Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale
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Visuospatial working memory mechanisms have been studied extensively at single cell level in the dorsolateral prefrontal cortex (PFCd) in nonhuman primates. Despite the importance of short-term memory of sound location for behavioral orientation, there are only a few studies on auditory spatial working memory. The purpose of this study was to investigate neuronal mechanisms underlying working memory processing of auditory and visual location information at single cell level in the PFCd. ⋯ Most neurons that were activated during the delay period were modality specific, responding either during visual or auditory trials. All bimodal delay related neurons that responded during both visual and auditory trials were spatially nonselective. The results of the present study suggest that in addition to the modality specific parallel mechanism, working memory of auditory and visual space also involves modality independent processing at cellular level in the PFCd.
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Randomized Controlled Trial
Effects of local anesthetics on somatosensory function in the temporomandibular joint area.
There is a need for systematic studies regarding the pathophysiology and pain mechanisms of somatosensory function in the temporomandibular joint (TMJ). So far, the effects on somatosensory functions of local anesthetics (LA) applied to the auriculotemporal (AT) nerve or intraarticularly (IA) into the TMJ have not been studied systemically. This study aimed to examine in a double-blinded, placebo-controlled manner the effects of LA on mechanical and thermal sensitivity in the TMJ area. ⋯ No other measures showed a significant change after the injections. Our results showed that IA bupivacaine injection in healthy subjects has no effect on the sensitivity of the TMJ or surrounding area, while AT nerve block has a more pronounced effect on deep mechanical, but not on superficial mechanical or thermal sensitivity. Further research to investigate the effect of LA on somatosensory functions in TMJ patients in comparison with this study results will give valuable information about the sensitivity in the TMJ area.
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We investigated the speed-accuracy trade-off in a task of pointing with the big toe of the right foot by a standing person that was designed to accentuate the importance of postural adjustments. This was done to test two hypotheses: (1) movement time during foot pointing will scale linearly with ID during target width changes, but the scaling will differ across movement distances; and (2) variations in movement time will be reflected in postural preparations to foot motion. Ten healthy adults stood on the force plate and were instructed to point with the big toe of the right foot at a target (with widths varying from 2 to 10 cm) placed on the floor in front of the subject at a distance varying from 10 to 100 cm. ⋯ We conclude that the speed-accuracy trade-off in a task with postural adjustments originates at the level of movement planning. The different dependences of movement time on D and W may be related to spontaneous postural sway (migration of the point of application of the resultant force acting on the body of the standing person). The results may have practical implications for posture and gait rehabilitation techniques that use modifications of stepping accuracy.
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Reaching to grasp an object of interest requires a complex sensorimotor transformation-involving eye, head, hand, and postural systems. We show here that discontinuities in development of movement in these systems are dependent not only on age but also vary according to task constraints. Providing external postural support allows us to examine the differential influences of the eye on the hand and the hand on the eye as the ability to isolate and coordinate each system changes with age. ⋯ Postural support had differential effects on the processes of initiation and execution of eye-hand movements. The addition of postural support decreased the time needed for planning the movement, especially in the youngest children, and contributed to increased speed of isolated movements, whereas it caused differential slowing of coordinated movements depending on the child's developmental level. We suggest that the complexity of the results reflects the complexity of changing task requirements as children transition from simpler ballistic control of all systems to flexible, independent but coordinated control of multiple systems.
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Placebo analgesia involves complex mechanisms and sometimes has a marked effect on patients in pain. In this study we examined changes in regional cerebral blood flow (rCBF) under three different conditions (resting, hot, painful) before and after placebo administration using H(2)(15)O and positron emission tomography in ten healthy subjects. ⋯ However, there was no rCBF change under the rest condition in the placebo nonresponders after placebo administration. These results suggest that placebo analgesia has its effect under the resting condition and MPFC, IPL and PPC may have an important role in placebo analgesia.