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E Grastyán

Publications and source records attributed to E Grastyán.

16 recordsLinked to original sources
PubMed1987

Septal deafferentation produces continuous rhythmic slow activity (theta) in the rat hippocampus.

Hippocampal EEG was recorded in behaving rats in which the brain stem afferents to the septal region were previously damaged. In these animals rhythmic slow activity (RSA or theta) was continuously present, including drinking and immobility. The average frequency of RSA, however, was significantly higher during running (8-9 Hz) than during drinking or awake motionless state (6-8 Hz). In normal rats irregular sharp waves, rather than RSA were present during drinking and immobility. The results suggest that brain stem afferents are necessary to suppress the rhythmic firing of septal "pacemaker" cells.

Afferent Pathways↗
PubMed1981

Hippocampal slow wave activity during appetitive and aversive conditioning in the cat.

The electrical activity of the dorsal and ventral divisions of the hippocampus was investigated quantitatively during the development of discriminative operant training and defensive conditioning. Signal-related (respondent, sign-tracking) and goal-directed (operant, 'voluntary') activities and their hippocampal electrical correlates were compared. Signal-related behaviour was accompanied by significantly higher frequency spectral peaks than lever press behaviour. Spectral peaks were higher during lever pressing in early stages of training as compared to criterion performance. In defensive conditioning overt sign-tracking behaviour disappeared but spectral peak shifts toward higher values upon signal presentation persisted. Comparison of dorsal and ventral hippocampal activity revealed high coherence values and similar frequency shifts during behaviour transitions. These findings argue against suggestions that a close relationship exists between elementary motor acts and hippocampal EEG.

Animals↗
PubMed1979

Hippocampal evoked potentials and EEG changes during classical conditioning in the rat.

Hippocampal evoked potentials (EPs) and EEG responses were studied in rats, using a classical conditioning paradigm (water, US), with a spatially discontiguous CS-US arrangement in order to separate the CS and goal-related responses. In early training, when the orienting score was high, the tone CS, instead of eliciting a definite EP, usually reset hippocampal theta activity in phase, i.e. theta rhythm became time-locked to CS. With further training, orienting activity (ORI) decreased to the preconditioning level, and this was associated with the recurrence of short-latency and high voltage hippocampal EPs, similar to those observed during habituation. This high voltage EP predicted that the animal would not orient any more towards CS. This correlation was confirmed by behavioural (satiation, shock US) and by pharmacological (scopolamine HBr, 2 mg/kg) treatments, all of which reduced the ORI score. Hippocampal EEGs also showed characteristic changes during conditioning. ORI towards CS was accompanied by higher frequency spectral peaks (9 c/sec) than response to US (7--8 c/sec). This correlation was seen both across sessions and within trials. We conclude that the above changes are related to orienting, attentional factors rather than to movement-related variables.

Animals↗
PubMed1979

Dynamic phase-shifts between theta generators in the rat hippocampus.

Winson [13] reported on two independent phase-reversed generators in the rat hippocampus. In the present study the synchrony between the two generators was investigated during the sleep-wakefulness cycle and during a behaviour-dependent discriminative learning task. Electrical activities derived from the CA 1 region and dentate gyrus were in phase during slow wave sleep but phase-reversed during the awake state and paradoxical sleep. The degree of phase-reversal was significantly higher during running than during lever pressing. These findings demonstrate that substantial changes occur within the hippocampal circuitry during dynamic shifts of behaviour.

Animals↗
PubMed1979

Auto-shaping or orienting?

Four experiments were carried out to study the development of the orienting response (OR) under different experimental conditions in the cat and rat. In Experiment I and II (cat) and Experiment IV (rat) classical CS-US pairing was used (with food, shock and water reinforcers, respectively). In Experiment III (cat) an instrumental pedal press response was brought under the control of a discriminative signal. In all four experiments the auditory CS was spatially discontiguous with reinforcement in order t o separate CS directed orienting responses from US related activities. Exposure to CS signalling food or water caused the animals to orient to it throughout conditioning (up to 700 trials) and this overt responding was absent if CS predicted aversive reinforcers. OR was consistently followed by goal (US) directed anticipatory activities. It is proposed that the CS directed auto-shaped response ("sign-tracking") is identical with the conditional orienting response, and that the spatio-temporal patterning of behaviors is influenced both by CS and US.

Animals↗
PubMed1979

Maintenance of signal directed behavior in a response dependent paradigm: a systems approach.

Rats were trained in a straight alley to repeatedly press a bar placed at one end of the alley until a discriminative signal (SD) appeared and to run for water reward (Rd) available at the other end. During training SD was spatially contiguous with Rd, then SD was placed above the bar (spatially discontiguous with Rd). In Experiment I subjects were trained for ten days, in Experiment II to equal level of performance before cue rearrangement. Experiment III applied systems analysis. Making SD spatially discontiguous with Rd caused abrupt and characteristic changes in many of the parameters observed (e.g., start-time, bar press perseveration, bar press topography, rearing, intertribal runs, defecation). If rats were initially trained under SD -Rd spatial discontiguity condition, making SD spatially contiguous with reward did not deteriorate their performance. It was concluded that: (i) rats learn and maintain responding to informative signals also in response dependent paradigms, (ii) spatial location of cue is of substantial importance for animals, and cue rearrangement will necessarily modify the topography of the learned response, (iii) the findings exclude the adventitious reinforcement explanation of signal directed behaviors, and question the validity of the concept of equivalent associability.

Animals↗
PubMed1979

The orienting-exploratory response hypothesis of discriminative conditioning.

Behavioral and electrophysiological manifestations occurring under conditions of spatial discontiguity of CS and reinforcement (or response) are described. It is concluded that the conflict or learning difficulties which arise in such situations are the result of a competition between the signal directed conditioned orienting response and the goal directed approach response which require different or opposite directional movements. Considerations are offered to prove that the complex orienting-exploratory response emerging as a result of reinforcement corresponds to the real conditioned response and accordingly the CS to a new independent goal with comparable attractiveness as the primary (consummative) goal. Arguments are (brought up against the validity of the stimulus substitution theory of signal directed activities. Findings obtained in fimbria-fornix lesioned animals are presented to show that the orienting-exploratory mode of coping with spatial tasks necessitates the intactness of the limbic system. The conclusion is drawn that an apparently more adaptive mode of behaving in spatial discontiguity, where the CS only releases or triggers the goal response (used occasionally by intact but exclusively by limbic lesioned animals) corresponds to a relatively inferior mode of adaptation.

Animals↗
PubMed1978

Evoked response correlate of symbol and significate.

Changing the source and intensity of the auditory signal to six trained cats responding to meaningful auditory stimuli permits exogenous and endogenous processes in the auditory evoked potential to be separated. For short-latency exogenous processes, latency and amplitude depend on the parameters of the physical stimulus. However, the amplitude and shape of longer-latency endogenous processes are essentially independent of the location and intensity of the signal source and seem to be invariant concomitants of the significance of the signal.

Animals↗
PubMedDate not supplied

[Evoked potentials during the elaboration of a conditioned reflex to hippocampal stimulation in rats].

In experiments on 9 rats, the study of evoked potentials (EPs) of the CA1 field of the dorsal hippocampus to stimulation of its symmetrical part serving as a signal of drinking conditioned reflex (CR) showed that during reflex elaboration, the amplitude of the main EP components significantly decreased; CR did not appear when the population spike (PS) was absent in the hippocampal response. PS always accompanying CR was not specific only of it, it was also recorded at other behavioural reactions. Changes of fascia dentata EPs in the process of CR elaboration to stimulation of its symmetrical part consisted in decrease of the initial negative wave and increase of the positive one. The obtained data point to a significant reconstruction of excitatory and inhibitory inputs to the hippocampus and fascia dentata under the influence of conditioned activity.

Animals↗