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Biomedical subjects

T H Jobe

Publications and source records attributed to T H Jobe.

At least 19 recordsLinked to original sources
PubMed2001

Statistical versus fuzzy measures of variable interaction in patients with stroke.

UNLABELLED: Evidence-based medicine, founded in probability-based statistics, applies what is the case for the collective to the individual patient. An intuitive approach, however, would define structure in the (physiologic) system of interest, the human being, directly relevant to other systems (patients) composed of similar variables. A difference in measure of variable interaction in the patient from that in the collective would show how extrapolation of information from the latter to the single patient is counterintuitive. METHODS: We compare statistical to 'fuzzy' measures of variable interaction. Three diagnostic variables are considered in 30 stroke patients who underwent the same diagnostic tests. 'Fit' (fuzzy information) values [0, 1] for degree of variable severity were expertly assigned by 2 blinded raters for real and fabricated patients. Fabricated patients were composed of real-patient 'fit' values after shuffling. Real and fabricated patients were each numerically represented as a set. Three groups of fabricated patients and the real patient group were studied. Statistical [Pearson's product-moment (regression analysis) and Spearman's rank correlation] and three different fuzzy measures of variable interaction were applied to patient data. RESULTS: Interaction for blood-vessel measured strong in real patients, and weak after one shuffle, using all fuzzy measures. By comparison, the same interaction was found in real patients by only 1 rater (Rater 2) using 1 statistical technique (Spearman's rank correlation) which, as did Pearson product-moment correlation, found a 'significant' interaction between blood-heart in fabricated patients. CONCLUSION: Our study suggests that the measure of variable interaction in nature - as combined in the individual (real) patient - is captured robustly by fuzzy measures and not so by standard statistical measures.

Evidence-Based Medicine↗
PubMed2000

Thought disorder in schizophrenia and mania: impaired context.

This research studied hypotheses that positive thought disorder in schizophrenia is influenced by patients' not taking in immediate target contextual material, thereby losing vital cues that guide thought processes. We assessed 164 acute inpatients (including 55 schizophrenia and 31 bipolar disorder patients), using standardized measures of thought disorder. We also used new measures that assessed (1) total ignoring of context, and (2) straying from the context. Results were as follows: (1) only 9 percent of the schizophrenia patients showed strong evidence of completely ignoring the external context; (2) straying from the external context while simultaneously maintaining part of the context was significantly more common than complete absence of context (p < 0.01); (3) patients with thought disorder strayed from the context significantly more than patients without thought disorder (p < 0.001); and (4) straying from the context was involved in the thought disorder of some, but not all, schizophrenia and mania patients. The data suggest that thought disorder in schizophrenia is not typically due to a failure to "hear" or to take in the relevant contextual material necessary for an appropriate response. Loss of context is involved in some, but not all, thought disorder in schizophrenia and mania.

Adult↗
PubMed1999

Causal interactions, fuzzy sets and cerebrovascular 'accident': the limits of evidence-based medicine and the advent of complexity-based medicine.

In evidence-based medicine, stroke subtype is diagnosed after a sequential search for etiology; the first positive test result of significant severity rounds off to one overwhelming cause. Degree of severity, interaction among variables, and concomitant variable conditions are not considered in defining the cause of stroke. Yet, thrombus formation, and possibly vascular rupture, is an interactive process involving the vascular wall, flow properties of the blood and blood constituents; this process occurs in homeostasis and pathology. Evidence-based medicine ignores this process and instead studies stroke using crisp 'all or none' classification where subtypes are distinct and interactively relate only to outcome. As a result, scientific inquiry is focused on prediction for the collective of patients. The statistical approach of evidence-based medicine is founded on probability theory, itself rooted in classical set theory where elementhood is all (1) or none (0), and opposites interact only to form the null set. Fuzzy set theory, where set membership is to degree [0, 1], encompasses classical set theory, allows for an interactive process between variables, and therefore becomes the measure of complexity. Fuzzy set theory can change the scientific method of evidence-based medicine.

Cerebrovascular Disorders↗
PubMed1997

Psychosis in medical conditions: response to risperidone.

We report the response to risperidone in seven hospitalized, adult patients who presented psychotic symptoms etiologically related to a general medical condition. The conditions included brain surgery in two, and anticardiolipin syndrome, renal failure, epilepsy, lupus, and metastatic carcinoma in one each. Four patients had failed previous treatment with at least one typical antipsychotic agent. Response to risperidone was assessed by the Brief Psychiatric Rating Scale (BPRS). Serum was collected for measurement of steady-state trough risperidone and 9-hydroxyrisperidone concentrations at effective doses in three patients. Amelioration of psychotic symptoms was noted in all seven patients. Mean (+/- SD) BPRS scores were reduced significantly from baseline (63.0 +/- 15.1) to endpoint (27.0 +/- 3.5; p < 0.01). The mean effective daily dose of risperidone was 3.1 +/- .7 mg and time to response was 4.7 +/- 2.4 days. Risperidone was not present at detectable concentrations in the three patients studied. The mean steady-state trough serum concentration of 9-hydroxyrisperidone in the three patients assessed was 20.3 +/- 9.8 ng/ml. These preliminary findings, which suggest that risperidone is a safe and effective agent in patients with psychotic symptoms due to various medical conditions, need to be confirmed by randomized, antipsychotic comparison trials involving a larger number of patients.

Adult↗
PubMed1997

Cerebral perfusion SPECT imaging in epileptic and nonepileptic seizures.

Patients with epileptic and nonepileptic seizures are commonly encountered in clinical practice, and they can pose a difficult diagnostic problem. We present two cases that show the difficult task of differentiating between true epileptic and nonepileptic or psychogenic seizures in some patients. The clinical presentations were complex and the use of video-monitored EEG alone was insufficient to make definitive diagnoses. Ictal and interictal Tc-99m HMPAO brain perfusion SPECT imaging examinations were used to help establish the correct diagnoses. This report describes the advantage of using the brain perfusion SPECT imaging examination. The injection of stabilized Tc-99m HMPAO during an ictal event followed by appropriate medical therapy provides a method of obtaining a reasonable image of relative perfusion (activity) during the seizure. These images can then be compared with interictal examinations and an epileptic or nonepileptic focus may be localized. The Tc-99m HMPAO brain perfusion SPECT imaging study was helpful in establishing the correct diagnosis in both cases.

Adult↗
PubMed1997

Application of ictal brain SPECT for differentiating epileptic from nonepileptic seizures.

The authors report 2 clinical cases that illustrate the difficulties with video-monitored EEG and the advantages of brain SPECT in differential diagnosis of true epileptic seizures and nonepileptic seizures. Injection of [99mTc]HMPAO at the time of the ictal event provides a means to obtain a SPECT image postictally for comparison with interictal examinations so that an epileptic or nonepileptic focus may be localized.

Adult↗
PubMed1996

Compton scatter correction in case of multiple crosstalks in SPECT imaging.

A strategy for Compton scatter correction in brain SPECT images was proposed recently. It assumes that two radioisotopes are used and that a significant portion of photons of one radioisotope (for example, Tc99m) spills over into the low energy acquisition window of the other radioisotope (for example, Tl201). We are extending this approach to cases of several radioisotopes with mutual, multiple and significant photon spillover. In the example above, one may correct not only the Tl201 image but also the Tc99m image corrupted by the Compton scatter originating from the small component of high energy Tl201 photons. The proposed extension is applicable to other anatomical domains (cardiac imaging).

Humans↗
PubMed1995

Neuropoiesis: proposal for a connectionistic neurobiology.

Given current assumptions about the biology of neural organization, some connectionists believe that it may not be possible to accurately model the brain's neural architecture. We have identified five restrictive neurobiological dogmas that we believe have limited the exploration of more fundamental correlations between computational and biological neural networks. We postulate that: 1) the dendritic tree serves as a synapse storage device rather than a simple summation device; 2) connection strength between neurons depends on the number and location of synapses of similar weight, not on synapses of variable weights; 3) axonal sprouting occurs regularly in adult organisms; 4) the postsynaptic genome directly controls the presynaptic cell via mRNA, rather than indirectly by the expression of NCAMs, reverse neurotransmitters, etc.; 5) dendritic spines serve a trophic function by controlling development of new sprouts via a process we term retroduction. We entertain an alternative formulation of a computational neural element that is fully consistent with modern neuroscience research. We then show how our model neuron can learn under Hebbian conditions, and extend the model to explain non-Hebbian, one-trial learning. This work is significant because by stretching the theoretical boundaries of modern neuroscience, we show how connectionists can potentially create new, more biologically-based neural elements which, when, interconnected into networks, exhibit not only properties of existing backpropagation networks, but other physiological properties as well.

Adult↗
PubMed1994

Schizophrenic deficits: neuroleptics and the prefrontal cortex.

Modern techniques have been applied to brain modeling, based on recent approaches in the artificial intelligence field that use brain-like "connectionistic" computational architectures. The model proposed by Cohen and Servan-Schreiber uses a gain parameter which they identify with dopamine function. They apply their model to neuroleptically treated schizophrenia patients who show improved task performance which they link to increased dopamine function and increased gain in the prefrontal cortex. However, evidence indicates that antipsychotic medications block dopamine (especially D2) receptors, decreasing mesolimbic and mesocortical dopamine function. If therapeutic dosages of neuroleptics diminish dopamine function, this would decrease gain in context modules needed for adequate task performance. Schizophrenia patients would perform more poorly by further reducing gain in their already compromised context modules. The current investigators suggest three possible ways to resolve this difficulty, to explain why normals perform more poorly when taking neuroleptics, although acute schizophrenia patients' performance may be enhanced in several areas. Evidence would suggest that multiple processes occur simultaneously in neuroleptically treated patients with some processes counterbalancing others.

Antipsychotic Agents↗
PubMed1992

Pisa syndrome mistaken for conversion in an adolescent.

We present a case of acute dystonia in an adolescent, with features that fit the description of the Pisa syndrome. The symptoms developed postoperatively, in a non-psychiatric setting, following administration of antiemetic medication, and the phenomenon was misdiagnosed as a conversion disorder. This case reinforces previous reports cautioning against misinterpretation of dystonic reactions as functional disorders, especially in children and adolescents.

Adolescent↗
PubMed1986

4 p.m. baseline cortisol level as a predictor of DST results in depression.

To assess the relationship of baseline cortisol to the 1 mg dexamethasone suppression test (DST), 4 p.m. baseline and 4 p.m. postdexamethasone blood samples were drawn on 52 consecutive depressed outpatients. Baseline cortisol correlated significantly with post-DST values, and baseline levels above 15 micrograms/dl predicted DST nonsuppression with 90.4% accuracy. These data lend some support to the usefulness of baseline cortisol determination in depressed outpatients in whom a full DST may be difficult.

Ambulatory Care↗