Biomedical subjects

M Seidenberg

Publications and source records attributed to M Seidenberg.

8 recordsLinked to original sources

PubMed1992

Adequacy of language function and verbal memory performance in unilateral temporal lobe epilepsy.

We examined adequacy of language functions, their influence on verbal learning and memory performance, and the relative effects of language function and laterality of seizure focus on the memory performance of 99 left-hemisphere dominant patients with invasively verified epilepsy of left (N = 47) or right (N = 52) temporal lobe origin. Patients with left temporal lobe epilepsy (TLE) scored significantly lower than the right TLE group on several aphasia battery subtests (Visual Naming, Sentence Repetition, Token Test, Reading Comprehension, Aural Comprehension). Adequacy of language function (nominal speech) was significantly related to verbal learning and memory performance for both left and right TLE groups. Finally, comparison of the predictive significance of laterality of TLE and adequacy of language function indicated that language functions (Visual Naming and Aural Comprehension), but not laterality of TLE, were significant predictors for verbal learning and memory performance. It is concluded that: 1) adequacy of basic language functions is particularly compromised in left TLE, 2) there is a significant relationship between adequacy of language function and several aspects of verbal learning and memory ability in both left and right temporal lobe groups, and 3) clinical assessment and theoretical models of memory need to consider these relationships.

Adolescent↗

PubMed1992

Childhood epilepsy and the role of psychology.

The relatively long history of psychology's involvement in the field of epilepsy is discussed. The view of epilepsy is that of a chronic disorder with onset in childhood, at a time when normal development is at risk for interference from the direct and secondary aspects of repetitive seizures, the neurological abnormalities from which they arise, and the clinical interventions that attempt to control them. The objective and scientifically based methods of psychology are viewed as particularly well suited to these topics. Past efforts by psychologists have increased understanding of the syndrome that is epilepsy, and have paved the way for opportunities to further contribute to the theoretically and practically important problems associated with epilepsy.

Adaptation, Psychological↗

PubMed1992

Two allosteric modulators interact at a common site on cardiac muscarinic receptors.

The abilities of gallamine, obidoxime, tetrahydroaminoacridine (THA), and 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8) to alter the rate of dissociation of N-[3H]methylscopolamine from rat cardiac muscarinic receptors were investigated. All four ligands monotonically slowed the dissociation, with the order of potency gallamine > TMB-8 > THA > obidoxime. There was a dramatic difference in the efficacy of these allosteric modulators. Gallamine, TMB-8, and THA slowed the dissociation of N-methylscopolamine by > 90% at maximally effective concentrations, whereas obidoxime was capable of slowing it by only about 50%. In a manner analogous to the action of a partial agonist, obidoxime was able to partially reverse the effects of the other three modulators. Furthermore, the concentration-dependent effects of combinations of obidoxime and gallamine were in good agreement with the model of competitive interaction between these two ligands. These results provide the first evidence that two muscarinic allosteric modulators interact competitively at a well defined site.

Allosteric Regulation↗

PubMed1991

Mood state in unilateral temporal lobe epilepsy.

The purpose of this investigation was to reexamine the relationship between self-reported depression and laterality of temporal lobe epilepsy and to determine the contribution of associated frontal lobe dysfunction in predisposing patients to depression. Sixty-four patients with complex partial seizures of left (n = 26) or right (n = 38) temporal lobe origin were administered several self-report measures of mood state (Beck Depression Inventory, Center for Epidemiological Studies-Depression scale, Beck Anxiety Inventory), and a test of frontal lobe function [Wisconsin Card Sorting Test (WCST)]. There were no overall differences between the left and right temporal lobe groups on the measures of depression and anxiety. However, the left temporal lobe group exhibited a significant relationship between the degree of associated frontal lobe dysfunction (as indicated by increased perseverative responding on the WCST) and dysphoric mood state. For the right temporal lobe group there was a nonsignificant inverse relationship between mood state and indices of frontal lobe dysfunction. These results (1) are consistent with the broader psychiatric literature, which has implicated a relationship between depression and left frontal lobe dysfunction, (2) suggest that previous conflicting reports of depression/left temporal lobe epilepsy relationships are due in part to variations in the intactness of frontal lobe function, and (3) suggest that the presence of associated frontal lobe dysfunction may be a consideration in understanding interictal psychopathology in epilepsy.

Adult↗

PubMed1989

Priming and semantic memory loss in Alzheimer's disease.

Semantic memory (SM) was investigated in six patients with probable Alzheimer's disease (AD) by on-line measurement of semantic priming in a lexical decision task, and off-line tests of comprehension. Detailed assessment was carried out on naming, name comprehension, and probes of semantic knowledge with a battery of 150 items. The patients performed normally on perceptual tests and displayed an item-specific loss of knowledge on the semantic tests. In a primed lexical decision task, greater semantic priming was found relative to age-matched normals. The priming was substantially greater for items with "degraded" representations as determined by the off-line tests. Lexical decision was also performed more slowly on these items. These unexpected results demand a reevaluation of the concepts of the lexicon and semantic memory structure and their possible alteration in dementia.

Aged↗

PubMed1989

Changes in cerebral functioning associated with normal aging.

It has been suggested that the normal aging process is characterized by a pattern of neuropsychological performance decline that implies relatively greater vulnerability of right-hemisphere functions. This hypothesis was tested in a sample of 68 volunteers aged 20-75 who were free of systemic and neurologic illness. Neuropsychologic measures of lateralized and focal function were specifically selected to eliminate systematic procedural differences among tests (e.g., timed vs. untimed, overlearned vs. unfamiliar). Inferences about the localizing significance of each measure were based on previously demonstrated double dissociation of function in lesion studies. Results suggested that declines in cerebral efficiency are not differentially lateralized. Age correlated performance changes implied bilateral reduction that was significantly more pronounced on operations associated with frontal-lobe function. Anatomic and theoretical explanations for this pattern were discussed.

Adult↗

PubMed1989

Gallamine exerts biphasic allosteric effects at muscarinic receptors.

Although gallamine and a number of other compounds have been reported to slow the rate of dissociation of labeled ligands, especially [3H]N-methylscopolamine (NMS), from muscarinic receptors of heart and brain, there has been some dispute as to whether the dissociation of [3H]quinuclidinyl benzilate (QNB) is subject to such allosteric regulation. The present studies were intended to determine whether past discrepancies might be due to differences between tissues. We have found that gallamine modulates the dissociation of [3H]QNB from muscarinic receptors of the heart in a biphasic manner. Low concentrations (micromolar) accelerate the rate of dissociation, whereas higher concentrations (millimolar) slow it; at about 0.1 mM, the two effects cancel each other. Similar results were obtained with muscarinic receptors from the brainstem, but gallamine had only marginal effects on the dissociation of [3H]QNB in the forebrain. On the other hand, verapamil exerts only monophasic effects (slowing) on the dissociation of both [3H]NMS and [3H]QNB from heart receptors and gallamine slows the dissociation of [3H]NMS to a similar extent in all three tissues. Thus, it appears that past discrepancies in the literature can be attributed to the tissues and concentrations of gallamine that were used. Furthermore, the biphasic effects of gallamine suggest that there are multiple allosteric regulatory sites associated with muscarinic receptors.

Allosteric Regulation↗

PubMed1987

Interactions between gallamine and muscarinic receptors: allosterism and subpopulation specificity are separate phenomena.

The quaternary antagonist gallamine discriminates subpopulations of muscarinic receptors in the forebrain and brainstem of the rat and also modulates the binding of other muscarinic ligands via an allosteric mechanism in both brain regions. The calcium channel antagonist verapamil exhibits a similar allosteric effect in both regions (at 100 microM) but does not differentiate the subpopulations that are defined by gallamine. On the other hand, N-methylatropine does not produce the allosteric effect at 100 microM, but shows a high degree of selectivity (about 1,000-fold) for the gallamine-defined subpopulations. These studies indicate that the allosterism and subpopulation specificity of gallamine are separate phenomena and may be examined in isolation by appropriate ligands.

Animals↗