Hemispheric specialization in dogs for processing different acoustic stimuli

Considerable experimental evidence shows that functional cerebral asymmetries are widespread in animals. Activity of the right cerebral hemisphere has been associated with responses to novel stimuli and the expression of intense emotions, such as aggression, escape behaviour and fear. The left hemisphere uses learned patterns and responds to familiar stimuli. Although such lateralization has been studied mainly for visual responses, there is evidence in primates that auditory perception is lateralized and that vocal communication depends on differential processing by the hemispheres. The aim of the present work was to investigate whether dogs use different hemispheres to process different acoustic stimuli by presenting them with playbacks of a thunderstorm and their species-typical vocalizations. The results revealed that dogs usually process their species-typical vocalizations using the left hemisphere and the thunderstorm sounds using the right hemisphere. Nevertheless, conspecific vocalizations are not always processed by the left hemisphere, since the right hemisphere is used for processing vocalizations when they elicit intense emotion, including fear. These findings suggest that the specialisation of the left hemisphere for intraspecific communication is more ancient that previously thought, and so is specialisation of the right hemisphere for intense emotions.     

Information processing specialization during interference between global and local aspects of visual hierarchical stimuli in men and women

Sex-related differences in global/local hemispheric selective processing were examined by hierarchically presented letters in conditions of their perception and comparison. Fifty-six right-handed men and 68 women (aged 17–22 years) participated in the experiment. During the interference between global and local aspects of stimuli, the mean reaction time for correct global responses was shorter than for local responses, and the right hemisphere dominated during global selective processing independently of sex. Sex-related differences in perception of visual hierarchical stimuli were more pronounced than during their comparison: men preferred the right-hemispheric global strategy of information processing, and women, the left-hemispheric local one. The dominance of the global strategy in men and local strategy in women during visual hierarchical stimuli perception, together with the absence of sex-related differences in correct responses indicates the possibility of obtaining the same efficiency of cognitive activity in different ways.     

Hemispheric specialization in domestic dogs (Canis familiaris) for processing different types of acoustic stimuli

Lateralization is considered to be a fundamental feature of vertebrate brains. The aim of the present study was to examine the impact of functional cerebral asymmetry on processing of auditory stimuli in the domestic dog (Canis familiaris) during the orientation reaction. The experiment was conducted on 46 dogs (25 females and 21 males). Four types of auditory stimuli were used in the experiment (three meaningful stimuli: cat meowing, dog barking, the "sit" command ("siad" in Polish), and a neutral word ("wir", meaning "whirl" in Polish). It was predicted that the orientation reaction (turning the head towards the stimuli) would take place only in the case of meaningful sounds. It was also expected that dogs would show consistent lateralization. As predicted, all three meaningful stimuli elicited the orientation reaction. The response of the examined dogs to cat meowing showed significant lateralization with dominant leftwards movement, which hints towards activation of the right cerebral hemisphere and may be related to strong emotions evoked by this stimulus. Contrary to results of previous studies, dogs reacting to dog barking turned their heads leftwards more often, which suggests activation of the right cerebral hemisphere, probably related to the emotional meaning of the stimulus. The "sit" command consistently evoked the orientation reaction but there was no significant lateralization of this movement.     

Philosophy and stimulus design for neuroethology of complex-sound processing.

In research on the neural mechanisms for the processing of biologically important sounds such as species-specific sounds and sounds produced by prey and predators, it is necessary to study responses of central auditory neurons to biologically important sounds, information-bearing elements (IBEs) in them, and tone bursts. The tone bursts or constant-frequency (CF) components can be an IBE in many species of animals. Information-bearing parameters characterizing these sounds must be systematically varied, and tuning of neurons to individual parameters must be studied. The measurement of a tuning curve must be performed not only for excitatory responses, but also for inhibitory and facilitative responses, if any. The selectivity of a neuron to a particular type of sound must be tested for whether it is level-tolerant. Responses to complex sounds can probably be explained on the basis of those to IBEs and tone bursts, so that the use of the tone bursts, even though they are not IBEs, is as essential as that of the biologically important sounds.     

Recurrent fractal neural networks: a strategy for the exchange of local and global information processing in the brain

The regulation of biological networks relies significantly on convergent feedback signaling loops that render a global output locally accessible. Ideally, the recurrent connectivity within these systems is self-organized by a time-dependent phase-locking mechanism. This study analyzes recurrent fractal neural networks (RFNNs), which utilize a self-similar or fractal branching structure of dendrites and downstream networks for phase-locking of reciprocal feedback loops: output from outer branch nodes of the network tree enters inner branch nodes of the dendritic tree in single neurons. This structural organization enables RFNNs to amplify re-entrant input by over-the-threshold signal summation from feedback loops with equivalent signal traveling times. The columnar organization of pyramidal neurons in the neocortical layers V and III is discussed as the structural substrate for this network architecture. RFNNs self-organize spike trains and render the entire neural network output accessible to the dendritic tree of each neuron within this network. As the result of a contraction mapping operation, the local dendritic input pattern contains a downscaled version of the network output coding structure. RFNNs perform robust, fractal data compression, thus coping with a limited number of feedback loops for signal transport in convergent neural networks. This property is discussed as a significant step toward the solution of a fundamental problem in neuroscience: how is neuronal computation in separate neurons and remote brain areas unified as an instance of experience in consciousness? RFNNs are promising candidates for engaging neural networks into a coherent activity and provide a strategy for the exchange of global and local information processing in the human brain, thereby ensuring the completeness of a transformation from neuronal computation into conscious experience.     

Early specialization for voice and emotion processing in the infant brain

Human voices play a fundamental role in social communication, and areas of the adult "social brain" show specialization for processing voices and their emotional content (superior temporal sulcus, inferior prefrontal cortex, premotor cortical regions, amygdala, and insula). However, it is unclear when this specialization develops. Functional magnetic resonance (fMRI) studies suggest that the infant temporal cortex does not differentiate speech from music or backward speech, but a prior study with functional near-infrared spectroscopy revealed preferential activation for human voices in 7-month-olds, in a more posterior location of the temporal cortex than in adults. However, the brain networks involved in processing nonspeech human vocalizations in early development are still unknown. To address this issue, in the present fMRI study, 3- to 7-month-olds were presented with adult nonspeech vocalizations (emotionally neutral, emotionally positive, and emotionally negative) and nonvocal environmental sounds. Infants displayed significant differential activation in the anterior portion of the temporal cortex, similarly to adults. Moreover, sad vocalizations modulated the activity of brain regions involved in processing affective stimuli such as the orbitofrontal cortex and insula. These results suggest remarkably early functional specialization for processing human voice and negative emotions.     

Quick minds slowed down: effects of rotation and stimulus category on the attentional blink

Background

Most people show a remarkable deficit to report the second of two targets when presented in close temporal succession, reflecting an attentional restriction known as the ‘attentional blink’ (AB). However, there are large individual differences in the magnitude of the effect, with some people showing no such attentional restrictions.

Methodology/Principal Findings

Here we present behavioral and electrophysiological evidence suggesting that these ‘non-blinkers’ can use alphanumeric category information to select targets at an early processing stage. When such information was unavailable and target selection could only be based on information that is processed relatively late (rotation), even non-blinkers show a substantial AB. Electrophysiologically, in non-blinkers this resulted in enhanced distractor-related prefrontal brain activity, as well as delayed target-related occipito-parietal activity (P3).

Conclusion/Significance

These findings shed new light on possible strategic mechanisms that may underlie individual differences in AB magnitude and provide intriguing clues as to how temporal restrictions as reflected in the AB can be overcome.     

A study of local effect and global effect on the microthermal bio-flows by molecular dynamics

This study develops a hybrid numerical scheme based on a molecular dynamics (MD) algorithm and the GROMACS protein data bank to analyze the thermal bio-flow of alanine molecules in a microchannel. The numerical results show that the velocity profiles in the microchannel are highly dependent on both global effects, i.e. the effective channel width and local effects, i.e. the thermal boundary conditions. Specifically, the magnitude of the fluctuations observed in the velocity profiles increase as the channel width decreases or as the thermal boundary temperature increases. The results presented in this study provide useful information regarding suitable microchannel widths and operational temperatures for bio-chip devices and contribute a further understanding of basic human thermal bio-flow phenomena, particularly, regarding the correlation between the rate of local metabolism, burn and frostbite events, respectively.     

The forest or the trees: preference for global over local image processing is reversed by prior experience in honeybees

Traditional models of insect vision have assumed that insects are only capable of low-level analysis of local cues and are incapable of global, holistic perception. However, recent studies on honeybee (Apis mellifera) vision have refuted this view by showing that this insect also processes complex visual information by using spatial configurations or relational rules. In the light of these findings, we asked whether bees prioritize global configurations or local cues by setting these two levels of image analysis in competition. We trained individual free-flying honeybees to discriminate hierarchical visual stimuli within a Y-maze and tested bees with novel stimuli in which local and/or global cues were manipulated. We demonstrate that even when local information is accessible, bees prefer global information, thus relying mainly on the object''s spatial configuration rather than on elemental, local information. This preference can be reversed if bees are pre-trained to discriminate isolated local cues. In this case, bees prefer the hierarchical stimuli with the local elements previously primed even if they build an incorrect global configuration. Pre-training with local cues induces a generic attentional bias towards any local elements as local information is prioritized in the test, even if the local cues used in the test are different from the pre-trained ones. Our results thus underline the plasticity of visual processing in insects and provide new insights for the comparative analysis of visual recognition in humans and animals.     

The relationship between specialization and local abundance: the case of helminth parasites of birds

Positive relationships are commonly observed between the abundance of a species in a locality and the frequency of its occurrence among localities on a larger scale. This pattern may not hold for parasitic organisms when the average abundance of a parasite among its hosts is related to the number of host species in which it occurs, because of the additive investment in specific adaptations to counter host immune responses required for each host species in a parasites repertoire. For a rigorous test of the hypothesis that there is a trade-off between the number of host species that can be successfully exploited and the average abundance of parasites in those hosts, one needs to take into account the phylogenetic (or taxonomic) distances among the host species used by a parasite. Differences in immune responses are likely to increase with increasing phylogenetic distances. The trade-off hypothesis was tested in a comparative analysis of 393 species of trematodes, cestodes and nematodes parasitic in birds surveyed from the same geographical area, using an index of host specificity that measures the average taxonomic distances between a parasites known host species. After correcting for the influences of parasite phylogeny and other potential confounding variables, mean abundance was negatively correlated with the average taxonomic distance among host species for nematodes, and with the variance in taxonomic distances among hosts for cestodes. In the case of trematodes, these variables covaried positively. The trade-off between average infection success and how taxonomically distant a parasites host species are from each other was only found in two of the three groups of helminths investigated, possibly because of compensating features in trematodes, such as their ability to multiply asexually in intermediate hosts. These results provide empirical evidence consistent with the hypothesis that specialization allows greater local adaptation and therefore greater local population abundance, supporting key predictions regarding the evolution of ecological specialization.Electronic Supplementary Material Supplementary material is available for this article at     

Scale dependence of effective specialization: its analysis and implications for estimates of global insect species richness

Estimates of global insect species richness are sometimes based on effective specialization, a calculation used to estimate the number of insect species that is restricted to a particular tree species. Yet it is not clear how effective specialization is influenced by spatial scale or characteristics of the insect community itself (e.g. species richness). We investigated scale dependence and community predictors of effective specialization using 15,907 beetles (583 species) collected by insecticide fogging from the crowns of 96 trees (including 32 Quercus trees) located in Ohio and Indiana. Trees were distributed across 24 forest stands (∼1 ha) nested within six sites (∼10–100 km²) and two ecoregions (> 1000 km²). Using paired-sample randomization tests, we found that effective specialization ( f _k ) exhibited negative scale-dependence in early (May–June 2000) and late (August–September 2000) sampling periods. Our average effective specialization ( F ) values — those that are comparable to Erwin's (1982) estimates — ranged from 19% to 97%, and increased as spatial scale decreased. We also found that beetle species richness and the number of shared beetle species across host trees were significant and consistent negative predictors of F . This shows that increases in spatial scale, species richness, and the number of trees (and/or tree species) all coincide with decreases in effective specialization. Collectively, our results indicate that estimates of global insect species richness based on effective specialization at a single spatial scale are overestimating the magnitude of global insect species richness. We propose that scale dependence should be promoted to a central concept in the research program on global estimates of species richness.     

Hemispheric lateralization in the processing of odor pleasantness versus odor names

It is well established that for most people linguistic processing is primarily a left hemisphere activity, whereas recent evidence has shown that basic odor perception is more lateralized to the right hemisphere. Importantly, under certain conditions, emotional responding also shows right hemisphere laterality. Hedonic (pleasantness) assessments constitute basic level emotional responses. Given that olfaction is predominantly ipsilateral in function, it was hypothesized that odor pleasantness evaluations may be accentuated by right nostril perception and that odor naming would be superior with left nostril perception. To test this prediction we presented eight familiar neutral-mildly pleasant odors for subjects to sniff through the left and right nostrils. Subjects smelled each odor twice (once through each nostril) at two different sessions, separated by 1 week. At each session subjects provided pleasantness, arousal and naming responses to each odorant. Results revealed that odors were rated as more pleasant when sniffed through the right nostril and named more correctly when sniffed through the left. No effects for arousal were obtained. These findings are consistent with previously demonstrated neural laterality in the processing of olfaction, emotion and language, and suggest that a local and functional convergence may exist between olfaction and emotional processing.     

Simple models for complex systems: exploiting the relationship between local and global densities

Simple temporal models that ignore the spatial nature of interactions and track only changes in mean quantities, such as global densities, are typically used under the unrealistic assumption that individuals are well mixed. These so-called mean-field models are often considered overly simplified, given the ample evidence for distributed interactions and spatial heterogeneity over broad ranges of scales. Here, we present one reason why such simple population models may work even when mass-action assumptions do not hold: spatial structure is present but it relates to global densities in a special way. With an individual-based predator–prey model that is spatial and stochastic, and whose mean-field counterpart is the classic Lotka–Volterra model, we show that the global densities and densities of pairs (or spatial covariances) establish a bi-power law at the stationary state and also in their transient approach to this state. This relationship implies that the dynamics of global densities can be written simply as a function of those densities alone without invoking pairs (or higher order moments). The exponents of the bi-power law for the predation rate exhibit a remarkable robustness to changes in model parameters. Evidence is presented for a connection of our findings to the existence of a critical phase transition in the dynamics of the spatial system. We discuss the application of similar modified mean-field equations to other ecological systems for which similar transitions have been described, both in models and empirical data.     

Preserved functional specialization for spatial processing in the middle occipital gyrus of the early blind

The occipital cortex (OC) of early-blind humans is activated during various nonvisual perceptual and cognitive tasks, but little is known about its modular organization. Using functional MRI we tested whether processing of auditory versus tactile and spatial versus nonspatial information was dissociated in the OC of the early blind. No modality-specific OC activation was observed. However, the right middle occipital gyrus (MOG) showed a preference for spatial over nonspatial processing of both auditory and tactile stimuli. Furthermore, MOG activity was correlated with accuracy of individual sound localization performance. In sighted controls, most of extrastriate OC, including the MOG, was deactivated during auditory and tactile conditions, but the right MOG was more activated during spatial than nonspatial visual tasks. Thus, although the sensory modalities driving the neurons in the reorganized OC of blind individuals are altered, the functional specialization of extrastriate cortex is retained regardless of visual experience.     

The effect of scopolamine on the stimulus change phenomenon.

Saline treated rats chose a novel stimulus, whereas rats injected with scopolamine showed no preference for a novel or familiar stimulus. Scopolamine decreased the latency to approach the stimulus. The effects of procedural variables on drug-induced changes is stressed.     

Homeostatic synaptic plasticity: local and global mechanisms for stabilizing neuronal function

Neural circuits must maintain stable function in the face of many plastic challenges, including changes in synapse number and strength, during learning and development. Recent work has shown that these destabilizing influences are counterbalanced by homeostatic plasticity mechanisms that act to stabilize neuronal and circuit activity. One such mechanism is synaptic scaling, which allows neurons to detect changes in their own firing rates through a set of calcium-dependent sensors that then regulate receptor trafficking to increase or decrease the accumulation of glutamate receptors at synaptic sites. Additional homeostatic mechanisms may allow local changes in synaptic activation to generate local synaptic adaptations, and network-wide changes in activity to generate network-wide adjustments in the balance between excitation and inhibition. The signaling pathways underlying these various forms of homeostatic plasticity are currently under intense scrutiny, and although dozens of molecular pathways have now been implicated in homeostatic plasticity, a clear picture of how homeostatic feedback is structured at the molecular level has not yet emerged. On a functional level, neuronal networks likely use this complex set of regulatory mechanisms to achieve homeostasis over a wide range of temporal and spatial scales.     

Modelling pathogen transmission: the interrelationship between local and global approaches

We describe two spatial (cellular automaton) host-pathogen models with contrasting types of transmission, where the biologically realistic transmission mechanisms are based entirely on 'local' interactions. The two models, fixed contact area (FCA) and fixed contact number (FCN), may be viewed as local 'equivalents' of commonly used global density- (and frequency-) dependent models. Their outputs are compared with each other and with the patterns generated by these global terms. In the FCN model, unoccupied cells are bypassed, but in the FCA model these impede pathogen spread, extending the period of the epidemic and reducing the prevalence of infection when the pathogen persists. Crucially, generalized linear modelling reveals that the global transmission terms betaSI and beta'SI/N are equally good at describing transmission in both the FCA and FCN models when infected individuals are homogeneously distributed and N is approximately constant, as at the quasi-equilibrium. However, when N varies, the global frequency-dependent term beta'SI/N is better than the density-dependent one, betaSI, at describing transmission in both the FCA and FCN models. Our approach may be used more generally to compare different local contact structures and select the most appropriate global transmission term.     

Conditioning of active type avoidance in the rat : effect of the interval between conditioned stimulus and unconditioned stimulus

Lengthening the time interval between the conditioned stimulus and the unconditioned stimulus increases the number of active avoidance conditioned responses in subjects that have been trained to a stable level of performance in many previous conditioning sessions. In the present research, rats chosen from a population specially selected for low rates of avoidance conditioning have been used. In addition to this characteristic, subjects were chosen for the exhibition of an apparent absence of retention from one day to another. The dependency of the number of conditioned responses on the time interval between conditioned stimulus and unconditioned stimulus may lead to wrong evaluation of the subjects' conditioning level. In fact, the level of conditioning may be attributed to either learning or memory processes when in many cases it is determined only by the latency time of the conditioned response. The conditioned response has no possibility of manifesting itself when its latency time exceeds in length the time interval between conditioned stimulus and unconditioned stimulus.