PubMed Health⌕ Search

Biomedical subjects

J Serrier

Publications and source records attributed to J Serrier.

11 recordsLinked to original sources
PubMed1996

Projection neurons of the mormyrid electrosensory lateral line lobe: morphology, immunohistochemistry, and synaptology.

This paper describes the morphological, immunohistochemical, and synaptic properties of projection neurons in the highly laminated medial and dorsolateral zones of the mormyrid electrosensory lateral line lobe (ELL). These structures are involved in active electrolocation, i.e., the detection and localization of objects in the nearby environment of the fish on the basis of changes in the reafferent electrosensory signal generated by the animal's own electric organ discharge. Electrosensory, corollary electromotor command-associated signals (corollary discharges), and a variety of other inputs are integrated within the ELL microcircuit. The organization of ELL projection neurons is analyzed at the light and electron microscopic levels based on Golgi impregnations, intracellular labeling, neuroanatomical tracer techniques, and gamma-aminobutyric acid (GABA), gamma-aminobutyric acid decarboxylase (GAD), and glutamate immunohistochemistry. Two main types of ELL projection neurons have been distinguished in mormyrids: large ganglionic (LG) and large fusiform (LF) cells. LG cells have a multipolar cell body (average diameter 13 microns) in the ganglionic layer, whereas LF cells have a fusiform cell body (on average, about 10 x 20 microns) in the granular layer. Apart from the location and shape of their soma, the morphological properties of these cell types are largely similar. They are glutamaterigic and project to the midbrain torus semicircularis, where their axon terminals make axodendritic synaptic contacts in the lateral nucleus. They have 6-12 apical dendrites in the molecular layer, with about 10,000 spines contacted by GABA-negative terminals and about 3,000 GABA-positive contacts on the smooth dendritic surface between the spines. Their somata and short, smooth basal dendrites, which arborize in the plexiform layer (LG cells) or in the granular layer (LF cells), are densely covered with GABA-positive, inhibitory terminals. Correlation with physiological data suggests that LG cells are I units, which are inhibited by stimulation of the center of their receptive fields, and LF cells are E units, excited by electric stimulation of the receptive field center. Comparison with the projection neurons of the ELL of gymnotiform fish, which constitute another group of active electrolocating teleosts, shows some striking differences, emphasizing the independent development of the ELL in both groups of teleosts.

Animals↗
PubMed1993

Storage of a sensory pattern by anti-Hebbian synaptic plasticity in an electric fish.

Synaptic plasticity occurs in several regions of the vertebrate brain and is believed to mediate the storage of behaviorally significant information during learning. Synaptic plasticity is well demonstrated in most cases, but the behavioral meaning of the relevant neural signals and the behavioral role of the plasticity are uncertain. In this paper we describe a case of synaptic plasticity which involves identifiable sensory and motor signals and which appears to mediate the storage of an image of past sensory input. Corollary discharge signals associated with the motor command that drives the electric organ are prominent in the electrosensory lobe of mormyrid electric fish. Some of these corollary discharge signals elicit a negative image or representation of the electrosensory input pattern that has followed recent motor commands. When the temporal and spatial pattern of sensory input changes, the corollary discharge effect also changes in a corresponding manner. The cellular mechanisms by which the corollary discharge-evoked representation is stored were investigated by intracellular recording from cells of the electrosensory lobe and pairing intracellular current pulses with the corollary discharge signal. The results indicate that the representation of recent sensory input is stored by means of anti-Hebbian plasticity at the synapses between corollary discharge-conveying fibers and cells of the electrosensory lobe. The results also suggest that dendritic spikes and plasticity at inhibitory synapses are involved in the phenomenon.

Animals↗
PubMed1992

Sensory processing and corollary discharge effects in the mormyromast regions of the mormyrid electrosensory lobe. I. Field potentials, cellular activity in associated structures.

1. This is the first of a series of papers on the electrosensory lobe and closely associated structures in electric fish of the family Mormyridae. The study describes the neuronal responses to sensory stimuli and to corollary discharge signals associated with the motor command that drives the electric organ discharge (EOD). The study is focused on the regions of the electrosensory lobe where primary afferent fibers from mormyromast electroreceptors terminate. 2. This first paper of the series describes the field potentials in the caudal lobe of the cerebellum and in the electrosensory lobe. It also describes the different types of unit activity in the caudal lobe of the cerebellum. Granule cells of the caudal lobe of the cerebellum provide the parallel fibers for most of the molecular layer of the electrosensory lobe. Determination of the input and responses of these cells is therefore an important part of the effort to understand the electrosensory lobe. 3. Corollary discharge field potentials evoked by the EOD motor command are very prominent in the caudal lobe of the cerebellum and in the electrosensory lobe. The potentials indicate that corollary discharge excitation affects first the granule cells of the caudal lobe and then, a few milliseconds later, the deeper cellular layers of the electrosensory lobe. The prominence and complexity of the field potentials indicate that corollary discharge signals have an important and varied role in the processing of electrosensory information by the mormyrid electrosensory lobe. 4. The field potentials evoked by electrosensory stimuli suggest that direct primary afferent excitation is limited to the granule and intermediate layers of the electrosensory lobe, as is indicated also by anatomic studies. 5. Proprioceptive units are the most common type of unit recorded in the granule cell region of the caudal lobe of the cerebellum (eminentia granularis posterior). These units have a regular discharge rate that changes tonically in response to slight bending of the trunk, bending of the tail, or bending of individual fins. Proprioceptive input will have a strong effect on the molecular layer of the electrosensory lobe and will thus modulate the responses of electrosensory lobe cells to electrosensory stimuli. Such proprioceptive input to the electrosensory lobe would allow the expected effects of body position changes to be accounted for in the processing of electrosensory information. 6. Units with stereotyped, short-latency corollary discharge bursts to the EOD motor command were the next most common type of unit in the eminentia granularis posterior. These corollary discharge units were not affected by sensory stimuli.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1989

Patterns of electric organ discharge activity in the weakly electric fish Brienomyrus niger L. (Mormyridae).

In this study we investigated the electric organ discharge (EOD) activity of the mormyrid fish Brienomyrus niger when they were not affected by conspecific EODs. The fish emitted two types of EOD patterns: phasic and tonic sequences of pulse intervals (SPIs). The phasic SPI occurred in the form of stereotyped, individual-specific bursts in EOD activity which we called scallop. Tonic SPIs varied in mean EOD repetition rate and pulse interval stability, and consisted of either regular activity with mean frequencies exceeding 10 Hz and a coefficient of variation (cv) below 15%, or variable activity with mean rates below 10 Hz and cv's of 15% and above. Individual fish predominantly generated one of the three patterns: "variable", "regular", or "scallop". Most fish emitted "variable" activity, but "regular" activity was typical of females and "scallop" of males. We suggest that these SPIs may facilitate individual recognition. The dynamics of the electromotor command system, as reflected by the fish's EOD activity, is compared with that of the well-studied mammalian inferior olive, and mechanisms for a possible self-regulatory central pattern generator are discussed.

Animals↗
PubMed1978

Influence of water temperature on the electric organ discharge (EOD) of the weakly electric fish Marcusenius cyprinoides (Mormyridae).

1. The influence of different water temperatures on the electric organ discharge (EOD) of a mormyrid fish Marcusenius cyprinoïdes was studied. The range of the water temperatures was fixed according to the seasonal temperature variations of the rivers in Central Africa, the natural habitat of this species. 2. The EOD activity was characterized using the following parameters: mean EOD rate, EOD pattern in the form of Interpulse Interval Histograms (IIH), IIH range, and shortest pulse interval. These parameters remained constant during control experiments at constant temperature (27 degrees C) for 4 days. 3. The mean EOD rate increases with increasing water temperatures. The lowest mean EOD rate is always found at 17 degrees C, the highest between 26 and 33 degrees C. The characteristics of the IIH are modified by stepwise temperature increases. These IIH show during high temperatures (26-33 degrees C) similar patterns to those previously observed during high level motor activity and excitement. The IIH range diminishes with stepwise temperature increases. The shortest pulse interval has a negative, linear correlation with water temperature. 4. The possible role of water temperature in the reproduction of the mormyrids is discussed. The high discharge rate of M. cyprinoïdes produced by high water temperatures during the rainy season could serve to improve the resolution of the electroreceptors during this period.

Animals↗
PubMed1976

Electric organ discharges of the weakly electric fish Gymnarchus niloticus (Mormyriformes) in its natural habitat.

Electric organ discharges (EODs) of Gymnarchus niloticus in its natural habitat (Chari River, Chad Basin) and accompanying ecological data (pH, conductivity, temperature, turbidity, O2 dissolved) were recorded. The EOD frequencies ranged from 204 to 313 Hz (day) and 196-326 Hz (night). In social swimming the range of interfish EOD frequency differences was from 4 to 82 Hz. The EOD frequency seems to decrease with the age of the fish.

Age Factors↗