Daniel M. Levinson

Predictors of adherence to triptans: factors of sustained vs lapsed users.

Objective.— The present study was conducted to identify factors that predict adherence to triptans by migraine patients.

Acquisition and retention of monocular discriminations in rats as a function of relevant (reversal) or irrelevant opposite-eye training

Albino rats retained a monocular pattern discrimination even after interpolated mastery of a reversal or a black-white discrimination via the opposite eye. In the first experiment, a second-eye reversal problem was acquired more rapidly than the original pattern problem. The second experiment showed that monocular training on a black-white problem has a marked facilitatory effect on subsequent acquisition of a pattern discrimination with the opposite eye.

Assessment of the generality of enhanced learning following unilateral lesions of posterior neocortex in rats

Sixty albino rats with unilateral lesions of striate cortex, unilateral orbital enucleations, or sham operations were trained on black-white and horizontal-vertical discriminations, with order of problem presentation counterbalanced. Mastery of the initially acquired discrimination greatly enhanced acquisition of the second; however, the previously 4 reported enhancement of acquisition associated with unilateral striate ablation proved to be of limited generality: it occurred only during initial learning of the horizontal-vertical problem.

A modification of the Hulse lickerandum: Preliminary studies and suggested applications

Three problems bearing on the utility of the rat’s tongue lick were attacked with provisional success: first, slight modification of an extant operandum-feeder afforded a simple and flexible means of measuring, and reinforcing the licking operant; second, Ss’ performances on FR schedules demonstrated that the tongue-lick, while possessing respondent properties, is unequivocally a “free” operant; and third, gross examination of 10 rats’ tongues following 55,000 to 127,000 licking responses revealed no observable deleterious changes. Several applications are suggested.

Interocular transfer in albino rats as a function of forebrain or forebrain plus midbrain commissurotomy.

Abstract An attempt was made to determine whether interocular transfer of a black-white discrimination would be blocked by section of interhemispheric pathways. Thirty-six albino rats were equally divided into three surgical treatment groups: sham-operate, corpus callosum-section, or corpus callosum-plus superior colliculus- and posterior commissure-section. Before statistical analyses of the behavioral data were performed, the animals were reassigned to appropriate groups based upon histological examination of the lesions. The multiple-commissurotomized animals showed nearly complete incidental section of hippocampal and habenular commissures, while the callosal-sectioned and sham-operated animals had comparatively little incidental damage. The callosal-sectioned and sham-operated animals exhibited interocular transfer of a black-white discrimination, although the callosal-sectioned animals showed less transfer than the sham operates. The multiple-commissurotomized animals showed no transfer; they also made reliably more errors during acquisition via the second eye (i.e., during the test for transfer) than either the sham operates or corpus callosal-sectioned animals. These results are comparable to previous research on cats. In addition, there were no differences in the initial rates of acquisition of the black-white discrimination between the three groups; these data suggest that section of the commissures does not impair the normal mechanisms needed to acquire the discrimination.

Endogenous hyperthermia in normal human subjects. I: Experimental study of evoked potentials and reaction time

Previous work on awake guinea pigs and rats in the authors’ laboratory revealed that microwave-induced elevations of brain temperature (ΔTs from 1° to 3° C over resting baselines) are associated with reliable reductions in latencies of flash-evoked brain potentials’ (EPs). To assess the generality of this finding in the normal human being, and to avoid the ethical problem of whole-body human exposure to an intense microwave field, ΔTs were induced endogenously by vigorous exercise and by insulative and vapor-barrier clothing. Twenty male athletes, 18 to 22 years of age, were randomly but equally divided into counterbalanced experimental and control groups for a single 3-h morning or afternoon session of measurements. During baseline measures, EPs of three types were observed: flash-evoked N1, pattern-reversal P100, and event-related P300. In addition, simple reaction times (RTs) to photic stimulation were recorded. All measures were repeated after sham warming of the 10 control subjects and after tympanically indexed brain temperatures of the 10 experimental subjects were elevated by an average of 1.2° C above control values. EP and RT latencies were reliably reduced in association with the ΔTs, the mean reductions ranging from 3% to 9%. The data on the human flash-evoked N1 component compare favorably with data recorded from rats and guinea pigs that have undergone exogenous elevations of temperature by microwave irradiation. The data on RTs and other EP components are consistent with the thesis that human CNS activity in general is accelerated during a modest bout of whole-body hyperthermia.

Development of Social Behavior in the Guinea Pig in the Absence of Adult Males

Thirty-six guinea pigs were observed from birth to 60 days of age in a colony containing no adult males. The average first day of occurrence for each of 12 social behaviors was recorded for males and females both as initiators and as recipients. Social behaviors associated with exploration were the first to appear. Unlike previous observations reported by us on a colony with adult males present, the appearance of aggressive behaviors was delayed from weaning to about the onset of puberty. The appearance of sexual behaviors was also somewhat delayed; however, the successful mount appeared much earlier when adult males were absent.

Assessment of the contact eye cover as an effective method of restricting visual input

In the wake of several studies that have cast doubt upon the effectiveness of contact eye covers in restricting vision, we performed a series of five experiments to the end of achieving reversible blinding of the albino rat. The data of Experiment 1 indicated that the contact eye cover can be as effective as a rubber cup in restricting visual input. In Experiment 2, animals that were fitted binocularly with opaque eye covers performed as if blind on a task involving acquisition of pattern discrimination. In Experiment 3, binocular coverage with the opaque eye cover resulted in chance performance across 300 trials of a previously acquired pattern-discrimination habit. In Experiment 4, the base diameter of the eye cover was found to be a critical factor: Performance of a previously acquired brightness discrimination was reduced to chance levels by contact eye covers that approximated 7.0 mm in diameter. In Experiment 5, a smaller eye cover (6-mm diam) had no effect in limiting the visually evoked electrocortical response of the albino rat, while an eye cover of 7.2-mm diam produced a reliable attenuation of the response. The collective results indicate that appropriately fabricated contact eye covers are a viable means of restricting visual input and may justifiably be considered contact occluders.

Effects of fixed ratio training on subsequent preference for the reinforcer

Four groups of albino rats received the same number of 0.1 cc maltose-solution reinforcements in a Skinner box, either on FR 10, FR 5, Crf, or noncontingent upon the bar press. In addition, a water-reinforced control group received the same number of 0.1 cc noncontingent distilled water reinforcements. Subsequently, all Ss were given a cafeteria-style preference test with the same maltose solution used during training and an unfamiliar sucrose solution as alternatives. All measures revealed a decline on the part of the fixed ratio groups in preference for the solution used as a reinforcer during training. This contrasts with a previous report that the effect of high effort training on reinforcement value is incremental.

Monocular acquisition and interocular transfer in albino guinea pigs as mediated by ipsi- or contralateral fiber systems.

Monocular acquisition and interocular transfer of a horizontal-vertical discrimination were measured in 12 male albino guinea pigs with unilateral lesions of the striate cortex, and in 6 sham-operated controls. In accordance with electrophysiological and anatomical findings, the animals learned readily using the contralateral fibers, while the ipsilateral fibers were found to be incapable of mediating either acquisition, or retention, of the discriminarion. The control animals learned readily, but showed incomplete transfer.