Direct observation and automated scoring of the activity of active and inactive inbred mouse strains

Inbred mouse strains previously found to be low (A/J) and high (C57BL/6J) in open-field activity were tested in a plastic oval runway while their runway activity was directly observed and also monitored by a contact switch recording device. The activity of active C57BL/6J mice was accurately monitored by the recording device, but scores of inactive A/J mice were inflated by a factor between 2 and 3 X. Activity differences between strains were consistently maintained[during repeated tests under both high and very dim illumination if direct observational scores were used. Utilization of scores obtained by the automated recording device resulted in a failure to obtain group differences under the condition of dim illumination. These results were directly related to the mode of locomotion of the two mouse strains.     

Interocular non-independence

Binocular interaction was studied by presenting a different letter form to each eye via a dichopic tachistoscope. The two dissimilar letters were presented simultaneously or at short delay internals of 0–200 msec and were either presented on corresponding or non-corresponding retinal areas. At delay internals of less than 100 msec stimulation of corresponding areas resulted in identification performance below that to be expected on the basis of independent chances to perceive. Stimulation on non-corresponding areas resulted in both presented letters being identified at the accuracy level predicted by an independence assumption.     

Motivated changes of auditory sensitivity in a simple detection task

Recently both neurophysiological and psychophysical theories have suggested that the sensitivity of receptors, or of the whole organism, may change through “efferent control” or as a result of “motivation.” A psychophysical method has been devised to investigate changes in a listener’s ability to detect signals in a noisy background, which are elicited “on demand” by the E, and when the time course of the changes may be in the order of seconds rather than minutes orhours. Observed effects, which are consistent with the hypotheses of active control of sensitivity, are found to be orderly but quite small, generally less than that associated with a 1–2 dB increase in the level of a tonal signal. While the average increment in performance is thus slight, it is found that the variance between Ss is significantly reduced when strong motivating stimuli are introduced. This reduction in variance may reflect an upper limit on the performance of real listeners, which might be fruitfully compared with the theoretical limits proposed in the theory of signal detectability.     

Use of Control Groups in Studies of Guidance

Problems in the interpretation of results of studies in which control groups are used are illustrated in a follow-up study. Subjects who had been counseled over a four-year period at the Research and Guidance Laboratory for Superior Students at the University of Wisconsin were followed up four years after high school graduation and their performances were compared with those of the members of a control or comparison group. The results are presented and the adequacy of the control group technique is discussed. The validity is questioned of the commonly accepted procedure of selecting control group subjects on the basis of their current comparability with experimental subjects without adequate history of their development toward that status.     

Cerebral evoked responses in schizophrenia

Results of previous studies of evoked responses in schizophrenic disorders are reviewed, and data from a new study of somatosensory recovery functions in schizophrenia are presented. Subjects in the latter study were 18 schizophrenic patients and 18 nonpatients matched for age and sex. Latencies and amplitudes of eight consecutive evoked-response peaks were measured. Only one amplitude and one latency of the response to the first stimulus discriminated between patients and controls, whereas four amplitudes and three latencies of the second response did so. Amplitude recovery was less in patients, whereas latency recovery was greater. The data verified previous findings of impaired amplitude recovery in schizophrenia, but did not confirm previous findings of increased amplitude in response to a single stimulus. Evoked-response deviations so far determined are not specific to schizophrenic disorders, inasmuch as they have been found in several other psychiatric syndromes. The data are in accord with the idea that psychiatric disorders involve deviant cerebral processing of sensory information.     

Warm and cool thresholds as a function of rate of stimulus temperature change

Ss lifted three weights in sequence with instructions to judge the average heaviness of the weights. In agreement with previous work, a recency effect was obtained, with the later weights having more influence on the judgment. In contrast to previous work, a discrepancy was found from predictions based on the hypothesis that the judgment was an average of the felt heavinesses of the weights. The discrepancy had the appearance of a response end-effect, and was eliminable by a scaling procedure based on functional measurement.     

Attention and auditory evoked responses to low-detectability signals

Comparisons were made between cortical evoked responses obtained under two conditions: (1) while Ss were reading, and (2) while they were attempting to count auditory signals. The amplitudes of evoked responses to low-detectability auditory stimuli were found to be approximately doubled when the Ss were required to count the number of stimuli, as compared to amplitudes recorded when they were reading. The duration of the response was also markedly increased. These increases in response amplitude and duration are considerably greater than those observed in earlierexperiments, where high-levelsignalswere used. Inter-S variability of the waveform of the averageevoked response was observed to be much less when the Ss counted the stimuli. In another experiment the level of the auditory signalwas varied over a range of approximately +4 to -4 decibels relative to the listeners’ behavioral thresholds. The per cent of signalswhich they counted varied from near-zero to 100, over this range, and the evoked response concurrently showed a variation from “unmeasureable” to approximately 8 microvolts.