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At early developmental stages, correlated neuronal activity is thought to exert a critical control on functional and structural refinement of synaptic connections. In the hippocampus, between postnatal day 2 (P2) and P6, network-driven giant depolarizing potentials (GDPs) are generated by the synergistic action of glutamate and GABA, which is depolarizing(More)
Sex steroids during the perinatal period are able to modify the postnatal development of neurons within steroid-sensitive areas in the rat brain. This study was designed to test the possible influence of the early postnatal levels of sex steroids on the morphology of the astrocytes. The experimental manipulation of the neonatal levels of sex steroids was(More)
Constraints introduced by signal carriers, pre-receptor mechanisms and receptor transduction are fundamental for shaping the signals used by the brain to build up perceptual images. This review analyses some of these constraints in the electrosensory system of pulse Gymnotids. First, it describes the characteristics and differences of electrolocation and(More)
Pulse electric fish evaluate successive electrosensory images generated by self-emitted electric discharges, creating a neural representation of the physical world. Intervals between discharges (system resolution) are controlled by a pacemaker nucleus under the influence of reafferent signals. Novel sensory stimuli cause transient accelerations of the(More)
This paper describes the peripheral mechanisms involved in signal processing of self- and conspecific-generated electric fields by the electric fish Gymnotus carapo. The distribution of the different types of tuberous electroreceptor and the occurrence of particular electric field patterns close to the body of the fish were studied. The density of tuberous(More)
Local electric fields generated by the electric organ discharge of Gymnotus carapo were explored at selected points on the skin of an emitter fish ('local self-generated fields') and on the skin of a conspecific ('local conspecific-generated fields') using a specially designed probe. Local self-generated fields showed a constant pattern along the body of(More)
Adult cycling female rats were injected with estradiol valerate (2 mg/100 g body wt.), a treatment which has previously been shown to result in synaptic remodelling in the arcuate nucleus and constant vaginal estrus. During the 32 weeks following estrogen treatment, arcuate nucleus neuronal plasma membranes were quantitatively assessed for intramembrane(More)
Understanding fixed motor pattern diversity across related species provides a window for exploring the evolution of their underlying neural mechanisms. The electric organ discharges of weakly electric fishes offer several advantages as paradigmatic models for investigating how a neural decision is transformed into a spatiotemporal pattern of action. Here,(More)
Weakly electric fishes "electrically illuminate" the environment in two forms: pulse fishes emit a succession of discrete electric discharges while wave fishes emit a continuous wave. These strategies are present in both taxonomic groups of weakly electric fishes, mormyrids and gymnotids. As a consequence one can distinguish four major types of active(More)
This article deals with the electric organ and its discharge in Gymnotus coropinae, a representative species of one of the three main clades of the genus. Three regions with bilateral symmetry are described: (1) subopercular (medial and lateral columns of complex shaped electrocytes); (2) abdominal (medial and lateral columns of cuboidal and fusiform(More)