Effects of electrical stimulation of the amygdaloid central nucleus on neocortical arousal in the rabbit.

This study sought to determine whether electrical stimulation of the amygdaloid central nucleus (ACe) produces cholinergically mediated neocortical arousal manifested in the suppression of frontal cortex delta wave (1-4 Hz) activity. Stimulation in both anesthetized and conscious rabbits produced a suppression of delta activity that was accompanied by bradycardia and blocked by cholinergic antagonists. Stimulation of the adjacent putamen did not produce delta suppression, whereas stimulation of the adjacent ventral globus pallidus produced a suppression of shorter duration than that produced by ACe stimulation.

Anatomical and physiological relationships between the anterior cerebellar vermis and the pontine parabrachial nucleus in the rabbit.

The anatomical connections between the midline cerebellum and the pontine parabrachial nucleus (PBN) were investigated in the rabbit using anterograde and retrograde axonal transport techniques. Small injections (20-50 nl) of cholera toxin conjugated to horseradish peroxidase (CT-HRP) or wheat germ agglutinin conjugated HRP (WGA-HRP) into the cortex of the anterior cerebellar vermis resulted in retrograde and anterograde-like label in the PBN. Focal injections of tracer into the PBN resulted in anterogradely labeled processes in the ACV and retrogradely labeled a small, but distinct group of Purkinje cells within the anterior vermis.

The anterior cerebellar vermis: essential involvement in classically conditioned bradycardia in the rabbit.

The effects of lesions of the cerebellum on the acquisition and retention of aversive Pavlovian conditioned bradycardia were examined in rabbits. Lesions of the anterior cerebellar vermis severely attenuated the acquisition of simple conditioned bradycardia without disrupting baseline heart rate (HR), or unconditioned HR responses. Also, lesions of the vermis performed after the acquisition of conditioned bradycardia eliminated evidence of prior conditioning.

Hypothalamic modulation of Purkinje cell activity in the anterior cerebellar vermis.

Intricate anatomical connections exist between the cerebellar vermis and the hypothalamus. This study examined the effects of electrical microstimulation of the hypothalamus on Purkinje cell activity in the anterior cerebellar vermis (ACV) in the awake rabbit. Single-pulse stimulation of the hypothalamus evoked robust, short-latency modifications of Purkinje cell discharge.

Purkinje cell responses in the anterior cerebellar vermis during Pavlovian fear conditioning in the rabbit.

Extracellular single-unit recordings of Purkinje cells in the anterior cerebellar vermis (ACV) of the rabbit found evidence of short-latency (20-30 ms) differential responses to discriminatively-conditioned auditory stimuli during Pavlovian fear conditioning procedures. These differential unit responses appeared to be a function of learning as differential ACV Purkinje cell responses were not observed in naive (untrained) animals. Some of these evoked neurophysiological responses were also correlated with the behavioral conditioned autonomic response.

Medial cerebellum and long-term habituation of acoustic startle in rats.

Three experiments assessed the effects of damage to the medial cerebellum on long-term habituation (LTH) of the acoustic startle response. Experiment 1 replicated previous results. Lesions of the cerebellar vermis blocked LTH without affecting initial response levels or short-term habituation (STH).

Lesions of the cerebellar vermis and cerebellar hemispheres: effects on heart rate conditioning in rats.

The effects of lesions of the cerebellum on the acquisition of heart rate (HR) conditioned responses (CRs) were examined in rats. Large lesions of the cerebellar vermis severely attenuated the acquisition of differentially conditioned bradycardic responses in restrained rats without affecting unconditioned HR responses to the tone conditioned stimuli (CSs) or the shock unconditioned stimulus (UCS). In a second experiment, rats were trained unrestrained, and under these conditions the CR was tachycardia in control animals.

Cerebellar vermis: essential for classically conditioned bradycardia in the rat.

The effects of lesions of the cerebellar vermis on the acquisition of heart-rate conditioning in rats was examined. Lesions of the vermis severely attenuated the acquisition of conditioned bradycardic responses in a simple conditioning procedure in restrained rats. Importantly, the vermal lesions did not affect resting heart-rate, unconditioned heart-rate orienting responses to a tone stimulus or unconditioned heart-rate responses to the shock unconditioned stimulus.

Response characteristics of neurons in the medial component of the medial geniculate nucleus during Pavlovian differential fear conditioning in rabbits.

Recent evidence suggests that the amygdaloid central nucleus (ACE) may contribute significantly to Pavlovian fear-conditioned bradycardic responses during the presentation of conditioned emotional stimuli. Because the medial component of the medial geniculate nucleus (MGm) is a major source of input to the region of the ACE, the extracellular single-unit responses of MGm neurons were examined during Pavlovian differentially conditioned bradycardic responding in rabbits. Conditioning involved pairing one tone (CS+) with paraorbital shock and presenting another tone (CS-) in the absence of shock.

Effects of lesions of the cerebellar vermis on VMH lesion-induced hyperdefensiveness, spontaneous mouse killing, and freezing in rats.

In a series of independent experiments, we showed that lesions of the vermis of the cerebellum in rats blocked the hyperdefensiveness induced by lesions of the ventromedial hypothalamus (VMH), attenuated spontaneous mouse killing, and reduced unconditioned freezing and other signs of fear in the presence of a cat. The vermal lesions did not significantly affect foot-shock conditioned freezing. Control lesions of the cerebellar hemispheres did not affect VMH lesion-induced hyperdefensiveness or freezing in the presence of a cat.

Effects of cerebellar vermal lesions on species-specific fear responses, neophobia, and taste-aversion learning in rats.

The cerebellar vermis has extensive anatomical connections with many brain stem and forebrain structures which have been implicated in emotional or affective behavior. Previous reports indicate that lesions of the vermis in a variety of experimental animals result in altered emotional behavior. The studies reported here attempted to clarify the nature of the change in emotional behavior following vermal lesions in rats by testing the animals in a variety of fear-eliciting situations.

Cerebellar vermis: essential for long-term habituation of the acoustic startle response.

The acoustic startle response in rats shows both short-term habituation, which recovers in seconds or minutes, and long-term habituation, which is effectively permanent. Lesions of the cerebellar vermis significantly attenuated long-term habituation without affecting the short-term process or altering initial response levels. In this response system the cerebellar vermis is part of an essential circuit for long-term habituation.