Albert J. Dinnerstein

Delayed feedback as a possible mechanism in parkinsonism.

Many aspects of human behavior may be viewed as the functioning of feedback concrol systems (Powers, Clark, & McFarland, 1960). This paper is concerned with some temporal aspects of feedback factors, which might explain parkinsonian disability. Parkinsonism is a disorder involving a loss of normal synchrony beween agonist and antagonisc musculature and is characterized by motor signs such as muscle rigidity, tremor, and slowness of movement. In advanced stages the patient can neicher walk nor perform coordinaced hand and arm lnovemencs for such activicies as feeding or dressing himself. The disease is considered to be the result of malfunction of the extrapyramidal syscem but there is no complete neurophysiological explanation of the mechanism by which this malfunction produces the symptoms. It has been argued chat che motor symptoms result from a loss of normal inhibicion of antagonistic reflexive movement (Denny-Brown, 1950). The nature of che inhibirion and disinhibicion has noc been elaborated, however. The present auchors believe thac che loss of at least some of the normal patterns of control might be explained by the hypothesis of a simple perceptual malfunction, an abnormal delay in proprioception. The theory which follows draw heavily on che analogies of experimentally induced disabilities and on evidence concerning normal perceptual delay. While possible neurophysiological mechanisms are described, the theory is justified on the grounds of parsimony and on successful experimental tests rather than on the grounds of excluding alternative hypotheses.

The Interaction of Drugs with Placebos in the Control of Pain and Anxiety

Placebos are pharmacologically inert materials which are administered to patients, or experimental subjects, along with expressed or implied suggestions that they will produce some, usually therapeutic, effect. Despite their pharmacological inertness, placebos are moderately effective in the relief of pain and anxiety. For example, the administration of an inert material with the suggestion that it is analgesic is roughly 50 per cent as effective as morphine in controlling postsurgical pain [1]. Placebos can, moreover, affect almost any of the physiological states which are controlled by the central or autonomic nervous systems [2]. The placebo effects are based on the patients comprehension of, and emotional response to, the apparent drug administration. This comprehension and emotional response, and their physiological consequence, depend in great part on the instructions or suggestions given to the person receiving the capsule or injection of pharmacologically inert material. The placebo effects thus result from the patients knowledge that he has been treated plus his conception of the nature of the treatment. Active drugs could be, but seldom are, administered in a concealed form. Moreover, drugs are almost always given with expressed or implied suggestions concerning some expected effect. The administration of an active drug thus includes the same variables as are involved in the administration of a placebo. For this reason, active drugs always act, in part, as placebos. The observed effect of drug administration is thus a combination of the pharmacological effects and the placebo effects.

INTERMODAL PERCEPTION OF TEMPORAL ORDER AND MOTOR SKILLS: EFFECTS OF AGE

Employing visual, auditory, and tactile stimuli, intermodal differences in perceptual latency were inferred by means of perception of temporal order (PTO) and by varieties of serial reaction times (RT) to the same stimuli. Skill at reading, peg board, tapping, and tracking was also determined for the same Ss. Mean intermodal differences in latency inferred from PTO were significantly different from those obtained from mean RTs. A correlation matrix showed that individual differences in visual, auditory and tactile latencies inferred from PTO were relatively independent of latencies inferred from RT. Consonant with previous studies, PTO scores correlated with reading rate and also with peg board speed. Taking age of Ss into account, the latter correlations were seen to be due exclusively to the presence of older Ss, who did show a correlation between PTO and RT. It was hypothesized that aged Ss show a decrease in perceptual “channel capacity” and a resulting overloading of short-term memory when faced with a complex perceptual and motor task.

Pain attenuation by contralateral cold stimulation

Twenty Ss reported cold induced discomfort and pain thresholds for their right hand which was immersed in an ice water mixture, in trials with and without the left hand also immersed in ice water. The contralateral cold stimulation resulted in a significant elevation in both discomfort threshold and pain threshold.

Relationship between Pain Tolerance and Kinesthetic Size Judgment

40 Ss were tested in tasks measuring pain tolerance and kinesthetic size judgment. The results demonstrated a significant relationship between the two types of performance: Ss low in pain tolerance tended to make larger errors in KSJ than Ss with higher pain tolerance. Among Ss with descending series, pain tolerance correlated negatively with degree of overestimation of the standard. The results are consonant with the hypothesis that attentional function is the relevant underlying mechanism.

Marijuana and perceptual style: a theoretical note

The apparent effects of marijuana on perceptual, motor and cognitive skills are consonant with the hypothesis that it induces the perceptual style of field dependence. The evidence for this hypothesis is discussed along with additional hypotheses and suggestions for relevant research.

PERCEPTION SPEED AND BEHAVIOR: A THEORETICAL NOTE

In feedback control systems, delay of the feedback information can produce oscillations or other distortions of system output. Previously unrelated work by others, when viewed as aspects of a single functional process, point co the potential effect of temporal factors in sensory processes on aspects of behavior. The three areas of research to be related are as follows: 1. Human behavior is disrupted if conditions external to S produce a delay in sensory feedback. The experimental techniques involved electromechanical delay of visual, auditory or tactile feedback (Chase, Sumon, & Rapin, 1961). The disrupted behaviors grossly simulate stuttering or neuropachological disability. 2. Physiological mechanisms, related to the functioning of the reticular activating system, can vary the latency of afferent transmission. Thus, a mechanism for variable internal sensory delay exists (Magoun, 1958). 3. Psychophysical measurement shows that perception speeds can differ in differenc sensory modalities. These differences reflect stable individual difference and also vary with direction of attention (Angel1 & Pierce, 1892; Stone, 1926). The present authors hypothesize that physiological changes in latency of either afferent transmission or perceptual registration may produce changes in behavior similar to thac induced by externally delayed feedback. Psychophysical measures of relative perception speed reflect the changes in lacency and, thus, these measures of perception speed might be profitably employed in attempts to explain some of the normal individual differences in motor skills and aspects of parkinsonian disability. Normal behavior.-The speed of perception normally differs in differenc sensory modalities. These intermodal differences in perception speed vary among individuals. For individuals showing unusually long perceptual delays in given modalities, one would expect to find corresponding relative slowness or inefficiency of those behaviors which depend on the specific modalities for feedback control. For example, Ss with below average speed in auditory and kinesthetic perception should show slowness in speech; Ss slow in visual and kinesthetic perception should be poor in visual-motor coordination tasks, and Ss slow only in kinesthesis should be slow specifically in making simple arm movements. These deductions, never tested, follow directly from the facts concerning externally delayed feedback and from the data concerning normal individual differences in perception speed.

Effect of contralateral cold on pain tolerance

Fourteen Ss reported pain threshold and quit point in trials in which either right, left, or both hands were immersed in an ice water mixture. The contralateral cold stimulation resulted in significant elevation in both pain threshold and quit point for both right and left hands. The data also indicated that even nonpainful contralateral cold elevated pain threshold; this latter effect showed adaptation.

Perceptual Speed and Behavioral Proficiency

Perceptual speed in specific sensory modalities should lead to efficiency in behaviors governed by these modalities. To test this hypothesis, correlations were computed between measures of perceptual speed and scores on a modified Stroop test. Those correlations relevant to the hypothesis were all significant and in the expected direction. The pattern of results is thus reasonably consonant with the hypothesis. Reserpine, which might be expected to affect the above relationships, was ineffective.

Effects of Aspirin on Shock Induced Deterioration of Hand Steadiness

Effects of aspirin on hand steadiness were studied as a function of shock intensity and of the temporal relation of shock to behavior. Aspirin had no direct effect on hand steadiness, but increased the disruptive effects of pain and of shock anticipation. Aspirin lacked evident analgesic effects and apparently potentiated Ss responses to anxiety evoking stimuli.