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At least 415 records · Page 23Linked to original sources
PubMed2006

Tactile guidance of prey capture in Etruscan shrews.

Whereas visuomotor behaviors and visual object recognition have been studied in detail, we know relatively little about tactile object representations. We investigate a new model system for the tactile guidance of behavior, namely prey (cricket) capture by one of the smallest mammals, the Etruscan shrew, Suncus etruscus. Because of their high metabolic rate and nocturnal lifestyle, Etruscan shrews are forced to detect, overwhelm, and kill prey in large numbers in darkness. Crickets are exquisitely mechanosensitive, fast-moving prey, almost as big as the shrew itself. Shrews succeed in hunting by lateralized, precise, and fast attacks. Removal experiments demonstrate that both macrovibrissae and microvibrissae are required for prey capture, with the macrovibrissae being involved in attack targeting. Experiments with artificial prey replica show that tactile shape cues are both necessary and sufficient for evoking attacks. Prey representations are motion- and size-invariant. Shrews distinguish and memorize prey features. Corrective maneuvers and cricket shape manipulation experiments indicate that shrew behavior is guided by Gestalt-like prey descriptions. Thus, tactile object recognition in Etruscan shrews shares characteristics of human visual object recognition, but it proceeds faster and occurs in a 20,000-times-smaller brain.

Animals↗
PubMed1997

Female space use is the best predictor of monogamy in mammals.

Monogamy is typically considered to have evolved either because biparental care is important for offspring survival, or because males are unable to monopolize more than one female due to females being too dispersed. Here, in the first phylogenetic analysis of the evolution of monogamy in mammals, we show that neither of these explanations is consistent with the distribution of monogamy across mammal species. Monogamy evolved significantly more often in the absence of paternal care than in its presence. Furthermore, monogamy does not normally occur in species where female ranges are large. Rather, the most common feature of mammalian monogamy is that it evolved where females were solitary and occupied small, exclusive ranges, enabling males to monopolize them.

Animals↗
PubMed2006

Experimentally increased food resources in the natal territory promote offspring philopatry and helping in cooperatively breeding carrion crows.

Kin-based societies, where families represent the basic social unit, occur in a relatively small number of vertebrate species. In the majority of avian kin societies, families form when offspring prolong their association with the parents on the natal territory. Therefore, the key to understanding the evolution of families in birds is to understand natal philopatry (i.e. the tendency to remain on the natal territory). It has been shown that, within populations, the strength of the association between parents and offspring (i.e. family stability) increases when offspring dispersal is constrained by external environmental factors, but it is unclear whether and how family wealth influences juvenile dispersal decisions. Here, we show that young carrion crows (Corvus corone corone) from territories that were food-supplemented year-round were more philopatric and more likely to help at their family's nest than the unfed ones. The results suggest that offspring philopatry and helping behaviour are influenced by the quality of 'home' and that the availability of food resources positively affects the cohesion of the family.

Animal Migration↗
PubMed2005

Mating system, philopatry and patterns of kinship in the cooperatively breeding subdesert mesite Monias benschi.

In the first molecular study of a member of the threatened avian family, Mesitornithidae, we used nine polymorphic microsatellite loci to elucidate parentage, patterns of within-group kinship and occurrence of extra-group paternity in the subdesert mesite Monias benschi, of southwest Madagascar. We found this cooperatively breeding species to have a very fluid mating system. There was evidence of genetic monogamy and polygynandry: of the nine groups with multiple offspring, six contained one breeding pair with unrelated helpers and three contained multiple male and female breeders with related helpers. Although patterns of within-group kinship varied, there was a strong positive relationship between group size and relatedness, suggesting that groups form by natal philopatry. There was also a strong positive correlation between within-sex and between-sex relatedness, indicating that unlike most cooperatively breeding birds, philopatry involved both sexes. In contrast to predictions of kin selection and reproductive skew models, all monogamous groups contained unrelated individuals, while two of the three polygynandrous groups were families. Moreover, although between-group variation in seasonal reproductive success was related to within-group female relatedness, relatedness among males and between the sexes had no bearing on a group's reproductive output. While kin selection may underlie helping behaviour in females, factors such as direct long-term fitness benefits of group living probably determine helping in males. Of the 14 offspring produced by fully sampled groups, at least two were sired by males from neighbouring groups: one by a breeding male and one by a nonbreeding male, suggesting that males may augment their reproductive success through extra-group paternity.

Animals↗
PubMed2003

Do familiar landmarks reset the global path integration system of desert ants?

It is often suggested that animals may link landmark memories to a global coordinate system provided by path integration, thereby obtaining a map-like representation of familiar terrain. In an attempt to discover if desert ants form such associations we have performed experiments that test whether desert ants recall a long-term memory of a global path integration vector on arriving at a familiar food site. Ants from three nests were trained along L-shaped routes to a feeder. Each route was entirely within open-topped channels that obscured all natural landmarks. Conspicuous artificial landmarks were attached to the channelling that formed the latter part of the route. The homeward vectors of ants accustomed to the route were tested with the foodward route, either as in training, or with the first leg of the L shortened or extended. These ants were taken from the feeder to a test area and released, whereupon they performed a home vector. If travelling the latter part of a familiar route and arriving at a familiar food site triggers the recall of an accustomed home vector, then the home vector should be the same under both test conditions. We find instead that the home vector tended to reflect the immediately preceding outward journey. In conjunction with earlier work, these experiments led us to conclude in the case of desert ants that landmark memories do not prime the recall of long-term global path integration memories. On the other hand, landmark memories are known to be linked to local path integration vectors that guide ants along a segment of a route. Landmarks thus seem to provide procedural information telling ants what action to perform next but not the positional information that gives an ant its location relative to its nest.

Animals↗
PubMed2002

How the viewing of familiar landscapes prior to release allows pigeons to home faster: evidence from GPS tracking.

Providing homing pigeons with a 5 min preview of the landscape at familiar sites prior to release reliably improves the birds' subsequent homing speeds. This phenomenon has been taken to suggest that the visual panorama is involved in familiar-site recognition, yet the exact nature of the improvement has never been elucidated. We employed newly developed miniature Global Positioning System (GPS) tracking technology to investigate how access to visual cues prior to release affects pigeons' flight along the length of the homing route. By applying a variety of novel analytical techniques enabled by the high-resolution GPS data (track efficiency, virtual vanishing bearings, orientation threshold), we localised the preview effect to the first 1000 m of the journey. Birds denied preview of a familiar landscape for 5 min before take-off flew an initially more tortuous path, including a high incidence of circling, possibly as part of an information-gathering strategy to determine their position. Beyond the first 1000 m, no differences were found in the performance of birds with or without preview. That the effect of the visual treatment was evident only in the early part of the journey suggests that lack of access to visual cues prior to release does not result in a non-specific effect on behaviour that is maintained throughout the flight. Instead, it seems that at least some decisions regarding the direction of home can be made prior to release and that such decisions are delayed if visual access to the landscape is denied. Overall, the variety of approaches applied here clearly highlight the potential for future applications of GPS tracking technology in navigation studies.

Animals↗
PubMed1986

Effect of space allowance and tylosin feeding on performance of growing-finishing pigs. NCR-89 Committee on Confinement Management of Swine.

The relationship between space allowance and tylosin feeding of growing-finishing pigs was investigated at nine experiment stations in the North Central Region. The experiment involved 1,352 pigs in 23 replications of treatments. Pigs allowed .46 m2 from 25 to 57 kg body weight and .74 m2 from 57 to 96 kg grew faster in the grower (P less than .001), finisher (P less than .05) and grower-finisher (P less than .001) periods than did pigs allowed .32 m2 and .56 m2 for the two weight periods, respectively. Feed efficiency was improved (P less than .005) by the more liberal space allowance in the grower, but not in the finisher period. Tylosin at 44 mg/kg changed to 22 mg/kg at 57 kg body weight caused an increase (P = .07) in rate of gain for the overall grower-finisher period and an improvement in feed efficiency in the grower (P = .07) and the grower-finisher (P less than .05) periods. In no instance was there an interaction between space allowance and tylosin feeding. Station effects were significant for all performance estimates, but there were no interactions between station and space-tylosin treatments. The results of the experiment indicate that crowding depressed performance of growing-finishing pigs, that tylosin feeding slightly improved performance and that the space allowance and the tylosin growth responses were independent.

Animals↗
PubMed1996

Effects of combined block of alpha 1-adrenoceptors and NMDA receptors on spatial and passive avoidance behavior in rats.

The present study was designed to investigate the interactions between alpha 1-adrenoceptors and NMDA receptors in modulating spatial navigation and passive avoidance behavior in rats. Pretraining treatment with prazosin, and alpha 1-adrenoceptor antagonist, at 2 mg/kg i.p., impaired acquisition performance in a water maze navigation test and had no effect on passive avoidance behavior. Posttraining and pretest injections of prazosin had no effect on water maze or passive avoidance behavior. Pretraining treatment with ((+/-))-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP), a competitive NMDA receptor antagonist, does dependently (3 and 10 mg/kg) impaired passive avoidance and water maze behavior. Posttraining treatment with CPP had no effect on water maze and passive avoidance behavior. A pretraining combination of subthreshold doses of CPP (1 mg/kg) and prazosin (1 mg/kg) impaired water maze behavior. A combination of subthreshold doses of CPP (3 mg/kg) and prazosin (1 mg/kg) injected posttraining or pretest had no marked effect on water maze or passive avoidance performance. A control experiment showed that CPP 3 mg/kg or CPP 1 mg/kg and prazosin 1 mg/kg injected pretraining had no effect on cue navigation to a clearly visible platform, but CPP 10 mg/kg markedly impaired performance. The present results indicate that alpha 1-adrenoceptors and NMDA receptors may synergistically regulate acquisition of spatial navigation performance. Therefore, it would be interesting to study the effects of combined stimulation of alpha 1-adrenoceptors and NMDA receptors on age-related memory defects.

Adrenergic alpha-Antagonists↗
PubMed1996

Metrifonate improves spatial navigation and avoidance behavior in scopolamine-treated, medial septum-lesioned and aged rats.

We investigated the effects of acute p.o. pretraining treatment with an indirect acetylcholinesterase inhibitor, metrifonate, on water maze spatial navigation and passive avoidance behavior. Metrifonate (10-100 mg/kg, orally, p.o.) did not improve the water maze or passive avoidance performance of young intact rats. However, in young rats metrifonate over a broad dosage range (10-100 mg/kg, p.o.) was able to alleviate the adverse effects of scopolamine (a muscarinic acetylcholine receptor antagonist; 0.4 and 2.0 mg/kg in water maze and passive avoidance study, respectively) and medial septum-lesioning on spatial reference and working memory and passive avoidance performance. In old (23-month-old) rats, a defect of water maze and passive avoidance behavior was observed. In old rats, metrifonate improved spatial reference memory function in the water maze and also passive avoidance at 10-30 mg/kg, but the 3 mg/kg dose was ineffective. Very old (27-month-old) rats had a more severe impairment of water maze performance than old rats, and metrifonate 3-30 mg/kg did not improve their spatial navigation. These results show that metrifonate may over a wide range of doses stimulate cognitive functioning, but during advanced aging neurobiological defects develop that may mask some of the therapeutic effects of metrifonate in rats.

Aging↗
PubMed1989

Intrahippocampal grafts of fetal basal forebrain tissue alter place fields in the hippocampus of rats with fimbria-fornix lesions.

Intrahippocampal grafts of fetal basal forebrain tissue have been shown to restore several aspects of neural function, including some degree of behavioral recovery in spatial memory tasks, in rats with fimbria-fornix lesions. Place fields, the behavioral correlates of complex-spike unit activity recorded in the hippocampus of rats, are altered by fimbria-fornix lesions, and provide an important measure of the functioning circuitry of the hippocampus after grafts. To investigate the effects of grafts on hippocampal circuitry, complex-spike units were recorded while the rats traversed a radial maze. Quantitative analyses of spatial activity showed that units in normal rats had spatially clustered, reliable place fields that were stable despite alterations of the maze. In contrast, units in rats with fimbria-fornix lesions had more dispersed, less reliable place fields that were disrupted when the maze was covered or rotated. Compared to rats with fimbria-fornix lesions, rats with grafts and units with more tightly clustered, more reliable, and more stable place fields when the maze was altered. The results suggest that: (1) fimbria-fornix lesions disrupt some aspects of complex-spike place field activity; (2) the functioning of hippocampal circuitry is influenced by fetal basal forebrain grafts; and (3) the grafts may ameliorate the effects of lesions on spatial behaviors by influencing critical aspects of place field activity in the hippocampus.

Action Potentials↗
PubMed1990

Behavioral determination of the spatial selectivity of contrast adaptation in cats: some evidence for a common plan in the mammalian visual system.

An aftereffects paradigm was used to behaviorally measure contrast sensitivity of cats to gratings of three different test spatial frequencies after adaptation to gratings of various spatial frequencies, contrasts, and durations. Post-adaptation reductions in sensitivity occurred even after short periods of adaptation (less than 7 s) and could be as large as 1.0 log unit under some conditions. The magnitude of the adaptation effect varied monotonically with (1) adaptation grating contrast, (2) duration, and (3) the contrast sensitivity for the test grating. Average half-width (at half-height) of the spatial-frequency tuning curves constructed from the data was 1.4 octaves, and was not dependent upon the level of adaptation or the spatial frequency of the test grating. Post-adaptation psychometric functions of the cats showed reduced slopes and maxima suggesting that, unlike humans, in cats apparent contrast grows more slowly with increases in physical contrast after contrast adaptation. All of the characteristics observed are in excellent agreement with electrophysiologically measured properties of neurons in striate cortex of cats. In addition, there was a remarkable similarity of the cat tuning functions, both in shape and bandpass, to those measured in man with a similar paradigm suggesting that (1) the two visual systems are sufficiently similar to make the cat a useful spatial vision model and (2) there is a common functional plan to all mammalian visual systems despite significant anatomical differences between species.

Adaptation, Ocular↗
PubMed2006

Behavioral inhibition and impaired spatial learning and memory in hypothyroid mice lacking thyroid hormone receptor alpha.

Thyroid hormone insufficiency leads to impaired neurogenesis, behavioral alterations and cognitive deficits. Thyroid hormone receptors, expressed in brain regions involved in these behaviors, mediate the effects of thyroid hormone deficiency or excess. To determine the contribution of thyroid hormone receptor alpha (TRalpha) in these behaviors, we examined the behavior of euthyroid as well as hypo- and hyperthyroid mice lacking all isoforms of the TRalpha (TRalpha(o/o)). The hypothyroxinemic TRalpha(o/o) mice demonstrated behavioral inhibition, manifested in decreased activity and increased anxiety/fear in the open field test (OFT) and increased immobility in the forced swim test (FST) compared to C57BL/6J mice. TRalpha(o/o) mice also showed learning and recall impairments in the Morris water maze (MWM), which were exaggerated by hypothyroidism in TRalpha(o/o) mice. These impairments were concurrent with increased thigmotaxis, suggesting an increased anxiety-like state of the TRalpha(o/o) mice in the MWM. Expression of genes, known to be involved in processes modulating learning and memory, such as glucocorticoid receptor (GR), growth-associated protein 43 (GAP-43) and neurogranin (RC3), were significantly decreased in the hippocampus of TRalpha(o/o) mice. GR expression was also decreased in the frontal cortex and amygdala of TRalpha(o/o) mice, indicating that expression of GR is regulated, probably developmentally, by one or more isoforms of TRalpha in the mouse brain. Taken together these data demonstrate behavioral alterations in the TRalpha(o/o) mice, indicating the functional role of TRalpha, and a delicate interaction between TRalpha and TRbeta-regulated genes in these behaviors. Thyroid hormone-regulated genes potentially responsible for the learning deficit found in TRalpha(o/o) mice include GR, RC3 and GAP-43.

Analysis of Variance↗
PubMed2002

Hippocampal expression of c-fos is not essential for spatial learning.

The formation of long-term memory is thought to involve underlying changes in synaptic strength. Many studies have focused on the mechanisms of spatial learning behavior in mammals that is critically dependent on the proper function of the hippocampus. Because of the enduring nature of long-term memory, it is thought that gene expression is involved in this process. The immediate early gene (IEG) c-fos encodes a transcription factor. The c-Fos proteins form heterodimeric proteins with the c-Jun family proteins and the resulting AP-1 transcription complex plays a key role in coupling short-term events elicited by stimuli received at the cell membrane to long-term neuroplastic changes by regulating gene expression. c-fos is induced in the hippocampus after spatial learning. Despite this knowledge, the precise role of c-fos in memory formation and the underlying mechanisms remain unknown. To start investigating the role of c-fos in learning and memory and underlying mechanisms, we evaluated spatial learning capabilities using mice carrying a hippocampal region-specific mutation of c-fos. We found that the c-fos mutant mice exhibit normal spatial learning behaviors in both the Morris water maze and the Barnes maze tests compared to control mice. Our results suggest that hippocampal c-fos expression is not essential for spatial learning.

Animals↗
PubMed2006

Spatiotemporal intermittency and scaling laws in the coupled sine circle map lattice.

We study spatiotemporal intermittency (STI) in a system of coupled sine circle maps. The phase diagram of the system shows parameter regimes with STI of both the directed percolation (DP) and non-DP class. STI with synchronized laminar behavior belongs to the DP class. The regimes of non-DP behavior show spatial intermittency (SI), where the temporal behavior of both the laminar and burst regions is regular, and the distribution of laminar lengths scales as a power law. The regular temporal behavior for the bursts seen in these regimes of spatial intermittency can be periodic or quasiperiodic, but the laminar length distributions scale with the same power law, which is distinct from the DP case. STI with traveling wave laminar states also appears in the phase diagram. Solitonlike structures appear in this regime. These are responsible for crossovers with accompanying nonuniversal exponents. The soliton lifetime distributions show power-law scaling in regimes of long average soliton lifetimes, but peak at characteristic scales with a power-law tail in regimes of short average soliton lifetimes. The signatures of each type of intermittent behavior can be found in the dynamical characterizers of the system viz. the eigenvalues of the stability matrix. We discuss the implications of our results for behavior seen in other systems which exhibit spatiotemporal intermittency.

Journal Article↗
PubMed1975

Origins of anthropoid intelligence.

The development of the extrastriate visual system relative to the striate system was estimated indirectly by measuring the volumes of the lateral posteriorpulvinar complex and lateral geniculate nucleus in six varieties of mammals selected on the basis of their propinquity with Anthropoidea [oppossums, hedgehogs, rats, squirrels, tree shrews and bushbabies]. The same animals were tested on two related behavioral tasks [spatial and visual reversal learning] whose successful achievement requires a simple sort of abstraction. The results show that the ability to learn visual reversal, but not spatial reversal, corresponds closely to the relative degree of development of the extrastriate system. Since the variation in both these behavioral and morphological characteristics also parallels the phylogenetic dimension, the recency of common ancestry to anthropoids, the evolutionary origin of the anthropoid capacity for visual abstraction is suggested.

Animals↗