behavioural task. Whenever possible, we recorded files for all three tasks from each neuron. For each file we calculated long time-span analog cross-correlations (± 1X28 s) between instantaneous neuronal firing rate and each of the full-wave rectified, low-pass filtered EMG signals. We used the peak correlation and the time of the peak as two summary measures of the functional relation between modulation of neuronal activity and EMG.4. The magnitude of the strongest correlations was between 0 4 and 0 5 (normalized to a perfect correlation of + 1X0). Distal muscles were the most frequently correlated, and extensors were more frequently correlated than flexors. For all monkeys, the lags for well correlated muscles were distributed broadly about L. E. MILLER AND OTHERS a uni-modal value near 0 ms. Eighty five per cent of the correlations larger than or equal to 0-25 had peaks between -150 and 200 ms.5. The activity of each neuron was represented in a muscle co-ordinate system by an n-dimensional 'functional linkage vector', each element of which was the peak correlation with one of n muscles. The vector for any given neuron points in a particular direction in muscle space, depending on the similarity between the activity of the neuron and the activity of each muscle. Sequential files recorded from a given neuron during a single behaviour yielded very similar linkage vectors, whereas the vectors for different neurons pointed in quite different directions in muscle space. The variation in linkage vectors for any given cell tested repeatedly during different behaviours was intermediate between that of the same cell-same task condition and the different cell-same task condition. Therefore, the correlation between the activity of the magnocellular red nucleus (RNm) neurons and limb muscles is not completely invariant for different tasks, but it varies less than for different RNm ...

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The sural artery and vein were used successfully as recipient vessels in nine patients who required free flap reconstruction about the knee. The anatomy of the sural vessels and the potential advantages of their use as free flap recipients are reviewed and discussed. Indications include popliteal vessels that are absent or severely damaged, as determined by preoperative angiography. No anastomotic complications were encountered in this series, indicating that the sural artery and vein can be used successfully as recipient vessels.

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Reconstructive microsurgery can be successfully applied to major defects of the lower back and posterior pelvis. When present, the superior and inferior gluteal vessels can be excellent free flap recipient vessels. However, if they are absent as a result of trauma or tumor ablation, a wrist carrier can be used to transfer large blocks of tissue in a staged procedure. Five patients are presented with challenging defects for which these techniques were used.

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Two case histories are presented in which cigarette smoking in the early postoperative period following digital replantation led to vasospasm and thus compromise of the microvascular anastomoses.