Neuronal organization of the periamygdaloid cortex in the cat brain

Neuronal organization of the fields Pmm, Pml2, Pe and epm of the periamygdaloid cortex of the cat brain has been studied by means of Golgi and Nissl methods. The field Pmm essentially differs from other fields of this cortex by primitiveness of its cytoarchitectonic an neuronal organization (two layers uniform by the composition of their neurons are distinguished, the structure of the latter is relatively primitive). In the medial part of this field long axonal rarely branching short dendritic, and in the lateral part--poorly differentiating pyramidal and spindle-like cells predominate. The field Pmm can be considered as a transitional formation between the subcortex (the medial nucleus of the amygdaloid body) and other fields of the periamygdaloid cortex. The fields Pml2, Pe and epm are built more complexly: the cells are organized in 4 layers, more complexly differentiated by their form and size than in the field Pmm and correspondingly more various (long axonal densely branching cells are observed: pyramidal and spindle-like--of the cortical type and bushy--of the subcortical type, as well as long axonal rarely branching reticular cells). The short axonal cells in the fields Pml2, Pe and epm are rather variable in their form, size and direction of axons; in the field Pmm they are less numerous. The field Pmm and the complex of the fields Pml2, Pe and epm are perhaps different in their function, this is evident from different projection of their neurons. Axons of the cells in the field Pmm get into less differentiated and the most ancient medial nucleus of the amygdaloid body and into the ancient system of connections of the latter--terminal strip, and neurons of the fields Pml2, Pe and epm are projected into the basolateral part of the amygdaloid body and into the external capsule--phylogenetically younger structures. Besides, poverty of the axonal collateralies in the long axonal neurons and a small amount and uniformity of the forms of the short axonal cells in the field Pmm and contrary, rich collateralies and variety of short axonal cells in the composition of other fields demonstrate more complex internal integrative function, performing in that composition.     

Neuronal ensembles in the cat motor cortex

Vertically oriented bundles of apical dendrites in the cat motor cortex were studied by methods of light and electron microscopy. The presence of desmosome-like and dendro-dendritic contacts in the bundles is regarded as the structural basis for electrotonic interaction between neurons in the same column. Axo-spinous "en passant" contacts between the descending axon of the pyramids of layer III and the apical dendrite of pyramids in layer V, possibly serving to regulate the activity of the principal cortical output elements, are described.A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 8, No. 5, pp. 455–458, September–October, 1976.     

Synaptic organization of the individual layers of field 4 of the cat cerebral cortex]

By means of electron microscopic method, synaptic organization of some layers in the field 4 of the cat brain cortex has been studied. It has been demonstrated that: a) synaptic organization of the cortex becoms more complex from superficual layers towards deeper ones; b) axospinous and axosomatic synapses have identical structure in all the cortical layers, while the structure of axodendritic synapses depends on their localization. A possible physiological estimation of the morphological data obtained has been carried out.     

Neuronal correlates of the motor function of the cerebral motor cortex

Modern ideas about the motor cortex neuronal mechanisms ensuring the initiation and correction of the instrumental manipulational movements in mammals have been analysed. A close correlation has been established to exist between the neuronal activity and various characteristics of movement including those that are not induced by muscle force. The role of somatic afferentation in the formation and realization of the movement programme is analysed as well as in motor output modulation by means of fast feedback.     

The temporal organization of the functional connection of the motor cortex neurons in the cat]

Conditioned food-procuring response to time (2 minutes interval) was elaborated in cats, multiunit activity of the motor cortex being recorded. On the basis of single spike trains discriminated from the multiunit activity the cross-correlation histograms were built and the spikes composing their peaks were analysed in real time. This secondary analysis of the histograms allowed to ascertain the dynamics of functional connections between the neurons during the phase of active waiting according to the distribution of coincident impulses. A concentration of coincident impulses of simultaneously recorded cells was observed in different moment of time. In some neuronal pairs the concentration of coincident impulses was revealed to the end of the conditioned interval. The data obtained are considered as a manifestation of the conditioned reaction at the level of neuronal interaction.     

Neuronal organization of the left celiac ganglion in the cat

Unit responses of the isolated left celiac ganglion to stimulation of various nerves of the solar plexus were studied by intracellular microelectrode recording in cats before and after degeneration of the preganglionic fibers. The resting potential of the ganglionic neurons was ?62.2±2.9 mV and the amplitude of the spike potential 72.4±3.2 mV. The spike was followed by after-hyperpolarization with a mean amplitude of 24% of the spike amplitude and a duration of between 25 and 180 msec. A characteristic feature of the ganglion was the presence of orthodromic unit responses to stimulation of peripheral nerve fibers of the solar plexus. The higher threshold of activation of the neurons by peripheral fibers than by preganglionic fibers and the preservation of orthodromic unit responses to stimulation of peripheral nerves after degeneration of the preganglionic fibers are evidence that the peripheral reflex arc is closed in this ganglion. Neurons of the left celiac ganglion are divided into three groups. Only preganglionic fibers of the splanchnic nerve with different properties converge on the neurons of the first group (the most numerous); only afferent fibers of peripheral nerves converge on the neurons of the third group (the least numerous); both types of fibers terminate on neurons of the second group. This convergence may lie at the basis of the mechanism of the centrifugal and peripheral reflex interaction in the ganglion for coordinated visceral activity.     

Neuronal correlates of motor performance and motor learning in the primary motor cortex of monkeys adapting to an external force field

The primary motor cortex (M1) is known to control motor performance. Recent findings have also implicated M1 in motor learning, as neurons in this area show learning-related plasticity. In the present study, we analyzed the neuronal activity recorded in M1 in a force field adaptation task. Our goal was to investigate the neuronal reorganization across behavioral epochs (before, during, and after adaptation). Here we report two main findings. First, memory cells were present in two classes. With respect to the changes of preferred direction (Pd), these two classes complemented each other after readaptation. Second, for the entire neuronal population, the shift of Pd matched the shift observed for muscles. These results provide a framework whereby the activity of distinct neuronal subpopulations combines to subserve both functions of motor performance and motor learning.     

Neuronal porosome in the rat and cat brain

It is well established that during cell secretion, membrane-bound secretory vesicles dock and fuse at the base of supramolecular cup-shaped structures at the cell plasma membrane called "porosomes", to expel intra-vesicular contents to the outside. In neurons, it has been demonstrated that 12-17 nm cup-shaped lipoprotein structure possessing a central plug are present at the presynaptic membrane, where 50 nm in diameter synaptic vesicles transiently dock and fuse to release neurotransmitter. In the past decade, the neuronal porosome has been isolated and its major chemical composition determined. Additionally, the porosome has been both structurally and functionally reconstituted into artificial lipid membrane, establishing its role as the secretory portal in neurons. Studies utilizing atomic force and electron microscopy, combined with electron density and 3D contour mapping, provide at the nanoscale, the structure and assembly of proteins within the neuronal porosome. In the current study, ultrahigh resolution imaging of the presynaptic membrane of isolated brains from both rats and cats, demonstrate for the first time, the presence of neuronal porosomes in cat brain, and further confirms the presence of porosomes at the presynaptic membrane in rat brain synaptosomes. Results from the present study further confirm the cup-shaped morphology of porosomes in the rat brain, and demonstrates their similar shape and size in the cat nerve terminal. The study also demonstrates for the first time, the universal presence of similar porosomes in different species of mammals.     

Neuronal porosome in the rat and cat brain

It is well established that during cell secretion, membrane-bound secretory vesicles dock and fuse at the base of supramolecular cup-shaped structures at the cell plasma membrane called “porosomes”, to expel intra-vesicular contents to the outside. In neurons, it has been demonstrated that 12–17 nm cupshaped lipoprotein structure possessing a central plug are present at the presynaptic membrane, where 50 nm in diameter synaptic vesicles transiently dock and fuse to release neurotransmitters. In the past decade, the neuronal porosome has been isolated and its major chemical composition determined. Additionally, the porosome has been both structurally and functionally reconstituted into artificial lipid membrane, establishing its role as the secretory portal in neurons. Studies utilizing atomic force and electron microscopy, combined with electron density and 3D contour mapping, provide at the nanoscale, the structure and assembly of proteins within the neuronal porosome. In the current study, ultrahigh resolution imaging of the presynaptic membrane of isolated brains from both rats and cats, demonstrate for the first time, the presence of neuronal porosomes in cat brain, and further confirms the presence of porosomes at the presynaptic membrane in rat brain synaptosomes. Results from the present study further confirm the cup-shaped morphology of porosomes in the rat brain, and demonstrates their similar shape and size in the cat nerve terminal. The study also demonstrates for the first time, the universal presence of similar porosomes in different species of mammals.     

Neuronal organization of the periaqueductal gray matter in the cat midbrain

It is shown by the use of Golgi's method in Antonova's modification that the neuronal structure of the periaqueductal gray matter (PGM) in the frontal plane is characterized by the presence of small and medium-sized cells of "reticular type," which can be subdivided into three types: fusiform, triangular, and multipolar. On the basis of the visual distribution of these types of neurons and also of statistical analysis of 800 identified neurons, two regions can be distinguished: medial, directly surrounding the aqueduct of Sylvius, containing small neurons, among which the fusiform kind predominate significantly (P<0.001), and a lateral region with larger neurons, with significantly (P<0.001) more triangular cells. Neurons in the medial region show a characteristic and strong (P<0.001) tendency for their dendrites to be oriented toward the lumen of the aqueduct, and through them the physiologically active substances of the CSF may influence the functional activity of neurons of PGM.Central Research Institute of Reflex Therapy, Moscow City Council Main Health Board, Moscow. Translated from Neirofiziologiya, Vol. 16, No. 6, pp. 773–777, November–December, 1984.     

Neuronal organization of the lateral basilar region of the cat spinal cord

The neuronal organization of the lateral basilar region (LBR) of gray matter in the cervical portion of the cat spinal cord was studied by light and electron microscopy. It was found that LBR neurons form a homogeneous group with regard to the size of their soma. The ordinary pale ultrastructure of the cytoplasm is found in 96.8% of neurons examined. The ultrastructure of the cytoplasm of the small cells (3.2%) is dark and their matrix has high electron density. Most endings on LBR neurons have spherical vesicles (of the S-type). Endings with flattened vesicles (F-type) are next in order of numerical frequency. In some endings, besides the ordinary synaptic vesicles, there are other vesicles with an osmiophilic center, and endings with a dense matrix and numerous spherical vesicles. Endings of the F-type are relatively more numerous on dendrites of LBR neurons than on their soma. Axodendritic synapses form 87.8% of the synaptic connections of the LBR, and axo-somatic synapses 9.2%. The few axo-axonal synapses are formed by small endings with small synaptic vesicles and large plaques with spherical vesicles. The latter frequently make contact with several dendrites simultaneously. The functional role of the various neuronal structures of LBR in the transmission of descending and afferent influences is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. A. N. Severtsov Institute of Evolutionary Morphology and Ecology of Animals, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 4, No. 3, pp. 296–302, May–June, 1972.     

Electrical characteristics of neurons in the cat motor cortex

Electrical characteristics of motor cortical neurons were studied in acute experiments on immobilized cats. Values of the input resistances varied from units to tens of megohms (mean 11.11±3.93 MΩ). The threshold current is a hyperbolic function of input resistance of the corresponding neurons and negative correlation was found between the axonal conduction velocity and input resistance. The time constant (τ₀) of the membrane was 7.1±3.46 msec. A time constant τ₁, of 1.65±0.36 msec, could also be distinguished in some neurons. Electrotonic lengths of dendrites of the cortical neurons were calculated by the use of Rall's model: mean 3.66±0.94 (in units of length constant).     

Spatio-temporal organization of receptive fields of the cat striate cortex

The responses of cortical cells to gratings and bars were compared. The excitatory and inhibitory on-and off-zones of a simple cell are composed of on- and off-subfields of CGL. Any zone is formed by an opponent pair of subfields one of which gives an excitatory effect, the other — inhibitory. Such organization assumes the linear properties of a simple field. The deviations from linearity are due to spatial dis-placements of the subfields, heterogeneity of subfields, or the absence of one subfield in the opponent pair. Subfields may be both phasic and tonic, even in the same RF. Analysis of the most common type of a complex cell with modulated responses against unmodulated background shows that a mask eliminating stimulation of any half of the RF causes (according to the theory of filtres) increasing the bandwidth due to the increase or the appearance of responses to side low and high frequencies. The modulated components of the responses from both halves of the RF are out of phase. Analysis of this fact and the responses to thin bars suggests that a complex field is formed by linear and nonlinear subsystems converging onto output neuron. Other types of complex fields are organized by different combinations of subsystems. Limited in area by masking the RF responds to much higher spatial frequencies than the whole RF. The optimal frequency in two-dimensional spatial frequency characteristics of the RF does not change with orientation. Simple RFs and a part of complex RF calculate the amplitude and the phase of the stimulus, the other part of complex RFs (with unmodulated response) calculate only amplitude. Given all this, the RFs are grating filters of spatial frequency.