INFLUENCE OF DOMINANT MOTIVATION ON THE FUNCTIONAL ORGANIZATION OF AUDITORY INPUT TO THE SENSORIMOTOR CORTEX OF THE CAT BRAIN

Yu. V. Ivanova, L. A. Vasil'eva, and G. Ao Kulikov

UDC 612.822.3 + 615.85

The results of experiments reviewed in this article demonstrate the possibility of the transformation of the frequency tuning of the auditory input into the sensorimotor cortex (SMC) of the cat under the influence of a dominant motivation. Similar changes took place in the parietal cortex (PC), but they were significantly less in absolute magnitude. The identified transformation of the frequency tuning of the auditory input into the SMC and the PC is in agreement with a change in the biological significance of the auditory signals of kittens for females in the period of lactation, and corresponds for each cat to the spectral composition of the vocalizations of its own kittens~

The problem of the significance of various signals is resolved by the living organism on the basis of the dominant motivation [1, 2, 17]. Change in motivational state exerts an influence on the electrical activity of cortical structures, and first of all, on the frontal neocortex [17]. It is known that the formation of motivational states takes place with the direct participation of the limbic system, which has numerous connections with the frontal cortex [7, 8, 13, 16, 21, et al.], and that stimulation of the limbic structures exerts an influence on the electrical activity of frontal region of the cortex, including the sensorimotoro In addition, the selectivity of reactions relative to the spectral characteristics of sound signals takes place particularly in the sensorimotor cortex (SMC) of cats; the existence of this selectivity is associated with the reflection of the biological significance of the features of acoustic stimuli [4, 5, 10]. Taking the dependence of the significance of the acoustic stimuli on the dominant motivation into account, it seemed of significance to analyze the influence of this factor on the functioning of auditory input into the SMC. Maternal behavior in females in the early periods following the birth of kittens was selected as the experimental model of dominant motivation. The choice of this model was predetermined by the previously available observations on dominant maternal behavior following the birth of kittens, especially in the first month of their life. At the same time, the significant role of acoustic signals of kittens in the organization of maternal behavior was taken into account [18, 20]. In order to determine the role of dominant motivation in the organization of auditory input into the SMC in conditions of a chronic experiment in two females, the dependence of the amplitude of average evoked potentials (AEPs) of the sensorimotor and parietal regions of the cortex on the filling frequency of tone bursts in the norm, over the course of a two month period of pregnancy, and 2-4 week following the birth of kittens. Additionally the role of the acoustic signals of kittens of the same cats in the organization of maternal behavior was investigated. METHODS The experiments were carried out on awake cats (females) with chronically implanted electrodes. Animals without visible features of middle ear disease were selected for the study. The electrode implantation operation was performed under hexenal anesthesia (80 I.tg/kg) under sterile conditions. Silver electrodes were implanted epiduraUy into the SMC (the lateral portion of the pericruciate sulcus) and the PC (field 5).

A. A. Ukhtomskii Physiological Institute, Leningrad State University. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 39, No. 3, pp. 527-535, May-June, 1989. Original article submitted February 24, 1988; revision submitted August 19, 1988. 0097-0549/90/2003- 255 $12.50 9 1990 Plenum Publishing Corporation

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During the experiment the animal was kept in a screened chamber. The animal's movement was limited by placing it in a special hammock. Tonal bursts with a filling frequency of 0.5-6.3 kHz, duration 100 msec, rise and decay time 6 msec, at a constant level of sound pressure at the site of input into the external auditory canal, were used as the acoustic stimuli. The tone bursts, formed by means of an electronic switch which provides a null switch-on phase, were presented through an MD-64M electrodynamic sound source, which was located contralateral to the side of the recording of the AEPs at a distance of 10 cm from the input into the external auditory canal along its central axis. The frequency characteristics of the sound-emitting system were constantly monitored by a "Bruel and Kjaer" (Denmark) acoustic measuring complex (microphone type 4134). The recording of the evoked potentials was accomplished monopolarly by the conventional methods. The collection and averaging was carried out by means of an F-37 signal analyzer~ The analysis time was 250 msec; the sampling interval, 100 [zsec. The AEPs obtained from 20 realizations were outputted to a two-dimensional recorder. Tonal bursts were presented in each experiment with filling 'frequencies of 0.5; 0.63; 0.8; 1.0; 1.25; 1.4; 1.6; 1.8; 2.0; 2.5; 2.8; 3.15; 3.6; 4.0; 5.0; and 6.3 kHz. The animal was presented with 20 tone bursts with the same filling frequency not more often than once in 5-10 sec. Following the averaging of the evoked potentials, 20 tone bursts with a different filling frequency was presented, etc. The order of the presentation of the tone bursts with different filling frequencies was changed from experiment to experiment. The state of the animals was monitored during the experiment by ECG, and visually by means of a PTU-44 television unit. Seven females with chronically implanted electrodes were prepared for the experiments. However, it was only possible in two of these to record the AEPs in all three periods: in the norm, during pregnancy, and following the birth of kittens. The females were kept separate from the males during the recording of the reactions in the norm. After 10-12 experiments were carried out in an intact female, a male was introduced to her in a cage. In connection with the difficulty of determining the time of fertilization, 56-60 days (the duration of pregnancy in the ca0 were counted off from the time of the kittens' birth, and the AEPs recorded in that period were referred to the period of pregnancy. The experiments were performed following the birth of kittens, when the female herself abandoned the nest, in order not to induce a negative attitude toward the experiment in her. Therefore, the cat stayed in a sound-proofed chamber without manifesting signs of disturbance over the course of the experiment (45-50 min). The investigative period for one animal took more than half a year overall. Thirty experiments were run on one female, and fifty on the other. In analyzing the results obtained, the average amplitude and temporal parameters of the AEPs were calculated for each animal for all of the periods studied. The significance of the differences of the average values was established. The obtained results were statistically treated by means of one-way and two-way analysis of variance on an SM-3 computer. The computer programs for the treatment of the results were programmed by Senior Instructor T. I. Golikova of the Leningrad Institute of Control Methods and Technology, to whom we tender our thanks. Vocalization was recorded in three kittens of two of the animals studied. The recording was achieved by means of a MK16 condenser microphone on a ~Ritm-310 (KZMP-5)" magnetic recorder. The recorded signals were processed on a "Spektr" analyzer, which allowed us to obtain spectrograms of these vocalizations. In all 131 signals, recorded in kittens at the age of 2-9 days, were analyzed. The values of the formant frequencies, identified by the modulation of the intensity of the responses of the fdters in a stationary segment, and the range of frequencies in which changes in the spectral maxima with respect to time were observed, were determined for each vocalization. Histograms of the formant frequencies for the signals of the individual kittens and for the whole sample were conswacted on the basis of the results of the processing of these data. RESULTS AEPs, which corresponded in their amplitude and temporal characteristics to those previously described in [11], were recorded in response to tone bursts with different filling frequencies in the SMC and the PC. The curves, which were constructed for both females, of the dependence of the amplitude of individual phases of the AEPs in the SMC and PC on the filling frequency of the tone bursts had the typical form in the norm [5, 10], i.e., were characterized by the presence of reliable maxima in specific frequency ranges. A change in the value of the amplitude of the AEPs took place in the SMC during pregnancy and following the birth of the kittens. These changes were not identical when tone bursts with different filling frequencies were presented. The results of the investigations of one of the females are presented in Fig. 1. AEPs were recorded with maximal amplitude in this female in the SMC in the norm in response to tone bursts with filling frequencies of 0.8 and 1.6 kHz, and in the range of 2.5-2.8 kHz (Fig. 1, A). At the same time the curve of the a mplitude-frequency dependence in the PC had reliable

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Fig. 1. Changes in the character of the dependence of the amplitude of the AEPs of the associative areas of the neocortex on the filling frequency of the tone burst in the female following the birth of kittens during the lactation period. A) Averaged curves of the amplitude-frequency dependence of the AEPs of the SMC in the female in the norm (solid line) and following the birth of kittens (broken line); B) averaged curves of the amplitudefrequency dependence of the AEPs of the SMC in the first (1) and second (2) months of pregnancy. Abscissa: the filling frequency of the tone burst; ordinate: amplitude of the AEPs in normed form. C, D) Averaged curves of the amplitude-frequency dependence of the AEPs of the PC. Designations are those in A and B, respectively. maxima only at frequencies of 0.8 and 1.6 kHz (Fig. 1, C). Following the birth of kittens the curve of the amplitude-frequency dependence changed its form in the SMC as a result of an increase in the amplitude of the AEPs at particular frequencies. The amplitude of the AEPs increased practically twofold at frequencies of 1A and 5.0 kHz (Fig. 1, A). An increase in the amplitude of the AEPs upon presentation of tone bursts with filling frequencies of 1.4 and 5.0 kHz also took place in the PC (Fig. 1, C). However, this increase was less pronounced in absolute value than in the rostral division of the neocortex. The amplitude of the AEPs in both regions of the cortex practically did not change at frequencies of 0.8 and 2.5-2.8 kHz (Fig. 1, A, C). During pregnancy (Fig. 1, B, D), especially in the last month prior to delivery, a significant change in the amplitude of the AEPs also took place. However, by contrast with the transformations observed following the birth of the kittens, the increase in amplitude of the AEPs during pregnancy took place practically throughout the entire frequency range investigated~ A change in amplitude of the AEPs in the SMC in the period following the birth of the kittens also took place in the second female. But the range of frequencies in which the increase in the amplitude of the AEPs took place in this female was wider in the region of middle frequencies (1.0-1.8 kHz, with a maximal increase in amplitude at 1.0 and 1.8 kHz). At the same time, as was the case with the first cat, changes did take place in the PC, but were more weakly expressed than in the SMC. The significance of the changes in the frequency dependence of the amplitude of the AEPs in the regions of the cortex under study were evaluated by means of a two-way analysis of variance. The calculations were performed with respect to the frequency (filling frequency of the tone bursts) and time (time of complete investigation of the female) factors. The significance of the influence of each of the factors on the amplitude of the AEPs was assessed by calculating Fisher's coefficient. The results of the analysis showed that both the time factor and the frequency factor influenced the amplitude of the AEPs in the SMC significantly in both females. At the same time, the Fisher's coefficient obtained for the PC was as a rule lower than for the SMC. However, analysis by means of a two-way analysis of variance did not make it possible to establish whether the changes in the amplitude of the AEPs which take place under the influence of the dominant motivation are frequency-dependent. To resolve this question, the data obtained for each filling frequency of a tone burst obtained in the norm and following the birth of kittens were analyzed by the means of a one-way analysis of variance. The Fisher's coefficient in the first female was greatest in the SMC when tone bursts with filling frequencies of 1.4, 3.15 and 5.0 kHz were presented, and in the PC, when tone bursts with filling frequencies of 1.4 and 5.0 kHz were presented. In the second female, the maximal value of Fisher's coefficient aJso corresponded to those frequencies upon the presentation of which the greatest increase in amplitude was observed both in the SMC and in the PC. Thus, the changes in the amplitude of the AEPs, which were observed

257

following the birth of the kittens, in the regions of the neocortex investigated, were not identical when tone bursts with different fiUing frequencies were presented, i.e., they were frequency-dependent. Behavioral experiments with the aim of determining the significance of the vocalization of the kittens for the cats by comparison with other acoustic signals were carried out in parallel with the electrophysiological experiments in these females in the period following the birth of the kittens. Signals from the kittens, signals from the vocal repertoire of adult animals, and tone bursts with different filling frequencies were presented in isolated conditions from a tape recorder in the behavioral experiments to the cats in the last days of pregnancy and following the birth of the kittens. A search reaction in response to the presentation in isolated conditions of the signals of kittens was already observed in the females in the last days of pregnancy. If these signals were presented to a lactating female outside of the nest, the cat approached the nest, and only after examining it, ran to the source of the sound. The appearance of a search reaction in the direction of the sound source was also observed if the cat was in the nest with the kittens during the presentation of the signals. This reaction was most pronounced during the first presentation of the squeals of kittens. The females reacted in similar fashion to both the signals of their own and those of slrange kittens. Signals of kittens in the first days of life evoked the reaction in the most stable manner. Of the set of typical vocalization of adult animals (meowing, purring, wailing, growling, hissing, "yelping," and "spring songs") presented to a lactating female, only the "song" of the subdominant male ehcited a behavioral reaction similar to the search for the kitten's squealing. Possibly such a reaction is governed by the presence of the vocalization of the subdominant male of high-frequency components which are characteristic for the signals of kittens [15]. The presentation of tone bursts with different filling frequencies did not elicit the search reaction in a lactating female with the exception of a frequency -2.0 kHz, which is sometimes a formant in the signals of immature kitten [14]. However, the reaction to a tone burst with a filling frequency of -2.0 kHz was observed only in trials in the first days following the births of the kittens. It should be noted that the presentation of the signals to non-lactating and non-pregnant females did not elicit a search reaction in them. Thus, the search reaction in the lactating females we examined was elicited primarily by the presentation of signals of kittens, as compared with other natural and artifical signals of the repertoire used by us, which attests to the significance of the vocalization of kittens and the organization of the maternal behavior of these females. The significance of kittens' signals for a female is determined both by her state, as well as by the spectral composition of the vocalizations. It has been shown that both the character of the spectrum of signals as well as the absolute value of the frequency of the spectral constituents of the signal are important for the manifestation of maternal behavior [12]o The dependence of the behavior of lactating females on the filling frequency of the signals of pups has also been identified in mice [19]. On this basis it is entirely possible that the transformation of the frequency selectivity of the reactions in the associative areas of the cortex observed in the females following the birth of kittens is associated with a change in the biological significance of certain frequency ranges of sound signals for lactating females. In order to identify the mutual correspondence between the observed changes in the frequency selectivity of the reactions in the SMC and the spectral composition of the vocalizations of kittens, a recording of the squeals of the kittens of each cat was made. While in the nest next to the mother, the kittens as a rule did not squeal. Therefore, the majority of the signals were recorded when the kittens were isolated, when they were on the floor, or in the arms of an experimenter. In all 131 signals, recorded in the kittens from 2-9 days of age, were analyzed. The majority of the signals, according to the spectrograms obtained, had a two-formant structure (Fig. 2, A), which is characteristic for the signals of kittens of this age [14]. The first formant in 47 analyzed signals of a kitten of the first female was located primarily in the region of ~IA kHz (from 1.2 to 1.6 kHz); the upper formant was located in the region of 3.0 kHz (from 2.5 to 4.0 kHz) (Fig. 2, B). A change in the spectral maximum in the majority of these signals was observed in the range from 0.8-2.0 kHz. It should be noted that an overlapping of the region of change in the spectral maximum with respect to time took place in the vocalizations of this kitten for the high-frequency and low-frequency components of the signal in the range from 1.2-1.6 kHz. This distribution of the principal components of the signal relative to the frequency axis corresponds to the range of filling frequency of the tone bursts during the presentation of which, as was demonstrated by the analysis of variance, the most marked changes in the amplitude of AEPs were observed in the first female under the influence of the dominant motivation. Wider ranges of the distribution of the lower and upper formants, which also corresponded to the range in which the increase in the amplitude of the AEPs in the SMC following the birth of the kittens as compared with the norm, took place, were obtained for 84 signals recorded from two kittens of the second female. Overall, the first formant in all of the analyzed signals of the kittens aged 2-9 days was located within the limits of 1.02.0 kHz (Fig. 2, C); the upper formant was located within the limits of 2.2-5.0 kHz. The range of the distribution of the 258

Fig. 2. Spectral characteristics of the signals of kittens in the females examined. A) Spectrograms (above) and the oscillograms (below) of the signals of kittens; 1-4) exampies of recorded signals of kittens (along the vertical, frequency; vertical lines above the oscillograms represent the calibration, 100 msec); B) histogram of the distribution of the In'st formant in the signals (n -- 47) of a kitten of a female, the results of the investigation of which are presented in Fig. 1; C) histogram of the distribution of the first formant in the signals (n = 131) of three kittens of two investigated females. Abscissa: frequency; ordinate: number of signals. lower formant that was established in the signals of the kittens coincides with the results of previously performed bioacoustical investigations [12, 20], and corresponds to the change in the frequency selectivity of the reactions in the SMC in both females, primarily in the middle range of frequencies (1.0-2.0 kHz), which takes place under the influence of a dominant motivation. It should be noted that the range of the most pronounced increase in the amplitude of the AEPs of the PC in the lactating females also coincided with the frequency region in which the lower formant in the analyzed kitten signals varied. DISCUSSION

OF RESULTS

These experiments have enabled us to establish the possibility of a change in character of the amplitude-frequency dependence of the AEPs of the SMC and the PC in females during pregnancy and following the birth of kittens as compared with the norm, which attests to the influence of dominant motivation on the frequency tuning of auditory input in these regions of the neocortex. It should be noted that if an increase in the amplitude in practically all of the frequency regions studied was observed in the second half of pregnancy, the amplitude of the AEPs increased after the birth of the kittens only when tone bursts with filling frequencies in specific ranges were presented. The increase in the amplitude of the AEPs in the range from 1.0 to 2.0 kHz was common to both of the females investigated. Data exists which indicate that the spectral components around 2.0 kHz in the cries of newborn kittens are the ones most energetically expressed [14]. A wider range of variation of the lower formant in kitten signals was identified in other bioacoustical investigations [12, 20]. In this case, the fast formant has lower values, but they are not lower than 1.0 kHz. The spectral analysis carried out of the signals of kittens of the first days of life (born of the experimental females) revealed on ,

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the whole a similar range of distribution of the f'trst formant for all of the signals analyzed. But, at the same time, a distinct correspondence of the frequency ranges of the maximal change in the amplitude of the AEPs and the distribution of the first formant in the signals of their own kittens took place in each female. Taking this correspondence into account, and taking note of the paramount significance, established in the behavioral experiments, precisely of the signals of the newborn kittens in the manifestation of maternal behavior in the females investigated in the lactation period, it can be concluded that a transformation takes place under the influence of the dominant motivation in the frequency tuning of the auditory input into the rostral neocortex in accordance with the change in the biological significance of the signals of the kittens for the females in the period of rearing the offspring. The parallel recording of the AEPs in the parietal associative region of the cortex in response to tone bursts with different filling frequencies made it possible to establish that a transformation of the frequency tuning of the auditory input was taking place here. However, the increase in the amplitude of the AEPs in the PC in response to the tone bursts was less pronounced in absolute value than in the SMC. Consequently, the change in the biological significance of a specific class of acoustic signals (in this case, of kittens' signals), which takes place under the influence of a dominant motivation, is reflected in the reactions of both the SMC and the PC. However, the reflection of this characteristic of the acoustic signal is expressed to a different degree in each of the regions of the cortex investigated. Taking into account the role of the frontal cortex in the assessment of the biological significance of signals [4, 10], and of the parietal cortex, in the bringing of the body schema into correlation with extrapersonal space [3], it can be hypothesized that the differences in the observed changes in the reactions of these associative regions are predetermined by the different functional load imposed on the SMC and the PC in the organization of the adaptive behavior of an animal in the acoustic environment. In discussing the neuronal mechanisms which provide for the established frequency transformation of the auditory input into the SMC, it seems most probable that the influence of the motivational state on the reactions of the rostral divisions of the cortex is determined by the presence of projections from structures of the limbic system. But, at the same time, the question of the primacy of the identified changes in the amplitude of the AEPs of the SMC arises: are these changes associated with restmcturings of the functional organization in the specific structures of the auditory pathway, or, on the other hand, in the associative or limbic structures which have input into the rostral neocortex. Data exists regarding the stability of the afferent stream in the structures of the auditory pathway at different levels of alimentary motivation. Thus, it has been established that deprivation of food has no influence on the amplitude of the microphonic potential or on the total electrical reactions of the fibers of the auditory nerve, the cochlear nuclei, and the auditory cortex of cats when presented with clicks [22]. The examples, cited in a number of studies, of an increase in the sensitivity to certain sensory signals when they act upon the structures of the limbic system [18], are based, as a rule, on data concerning the systemic reactions of the organism, and therefore cannot be proof of a change in the threshholds of receptors or of the neurons of the specific formations of the sensory systems. At the same time, the possibility in principle has been established currently of the influence of many structures of the limbic system on the activity on the auditory pathway. A suppression of the total reactions of the inferior coUiculus and of the medial geniculate body takes place during electrical stimulation of the hippocampus [23]. The eleclrical stimulation of the amygdala in cats leads to inhibition of the activity of the medial geniculate body, which can be removed by the functional switching off of the cortex [24], which, in the opinion of the authors, point to the transmission of the influences along the corticofugal pathways. The administration of a steroid hormone was not only manifested in frogs in reproductive behavior, but induced an increase in the auditory evoked potentials of the midbrain as well [25]. However, the changes in the evoked potentials in response to stimuli with specific filling frequencies was manifested only at the very fast moment following repeat administration of the hormone. In considering the neuronal mechanisms which provide for selectivity in the functional organization of the auditory input of the SMC relative to the significant features of acoustic stimuli, a disproportional representation was not found in any of the frequency channels in the specific formations of the auditory system. By contrast with this, in the input of the auditory systems the reaction's selective character is assured in representatives of the amphibia, the majority of reptiles, and of the lower mammals (the marsupials and the bats), and is governed by the maximal density of the disposition of the hair cells in the corresponding frequency divisions of the cochlea [6, 9]. Thus, selectivity is manifested in the higher mammals in the functional organization of the sensory inputs into the rostral divisions of the cortex, and has an adaptive character, being transformed under the influence of the dominant motivation. Overall, in accordance with the data set forth above of this series of experiments, it can be concluded that the dominant motivation leads to selective changes in the functional organization in the auditory input of the SMC of the cat, changes which correspond to the biologically significant forms of auditory-motor integration.

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CONCLUSIONS 1. An increase in the amplitude of the AEPs in the SMC and to a lesser degree in the PC takes place in females in the lactation period following the birth of kittens, when tone bursts with a filling frequency in the 1.0-2.0 kHz range are presented. 2. The identified range of changes in the SMC in females in the lactation period corresponds to the range of the distribution of the first formant in the signals of their own kittens. 3. The change in the selective character of the reflection of the filling frequency of tone bursts in the AEPs of the SMC under the influence of the dominant motivation points to the possibility of restructurings in the organization of the auditor3, input of the SMC in keeping with the ongoing tasks of auditory-motor integration. LITERATURE CITED 1. 2. 3.

4. 5. 6. 7. 8. 9.

10. 11. 12. 13. 14. 15. 16.

17. 18. 19. 20. 21.

P. Ko Anokhin, The Biology and Neurophysiology of the Conditioned Reflex [in Russian], Meditsina, Moscow (1968). A.S. Batuev, The Neurophysiology of the Cerebral Cortex [in Russian], Izd-vo LGU, Leningrad (1984). A.S. Batuev, L. A. Vasireva, and O. P. Tairov, "The functions of the thalamoparietal associative system of the mammalian brain," In: The Evolution of the Functions of the Parietal Lobes of the Brain [in Russian], Nauka, Leningrad (1973), pp. 44-117. A.S. Batuev and G. A. Kulikov, Behavior in the Physiology of the Sensory Systems [in Russian], Vyssh. Shk., Moscow (1983). A.S. Batuev and G. A. Kulikov, "The frequency characteristics of auditory input to the motor cortex of cats," Dokl. AKAD. NAU-K SSSR, 223, No. 2, 505-509 (1975). N.N. Vasil'evskii, The Ecological Physiology of the Brain [in Russian], Meditsina, Leningrad (1979). V.S. Eganova, O. G. Baklavadzhan, and E. A. Khudoyan, "Comparative characteristics of hypothalamocortical and reticulocortical evoked potentials," Fiziol. Zh. SSSR, 64, No. 10, 1361-1371 (1978)o A.I. Karamyan and T. N. Solertinskaya, "Some features of the development of the hypothalamo-hemispheric interrelationships in the phylogenesis of vertebrates," Fiziol. Zh. SSSR, 50, No. 8, 962-974 (1964). A.I. Konstantinov and V. N. Movchan, "Frequency tunings of the auditory system of mammals (insectivores, Chiroptera, rodents)," In: Sonic Communication, Echolocation, Hearing [in Russian], Izd-vo LGU, Leningrad (1980), pp. 107-121. G.A. Kulikov, The Neurophysiological Bases of the Determination of the Biological Significance of Acoustic Stimuli, Vest. LGU, No. 21, 80-87 (1981). G.A. Kulikov, V. Yu. Klimenko, L. A. Vasireva, and I. M. Petrzhek, "Evoked potentials of the sensorimotor and parietal areas of the cortex of the cat in response to tonal stimuli," Zh. Vyssh. Nervn. Deyat., 34, No. 1, 89-98 (1984). V.N. Movchan, "Behavioral reactions of the cat to simple models of acoustic signals of kittens," Zh. Vyssh. Nervn. Deyat., 33, No. 4, 752-754 (1983). M.V. Motorina, "Investigation of hypothalamocortical associations in rabbits," Zh. l~vol. Biokhimo Fiziol., 4, No. 2, 187-194 (1968). N.N. Sokolova, "Spectral analysis of acoustic signals of kittens of various ages," Vest. LGU, No. 9, 70-79 (1979). N.N. Sokolova and G. A. Kulikov, "The acoustic signals of the domestic cat (Felis catus L.)," Vest. LGU, No. 15, 67-81 (1982). Vo M. Storozhuk, I. A. Vladimirova, T. V. Kozyreva, and S. V. Nederkina, "The functional associations of posterior hypothalamus and the amygdaloid complex with the sensorimotor cortex ," Zh. Vyssh. Nervn. Deyat., 18, No. 6, 1017-1025 (1968). K.V. Sudakov, Biological Motivations [in Russian], Meditsina, Moscow (1971). R. Hind, Animal Behavior [Russsian translation], Mir, Moscow (1975). G. Ehret and B. Haack, "Categorical perception of rat pup ultrasound by lactating females," Naturwissenschaften, 68, No. 4, 208-209 (1981). R.A. Haskins, "A causal analysis of kitten vocalization: observational and experimental study," Animal Behav., 23, No. 3,726-736 (1980). H. Kita and Y. Oomura, "Reciprocal connections between the lateral hypothalamic and frontal cortex in the rat: electrophysiological and anatomical observation," Brain Res., 213, No. 1, 1-16 (1981).

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22. 23. 24.

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L~ C. Oatman, "Effects of appetitive drive on auditory evoked potential: a replication," J. Comp. Physiol. Psychol., 87, No. 6, 1092-1099 (1974). K. Retj6, "Effect of limbic system upon the auditory evoked responses," Wiss. Martin. Luter--Univ. Halle-Wittenberg: Math.-naturwiss. R., 29, 199-202 (1976). Z. Shaoci, L. Xiangyue, and Y. Huizhen, "Study of inhibitory effect of amygdaloid stimulation of auditory response of medial geniculate body (MGB) and analysis of transmissive pathway of the said effect," Sci. Sinica, 26, No. 3,262273 (1983). S. Yovanof and A. S. Feng, "Effects of estradiol on auditory evoked responses from the frog's auditory midbrain," Neurosci. Lett., 36, No. 3,261-297 (1983).

BLOOD-FLOW AND PO2 IN THE POSTERIOR HYPOTHALAMUS OF CATS DURING PARADOXICAL SLEEP

L. S. Nikolaishvili, L. Sh. Gobeehiya, and M. I. Devdariani

UDC 612.821.7 + 612.824

It was found in chronic experiments in cats, using the recording of local blood flow and oxygen tension (p02) in the anterior and posterior hypothalamus in the sleep-wakefulness cycle, that when the phases of sleep are alternated, the changes in these parameters are in ch'fferent directions: the level of blood flow and the frequency of fluctuation of the p02 during paradoxical sleep increase in the posterior hypothalamus, while they decrease in the anterior hypothalamus. On the other hand, the opposite pattern is observed during slow-wave sleep. The muhidirectionality of the changes in local blood flow level and in the frequency of fluctuations of p02 in one and the same sleep phase indicate that they are of local origin and must be governed by functional-metabolic shifts in these structures; the functional state of the posterior hypothalamus during paradoxical sleep is assessed on this basis.

As is well known, the temperature of brain tissue rises during paradoxical sleep [8, 16, 17, 20], independent of the temperature of the environment [8, 16, 21]o It is presumed that this must be associated with a decrease in heat emission and with an increase of production of heat during paradoxical sleep [8, 9, 13, 20]. This process, according to the current hypothesis, must be accomplished by means of the activation of the posterior hypothalamus as a center of heat production [10, 15, 21], as a result of which a significant increase in its temperature should commence during this sleep phase [8, 16, 17, 20]. In the opinion of other researchers [14, 16], the increase in temperature of the posterior hypothalamus can be governed by an increase in the temperature of the incoming blood (due to a narrowing of the peripheral vessels during paradoxical sleep [8, 16, 21]), or, on the other hand, by an increase in the intensity of blood flow [16, 19]. Meanwhile, it is known that the temperature of the posterior hypothalamus is significantly greater than the temperature of the incoming blood in the norm in warm-blooded animals [7-9], while during paradoxical sleep the temperature of the latter is never higher than the temperature of this structure [8, 16]. Hence, it follows that an increase in blood flow should exert a cooling effect on the posterior hypothalamus, although as a result of the high metabolic heat production of the posterior hypothalamus [7, 8, 19], this effect ought to be insignificant, all the more so since an increase is not always observed in the blood flow, and, as has been found, the degree of increase in the temperature during increased blood flow does not differ from that which occurs during decreased blood flow [25]. Consequently, the increase in the temperature of the posterior hypothalamus can be associated with an increase in metabolic heat production [17, 20, 25]. I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR [AN GSSR], Moscow. Translated from Zhurnal Vysshei Nervnoi Deyaternosti imeni I. P. Pavlova, Vol. 39, No. 3, pp. 536-542, May-June, 1989. Original article submitted September 28, 1988; revision submitted October 21, 1988. 262

0097-0549/90/2003-262 $12.50 9 1990 Plenum Publishing Corporation