Showing papers in "Acta Neurobiologiae Experimentalis in 1989"

The development of sustained attention in children might be related to the maturation of frontal cortical functions.

Abstract: The relationship between the development of sustained attention and the ability to inhibit responding to external stimuli was investigated in seventy five children, 8, 10 and 12 years old. An important period in the development of both functions is between 8 and 10 years of age. A positive correlation was found between the number of signals detected (sustained attention) and the number of successfully suppressed reflexive saccades to the peripherally located target (the ability to inhibit responding to external stimuli).

Speed control in quadrupedal locomotion: principles of limb coordination in the dog.

Abstract: Key wo~cls: locomotion, speed control, interhnb coordination Abstract. Long distance, overground locomotion in the dog was ob- served and analyzed using the two dimensicmal gait diagram method. Though the velocity of locomotion chosen by the animals over a 1,000 m course varied, a preferred speed generally emerged and was used during most of the experiment. This animal-specific preferred overground ve- lociiy was strongly correlated with the animal's limb lengths, and cor- responded to the minimum observed swinging velocity of the limbs. Changes in the pattern of limb coordination during three-limb locomo- tion were also investigated. Depending upon which limb was restrained, dogs used trot-like or gallop-like galts which exhibited the same temporal and spatial phase differences as were observed during normal locomotion. However, stride length and swing-stance durations were increased rela- tive to those observed in four legged locomotion. Animals with an addi- tional 2 kg weight trotted slowly, but no significant changes in limb movement parameters were found. Locomotion studies performed in darkness resulted in an immediate switch from asymmetrical (galloping) to symmetrical gaits (walking and trotting). These gaits allow for pre- cise foot placement.

Serotonin depletion with P-chlorophenylalanine in the cat: effects on carbachol-induced defensive behavior and regional brain amine content.

Abstract: Serotonin (5-HT) depletion with p-chlorophenylalanine (p-CPA) (3 X 150 mglkgll2 h i.p.) in the cat resulted in an increase in the carbachol-induced growling response 36 h after the last injection. Besides important depletion of 5-HT in the anterior and posterior hypo- thalamus, midbrain and amygdala, and 5-hydroxyindoleacetic acid (5- HIAA) in the anterior and posterior hypothalamus and midbrain, dop- amine (DA) level significantly increased in the amygdala and posterior hypothalamus with tendency to increase in the anterior hypothalamus and midbrain. No changes in noradrenaline (NA) level were observed. The results indicate that the carbachol-induced defensive behavior significantly increased as a consequence of reduction in the 5-HT system activity. The changes in DA content indicate that there are interactions between the 5-HTIDA systems.

Differential effect of the damage to the lateral hypothalamic area on hippocampal theta rhythm during waking and paradoxical sleep

Abstract: Hippocampal theta rhythm was analyzed in rats subjected to bilateral, electrolytic lesions of the lateral hypothalamic (LH) region at different levels of its rostro-caudal axis. It was found that damage to the LH disturbed the hippocampal theta activity both during waking and paradoxical sleep. The main effect consisted in the lowering of the theta frequency. Typically, a decrease of frequency was accompanied by an increase of amplitude during waking, and an amplitude fall during paradoxical sleep. Extensive lesions increased the amount of rhythmic slow activity during waking and induced long trains of immobility-related theta. The general picture of impairments of the hippocampal theta rhythm in particular subjects depended on the size of the lesion and, to some extent, also on its localization within the LH. It is concluded that LH region contains systems of fibers which transmit impulses from the brain stem reticular formation to the prosencephalic structures generating the rhythmicity of theta.

Influence of environmental temperature and photoperiod on temporal structure of sleep in corvids.

Abstract: A survey is presented of the author's own investigations on the effects of ambient temperature and photoperiod on sleep in corvids. Daily sleep patterns of rook, Corvus frugilegus and magpie, Pica pica have been studied electrographically under natural ambient conditions of light and temperature. The daily amount of total sleep time (TST) was positively correlated with night duration, whereas the proportion of TST spent in paradoxical sleep (PS) was strongly reduced in lm ambient temperature (T,). The mean duration of sleep cycle was found to be positively correlated with T,. The temporal structure of PS in contrast to that of slow wave sleep (SWS) underwent dramatic changes due to cold exposure. In cold PS episodes appeared randomly through- out the night. The systematic trend observed in nocturnal distributions of SWS did not vary significantly when T, changed from thermoneutral to moderate cold. This study provided indirect support for the view that PS in birds, like in mammals, is associated with inhibition of thermo- regulatory responses.

Delayed response to light stimuli in binocularly deprived cats.

Abstract: Cats binocularly deprived of pattern vision, born and cagereared in the laboratory, were trained on the delayed response task involving light stimuli with 0-, 5-, and 15-s delay. Control cage-reared animals, also laboratory born were not deprived visually. No significant group difference was found in the delayed response learning, both groups performing poorly, as compared to the earlier data reported on cats reared without environmental restriction. The groups differ, however, in reaction time (RT), as in the visually deprived animals a lower proportion of responses with shorter RT was observed than in the controls. Conversely, for responses to the actual light stimuli a higher proportion of shorter RT was found in the deprived animals than in the controls.

Is the 45 degrees-oblique a third dominant direction?

Abstract: Vertical and horizontal are widely accepted as dominant directions or norms of visual orientation in the frontoparallel plane. They are supposed to cause a normalization effect consisting in the apparent rotation of a tilted straight line towards the nearest dominant direction. The evidence for tilt normalization towards the vertical or horizontal visual meridia is indirect. On the other hand, human observers are very sensitive to departures from the vertical and horizontal, which means that most orientations in the frontoparallel plane are termed tilted rather than vertical or horizontal. By measuring directly the orientation of dot patterns we found that estimated orientation was systematically biased towards the nearest 45 degrees-oblique visual meridian. This finding is interpreted as evidence for the existence of an oblique norm in visual tilt.

Alteration in the pattern of locomotion following a partial movement restraint in puppies.

Abstract: KCU ~uords: locomotion, movement restraint, gait alteration Abstract. The pattern of locomotion following a partial movement re- straint was studied in five mongrel puppies. The locomotion of the ani- mals was characterized by enforced pacing during the restraint peri-od and exhibited significant, time dependent gait alterations after removal of the restraint. These changes involved gradual recovery to normal trotting. The time course and the degree of recovery in the animals were dependent on the period of movement restraint. Puppy that was forced to practice pacing for only two months switched almost instantaneously to the normal trotting, whereas in those dogs with a longer selective movement restraint, a significant long lasting incidence of pacing was observed. The study describes an animal model which can be useful as tool in future studies of the plasticity of motor system and its basic me- ch:~nisms in various physiological conditions.

EEG afterdischarge patterns and performance of the avoidance response in hippocampally kindled cats.

Abstract: The relation between EEG limbic after,dis,charge patterns and the performance of avoidance re,sponse was studied in eight hippocam- piilly kindled cats. Five basic types of EEG afterdischarge patterns were identified in the hippocampal formation: (i) continuous, 2-41s high am- plitude spikes or spike and wave complexes; (ii) continuous, 4.5-12/s high amplitude spikes or spike and wave complexes; (iii) dysrhythmic pattern: disorganized irregular spiking, mixed with slow waves at 3-20/s frequency; (iv) conti.nuou,s, 20-301s comb-like shaped spiking of mo- derate amplitude, and (v) trains of high amplitude and frequency irregu- lar spikes, lasting for 0.2-1 s. followed by EEG depression lasting 0.3-1 s. The performance of conditioned response was tested during first 10 s, of afterdischarge development after kindling electrical stimulation of the hippccampus. A statistically significant relatio'n was observed between the EEG afterdischarge patterns seen at the beginning of afterdischarge formation (basically types I, I1 and 111) and the performance of avoidan- ce response, with greatest probability of the response failure with type I11 of afterdischarge pattern. Latencies of thd avoidance responses were prolonged during afterdischarges, in comparison to latencies observed before and after kindling hippocampal stimulation.

Nucleus limitans thalami--comparative anatomical study.

Abstract: Cyto- and myeloarchitectonics as well as acetylcholinesterase activity of the nucleus limitans thalami - an important part of the nociceptive system - were studied in insectivora (Sorex araneus, Erinaceus euro- paeus, Talpa europaeus), rat, rabbit, cat, monkey and man. Our results suggest that nucleus limitans is phylogenetically a rather new structure. In insectivora and in the rat we could not find any evident group of neurons resembling nucleus limitans. In the rabbit and cat nucleus li- mitans is composed of few layers of elongated cells. In macaca and man it is a larger, more complicated structure possessing various types of neurons, and arranged into many layers.

The sensory projections to the frontal association cortex in the dog.

Abstract: Afferents to the frontal association cortex (FAC) from structures involved in olfactory, visual and auditory functions were studied in 37 dogs using the method based on the retrograde axonal transport of horseradish peroxidase. Separate injections to FAC or to the mediodorsal thalamic nucleus (MD) showed that sensory afferents could reach FAC by two channels: by direct cortico-cortical projections and via MD. The olfactory input originating in the primary and secondary olfactory cortex run to FAC through both transcortical and subcortical pathways, while some subcortical structures, such as the anterior olfactory nucleus and olfactory tubercle, send abundant afferents to FAC only via MD. The visual projections taking their rise from a few separated areas of the visual association cortex reach FAC only transcortically. Most significant subcortical projection to FAC from the lateral geniculate nucleus, were transmitted via MD. On the contrary, auditory information was sent to FAC mainly through direct cortico-cortical pathways originating in the auditory association areas. Auditory input related by MD was very weak and originated from a limited region of the some cortex. Thus, independently from the way of transmission, auditory and visual projections terminated always in the dorsal zone of FAC, whereas the olfactory projection terminated in its ventral zone.

Differential projection from the motor and limbic cortical regions to the mediodorsal thalamic nucleus in the dog.

Abstract: The cortical afferents to the mediodorsal thalamic nucleus in the dog were studied by using horseradish peroxidase. Small injections allowed to establish two specific projection zones connected separately with the lateral and medial segments of the nucleus. The lateral segment received the major projection from the dorsal half of the hemisphere. It included premotor and part of the motor cortices in the anterior sigmoid gyrus and precruciate areas as well as the presylvian cortex. The medial segment of the nucleus was innervated by the limbic areas of the ventral half of the hemisphere. These areas included the medioventrally located genual, subcallosal and piriform cortices, as well as the cortex of the ventral bank of the anterior rhinal sulcus and the caudal part of the orbital gyrus. The cortical fields situated between these two main cortical zones, both on the lateral and medial surfaces (rhinal and sylvian sulci and anterior cingular gyrus, respectively) sent projections to both medial and lateral segments of the nucleus. These results indicate that in the mediodorsal thalamic nucleus may take place the integration of information from two functionally defined systems, the motor and limbic ones.

Properties of the visually driven neurons of cat's hippocampal regions CA 1 and CA 3.

Abstract: Neurons in areas CA 1 and 3 of cat's dorsal hippocampus were studied. Fifteen percent of the investigated cells were influenced by visual stimuli. Eighty five such neurons were investigated. The organization of their receptive fields was tested with stationary and moving visual stimuli. Twenty eight percent of neurons had small receptive fields (10-20 deg square). Forty one neurons responded to stationary flashing spots. They were ON-OFF, ON and OFF types with phasic (66%) and tonic (34%) characteristics. Seventy five responded to dark and bright stimuli moving across their receptive fields. Twenty five neurons were direction-sensitive and 21 responded better to the dark moving stimuli than to the bright ones. No significant differences in the response properties of neurons in the CA 1 and CA 3 fields were observed.

Augmented breath provoked by lung inflation in cat.

Abstract: The rate of occurrence and magnitude of provoked augmen- ted breath (PAB) were studied as the function of lung expansion applied at different intervals (15-180 s). Together with phrenic nerve activity (Phr.) the activities of recurrent laryngeal (RL) and hypoglossal (Hyp) nerves were investigated during PAB. The experiments were carried out in 10 cats anesthetised, paralysed and artificially ventilated by means of a phrenic nerve-driven respirator. Lung expansion was performed by increasing the gain of the servorespirator for one breath. PAB could be elicited when the interval between subsequent inflations was longer than 30 s ("refractory time"). We did not find out any consistent rela- tionship, common for all experiments, between the value of the interval (> 30 s) and the rate of occurrence of PAB as well as between the volume of lung inflation and the magnitude of PAB. During PAB regi- stered on Phr., activities of RL and Hyp were usually inhibited. It is concluded that PAB depends upon the instantaneous balance of excitatory and inhibitory vagal influences centrally differentiated at various respi- ratory outputs. Its amplitude and occurrences are therefore difficult tcr predict. Thus, PAB can be hardly compared with spontaneous deep breath. INTRODUCTICN

Hemispheric differences in evoked potentials to faces and words.

Abstract: ception Abstract. Sixteen right-handed subjects (8 male and 8 female) were asked to compare two faces or two words successively presented at the centre of the visual field. The brain's electrical activity was recorded from the scalp at symmetrical points of the left and right occipital lobes (01 and 0,) and posterior temporal lobes (T, and T6). The reference electrode was placed on the scalp vertex (C,). A multi-factor analysis of wariance revealed significant hemispheric differences of the N243 and P406 amplitudes. For the N2%3 the opposite asymmetry was found for faces and words. For the face matching the N243 amplitude was higher in the right hemisphere, whereas for word matching it was higher in the left hemisphere. For the the asymmetry was in the same direction both for faces and words, with higher amplitude in the left hemisphere. In the case of face matching the hemispheric difference in the P406 was more pronounced, due to a negative shift of the potential in the left hemisphere in the latency range of 200-1,500 ms. Functional asymrpetry of the brain in face perception thus appears to be reflected in the brain's electrical activity. We conclude that differentiation in hemispheric func- tions takes place while encoding information about stlmulus in short term memory.

Contralateral connections of the dog's frontal association cortex.

Abstract: Keu words: frontal association cortex, contralateral connections, dog, HRP method Abstract. We studied the topography of contralateral connections of both prefrontal and premotor regions of the dog's frontal association cor- tex (FAC) by charting distributions of retrogradely labeled cells following unilateral MRP injections to various areas of this cortex. Generally, in the contralateral hemisphere the labeled cells were most numerous in the FAC areas localized homotopically to the injection sites, less numerous in FAC areas heterotopic to injections, and the least numerous in cortical areas situated outside the I'rontal lobe. The nonfrontal areas which project to the dorsal azd ventral FAC dlffer from one another. Dorso-caudal parts of the cingular and insular areas, as well as the auditory, somatosensory and visual association cortices project to the dorsal FAC, while the ventro-rostra1 parts of the cingular and insular areas, together with the prepiriform and periamygdaloid areas of the olfactory cortex as well as the subcallosal area send their axons to the ventral FAC. Thus, the dorsal and ventral FAC areas are supplied by contralatera! afferents originating from different cortical areas. Similar organization of ipsilateral FAC connections was described previously.

Controversies on the subject of slave-raids in amazon ants (genus Polyergus).

Abstract: The paper contains a polemic with the view expressed by Talbot, Wilson and Topoff and his co-workers, who maintain that the existence of scouts and their leading directing in slave-raids of the American Polyergus' species is fully proved In particular we do not agree with Talbot's and Wilson's argument that following by the ama- zons of the scent-trail prepared from the crushed bodies of their nest- mates indicates that the amazon raids follow the trails of scouts Con- sidering the results and notions of the above-mentioned authors, we maintain that the mechanism of slave-raids in the American amazons is far from clear

Effects of a weak diffuse-brain-stimulation on insomniacs with vibration syndrome.

Abstract: To verify the efficacy of a weak diffuse-brain-stimulation (DBS) method that was specially devised by this research team, a weak DBS was administered to seven male inpatients, who had vibration syndrome due to a prolonged use of a vibratory tool and who were simultaneously complaining of insomnia. Sleep data obtained from the polygraphic recordings on the DBS-treated night were compared with those on the pseudo DBS-treated. As the result, this DBS method proved to be effective in improving patients' sleep initiation and/or maintenance, and also their subjective ratings on the quality of actual sleep. In conclusion, the present DBS was determined to produce a decrease in the sympathetic tone which is needed at the onset of sleep.

Modulation of single cell responses and neuronal interactions produced by iontophoresis of glutamate in adult cat visual cortex.

Abstract: Single neuron responses and interneuronal coordinations after microiontophoretic injections of L-glutamic acid (glutamate) were examined in cats striate cortex with an aid of multielectrode extracel- lular recording and crosscorrelation analysis. The effects of 15 min long stimulation with glutamate were compared with spontaneous mutability observed within at least 1.5 h. A mutability coefficient was suggested for quantitative data analysis. Spontaneous changes were analyzed in 144 neuronal pairs in two anesthetized and seven pretrigeminal cats. Differences in spontaneous mutability between these groups were not significant. Fluctuations of crosscorrelograms were smaller than fluclu- ations of poststimulus time histograms (PST). The type of correlogram and receptive field preferred orientation and direction never changed. The effect of glutamate injection was studied in 157 neuronal pairs in four anesthetized and eight pretrigeminal cats. Excitatory responses were observed in 6S0/o of neurons, inhibitory in 18O/o. The excitatory response to glutamate was accompanied with enhanced visual response in 47O/(u of cases and with reduced visual response in 18O/o. Crosscor- relogram strength was reduced in 43O/0 of pairs with excitatory response lo glutamate and increased only in 23O/@. After the termination of ionto- phoresis a persistent increase of the shared input coordination was ob- served in two pairs in anesthetized animals and in three pairs in pretri- geminal cats. The appearance of direct excitatory coordination was found in one case in pretrigeminal cats. Alterations of PST histograms did not

Hippocampal rhythmical slow activity during instrumental responses with sexual reinforcement in male rats

Abstract: The hippocampal EEG activity was recorded In male rats during the response-contingent reinforcement of a female. The instru- mental response was a bar-pressing on a fixed-ratio-10 reinforcement schedule. The frequency of bar-pressing tends to increase during the sue- ceeding copulatory series. The similar phenomenon was observed in the frequency of the hippocampal slow activity (RSA) accompanying the bar-pressing and the pursuit of the female. This tendency was most con- spicuously present during the first copulatory series but became less evident during the following ones.

Is it advisable to use sorbitans in the investigation of the brain mechanisms

Abstract: Injection of O.lO/o saline solution of Tween 80 i.p. (3 X 3 cm3/kg/12 h) in the cat decreased the carbachol-induced growling response 36 h after the last injection. The content of 5-hydroxyindolea- cetic acid (5-HIAA) increased in the hypothalamus, midbrain and amy- gdala, which indicates the increase in serotonin (5-HT) turnover and the 5-HT system activity. The results imdicate that Tween 80 causes per se both behavioral and neurmhemical changes. Therefore, it is inadvisable to add sorbitans to the solutions used in the investigation of the brain mechanisms.

Stimulus modality effects on transformations of conditioned enhancement and conditioned suppression in rats.

Abstract: Unconditioned and conditioned effects of house-light offset and acoustic white noise on barpressing behavior maintained by intermittent food reinforcement were tested in male hooded rats. Presentations of these stimuli prior to their acquiring signal value initially tended to depress and then to enhance barpressing rate, but generally the rate of the on-going barpressing was lower during the light offset then during noise presentations. Subsequently, one stimulus was used to signal continuous food reinforcement, evoking conditioned enhancement, and the other to signal inescapable footshock eliciting conditioned suppression of barpressing. The enhancement was acquired more rapidly than the suppression, independent of the stimulus modality used. The stimulus modality effect emerged when the continuous food reinforcement was withdrawn, since enhancement elicited by light offset extinguished more rapidly than elicited by noise. The stimulus modality effect was stronger when the other stimulus continued to signal pain and was attenuated when conditioned suppression was also extinguished. During the next stage of the experiment, the signal values of the conditioned stimuli were reversed, resulting in easy transformation of conditioned suppression into conditioned enhancement and vice versa. The stimuli used and changes in their signal values exerted clear effects on the rate of barpressing during intertrial intervals and this, in turn, somewhat modulated the behavioral effects of the conditioned stimuli. These results indicate that unconditioned effects of the stimuli on the behavior interact with their properties acquired in the course of conditioning.

Effect of GABA muscimol and picrotoxin on electrical activity of the medial preoptic area in unanesthetized rats.

Abstract: Intracranial cannula along with electrodes was stereotaxically implanted in medial preoptic area of male rats The electrical activity of mPOA was recorded before and after microinjection of GABA (05 micrograms/02 microliters), muscimol (05 micrograms/02 microliter), picrotoxin (025 micrograms/02 microliter) and their respective controls Generalized slowing with an increase in amplitude appeared with GABA and muscimol, while picrotoxin produced just the reverse, ie fast activity Thus the mPOA seems to be vulnerable to GABAergic compounds and supports the diversity of physiological and behavioral functions

Diversity of kindling effects: EEG manifestations in cats during kindling in the hippocampal formation.

Abstract: The formation and subsequent development of after-dis- charges (ADS) and spontaneous interictal spikes was investigated in a group of ten kindled cats. The electrodes used for electrical stimulation and EEG recording were located in various parts of the hippocampal formation: in the hippocampal gyrus, dentate gyrus, subiculum and en- torhinal cortex. The animals were stimulated once daily with 1 s trains of 501s electric pulses. The choice of stimulating electrodes, stimulating currents and, in some cases, monitoring of the stability of stimulating conditions was aided by recording hippocampal field potentials evoked by intrahippocampal electrical stimulation. A subgroup of 5 cats was stimulated at AD threshold or near threshold currents of constant in- tensity. The following patterns of AD development were observed: (i) a long lasting initial phase of stable, a few second-long ADS with sub- sequent development, culminating in prolonged ADS and complex partial or secondary generalized tonic clonic seizures, after 80-120 days of kin- dling; (ii) stable pattern of brief ADS (0.3-1.5 s duration) during 120 days of kindling; (iii) gradual development of initially brief ADS (about 5 s) into longer lasting ADS (about 35 s) associated with complex partial sei- zures, during 220 days of stimulation. Spontaneous interictal spikes de- veloped in this subgroup after 16-15 days of kindling. The second sub- group of 5 animals was subjected to stimulation with gradually increa- sing AD subthreshold currents. In two animals of this subgroup sponta- neous EEG discharges of isolated spikes and clusters of high frequency

The EEG time series parametrization method in the study of nociception

Abstract: A new method of EEG time series parametrization was proposed. The EEG rhythms were described in terms of frequency, amplitude and damping. These parameters were used in multivariate analysis of variance in order to estimate the group differences in terms of Mahalanobis distances. The rhythm diagrams were constructed and their advantages in comparison with averaged power spectra were dis- cussed. The proposed method overcomes the difficulties connected with the arbitrary division of spectrum into the frequency bands. The use- fulness of the method in the study of nociception was tested. The effect of nociceptive stimulation in the four brain structures: sensorimotor cortex, ventro-postero-lateral thalamic nuclei, midbrain reticular form- ation and periaqueductal gray was investigated. The influence of atro- pine and mecamylamine administered locally was studied.

The role of body turn-brightness associations in the effect of scopolamine on response-to-change in the rat.

Abstract: We explored further the different effects of anticholinergics on response-to-change in the passive and active tests. We hypothesized that body turn-brightness associations are formed in the active but not in the passive test, where the turns were prevented by transparent partitions blocking maze arm entrance. This difference might account for the resistance of the active test performance to anticholinergic drugs. To examine this idea, the passive test conditions were modified so that body turns were possible. However, scopolamine (1.0 mg/kg) interfered with response-to-change performance to the same extent as observed previously in the typical passive test procedure. Thus, body turn-brightness associations are not the source of resistance of active test performance to cholinergic receptor blockade.

Properties of visually driven neurons in cats pretectal region.

Abstract: Properties of visually driven neurons in the cat pretectal region were studied. A detailed investigation of the receptive field (RF) structure revealed, in the majority of neurons, irregular shapes of RF contours. Dark-sensitive and bright-sensitive zones of a neuronal RF had different spatial locations. The majority of pretectal neurons were movement-sensitive and reacted weakly to stationary flashing spots. Although no clear-cut orientation sensitivity was found in the pretectal neurons, some orientations of motion were, nevertheless, more effective. In some cases a non-directional response could be transformed into a directionally-sensitive one by changing the orientation of motion. Out data confirm earlier observations that the pretectal region is involved in the central processing of visual information.

The inhibitory components in the responses of the lateral suprasylvian area neurons to moving stimuli in cats.

Abstract: The inhibitory components in the neuronal responses of the cat's lateral suprasylvian area (LSA) to moving bright and dark stimuli were investigated. The LSA neurons could be divided into two groups. Neurons of the first group (33°/oi) do not reveal spatial displacement of the inhibitory zones and show displacement of the discharge centers in the receptive field only for one polarity of contrast of mwing stimuli, either brighter or darker than the background. The second group (67O/m) contained the neurons which showed a spatial displacement of the in- hibitory components and discharge centers in the receptive field for either polarity of contrasts of the moving stimuli. Tested with stationary flashing stimuli, the majority of neurons in both groups had overlapping ON-OFF discharge regions within their receptive fields. The results obtained with moving stimuli of different speeds and with the masking method suggest the rebound origin of the inhibitory responses m LSA neurons.

Effect of after-discharge EEG patterns on performance and latency of the conditioned avoidance response in hippocampally kindled cats.

Abstract: The relation between different EEG after-discharge patterns and memory retrieval of the conditioned avoidance response was studied in 8 hippocampally kindled cats. The after-discharge patterns were classified into 5 basic EEG types. The relation was analyzed in three different situations: A, at the conditioning stimulation onset, B, at the conditioning stimulus termination, and C, when conditioning stimulus onset and termination were studied within the same type of EEG pattern of after-discharge. The moment of presentation of the conditioning stimulus was determined by the type of EEG after-discharge pattern. Significant relation was observed between reflex performance and type II and III EEG AD types. The type II (4.5-12/s spiking activity) was associated with a greater proportion of positive responses if presented on the uniform background of EEG after-discharge patterns. During the type III pattern (EEG dysrhythmia), there were more negative than positive responses in all the three experimental situations, especially if the type III EEG pattern was observed at the time of conditioned stimulus termination. The latency of reflex performance measured in the experimental condition C (the same pattern of EEG during conditioning stimulus onset and termination) was longer during the type II EEG pattern of after-discharges than the latencies found during type III EEG activity and in the control group. During type III pattern associated with greatest proportion of response failures there was, however, no increase of reflex latencies. The results suggest differential effect of different EEG after-discharge patterns on memory retrieval of the well established conditioned avoidance response in cats.