Journal of neurophysiology
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Comparative Study
Forms of forward quadrupedal locomotion. I. A comparison of posture, hindlimb kinematics, and motor patterns for normal and crouched walking.
1. Posture, hindlimb kinematics, and activity patterns of selected hindlimb muscles were compared for normal and crouched treadmill walking (0.5-0.6 m/s) for eight cats. To elicit crouched walking in which the trunk and head were lowered, cats were encouraged to walk under a light-weight Plexiglas ceiling suspended 17-20 cm above the treadmill belt. ⋯ Postural set during walking appears to be determined by brain stem and diencephalic centers, and the postural orientation of the cat may require adjustments in the motor program provided by spinal centers for the cat to walk. The role of posture and locomotion and the adjustments in hindlimb kinematics and EMG activity patterns have been studied for forward and backward walking in the cat and now for crouched walking on the treadmill. These data will assist us in understanding the role of posture, especially crouched posture, during other walking behaviors.
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Comparative Study
Changing directions of forthcoming arm movements: neuronal activity in the presupplementary and supplementary motor area of monkey cerebral cortex.
1. To understand roles played by two cortical motor areas, the presupplementary motor area (pre-SMA) and supplementary motor area (SMA), in changing planned movements voluntarily, cellular activity was examined in two monkeys (Macaca fuscata) trained to perform an arm-reaching task in which they were asked to press one of two target buttons (right or left) in three different task modes. 2. In the first mode (visual), monkeys were visually instructed to result and press either a right or left key in response to a forth coming trigger signal. ⋯ Neurons exhibiting the shift-related activity were distributed differentially among the two areas. In the pre-SMA, 31% of the neurons recorded showed the shift-related activity, whereas in the SMA, only 7% showed such an activity. These results suggest that pre-SMA and SMA play differential roles in updating the motor plans in accordance with current requirements.
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Comparative Study
Neuroprotection by propofol in acute mechanical injury: role of GABAergic inhibition.
1. Whole cell patch-clamp and extracellular field recordings were obtained from granule cells of the dentate gyrus in 400-microns-thick brain slices of the adult rat to determine the actions of the intravenous general anesthetic 2,6-diisopropylphenol (propofol) on acute neuronal survival and preservation of synaptic integrity after amputation of dendrites (dendrotomy), and to determine the role of gamma-aminobutyric acid-A (GABAA)-receptor-mediated inhibition in the neuroprotective effects of propofol. The actions of propofol were compared with those exerted by another widely used intravenous general anesthetic, 5-ethyl-5-[1-methylbutyl]-2-thiobarbituric acid (thiopental). 2. ⋯ The failure to rescue cells from dendrotomy-induced injury did not result from a decreased sensitivity of the GABAA receptors to the anesthetics, because the potentiating effects of the anesthetics on mIPSCs from control and dendrotomized neurons were not different. 7. These data indicate that propofol potentiates synaptic inhibition pre- and postsynaptically, and, when present during dendrotomy, it can protect neurons from acute mechanical-injury induced cell death via potentiation of GABAA receptor functions. However, propofol fails to provide neuroprotection against dendrotomy-induced changes in synaptic physiology.
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1. The locations and connections of the smooth and saccadic eye movement subregions of the frontal eye field (FEFsem and FEFsac, respectively) were investigated in seven hemispheres of five Cebus monkeys. The supplementary eye field was also mapped in seven hemispheres and the hand/arm regions of the dorsal and ventral premotor areas were localized in five hemispheres. ⋯ These results suggest that there may be similar, but relatively independent, parallel corticocortical networks to control pursuit and saccadic eye movements. The weak connections between the middle temporal area (MT) and FEF suggest that the MT may not provide the major source of visuomotion inputs to the FEF, but that it rather plays a role in mediating visual information that is relayed from the striate and extrastriate cortices via MT to the parietal cortex and then to the FEF. In addition to the well-known neural connections between the lateral intraparietal area and the FEF, additional parietal projections have been demonstrated from the dorsomedial visual area area specifically to the FEFsac and from area 7m specifically to the FEFsem.
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1. Whole cell patch-clamp recordings were obtained from identified cutaneous and muscle afferent neurons (33-60 microns diam) in dissociated L4 and L5 dorsal root ganglia (DRGs) from normal rats and from rats 2-3 wk after sciatic nerve ligation or crush injury. gamma-Aminobutyric acid (GABA)-induced conductance was compared in normal and injured neurons from both functional classes of sensory neurons. 2. Control cutaneous afferent neurons had a peak GABA-mediated conductance of 287 +/- 27 (SE) nS compared with 457 +/- 42 nS for control muscle afferent neurons. 3. ⋯ However, action potential waveform was not altered by crush injury, suggesting a differential regulation of these two properties in cutaneous afferent neurons. 6. These data indicate that injury-induced plasticity of GABAA-receptor-mediated conductance and action potential waveform occurs in cutaneous but not muscle afferent DRG neurons. It appears that peripherally derived influences are critical in maintaining the electrophysiological phenotype of cutaneous afferent neurons but not muscle afferent neurons.