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Biomedical subjects

D M Levinson

Publications and source records attributed to D M Levinson.

12 recordsLinked to original sources
PubMed1997

Monitoring recovery from traumatic brain injury using automated neuropsychological assessment metrics (ANAM V1.0).

Twenty-two students in the Coastline Community College Traumatic Head Injury Program completed two sessions of neuropsychological testing spaced 2-3 months apart, using ANAM V1.0. Eight (GP1) were marginally injured, seven (GP2) mildly, and seven (GP3) moderately. Comparisons of first-session accuracy scores with normative data revealed that GP1 was impaired on one test, while GPs 2 and 3 were impaired on 3 and 4 tests, respectively. Second-session accuracy scores were normal for GPs 1 and 2 on all tests, and impaired on one for GP3. Comparisons of first-session efficiency scores with normative data indicated that GP1 was significantly impaired on 2 tests, while GPs 2 and 3 were impaired on all 6. Second-session efficiency scores were normal for GP1 on 5 tests; GPs 2 and 3 also improved but remained impaired on all 6 tests. Based on efficiency, 91 % of the individuals were correctly classified.

Journal Article↗
PubMed1997

Density and the journey to work.

"This paper evaluates the influence of residential density on commuting behavior across U.S. cities while controlling for available opportunities, the technology of transportation infrastructure, and individual socio-economic and demographic characteristics. The measures of metropolitan and local density are addressed separately.... Regressions are conducted to predict commuting time, speed, and distance, by mode of travel on a cross-section of individuals nationally and city by city. The results indicate that residential density in the area around the tripmaker's home is an important factor: the higher the density the lower the speed and the shorter the distance.... The paper suggests a threshold density at which the decrease in distance is overtaken by the congestion effects resulting in a residential density between 7,500 and 10,000 persons per square mile (neither the highest nor lowest) with the shortest duration auto commutes."

Americas↗
PubMed1982

Photic cuing of escape by rats from an intense microwave field.

A total of 16 female hooded rats was first observed for baseline behaviors and then they received 25 2-min trials of training, five trials per day, under one of four stimulus conditions (all ns = 4): exposure to a highly intense 918-MHz field (dose rate, 60 mW/g); exposure to photic stimulation (approximately 350 1x); exposure to the field in synchrony with photic stimulation; or exposure to faradic shock (approximately 800 micro A rms). During conditioning trials, which were separated by 2-min intertrial intervals, entry by a rat into a safe area of a multimode cavity resulted in immediate and complete cessation of stimulation; exit, in resumption. Acquisition of the escape response was rapid and highly efficient for shocked animals and was less rapid and efficient but was reliably demonstrated by irradiated animals that were also signaled by light. In the absence of microwave irradiation, cessation of light did not reliably motivate escape behavior. Although there was weak evidence of escape learning by rats subjected only to microwave irradiation, their performance failed to differ reliably from those of rats in the light-only condition. These data confirm and extend those of Carroll et al, which indicate that potentially lethal, deeply penetrating, nonpulsed microwaves in a multipath field lack the sensory quality to motivate efficient aversive behavior by the rat.

Animals↗
PubMed1980

Failure of rats to escape from a potentially lethal microwave field.

Ocularly pigmented rats, all mature females of the Long-Evans strain, were repeatedly presented an opportunity to escape from an intense 918-MHz field (whole-body dose rate = 60 mW/g) to a field of lower intensity (40, 30, 20, or 2 mW/g) by performing a simple locomotor response. Other rats could escape 800-microamperemeter faradic shock to the feet and tail by performing the same response in the same milieu, a multimode cavity. None of 20 irradiated rats learned to associate entry into a visually well-demarcated area of the cavity with immediate reduction of dose rate, in spite of field-induced elevations of body temperature to levels that exceeded 41 degrees C and would have been lethal but for a limit on durations of irradiation. In contrast, all of ten rats motivated by faradic shock rapidly learned to escape. The failure of escape learning by irradiated animals probably arose from deficiencies of motivation and, especially, sensory feedback. Whole-body hyperthermia induced by a multipath field may lack the painful or directional sensory properties that optimally promote the motive to escape. Moreover, a decline of body temperature after an escape-response-contingent reduction of field strength will be relatively slow because of the large thermal time constants of mammalian tissues. Without timely sensory feedback, which is an essential element of negative reinforcement, stimulus-response associability would be imparied, which could retard or preclude learning of an escape response.

Animals↗
PubMed1980

Role of interproblem learning in interocular transfer.

The learning of a pattern discrimination may be divided into two components, one specific to the pattern task and another general to it and other tasks. The purpose of these experiments was to assess the degree to which these different components transfer interocularly, as well as to determine the effects of variations in prior acquisition on interocular transfer. In the first experiment, 28 albino rats were assigned to four equal groups that permitted assessment of the influences, on acquisition or interocular transfer of a pattern discrimination, of prior ipsi-ocular, contra-ocular, or sequential binocular training on a black-white task. Interocular savings were reduced by a factor of three when the black-white task (the general component) was acquired priorly, but there was no difference between the effects of prior contra-ocular training on black-white or pattern on subsequent monocular acquisition of the pattern task. Thus, all interocular transfer might be due to the general component. The second experiment, a partial replication, was performed to clarify whether information specific to the pattern task transferred interocularly. Again, interocular savings were reduced by a factor of three after prior black-white training. However, monocular acquisition of the pattern task facilitated subsequent contra-ocular learning of that same task more so than did prior monocular acquisition of a black-white task, indicating that some contribution is made to interocular savings by the information specific to the pattern task.

Animals↗
PubMedDate not supplied

Computerized measurement of cognitive impairment and associated neuropsychiatric dimensions.

This study aimed to cross-validate the capacity of a computer software program to detect and measure, using a measurement method applied to the content and form analysis of 5-minute speech samples, cognitive impairment and associated comorbid neuropsychiatric psychobiological dimensions in drug-abusing patients. At the University of California-Irvine (UCI) Neuropsychiatric Center, 28 drug-abusing inpatients using illegal drugs were clinically evaluated. Their scores for cognitive impairment derived by the computerized content analysis method were compared with scores derived from selected tests from the Halstead-Reitan Neuropsychological Test Battery, the computerized Automated Neuropsychological Assessment Metric Battery (ANAM), the Alzheimer's Disease Assessment Scale-Cognitive Portion, the Stroop Color and Word Test, the Symbol Digit Modalities Test, and the Controlled Oral Word Association Test. The statistical significance (P value) of the correlations of scores from these different measures with scores obtained from the computerized content analysis measures was less than .05 to .001. The comparative "hit rate," detecting cognitive impairment above the norms for each measure administered to these drug-abusing patients, for the computerized content analysis measures and some of the ANAM neuropsychological measures was 75% to 89%, and for the other neuropsychological measures, 25% to 64%. In conclusion, the computerized content analysis methodology applied to 5-minute verbal samples is a valid, rapid, easily administered measurement instrument for assessing the magnitude of cognitive impairment and comorbid neuropsychiatric dimensions.

Adolescent↗