G. Amato

The importance of the caudate nucleus in the control of convulsive activity in the amygdaloid complex and the temporal cortex of the cat

Abstract In cats in acute preparation and in cats with chronically implanted electrodes, an investigation was carried out of the effects of caudate nucleus stimulation on intrastimulatory (ID) and post-stimulatory (AD) focal paroxysmal activity in the amygdala and in the temporal cortex. 1. 1. The ID of the ventro-basal complex of the amygdala is greatly reduced by activation of the ipsilateral caudate. When the ID does not exceed 250 μV it is generally totally suppressed. Also the ID of the temporal cortex is inhibited by conditioning stimulation of the caudate-nucleus. 2. 2. The convulsive AD, both in the ventro-basal complex of the amygdala and in the temporal cortex, is suppressed by caudate nucleus stimulation. The optimal parameters of stimulation were studied. 3. 3. Inhibitory effects are present only when conditioning stimulation of the caudate nucleus immediately precedes the test stimulus capable of eliciting the amygdaloid or temporal AD. When caudate nucleus activation follows amygdaloid activation, there is an increase in convulsive activity. 4. 4. In animals with chronically implanted electrodes effective stimulation of the amygdala elicits behavioural phenomena comparable with those of psychomotor epilepsy in man. Conditioning stimulation of the caudate nucleus reduces the animal to a state of immobility without any epileptic manifestations. 5. 5. The potentials elicited in the amygdala and the temporal cortex are inhibited by short duration, high frequency conditioning stimulation of the ipsilateral caudate nucleus. 6. 6. The effects of the inhibitory activity of the caudate nucleus on focal paroxysmal phenomena in the limbic system are discussed.

Relationship between the striatal system and amygdaloid paroxysmal activity.

Abstract To study the anatomic pathways through which neostriatal efferent fibers may influence paroxysmal activity focalized in the amygdala, an experiment was carried out both in acute and in chronic cats. Conditioning stimulation of the globus pallidus and substantia nigra greatly reduced the duration of the afterdischarge (AD) or totally blocked the appearance of the seizure, depending on the stimulus parameters. Caudate conditioning stimulation, conducted with the same parameters as nigral or pallidal activation, was less effective in the control of the AD. Chemical lesion of entopeduncular neurons by means of kainic acid injection, resulted in a decrease of about 50% of the inhibition induced by the caudate nucleus on the amygdaloid AD, whereas kainic acid lesion of the substantia nigra resulted in the disappearance of the caudate inhibition. The essential role of the substantia nigra in the final control of amygdaloid paroxysmal activity is thus emphasized.

The role of the substantia nigra in the control of amygdaloid paroxysmal activity

Both in acute and chronic cats focal paroxysmal activity evoked in the ventro-basal complex of the amygdala has been inhibited by substantia nigra conditioning stimulation, to a greater extent, than by caudate nucleus activation. Injection of kainic acid into substantia nigra resulted in the disappearance of the caudate inhibition. It is suggested that the final control, exerted by the striatum on the amygdaloid seizures, occurs by means of the substantia nigra.

The control of amygdaloid seizures by the globus pallidus

Both in acute and chronic cats entopeduncular stimulation inhibits, to a greater extent than caudate activation, focal paroxysmal activity in the ventro-basal complex of the amygdala. Lesion of entopeduncular neurons, by means of kainic acid injection, induces a decrease of the caudate inhibitory effect. It is suggested that neostriatal control of the amygdaloid seizures occurs partly through the globus pallidus.

Effects of motor cortex removal on circling behaviour

AbstractChemical stimulation of the dopaminergic nigro-striatal system induces circling behaviour also in animals in which an extensive telencephalic lesion has been performed. In order to avoid the effects linked to chemical stimulation, we have studied the circling behaviour means of electrical stimulation of the caudate nucleus in chronic cats with cortical lesions. The role of the motor cortex on the circling behaviour is emphasized.

Modifications of the spontaneous bioelectric activity and of the after discharge evoked in the amygdala after pallidal injection of kainic acid in the cat.

Publisher Summary This chapter explains the modifications of the spontaneous bioelectric activity and of the after discharge (AD) evoked in the amygdala after pallidal injection of kainic acid (KA) in the cat. An experiment was conducted in which injection of KA, a neurotoxic drug analog of glutamate, was made into the entopeduncolar nucleus (EN), the equivalent of the medial globus pallidus of primates, to observe the modifications produced on the spontaneous amygdaloid bioelectric activity and on the evoked AD. An AD was evoked in the amygdala by stimulation of the ipsilateral pyriform cortex. The duration of the amygdaloid AD was related to the stimulus parameters. In the same animal, the AD duration did not greatly change when stimulation parameters remained constant. Stereotaxically microinjection of KA was effected in the EN ipsilateral to the amygdaloid deriving electrodes. Few minutes after the injection of the drug, a decrease of the AD duration was observed likely linked to the excitatory effect of KA on the EN neurons that increased its inhibitory effect on the amygdaloid complex. The results of the experiment contribute to underline excitatory effect and subsequently damaging of KA on EN neurons allowing one to confirm a control role of the globus pallidus on the spontaneous and evoked paroxystic amygdaloid activity.

Contralateral potentials in the suprasylvian gyrus evoked by pulvinar stimulation.

AbstractIn encephale isole cats the transmission of the bioelectrical activity in the suprasylvian gyrus, evoked by contralateral pulvinar stimulation was explored. Through the excitability increase and decrease of the pulvinar (by strychnine or KCl, respectively), the surgical removal of the ipsilateral suprasylvian gyrus and the electrocoagulation of the posterior commissure it appeared that the transmission of the activity in the suprasylvian gyrus evoked by contralateral pulvinar stimulation occurs through both the callosal and the interthalamic pathway.

Modifications in Evoked Activity in the Visual Cortex Induced by the Caudate Nucleus

The visual system, like the other sensorial systems, is subjected to intrinsic, complex control, originating both in the retina (CHANG et al., 1959; ARDUINI and HIRAO, 1960; STERIADE, 1967) and in the visual cortex (BUSER et a/., 1963; JASSIK-GERSCHENFELD and ASCHER, 1963; MEULDERS, 1965), which regulates its input at various levels of the specific pathways. However, the visual system is also influenced by subcortical structures which, though not exerting on it a strictly selective control, determine notable modifications in the level of excitability of the cortical sensorial neurons. It is in fact we11 known that activation of the mesencephalic reticular formation, by increasing the level of cortical excitability, produces a facilitation of the potentials evoked in the visual cortex (BREMER and STOUPEL, 1958 and 1959; DUMONT and DELL, 1958 and 1960; BREMER et al., 1960; FUSTER, 1961; FUSTER and DOCTER, 1962). On the other hand, electrical or chemical stimulation of the ventral pontine reticular formation inhibits the potentials evoked in the specific areas of the cerebral cortex and chemical inactivation of the same pontine area causes their facilitation (COURVILLE et al., 1962; DEMETRESCU and DEMETRESCU, 1962b). Again referring to subcortical control of the sensorial afferences, there is however the more recent demonstration of an inhibitory action by the caudate nucleus on activity evoked in the areas of specific projection (DEMETRESCU and DEMETRESCU, 1962a; DEMETRESCU et al.,