Brain research
-
The present study examines the functional and anatomical underpinnings of egocentric and allocentric coding of spatial coordinates. For this purpose, we set up a functional magnet resonance imaging experiment using verbal descriptions of spatial relations either with respect to the listener (egocentric) or without any body-centered relations (allocentric) to induce the two different spatial coding strategies. We aimed to identify and distinguish the neuroanatomical correlates of egocentric and allocentric spatial coding without any possible influences by visual stimulation. ⋯ Furthermore, bilateral hippocampal involvement was observed during allocentric, but not during egocentric spatial processing. Our results demonstrate that the processing of egocentric spatial relations is mediated by medial superior-posterior areas, whereas allocentric spatial coding requires an additional involvement of right parietal cortex, the ventral visual stream and the hippocampal formation. These data suggest that a hierarchically organized processing system exists in which the egocentric spatial coding requires only a subsystem of the processing resources of the allocentric condition.
-
Transcutaneous electrical nerve stimulation (TENS) is a commonly utilized non-pharmacological, non-invasive treatment for pain. GABA is a neurotransmitter in the dorsal horn of the spinal cord that mediates analgesia locally, and also through activation of supraspinal sites. TENS reduces hyperalgesia through activation of receptor-mediated pathways at the level of the spinal cord, and supraspinally. ⋯ The increases in GABA do not occur in response to low frequency TENS, and there are no increases in glycine in response to low or high frequency TENS. However, the reduction in primary hyperalgesia by both high and low frequency TENS is prevented by spinal blockade of GABA(A) receptors with bicuculline. Thus, high frequency TENS increases release of GABA in the deep dorsal horn of the spinal cord, and both high and low frequency TENS reduce primary hyperalgesia by activation of GABA(A) receptors spinally.
-
Comparative Study
Cerebral blood flow and BOLD fMRI responses to hypoxia in awake and anesthetized rats.
This study investigated the functional MRI responses to graded hypoxia in awake/restrained and anesthetized animals by measuring cerebral blood flow (CBF) and blood oxygenation (BOLD) changes and estimating changes in cerebral metabolic rate of oxygen (CMRO2). Hypoxia in isoflurane anesthetized rats reduced blood pressure but did not change heart rate and respiration rate. In contrast, hypoxia in awake animals showed compensatory responses by sustaining blood pressure, increasing heart rate and respiration rate. ⋯ CMRO2 estimated using a biophysical BOLD model did not change under mild hypoxia but was reduced under severe hypoxia relative to baseline. These results showed that isoflurane attenuated autonomic responses to hypoxia, hypoxia-induced hypocapnia dominated CBF changes, tissues in awake conditions appeared better oxygenated, and severe hypoxia reduced oxygen metabolism. This study underscored the marked differences in BOLD and CBF MRI responses to hypoxia in vivo between awake and anesthetized conditions and has implications for functional MRI studies of hypoxia in anesthetized animal models.
-
The spinal cord is well known to undergo inflammatory reactions in response to traumatic injury. Activation and proliferation of microglial cells, with associated proinflammatory cytokines expression, plays an important role in the secondary damage following spinal cord injury. It is likely that microglial cells are at the center of injury cascade and are targets for treatments of CNS traumatic diseases. ⋯ In the olomoucine-treated group, a significant reduction of activated and/or proliferated microglial induced IL-1beta expression was observed 24 h after SCI. Moreover, olomoucine evidently attenuated the number of apoptotic neurons after SCI. Our findings suggest that modulation of microglial proliferation with associated proinflammatory cytokine expression may be a mechanism of cell cycle inhibition-mediated neuroprotections in the CNS trauma.
-
Spinal cord stimulation (SCS), also known as dorsal column stimulation, is a novel technique used widely in pain surgery. However, its effect on other pathologies such as epileptic disorders is unknown. The aim of this study is to evaluate the influence of electrical epidural stimulation of the upper cervical region on epileptic cortical discharges. ⋯ Spinal cord stimulation decreased penicillin-induced median values of epileptic discharges. Epileptic wave frequencies decreased significantly with increasing intensities of SCS. The results of this study suggest that SCS used for drug resistant epilepsies may be a viable alternative treatment modal.