Visual and auditory intrusion errors in short-term memory.
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Biomedical subjects
Publications and source records attributed to G J Harris.
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Dynamic susceptibility contrast (DSC) MRI is an alternative to positron emission tomography (PET) and single photon emission computed tomography (SPECT) for the evaluation of cerebral hemodynamics in patients with Alzheimer's disease. DSC MRI allows the construction of high resolution images of cerebral blood volume (CBV) without the use of radionuclides or ionizing radiation. In this study, DSC MRI data were collected from 16 patients with probable Alzheimer's disease and 16 age-matched control subjects. Characteristic patterns of regional CBV variation were found using principal component analysis. Three such patterns were identified: a global variation pattern, an anterior-to-posterior CBV gradient, and a temporoparietal pattern. Group differences in the principal component scores associated with the global and temporoparietal patterns (P = .08 and P = .007, respectively) suggest that these deficits reflect characteristic CBV abnormalities in Alzheimer's disease. Using only these two scores, the Alzheimer's disease group was classified with a sensitivity of 81% and a specificity of 88%. Additionally, disease severity, as measured by the Mini-Mental State Examination (MMSE), was correlated significantly with the third principal component score (Pearson's r = .50, P = .05).
Although granular cell tumor (GCT) has been a distinct pathological entity since 1926, confusion and controversy have long existed regarding the nature and histogenesis of the tumor. Twenty-five cases of granular cell tumor involving the orbit and ocular adnexae previously reported in the ophthalmic literature, are reviewed and six additional cases are reported. The histopathological and immunohistochemical characteristics of granular cell tumors in this uncommon location are discussed and their probable origin from Schwann cells is also considered.
The safety of metrizamide in the optic nerve sheath has not been studied to our knowledge. We studied histologic changes produced by metrizamide in the optic nerve of cats with surgically created lesions simulating orbital tumors and trauma. Displacement, compression, and disruption of the optic nerve sheath were detectable by radiographing the opacified sheath. Arachnoiditis of the optic nerve sheath is unlikely from a single exposure to metrizamide in a concentration less than 300mg I/ml.
The diagnosis of central venous catheter-related sepsis depends on a positive culture obtained from the distal intravascular portion of the catheter. The effects of the subcutaneous tunnel and the skin exit site on the accuracy of cultures obtained from the catheter are unknown. We have developed an in vitro model to study the effect of these variables. By inoculating polyethylene catheters embedded in agar with Pseudomonas aeruginosa, we were able to show that: (1) capillary action occurs along catheters in an agar tunnel, (2) organisms that are growing on the distal segment (tip) of the catheter can be dislodged from the surface of the catheter when it is pulled through the agar tunnel, and (3) pulling a catheter through a contaminated area results in distal contamination.
A 2-month-old female infant underwent intralesional corticosteroid injection for a capillary hemangioma that was causing amblyopia of the right eye from ptosis, globe displacement, and astigmatism. Forty-eight hours after the injection, the infant's parents noted that she was visually inattentive. On examination, she could not fixate or follow with either eye, and an afferent pupillary defect was present in the left eye. Ophthalmoscopy showed scattered areas of intraretinal hemorrhage in the right eye and extensive preretinal and intraretinal hemorrhages in the left eye. Ten months after injection, the hemangioma had greatly regressed, and visual acuity in the right eye was felt to be normal. The left eye had unsteady fixation with a persistent afferent pupillary defect and macular scarring. Retrograde flow of the corticosteroid suspension through the hemangioma's feeder vessels, probably originating from both ophthalmic arteries, is the most likely explanation for this complication.
This paper considers the opportunities for noise control within the route corridor required for construction of road, rail and other guided transport schemes. It deals with control of noise generation at source, and in the transmission path close to the point of generation. In this way it is possible to control the amount of acoustic power generated, and to absorb part of the radiated power at points of reflection. Purely reflective wayside barriers do little to absorb acoustic energy, merely reflecting it in a different direction. Whilst this has selfish benefits to the receptor in the shadow zone of the barrier, it makes things worse for others on the reflective side of the geometry. The paper therefore considers the options available to the engineer in the design of rolling and sliding interfaces and the use of acoustically absorptive finishes on all surfaces close to the point of noise generation. This includes the running surface itself, structural components, retaining walls, over and under passes, and the inner surfaces of track and wayside barriers.
Optic nerve sheath meningiomas and optic nerve gliomas can be difficult to differentiate by computed tomography (CT). Three patients with optic nerve sheath meningiomas were studied with a CT/T 8800 scanner with 1.5-mm-thick axial sections and intravenous contrast material. In each case, an abnormal optic nerve sheath was identified by CT. A soft-tissue mass arose from one side of the sheath in one patient, and the entire sheath was enlarged in two patients. This provides a basis for distinguishing optic nerve sheath meningioma from optic nerve glioma.
Arteriovenous malformations (AVMs) of the orbit are progressively enlarging communications between arteries and veins that bypass normal capillary beds. In contrast to arteriovenous fistulas (AVFs), AVMs are congenital lesions with multiple large feeding arteries, a central nidus, and numerous dilated draining veins. Management of AVMs of the orbit may be difficult due to the threat of hemorrhage, vascular occlusion during treatment, and collateral damage to surrounding organs. We managed AVM of the orbit and periorbital tissues in four patients. Neuroimaging studies, clinical decision making, operative experience, and long-term postoperative results were retrospectively reviewed. Four cases of AVM of the orbit and periorbital tissues were successfully treated with preoperative embolization and subsequent excision of the central nidus of the AVM. There was no evidence of recurrence in any of the cases over follow up ranging from 2 to 5 years. We conclude that identification of all arterial feeders, from both internal and external carotid systems, is critical in developing a therapeutic plan. AVMs may be treated by surgical excision alone, or embolization alone. However, in the hands of an experienced interventional neuroradiologist and an appropriately chosen surgical team, most AVMs can and should be treated by a combined approach of preoperative embolization followed by surgical excision of the vascular mass. The goal of therapy is closure of the low-resistance shunt.