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Transposition errors during the reproduction of a hand movement sequence make it possible to receive important information on the internal representation of this sequence in the motor working memory. Analysis of such errors showed that learning to reproduce sequences of the left-hand movements improves the system of positional coding (coding ofpositions), while learning of the right-hand movements improves the system of vector coding (coding of movements). Learning of the right-hand movements after the left-hand performance involved the system of positional coding "imposed" by the left hand. Learning of the left-hand movements after the right-hand performance activated the system of vector coding. Transposition errors during learning to reproduce movement sequences can be explained by neural network using either vector coding or both vector and positional coding.

A review. Works related to research into the neuroanatomical basis of associative learning in the honeybee (proboscis extension reflex) are summarized. Data on the brain organization of the honeybee are presented. The parallel neural pathways of conditioned and unconditioned stimuli are shown. Contribution of different brain structures and identified neurons (VUMmx1, PE1) in the formation of the proboscis extension reflex are discussed.

A review. Possible mechanisms for generation of neural representations of object-place associations (NROPA) are analyzed in different parts of a neural network which include the hippocampus and parahippocampal complex. Streams of spatial and non-spatial information arrive to the hippocampus from the parahippocampal complex consisting of perirhinal, postrhinal and entorhinal cortical areas. We assume that, due to the absence of connections between lateral and medial areas of the entorhinal cortex, object-place associations are mostly formed in the hippocampus, but can also be generated in the perirhinal cortex due to existence of input from the postrhinal cortex. As both information streams converge on neurons of the dentate fascia and field CA3, a trisynaptic pathway through the hippocampus can play the basic role in the NROPA generation. Since the spatial information arrives in the neocortex and, therefore, reaches the parahippocampal complex and hippocampus approximately by 20 ms earlier than the "non-spatial" stream, only spatial information is processed firstly in the dentate fascia and field CA3. Generation of NROPA in the dentate fascia starts later, due to returning excitation from field CA3c. In the dentate fascia, signals from the NROPA are transferred into field CA3, where the activated neuronal pattern is superimposed by information arriving from the entorhinal cortex. As a result, more complex NROPA are formed in field CA3 and send signals to field CA1. In the dorsal (ventral) part of the field CA1, the activated neuronal pattern is superimposed by non-spatial (spatial) information arriving from the lateral (medial) part of the entorhinal cortex. As a result, a higher-order NROPA are generated. In the parahippocampal cortex, the generation ofNROPA can be a consequence of the activity transferred from the dorsal part of the hippocampal CA1 field.

In order to reveal characteristics of functioning of amygdalar neuronal network during unconditioned fear, firing patterns of basal and central nuclear neurons and their interaction were studied during freezing (fear), active unconditioned motor reactions (in the absence of fear) to emotionally significant stimuli, and during quiet wakefulness. As compared to other states, specific changes in interaction of adjacent amygdalar neurons took place during freezing. Such changes were not revealed in firing of single neurons. During freezing, the number of short-latency (to 100 ms) excitatory connections increased and the number of long-latency (250-450 ms) inhibitory connections decreased. In freezing, more frequently than in other states, delta-2 range frequencies (from 2 to 4 Hz) were observed in the interneuronal interaction. During active locomotor reactions to stimuli, the number of interacting neurons decreased, the number of long-latency (200-250 ms) excitatory and short-latency (50-200 ms) inhibitory connections decreased, and theta 1-range frequencies were frequently observed in the interaction. It was concluded that, for the development of fear, the balance between excitatory and inhibitory links of amygdalar neuronal network is essential.

The authors suggest to distinguish the mesoaccumbocingulate dopaminergic system within the mesocorticolimbic dopaminergic system. It defines the formation of dependence on the influence of psychoactive drugs. The cortical center of the mesoaccumbocingulate dopaminergic system--anterior cingulate fields in rats (Cg1 and Cg3)--simultaneously represents the affective and motivation-mnestic center. The affective function of the rat anterior cingulate fields after the administration of psychoactive drugs, as well as the formation of dependence on them, is associated with the distribution of the dopaminergic endings of midbrain neurons in the nucleus accumbens and at the anterior cingulate fields, in particular, in the pregenual part.

Dopamine(DA), the most widely distributed in the nervous system and functionally important chemical signal, is synthesized in DA-ergic neurons from L-tyrosine by means of two enzymes, tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AADC). Apart from the enzymes, specific DA transporter is an attribute of DA-ergic neurons. In the mid eighties of the last century, in addition to DA-ergic neurons, those expressing only one enzyme, TH or AADC, have been discovered. These "monoenzymatic" neurons occurred to be more numerous and more widely distributed in the brain compared to DA-ergic neurons that manifests their wide involvement to the brain functioning. It has been demonstrated that the monoenzymatic neurons expressing complementary enzymes of DA synthesis produce this neurotransmitter in cooperation. In this case, L-tyrosine is transformed to L-DOPA in TH containing neurons that is followed by L-DOPA release and uptake from the intercellular space to AADC containing neurons for DA synthesis. Moreover, the L-DOPA uptake to DA-ergic or serotoninergic neurons results either in the increase or the onset of DA synthesis in addition to serotonin, respectively. The expression of the enzymes of DA synthesis in non-dopaminergic neurons is one of the adaptive reactions serving to compensate the functional insufficiency of DA-ergic neurons. For instance, hyperprolactinemia and the deficiency of DA, prolactin-inhibiting hormone, which is developed under degeneration of DA-ergic neurons of the arcuate nucleus, are compensated with time due to the increase of the number of monoenzymatic neurons and cooperative synthesis of DA in the nucleus. It is supposed that the same compensatory cooperative synthesis of DA is turned on under the degeneration of DA-ergic neurons of the nigrostriatal system that is manifested by the appearance of non-dopaminergic neurons expressing enzymes of DA synthesis in the deafferentated striatum. The expression of the enzymes of DA synthesis in non-dopaminergic neurons is under the control by intercellular signals, catecholamines, neurotrophic (growth) factors and, perhaps, hormones. Thus, non-dopaminergic monoenzymatic neurons expressing enzymes of DA synthesis produce this neurotransmitter in cooperation that is a compensatory reaction under functional insufficiency of DA-ergic neurons, in neurodegenerative diseases, hyperprolactinemia and Parkinson's disease, in particular.

In reply to the article of an opponent, the author presents new personally obtained data on the similarity of some brain neurons possessing asynaptic dendrites and innervating the perivascular space, pia mater (from inside), or having the direct contact with the ventricular cerebrospinal fluid, to the local autonomic Dogiel's II type neurons of the viscera. Author also demonstrates personal electron micrographs showing the terminals of asynaptic dendrites of brain neurons which are not different in any aspect of their ultrastructure from the terminals of visceral receptors. The facts are presented, that, in author's opinion, refute the opponent's conceptions on the impossibility of the various receptor functions of the cilia in general, and in ciliated neurons, in particular, on the development of sensory neurons from the neural crest only, and on the impossibility of the sensory innervation of the brain tissues, in principle.

We investigated distribution of retrograde-labelled cells in cortical areas 17, 18, and the transition zone 17/18 of both hemispheres in cats after microiontophoretic horseradish peroxidase (HRP) injections into the single cortical columns of area 17, 18, 19 or 21a. On the base of clustered pattern of intrinsic labelling, asymmetric location of labelled callosal cells that was associated with the appropriate pattern of labelling in layers A and A1 of lateral geniculate nucleus, we suggest that cortical neuronal connections are eye-specific and may provide for each eye a separate binding of visual hemifields. After HRP injections into columns of area 19 or 21a, the disparate inputs from areas 17, 18 and transition zone 17/18 were revealed. Such connections may provide a local depth information and the selection of stereoscopic surfaces in central sectors of visual space.

A modulating character of the amygdala basolateral nuclei effect upon the vestibular sensory system was determined in rabbits [correction of rats]. A mechanism of the descending effect of the amygdaloid complex on the activity of the Deiters nucleus neurons, is discussed.

Synaptic junctions in the rabbit amygdala were studied by electron microscopy. A definite distribution of morphologically different synapses on the neuronal surface was noticed. This distribution changed 3 days after ipsilateral lobectomy. A suggestion is made on transformation of a certain morphological form of synaptic contact into another one during the changed function.

Neuronal responses in the first and second somatosensory cortex (SI and SII) to stimulation of the ventroposterior nucleus of the thalamus (VP) were studied in experiments on cats immobilized with d-tubocurarine. 12.0% responding neurons in SI and 9.5% in SII were activated antidromically by VP stimulation. In the majority of antidromic responses the latencies did not exceed 1.0 ms. The minimal latency of orthodromic spikes was 1.5 ms in SI and 1.7 ms in SII. In SI the number of neurons whose orthodromic spike latencies did not exceed 3.0 ms was larger than neurons activated with latencies of 3.1-4.5 ms. In SII an inverse quantitative relationship between those two neuronal groups was observed. In SII a significantly larger number of neurons was excited with latencies of EPSPs ranged between 1.1-9.0 ms in SI and between 1.4-6.6 ms in SII and the latencies of IPSPs between 1.5-6.8 ms in SI and 2.2-9.4 ms in SII. The importance of different pathways for excitatory and inhibitory VP influences to neurons of SI and SII is discussed.

Extra- and intracellular responses of pars principalis neurons in the medial geniculate body to stimulation of the first (AI), second (AII) and third (AIII) auditory cortex were studied in experiments on cats immobilized with d-tubocurarine. In geniculate neurons both antidromic (45-50%) and orthodromic (50-55%) reactions occurred in response to the auditory cortex stimulation. The latencies for antidromic and orthodromic responses were 0.3-2.5 ms and 2.0-ms, respectively. Late responses appeared with a latency of 30-200 ms. 63% of neurons responded antidromically to both AII and AI stimulation, that confirms the suggestion on the projection of a considerable number of the geniculate neurons to both auditory zones. Orthodromic responses of geniculate neurons consisted either of 1-2 spikes or a burst of 8-12 spikes with a frequency of 300-600/sec. The bursts are supposed to be the responses of inhibitory geniculate neurons. Intracellular recording showed the following responses: antidromic spikes, EPSP, EPSP-spike, EPSP-spike-IPSP, EPSP-IPSP and initial IPSP. Above 50% of initial IPSPs had the latency of 2.0-4.0 ms. They are supposed to be produced with the participation of intermediate inhibitory neurons located in the medial geniculate body.

The activity of reticulo-spinal (RS) neurons was recorded in thalamic and decerebrate cats during actual and "fictition" scratching. Most RS neurons were silent during scratching, but some exhibitied a distinct modulation of their discharge related to the rhythmical activity of motoneurons. They were excited during the flexor phase and inhibited during the extensor phase of the cycle. The pattern of modulation was identical both in actual and in "fictitions" scratching.

The influence of stimulation of stria terminalis and midbrain central gray substance on the neuronal activity of the lateral hypothalamus was studied in acute experiments on curarized rats. Five types of neuronal responses were found: 1) phase activation; 2) phase inhibition;3) diffusive activation; 4) diffusive inhibition; 5) two-phase responses. Stimulation of stria terminalis produced inhibition in 62.7% of the lateral hypothalamus neurons. 87% of those neurons were activated after stimulation of the central gray substance. The convergence of impulses from the amygdaloid complex and midbrain central gray substance was observed in 14.4% of reactive neurons. 84.6% of cells showed antagonistic convergent effects.

Chang's experiments showing the rhythmic afterdischarge in slightly nembutalized cats which he considered as a manifestation of the activity of thalamocortical reverberating circuits, prompted us to study the origin of the afterdischarge in the auditory cortex arising in response to single sound clicks on unanesthetized immobilized and nembutalized cats. The rhythmic afterdischarge was found to be most pronounced at light anesthesia with a tendency of background activity to synchronization, which may be evidenced by rare bursts of spindles. During the prolonged spontaneous desynchronization as well as during stimulation of mesencephalic reticular formation no rhythmic afterdischarge and no spontaneous bursts of spindles arose. With a deepening of anesthesia slow afterdischarge undergoes precisely the same changes as spontaneous spindle bursts (the duration tends to increase for a while with a subsequent decrease, the frequency and then the amplitude of waves decrease and eventually they disappear altogether). These and other findings suggest that rhythmic afterdischarge of the auditory cortex arising to sound clicks seems to be similar to the evoked spindle in response to peripheral and central stimulations. It was reported in many previous and recent papers. The fact, that following the cooling or ablation of the auditory cortex the rhythmic afterdischarge to sound clicks as well as spontaneous spindle bursts keep arising in the medial geniculate body without changing their patterns, militates also against the possibility of thalamocortical reverberation.

Neuromorphological, neurophysiological and biomechanical studies in cats revealed cortical structural neuronal modules and functional units of different grades of complexity. Single systemic principle was determined for the sensorimotor cortex activity: structurally organized neuronal modules, having distributed outputs, can be involved in different functional units for purposeful movements. Specific lemniscal signals concerning the movements are the factor which filters inflow of teleceptive information to the neuronal modules and determines exact torographical relations of cortical motor outputs.

Evoked activity of single units in anterior and posterior hypothalamus to vagal, sciatic nerves, and photic stimulation was studied in anesthetized and immobilized cats. The responsiveness of neurons of the posterior hypothalamus was 66, 77 and 37% to vagal, sciatic nerves and photic stimulation, respectively, and of the anterior hypothalamus -- 47, 62 and 48%. Vagal stimulation was found to be the more effective for units of the posterior hypothalamus. Responses of units to a flash prevailed in the anterior hypothalamus. 78% of convergence of viscero-somatic afferentation on neurons of the posterior hypothalamus and 62% -- on anterior hypothalamic neurons, were revealed. The responses to all kinds of afferent stimuli were phasic and of excitatory character. Possible role and mechanisms of vagal interoceptive activation of hypothalamic units are discussed.

Distributional peculiarities of the associative and callosal connections of the visual area and parietal region in the cat cortex have been studied by Nauta-Guigax and Fink-Heimer's methods. Their horizontal and transversal distribution in the parietal and occipital areas are described. The afferents of the visual projection area are rare in both hemispheres, but spread in all visual areas and middle suprasilvian girus. The connections of the parietal associative area are expressed better and seen in all areas of parietal and occipital regions of the ipsilateral hemisphere, in the contralateral hemisphere, however, they are found in its homotopic area. Both afferent, independently of their origin are characterized by the identical distribution along the transverse of the different zones of the neocortex. For example, in field 17 the oblique and radially oriented degenerating fibres are represented equally and are limited by inner layers, as to the parietal associative region, predominatingly radial parallel fibres are seen along the whole cortex, they terminate mainly in the upper layers.

Bilateral electrolytic destruction of the paramedian midbrain caudal tegmentum caused the appearance in the internal part of the hypothalamic supraoptic nucleus of neurosecretory cells with low functional activity and degenerating forms (dark-stained and pycnomorphic cells); in the posterior hypophysis the destructed gigantic terminal varicosities (Herring bodies) were revealed; the posterior hypophysis contained a subnormal amount of neurosecret; the vasopressin-antidiuretic hormone level in blood plasma was reduced. Painful stimulation of animals with the destructed midbrain tegmentum revealed the functional insufficiency of the supraoptic hypophyseal neurosecretory system (SHNS). The results obtained permit considering that the paramedian midbrain tegmentum exerts a modulating influence upon the SHNS function during stress.

The changes in the receptive fields of neurons in the deep layers of the tectum opticum were studied as induced by labyrinthine and sound stimulation. Variations in the size of the receptive field, the particular direction of sensitive cells movement, duration of the reaction and amount of impulses in it were found. The results obtained and data from the literature allow one to suggest an active role of tectum opticum in the transformation of signals from the retina depending on the kind of information from other sensory systems.

It has been shown in experiments on alert rabbits that evoked potentials (EP) of the visual and motor cortex to a millisecond stimulation of the midbrain reticular formation (RF) have a greater similarity (due to increased amplitude and coherence of the theta-rhythmic components) as compared with preceding background activity and evoked potentials to a photic flash. The EPs of these neocortical areas to a photic flash had a more similar form after preliminary RF stimulation. The similarity of evoked responses to stimulation of RF increased after its repeated presentations. The summate poststimulus histogram in which the responses of individual units (24 neurones) of the visual cortex to a single RF stimulation were summed up, proved to be similar in form to EP recorded on the surface of the visual cortex after a similar RF stimulation.

Stimulation of the motor cortex evoked excitatory and inhibitory PSP in reticulospinal neurons of the cat gigantocellular nucleus. EPSP were recorded in 94.3% of the investigated neurons and IPSP in 5.7%. Analysis of the presynaptic pathways showed that 77.4% of EPSPs appeared through monosynaptic and 22.6% through polysynaptic corticoreticular connections. According to latency, duration and rise time all monosynaptic EPSP were divided into two groups (fast and slow). Obviously, fast EPSPs are generated by fast corticobulbar fibres and slow ones by slow fibres. IPSP were recorded in neurons which were also inhibited by stimulation of the ventral funiculi of the spinal cord. It is suggested that motor cortical signals can be transmitted to the spinal cord through both mono- and polysynaptic connections of the fast and slow pyramidal neurons with reticulospinal neurons.

Cortical respones to low-frequency (6 to 8 per sec) rhythmic stimulation of the Centrum medianum thalami have been studied in chronic experiments on cats. Three types of recruiting reactions have been readily obtained: 1) with periodic spindling of response amplitudes, the sustained oscillatory type; 2) with spindling only at the beginning of stimulation, the decaying oscillatory type, and 3) with equal amplitudes throughout the stimulation, the aperiodic type. Distinct changes in the type of reactions have been shown--from the aperiodic to the sustained oscillatory type during transition of active awake state to slow-wave sleep, and from the sustained oscillatory type to the aperiodic type during transition of slow-wave sleep to the paradoxical sleep, which is due to changes in the weights of feedbacks in the thalamo-cortical nonspecific system.

Responses of single hypothalamic neurons to splanchnic, sciatic nerves and photic stimulation were studied in anesthetized, curarized cats. It is found that units of the posterior and anterior hypothalamus are "convergence neurons" with multisensory inputs. Convergence of somatosensory and visceral (splanchnic) impulses to such neurons was complete. No neurons responding only to the splanchnic nerve stimulation were found. In the posterior hypothalamus some units responded only to stimulation of splanchnic and sciatic nerves and were unresponsive to a flash. On the contrary, in the anterior hypothalamus a part of units responded only to photic stimulation. The polysensory neurons of the posterior and anterior hypothalamus were of a nonspecific modality: they responded with a similar pattern of phasic or tonic discharge with a predominance of phasic responses. Units were more often excited than inhibited. A high responsibility (68%) of spontaneously active neurons to somato-visceral and photic stimulation was observed in the posterior, as well as in the anterior hypothalamus. The principles of functional organization of hypothalamic afferent system are discussed.

Definite ultrastructural features were found in the regions of the cat spinal grey matter connected with different descending pathways, especially in the structure of dendritic membranes and relative quantities of axon terminals. Two types of destructive changes in myelinated axons and axon terminals in these regions were observed during experimental degeneration of descending fibres. Axon terminals of small size and F-type vesicles were subjected to degeneration after pyramidal tract lesion, while large terminals of both S-type and F-type were affected after sectioning of extrapyramidal tracts.

The evoked potentials in the anterior suprasylvian and posterior sigmoid gyri to the bulbar vestibular nuclei stimulation were recorded in relaxed anesthetized cats. Neuronal discharges of 70 units in the forelimb cortical zone in the posterior sigmoid gyrus were also recorded. 26 neurons responded to the vestibular nuclei stimulation, 6 of them were identified as cortico-rubral neurons. All of them were activated by the radial-nerve muscle branch stimulation. There was no neurons characterized by the muscle-vestibular convergence from the pyramidal tract neurons. The muscle-vestibular afferent system projection to the cortico-rubral neurons is supposed to play a major role in the tonic muscle coordination of the forelimbs.

Responses of propriospinal interneurons localized in the ventromedial regions of the cat lumbar cord to the reticulospinal tract stimulation were studied. Monosynaptic excitatory action usually accompanied by di- and polysynaptic components was found in most units. Strong single stimuli were able to evoke discharges only in some cells, while temporal summation was necessary in many others. Excitation of neurons was followed by a short postactivation inhibition limiting the maximal discharge frequency.

Parallel intracellular recording from giant reticulospinal axons and target motoneurons of the lamprey (Lampetra fluviatilis) revealed unitary synaptic actions produced in the post-synaptic membrane by direct stimulation of individual presynaptic fibres. It is shown that monosynaptic reticulomotoneuronal EPSPs contain both electrical and chemical components which have different synaptic delay, time course, amplitude, sensitivity to Cadeficit and operating characterisitcs. A single motoneuron may receive direct electrotonic inputs from several giant axons. Individual giant axons may affect segmental motoneurons not only via monosynaptic connections but also via additional synaptic relays.

The development of the Luy's nucleus of the cat is not accomplished by birth-time. Complex relationships between nerve cell and capillaries continue to change during postnatal ontogenesis. The function of the Luy's nucleus becomes perfect by the third month. It should be noted that maturation of nerve cells and the vascular network goes not in parallel: the enlargement of the nerve cell occurs smoothly while the increase of the vascular-capillary network density is undulatory. There are three peaks in the development of vascular-capillary network: the 20th day, one month and a half, adult cat.

In experiments on alert rabbits high frequency stimulation of the CA1 field of the dorsal hippocampus reduced the peak latency of the main negative component of the evoked potential (EP) to a light flash in the sensorimotor and occipital tests areas of the cerebral cortex. A single stimulation of the same part of the hippocampus resulted in a gradually developing facilitation of secondary negativity of the EP 5th component, predominantly in the sensorimotor cortex. Investigation of neuronal responses in the same cortical areas to a stimulation of the CA1 field with different parameters has shown that the effects of EP modulation are due to dynamic reorganizations of cortical neuronal activity.

Time characteristics of the monosynaptic EPSP evoked by stimulation of the motor cortex in reticulospinal neurons were studied in detail. Negative correlation was revealed between latency duration of EPSP and conduction velocity of the corticobulbar fibres and positive correlation between such characteristics and conduction velocity of axons. Reticulospinal neurons with conduction velocity from 10.8 to 65.0 m/s were activated by fast and slow corticobulbar fibres, but neurons with conduction velocity from 65.0 to 155 m/s were activated only by slow ones. A functional role of different cortico-reticulo-spinal connections is discussed.

Microapplication of noradrenaline, isadrine, phentolamine, and propranole to neuroanal populations of the striatum in curarized unanesthetized rabbits revealed an inhibitory and stimulatory effects of noradrenaline and isadrine. A specific antagonism between alpha- and beta-adrenomimetics and respective alpha- and beta-adrenoblocking agents, was noted. Noradenaline seems to have a very important mediatory function in the adrenergic synapases of the striatum. Existence of alpha- and beta-adrenoreceptors with different functions in different brain areas, is suggested.

By means of cyclography method developed in detail by N.A. Bernstein for disclosing the changes in the physical parameters of jumps it was shown that as compared with intact animals, the speed of movements of the distal parts of the fore and hind limbs significantly decreases in animals with electro-coagulated medial lemnisci. The swing of flexion-extension in the ulnar and knee joints likewise diminishes, and the trajectory of the centre of gravity movement changes significantly. In the course of jumping from one platform to another the operated animal experiences difficulties in changing movement phases. It is suggested that the system of medial lemnisci exercises the function of internal somatic backward connection, which is necessary for the succession of micromovements within the general program of the motor act.

Electric stimulation of different hypothalamic nuclei was used during the effect of extracellular polarizing current on neurons of the rabbit optic cortex. It was found that stimulation of the hypothalamus caused a decrease in the medium rate of impulsation of a great number of studied optic cortex neurons under conditions of anodic polarization when the background level of activity was considerably enhanced. The same stimulation increased the activity under conditions of cathodic polarization when the initial level of the activity was considerably lowered. The same tendency to restore the initial (background) level of the neuronal activity after hypothalamic stimulation was observed under conditions when this level was shifted by application of rhythmic light. The greatest effect was observed during stimulation of the preoptic region. Stimulation of the posterior hypothalamic nucleus was less effective in this respect.

It has been found on alert non-immobilized rabbits that paired stimulations of the medical lemniscus, the midbrain reticular formation and the pyramidal tract in different succession cause in the sensorimotor cortex the formation of a temporary connection by the parameters of single unit activity and evoked potentials. The temporary connection is manifested in dynamics of evoked responses and in the change of electrical activity at the moment of usual presentation of the second stimulus, if it is omitted. The inflow of impulse activity by different paths adds some peculiarities to the organization of the temporary connection. The leading role in the given model situation may belong to the non-specific system.

A study has been made of the posttetanic potentiation of evoked potentials (PTP EP) in the sensorimotor cortex, appearing in response to VPL stimulation. A distinct PTP EP of the cortical surface has been found as well as considerable differences in its intensity recorded at different portions of deep cortical layers (700 to 1600 mu). Suggestions were made regarding the origin of the phenomena observed.