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Statistical evaluation of several aspects concerning the oscillation effect
Abstract
Previous experiments using a sequence of alternating unilateral stimulations of the amygdalae indicated an “oscillation effect”, i.e., consistent low-latency values for convulsions elicited from one amygdala and consistent high-latency values for convulsions elicited by stimulation of the contralateral amygdala. The present study was concerned mainly with statistical evaluations of the reliability of oscillation events. Tests of the randomness of the observed primary and secondary oscillation patterns indicated that oscillation patterns were significant systematic ones in latency, criterion, and duration data, with the greatest frequency of oscillation occurring in the latency measure. Although there was no significant difference in the frequency of primary or secondary oscillation using chi-square methods, an analysis of variance trend analysis indicated that the primary oscillation pattern (low values on primary side) was the predominant one when considered over the total sample, 139 rats. Also, it was shown that the behavioral pattern (oscillation, nonoscillation) appears not to be related to the number of trials to reach the criterion of six convulsions. The exact basis for oscillatory behavior is unknown. However, for a number of reasons, it appears to be based probably on transfer and interference effects between the primary and secondary brain sites.
... The oscillation tendency in latency data has been remarkably resistant to a number of experimental manipulations. The exact basis for the oscillation is not certain, but it is assumed to be due to transfer and interference effects between the two amygdalae (Gaito, Nobrega, & Gaito, 1978;McIntyre & Goddard, 1973). ...
Previous experiments with the kindling paradigm involved a sequence of alternating unilateral stimulations of the amygdalae, and an “oscillation effect” was observed, that is, consistent low-latency values for convulsions elicited from one amygdala and consistent high-latency values for convulsions elicited by stimulation of the contralateral amygdala. In the present study the effect of site of placement of electrode was investigated in two experiments to evaluate the possibility that the oscillation tendency is due to the differential placement of the two electrodes. In two groups of rats, one electrode was placed in the amygdala and the other in the dorsal caudate-putamen. In Group 1 stimulation of the caudate-putamen came first; in Group 2, stimulation of the amygdala occurred in the initial phase. In a third group both electrodes were placed in the amygdalae. Oscillation patterns occurred in the three groups in the two experiments but not in the pattern suggested by the differential placement hypothesis. These results reinforce previous findings indicating that site of electrode placement is not the basis for the oscillation effect. The behavioral pattern observed during the development of kindling with caudate-putamen stimulation was strikingly different from that found with the amygdala: a sharp pull of the head in the ipsilateral direction and spastic jerks of the forepaws upon the onset of stimulation. With termination of the current, this behavior ceased. During the development of kindling, this behavioral pattern was partially or completely displaced as kindling behavioral stages became prominent.
There are three types of interference effects during kindling: that produced by alternate stimulation of homologous brain sites, by successive stimulation of one site, and by stimulation of one site by different frequencies. These three types of interference appear to be similar. Facilitation and interference effects during kindling seem to be generated by the operation of two factors: a “neurological trace” process, possibly involving synaptic changes, and an “aftereffect.” The latter process may be the main basis for these interference effects.
Previous research indicated that an oscillation effect resulted during sequential alternation of unilateral amygdaloid stimulation with consistently low latency values for one side and consistently high values for the contralateral one when 30 sec was the duration of stimulation. In the present experiment, stimulation was for 5 sec. The oscillation tendency was the same with 5 sec duration as it had been with 30 sec.
Previous research indicated that an oscillation effect resulted during sequential alternation of unilateral amygdaloid stimulation with consistent low-latency values for one side and consistent high values for the contralateral one. In this study only one trial of stimulation was applied before alternating to the opposite side. The oscillation tendency resulted under this condition in a similar fashion as in previous studies in which stimulation was continued with one side until six convulsions occurred.
Data from a number of sequential alternation experiments for 125 subjects were factor analyzed to determine the number of common factors present. Three measures (mean latency of convulsion, mean number of trials to, six convulsions, mean duration of convulsions) were evaluated by principal components analyses. The presence of two factors was suggested in the latency, criterion, and duration measures (primary site stimulation, secondary site stimulation). The two factors were more clearly defined for the latency data than for the other measures. Further analyses with individual trials (rather than means) for the 125 subjects provided approximately the same results. Factor analyses of data from 35 rats stimulated only on one side showed the presence of one factor in all analyses. These results suggest a two-factor interpretation of kindling events, possibly the two effects of Goddard et al. and McIntyre and Goddard: a long-term neurological circuitry modification for each of the primary and secondary sites and a short-term aftereffect which accounts for the negative-transfer aspects from the primary to the secondary site.
Previous research indicated that an oscillation effect resulted during sequential alternation of unilateral amygdaloid stimulation with consistent low-latency values for one side and consistent high values for the contralateral one. One possible basis for this effect is that one of the two sides naturally has a greater reactivity to the stimulating current. This hypothesis was evaluated in this study. One group of rats had the usual alternation of stimulation from one side to the other over 10 phases of six convulsions each. A second group received five consecutive phases of stimulation of the primary site and then five consecutive phases for the secondary side. If the hypothesis were true, the latency values for one side would be consistently lower (or higher) than those for the phases on the other side; this result did not occur, although significant oscillation patterns were prominent with the alternation group. These results tend to suggest that differential natural reactivity of the two sides is not the basis for the oscillation effect.
Previous research with the kindling paradigm indicated that an oscillation effect resulted during sequential alternation of unilateral amygdaloid stimulation with consistently low values for one side and consistently high values for the contralateral one. The effect of interphase intervals of 1 and 14 days following (Experiment 1) and during (Experiment 2) the development of oscillation was investigated in this study. In Experiment 1 both the 1-day and 14-day intervals disrupted the oscillation tendency in criterion data but not in the latency measure. In Experiment 2 disruption of oscillation occurred only for the criterion measure in the 14-day group.
Brain dopamine is known to retard the development of kindled seizures, but it is uncertain whether kindling affects dopamine function. In the present study, rats were screened for cerebral dominance by recording their preferred direction of rotation when injected with d-amphetamine. Bipolar stimulating electrodes were then implanted in the amygdaloid complex of either the dominant or nondominant hemisphere (i.e., respectively, contra- and ipsilateral to the preferred direction of rotation; the dominant hemisphere identified in this way has been shown to contain higher concentrations of dopamine than the nondominant hemisphere). Kindling stimulation (or sham-kindling, in control rats) was applied through the electrodes two or three times daily for 21 days, and the rats were reassessed for amphetamine- and apomorphine-induced rotation, during and after the course of treatment. Kindling of the originally dominant hemisphere caused a diminution of rotational asymmetry as measured in tests 2 to 3 h after stimulation sessions, and in some rats led to a reversal in the preferred direction of amphetamine-induced rotation. Kindling of the nondominant hemisphere tended to accentuate the original amphetamine-induced asymmetry. The direction of rotation induced by a direct postsynaptic DA-receptor agonist (apomorphine) was not significantly affected by kindling of either hemisphere. It appears that kindling stimulation brings about a relatively inferior level of DA function on the stimulated vs. the nonstimulated side of the brain, and that this process depends mainly on changes occurring at a presynaptic level.
Previous research had indicated that an oscillation effect resulted during sequential alternation of unilateral amygdaloid stimulation with consistent low values for one side and consistent high values for the contralateral one. In the present study with two experiments, stimulation was of a single amygdaloid site over 10 phases of six clonic convulsions. The frequency of oscillation patterns was not greater than that expected by chance in the latency measure, which suggested that the oscillation effect results from the interaction between the homologous brain sites during the kindling process.
Data from a number of sequential alternation experiments were factor analyzed to determine the number of common factors present. Three dependent variables (latency of convulsion, number of trials to six convulsions, duration of convulsions) were evaluated by three procedures: principal components solution with 1s in main diagonals, principal axes solution with largest r in the diagonals, principal axes solution with R2 in the diagonals. The results were similar; the presence of two factors was suggested in the latency and criterion measures (primary site stimulation and secondary site stimulation) and one in the duration data. A principal components factor analysis over the three dependent variables showed the presence of three factors, those observed in each of the separate analyses.
Three groups of rats were subjected to a sequence of stimulations alternating from one amygdala to the contralateral one. Each phase of stimulation was for six convulsions prior to stimulation of the opposite side. Rats in Group 1 were stimulated six times per day; Group 2 rats had three trials each day; and one stimulation each day was provided for Group 3 rats. The oscillation tendency (high values for one side, low values for other side) was prominent with all groups but seemed most prevalent with Group 3 rats.
In two experiments, rats were subjected to a sequence of stimulations alternating from one amygdala to the contralateral one. Each phase of stimulation was for six convulsions prior to alternation to the other side. Rats In Experiment 1 had a series of six or seven phases of alternation, followed by five phases of bilateral stimulation, and concluded with seven phases of unilateral stimulation. In Experiment 2, rats had five phases of bilateral stimulation prior to seven phases of unilateral stimulation. The bilateral phases produced a modest disruption of the oscillation tendency when it was interspersed between two series of unilateral stimulation phases, more so in the criterion measure than in latency data. The effect was less on the oscillation tendency when bilateral stimulation preceded unilateral stimulation phases.
Previous research indicated that an oscillation effect resulted during sequential alternation of unilateral electrical stimulation of the amygdala over 10 phases of six clonic convulsions per phase, with consistent low latency values for one side and consistent high values for the contralateral one (i.e., a fluctuation of low and high values on consecutive phases). In the present experiment 10 rats were stimulated for up to 50 phases. Four of the 10 showed remarkable patterns of oscillation in latency data: One oscillated on every one of 50 phases, two showed oscillation patterns on 48 of 50 phases, and the fourth oscillated on every one of 32 phases.
In two experiments, rats were subjected to a sequence of electrical stimulations alternating from one amygdala to the contralateral one. Each phase of stimulation was for six convulsions prior to alternation to the other side. An oscillation effect resulted, involving low trials to six clonic convulsions and low latency to convulse for stimulation of one side, but high values of these measures for the contralateral site. The oscillation persisted, especially for the latency measure, even when one phase of bilateral stimulation preceded unilateral stimulation, when a 17- to 23-day rest period was inserted following a sequence of alternations and when two phases of bilateral stimulation occurred following postrest unilateral stimulations. The oscillation effect was less prominent in the number of trials to six convulsions data and almost nonexistent in duration of convulsion. Of 16 rats used in 15 to 19 alternating phases, 7 oscillated throughout all of these phases in latency data, but none showed oscillation over all phases in the other dependent variables.
Eighteen experiments pairing the transfer experiment with the kindling paradigm were conducted. The brain homogenate supernatant from rats kindled to clonic convulsions was injected intraperitoneally into naive recipients. Similar material from nonkindled rats was injected into other naive recipients. One, two, two and one-half, and three brain amounts were used. Recipients receiving supernatant from kindled animals were retarded significantly in the development of clonic convulsions for all brain amounts. No clear retardation effect was obtained if the supernatant was injected intracerebrally or if the recipients had reached the convulsion stage.
Five experiments were conducted in which donor rats were kindled to the clonic-convulsion stage, sacrificed, and their brains removed. The brain was homogenized, and the supernatant fraction was injected intraperitoneally into recipient experimental rats, who then were subjected to the kindling procedure. Control donors which received no stimulation were included. When the injection involved two or more brain amounts, a retarding effect tended to occur with the experimentals. If only one brain amount was used for the injection, no change resulted in the kindling rate of these recipients. This interanimal negative-transfer effect appears to be similar to the intraanimal negative-transfer effect reported by Mclntyre and Goddard.
Previous research had indicated that an oscillation effect resulted during sequential alternation of unilateral amygdaloid stimulation with consistently low latency values for one side and consistently high values for the contralateral one. The effect of intensities approximately 15 microA above threshold was investigated in this study. The oscillation tendency occurred at these near-threshold intensities both for rats which previously had shown oscillation patterns at different intensities and for those which were being stimulated for the first time.
In 2 experiments, a total of 25 aged Wistar male rats (approximately 420-475 days old) were subjected to stimulation of each amygdala in an alternating sequence. Their behavioral response to this stimulation was similar to that found previously with younger rats, systematically going from normal exploration, to automatic behavior, to clonic convulsions. Results also show the "oscillation effect," i.e., low values in latency when stimulated on one side and high values when stimulated on the opposite side. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
This book was prepared as a text for a graduate-level course at the State University of Iowa, taken principally by students of experimental psychology. The course, carrying the same title and having about the same scope as the book, was an outgrowth of the common observation that most graduate students of psychology are initially unable to digest theoretical and experimental papers containing anything beyond the most elementary of mathematical formulations. The book, although loaded with mathematical proofs, rules, and formulas, should not be regarded as a likely substitute for any regular text in mathematics. It is not the equivalent, for example, of an elementary text in calculus. It was not intended to be. The amount of straight mathematics included, as well as the kind, especially the sampling from calculus, was determined by the over-all aim of both the course and the book-to provide the student with enough information to enable him to begin using mathematical procedures in his scientific ventures and to whet his appetite for further knowledge of mathematics. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Previous research indicated that sequential alternation of stimulation of certain homologous brain areas via chronically implanted electrodes resulted in oscillation of high and low latencies for convulsions. This phenomenon suggested the establishement of interhemispheric facilitatory-inhibitory effects as a result of repeated stimulation of the two brain sites. In the present study, the latency oscillation pattern was observed in split-brain rats as well as in bilaterally stimulated controls, but not in rats stimulated on one side only. Significant differences were observed between split-brain and control rats in terms of initial kindling rates, duration of convulsions and type of oscillation. Results are discussed in the context of possible interhemispheric mechanisms involved in long term kindling.
Rats were subjected to varying degrees of commissurotomy, followed by implantation of a bipolar electrode into each amygdala. After the kindling of six convulsions at one electrode (primary site), the procedure was applied to the contralateral amygdala (secondary site). Convulsions were observed to develop more rapidly, independent of the degree or kind of transection. After 6 secondary site convulsions, the primary site was re-tested and convulsion-triggering was blocked, except in animals with transection of the rostral portion of the corpus callosum (CC).
Collectively, the data indicate: (i) amygdala kindling develops a lasting trace which operates through the midbrain or brainstem; (ii) kindling from a second site utilizes this trace; (iii) a series of 6 convulsions produces negative after-effect which manifests itself at the convulsion level via the anterior CC; (iv) the anterior CC is important in determining the laterality of the forelimb clonus; and (v) the inter-amygdala propagation of after-discharge is blocked by the combined sectioning of the anterior CC and the anterior commissure.
Bipolar electrodes were implanted into the amygdala of each hemisphere of adult male rats. A short burst of low-intensity stimulation was applied to one of these electrodes once each day. Initially there was little response. With repetition, epileptiform responses progressively developed until each daily stimulus triggered a behavioral convulsion (kindling effect). Following six convulsions, the procedure was applied to the contralateral hemisphere. Convulsions were observed to kindle more rapidly, especially if a rest interval of 2 weeks followed the last primary site convulsion. When stimulation was reapplied to the primary site, convulsions were not triggered. This was associated with failure to evoke local after-discharge and/or failure of the after-discharge to propagate. Several trials were necessary to re-establish convulsion, unless a 2 week rest preceded testing, in which case convulsions were triggered on the first trial. Following a series of convulsions triggered from either hemisphere, the contralaterally triggered convulsions, when they appeared, showed consistently longer onset lattencies. These latency shifts were attentuated when rest intervals preceded the testing. Latency shifts and seizures failures were not observed if the preceeding series of convulsions was reduced from six to one. Lesions at the tip of either electrode had little effect on the results obtained in the contralateral hemisphere. Together, the results imply that: kindling establishes a lasting trace which is both transynaptic and widespread, kindling from a second location establishes a second trace utilizing parts of the existing trace, a series of convulsions leaves a less durable after-effect with a decay time of about 2 weeks and which interferes with various aspects of seizure activity, and the trace which activates the convulsions is less susceptible to interference from the after-effect.
Brief bursts of nonpolarizing electrical brain stimulation were presented once each day at constant intensity. At first the stimulation had little effect on behavior and did not cause electrographic afterdischarge. With repetition the response to stimulation progressively changed to include localized seizure discharge, behavioral automatisms and, eventually, bilateral clonic convulsions. Thereafter, the animal responded to each daily burst of stimulation with a complete convulsion. The effect was obtained from bipolar stimulation of loci associated with the limbic system, but not from stimulation of many other regions of the brain. Parametric studies and control observations revealed that the effect was due to electrical activation and not to tissue damage, poison, edema, or gliosis. The changes in brain function were shown to be both permanent and trans-synaptic in nature. Massed-trial stimulation, with short inter-burst intervals, rarely led to convulsions. The number of stimulation trials necessary to elicit the first convulsion decreased as the interval between trials approached 24 hours. Further increase in the inter-trial interval had little effect on the number of trials to first convulsion. High-intensity stimulation studies revealed that the development of convulsions was not based simply on threshold reduction, but involved complex reorganization of function. Experiments with two electrodes in separate parts of the limbic system revealed that previously established convulsions could facilitate the establishment of a second convulsive focus, but that the establishment of this second convulsive focus partially suppressed the otherwise permanent convulsive properties of the original focus.
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