Richard C. Frecker

Power spectra for ocular drift and tremor

Eye position during fixation has been measured without contact and the power spectrum of drift and tremor eye movements has been estimated. In the 0-40 Hz frequency range power declines with frequency roughly as 1/f2. In the 40-100 Hz frequency range the dominant spectral component is a broad spectral peak with a peak amplitude of about 6 arc sec. The shape of the broad spectral peak is dependent on the fixation direction. A model that explains qualitatively the shape of the power spectra function is presented. It is suggested that tremor eye movements are by-products of the clock-like firing of motor neurons.

Effect of an undergraduate medical curriculum on students' self-directed learning.

Purpose. Lifelong, self-directed learning (SDL) has been identified as an important ability for medical graduates. To evaluate the effect of the University of Toronto Faculty of Medicine’s revised undergraduate medical curriculum on students’ SDL, a cross-sectional study was conducted. Method. A questionnaire package was mailed to 280 randomly selected students, 70 from each of the four years of the curriculum. The package contained the two most widely recognized, extensively used, and validated instruments of SDL (Guglielmino’s 58-item Self-Directed Learning Readiness Scale and Oddi’s 24-item Continuous Learning Inventory) and Ryan’s two-part Self-Assessment Questionnaire. An identification number and sociodemographic questions were included with the questionnaires. Data analysis was completed using chi-square for differences of proportions, analysis of variance for differences between means, and linear regression for trends. Results. A total of 250 (89.3%) complete questionnaire packages were returned. No significant trend in SDL was evident by curriculum year, and similar SDL levels were observed for women and men. However, a significant positive trend in SDL was found with the highest level of premedical education achieved (undergraduate only, masters, or doctoral). Further, students’ perceptions concerning the importance of SDL decreased according to year in the curriculum. Conclusion. This study found no evidence that students’ self-reported SDL is positively influenced by the current undergraduate medical curriculum at the University of Toronto Faculty of Medicine.

Self-selected blocking of vents on low-yield cigarettes.

Blockers of vents in ultra-low-yield cigarettes had higher levels of carbon monoxide (CO) and salivary cotinine than did nonblockers. None of the blockers reported that they blocked vents. Exposure differences seemed not to be due simply to vent blocking, but also to be the result of syndromes of heavier (blocking, more cigarettes per day, and starting earlier in the morning) or lighter smoking (not blocking, fewer cigarettes per day, and starting later in the morning). The results are interpreted in light of the boundary model. Cigarette smoking and brand selection should be studied as they occur naturally, as well as in experimentally contrived studies.

End-point nystagmus and ocular drift: An experimental and theoretical study

End-point nystagmus (EPN) and ocular drift during eccentric fixation were investigated in five normal subjects. All had EPN during prolonged eccentric fixation, two had sustained EPN within a few seconds of fixating an eccentric target. Our data show that the occurrence of EPN was determined by the velocity of slow phase ocular drift. Drift velocities greater than 1 deg/sec elicited sustained EPN or fatigue EPN while drift velocities lower than 0.3 deg/sec did not elicit EPN. Slow phase drift velocity increased with eccentricity and fixation duration and decreased with visual feedback. Computer simulations and theoretical analysis suggest that the reduction in drift eye movement velocity during fixation of a visible target, as compared to drift eye movement velocity during attempted fixation of a remembered target in darkness, is mainly due to the smooth pursuit system.

Nicotine yields of cigarettes, plasma nicotine in smokers, and public health

Abstract Previous research by M. A. H. Russell, M. Jarvis, R. Iyer, and C. Feyerabend (Brit. Med. J.280, 972–976 (1980)) concluded (a) that standard nicotine yields of cigarettes are very poor indicators of plasma nicotine concentrations in smokers, and therefore, (b) that the presumed health advantage of lower-yield cigarettes was likely not due to reduced “tar” intake by smokers of these cigarettes. The laboratory data, however, were not analyzed in a way that permits direct generalization to the epidemiological findings. A reanalysis of the data shows that the odds of deriving high yields increases substantially as the standard nicotine yield increases: lower risks associated with lower-yield cigarettes may be attributable to reduced nicotine (tar) yields to smokers. Implications for public health and the special risks of ventilated-filter cigarettes are discussed.

The Nature and Etiology of Normal and Alcohol Withdrawal Tremor

Alcohol withdrawal tremor is principally a postural-type tremor. That is, the tremor manifests itself most when the limbs are voluntarily maintained in a stationary position. The tremor of alcohol withdrawal is typically 5 to 20 times as large and approximately the same frequency as normal postural tremor. The fact that withdrawal tremor is uncorrelated in both outstretched hands argues against the involvement of a central pacemaker in the genesis of the tremor. Both withdrawal and normal physiologic type hand tremors are associated with synchronous firing of extensor motor units in phase with tremor velocity at the frequency of limb resonance. Both kinds of tremor are reduced by the p-adrenergic receptor blocking drug, propranolol. The reduction in tremor is caused by a decrease in the synchrony of motor units and not a decrease in the total number of units involved in maintaining limb posture. It is proposed that increased tremor during withdrawal is due to the entrainment by 1 A muscle spindle afferents of asynchronously firing motoneurons. Tremor is also increased by entrainment of motoneurons firing synchronously at 9 to 10 Hz due to an oscillation in the stretch reflex control system. Tremor reduction following propranolol is due to a decrease in entrainment because of decreased 1 A afferent inflow to the spinal cord or because of reduced sensitivity of alpha motoneurons to 1 A spindle afferent discharges.

Long‐term impact of addictions training for medical residents

The present survey was conducted to determine the long‐term impact of addictions training on the practice patterns of physicians who completed a specialized addictions residency training program. Medical residents and medical research fellows who participated in a residency training program in addictions from 1981 through 1991 at the Addiction Research Foundation in Toronto were mailed a brief questionnaire about their training experience. Of the 27 physicians who responded to the questionnaire (73% response rate), 52% were currently working in the addictions field. Of the 13 who were not working in the field, 77% reported using their addictions training in their current practice. Thus, 89% of the physicians who participated in the specialized addictions residency training program and responded to the survey reported continued utilization of their training several years after the experience.

Braking Performance of Drivers under the Influence of Alcohol and Cannabis

The effects of alcohol and marijuana were compared, separately and in combination, on the ability of subject drivers to bring their vehicles to a smooth stop in response to a light signal. The results suggest that driver performance is affected by doses of alcohol and marijuana normally associated with social use. Univariate analyses suggested that drivers under the influence of alcohol (alone or with marijuana) tend to brake sooner than when under the influence of marijuana or when not intoxicated. While the univariate analyses illustrated performance differences on several variables among selected drug conditions, none of the variables demonstrated significant differences identifying each drug condition. Multivariate analyses, on the other hand, were able to differentiate performance on one drug treatment from that on another. Research is recommended to develop an on-line monitoring device for detecting driver impairment.