Facilitation of seizures in limbic epileptic rats by complex 1 microTesla magnetic fields

On three separate sessions 24 male rats with histories of limbic epilepsy were exposed to 10 temporal configurations for 5 min. each of one of two patterns of magnetic fields. Their intensities averaged about 1 microTesla (microT). The numbers of Level 5 (Racine) seizures, inferred by the rat's rearing, rapid forelimb clonus, and falling, were statistically more frequent for the frequency-modulated (Thomas) pattern when its pixel duration and interstimulus presentation were 3 msec. The effectiveness of this temporal configuration was replicated in a second within-subjects experiment (n = 9) that directly compared the numbers of seizures during exposures to each of the two patterns and to a sham-field. These results suggest that brains with sensitive limbic systems might respond to weak magnetic fields, generated from multiple overlapping fields from communication and computer systems whose temporal derivatives emerge as complex sequences with pixel durations within the millisecond range.     

Geophysical variables and behavior: XCI. Ambulatory behavior in rats following prenatal exposures to complex magnetic fields designed to interact with genetic expression

A total of 45 litters were exposed during their entire prenatal development to one of two complex patterns of magnetic fields whose strengths varied within one of four intensity ranges between 10 nT and 1,000 nT or to sham-field conditions. The litters exposed to the most complex pattern, composed of 50 200-msec. presentations of different pulses for 10 sec. every 50 sec., displayed more ambulation in an open field at 21 days of age than the litters that had been exposed continuously to a repetitive frequency-modulated field or to sham-field conditions. This treatment explained 25% of the variance in the numbers of squares traversed. The results suggest that complexity of the applied magnetic field during prenatal development may be more important than intensity for permanently affecting neuronal organization and behavior.     

Ranking of stimuli that evoked memories in significant others after exposure to circumcerebral magnetic fields: correlations with ambient geomagnetic activity

To identify means to enhance the laboratory production of alleged paranormal phenomena, 15 pairs of men and women involved emotionally were tested by male and female experimenters who were not familiar with the hypothesis that ambient (geomagnetic) activity could modulate this production. While the female of the pair was exposed to six different patterns of complex magnetic fields designed to affect states of consciousness, the male wrote his reminiscences about shared experiences evoked by a postcard randomly selected from a collection of five. Increased global geomagnetic activity (k values between 0 and 5) at the time of the experiments was significantly and moderately correlated with the more accurate ranking of the stimulus cards. These results were similar to those of a previous study. We suggest that alleged paranormal phenomena involve processes that might be produced by experimentally altering the electroencephalographic correlates of consciousness with circumcerebral applications of counterclockwise weak magnetic fields. However, these processes may be enhanced if global geomagnetic activity is increasing during the periods of exposure.     

Preference, familiarity, and recognition after repeated brief exposures to random geometric shapes

Repeated one-millisecond exposures to random polygon targets have been shown to result in preference for the target shapes over similar distractor shapes in the absence of recognition (Knust-Wilson & Zajonc, 1980). Seamon, Brody, and Kauff (1983a) interpreted this preference-without-recognition effect in terms of a two-process model of recognition memory. The present set of experiments tested three predictions of the two-process model: Target discrimination equal to that found in the preference task should also occur when subjects make familiarity judgments; recognition performance should improve if the target stimuli are presented and tested with an easily encodable visual context; and both preference and familiarity judgments should be unaffected by manipulations of context. The results supported all three predictions. The implications of the results for a competing model proposed by Zajonc (1980) are also discussed.     

Integration of cardiac responses to serial stimuli after Pavlovian conditioning in rats

The expression of cardiac responses to sequences of two sounds was studied in restrained rats following discriminative trace or delay conditioning. Stimuli paired with a tail shock 10 sec later (CS1) elicited conditioned bradycardia. Unpaired or neutral stimuli (CS0) elicited mostly tachycardia. Rats did not learn to suppress responding to nonreinforced sequences with an interval of 6 sec between sounds. Responses to the second stimulus were significantly augmented following a CS1 stimulus, but not following a CS0 stimulus. Real-time summation of simple responses provided a more complete and quantitative prediction of dual responses than did resetting or facilitation. These results extend the time range over which summation may be observed from less than 2 sec to at least 16 sec. They appear to be inconsistent with models involving competition between unitary representations of stimuli in short-term memory and suggest the existence of multiple stimulus traces with independent time courses.     

Fixed-ratio and variable-ratio schedules of brief stimuli in second-order schedules of matching to sample

Eight pigeons matched to sample under second-order schedules of food reinforcement. Under fixed-interval unit schedules, the first correct match to occur after a given period of time was followed by the presentation of a brief stimulus. The termination of the last fixed-interval unit schedule was followed by food according to second-order fixed-ratio and variable-ratio schedules. In Experiment 1, as the number of fixed-interval unit schedules increased, long pauses occurred under the second-order fixed-ratio schedules, but not under the variable-ratio schedules. The similarity of performance measures such as local rate and accuracy indicated that the differences engendered by these two types of schedule are in the duration of the periods of not-responding. In Experiment 2, the addition of a brief stimulus at the end of each unit schedule in chained schedules that had different discriminative stimuli present for the duration of each unit did not substantially affect the performance, and long pauses continued to occur. However, few long pauses occurred under schedules with brief stimulus presentations alone. The most inaccurate performances were engendered by chained schedules without brief stimuli.     

Burying by rats in response to aversive and nonaversive stimuli

Previous investigations have shown that rats bury a variety of conditioned and unconditioned aversive stimuli. Such burying has been considered as a species-typical defensive reaction. In the present studies, rats buried spouts filled with Tabasco sauce, or condensed milk to which a taste aversion was conditioned, but did not bury water-filled spouts or spouts filled with a palatable novel food (apple juice) to which a taste aversion was not conditioned. However, in other experiments rats consistently and repeatedly buried Purina Rat Chow, Purina Rat Chow coated with quinine, and glass marbles. This indicates that a variety of stimuli, not all aversive or novel, evoke burying by rats. Whereas the behavior may reasonably be considered as a species-typical defensive behavior in some situations, the wide range of conditions that occasion burying suggests that the behavior has no single biological function.     

Effects of multiple exposures to D-cycloserine on extinction of conditioned fear in rats

Previous research has shown that an acute, post-training injection of D-cycloserine (DCS) facilitates extinction of conditioned fear in rats; however, the effects of multiple exposures to DCS in this situation are not known. In Experiment 1, rats were conditioned (light-shock pairings) and 24 h later given six extinction (light-alone) trials followed by an injection of DCS (15 mg/kg) or saline. The next day, all rats were tested for light-elicited freezing. In Experiment 2, the effect of DCS on extinction was tested in the same manner, except that rats were pre-exposed to DCS (0, 1, or 5 injections) just prior to conditioning. In Experiment 3, rats received five pre-exposures of DCS but conditioning occurred either 2 or 28 days after the last pre-exposure. The results showed that DCS facilitated extinction of conditioned freezing to the light CS when no drug pre-exposure had occurred, but pre-exposure to DCS just prior to conditioning disrupted the facilitation of extinction effect. When 28 days were interposed between pre-exposure and conditioning, the facilitatory effects of DCS on extinction were restored. These findings suggest that DCS has significant clinical value but that behavioral desensitization may occur with multiple exposures; however, desensitization is not permanent and is reduced by the passage of time.     

Assessing control by elements of complex stimuli in delayed matching to sample.

A series of six experiments examined delayed identity matching-to-sample performances of subjects with mental retardation. The stimuli were either one or two simultaneously displayed forms. When the reinforcement contingencies required that only one form exert discriminative control, all subjects achieved high accuracy scores. However, accuracy scores were substantially lower when the contingencies required discriminative control by two forms, suggesting restricted stimulus control. The decline in matching accuracy appeared to reflect selective losses of conditional control by sample stimuli and shifts in control to features of the comparison stimulus displays. The experiments suggest improved techniques for assessing control by complex stimuli and for evaluating the effects of procedures that seek to broaden restricted stimulus control. The results challenge interpretations based on stimulus-generalization decrement or shared attention.     

Geophysical variables and behavior: XCVII. Increased proportions of the left-sided sense of presence induced experimentally by right hemispheric application of specific (frequency-modulated) complex magnetic fields

12 young men and women who were not aware of the stimulus order were exposed to 8 configurations of weak 1 microTesla) magnetic fields for 5 min. each, applied primarily over the right parietotemporal region. The numbers of sensed presences along the left side, right side, or front/back, as inferred by button presses at the time of the experience, were recorded. There were significantly (eta2= .37) more experiences along the left side than the right side during the presentations of a frequency-modulated (Thomas) pattern with 3-msec. point durations compared to the presentation of its temporally reversed structure or to patterns that were more or less complex. 40% of all left-sided presences occurred during the 5-min. presentation of this specific frequency-modulated pattern. These results suggest that the subjective lateralization of a sensed presence to the left during right hemispheric stimulation by weak magnetic fields is enhanced by the specific temporal structure of the applied field.     

Exposition of visual stimuli in an aversive situation and self-exposure to light in rats

The aim of the work presented was to test the effect of associating visual stimuli with an aversive situation on later self-exposure to these stimuli. Forty-five male albino rats (Wistar) aged approximately 90 days were divided into three groups; visual trained in avoidance response to visual stimuli; auditory trained in avoidance response to auditory stimuli; and neutral untrained in avoidance response. In part two of the experiment all the rats were tested in a chamber for self-exposure to light. A statistically significant increase in the rewarding value of visual stimulation was found in the visual group in comparison with the remaining groups. This effect is interpreted as a result of extinction of anxiety response to visual stimuli as a result of which relaxation begins to positively reinforce the response leading to switching on the light.     

Stimulus factors in aversive controls: conditioned suppression after equal training to two stimuli

Pigeons trained to peck a key for food were periodically presented with tones ending with electrical shock until tone presentation consistently suppressed ongoing pecks. Shock was then discontinued and gradients of stimulus generalization were assessed by presenting tones with frequencies above, below, and at the frequencies of those used to develop conditioned suppression. When the training tones had frequencies at 670 and 1500 cps, resulting gradients were bi-modal with peak suppression at 670 and 1500 cps. Of the other test tones, 1000 cps produced the most suppression. When the training tones had frequencies at 450 and 2250 cps, bi-modal gradients were again obtained with peak suppression to the 450 and 2250 cps tones. Of the other test tones, 1000 cps produced the least suppression. These results support the hypothesis that generalized response tendencies summate.     

The development of attention to simple and complex visual stimuli in infants: Behavioral and psychophysiological measures

The study of visual attention in infants has used presentation of single simple stimuli, multi-dimensional stimuli, and complex dynamic video presentations. There are both continuities and discontinuities in the findings on attention and attentiveness to stimulus complexity. A continuity is a pattern of looking that is found in the early part of infancy that remains throughout adulthood. A discontinuity is an emerging sensitivity to the content of the information in the stimulus presentations and alterations in patterns of attention based upon stimulus comprehensibility. The current paper reviews some of these findings with particular application to complex video presentations.     

Decreased locomotor and investigatory exploration after denervation of catecholamine terminal fields in the forebrain of rats.

Exploratory behaviors were examined after bilateral microinjections of 6-hydroxydopamine into two hypothalamic sites that produced different patterns of denervation of forebrain catecholamine terminal fields. After anterolateral injections rats locomoted and reared less in a novel open field, responded abnormally to changes in the degree of novelty of the open field, and investigated a novel object less. These are deficits in exploratory behavior because they were not secondary to the inhibition of open-field behavior by hyperemotionality, by general motor disability, or by the failure to detect novel spaces or objects. Such anterolateral injections produced loss of catecholamine fibers, determined histochemically, in neocortical, hippocampal, anterolateral hypothalamic, mesolimbic, mesocortical, and anteromedioventral striatal terminal fields and loss of dopaminergic perikarya in the A10 and anteromedial A9 cell groups. No deficits in exploratory behaviors occurred, however, after bilateral anteromedial 6-hydroxydopamine injections that denervated neocortical, hippocampal, and anteromedial hypothalamic catecholamine terminal fields. A critical forebrain catecholaminergic innervation for exploratory responses to novel stimuli may be within areas that were denervated by anterolateral but not by anteromedial hypothalamic 6-nydroxydopamine injections. These areas are mesolimbic, mesocortical, anteromedioventral, and anterolateral hypothalamic terminal fields.     

Studies of instrumental behavior with sexual reinforcement in male rats (Rattus norvegicus): I. Control by brief visual stimuli paired with a receptive female

We describe a novel procedure for measuring instrumental sexual behavior in the male rat by using a second-order schedule of presentation of sexual reinforcement, an estrous female. Experimental assessment and validation of the paradigm have been achieved by examining (a) the importance of the conditioned stimulus in maintaining instrumental responding by measuring the effects of its omission during a test session, (b) the effects and motivational specificity on instrumental behavior of the postejaculatory refractory period (a period of sexual unarousability) and of satiety for food by measuring the impact of each manipulation on animals working for food and for a female, (c) the effects of replacing an estrous female with an anestrous one as the earned reward, and (d) the correlations between conditioned and unconditioned measures of sexual behavior. We conclude that the second-order paradigm provides a means of distinguishing between the effects of neuroendocrine manipulations on incentive motivational and performance variables underlying the expression of sexual behavior.