Identification of individual neurons reflecting short- and long-term visual memory in an arthropod

Ideally, learning-related changes should be investigated while they occur in vivo, but physical accessibility and stability limit intracellular studies. Experiments with insects and crabs demonstrate their remarkable capacity to learn and memorize visual features. However, the location and physiology of individual neurons underlying these processes is unknown. A recently developed crab preparation allows stable intracellular recordings from the optic ganglia to be performed in the intact animal during learning. In the crab Chasmagnathus, a visual danger stimulus (VDS) elicits animal escape, which declines after a few stimulus presentations. The long-lasting retention of this decrement is mediated by an association between contextual cues of the training site and the VDS, therefore, called context-signal memory (CSM). CSM is achieved only by spaced training. Massed training, on the contrary, produces a decline of the escape response that is short lasting and, because it is context independent, is called signal memory (SM). Here, we show that movement detector neurons (MDNs) from the lobula (third optic ganglion) of the crab modify their response to the VDS during visual learning. These modifications strikingly correlate with the rate of acquisition and with the duration of retention of both CSM and SM. Long-term CSM is detectable from the response of the neuron 1 d after training. In contrast to MDNs, identified neurons from the medulla (second optic ganglion) show no changes. Our results indicate that visual memory in the crab, and possibly other arthropods, including insects, is accounted for by functional changes occurring in neurons originating in the optic lobes.Fil:Tomsic, D. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Berón de Astrada, M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Sztarker, J. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Identification of individual neurons reflecting short- and long-term visual memory in an arthropod

Ideally, learning-related changes should be investigated while they occur in vivo, but physical accessibility and stability limit intracellular studies. Experiments with insects and crabs demonstrate their remarkable capacity to learn and memorize visual features. However, the location and physiology of individual neurons underlying these processes is unknown. A recently developed crab preparation allows stable intracellular recordings from the optic ganglia to be performed in the intact animal during learning. In the crab Chasmagnathus, a visual danger stimulus (VDS) elicits animal escape, which declines after a few stimulus presentations. The long-lasting retention of this decrement is mediated by an association between contextual cues of the training site and the VDS, therefore, called context-signal memory (CSM). CSM is achieved only by spaced training. Massed training, on the contrary, produces a decline of the escape response that is short lasting and, because it is context independent, is called signal memory (SM). Here, we show that movement detector neurons (MDNs) from the lobula (third optic ganglion) of the crab modify their response to the VDS during visual learning. These modifications strikingly correlate with the rate of acquisition and with the duration of retention of both CSM and SM. Long-term CSM is detectable from the response of the neuron 1 d after training. In contrast to MDNs, identified neurons from the medulla (second optic ganglion) show no changes. Our results indicate that visual memory in the crab, and possibly other arthropods, including insects, is accounted for by functional changes occurring in neurons originating in the optic lobes.Fil:Tomsic, D. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Berón de Astrada, M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Sztarker, J. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Central nervous system of the crab Neohelice granulata: A neuroanatomical description

We present a study of the CNS of Neohelice granulata performed at both the neuronal cluster and the neuropil level, describing eyestalk ganglia, the thoracic ganglion, and the central brain, with special focus on the latter. This characterization is based on the functional study of the crab´s nervous system during two main phases: visual information processing, and storage of memory. The nervous system delineation uses classical histological techniques as well as immunohistochemistry to characterize cellular clusters and neuropils. This is the first general description of N. granulata nervous system as a whole, at neuropil and cellular level. Few representations of the central nervous system of N. granulata have been published besides the general scheme published by Bond-Buckup et al. (1991).Fil: Freudenthal, Ramiro A. M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Pedreira, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Berón de Astrada, Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Sztarker, Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Delorenzi, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Frenkel, Lia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Maza, Francisco Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Carbo Tano, Martín. Centre de Recherche de I'Institut du Cerveau et de la Moelle Epinière; FranciaFil: Hepp, Yanil. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; Argentin

Neuroanatomical distribution of angiotensin-II-like neuropeptide within the central nervous system of the crab Chasmagnathus; physiological changes triggered by water deprivation

The angiotensins constitute a neuropeptidergic system that emerged early in evolution. Their classical osmoregulatory and dipsogenic functions and their mnemonic actions have been demonstrated both in vertebrates and in some invertebrates. Previously, we have shown that, in the euryhaline and semiterrestrial crab Chasmagnathus granulatus, water deprivation correlates with an increased level of brain angiotensin-II-like neuropeptide/s (ANGII-like) and improves memory processes through ANGII receptors. We have proposed that the release of brain angiotensins in response to water shortages is an ancient mechanism for coordinating various functions that, together, enable organisms to tolerate this environmental change. Here, we have evaluated the physiological changes in ANGII-like levels in diverse structures of the central nervous system of these animals during water deprivation. The neuroanatomical distribution of ANGII-like is described in the optic lobes and brain of Chasmagnathus granulatus and the physiological changes in ANGII-like distribution in various brain neuropils is evaluated after water deprivation. Our results indicate that ANGII-like is widely distributed, especially in the medial protocerebrum. After 2 h of water deprivation, ANGII-like immunoreactivity increases in the central body and decreases in the olfactory neuropil and, after 6 h of water deprivation, is markedly reduced in several brain areas. Although further experiments are needed to establish that the angiotensinergic system is involved in the balance of body fluids in this crab, our results suggest that ANGII regulates several functions during water shortages.Facultad de Ciencias Veterinaria