No description available.

The optic tectum of the leopard frog has long been known to process visual information about prey and looming threats, stimuli characterized by their movement in the visual field. However, atectal frogs can still respond to the stationary visual environment, which therefore constitutes a separate visual subsystem in the frog. The present work seeks to characterize the stationary visual environment module in the leopard frog, beginning with the hypothesis that this module is located in the anterior thalamus, among two retinorecipient neuropil regions known as neuropil of Bellonci (NB) and corpus geniculatum (CG). First, the puzzle of how a stationary frog can see the stationary environment, in the absence of the eye movements necessary for persistence of vision, is resolved, as we show that whole-head movements caused by the frog's respiratory cycles keep the retinal image in motion. Next, the stationary visual environment system is evaluated along behavioral, anatomic, and physiological lines, and connections to other brain areas are elucidated. When the anterior thalamic visual center is disconnected, frogs show behavioral impairments in visually navigating the stationary world. Under electrophysiological probing, neurons in the NB/CG region show response properties consistent with their proposed role in processing information about the stationary visual environment: they respond to light/dark and color information, as well as reverse-engineered "stationary" stimuli (reproducing the movement on the retina of the visual backdrop caused by the frog's breathing movements), and they do not habituate. We show that there is no visuotopic map in the anterior thalamus but rather a nasal-ward constriction in the receptive fields of progressively more caudal cell groups in the NB/CG region. Furthermore, each side of the anterior thalamic visual region receives information from only the contralateral half of the visual field, as defined by the visual midline, resulting from a pattern of partial crossing over of optic nerve fibers that is also seen in the mammalian thalamic visual system, a commonality with unknown evolutionary implications. We show that the anterior thalamic visual region shares reciprocal connections with the same area on the opposite side of the brain, as well as with the posterior thalamus on both sides; there is also an anterograde ipsilateral projection from the NB/CG toward the medulla and presumably pre-motor areas. / Biology

No description available.

Durante a evolução, alguns animais desenvolveram toxinas que são capazes tanto de paralisar quanto de matar suas presas, através de ação seletiva sobre receptores ou canais iônicos. As acilpoliaminas, por exemplo, são componentes não-proteicos antagonistas dos receptores glutamatérgicos acoplados a canais iönicos, que mostraram-se anticonvulsivantes em diversos modelos animais. Apesar do estudo das alterações comportamentais em animais após a injeção de substâncias químicas (etofarmacologia) ter auxiliado a estudar o mecanismo de ação destas substâncias no SNC, não há relatos sobre os efeitos comportamentais da injeção i.c.v. e i.v. da peçonha da aranha Parawixia bistriata. Descobriu-se recentemente na peçonha bruta da aranha Parawixa bistriata uma ação potencialmente anticonvulsivante in vitro: ela potencia a neurotransmissão gabaérgica e desloca receptores glutamatérgicos de seus sítios específicos em sinaptosomas do cérebro de rato (FONTANA, 1997). O objetivo do presente trabalho é estudar as alterações comportamentais causadas pela injeção central e periférica da peçonha bruta de P. bistriata através de uma metodologia quantificativa (método neuroetológico), e verificar se esta peçonha possui ação anticonvulsivante in vivo em um modelo químico de indução de crises agudas - o pentilenotetrazol (PTZ, 80 mg/kg, i.p.). Os resultados mostram que a injeção i.c.v. da peçonha bruta origina nos ratos dois quadros comportamentais, identificados como crises convulsivas, denominados de crises graves e leves. Nas crises graves, observou-se, entre outros, mioclonias semelhantes às crises convulsivas límbicas descritas por Racine (1972). As crises leves são caracterizadas por tremores generalizados, e sacudidelas de corpo (wet dog shakes). A injeção da peçonha i.v. não origina crises nos animais mas, no entanto, causa um intenso aumento nas interações estatísticas das seqüências comportamentais, que lembram em muito as atividades de deslocamento. Tanto nas crises graves, leves, e na injeção i.v., a neuroetologia permitiu a visualização das interações entre as mioclonias convulsivas límbicas e os outros comportamentos, dados não fornecidos pelas escalas de medição de intensidade das crises límbicas. Buscando indícios da presença de componentes anticonvulsivantes não-proteicos (como acilpoliaminas), injetou-se i.c.v. a peçonha de P. bistriata fervida (numa dose que não causa crises nem alteração motora per se), seguida da injeção i.p. de PTZ. Verificou-se que este tratamento abole as crises clônicas e tônicas induzidas por PTZ. Conclui-se que a peçonha bruta de P. bistriata provavelmente possui componentes pró-convulsivantes com possível ação sobre o sistema límbico. Esta peçonha pode conter, também, componentes anticonvulsivantes não-proteicos, possivelmente acilpoliaminas. / Spider venoms have hight affinity and specificity for neuronal receptors, transporters and ion channels, therefore been important tools to characterize mammal and insect nervous system. However, behavioural alterations in mammals caused by injections of spider venoms have not been studied in detail. In this work we describe the rat behavioural alteration caused by central injection of the crude venom of the spider Parawixia bistriata, using a neuroethological methodology. There were seen two types of seizures, named mild and severe. Neuroethological flowcharts showed that in mild seizures, there was a strong statistical correlation (c2) between tremor followed by laying or by laying left, which indicates that the venom, perhaps, is difficulting central coordination of movements. In severe seizures, this effect is enworsed, with the animal falling.This type of seizure are similar to those described by Racine (1972). Since the crude venom of P. bistriata showed a potencial anticonvulsant activity in vitro, we tested if it would indeed inhibit clonic and tonic convulsions induced by pentilenetetrazole (PTZ; 80 mg/kg, i.p.). Boiled crude venom of P. bistriata was i.c.v. injected, and 20 minutes later, animals (n=10) received PTZ. A control group (n=10) received only PTZ. The results were: central injection of the venom abolished clonic and tonic convulsions induced by PTZ, in 60% of the animals. In conclusion, the crude spider venom of P. bistriata, centrally injected, causes central loss of movement coordination, and elicits limbic seizures similar to those described by Racine (1972), but, when boiled and injected in lower doses, it blocks clonic and tonic convulsions induced by PTZ (80 mg/kg).

Weakly electric fish produce and detect electric fields and use their electrosensory modality in a number of behaviours including navigation and communication. They can modulate their electric discharge in frequency and amplitude to produce electrocommunication signals in variable patterns during social interactions. In one model neuroethological species, Apteronotus leptorhynchus, the most commonly produced communication signal is the ‘small chirp’ – a brief 10-30ms modulation. Individuals tend to produce these signals at high rates during agonistic interactions. In this thesis I will explore the social value of chirps, and to a lesser extent other communication behaviours, in A. leptorhynchus using a variety of experimental designs involving different staged social contexts. I use time series analysis methods to explore the patterns of chirps produced and accompanying aggressive behaviours. I first characterize electrocommunication and chirping in pairs of free swimming fish and correlate signal production with aggressive displays. Bursts of echoed, or reciprocated, chirps tend to be produced in the intervals separating aggressive attacks. Behavioural analysis shows that fish respond to conspecific chirps with echoed chirps and decreased aggression in social contexts outside the range in which previous modelling and electrophysiological data predicted that chirps could be encoded effectively. I then characterize the chirping and aggressive responses to playbacks simulating intruders with different chirping styles to test whether alternative chirp patterns differentially influence conspecific behaviour. In response to simulated intruders producing chirps that echo the real fish’s chirps with a short latency, less aggressive fish tend to produce more of their chirps in bursts than more aggressive fish. For randomly chirping intruders, the response of fish depends on the rate of chirps delivered. Fish respond less aggressively, with fewer chirps, and echo the stimulus chirps at a higher rate when high rates of random chirps are delivered than when responding to simulated intruders with low rates of randomly delivered chirps. Further, across all playback scenarios, fish that produce chirps in response to the playbacks are more aggressive than those that do not chirp. Finally, to better understand the electrosensory inputs during these interactions, I characterize changes in the electric image received by a restrained fish during movements of a free-swimming conspecific and correlate these with chirp production. When one fish is restrained, bursts of chirps tend to be associated with approach behaviours. Communication signals often function to promote individual assessment of potential rivals during agonistic encounters and bursty, antiphonal chirp exchanges may facilitate these assessments and deter potentially costly physical escalations.

Weakly electric fish produce and detect electric fields and use their electrosensory modality in a number of behaviours including navigation and communication. They can modulate their electric discharge in frequency and amplitude to produce electrocommunication signals in variable patterns during social interactions. In one model neuroethological species, Apteronotus leptorhynchus, the most commonly produced communication signal is the ‘small chirp’ – a brief 10-30ms modulation. Individuals tend to produce these signals at high rates during agonistic interactions. In this thesis I will explore the social value of chirps, and to a lesser extent other communication behaviours, in A. leptorhynchus using a variety of experimental designs involving different staged social contexts. I use time series analysis methods to explore the patterns of chirps produced and accompanying aggressive behaviours. I first characterize electrocommunication and chirping in pairs of free swimming fish and correlate signal production with aggressive displays. Bursts of echoed, or reciprocated, chirps tend to be produced in the intervals separating aggressive attacks. Behavioural analysis shows that fish respond to conspecific chirps with echoed chirps and decreased aggression in social contexts outside the range in which previous modelling and electrophysiological data predicted that chirps could be encoded effectively. I then characterize the chirping and aggressive responses to playbacks simulating intruders with different chirping styles to test whether alternative chirp patterns differentially influence conspecific behaviour. In response to simulated intruders producing chirps that echo the real fish’s chirps with a short latency, less aggressive fish tend to produce more of their chirps in bursts than more aggressive fish. For randomly chirping intruders, the response of fish depends on the rate of chirps delivered. Fish respond less aggressively, with fewer chirps, and echo the stimulus chirps at a higher rate when high rates of random chirps are delivered than when responding to simulated intruders with low rates of randomly delivered chirps. Further, across all playback scenarios, fish that produce chirps in response to the playbacks are more aggressive than those that do not chirp. Finally, to better understand the electrosensory inputs during these interactions, I characterize changes in the electric image received by a restrained fish during movements of a free-swimming conspecific and correlate these with chirp production. When one fish is restrained, bursts of chirps tend to be associated with approach behaviours. Communication signals often function to promote individual assessment of potential rivals during agonistic encounters and bursty, antiphonal chirp exchanges may facilitate these assessments and deter potentially costly physical escalations.

Many insects have auditory systems capable of detecting the ultrasonic calls of insectivorous bats and use these cues to evade capture. I tested the hypothesis that bats can decrease the conspicuousness of their echolocation calls by varying three call features: duration, repetition rate and ramp times. This was done by examining the AN2 command interneuron’s response to these features in the cricket, Teleogryllus oceanicus, after describing the firing pattern necessary for evasive behaviour. Past studies on duration and repetition rate suggest increased thresholds for short durations and low repetition rates. Measurements of the AN2 response, which controls evasive behaviour, indicated that increased thresholds were a result of a decrease in bursting, raw spike numbers and an increase in latencies in the AN2. Results suggest that there is pressure on bats to evade early detection and that this can be done by employing large ramp times in search phase echolocation calls.

Many insects have auditory systems capable of detecting the ultrasonic calls of insectivorous bats and use these cues to evade capture. I tested the hypothesis that bats can decrease the conspicuousness of their echolocation calls by varying three call features: duration, repetition rate and ramp times. This was done by examining the AN2 command interneuron’s response to these features in the cricket, Teleogryllus oceanicus, after describing the firing pattern necessary for evasive behaviour. Past studies on duration and repetition rate suggest increased thresholds for short durations and low repetition rates. Measurements of the AN2 response, which controls evasive behaviour, indicated that increased thresholds were a result of a decrease in bursting, raw spike numbers and an increase in latencies in the AN2. Results suggest that there is pressure on bats to evade early detection and that this can be done by employing large ramp times in search phase echolocation calls.

Weakly electric fish produce and detect electric fields and use their electrosensory modality in a number of behaviours including navigation and communication. They can modulate their electric discharge in frequency and amplitude to produce electrocommunication signals in variable patterns during social interactions. In one model neuroethological species, Apteronotus leptorhynchus, the most commonly produced communication signal is the ‘small chirp’ – a brief 10-30ms modulation. Individuals tend to produce these signals at high rates during agonistic interactions. In this thesis I will explore the social value of chirps, and to a lesser extent other communication behaviours, in A. leptorhynchus using a variety of experimental designs involving different staged social contexts. I use time series analysis methods to explore the patterns of chirps produced and accompanying aggressive behaviours. I first characterize electrocommunication and chirping in pairs of free swimming fish and correlate signal production with aggressive displays. Bursts of echoed, or reciprocated, chirps tend to be produced in the intervals separating aggressive attacks. Behavioural analysis shows that fish respond to conspecific chirps with echoed chirps and decreased aggression in social contexts outside the range in which previous modelling and electrophysiological data predicted that chirps could be encoded effectively. I then characterize the chirping and aggressive responses to playbacks simulating intruders with different chirping styles to test whether alternative chirp patterns differentially influence conspecific behaviour. In response to simulated intruders producing chirps that echo the real fish’s chirps with a short latency, less aggressive fish tend to produce more of their chirps in bursts than more aggressive fish. For randomly chirping intruders, the response of fish depends on the rate of chirps delivered. Fish respond less aggressively, with fewer chirps, and echo the stimulus chirps at a higher rate when high rates of random chirps are delivered than when responding to simulated intruders with low rates of randomly delivered chirps. Further, across all playback scenarios, fish that produce chirps in response to the playbacks are more aggressive than those that do not chirp. Finally, to better understand the electrosensory inputs during these interactions, I characterize changes in the electric image received by a restrained fish during movements of a free-swimming conspecific and correlate these with chirp production. When one fish is restrained, bursts of chirps tend to be associated with approach behaviours. Communication signals often function to promote individual assessment of potential rivals during agonistic encounters and bursty, antiphonal chirp exchanges may facilitate these assessments and deter potentially costly physical escalations.

Durante a evolução, alguns animais desenvolveram toxinas que são capazes tanto de paralisar quanto de matar suas presas, através de ação seletiva sobre receptores ou canais iônicos. As acilpoliaminas, por exemplo, são componentes não-proteicos antagonistas dos receptores glutamatérgicos acoplados a canais iönicos, que mostraram-se anticonvulsivantes em diversos modelos animais. Apesar do estudo das alterações comportamentais em animais após a injeção de substâncias químicas (etofarmacologia) ter auxiliado a estudar o mecanismo de ação destas substâncias no SNC, não há relatos sobre os efeitos comportamentais da injeção i.c.v. e i.v. da peçonha da aranha Parawixia bistriata. Descobriu-se recentemente na peçonha bruta da aranha Parawixa bistriata uma ação potencialmente anticonvulsivante in vitro: ela potencia a neurotransmissão gabaérgica e desloca receptores glutamatérgicos de seus sítios específicos em sinaptosomas do cérebro de rato (FONTANA, 1997). O objetivo do presente trabalho é estudar as alterações comportamentais causadas pela injeção central e periférica da peçonha bruta de P. bistriata através de uma metodologia quantificativa (método neuroetológico), e verificar se esta peçonha possui ação anticonvulsivante in vivo em um modelo químico de indução de crises agudas - o pentilenotetrazol (PTZ, 80 mg/kg, i.p.). Os resultados mostram que a injeção i.c.v. da peçonha bruta origina nos ratos dois quadros comportamentais, identificados como crises convulsivas, denominados de crises graves e leves. Nas crises graves, observou-se, entre outros, mioclonias semelhantes às crises convulsivas límbicas descritas por Racine (1972). As crises leves são caracterizadas por tremores generalizados, e sacudidelas de corpo (wet dog shakes). A injeção da peçonha i.v. não origina crises nos animais mas, no entanto, causa um intenso aumento nas interações estatísticas das seqüências comportamentais, que lembram em muito as atividades de deslocamento. Tanto nas crises graves, leves, e na injeção i.v., a neuroetologia permitiu a visualização das interações entre as mioclonias convulsivas límbicas e os outros comportamentos, dados não fornecidos pelas escalas de medição de intensidade das crises límbicas. Buscando indícios da presença de componentes anticonvulsivantes não-proteicos (como acilpoliaminas), injetou-se i.c.v. a peçonha de P. bistriata fervida (numa dose que não causa crises nem alteração motora per se), seguida da injeção i.p. de PTZ. Verificou-se que este tratamento abole as crises clônicas e tônicas induzidas por PTZ. Conclui-se que a peçonha bruta de P. bistriata provavelmente possui componentes pró-convulsivantes com possível ação sobre o sistema límbico. Esta peçonha pode conter, também, componentes anticonvulsivantes não-proteicos, possivelmente acilpoliaminas. / Spider venoms have hight affinity and specificity for neuronal receptors, transporters and ion channels, therefore been important tools to characterize mammal and insect nervous system. However, behavioural alterations in mammals caused by injections of spider venoms have not been studied in detail. In this work we describe the rat behavioural alteration caused by central injection of the crude venom of the spider Parawixia bistriata, using a neuroethological methodology. There were seen two types of seizures, named mild and severe. Neuroethological flowcharts showed that in mild seizures, there was a strong statistical correlation (c2) between tremor followed by laying or by laying left, which indicates that the venom, perhaps, is difficulting central coordination of movements. In severe seizures, this effect is enworsed, with the animal falling.This type of seizure are similar to those described by Racine (1972). Since the crude venom of P. bistriata showed a potencial anticonvulsant activity in vitro, we tested if it would indeed inhibit clonic and tonic convulsions induced by pentilenetetrazole (PTZ; 80 mg/kg, i.p.). Boiled crude venom of P. bistriata was i.c.v. injected, and 20 minutes later, animals (n=10) received PTZ. A control group (n=10) received only PTZ. The results were: central injection of the venom abolished clonic and tonic convulsions induced by PTZ, in 60% of the animals. In conclusion, the crude spider venom of P. bistriata, centrally injected, causes central loss of movement coordination, and elicits limbic seizures similar to those described by Racine (1972), but, when boiled and injected in lower doses, it blocks clonic and tonic convulsions induced by PTZ (80 mg/kg).