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Biomedical subjects

L Nadel

Publications and source records attributed to L Nadel.

At least 37 records · Page 2Linked to original sources
PubMed1998

Spatial but not object memory impairments in children with fetal alcohol syndrome.

Behavioral dissociations on tests of cognitive abilities are powerful tools that can help define the neuropsychology of developmentally disabling conditions. Animals gestationally exposed to alcohol demonstrate spatial (place) but not object (cue) memory impairments. Whether children with fetal alcohol syndrome demonstrate a similar dissociation has received little attention. In this experiment, 30 Native American children, 15 previously identified with fetal alcohol syndrome and 15 control children, were asked to recall places and objects in a task previously shown to be sensitive to memory skills in individuals with and without mental retardation. As in animal models, children with fetal alcohol syndrome demonstrated a spatial but not an object memory impairment. A possible role for the hippocampus was discussed.

Arizona↗
PubMed1997

Severe spatial navigation deficit in the Morris water maze after single high dose of neonatal x-ray irradiation in the rat.

Ambiguous spatial behavior deficits induced in adult rats by different types of dentate gyrus lesions were examined by subjecting neonatal rats to x-ray irradiation, which reduces the granule cell population in fascia dentata without affecting the number of hilar neurons and pyramidal cells of Ammon's horn. Three- to six-month-old irradiated and intact male Long-Evans rats were tested in the Morris water maze. Four experiments were done. (i) Rats were trained to find an invisible escape platform, when started from any of four equidistant points at the circumference of the pool. (ii) The same rats then were trained to find a visible platform in the same pool. Poor performance of irradiated rats in both experiments suggested a visual deficit. (iii) Navigation in the absence of visual cues was studied in other rats trained in total darkness to find the escape platform under conditions of fixed start-fixed goal geometry. (iv) Contribution of nonvisual allocentric cues and egocentric path integration mechanisms to spatial performance of the above rats was tested in darkness after rotating both the start and goal positions by 90 degrees clockwise. Impairment of irradiated rats in Exp. 3 and 4 and histological examination of their brains support the conclusion that 60-70% reduction of granule cells in the dorsal hippocampus causes significant deterioration in both allocentric and egocentric orientation.

Analysis of Variance↗
PubMed1997

Memory consolidation, retrograde amnesia and the hippocampal complex.

Results from recent studies of retrograde amnesia following damage to the hippocampal complex of human and non-human subjects have shown that retrograde amnesia is extensive and can encompass much of a subject's lifetime; the degree of loss may depend upon the type of memory assessed. These and other findings suggest that the hippocampal formation and related structures are involved in certain forms of memory (e.g. autobiographical episodic and spatial memory) for as long as they exist and contribute to the transformation and stabilization of other forms of memory stored elsewhere in the brain.

Amnesia↗
PubMed1996

Electroconvulsive shock and lidocaine reveal rapid consolidation of spatial working memory in the water maze.

Head trauma leading to concussion and electroconvulsive shock (ECS) in humans causes amnesia for events that occurred shortly before the injury (retrograde amnesia). The present experiment investigated the amnesic effect of lidocaine and ECS in 25 rats trained on a working memory version of the Morris water task. Each day, the escape platform was moved to a new location; learning was evidenced by a decrease in the latency to find the platform from the first to the second trial. "Consolidation" of this newly encoded spatial engram was disrupted by bilateral inactivation of the dorsal hippocampus with 1 microliter of 4% lidocaine applied as soon as possible after the first trial. When trial 2 was given after recovery from the lidocaine (30 min after the injection), a normal decrease in latency indicated that the new engram was not disrupted. When trial 2 was given under the influence of lidocaine (5 min after injection), absence of latency decrease demonstrated both the success of the inactivation and the importance of hippocampus for the task. To examine the role of events immediately after learning, ECS (30 or 100 mA, 50 Hz, 1.2 sec) was applied 0 sec to 45 sec after a single escape to the new platform location. A 2-h delay between ECS and trial 2 allowed the effects of ECS to dissipate. ECS applied 45 sec or 30 sec after trial 1 caused no retrograde amnesia: escape latencies on trial 2 were the same as in control rats. However, ECS applied 0 sec or 15 sec after trial 1 induced clear retrograde amnesia: escape latencies on trial 2 were no shorter than on trial 1. It is concluded that the consolidation of a newly formed memory for spatial location can only be disrupted by ECS within 30 sec after learning.

Amnesia↗
PubMed1996

Spatial locations gone awry: object and spatial memory deficits in children with fetal alcohol syndrome.

Hippocampus vulnerability following gestational alcohol exposure has been demonstrated neuroanatomically and behaviorally in animal models of fetal alcohol syndrome (FAS). There has been no similar demonstrations in humans. The Smith and Milner (1981) Memory for 16 Objects task has been used to explore the effects of right vs left temporal lobectomy with varying degrees of damage to the hippocampus. In the present experiment, this same task was administered to 15 children with FAS (mean age 10.03, S.D. = 2.33) and 15 control children (mean age 10.02, S.D. = 2.31). Similar to patients with right temporal lobectomies and a large excision to the hippocampus, children with FAS were able to perform immediate but not delayed object recall, had a general spatial memory deficit (P < 0.05), and significantly distorted the spatial array (P < 0.05). Although these results are consistent with an interpretation of hippocampal dysfunction, gestational alcohol exposure is known to result in a wide-ranging spectrum of neuropsychological deficits that vary in both extent and severity. Visuospatial deficits on the Beery test of Visuomotor Integration and Clock Drawing are suggestive of the other neural regions that may be involved in producing the behavioral deficits in children with FAS.

Adolescent↗
PubMed1994

Brain structure changes in schizophrenics with high serum titers of antibodies to herpes virus.

We compared five indices of brain structure between two groups of schizophrenics, namely, those with high and normal levels of antibody in the serum to herpes virus. Eleven 'immuno-positive' and 21 'immuno-normal' subjects obtained from a concomitant study of serum IgG antibody to viruses underwent magnetic resonance imaging (MRI) utilizing a 1 Tesla magnet and 8 mm thick slices. We measured ventricle-brain ratio (VBR), 3rd ventricle width, cortical atrophy, area of corpus callosum, and frontal lobe area. The differences between groups were assessed by t-test and chi-square analysis. Eight of 11 immuno-positives compared to 7 of 21 immuno-normals showed evidence of cortical atrophy (chi 2 = 4.49, p < 0.03). The immuno-positives had smaller left frontal area (mean + s.d = 125.69 + 21.30 versus 143.76 + 19.84, t = 2.07, p < 0.05) and larger 2nd quadrant of the corpus callosum (mean + s.d. = 1.58 + 0.39 versus 1.27 + 0.52, t = 2.68, p < 0.01). The right frontal area also was smaller in immuno-positives but not significant. VBR, 3rd ventricle and the 1st, 3rd and 4th callosal quadrants did not differ between the groups. We conclude that high antibody titers to herpes found in the sera of some schizophrenics might reflect an earlier pathogenetic process that affected brain development. Further studies of antibodies in CSF and brain structure in these or similar subjects and those suspected to be exposed to viral infections in utero should be vigorously pursued to obtain definitive evidence for this hypothesis.

Adult↗
PubMed1991

Tumoral thrombosis of cerebral venous sinuses: preoperative diagnosis using magnetic resonance phase imaging.

Intracranial, dural-based neoplasms will not infrequently invade adjacent venous sinuses. Therefore, the preoperative diagnosis of venous invasion is important, as it will alter the surgical approach to the lesion. Magnetic resonance imaging is a noninvasive means of visualizing the cerebral venous sinuses. The preoperative diagnosis of venous thrombosis can, however, be difficult and confusing with conventional spin-echo magnetic resonance imaging because of variable appearances produced by blood clot degradation products as well as flowing blood. Phase magnetic resonance imaging is a simple method that can be acquired simultaneously with conventional spin-echo sequences, and is based primarily on whether protons are stationary or moving. In the context of venous sinus occlusion, phase imaging can demonstrate the presence or absence of blood flow more easily than spin-echo imaging. Three cases of dural-based neoplasms are presented that demonstrate the utility of phase imaging in diagnosing tumoral occlusion of the venous sinuses.

Adenocarcinoma↗
PubMed1991

Intracranial vascular abnormalities: value of MR phase imaging to distinguish thrombus from flowing blood.

The interpretation of conventional spin-echo and gradient-echo MR images of intracranial vascular lesions can be complex and ambiguous owing to variable effects on image intensity caused by flowing blood or thrombus. MR phase images, obtained simultaneously with conventional-magnitude images, are useful for evaluating proton motion (i.e., blood flow), and therefore can simplify the diagnosis of the presence or absence of thrombosis within a vascular structure or lesion. Fourteen patients with a variety of intracranial vascular abnormalities (aneurysms, superior sagittal sinus thrombosis, neoplasms adjacent to venous sinuses, and vascular malformations) were evaluated with conventional MR and phase imaging for the presence of blood flow. The phase images correlated with angiography in all cases. Phase imaging was not necessarily better than conventional spin-echo imaging in all cases, but it simplified the evaluation of thrombus vs blood flow in many. In three of five aneurysms, the phase images were diagnostic for evaluating lumen patency whereas the conventional images were ambiguous. Phase imaging was advantageous for detecting tumor invasion of the venous sinus when venous blood was enhanced by gadopentetate dimeglumine. A laminar flow phantom experiment determined the lower limits of sensitivity of phase imaging to be 0.5 cm/sec in the slice-select and 2.5 cm/sec in the read gradient directions. Phase imaging is a simple, reliable technique that can distinguish thrombosis from flowing blood within intracranial lesions. It is easily performed and adds no additional time to the MR examination.

Adolescent↗
PubMed1990

MRI of intracranial sinovenous thrombosis: the role of phase imaging.

Conventional spin-echo magnetic resonance (MR) imaging of venous thrombosis is complicated by the variable appearance produced by the stage of blood clot degradation and velocity of blood flow. Phase MR imaging is a simple method based primarily on whether protons are stationary or moving. A case of superior sagittal sinus thrombosis demonstrates the utility of phase imaging.

Adult↗
PubMed1990

CT and MR imaging of the central skull base. Part 1: Techniques, embryologic development, and anatomy.

Recent advances in surgical techniques have enabled surgeons to approach previously inoperable deep-seated lesions of the skull base. The radiologist requires a thorough knowledge of the normal anatomy and the pathologic spectrum of this region and an understanding of imaging modalities in order to determine the extent of pathologic conditions and help plan the surgical approach. The embryologic development of the central skull base, normal gross anatomy, and anatomy as seen on computed tomographic and magnetic resonance images are presented.

Humans↗
PubMed1990

CT and MR imaging of the central skull base. Part 2. Pathologic spectrum.

The radiologist must have a thorough knowledge of the normal anatomy and the pathologic spectrum of the skull base to determine the extent of abnormality and to help plan the surgical approach. The authors describe and present examples of congenital, benign, and malignant lesions that affect this region, including cephalocele, fracture, fistula, juvenile angiofibroma, meningioma, chordoma, pituitary adenoma, chondrosarcoma, nasopharyngeal carcinoma, and rhabdomyosarcoma. Metastatic, infectious, and other miscellaneous processes are also discussed. Imaging strategies with computed tomography and magnetic resonance imaging to aid in the diagnosis are suggested.

Adolescent↗
PubMed1990

Perineural tumor extension through the foramen ovale: evaluation with MR imaging.

Perineural tumor extension is a form of metastatic disease in which primary tumors spread along neural pathways and gain access to non-contiguous regions. The treatment and prognosis are altered when perineural extension occurs. Awareness and proper evaluation are critical for the radiologist. The third (mandibular) division of the trigeminal nerve (V3), passing through the skull base via the foramen ovale, is a common route of perineural spread of head and neck lesions. Seven patients with perineural tumor involvement of the mandibular nerve were evaluated with magnetic resonance imaging with use of standard spin-echo pulse sequences emphasizing T1-weighted information. Three patients had adenoid cystic carcinoma, three had squamous cell carcinoma, and one had well-differentiated lymphocytic lymphoma of the orbit. MR imaging signs of perineural involvement included smooth thickening of V3, concentric expansion of the foramen ovale, replacement of the normal trigeminal cistern hypointensity by an isointense mass, lateral bulging of cavernous sinus dural membranes, and atrophy of masticator muscles.

Carcinoma, Adenoid Cystic↗
PubMed1987

Spatial learning in the rat: impairment induced by the thiol-proteinase inhibitor, leupeptin, and an analysis of [3H]glutamate receptor binding in relation to learning.

Rats were given continuous intraventricular infusion of saline or the thiol-proteinase inhibitor leupeptin, via subcutaneously implanted osmotic minipumps, while being trained on a spatial learning water task using spaced trials. Leupeptin caused overnight forgetting during training, but performance eventually reached asymptote in both groups. A retention test conducted 48 h later to assess spatial memory revealed no significant group differences, but did cause, in saline-treated rats only, a disruption of subsequent retraining back to the correct spatial location. The groups showed no differences in Cl-dependent [3H]glutamate receptor binding to hippocampal or entorhinal cortex membranes subsequent to training. In a second experiment, normal rats trained on the same task also showed no differences in Cl-dependent [3H]glutamate binding relative to rats exposed to the water task but given random spatial position training and handled controls. The results are discussed in relation to the hypothesis of Lynch and Baudry (Science (1984) 224, 1057-1063) that a calcium-dependent thiol proteinase is involved in memory formation through its ability to modify glutamate receptor distribution and dendritic spine shape.

Animals↗