Optical recording of activity in the hamster gustatory cortex elicited by electrical stimulation of the tongue

Having been informed by the Dean of the School of Dental Medicineat the University of Connecticut Health Center that some ofthe data reported in the above article has been found to befabricated, the Editors of Chemical Senses hereby retract thispaper and discourage citations of it.     

Short-latency unit responses of the lateral geniculate body to electrical stimulation of the optic tract in rats

Short-latency responses of single relay neurons of the lateral geniculate body to electrical stimulation of the optic tract were studied. The response of many neurons was complex and could consist of a series of (1–3) spikes with fixed latent periods. Each spike of such a response can be recorded on the EPSP in the absence of other spikes, preserving its latent period. The fixed latent periods of different relay neurons may vary from one to another. In the intervals between spikes with these latent periods active inhibition (IPSP) takes place. The series of spikes, EPSP, and IPSP is completed, as a rule, by a long IPSP.M. V. Lomonosov Moscow State University. Translated from Neirofiziologiya, Vol. 5, No. 1, pp. 28–32, January–February, 1973.     

Electron microscopy of degeneration in the lateral olfactory tract and plexiform layer of the prepyriform cortex of the rat

Summary The synaptic organization of the plexiform layer of the prepyriform cortex in the rat has been studied with the electron microscope both in the normal and after ipsilateral olfactory bulb removal. Survival times ranged from six hours to three months.In normal preparations synaptic contacts occur mainly on dendritic branches, spines or lateral projections. Gray's Type I contacts are most frequent and Type II contacts usually contain flattened vesicles after formalin fixation.Degeneration of the presynaptic bags begins within 24 hours after the lesion and some degenerated bags are still seen after three months survival. During this time degenerated bags are apparently removed by astroglia but the spine tips appear to be unaffected by the phagocytosis. Glia or other processes may come to occupy the denervated sites. The evidence for possible reestablishment of new contacts is considered.The severed axons show a characteristic mode of degeneration and at three months some appear to be phagocytosed by oligodendroglia which also contain lamellated inclusion bodies.This study represents a part of a thesis accepted in fulfillment of requirements for the degree of Doctor of Philosophy at the University of London (England), June 1966.This investigation was supported in part by a U.S. Public Health Service Fellowship NB 20-844 from the N.I.N.D.S. while the author was a postdoctoral fellow at the Anatomy Department, University College, London, England, and by grants NB 02896 and NB 04053 from the N.I.N.D.S. The author gratefully acknowledges this support and would also like to thank Professors J. Z. Young and E. G. Gray for encouragement and advice throughout the course of this study.     

Receptive fields in the rat piriform cortex.

Current models of odor discrimination in mammals involve molecular feature detection by a large family of diverse olfactory receptors, refinement of molecular feature extraction through precise projections of olfactory receptor neurons to the olfactory bulb to form an odor-specific spatial map of molecular features across glomerular layer, and synthesis of these features into odor objects within the piriform cortex. This review describes our recent work on odor and spatial receptive fields within the anterior piriform cortex and compares these fields with receptive fields of their primary afferent, olfactory bulb mitral/tufted cells. The results suggest that receptive fields in the piriform cortex are ensemble in nature, highly dynamic, and may contribute to odor discrimination and odor memory.     

Thalamic activation modulates the responses of neurons in rat primary auditory cortex: an in vivo intracellular recording study

Auditory cortical plasticity can be induced through various approaches. The medial geniculate body (MGB) of the auditory thalamus gates the ascending auditory inputs to the cortex. The thalamocortical system has been proposed to play a critical role in the responses of the auditory cortex (AC). In the present study, we investigated the cellular mechanism of the cortical activity, adopting an in vivo intracellular recording technique, recording from the primary auditory cortex (AI) while presenting an acoustic stimulus to the rat and electrically stimulating its MGB. We found that low-frequency stimuli enhanced the amplitudes of sound-evoked excitatory postsynaptic potentials (EPSPs) in AI neurons, whereas high-frequency stimuli depressed these auditory responses. The degree of this modulation depended on the intensities of the train stimuli as well as the intervals between the electrical stimulations and their paired sound stimulations. These findings may have implications regarding the basic mechanisms of MGB activation of auditory cortical plasticity and cortical signal processing.     

Optical recording of the odor-evoked responses in olfactory structures of the brain of the terrestrial mollusk Helix

Regular oscillations were recorded in olfactory part of the brain (procerebrum) of gastropod mollusk Helix both electrographically and optically. In general, oscillations resembled those in slugs reported earlier. Odor application caused a transient change in the procerebral oscillations followed by appearance of a special pattern. For the first time the evoked potential was recorded in procerebrum and mapped in reference to the area of oscillations. The area of spreading of evoked potential roughly corresponded to the neuropil projection, while the oscillations were recorded in the projection of the cell body layer of procerebrum. The wave of the evoked potential emerged near the place of the olfactory nerve entrance into the procerebrum and propagated via the procerebrum neuropil towards the cell body layer. The evoked potential did not produce a phase-independent wave in rhythmical oscillations.     

Serotonin-mediated cardiovascular responses to electrical stimulation of the raphe nuclei in the rat.

The dorsal and median raphe nuclei in rats were electrically stimulated and blood pressure and heart rate were recorded. Stimulation of each raphe nucleus caused an increase in blood pressure without affecting heart rate. The size of the increase in blood pressure depended upon the stimulus-intensity.Significant increases were already obtained with 5 sec. trains of 0.3 msec., 200 μA stimuli given at a frequency of 50 Hz. The increases in blood pressure could be obtained with electrodes within the raphe nuclei.Pretreating rats with para-chlorophenylalanine (pCPA, 100 mg/kg.day for 3 days) significantly diminished the increases in blood pressure obtained during electrical stimulation of the median raphe nucleus. However, similar pretreatment did not affect blood pressure rises induced by dorsal raphe stimulation.These data are discussed in relation to the role of central serotoninergic mechanisms in cardiovascular control.     

Cerebral-evoked responses elicited by direct stimulation of the lateral spinothalamic tract in the human

The authors recorded cerebral-evoked responses elicited by direct stimulation of the human lateral spinothalamic tract (LST) during percutaneous cordotomy to investigate central conduction of noxious stimuli. These responses consisted of four negative potentials, peak latency being 3.8 (N1), 8.4 (N2), 12.2 (N3) and 21.9 (N4) ms respectively. N1 showed wide distribution over the scalp and was considered to be of subcortical origin. N2-N4 were distributed in both the temporal and central area. The different distribution pattern of N2-N4 from conventional somatosensory-evoked potential suggested a different projection of LST from the medial lemniscus system.     

Convergence in the piriform cortex

How are the responses to distinct chemical features integrated to form an olfactory perceptual object? In this issue of Neuron, Davison and Ehlers show that individual piriform cortex neurons receive convergent input from up to 10% of main olfactory bulb glomeruli and are activated by specific spatial patterns of coactive glomeruli.     

The late excitatory responses of the motor cortex neurons in the cat to stimulation of the pyramidal tract

Under conditions of partial suppression of GAMKA-dependent cortical inhibition in the motor cortex of anesthetized cats, a weak electrical stimulation of the pyramidal tract evoked the late slow (50-200 ms) excitatory reactions in the motor cortex neurons similar to those previously recorded under the same conditions in response to stimulation of the parietal cortex. This finding favors the proposal that the late excitatory component of the cortico-cortical response reflects the repetitive activation of cortical neurons due to excitation spread via the system of cortical recurrent excitatory collaterals.     

Inhibition of ovulation in the rat by electrical stimulation of the lateral amygdala.

Effects of electrical stimulation of the lateral amygdaloid areas on ovulatory gonadotropin release were examined in adult Wistar female rats. Electrical stimulation was applied in rats in proestrus under ether anesthesia with square wave pulses of 0.5 ms duration and 100 Hz frequency for 30 min (30 sec on and off). Stimulation of the lateral amygdala blocked ovulation in 50% of animals when it was applied between 13:30 and 14:30 with a current of 300 muA. Stimulation of the medial amygdala under the same experimental condition was absolutely ineffective to block ovulation. Sham stimulation was also ineffective. In determining the gonadotropin concentration in serum, the stimulation into the lateral amygdala was observed to inhibit the ovulatory release of LH, FSH and prolactin. It may be said that the lateral amygdaloid area participates in the control of gonadotropin release in an inhibitory manner.     

Effects of electrical stimulation of the human olfactory mucosa

Electrical stimulation of the human olfactory mucosa was performed by means of an electrode attached to a rhinoscope . Stimulation of the nasal mucosa did not evoke smell sensations, but suppressed smell sensations of presented odorants. When electrical stimulation followed the exposure to an odorant within a certain interval, the stimulus recalled the already faded sensation of the preceding odorant. Electrical stimulation without prior natural stimulation produced unpleasant sensations in 3 patients with a history of temporal lobe seizures and olfactory auras , but not in patients with primary, generalized or focal epilepsy.     

Effect of injury to the lateral reticular nucleus and nuclei of the inferior olive on electrical responses of the cerebellar cortex evoked by vagus nerve stimulation in cats

The role of the lateral reticular nucleus and nuclei of the inferior olive in the formation of cerebellar cortical evoked potentials in response to vagus nerve stimulation was determined in experiments on 28 cats anesthetized with chloralose and pentobarbital. After electrolytic destruction of the lateral reticular nucleus, in response to vagus nerve stimulation, especially ipsilateral, lengthening of the latent period and a decrease in amplitude of evoked potentials were observed; after bilateral destruction of this nucleus, evoked potentials could be completely suppressed. It is concluded that the lateral reticular nucleus relays interoceptive impulses in the vagus nerve system on to the cerebellar cortex. Additional evidence was given by the appearance of spike responses of Purkinje cells, in the form of mainly simple discharges, to stimulation of the vagus nerve. After destruction of the nuclei of the inferior olive, the latent period and the number of components of evoked potentials in response to vagus nerve stimulation remained unchanged but their amplitude was reduced. The role of the nuclei of the inferior olive as a regulator of the intensity of the flow of interoceptive impulses to the cerebellum is discussed.N. I. Pirogov Medical Institute, Vinnitsa. Translated from Neirofiziologiya, Vol. 9, No. 3, pp. 290–299, May–June, 1977.     

Unit responses of the sensomotor cortex to paired electrical stimuli

Unit responses of the sensomotor cortex to paired electrical stimulation and visual cortex, applied either simultaneously or after various delays (from 0 to 200 msec) depend on the order of application of the stimuli and on the interval between them. If stimulation of the sensomotor cortex was used in a conditioning role the response continued unchanged when the intervals between stimuli were increased to 200 msec. If, however, stimulation of the sensomotor cortex had a testing role interaction was observed between the stimuli so that responses to both first and second stimuli were blocked; this was exhibited most clearly for intervals of 40–80 msec between stimuli. The blocking effect persisted on some neurons with delays of up to 200 msec between stimuli, while the response of others to both the first and the second stimulus was restored.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 5, No. 6, pp. 628–635, November–December, 1973.     

Evidence for synchronised responses in the piriform cortex by using Gibbs potential analysis

 The piriform cortex is a large paleocortical area which receives direct projections from the olfactory bulb. In order to study the spatiotemporal distribution of the piriform cortex activity, we chose optical recording of the responses evoked by olfactory bulb electrical stimulation. Such a stimulation elicited a large signal corresponding to cortical reactivation (disynaptic activity) via intrinsic association fibres. As the disynaptic activity was observed over the entire piriform area, we wondered whether or not this redistribution contributes to a synchronisation of the activity in the piriform cortex. In order to answer this question, we developed a statistical approach which allows us to take the temporal dimension into account. The analysis was performed by using the Gibbs potential analysis. The neural response of the diode is represented by a stochastic point process (occurrence of latency peak), and the response of the diode array is given as successive realisations of a binary random field defined on a finite set. The Gibbs measure associated with this field is then estimated through the interaction potentials of the field’s configurations, which provide a quantitative evaluation of the interaction and the synchronisation between the neural sites. The analysis was performed on the latency of the peak of disynaptic activity, which was determined from signals from 60 different acquisitions realised with the same stimulus parameters. From these 60 files of latency values, we estimated the Gibbs interaction potential of singletons and pairs. The former gave an image of the spatiotemporal distribution of the disynaptic activity, which appears to propagate from the anterior to the posterior part of the area recorded. The estimation of the interaction potential of pairs allows us to characterise the degree of synchronisation between two neighbouring recording sites. It appeared that, in the anterior half of the area recorded, the disynaptic activity was statistically desynchronised whereas, in the posterior part the disynaptic activity appeared strongly synchronised. The functional implications of such a spatiotemporal distribution of the activity are discussed. Received : 10 January 1996 / Accepted in revised form: 25 October 1996     

Visual cortex contribution to the organization of eye movements produced by local electrical stimulation of the cat lateral geniculate body

Eye movements evoked by local electrical stimulation of the dorsal nucleus of the lateral geniculate body were analyzed after removal of the visual cortex and in intact animals during trials on awake cats. No significant difference was observed between the eye movement patterns of the two animal groups evoked by electrical stimulation. These movements could be classed into three main groups: those unassociated with the starting position of the eyes in orbit (or unidirectional movements), goal-directed, and centered movements, with direction depending on the initial position of the eyes in their orbits. Our findings indicate that the cortical visual areas are neither the principal nor an indispensable link in the chain for transmitting signals evoked by (electrically) stimulating the geniculate body from the cortical structures of the direct visual pathway towards the operative links of the oculomotor system. Potential pathways for conducting information from the dorsal nucleus of the lateral geniculate body to oculomotor system structures are discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 19, No. 2, pp. 164–170, March–April, 1987.