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1.
Temporal correlation of neuronal activity has been suggested as a criterion for multiple object recognition. In this work,
a two-dimensional network of simplified Wilson-Cowan oscillators is used to manage the binding and segmentation problem of
a visual scene according to the connectedness Gestalt criterion. Binding is achieved via original coupling terms that link
excitatory units to both excitatory and inhibitory units of adjacent neurons. These local coupling terms are time independent,
i.e., they do not require Hebbian learning during the simulations. Segmentation is realized by a two-layer processing of the
visual image. The first layer extracts all object contours from the image by means of “retinal cells” with an “on-center”
receptive field. Information on contour is used to selectively inhibit Wilson-Cowan oscillators in the second layer, thus
realizing a strong separation among neurons in different objects. Accidental synchronism between oscillations in different
objects is prevented with the use of a global inhibitor, i.e., a global neuron that computes the overall activity in the Wilson-Cowan
network and sends back an inhibitory signal.
Simulations performed in a 50×50 neural grid with 21 different visual scenes (containing up to eight objects + background)
with random initial conditions demonstrate that the network can correctly segment objects in almost 100% of cases using a
single set of parameters, i.e., without the need to adjust parameters from one visual scene to the next. The network is robust
with reference to dynamical noise superimposed on oscillatory neurons. Moreover, the network can segment both black objects
on white background and vice versa and is able to deal with the problem of “fragmentation.”
The main limitation of the network is its sensitivity to static noise superimposed on the objects. Overcoming this problem
requires implementation of more robust mechanisms for contour enhancement in the first layer in agreement with mechanisms
actually realized in the visual cortex.
Received: 25 October 2001 / Accepted: 26 February 2003 /
Published online: 20 May 2003
Correspondence to: Mauro Ursino (e-mail: mursino@deis.unibo.it, Tel.: +39-051-2093008, Fax: +39-051-2093073) 相似文献
2.
Plants only interact with neighbors over restricted distances, so local conditions are of great significance for plants. It
is therefore important to consider spatial structure and neighborhood effects if we are to understand plants' strategies.
We constructed a spatially-explicit, game theory model to explore optimal height growth at the individual-level. In the model,
there is no ESS for height growth at the population level, because there is an “instantaneous” optimal height growth strategy
for the individual plant that changes depending on the local light environment. The optimal strategy is plasticity in response
to local conditions. Game-theoretic models for plant phenotypic traits should move from “mean-field approximations” towards
explicit modeling of local interactions. 相似文献
3.
4.
Animat navigation using a cognitive graph 总被引:7,自引:0,他引:7
This article describes a computational model of the hippocampus that makes it possible for a simulated rat to navigate in
a continuous environment containing obstacles. This model views the hippocampus as a “cognitive graph”, that is, a hetero-associative
network that learns temporal sequences of visited places and stores a topological representation of the environment. Calling
upon place cells, head direction cells, and “goal cells”, it suggests a biologically plausible way of exploiting such a spatial
representation for navigation that does not require complicated graph-search algorithms. Moreover, it permits “latent learning”
during exploration, that is, the building of a spatial representation without the need of any reinforcement. When the rat
occasionally discovers some rewarding place it may wish to rejoin subsequently, it simply records within its cognitive graph,
through a series of goal and sub-goal cells, the direction in which to move from any given start place. Accordingly, the model
implements a simple “place-recognition-triggered response” navigation strategy. Two implementations of place cell management
are studied in parallel. The first one associates place cells with place fields that are given a priori and that are uniformly
distributed in the environment. The second one dynamically recruits place cells as exploration proceeds and adjusts the density
of such cells to the local complexity of the environment. Both implementations lead to identical results. The article ends
with a few predictions about results to be expected in experiments involving simultaneous recordings of multiple cells in
the rat hippocampus.
Received: 25 June 1999 / Accepted in revised form: 20 March 2000 相似文献
5.
Mirror neurons within a monkey's premotor area F5 fire not only when the monkey performs a certain class of actions but also
when the monkey observes another monkey (or the experimenter) perform a similar action. It has thus been argued that these
neurons are crucial for understanding of actions by others. We offer the hand-state hypothesis as a new explanation of the
evolution of this capability: the basic functionality of the F5 mirror system is to elaborate the appropriate feedback – what
we call the hand state– for opposition-space based control of manual grasping of an object. Given this functionality, the social role of the F5
mirror system in understanding the actions of others may be seen as an exaptation gained by generalizing from one's own hand
to an other's hand. In other words, mirror neurons first evolved to augment the “canonical” F5 neurons (active during self-movement
based on observation of an object) by providing visual feedback on “hand state,” relating the shape of the hand to the shape
of the object. We then introduce the MNS1 (mirror neuron system 1) model of F5 and related brain regions. The existing Fagg–Arbib–Rizzolatti–Sakata
model represents circuitry for visually guided grasping of objects, linking the anterior intraparietal area (AIP) with F5
canonical neurons. The MNS1 model extends the AIP visual pathway by also modeling pathways, directed toward F5 mirror neurons,
which match arm–hand trajectories to the affordances and location of a potential target object. We present the basic schemas
for the MNS1 model, then aggregate them into three “grand schemas”– visual analysis of hand state, reach and grasp, and the
core mirror circuit – for each of which we present a useful implementation (a non-neural visual processing system, a multijoint
3-D kinematics simulator, and a learning neural network, respectively). With this implementation we show how the mirror system
may learnto recognize actions already in the repertoire of the F5 canonical neurons. We show that the connectivity pattern of mirror
neuron circuitry can be established through training, and that the resultant network can exhibit a range of novel, physiologically
interesting behaviors during the process of action recognition. We train the system on the basis of final grasp but then observe
the whole time course of mirror neuron activity, yielding predictions for neurophysiological experiments under conditions
of spatial perturbation, altered kinematics, and ambiguous grasp execution which highlight the importance of the timingof mirror neuron activity.
Received: 6 August 2001 / Accepted in revised form: 5 February 2002 相似文献
6.
Yukio Takahata 《Primates; journal of primatology》1982,23(1):1-23
Some dyads of Japanese monkey adult males and females show remarkable spatial proximity and frequent exchanges of social behaviors.
It is suggested that some kind of “affinity” exists between them. Females obtain much unilateral benefit from “proximity effects”;
even lowranking females can dominate high-ranking females as long as they stay nearby their “affinitive” males. Males acquire
female followers in return. Mating relations and female mother-daughter relations play important roles in forming new “affinitive
relations.” Once monkeys have formed “affinitive relations,” however, they seldom mate with each other, as if they were kin-related.
Therefore, the acquisition of female followers appears inconsistent with a male's strategy for reproducing many genes in the
next generation.
This study was financed partly by the Cooperative Research Fund of the Primate Research Institute, Kyoto University. The outline
of this paper has already been published inTakahata (1980b). 相似文献
7.
It is widely accepted that people establish allocentric spatial representation after learning a map. However, it is unknown whether people can directly acquire egocentric representation after map learning. In two experiments, the participants learned a distal environment through a map and then performed the egocentric pointing tasks in that environment under three conditions: with the heading aligned with the learning perspective (baseline), after 240° rotation from the baseline (updating), and after disorientation (disorientation). Disorientation disrupted the internal consistency of pointing among objects when the participants learned the sequentially displayed map, on which only one object name was displayed at a time while the location of “self” remained on the screen all the time. However, disorientation did not affect the internal consistency of pointing among objects when the participants learned the simultaneously displayed map. These results suggest that the egocentric representation can be acquired from a sequentially presented map. 相似文献
8.
Hidden treatments in ecological experiments: re-evaluating the ecosystem function of biodiversity 总被引:68,自引:0,他引:68
Michael A. Huston 《Oecologia》1997,110(4):449-460
Interactions between biotic and abiotic processes complicate the design and interpretation of ecological experiments. Separating
causality from simple correlation requires distinguishing among experimental treatments, experimental responses, and the many
processes and properties that are correlated with either the treatments or the responses, or both. When an experimental manipulation
has multiple components, but only one of them is identified as the experimental treatment, erroneous conclusions about cause
and effect relationships are likely because the actual cause of any observed response may be ignored in the interpretation
of the experimental results. This unrecognized cause of an observed response can be considered a “hidden treatment.” Three
types of hidden treatments are potential problems in biodiversity experiments: (1) abiotic conditions, such as resource levels,
or biotic conditions, such as predation, which are intentionally or unintentionally altered in order to create differences
in species numbers for “diversity” treatments; (2) non-random selection of species with particular attributes that produce
treatment differences that exceed those due to “diversity” alone; and (3) the increased statistical probability of including
a species with a dominant negative or positive effect (e.g., dense shade, or nitrogen fixation) in randomly selected groups
of species of increasing number or “diversity.” In each of these cases, treatment responses that are actually the result of
the “hidden treatment” may be inadvertently attributed to variation in species diversity. Case studies re-evaluating three
different types of biodiversity experiments demonstrate that the increases found in such ecosystem properties as productivity,
nutrient use efficiency, and stability (all of which were attributed to higher levels of species diversity) were actually
caused by “hidden treatments” that altered plant biomass and productivity.
Received: 16 December 1996 / Accepted: 2 March 1997 相似文献
9.
E. W. Menzel Jr. 《Primates; journal of primatology》1991,32(4):497-508
Fifteen adult chimpanzees were tested on a series of tasks that differed from standard two-choice object discrimination learning
problems in one detail: a third choice was sometimes offered, and it consisted of clearly visible and readily accessible food.
Even under conditions where they would have to score 100% on the discrimination learning tasks to get as much food as they
could get by taking the “free” food, many of the chimpanzees worked on the problems. Individual differences were large and
reliable. Frequency of response to a given problem also varied according to how accurately the animals were performing and
increased markedly if the hidden food was made a few grams larger than the free food. The chimpanzees did not rely strictly
on a “bird-in-hand” strategy or necessarily always work to get the maximum amount of food with the minimum amount of energy
expenditure. Whether this is bad economics or good economics depends on the time scale on which one views adaptation. 相似文献
10.
Tommi Linnansaari Jean-Marc Roussel Richard A. Cunjak Jo H. Halleraker 《Hydrobiologia》2007,582(1):281-287
Active tracking of passive integrated transponder (PIT)-tags using portable antennae is becoming an increasingly common technique
in fish habitat studies in shallow rivers. We carried out “blind testing” to test the efficacy (% tags found) and accuracy
(distance between predicted and true tag location) of a portable antenna system (Texas Instruments) in winter conditions using
23-mm PIT-tags. Up to 90 cm reading range was achieved and signals penetrated ice, rock, wood and water. In the “blind test”
trials, a majority of the hidden tags (N = 12–30) were found indicating high tracking efficacy. PIT-tags that were oriented with their cylindrical axis parallel to
the plane of the antenna coil inductor loop resulted in a bimodal detection field that had low detection range in the centre
of the loop. The utilization of this bimodal detection field proved to be a very accurate method for identifying tag position
(mean ± SE distance from predicted to true tag location 10.9 ± 1.4 cm) and thus well suited for microhabitat and activity
studies in winter conditions. Aggregations of tags (multiple tags within 1 m2) and obstacles for the antenna maneuvering (e.g., boulders, logjams) reduced the pinpointing accuracy (mean ± SE 13.3 ± 1.8
cm), but the reduction in accuracy was statistically non-significant between the single and aggregated tags. 相似文献
11.
Zoey P. Zahorodny Duggan Heather N. Koopman Suzanne M. Budge 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2009,179(6):783-798
Fat bodies in the heads of toothed whales, which serve to transmit and receive sound, represent extraordinary examples of
physiological specialization in adipose tissues among mammals, yet we know surprisingly little about their biochemical composition.
We describe the spatial distributions and development of unusual endogenous lipids (branched-chain [“iso”] molecules and wax
esters) in the mandibular fat bodies of bottlenose dolphins (Tursiops truncatus) using an ontogenetic series (fetus to adult; n = 10). Although concentrations of iso-acids, iso-alcohols and waxes were lower in younger dolphins than in adults, the same
relative spatial arrangement was present in all age classes, implying a set “pattern” of acoustic lipid distribution that
is established very early in life. In all age classes, a small region of blubber overlying the lateral region contained unusually
high concentrations of iso-acids, exhibiting a tenfold increase over “normal” adjacent blubber. Being chemically more similar
to the acoustic fat bodies, this region may serve as an entry point for sound into the head. Developmental accumulations of
some iso-acids and iso-alcohols occurred more rapidly than others, implying that not only are the spatial distributions of
branched-chain molecules under extremely fine-scale control, but the regulatory mechanisms controlling acoustic lipid synthesis
are also highly complex. 相似文献
12.
Once people perceive what is in the hidden figure such as Dallenbach’s cow and Dalmatian, they seldom seem to come back to
the previous state when they were ignorant of the answer. This special type of learning process can be accomplished in a short
time, with the effect of learning lasting for a long time (visual one-shot learning). Although it is an intriguing cognitive
phenomenon, the lack of the control of difficulty of stimuli presented has been a problem in research. Here we propose a novel
paradigm to create new hidden figures systematically by using a morphing technique. Through gradual changes from a blurred
and binarized two-tone image to a blurred grayscale image of the original photograph including objects in a natural scene,
spontaneous one-shot learning can occur at a certain stage of morphing when a sufficient amount of information is restored
to the degraded image. A negative correlation between confidence levels and reaction times is observed, giving support to
the fluency theory of one-shot learning. The correlation between confidence ratings and correct recognition rates indicates
that participants had an accurate introspective ability (metacognition). The learning effect could be tested later by verifying
whether or not the target object was recognized quicker in the second exposure. The present method opens a way for a systematic
production of “good” hidden figures, which can be used to demystify the nature of visual one-shot learning. 相似文献
13.
Prime SL Vesia M Crawford JD 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2011,366(1564):540-553
Constructing an internal representation of the world from successive visual fixations, i.e. separated by saccadic eye movements, is known as trans-saccadic perception. Research on trans-saccadic perception (TSP) has been traditionally aimed at resolving the problems of memory capacity and visual integration across saccades. In this paper, we review this literature on TSP with a focus on research showing that egocentric measures of the saccadic eye movement can be used to integrate simple object features across saccades, and that the memory capacity for items retained across saccades, like visual working memory, is restricted to about three to four items. We also review recent transcranial magnetic stimulation experiments which suggest that the right parietal eye field and frontal eye fields play a key functional role in spatial updating of objects in TSP. We conclude by speculating on possible cortical mechanisms for governing egocentric spatial updating of multiple objects in TSP. 相似文献
14.
Masazumi Mitani 《Primates; journal of primatology》1986,27(4):397-412
Japanese monkeys often exchange the particular vocal sound, “coo,” especially when they feed or move as a group. It was considered
that the “coo” sound had no positive social meaning, perhaps because the “coo” sound network and its function were hidden
behind other behavioral observations. For identification of the vocalizer only from hearing the “coo” sound, three phonetic
values, i.e., the “fundamental,” “duration,” and “formants,” plus other characteristics were used as indices of voiceprints. The results indicated that these were effective for identifying
the vocalizer in two-thirds of the adults in the study troop which was composed of 12 adults and 16 immature members. The
“coo” sound exchange network among the troop members (adults) was drawn on the basis of the voiceprint identification. The
network showed three characteristics as follows: (1) matriarchs of the kin-groups frequently exchanged “coo” sounds with each
other; (2) the other females exchanged “coo” sounds mostly within their own kin-groups; and (3) males seldom participated
in the “coo” sound exchange. This suggests that “coo” sound exchange plays a central role for the matriarch of kin-groups
in binding each kin-group and, ultimately, in binding all members together into an organized troop. 相似文献
15.
Edna Cabecinha Paul J. Van den Brink João Alexandre Cabral Rui Cortes Martinho Lourenço Miguel Ângelo Pardal 《Hydrobiologia》2009,628(1):27-45
Phytoplankton communities are structured by factors acting over temporal and spatial scales. Identifying which factors are
driving spatial patterns in aquatic communities is the central aim of ecology. In this study, data sets of phytoplankton communities
and environmental data of two Portuguese reservoirs types (lowland “riverine reservoirs” and higher altitude “artificial lake
reservoirs”) were used to determine the importance of environmental variables at different spatial (geographical, regional
and local) and time scales (seasons, years) on the community structure. In all the data sets, the multivariate ordination
technique Canonical Correspondence Analysis (CCA) showed that regional and local scales explained the majority (9–18% and
13–19%, respectively) of the taxa variance. However, for “riverine reservoirs”, time variables were more important, explaining 27% of the variability in phytoplankton
assemblages. Variance partitioning was used to assess the individual importance of the three spatial scales and time for the
community structure of the two reservoir types. The majority of among-site variability (5.9–21.4%) was accounted for by time
variables, with local, regional, and geographical scale variables accounting for 3.3–5.6%, 3.7–4.5% and 2.6–2.9%, respectively.
The effects of different spatial scales on phytoplankton communities were clearly interrelated; thus, implying that phytoplankton
assemblages are capable of detecting stress from catchment to site scales.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Handling editor: J. Padisak 相似文献
16.
Derick A. Fay 《Human ecology: an interdisciplinary journal》2007,35(1):81-95
With the rise of joint management of protected areas, community representatives are increasingly involved in formal negotiations
with state officials, nongovernmental organizations (NGOs) and other actors. Policy recommendations have commonly idealized
“win-win” scenarios. Theoretical work on negotiation from psychology and management studies, however, points to identifiable
circumstances under which the goal of a mutually beneficial “win-win” situation may limit the strategies, and ultimately the
benefits, available to communities. Instead, an antagonistic, “distributive” approach to negotiations may be more compatible
with the pressures on and strategies available to community representatives. The tensions between a “mutual gains” and “distributive”
approach to negotiations are evident in two land claims on protected areas in South Africa: the Dwesa-Cwebe Nature Reserves,
and the Pafuri Triangle, a portion of Kruger National Park. In each, NGOs that operated with a “mutual gains” strategy, espousing
a “win-win” scenario, came to be perceived as collaborating with conservation agencies. Meanwhile, as negotiation theory would
suggest, community representatives inclined towards a “distributive” strategy and allied with a second set of explicitly advocatory
NGOs. Expecting that communities should embrace a “win-win” scenario from the outset is unrealistic and likely to reduce communities’
power in negotiations.
相似文献
Derick A. FayEmail: |
17.
A detailed analysis is presented of the main contributions, both local and international, to the fields of oceanography and
fishery sciences resulting from exploratory cruises carried out on the continental shelf off Argentina over the last 100 years.
The end of the 19th century is chosen as a starting point for this analysis as it marks the beginning of active marine research
by Argentinian scientists and an accumulation of information on Antarctic and Subantarctic organisms in foreign journals.
Mention is also made of previous contributions derived from the classic expeditions and global circumnavigational voyages
during the 18th and 19th centuries. Although the aims of those were not always strictly oceanographic, they rendered significant
information to this field of knowledge. In the early years, references arose mainly from the particular geographic situation
of the Argentinian shelf, a necessary passage in the navigation routes to the Pacific Ocean, and later on the way to Antarctica.
Sources of information are divided into four categories: (a) foreign scientific projects in the area; (b) investigation by
Argentinian scientists and research vessels; (c) joint projects between Argentinian and foreign institutions; and (d) contributions
from sources other than oceanographic cruises (commercial navigation, maritime weather reports, satellite images, etc.). The
analysis includes an updated and classified bibliographical list of the main contributions to the fields of oceanography and
fishery sciences derived from those sources, published either in international or local journals or appearing as technical
and internal reports. The motivations, objectives and main achievements of foreign surveys and programmes in the area and
their impact on local scientific progress are discussed. The early sixties mark a turning point in the evolution of international
research in the area. The creation of biological stations along the Argentinian coast, and the support given to the pooling
of human resources set the basis for the development of bilateral programmes. Similar progress in Brazil and Uruguay led to
the outgrowth of regional activities. Joint scientific efforts described in this analysis include the programmes carried out
by the research vessels of Germany (“Walther Herwig”, “Meteor”), Japan (“Kaiyo Maru”, “Orient Maru”, “Shinkai Maru”), Poland
(“Professor Siedlecki”), Russia (“Evrika”, “Dimitry Stefanov”) and the USA (“Vema”, “Atlantis II”), the achievements of which
are a landmark in the evolution of marine science in the aea. 相似文献
18.
Shuichi Matsumura 《Primates; journal of primatology》1999,40(1):23-31
Recent studies of captive macaques have revealed considerable inter-species differences in dominance styles among females.
In “egalitarian” species such as stumptail (Macaca arctoides) or tonkean macaques (M. tonkeana), social interactions are more symmetrical and less kin-biased than in “despotic” species such as Japanese (M. fuscata) or rhesus macaques (M. mulatta). Field observations of moor macaques (M. maurus), close relatives of tonkean macaques, suggest that tolerance during feeding characterizes their egalitarian dominance style
in the natural habitat. Although it has been proposed that communal defense against other groups may be the main selective
force in the evolution of egalitarian dominance style among females, few field data support this prediction. A game theory
analysis showed that both an “egalitarian” strategy and a “despotic” strategy are possible evolutionarily stable strategies
(ESS) under certain conditions. The difference in dominance styles might reflect the difference in ESS. This means that an
egalitarian dominance style can emerge without strong between-group contest competition. A phylogenetic comparison among macaques
suggests that despotic dominance styles very likely evolved from egalitarian dominance styles. In the future, primate socioecological
studies should pay more attention to the evolutionary history of each species. 相似文献
19.
The intentional introduction of exotic species can increase the level of local biodiversity, enrich people’s material lives,
and bring significant social and economic benefits that are also the symbols of human progress. However, along with the frequent
intercourse among countries and regions, the frequency of uncontrolled crossregional migration of species is increased and
there is a lack of scientific management strategy for the intentional introduction of exotic species. Exotic species invasion,
which is behind habitat fragmentation, has become the second largest threatening factor to the maintenance of the global-scale
level of biological diversity. Exotic species invasion can destroy the structure of an ecosystem, disturb the economic life
of a society, and do harm to human health. In this paper, the authors review some of the ecological explanations for issues
such as “what causes or mechanisms have led to the successful invasion of exotic species”, including the “ideal weeds characteristics”,
“biodiversity resistance hypothesis”, “enemies release hypothesis”, “evolution of increased competitive ability hypothesis”,
“niche opportunity hypothesis”, and “novel weapon hypothesis”. The authors also analyze and evaluate the background and theoretical
basis of the hypotheses, providing explanations for some phenomena, as well as the deficiencies of these explanations. 相似文献
20.
Akio Mori 《Primates; journal of primatology》1995,36(1):11-26
The feeding process of Japanese monkeys on soy beans which were scattered over a sandy beach on Koshima islet was studied.
Younger monkeys were able to pick up more beans when 8 kg of beans were divided and given two times (“two times feeding”)
than when the whole amount (8 kg) of beans was given at one time (“one time feeding”). The effect of saturation of the food
intake capacity in younger monkeys at the first feeding in “two times feeding” did not appear at the second feeding one hour
later. The minutely intake of soy beans (feeding speed) for each age class was analyzed. The decline of feeding speed in adult
females after the peak in “one time feeding” was not related to the decline in density of beans on the ground, and this decline
was caused by saturation of their food intake capacity.
Adult females were divided into four classes according to their dominance rank order: high, lower-high, higher-low, and low
classes. The total amount of intake in “one time feeding” was far larger in the high class than in any of the other classes.
The total amount of feeding in the first feeding of “two times feeding” increased in accordance with rise in the dominance
rank class, and there was no relation to rank and total feeding amount in the second feeding of “two times feeding.” Differences
existed in the process of feeding between the rank classes. The feeding speed of the low class was as high as that of the
high class on the curve of minutely intake, while the low class stopped feeding much earlier than the high class. The lower-high
class displayed a low feeding speed, and stopped feeding the latest. The order of the duration to stay and to feed in the
feeding area was lower-high > high > higher-low > low, and this order did not change under the three different feeding conditions,
“one time feeding,” and the first and second feedings of “two times feeding.” Adolescent females tended to stay the longest
duration in the feeding area among all age classes. Both the lower-high class females and adolescent females had an unstable
social status in the Koshima group, and their social status affected their feeding behaviors. The feeding behaviors were similar
in attitude depending on social status, and are considered to be maintained for a fairly long time.
The feeding strategy of the lower-high class, in staying a longer duration in the artificial feeding area, and departing later,
may be effective under the artificial feeding conditions, but it may be a bad strategy in a natural habitat where the food
is not so clumped as in artificial feeding, and where choice of other food patches is possible. The above results agree well
with previous reports for the Koshima group, indicating that the rank of the lower-high class females was unstable (Mori et al., 1989), and that their reproductive success was low (Watanabe et al., 1992). 相似文献