Unconscious activation of visual cortex in the damaged right hemisphere of a parietal patient with extinction.
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Visual extinction is a sign classically associated with right parietal damage. The patient can see a single stimulus presented in the ipsilesional or contralesional visual field, but is characteristically unaware of the same contralesional stimulus during simultaneous stimulation of both fields. The ipsilesional stimulus is said to 'extinguish' the contralesional stimulus from awareness during bilateral stimulation, perhaps due to a pathological bias in attention towards the ipsilesional side. Recent psychophysical evidence suggests that, although extinguished stimuli are not consciously seen, they may undergo residual processing and exert implicit effects on performance. However, the neural structures mediating such residual processing for extinguished stimuli remain unknown. Here we studied the neural activity evoked by an extinguished visual stimulus, using event-related functional MRI (fMRI), in a patient with circumscribed right inferior parietal damage and profound left-sided extinction. Monochrome objects (faces or houses) were presented in the left or right field, either unilaterally or bilaterally on each trial, with the patient indicating by button press whether he saw an object on the left, the right or on both sides. He usually saw only the right object on bilateral trials, yet the fMRI data showed activation of visual cortex contralateral to the extinguished left stimulus on these trials (compared with right-only stimulation), in both striate and early extrastriate areas of the right hemisphere. This activity had a similar location and time-course to that resulting from a single stimulus in the left versus right visual field. Cortical pathways involved in the normal processing of a single seen stimulus can thus still be activated by an unseen, extinguished stimulus after right parietal damage. Comparison of fMRI responses for faces versus houses revealed some category-specific activation for extinguished stimuli in right fusiform regions, but only at low statistical threshold. These results are discussed in terms of theoretical accounts for parietal extinction and, more generally, for the neural substrates of visual awareness. (+info)
Effect of the size of the deletion and clinical manifestation in Wolf-Hirschhorn syndrome: analysis of 13 patients with a de novo deletion.
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We performed clinical, cytogenetic, and molecular analyses on 13 patients (8 females and 5 males, aged 6 months to 13 years) with Wolf-Hirschhorn syndrome due to de novo deletions of chromosome 4p. All patients presented with the typical facial gestalt, microcephaly, and profound mental retardation. Other clinical signs were low birth weight (10/13; 77%), postnatal short stature (8/12; 66%), muscular hypotonia (12/13; 92%), seizures (11/13; 85%), congenital heart defects (4/13; 31%), colobomata of iris (4/12; 33%), genital anomalies (4/13; 31%), deafness (3/13; 23%), and renal anomalies (3/13; 23%). The smallest deletion was a submicroscopic terminal deletion of nearly 2.5 Mb. The largest was a terminal deletion of nearly 30 Mb. Cleft lip/palate, preauricular pits/tags, and congenital heart defects were present only in patients with terminal deletions larger than 10 Mb. The deviations from mean birth weight, birth length, and postnatal head circumference correlated with the size of the deletion. Determining the parental origin of the deletion with microsatellite markers, the maternal allele was missing in three patients and the paternal allele in eight patients. Our observations support the existence of a partial genotype-phenotype correlation in Wolf-Hirschhorn syndrome. (+info)
Complicated emergent endovascular repair of a life-threatening bilateral internal jugular vein occlusion.
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A 62-year-old woman had painful facial swelling that progressed to extensive periorbital and perioral edema with loss of vision, hearing, and consciousness. Her past surgical history was significant for right radical neck dissection including internal jugular vein (IJV) resection, laryngectomy, partial esophagectomy, tracheoesophageal fistula repair, and tracheostomy for squamous cell carcinoma of the oropharynx. In addition, the patient had received radiation therapy to the neck. A venogram revealed occlusion of the left IJV. A guidewire from the femoral vein was passed through the occluded segment; however, attempts to introduce an angioplasty balloon failed. A percutaneous basilic vein approach allowed passage of a dilator sheath over a guidewire, thereby enabling Wallstent deployment across the IJV occlusion. A second Wallstent was inserted across a stenosis in the brachiocephalic vein; however, this second stent reoccluded the IJV. Surgical removal of the second Wallstent was required through a segmental claviculectomy and venotomy. Patency was restored in the IJV and the brachiocephalic vein with the return of baseline neurologic function. This case demonstrates a complicated emergent endovascular repair of a life-threatening IJV occlusion that required surgical salvage. (+info)
Effects of a three-dimensional bimetric maxillary distalizing arch.
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This study aimed to investigate the dental effects of a three-dimensional (3D) bimetric maxillary distalizing arch. The Wilson rapid molar distalization appliance for Class II molar correction was used in 14 patients (10 girls and four boys with a mean age of 12.18 years). The open coil springs were activated with bent Omega stops and Class II intermaxillary elastics. The mandibular anchorage was gained by a 0.016 x 0.016 utility arch with a 3D lingual arch or a lip bumper with a standard lingual arch. The lateral cephalograms taken before and after treatment formed the material of the research. A Wilcoxon test was used to statistically evaluate the treatment effects. The results showed that the distal tipping of the maxillary first and second molars, and first and second premolars and canines were statistically significant. Significant distal movement occurred in all posterior and canine teeth. The maxillary first molar distalization was found to be 3.5 mm. The maxillary incisor showed significant proclination and protrusion. The decrease in overbite was found to be statistically significant. The mandibular plane angle significantly increased by a mean of 0.5 mm. In addition, significant soft tissue changes were observed. (+info)
A comparison of health state utilities for dentofacial deformity as derived from patients and members of the general public.
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The cost-utility approach is a method of economic evaluation, which assigns a ratio of cost to benefit, based on utility values of the health state in question. It allows efficient use of health care resources and is a useful method in that it permits comparison of a wide range of medical interventions, including those which are life saving and those that improve quality of life. This study obtained utility values for dentofacial deformity from orthognathic patients and members of the general public using three recognized methods--rating scale (RS), standard gamble (SG), and time trade-off (TTO). There were no significant differences between the utility values for the two groups of respondents. Method agreement between the TTO and the SG (the 'gold standard') was better than that between the RS and SG. In addition, the SG and TTO were found to have greater repeatability than the RS. (+info)
Functional MRI at 1.5 tesla: a comparison of the blood oxygenation level-dependent signal and electrophysiology.
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How well does the functional MRI (fMRI) signal reflect underlying electrophysiology? Despite the ubiquity of the technique, this question has yet to be adequately answered. Therefore, we have compared cortical maps generated based on the indirect blood oxygenation level-dependent signal of fMRI with maps from microelectrode recording techniques, which directly measure neural activity. Identical somatosensory stimuli were used in both sets of experiments in the same anesthetized macaque monkeys. Our results demonstrate that fMRI can be used to determine the topographic organization of cortical fields with 55% concordance to electrophysiological maps. The variance in the location of fMRI activation was greatest in the plane perpendicular to local vessels. An appreciation of the limitations of fMRI improves our ability to use it effectively to study cortical organization. (+info)
The effect of contrast and size scaling on face perception in foveal and extrafoveal vision.
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PURPOSE: To determine whether face perception can be equalized across the visual field by scaling size and contrast simultaneously. METHODS: Contrast sensitivities were measured for detection (N = 1) and identification (N = 2-8) of a target face as a function of size (0.4 degrees-10 degrees) across eccentricities (E = 0 degrees-10 degrees). RESULTS: In all conditions contrast sensitivity first increased and then saturated, as a function of stimulus size. Maximum sensitivity (Smax) decreased, whereas critical size (where S = Smax/square root(2)) increased with eccentricity and set size (N). At each set size, sensitivities from all eccentricities could be equated by double scaling--i.e., translation in horizontal (size) and vertical (contrast) dimensions on log-log axes. Similarly, at each eccentricity, data from all set sizes could be superimposed using double scaling. Furthermore, all data could be superimposed onto the foveal detection curve when double scaled according to the equation F = 1 + E/E2i + logN/logN2i + E(logN)/K, where i is horizontal or vertical. This equation incorporates the eccentricity (E2) and set size (N2), where contrast and size double, as well as the interaction term (K). CONCLUSIONS: Double scaling superimposes data. Not only is this possible across set sizes or eccentricities separately, but by combining their effects, a function is provided that collapses all data to a single curve, explaining all performance variation across eccentricity and set size. Our results support the proposition based on numeral recognition that failures of spatial scaling across eccentricities may simply reflect the need for scaling both size and contrast. (+info)
B-Cell deficiency predisposes mice to disseminating anaerobic infections: protection by passive antibody transfer.
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We have previously demonstrated that a high proportion of RAG-2 SCID knockout mice, which lack T and B cells, develop orofacial abscesses and disseminated infections following pulpal infection, whereas immunocompetent control mice do not. In the present study, we sought to identify the components of the adaptive immune response which contribute to protection against disseminating anaerobic infections and sepsis. For this purpose, various genetically engineered immunodeficient mice were employed, including RAG-2 SCID, Igh-6 (B-cell deficient), Tcrb Tcrd (T-cell deficient) and Hc(0) (C5 deficient). For abscess induction, the mandibular first molars were subjected to pulp exposure on day 0. Teeth were infected with a mixture of four anaerobic pathogens, including Prevotella intermedia, Streptococcus intermedius, Fusobacterium nucleatum, and Peptostreptococcus micros, and teeth were sealed to prevent communication with the oral cavity. The findings demonstrate that both RAG-2 SCID and B-cell-deficient mice, but not T-cell- or C5-deficient mice, have increased susceptibility to the development of disseminating anaerobic infections. Abscess-susceptible RAG-2 SCID and B-cell-deficient mice also showed a significant loss of body weight, splenomegaly, and absent antibacterial antibody production. Furthermore, dissemination was significantly reduced, from 74 to 25%, in susceptible RAG-2 mice by passively transferred antibody, predominantly immunoglobulin G2b (IgG2b) and IgM, against the infecting bacterial innoculum. Fractionated IgG-enriched preparations were more efficient in transferring protection than IgM preparations. We conclude that an antibody-mediated mechanism(s), most likely bacterial opsonization, is of importance in localizing anaerobic root canal infections and in preventing their systemic spread. (+info)