Interhemispheric connections of the parietal area of the cat cerebral cortex

The interhemispheric connections of the temporal cortical area in the cat cerebrum have been investigated after electrolytic coagulation of separate fields with subsequent study of the degenerated fibers course after Nauta--Gygax method. The fields 5 and 7 give origin mainly to homotopic fibers, terminating in symmetrical fields of the contralateral hemisphere. These fields also give origin to a small number of heterotopic commissural fibers, that provide bilateral connection of the fields 5 and 7 and do not get beyond the limits of the temporal cortex. The commissural fibers of the temporal cortex get into the contralateral hemisphere through the corpus callosum. In the latter, the commissural fibers of the field 5 are situated more rostral of the fibers running from the field. 7. This corresponds to topographic arrangement of the fields on the cortical surface.     

Cochleotopic organization of the second auditory cortical area in the cat

The cochleotopic organization of the second auditory cortical area was investigated in cats anesthetized with pentobarbital by the evoked potentials method. Two independent representations of the cochlea were shown to exist in area AII: One in the dorsocaudal portion, the other in its ventrorostral portion. These projections of the cochlea differ in size and in the order of representation of its different parts. The dorsocaudal part of the auditory projection area of the cochlea, which extends over a distance of 2.6–2.8 mm from the center of the basal to the center of the apical focus, is arc-shaped. The order of arrangement of projections of different parts of the cochlea in this region of the auditory cortex coincides with that in the first auditory area, whereas the projection of the cochlea in the ventrorostral part of area AII, the length of which is 1.4–1.6 mm, has the opposite order of representation. The localization of projections of the cochlea in different cats shows considerable variability not only as regards anatomical topography of the auditory cortex, but also from one animal to another. The basal region of the cochlea was shown to project to a larger area of the cortex than the middle and apical portions taken together. It is suggested that the basal turn of the cochlea is functionally the most important for perception and primary analysis of auditory information.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 1, pp. 18–27, January–February, 1980.     

Receptive fields of neurons in the lateral suprasylvian area of the cat

The structure of receptive fields of single neurons in the lateral suprasylvian area of the cat's cortex was studied. Receptive fields of neurons in this area are larger (up to 2000 deg² or more) than those of the visual projection cortex. A difference was found in the sizes of these fields of the same neuron when measured by presentation of a black object and spot of light. Experimental results showed that most neurons of the area (104 of 148) that are sensitive to visual stimulation respond clearly to flashes of a stationary spot of light. Because of this feature the structure of the receptive fields of the neurons were studied by point by point testing of their whole surface. Intensities of on- and off-components of on-off neurons were found to differ. Only 16% of receptive fields had equal numbers of discharges in on- and off-components of the on-off response. Dominance of one component was observed in 84% of on-off neurons. Receptive fields with several discharge centers are a characteristic feature of neurons in this area. A concentric organization of the receptive fields was found in 11% of neurons.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan, Translated from Neirofiziologiya, Vol. 14, No. 3, pp. 278–283, May–June, 1982.     

Afferent connections of the dorsal magnocellularis area of the cat red nucleus

Location within the brain of retrogradely labeled neurons putting out projections from the dorsal magnocellularis area of the red nucleus was investigated by means of microiontophoretic injection of horseradish peroxidase into the dorsal magnocellularis area of the cat red nucleus. Projections were found from a number of hypothalamic nuclei, the centrum medianum, parafascicular and subthalamic nuclei, zone incerta, Forel's field, nucleus medialis habenulae, pontine and bulbar reticular formation, and the following midbrain structures: the central gray matter, superior colliculus, Cajal's interstitial nucleus, reticular formation, and the contralateral red nucleus. Projections were also identified proceeding from more caudally located structures: the cerebellar fastigial nucleus, facial nucleus, medial vestibular and dorsal lateral vestibular nuclei, and ventral horns of the spinal cord cervical segments. Connections between the substantia nigra and the red nucleus were clarified. Projections to the red nucleus from the cerebral cortex, interstitial and dentate (lateral) cerebellar nuclei, the nucleus gracilis and cuneate nucleus were found, confirming data presented in the literature. Bilateral trajectories of retrogradely labeled fiber systems are described.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 19, No. 6, pp. 810–816, November–December, 1987.     

Cholecystokinin-octapeptide like immunoreactivity in the area postrema of the rat and cat

The distribution of cholecystokinin-8 (CCK-8)-like immunoreactivity in the area postrema of the rat and cat was visualized using the peroxidase, antiperoxidase technique. In the rat the greatest amount of immunostaining occurred in peripheral regions of the area postrema at intermediate and rostral levels. Caudally, scattered immunoreactivity predominated. After colchicine treatment, numerous immunoreactive somata were observed throughout the area postrema. The cat area postrema had a different and more complex pattern of immunostaining than the rat. Moderate to dense accumulations of immunostaining occurred in the ventromedial region of the area postrema bordering the solitary tract and dorsal vagal nuclei. The central region of the area postrema possessed scattered amounts of immunoreactivity at rostral levels. Following colchicine treatment, no visible CCK-8-like immunoreactive cell bodies were observed in the cat area postrema. Results of the present investigation provide morphological evidence for the role of CCK-8 in cardiovascular regulation and satiety. The difference in the distribution of CCK-8 in the rat and cat suggest a possible role in the emetic reflex.     

The convergent properties of the neocortical vestibular area in the cat]

In acute experiments on cats under nembutal-chloralose anaesthesia the evoked potentials and cellular reactions were studied of suprasylvian vestibular and auditory projection zones to stimulation of vestibular, acoustic and visual nerves and frontal paw. It has been shown that the suprasylvian vestibular zone represents the region of convergence of vestibular, auditory, somatic and visual afferentation. Properties of summary and cellular reactions of the vestibular zone and also the character of interaction of the evoked potentials of homo- and heteromodal origin testify to the absence of significant dominance of vestibular input to this area of the cerebral cortex in cats. Limitation of spreading of labyrinth activity in the cerebral cortex and the absence of dominance of homomodal input in the projection zone should, probably, be considered as typical property of the vestibular system presentation in the cortex, determining the disability of monomodal specific reaction in the sensory-perceptive sphere.     

Tonotopic organization of the dorsocaudal zone of cortical area aii in the cat

The tonotopic organization of the dorsocaudal (DC) auditory cortex area AII was investigated during acute experiments on cats anesthetized with Nembutal. A capacity for selective response to presentation of auditory stimuli at a certain frequency was found in 93% of the neurons investigated. It was further observed that 75% of these cells were characterized by their fine tuning to one characteristic frequency (CF), the remaining 26% had several CF, and 7% reacted with a spike response to acoustic stimulation at all test frequencies and had no clearcut CF. A relationship was found between the location of a unit within the DC zone and its CF level. Neurons with the lowest CF were located in the upper position of the sylvian gyrus near the posterior ectosylvian sulcus. The CF of neurons rose progressively in step with increasing distance between the site of microelectrode recording and the low frequency focus of the DC zone travelling along the sylvian gyrus in a ventrorostral direction. Distance between low and high frequency foci of the DC zone measured 2.5–3.5 mm. Location of this zone in relation to the auditory cortex sulci varied considerably from one animal to another. Neurons with similar CF levels and arranged on this basis in vertical cortical columns could vary substantially in the dimensions of their receptive fields, sharpness of tunining to their own CF, and firing response pattern.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 20, No. 2, pp. 220–227, March–April, 1988.     

Cholinergic structures in the cat auditory cortex (area AI)

Plexuses of cholinergic varicose fibers, differing in density in different layers of the neuropil, were found in area AI of the cat's auditory cortex by the histochemical reaction for acetylcholinesterase: Their density was maximal or average in layer I or deeper layers and minimal in layers II and III. Among cells in area AI those which are cholinergic are a few stellate neurons located in layers II–VI. Axons of some neurons terminate on neighboring cells, those of others (some neurons in layer VI) run into the subcortical layer of arcuate association fibers. Cholinergic terminals are located on the bodies and proximal areas of dendrites of neurons most of which do not contain acetylcholinesterase. Choliniceptive neurons of different sizes and shapes are found in all layers of this region of the auditory cortex.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. I. I. Mechnikov Odessa State University. Translated from Neirofiziologiya, Vol. 16, No. 1, pp. 75–81, January–February, 1984.     

Neuronal responses in area 7 of the cat cortex during defensive conditioning

Responses of neurons in area 7 of the parietal association cortex during and after formation of a defensive conditioned reflex to sound were recorded in waking cats. Changes in spike responses of the neurons as a result of the onset of conditioned reflex limb movements were observed in 68% of neurons. Spike responses of neurons formed as a result of learning appeared only if conditioned-reflex limb movements appeared, and they were not observed if, for some reason or other, movements were absent after presentation of the positive conditioned stimulus or on extinction of the reflex. Responses of 46% neurons to conditioned stimulation preceded the conditioned-reflex motor responses by 50–450 msec. The remaining responding neurons were recruited into the response after the beginning of movement. Characteristic spike responses of neurons to the conditioned stimulus appeared 500–900 msec before the beginning of movement and, in the case of appearance of special, "prolonged" motor responses of limb withdrawal, evoked by subsequent reinforcing stimulation.     

A new visual area on the inferior wall of the cat cruciate sulcus

Properties of 187 neurons in the inferior wall of the cruciate sulcus, in an area where electrical stimulation evoked unidirectional saccadic eye movements, were investigated in waking cats. Of the total number 172 responded to visual stimulation. Neurons in the surface layers of the cortex responded to simple visual stimuli: light or dark spots or bars, both stationary and moving at speeds of around 30 deg/sec. These neurons showed no selectivity as regards stimulus orientation but sometimes behaved selectively toward the direction of their movements. In the intermediate layers the maximal neuronal response was obtained to a model of a bird flaping its wings. Neuronal responses in the depth of the cortex were characterized by selectivity to movement of stimuli toward or away from the animal in a certain part of the visual field, irrespective of whether a light stimulus was presented against a dark background or a dark stimulus against the light background. Responses to visual stimulation were exhibited only if the animal was in a state of activation, when the EEG showed desynchronization, and they were absent in a state of quite wakefulness. No responses were obtained to auditory or somatic stimulation. Responses to visual stimulation were not found in neurons of the medial wall of the brain beneath the cruciate sulcus, but responses were recorded to eye movements of definite size or orientation. It is postulated that at least two contiguous retinotopically organized zones exist in this part of the brain. Activity of one of them is connected with visual function, that of the other with eye movements.Institute for Problems in Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 16, No. 6, pp. 766–773, November–December, 1984.     

The area of the optically activated zones of cat area 17 under stimulation with grids of different orientation

In acute experiments with 9 anesthetized and immobilized cats, the relative tangential square of the activated cortical columns in area 17 was mapped by the intrinsic optical signal under stimulation with grids of different orientation. We examined the "oblique effect", i.e. the greater representation of neurons tuned to the vertical and horizontal orientations vs. oblique orientations in the primary visual cortex. The square of the activated parts of the cortex was estimated under different threshold criteria (80, 60 and 40% of the maximum). The "oblique effect" was not observed in our study: the areas of activation of the cortical columns did not differ statistically for two basic vs. oblique orientations. Reasons for the difference between the results of electrophysiological and optical mapping are suggested and possible contributions of the experimental protocol (anesthesia) and individual visual experience in different animals' samples to the origin of these differences are discussed.     

Autonomy of spontaneous rhythmogenesis of perivesicular area of cat ureter

The work presents data indicating no dependence of the pacemaker activity located in the zone of junction of cat ureter with urinary bladder on genesis of the main perirenal pacemaker. Data are presented on effect of clamping the renal artery supplying with blood flow the renal area on rhythmogenesis of the ureter perivesicular area. An inhibition of the pacemaker activity of the pyeloureteral anastomosis is observed. At the same time, no marked effect on automatism of the low organ area is revealed. Data of morphological studies of the vascular bed providing blood supply of various ureter areas are presented.