PubMed · 4831421
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
K R Smith. 1974. Letter: Lower extremity monoparesis.. https://pubmed.ncbi.nlm.nih.gov/4831421/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
We performed blood oxygenation level-dependent (BOLD) functional MR imaging in 11 children younger than 5 y of age and 10 children older than 5 y of age. All but five of the children in the older age group were tested under light anesthesia. We examined the cerebral oxidative metabolism (CMRO(2)) associated with the processing of a flashed and a reversing checkerboard stimulus. These stimuli had been shown in a previous study to induce identical vascular responses. The reversing checkerboard activated twice the neuronal population of the flashed checkerboard, doubling the CMRO(2) associated with it. We compared the extent of activation for the positive BOLD response and found that it did not differ between the different age groups. We estimated the oxidative metabolism by examining the change in the local deoxyhemoglobin (HbR) concentration using Delta R2*. Because both stimuli induced the same vascular response, any increase in oxygen requirement would have to be met by the identical blood volume. Increasing CMRO(2) will therefore result in an increase in the oxygen extraction fraction (OEF), which raises the local HbR concentration. In the younger children, both checkerboard stimuli produced identical, high HbR concentrations. In the older children, the HbR concentration to the flashed stimulus was significantly lower than to the reversing stimulus. We conclude that, for identical stimuli, the oxidative energy requirement associated with the cortical processing is higher in young children than in older children because the presence of superfluous synaptic connections in the immature visual system activates a larger neuronal population.
After aneurysmal subarachnoid haemorrhage (SAH), the clinical outcome depends upon the primary haemorrhage and a number of secondary insults in the acute post-haemorrhagic period. Some secondary insults are potentially preventable but prevention requires prompt recognition of cerebral or systemic complications. Currently, several neuro-monitoring techniques are available; this review describes the most frequently used techniques and discusses indications for their use, and their value in diagnosis and prognosis. None of the techniques, when considered in isolation, has proved sufficient after SAH. Furthermore, the use of multi-modality monitoring is hampered by a lack of clinical studies that identify combinations of specific techniques in terms of clinical information and reliability. However, ischaemia at the tissue level can be detected by intracerebral microdialysis technique. Used together with the conventional monitoring systems, for example intracranial pressure measurements, transcranial Doppler ultrasound and modern neuro-imaging, direct assessment of biochemical markers by intracerebral microdialysis is promising in the advancement of neurointensive care of patients with SAH. A successfully implemented monitoring system provides answers but it also raises valuable new questions challenging our current understanding of the brain injury after SAH.
BACKGROUND: Signal detection by one sense selectively activates other relevant systems. For example, when an auditory stimulus comes from a specific location, visual sensitivity, tactile sensitivity, and motor readiness increase for stimuli or actions in that direction. This observed phenomenon provides an apparent sensory-sensory and sensory-motor coordination with evolutionary adaptive advantages. Anatomically, many of the relevant cortical sites are adjacent to each other. MATERIAL/METHODS: The spread of excitation from an active processing site in the cortex to nearby functions can be seen in brain scans. Cognitive and affective functions also selectively activate each other and are activated by focal sensory stimulation based on cortical proximity. These behavioral interactions seem to offer no selective adaptability but still call for a model of possible mediation. The objective of the current paper is to consider evidence for competing mechanisms for the flow of cortical activation that are characterized by being neurobiologically feasible, showing preferential activation over short distances, and having empirical support. RESULTS: These three criteria are met by blood flow, heat flow, nearest networks, electromagnetism, and inhibition. CONCLUSIONS: It is suggested that several of these mechanisms work independently or synergetically to produce the known interactions among attention, affect, cognition, and behavior. An understanding of these processes and the functional cerebral space in which they operate can suggest practical applications for the manipulation of behavior.