Dye coupling evidence for gap junctions between supramedullary/dorsal neurons of the cunner, Tautogolabrus adspersus.
Explore the source record for details and available documents.
Animals↗
Biomedical subjects
D E Arnolds
Publications and source records attributed to D E Arnolds.
A functional link between the limbic cortex and ventral striatum: physiology of the subiculum accumbens pathway.
Parallel electrophysiological and anatomical tracing studies on the projections from the hippocampal formation to the ventral striatum in the cat, were carried out with the aim of defining the nature and organization of the motor interfaces of the limbic cortex. In this context the main pathway was found to be that from the subiculum to the N. Accumbens; electrophysiological characteristics of this pathway are reported in the present study. This well organized pathway is primarily of an excitatory nature and consists of slow conducting fibers (1-2 ms-1). Three types of response patterns of single Accumbens units to subicular simulation were found: units which responded with a burst of action potentials (the majority); units which responded with iterative bursting; units responding primarily with an inhibition of firing. Often the primary excitatory response was followed by a decrease in firing rate. Analysis of Evoked Potentials indicate that the subicular inputs induce a monopolar positive field within the N. Accumbens; in combination with the evidence obtained from current source density (CSD) analysis these data suggest the following activation model: subicular inputs evoke depolarization of synapses lying peripherally in the dendrites of stellate neurons provoking peripheral sinks which form a concentric shell around sources at and in the neighbourhood of the cell bodies. In addition to the subiculum-Accumbens pathway evidence was also obtained for an excitatory input from the Entorhinal cortex to the N. Accumbens. Furthermore, an excitatory pathway from the prepyriform cortex to the olfactory tubercle was also electrophysiologically identified.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Hippocampal EEG and motor activity in the cat: the role of eye movements and body acceleration.
In cat the relation between various behaviours and the spectral properties of the hippocampal EEG was investigated. Both EEG and behaviour were quantified and results were evaluated statistically. Significant relationships were found between the properties of the hippocampal EEG and motor acts (walking, sitting, eating, stepping and eye movements). These results were compared with those obtained in dog under similar experimental circumstances. Species differences were found particularly regarding the fact that in the cat a dissociation between frequency and amplitude parameters was obtained for some behaviours; this may explain why appreciable differences in the visual interpretation of EEG records of different species are often reported. A simple model of the modulation of hippocampal EEG by brainstem inputs is presented. Particular attention is paid to species differences regarding the anatomy and physiology of the pathways involved in this modulation. It is concluded that in cat a strong relation exists between the modulation of spectral properties of hippocampal EEG and vestibular inputs and/or eye movements. The effects of body acceleration on hippocampal EEG are put in evidence and related to theories of hippocampal function.
Acceleration↗
The spectral properties of hippocampal EEG related to behaviour in man.
In an epileptic patient with depth electrodes placed in the hippocampal formation we observed the following: (1) There existed a significant peak in the theta band of the hippocampal EEG of this subject under a number of behavioural circumstances. (2) Four different behaviours were performed at two degrees of intensity. Whenever the values of a certain spectral parameter associated with a low or a high intensity behaviour showed a significant difference, the higher value corresponded with the more intense version of the behaviour. (3) The frequency and rhythmicity of the hippocampal theta component during writing was consistently higher than during sitting or walking. The amplitude was smaller. (4) In a word association task the amplitude, frequency and rhythmicity showed a significant rise during the period of silence immediately following the question and preceding the answer.
Adolescent↗
Hippocampal EEG and behaviour in dog. I. Hippocampal EEG correlates of gross motor behaviour.
It was shown that rewarding spectral shifts (i.e. increase in amplitude or peak frequency of the hippocampal EEG) causes a solitary dog to show increased motor behaviour. Rewarded spectral shifts concurred with a variety of behavioural transitions. It was found that statistically significant modulations occur in the spectral properties of the hippocampal EEG correlated with: (1) the transition from walking to standing; (2) the transition from standing while eating to walking away from the food dish; (3) the increase in speed of a walking dog, caused by rewarding the animal; and with (4) each head movement in a learned series of head movements. Thus behavioural transitions to a more active state are accompanied by an increase of amplitude, frequency and rhythmicity in the theta band of the hippocampal EEG; behavioural transitions to a less active state show the inverse relationship with the hippocampal EEG. A close relationship between modulations of the dog's hippocampal EEG activity and elementary motor acts is stressed. The hypothesis is put forward that the spectral properties of the hippocampal EEG reflect the degree to which a number of motor and sensory structures in the limbic midbrain and brain stem are active.
Animals↗
Hippocampal EEG and behaviour in dog. II. Hippocampal EEG correlates with elementary motor acts.
A positive correlation has been shown between the speed of forced stepping on a conveyor belt and the amplitude and frequency of the concomitant hippocampal EEG. Significant modulation in the spectral properties of the dog's hippocampal EEG has been found in relation to 3 elementary motor acts: stepping, respiratory movements and a reflex movement in reaction to linear acceleration of the animal. The findings support the idea that within a certain experimental situation the hippocampal EEG reflects the intensity of motor behaviour in a non-specific but predictable way. However, some experimental results indicate that sensory inputs may modulate the hippocampal EEG as well.
Animals↗
Hippocampal EEG and behaviour in dog. III. Hippocampal EEG correlates of stimulus-response tasks and of sexual behaviour.
A dog was trained to perform a spatial sound discrimination. The hippocampal EEG correlates and the movement correlates of correct trials were compared with those of incorrect trials and of 'pressings in between'. Correct and wrong responses on a place learning task were compared both with respect to the hippocampal EEG correlates and to the motor behaviour. Where significant differences in EEG correlates were found, the motor behaviour differed significantly as well. The same was found for 2 behavioral states with different motor behavioural qualities which occurred during copulation. The data support the hypothesis that the spectral properties of the hippocampal EEG reflect in a predictable but non-specific way the intensity of motor behaviour. They question the postulated correlations between hippocampal EEG and 'internal processes', on the ground that unambiguous experimental verification of such hypothesis appears to be very difficult.
Animals↗
Physiology of the hippocampus and related structures.
Explore the source record for details and available documents.
Afferent Pathways↗
Computer assisted determination of brain-behaviour correlates.
A computer method allowing determination of correlations between EEG signals and behaviour and the statistical assessment of their validity is described. The basic features of this method are: (1) Determination of averages of EEG spectral parameters and behavioural parameters within a set of time periods. Statistical assessment of the degree to which these averages differ. (2) Event related averages of EEG- or behavioural parameters in real time. Statistical assessment of the significance of the fluctuations in these averages. By way of illustration some examples of correlations between hippocampal EEG and behaviour are given.
Animals↗
[Hippocampal EEG in dog, cat and man (author's transl)].
A comparative neurophysiological study of the reactivity of hippocampal EEG in dog, cat and human (an epileptic patient with chronically indwelling electrodes) was carried out. In all 3 species the same type of qualitative changes in hippocampal spectral parameters in the theta frequency band (peak frequency, peak amplitude and rhythmicity) in relation to behavioural tasks was encountered. These results were obtained by means of computing triggered averages of spectral parameters in relation to behavioural events. Both in dog and in cat it was found that transitions in behaviour from a low intensity (e.g. sitting) to a high intensity (e.g. walking) motor activity were accompanied by an increase in the value of the afore mentioned spectral parameters. In man a similar relation between such a transition in gross motor behaviour and hippocampal EEG was, however, not observed. The highest frequencies in the theta band appeared in man to be related to "verbal behaviour and writing". In all 3 species the following generalization appeared to hold; when the same behavioural state occurs at different levels of intensity, a higher intensity of the behaviour--as measured in terms of its motor components--is related to higher values for the spectral parameters of the hippocampal EEG.
Animals↗