Effects of aversive and rewarding electrical brain stimulation on auditory evoked responses in albino rat tectum

Auditory evoked responses in rat tectum yielded recovery functions to aversive electrical brain stimulation of either contralateral mesencephalic central gray or deep superior colliculus. Effects of stimulation on inferior colliculus auditory potentials are abolished by pentobartital and curare, implying tympanic muscle mediation due to reticular activation. Brain stimulation effects survive identical pharmacological manipulations when auditory responses are led from deep superior colliculus, showing independence from reticular processes or events occurring in inferior colliculus, one synapse previous. Rewarding brain stimulation also effects deep superior colliculus potentials, but interacts in an undetermined manner with nonspecific processes.     

Acceleration of functional recovery following lateral hypothalamic damage by means of electrical stimulation in the lesioned areas

Mechanical lesions produced by placing chronic macroelectrodes in the lateral hypothalamus resulted in 6 days of aphagia. However, if the hypothalamus was electrically stimulated for 1 hr a day, through the same electrodes, feeding behavior was recovered in just 2 days.     

Autoshaping in the rat with electrical stimulation of the brain as the US

Previous studies with rats have demonstrated autoshaped approach behavior to a Pavlovian CS when the CS was the insertion of an object into the test chamber and the US was food or electrical stimulation (ESB) of the lateral hypothalamus. Our study showed that rats also will approach a stationary light-onset CS that signals stimulation of other brain areas (substantia nigra, amygdala, raphe nucleus) as well. Whenever autoshaping occurred, ESB proved to be operantly reinforcing; this, however, was not a sufficient condition for autoshaping. No major differences in the topography of conditioned responses with different types of ESB were observed.     

Behavior maintained by electrical stimulation of the rat cerebellum

Thirty-two of 53 rats receiving electrical stimulation of the cerebellum (ESC) displayed at least one stimulusbound response, and grooming was the most frequently evoked behavior. In the absence of any special procedures, only 4 animals exhibited any additional oral behaviors. However, 26 other animals that groomed during the stimulation also began to eat, gnaw wood, and/or drink water when goal objects were presented manually. The failure of these stimulated animals to approach goal objects on their own could not be explained by a lack of stimulation experience with relevant goal objects. ESC also inhibited male sexual behavior and eating in food deprived rats. In both these cases, competing responses (usually grooming) were elicited throughout the stimulation interval. Positive, negative, and neutral reinforcing effects were obtained from electrode sites supporting oral behaviors; but other sites yielded only neutral and negative effects. ESC was ineffective in eliciting object-carrying behavior.     

Facilitation of male rat copulatory behavior by electrical stimulation of the medial preoptic area

Lesion studies have demonstrated that the medial preoptic area (MPO) plays a critical role in male rat copulatory behavior. The present study attempted to better localize the neural elements mediating this behavior pattern and to determine the influence of preoptic area stimulation on particular aspects of copulatory behavior. Monopolar stimulating electrodes were implanted in the medial preoptic-anterior hypothalamic continuum or the lateral preoptic-medial forebrain bundle region. The effects of stimulating a particular locus were measured by comparing each animal's behavior on repeated stimulation and control tests. All measures of copulatory activity taken were facilitated by medial, but not by lateral, preoptic stimulation. The most common change produced by MPO stimulation was a reduction in both the number of mounts and intromissions preceding ejaculation. Short-latency approach and mounting of the female and greatly reduced refractory periods were also seen in two MPO animals. No evidence of a post-stimulation inhibition of copulatory behavior resulting from the stimulation itself was seen in these two animals. Most animals in both the medial and lateral groups learned to self-stimulate (SS) using the same 30-sec trains of stimulation as used in earlier tests of copulatory activity. SS rate, stimulation-bound copulation, and degree of facilitation of ejaculation were positively correlated in MPO, but not in lateral preoptic animals.     

An air pressure operated commutator system for electrical brain stimulation in a fighting rat

A five-channel commutator system for electrical brain stimulation in a fighting rat is described. Two air pressure bearings minimize starting torque and revolving mass. A wire-guide prevents entanglement. Detailed instructions for assembling a reliable connector for attachment of the leads to the rat are given.     

Comparison of motor effects following subcortical electrical stimulation through electrodes in the globus pallidus internus and cortical transcranial magnetic stimulation

Current concepts of transcranial magnetic stimulation (TMS) over the primary motor cortex are still under debate as to whether inhibitory motor effects are exclusively of cortical origin. To further elucidate a potential subcortical influence on motor effects, we combined TMS and unilateral subcortical electrical stimulation (SES) of the corticospinal tract. SES was performed through implanted depth electrodes in eight patients treated with deep brain stimulation (DBS) for severe dystonia. Chronaxie, conduction velocity (CV) of the stimulated fibres and poststimulus time histograms of single motor unit recordings were calculated to provide evidence of an activation of large diameter myelinated fibres by SES. Excitatory and inhibitory motor effects recorded bilaterally from the first dorsal interosseus muscle were measured after SES and focal TMS of the motor cortex. This allowed us to compare motor effects of subcortical (direct) and cortical (mainly indirect) activation of corticospinal neurons. SES activated a fast conducting monosynaptic pathway to the alpha motoneuron. Motor responses elicited by SES had significantly shorter onset latency and shorter duration of the contralateral silent period compared to TMS induced motor effects. Spinal excitability as assessed by H-reflex was significantly reduced during the silent period after SES. No ipsilateral motor effects could be elicited by SES while TMS was followed by an ipsilateral inhibition. The results suggest that SES activated the corticospinal neurons at the level of the internal capsule. Comparison of SES and TMS induced motor effects reveals that the first part of the TMS induced contralateral silent period should be of spinal origin while its later part is due to cortical inhibitory mechanisms. Furthermore, the present results suggest that the ipsilateral inhibition is predominantly mediated via transcallosal pathways.This paper is dedicated to Bernd-Ulrich Meyer, who died in a plane accident     

Differential behavioral responsiveness to ipsilateral and contralateral visual stimuli produced by unilateral rewarding hypothalamic stimulation in the rat

Rats were trained to respond to a visual cue signalling availability of brain reward on the left or the right side of a small chamber. Most of the rats began to respond more accurately to the visual cue presented on the side contralateral to brain stimulation than to the ipsilateral cue as the training progressed. The facilitation of the rat's response to the contralaterally presented visual cue was more evident when tested with visual cues presented simultaneously in both ipsilateral and contralateral sides. However, when tested with visual cues removed from both sides, this tendency became unclear. Additionally, monocular training gave evidence of identifying the visual cue ipsilateral to the open eye, irrespective of the electrode side. The results are interpreted as signifying that the ipsilateral hemisphere is activated by the brain stimulus and leads to improved discrimination of the contralateral visual cue because the visual system in the rat is crossed.     

Forelimb and hindlimb stepping by the anesthetized rat elicited by electrical stimulation of the diencephalon and mesencephalon

Thirty rats anesthetized with a combination of chloralose, urethane and nembutal or nembutal alone were fixed in a stereotaxic apparatus and suspended over a moving treadmill belt. Electrical stimulation (100 microA, 10-sec trains, 0.5-msec cathodal pulses, 50-Hz pulse frequency) was applied every 200-microns through 109 movable electrodes. The patterns of stepping elicited ranged from well-coordinated stepping of all four limbs to spastic stepping of only one limb. In the hypothalamus, stepping-positive sites were found in and dorsal to the medial forebrain bundle, the paraventricular, dorsomedial and posterior nuclei, and the supramammillary areas. Dorsally, effective regions extended to the medial zona incerta and the fields of Forel. In the thalamus only the parafascicular nucleus and the anterior parts of the rhomboid and reuniens nuclei were positive. Positive sites were particularly dense in the ventral tegmental area. In the dorsal midbrain positive sites were most common at caudal levels dorsal and dorsolateral to the central gray. At sites in the area of the medial raphe, stepping was elicited only at the offset of the train. The distribution of positive sites resembled that found in unanesthetized rats and indicates that pathways at which electrical stimulation elicits stepping are separated into dorsal and ventral systems at the level of the midbrain.     

A hypothalamic alpha-adrenergic mechanism mediating the thermogenic response to electrical stimulation of the lower brainstem in the guinea pig

Summary Electrical stimulation of the lower brain stem (ESLB) at sites presumed to be parts of the ascending noradrenergic system was carried out in unanaesthetized young guinea pigs. At neutral ambient temperature ESLB elicited a thermogenic response resembling that evoked by microinjection of noradrenaline into the hypothalamus. The response consisted of a rise in oxygen uptake (to more than 50% of the resting value) and of body temperatures, especially of the interscapular adipose tissue. In some cases shivering was also evoked. The thermogenic response to ESLB was completely blocked by additional microinjection of an adrenergic alpha-receptor blocker, phentolamine, into the hypothalamic area where the noradrenergic fibres were presumed to terminate. Subsequent intrahypothalamic injection of noradrenaline, which had formerly been shown to restore the decreased responses to repeated ESLB, failed to restore the effectiveness of ESLB after phentolamine. It is concluded that the thermogenic responses to ESLB are mediated by a noradrenergic pathway ascending to the hypothalamus and not by direct stimulation of efferent pathways controlling the peripheral target system. The hypothalamic transmission can be prevented by an alpha-adrenergic blockade.Supported by the Deutsche Forschungsgemeinschaft SFB 122, Projeckt B 1     

Cerebellar stimulation in the rat: complex stimulation-bound oral behaviors and self-stimulation

An extensive stimulation mapping study of the rat cerebellum was carried out in 82 animals. It was found that complex oral behaviors (eating, grooming, and gnawing) as well as self-stimulation could be obtained from a region including the rostro-ventral anterior lobe vermis, fastigial nucleus, and superior cerebellar peduncle. The behaviors, differing in several respects from hypothalamic-elicited behaviors, appeared only in the presence of the appropriate goal object, thus ruling out simple motor automatisms. The present results suggest that the traditional view of the cerebellar role of improving the coordination of individual muscle movements and posture may need to be expanded. Indeed, the cerebellum may act to facilitate and coordinate complex chains of species-specific behavior patterns.     

Habituation of orienting and motor responses elicited by stimulation of the cortex in the cat

Orienting and motor responses have been elicited by electrical stimulation of the cortex in the unanesthetized, freely moving cat. A total of 73 electrodes from 29 cats was studied. The orienting response was elicited from 56 sites. The response was undistinguishable from that elicited by ordinary sensory stimulation, and no difference was observed in the responses elicited from different cortical areas. Motor responses were observed less frequently. The orienting response showed habituation and dishabituation in all cases except 4. This finding is in agreement with previous work in this area. However, motor responses, with or without accompanying orienting responses, also showed habituation, dishabituation, and even savings from one day to another. Stimulus recognition models [10] seem inadequate to explain our findings for the motor response, but the data are explained by synaptic models of habituation [3].     

Refractoriness of neurons subserving circling following stimulation of the median raphe region in the rat

Five rats implanted with monopolar electrodes immediately lateral to the median raphe (MR) were stimulated with pairs of cathodal pulses (a conditioning or C pulse and a test or T pulse). The stimulation resulted in vigorous ipsilateral circling. The refractoriness of directly stimulated neurons was inferred by the frequency of pulse pairs necessary at each C-T interval to produce a constant amount of circling. The absolute refractory periods (ARPs) of the fastest stimulated neurons were found to be between 0.36 and 0.4 msec. In addition, neuronal elements with ARPs smaller than 1.2 msec contributed for approximately 90% of the behavioral output. It was therefore concluded that circling behavior by stimulation of the MR region involves mainly non serotonergic neuronal elements.     

Development of fetal hypothalamic magnocellular neurosecretory neurons transplanted into the third ventricle of the adult rat brain

Department of Biology, N. I. Pirogov Second Moscow Medical Institute. Department of Biology, Khar'kov Medical Institute. (Presented by Academician of the Academy of Medical Sciences of the USSR V. N. Smirnov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 105, No. 2, pp. 224–227, February, 1988.     

Feeding induced in cats by electrical stimulation of the brain stem

Summary Stimulation at 14 of 106 loci (Figs. 1 and 2) at which electrodes had been chronically implanted elicited immediate feeding in fully satiated, freely moving cats. Half of the effective points were in the lateral hypothalamus and thus agreed with expectations from extensive prior research on the neural organization of feeding behavior. The other points, however, were in the ventral tegmental area or at the ventrolateral boundary of the central gray. The distribution of all effective points could be explained as following a projection pathway from the globus pallidus. Exploration along 162 recording tracks in acute experiments on these same cats revealed no consistent differences in projection of evoked potentials which could distinguish stimulation at effective versus ineffective loci. Potentials of possible significance, however, were evoked in the paramedial nucleus reticularis of the medulla, the rostral pontine nuclei, the nucleus centralis superior of Bekterev, the lateral frontal cortex and the basal medial forebrain in the vicinity of the diagonal band of Broca.Supported by USPHS Grant B 1068. Dr. Wyrwicka held a fellowship from Foundations' Fund for Research in Psychiatry. The authors are indebted to Mr. Joseph Jones and Mrs. Frances Bignall for technical assistance.     

Telencephalic and preoptic areas integrate sexual behavior in hime salmon (landlocked red salmon, Oncorhynchus nerka): results of electrical brain stimulation experiments

Various patterns of sexual behavior were evoked in freely swimming hime salmon by electrical stimulation of specific loci in the telencephalon and the preoptic area (POA) using chronically implanted electrodes. Furthermore, co-ordinated sexual behavior corresponding to stages of the natural spawning sequence was elicited from some of these brain regions. These results suggest that (1) sexual behavior is integrated in specific parts of the telencephalon and POA, and (2) within these regions there is a hierarchy of neural systems which mediate progressively more complete components of normal sexual behavior.     

Behavioral inhibition induced by electrical stimulation of the median raphe nucleus of the rat.

Earlier studies using brain lesions or drugs that impair 5-hydroxytryptamine (5-HT) neurotransmission suggest that the ascending serotonergic system is involved in behavioral inhibition. Confirming this hypothesis, the present study demonstrates that electrical stimulation of the median raphe nucleus (NMR) of the rat induces behavioral inhibition. Rats implanted with brain electrodes in the NMR were trained to lever press under a variable-interval 1 min schedule of water presentation. At variable time intervals averaging 7 min, periods of 90 sec of brain stimulation were superimposed on VI responding without any exteroceptive stimulus change. Electrical stimulation of the NMR caused suppression of ongoing lever-pressing behavior, proportional to the stimulus intensity. In addition, NMR stimulation elicited defecation, also directly related to the stimulus intensity, and a cluster of somatic and autonomic changes, such as crouching, micturition, piloerection and teeth chattering, that are characteristic of the rat's emotional behavior in stressful situations. In four out of six rats, the response-suppressant effect of NMR stimulation was counteracted by the 5-HT synthesis inhibitor, para-chlorophenylalanine (PCPA), three to five days following the administration of a single dose of 500 mg/kg of the drug. The effect of PCPA tended to disappear after fifteen days and in one rat, was reversed by 5-hydroxytryptophan, given after benserazide, on the third day from PCPA injection. These results support the suggestion that the mesolimbic serotonergic pathway originating in the NMR and projecting to the septal area and the hippocampus is a substrate of behavioral inhibition, in the rat.