Small signal influences upon a sawtooth oscillator.
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Biomedical Engineering↗
Biomedical subjects
P Boon
Publications and source records attributed to P Boon.
Language activation distributions revealed by fMRI in post-operative epilepsy patients: differences between left- and right-sided resections.
OBJECTIVE: To reveal differences of cerebral activation related to language functions in post-operative temporal lobe epilepsy (TLE) patients. METHODS: Right (RTL) and left temporal lobe (LTL) resected patients, and healthy controls were studied using functional magnetic resonance imaging (fMRI). Only patients with complete left-hemispheric language dominance according to the intracarotid amytal procedure (IAP) were included. Language-related activations were evoked by performing word generation and text reading language tasks. Activation lateralization and temporo-frontal distribution effects were analysed. RESULTS: For word generation, only LTL patients showed reduced left lateralized activation compared to controls, due to a decrease in activation in the left prefrontal cortex and an increase in the right prefrontal cortex. For reading, the left-hemispheric lateralization in RTL patients increased because of enhanced activity in the left prefrontal cortex, whereas for LTL patients the activation became bilaterally distributed over the temporal lobes. Lateralization results between pre-operative IAP and post-operative fMRI were highly discordant. Significant temporo-frontal distribution changes manifested from the reading but not from the word generation task. CONCLUSION: The cerebral language representation in post-operative LTL epilepsy patients is more bi-hemispherically lateralized than in controls and RTL patients. Post-operative temporo-frontal and interhemispheric redistribution effects, involving contralateral homologous brain areas, are suggested to contribute to the cerebral reorganisation of language function.
Adult↗
Effect of photoperiod on body weight gain, and daily energy intake and energy expenditure in Japanese quail (Coturnix c. japonica).
Effect of photoperiod and food duration on body weight gain, energy intake, energy expenditure, and sexual development were investigated in two strains of Japanese quail (Coturnix c. japonica), bred for meat (broilers) or egg production (layers), from 7 to 71 days of age. In a first experiment chicks were subjected to 18L:6D, 15L:9D, 12L:12D, 9L:15D, or 6L:18D, with ad lib food during the light period. In a second experiment birds were exposed to a long photoperiod (18L:6D or 15L:9D) with ad lib food during part of the light period (first 6 or 9 h, respectively). Longer photoperiods were associated with larger weight gains. In 18L:6D broilers total body weight gain was 262 g compared to 213 g in 6L:18D broilers. In layers, corresponding values were 182 and 131 g. This effect of photoperiod on weight gain was primarily due to the effect of photoperiod on food availability. The photoperiod below which detrimental effects on weight gain occurred was 9L:15D for both strains. Chicks subjected to 9L:15D or 6L:18D exploited crop filling to enhance energy intake. They also decreased nocturnal metabolic rates to a greater extent compared to levels during the light phase than chicks subjected to light periods of 12 h or more. Sexual maturation was stimulated by photoperiod. At the age of 71 days, eight out of nine females subjected to 18L:6D were producing eggs, but none of the 6L:18D females. It is concluded that changes in feeding behavior and energy expenditure shown under short photoperiods are part of a strategy that allow chicks to gain weight continuously.
Animals↗
An MR protocol for presurgical evaluation of patients with complex partial seizures of temporal lobe origin.
PURPOSE: To find an optimal diagnostic protocol for the presurgical MR evaluation of patients with temporal lobe epilepsy. METHODS: MR imaging in 14 healthy subjects and 25 consecutive patients with temporal lobe epilepsy was performed in paracoronal sections perpendicular to the hippocampi with T1-weighted inversion recovery and T2 weighting. Volume measurements of the hippocampus/amygdala complex were performed and a multiecho sequence yielded T2-calculated images. RESULTS: Hippocampal disease was seen in 22 of 25 temporal lobe epilepsy patients on paracoronal T1-weighted inversion recovery images. Four had bilateral abnormalities. Characteristic for hippocampal disease were features such as volume loss, decreased signal, and loss of internal morphology. Only 17 of 25 patients demonstrated hippocampal pathology on T2-weighted images, and in one patient this was bilateral. Patients with only minimal structural loss on T1-weighted inversion recovery had normal T2-weighted images. T2 calculation was no more sensitive than visual assessment on the T2-weighted images. Volume measurements were normal in one patient and misleading in two patients. Lateralization, as compared with clinical and electroencephalographic findings, was most confidently done with paracoronal T1-weighted inversion recovery images and volume measurements. CONCLUSIONS: An optimum MR protocol for temporal lobe epilepsy patients is proposed. Its essential feature is that the hippocampus be evaluated by paracoronal T1-weighted inversion recovery images and volume measurements. T2-weighted imaging can be omitted.
Adolescent↗
Value of single-voxel proton MR spectroscopy in temporal lobe epilepsy.
PURPOSE: To study the value of different parameters derived from single-voxel proton MR spectroscopy of the mesial temporal lobes in the lateralization of the epileptogenic zone in patients with temporal lobe epilepsy. METHODS: We studied 12 healthy volunteers and 21 patients with temporal lobe epilepsy refractory to medical treatment, which was clearly lateralized with electroencephalography (EEG) and MR imaging. The mesial temporal lobes were investigated with single-voxel proton MR spectroscopy using a point-resolved spectroscopic sequence with an echo time of 135 milliseconds. The normalized concentration of N-acetylaspartate (NAA), creatine (Cr), and choline-containing compounds (Cho), and the metabolite ratios NAA/Cho+Cr, NAA/Cr, Cho/Cr, and NAA/Cho were calculated from the spectra. Using these values and an asymmetry index, we assigned the patients to one of five lateralization categories. RESULTS: The most consistent MR spectroscopic parameter for clear lateralization was the NAA/Cho+Cr ratio, followed by the NAA ratio. But with an adequate asymmetry index, the epilepsy in 17 (81%) of 21 patients could be lateralized by EEG and MR imaging with both parameters concordantly. Symmetric bilateral abnormalities were found in four of the 21 patients with NAA/Cho+Cr and in only one of the 21 patients with NAA. With both parameters, no contradictory lateralization was found; however, this was indeed the case with the remaining ratios, NAA/Cr, Cho/Cr, and NAA/Cho, in two, three, and one of the patients, respectively. A statistically significant decrease in NAA was found on the epileptic side, but also on the contralateral side. CONCLUSION: With an adequate asymmetry index, NAA/Cho+Cr and NAA are equally sensitive in predicting the side of involvement in patients with unilateral temporal lobe epilepsy.
Adolescent↗