Pharmacological analysis of conditioning in sensorimotor cortex neurons in a model

In awake mobile rabbits, with electrodes implanted in the medial lemniscus, midbrain tegmental reticular nucleus, and pyramidal tract, combined stimulation of two brain structures resulted in elaboration of conditional connections in sensorimotor cortex neuronal populations. The main criterion of the conditioning was the appearance of changes in the neuronal activity on omission of the second stimulus. These changes represented a complex of electrical events, some of which were similar to and others different from the evoked responses to the second stimulus. Application of atropine, sulfate, chlorpromazine hydrochloride, serotonin creatinine sulfate, andγ-aminobutyric acid (GABA) to the cortex at the site of the recording exerted a modulating effect on the conditional neuronal activity patterns. Of the above substances, GABA and atropine had the most pronounced effect. The GABA removed the short-latency components of the conditional changes which were similar to evoked responses. The atropine abolished the long-latency changes which differed from evoked responses.     

The relative accessibility of phonemes and syllables

Previous research comparing detection times for syllables and for phonemes has consistently found that syllables are responded to faster than phonemes. This finding poses theoretical problems for strictly hierarchical models of speech recognition, in which smaller units should be able to be identified faster than larger units. However, inspection of the characteristics of previous experiments’ stimuli reveals that subjects have been able to respond to syllables on the basis of only a partial analysis of the stimulus. In the present experiment, five groups of subjects listened to identical stimulus material. Phoneme and syllable monitoring under standard conditions was compared with monitoring under conditions in which near matches of target and stimulus occurred on no-response trials. In the latter case, when subjects were forced to analyze each stimulus fully, phonemes were detected faster than syllables.     

A microcomputer-based tracking task for examination of the spatial and temporal organization of perceptual motor skill

A microcomputer-based tracking task is described in detail. The program that controls this task was written in Pascal and 6502 assembler language and was designed to run on an Apple IIe computer. The program was designed to allow the experimenter to vary such parameters as the velocity of the stimulus signal. In addition, several indicants of performance are recorded simultaneously and are averaged over selected time intervals during each trial. The paper also illustrates the applications of this particular computer program in the study of motor control and learning.     

Variations in the training parameters of an avoidance conditioning paradigm and their effects on the acquisition and performance

Albino rats were trained in a delayed discriminated conditional avoidance response (CAR) to study the possible effects of varying the various training parameters,viz., the CS-UCS interval, the stimulus and strength of the inter-trial and intersession intervals on the acquisition and performance of the CAR. The response latency (RL) was related to the CS-UCS interval in a serial trend while there were response failures (ER%) at both extremes. The efficiency of the CAR were also varied according to the stimulus strength, improving up to 2 mA intensities and declining thereafter. The CAR deteriorated, as reflected in increased magnitudes of RL and ER%, with increasing intertriai intervals of 4 min or more, both in trained and trainee rats, but was not significantly affected by increasing intersession intervals unless it was 7 days or above. These findings are discussed in the light of the known principles of classical conditioning as well as of electrophysiological findings from instrumental animal conditioning studies.     

Electrocutaneous stimulation: Psychometric functions and temporal integration

Psychometric functions and psychophysical strength-duration curves were obtained with rectangular electro-cutaneous pulses. The slopes of the psychometric functions were much steeper than corresponding functions in other modalities, with the standard deviation of the distribution only about 0.08 times the threshold. Precise monitoring of stimulus current showed that physiological rather than physical variability was involved. Psychophysical strength-duration curves support the contention that large A-fibers are directly stimulated. Data from this study. as well as from comparable I × t experiments in other senses, are well-fit throughout the range of durations by rectangular hyperbolas. The period over which complete temporal summation occurs is only about 0.5 msec.     

The Pavlovian basis of reciprocal inhibition therapy

While there is a slight disagreement between Wolpe’s views and Pavlov’s statements concerning the application of experimental psychology to the study of psychiatry, Wolpe indicates that he owes much to Pavlov. A Pavlovian analysis of therapy by reciprocal inhibition, which includes the physiological constructs as well as Pavlovian methodology, will increase our understanding of Reciprocal Inhibition therapy. The major techniques of Reciprocal Inhibition therapy are discussed in the terms of Pavlovian method and theory. Desensitization based on systematic relaxation appears to be effective because the excitatory stimulus is presented when the subject’s cortex is predominantly in an inhibitory state while relaxed. Assertive training relies mainly on building up the excitatory process by use of the second signal system. Thought-stopping is analogous to the external inhibition procedure with the use of the second signaling system as the “extra” stimulus. Deductions from Pavlov’s typology predict that an excitable subject will be difficult to desensitize and somewhat easier to train in assertive behavior and thought-stopping. Some implications of relating Pavlovian method and theory to Reciprocal Inhibition therapy are discussed.     

Reaction time to different wavelengths at various luminances

The present investigation is concerned with determining whether or not differences in the reaction times exist in a human subject’s responses to 6 different wavelengths equated at 5 levels of luminance. The heterochromatic matching was done by the method of flicker photometry and checked by the method of direct comparison. Simple reaction time, the time interval starting with the presentation of a visual stimulus and terminating in a manual response, was used as the method of determining the latencies for the establishment of equal sensory effects for the different wavelengths. Monocular viewing of the stimuli was used by two subjects and reaction times are determined over a luminance range of 5.2 log units around a central value of I millilambert. The results indicated that simple reaction time is inversely related to stimulus luminance. There were no differences in the reaction times to the different wavelengths at the four highest luminance levels; at the lowest luminance level, the wave-lengths fan out in a manner that is in line with the classical data of vision. In other words, the visual functions obtained with simple reaction time parallel certain well-known visual functions in intensity discrimination, flicker and visual acutty-the results may be accounted for by the Duplicity Theory of vision.     

Using the Macintosh computer in psychophysiological research: Programs for stimulus presentation,data collection,and response quantification

In this paper, we describe two Turbo Pascal programs, one for the control of stimulus presentation and measurement with peripheral devices (BLINK) and another for off-line stimulus reduction and analysis (SCORE). The programs can be applied in a wide variety of research settings. The programs do not use all of the interactive features of the pull-down menus found in the Macintosh, which increases the degree to which they can be modified for local use. They do not require familiarity with programming.     

Auditory overselectivity in autistic children

Autistic and normal children were trained to respond to a complex stimulus containing two auditory components. After the discrimination was acquired, the individual components were presented separately, allowing assessment of the extent to which the child's responding was controlled by one or both of the cues. The autistic children, unlike the normal children, provided evidence for stimulus overselectivity in that 6 of 8 autistic subjects responded to only one of the components. These results are consistent with those of previous studies which showed that when autistic children are presented with a complex visual or multiple-modality stimulus, they selectively respond to only one component of the complex. The present results extend the stimulus overselectivity hypothesis to the situation where all of the stimuli occur within the auditory modality. It is suggested that auditory overselectivity may partially account for autistic deficits in speech comprehension.     

An IBM XT-compatible,computer-based,slide-projector laboratory

In the present paper, we describe the software and hardware of an on-line, visual-memory laboratory running under Turbo Pascal on an IBM PC XT-compatible computer. The display system includes one Kodak random access projector and four standard Kodak carousel projectors, all equipped with tachistoscopic shutters and luminance-control devices. The response system consists of eight 16-key response boxes. The laboratory can be used for any experiment in which 35-mm slides are to be used as stimuli, and in which precise display times, stimulus luminances, and reaction times are required. The laboratory is particularly well suited to picture-perception and picture-memory experiments.     

Prediction of choice reaction time from information of individual stimuli

A model is developed to predict the reaction time to stimuli using information content of the individual stimuli. Review of previous research in the area showed inconsistencies due possibly to the mode of stimulus presentation or to the number of stimuli. Two experiments designed to cover the range of variables used in previous experiments were conducted. The results indicate that the model makes accurate predictions over the entire range of variables used. A comparison to earlier studies also indicates a close correspondence. nt|mis|Acknowledgment is due the Office of Naval Research which supported this research through a prime contract, NOnr 2512(00), with General Dynamics Electric Boat Division as a part of the SUBIC. (SUBmarine Integrated Control) program.     

Note on Crozier’s Neural-Availability theory

Two implications of Crozier’s Availability theory are developed. First, the population of elements of neural effect is shown to have a minimum size. Second, intensity discrimination must be mediated by progressively smaller increments in neural effect as stimulus intensity is increased-an improbable state of affairs.     

A sequential theory of psychological discrimination

A theory of discrimination which assumes that subjects compare psychological values evoked by a stimulus to a subjective referent is proposed. Momentary differences between psychological values for the stimulus and the referent are accumulated over time until one or the other of two response thresholds is first exceeded. The theory is analyzed as a random walk bounded between two absorbing barriers. A general solution to response conditioned expected response times is computed and the important role played by the moment generating function (mgf) for increments to the random walk is examined. From considerations of the mgf it is shown that unlike other random walk models [Stone, 1960; Laming, 1968] the present theory does not imply that response conditioned mean correct and error times must be equal. For two fixed stimuli and a fixed referent it is shown that by controlling values of response thresholds, subjects can produce Receiver Operating Characteristics similar or identical to those predicted by Signal Detection Theory, High Threshold Theory, or Low Threshold Theory.     

Cardiac activity in a simple reaction time task

Twenty subjects, half having high extraversion and the other half having low extraversion scores on the Eysenck Personality Inventory, performed a simple reaction time task in which the warning stimulus was a light and the imperative stimulus was a tone. Beat-by-beat analysis showed significantly different response patterns between the two groups in time of onset, magnitude, and duration of the cardiac responses. The extraversion measures were found to relate to central-nervous-system-strength types and to indicate relative strength of central inhibitory processes, as reflected by cardiac activity.     

Reafference learning in the presence of exafference

Reafference learning has been demonstrated most clearly in the case of position-constancy adaptation in which the only stimulus change is caused by the subject’s own movoment. The present study used the more ecologically representative training situation in which only part of the stimulus change is caused by the subject (reafference), while part of it is caused by an independent source (exafference). The exafference varied the space relation between subject movement and optical movement or the time relation between those two. In both cases, reafference learning was not affected by the exafference, and the subject’s varied training experience resulted in a fixed expected optical movement and a fixed expected time lag.     

Stimulus averaging and the context for judgment

Loudness judgments of stimulus sets composed of four bursts of noise were analyzed for two types of contextual effects: between-set and within-set. Experiment I demonstrated between-set effects for these four-component stimuli; they were shown to be similar to those found in previous work with single stimuli. Experiment 2 tested an averaging model for within-set contextual effects. The results were inconsistent with the model. One interpretation is that there are within-set effects and that these are caused by shifts in the effective range of stimuli. Alternative interpretations attribute the apparent contextual effects either to an averaging of physical values or to an inappropriate scale of judgment.     

An attempt to condition components of urine formation in dogs

Previous research on the renal conditional reflex (CR) has resulted in contradictory data. The work of Bykov with dogs and of Hoferet al. with humans indicated that a renal CR is possible, but the experiments of Corsonet al. and Watt and Gantt with dogs having normal or transplanted cervical kidneys showed no clear-cut renal CR’s. The present work supports the latter finding. Three female mongrel dogs were used. One dog (normal) had an externalized ureter; the other two (experimental) had denervated cervical kidneys (autografts). In 155 days of experiments, the investigators found diuresis to occur only on unconditional stimulus,i.e., only when a dog drank diluted milk (one part milk to four parts water)ad lib.; the dogs drank an average of between 500 and 1,100 ml. No diuresis occurred when 30 ml. of the mixture were given (conditional stimulus). Urinalysis indicated a lack of renal conditioning with respect to the excretion rates and the concentrations of creatinine and electrolytes, except for the sodium concentration in the normal dog’s urine, which decreased on bothad lib and test (30 ml) days; the volume was not affected. Conclusion: Drinking a small quantity of diluted milk as a conditional stimulus did not produce a conditional diuretic response either in the normal dog or in the two dogs with transplanted kidneys.     

Generation of multiple ratio scales with a fixed stitnulus attribute

Psychophysical theories differ in the relative weight given to sensory and cogruuve variables. Two opposing theories are described and tested in an experiment designed to vary a cognitive factor while maintaining a constant sensory factor. The method of magnitude estimation was used with the constant stimulus attribute of line length. The cognitive factor was varied by providing Ss with different feedback concerning the numerical values assigned to the largest and smallest lines in the series. This procedure led to multiple ratio scales for the same stimulus attribute. It is argued that these results support a theory which stresses both cognitive and sensory variables in the explanation of psychophysical functions.     

Odor intensity after self-adaptation and cross-adaptation

Psychophysical functions for the odor intensity of n-propanol and n-pentanol were obtained after no adaptation and after self-adaptation and cross-adaptation. Adaptation caused the psychophysical function to become steeper and generally concave downward in log-log coordinates. Increase in the in tensity of a: self-adapting stimulus produced relatively greater increases in the steepness of the functions than did increases in adapting duration. A comparison between the odorants revealed that propanol and pentanol have equal self-adapting effects when their respective adapting concentrations are matched for subjective intensity. Cross-adaptation had approximately the same effect as self-adaptation on the form of the psychophysical function, but a cross-adapting stimulus of a specified subjective intensity was less effective than a self-adapting stimulus of the same intensity. Adaptation to pentanol caused a larger reduction in the perceived intensity of propanol than adaptation to propanol caused in the perceived intensity of pentanol.