Neural Constraints Research Articles

Is parasitoid acceptance of different host species dynamic?

Summary Parasitoid acceptance of host individuals that differ in suitability is dynamic, varying with physiological state and experience. Female parasitoids with high egg loads and low life expectancy (i.e. time limited) are more willing to accept hosts with low suitability for progeny development than females with low egg loads and high life expectancy (i.e. egg limited). However, studies of dynamic acceptance behaviour in parasitoids have only considered high‐ vs. low‐suitability host individuals within the same host species. Here, we report the first results on whether acceptance of individuals from different host species that vary in suitability is also dynamic, using two aphid parasitoid species in the genus Aphelinus (Hymenoptera: Aphelinidae). Stressors (starvation and age) and experience that increase time limitation did not affect the acceptance of low‐suitability host species by two Aphelinus species with reciprocal specificities. Oviposition in a high‐suitability host species increased with egg load, but did not vary with egg load for females exposed to low‐suitability host species. This is an unexpected pattern since it results in proportionally higher acceptance of low‐suitability hosts with decreasing egg load. The stability of behavioural host specificity in these parasitoids under very stressful conditions might be explained by (i) frequent transient egg limitation, (ii) higher fitness from egg resorption than oviposition or (iii) neural constraints on host recognition. If neural constraints restrict the ability of these specialists to change their behaviour under stress, we predict that generalist species of Aphelinus should show greater dynamism in acceptance of low‐suitability hosts. We are testing this prediction using Aphelinus species with very broad host ranges.

The brain set free: Lifting neural constraints could turn back time, making way for youthful flexibility

Science NewsVolume 182, Issue 3 p. 18-21 Feature The brain set free: Lifting neural constraints could turn back time, making way for youthful flexibility Laura Sanders, Laura SandersSearch for more papers by this author Laura Sanders, Laura SandersSearch for more papers by this author First published: 01 August 2012 https://doi.org/10.1002/scin.5591820322Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Volume182, Issue311 August 2012Pages 18-21 RelatedInformation

Review and perspective: neuromechanical considerations for predicting muscle activation patterns for movement

Muscle coordination may be difficult or impossible to predict accurately based on biomechanical considerations alone because of redundancy in the musculoskeletal system. Because many solutions exist for any given movement, the role of the nervous system in further constraining muscle coordination patterns for movement must be considered in both healthy and impaired motor control. On the basis of computational neuromechanical analyses of experimental data combined with modeling techniques, we have demonstrated several such neural constraints on the temporal and spatial patterns of muscle activity during both locomotion and postural responses to balance perturbations. We hypothesize that subject-specific and trial-by-trial differences in muscle activation can be parameterized and understood by a hierarchical and low-dimensional framework that reflects the neural control of task-level goals. In postural control, we demonstrate that temporal patterns of muscle activity may be governed by feedback control of task-level variables that represent the overall goal-directed motion of the body. These temporal patterns then recruit spatially-fixed patterns of muscle activity called muscle synergies that produce the desired task-level biomechanical functions that require multijoint coordination. Moreover, these principles apply more generally to movement, and in particular to locomotor tasks in both healthy and impaired individuals. Overall, understanding the goals and organization of the neural control of movement may provide useful reduced dimension parameter sets to address the degrees-of-freedom problem in musculoskeletal movement control. More importantly, however, neuromechanical analyses may lend insight and provide a framework for understanding subject-specific and trial-by-trial differences in movement across both healthy and motor-impaired populations.

Improved Motion Perception and Impaired Spatial Suppression following Disruption of Cortical Area MT/V5

As stimulus size increases, motion direction of high-contrast patterns becomes increasingly harder to perceive. This counterintuitive behavioral result, termed "spatial suppression," is hypothesized to reflect center-surround antagonism-a receptive field property ubiquitous in sensory systems. Prior research proposed that spatial suppression of motion signals is a direct correlate of center-surround antagonism within cortical area MT. Here, we investigated whether human MT/V5 is indeed causally involved in spatial suppression of motion signals. The key assumption is that a disruption of neural mechanisms that play a critical role in spatial suppression could allow these normally suppressed motion signals to reach perceptual awareness. Thus, our hypothesis was that a disruption of MT/V5 should weaken spatial suppression and, consequently, improve motion perception of large, moving patterns. To disrupt MT/V5, we used offline 1 Hz transcranial magnetic stimulation (TMS)-a method that temporarily attenuates normal functioning of the targeted cortex. Early visual areas were also targeted as a control site. The results supported our hypotheses and showed that disruption of MT/V5 improved motion discrimination of large, moving stimuli, presumably by weakening surround suppression strength. This effect was specific to MT/V5 stimulation and contralaterally presented stimuli. Evidently, the critical neural constraints limiting motion perception of large, high-contrast stimuli involve MT/V5. Additionally, our findings mimic spatial suppression deficits that are observed in several patient populations and implicate impaired MT/V5 processes as likely neural correlates for the reported perceptual abnormalities in the elderly, patients with schizophrenia and those with a history of depression.

How does perceptual grouping synchronize quickly under realistic neural constraints?

How does perceptual grouping synchronize quickly under realistic neural constraints?

Hjernen og følelser – fra barn til voksen

Contemporary neuroscience relates human behaviour, emotions and cognition to underlying neurobiological processes in the brain. Increased awareness of such processes may improve our understanding of emotional regulatory problems and development of psychopathology in some children and adolescents.This article is based on articles identified through a non-systematic search in PubMed and on publications from the authors' own database.Several processes form the biological basis for how children and adolescents regulate their emotions when relating to others: linear development of white matter, growth and subsequent elimination of gray matter and maturation of various neuronal networks in the brain. Emotional regulation develops discontinuously in children and adolescents, and varying degrees of maturation of specific neural networks involved in self-regulation may explain different behavioural traits that are typical for specific age groups.Emotional regulation develops in a complex interaction between a child's relationships, experiences, activities and underlying biological/genetic factors. Knowledge of these underlying neural constraints may contribute to understanding typical behavioural traits at different ages and in children and adolescents who have difficulties controlling their emotions. Identification of genetic or environmental factors that can help children and adolescents regulate their feelings may also be important for development of more specific therapies.

Cascaded Bayesian processes: An account of bias in orientation perception

Following adaptation to an oriented (1-d) signal in central vision, the orientation of subsequently viewed test signals may appear repelled away from or attracted towards the adapting orientation. Small angular differences between the adaptor and test yield ‘repulsive’ shifts, while large angular differences yield ‘attractive’ shifts. In peripheral vision, however, both small and large angular differences yield repulsive shifts. To account for these tilt after-effects (TAEs), a cascaded model of orientation estimation that is optimized using hierarchical Bayesian methods is proposed. The model accounts for orientation bias through adaptation-induced losses in information that arise because of signal uncertainties and neural constraints placed upon the propagation of visual information. Repulsive (direct) TAEs arise at early stages of visual processing from adaptation of orientation-selective units with peak sensitivity at the orientation of the adaptor ( θ ) . Attractive (indirect) TAEs result from adaptation of second-stage units with peak sensitivity at θ and θ + 90 ° , which arise from an efficient stage of linear compression that pools across the responses of the first-stage orientation-selective units. A spatial orientation vector is estimated from the transformed oriented unit responses. The change from attractive to repulsive TAEs in peripheral vision can be explained by the differing harmonic biases resulting from constraints on signal power (in central vision) versus signal uncertainties in orientation (in peripheral vision). The proposed model is consistent with recent work by computational neuroscientists in supposing that visual bias reflects the adjustment of a rational system in the light of uncertain signals and system constraints.

Neural constraints in kinematics of head-free gaze

Introduction Gaze position (eye in space) does not use all three rotational degrees of freedom of eye or head mechanics [1]. In classical studies of head-free saccades, the reduction of degrees of freedom is described by Donders' law [2]: 3Deye orientations are located on a 2D-surface [3]. But only few studies investigated the dependence of Donders' law on the direction of the saccade preceding the actual fixation. The aim of this study was to perform this analysis for eye and head movements simultaneously during headfree gaze shifts. Furthermore, we collected a data set in normal adult humans for comparison with oculomotor disorder patients.

Neural and cognitive plasticity: From maps to minds.

Some species and individuals are able to learn cognitive skills more flexibly than others. Learning experiences and cortical function are known to contribute to such differences, but the specific factors that determine an organism's intellectual capacities remain unclear. Here, an integrative framework is presented suggesting that variability in cognitive plasticity reflects neural constraints on the precision and extent of an organism's stimulus representations. Specifically, it is hypothesized that cognitive plasticity depends on the number and diversity of cortical modules that an organism has available as well as the brain's capacity to flexibly reconfigure and customize networks of these modules. The author relates this framework to past proposals on the neural mechanisms of intelligence, including (a) the relationship between brain size and intellectual capacity; (b) the role of prefrontal cortex in cognitive control and the maintenance of stimulus representations; and (c) the impact of neural plasticity and efficiency on the acquisition and performance of cognitive skills. The proposed framework provides a unified account of variability in cognitive plasticity as a function of species, age, and individual, and it makes specific predictions about how manipulations of cortical structure and function will impact intellectual capacity.

The biology and evolution of music: A comparative perspective

Studies of the biology of music (as of language) are highly interdisciplinary and demand the integration of diverse strands of evidence. In this paper, I present a comparative perspective on the biology and evolution of music, stressing the value of comparisons both with human language, and with those animal communication systems traditionally termed “song”. A comparison of the “design features” of music with those of language reveals substantial overlap, along with some important differences. Most of these differences appear to stem from semantic, rather than structural, factors, suggesting a shared formal core of music and language. I next review various animal communication systems that appear related to human music, either by analogy (bird and whale “song”) or potential homology (great ape bimanual drumming). A crucial comparative distinction is between learned, complex signals (like language, music and birdsong) and unlearned signals (like laughter, ape calls, or bird calls). While human vocalizations clearly build upon an acoustic and emotional foundation shared with other primates and mammals, vocal learning has evolved independently in our species since our divergence with chimpanzees. The convergent evolution of vocal learning in other species offers a powerful window into psychological and neural constraints influencing the evolution of complex signaling systems (including both song and speech), while ape drumming presents a fascinating potential homology with human instrumental music. I next discuss the archeological data relevant to music evolution, concluding on the basis of prehistoric bone flutes that instrumental music is at least 40,000 years old, and perhaps much older. I end with a brief review of adaptive functions proposed for music, concluding that no one selective force (e.g., sexual selection) is adequate to explaining all aspects of human music. I suggest that questions about the past function of music are unlikely to be answered definitively and are thus a poor choice as a research focus for biomusicology. In contrast, a comparative approach to music promises rich dividends for our future understanding of the biology and evolution of music.

The soap bubble: Phenomenal state or perceptual system dynamics?

The Gestalt Bubble model describes a subjective phenomenal experience (what is seen) without taking into account the extraphenomenal constraints of perceptual experience (why it is seen as it is). If it intends to be an explanatory model, then it has to include either stimulus or neural constraints, or both.

Social, Cognitive, and Neural Constraints on Subjectivity and Agency: Implications for Dissociative Identity Disorder

Social, Cognitive, and Neural Constraints on Subjectivity and Agency: Implications for Dissociative Identity Disorder

Three-dimensional eye-head coordination is implemented downstream from the superior colliculus.

How the brain transforms two-dimensional visual signals into multi-dimensional motor commands, and subsequently how it constrains the redundant degrees of freedom, are fundamental problems in sensorimotor control. During fixations between gaze shifts, the redundant torsional degree of freedom is determined by various neural constraints. For example, the eye- and head-in-space are constrained by Donders' law, whereas the eye-in-head obeys Listing's law. However, where and how the brain implements these laws is not yet known. In this study, we show that eye and head movements, elicited by unilateral microstimulations of the superior colliculus (SC) in head-free monkeys, obey the same Donders' strategies observed in normal behavior (i.e., Listing's law for final eye positions and the Fick strategy for the head). Moreover, these evoked movements showed a pattern of three-dimensional eye-head coordination, consistent with normal behavior, where the eye is driven purposely out of Listing's plane during the saccade portion of the gaze shift in opposition to a subsequent torsional vestibuloocular reflex slow phase, such that the final net torsion at the end of each head-free gaze shift is zero. The required amount of saccade-related torsion was highly variable, depending on the initial position of the eye and head prior to a gaze shift and the size of the gaze shift, pointing to a neural basis of torsional control. Because these variable, context-appropriate torsional saccades were correctly elicited by fixed SC commands during head-free stimulations, this shows that the SC only encodes the horizontal and vertical components of gaze, leaving the complexity of torsional organization to downstream control systems. Thus we conclude that Listing's and Donders' laws of the eyes and head, and their three-dimensional coordination mechanisms, must be implemented after the SC.

The cost of polyphagy: oviposition decision time vs error rate in a butterfly

Neural constraints on information processing have emerged as a possible general explanation for why a majority of plant‐feeding insects are relative specialists. According to the hypothesis, acquiring and processing information necessary to make fast and accurate oviposition decisions will carry a cost. As plants constitute a vast but diverse resource, the cost can be expected to increase with increasing host range. The cost can be paid in two currencies: time or accuracy. Both types of costs have been demonstrated, using a variety of taxa including butterflies. However, all studies have measured either one of the two currencies. Hence, there is the possibility that a decrease in one of the currencies can be compensated by an increase in the other, in which case the net outcome may not be a cost at all. Poor oviposition decisions could then be counterbalanced by shorter decision times, which could lead to higher realized fecundity. Using two strains of butterflies (Polygonia c‐album) with different degrees of specificity, I test the hypothesis that the previously reported higher error rates in the more polyphagous butterflies are compensated by shorter decision times at oviposition. Post‐alighting decision times were measured while the females evaluated a preferred plant (Urtica dioica) for oviposition. Contrary to the expectations, the polyphagous butterflies actually had longer decision times than the specialized butterflies, giving no support for the quality vs. quantity hypothesis. Instead, the results suggests that the polyphagous butterflies do pay a real cost for their wide host range and thus gives increased support for the information processing hypothesis as a general explanation for the widespread host specificity among plant‐feeding insects.

Reviews: Motion Vision: Computational, Neural and Ecological Constraints

Reviews: Motion Vision: Computational, Neural and Ecological Constraints

Upper-Limb Discoordination in Hemiparetic Stroke: Implications for Neurorehabilitation

Clinically, upper-limb discoordination after stroke is evident in the form of stereotypic movement patterns that reflect a loss of independent joint control. These movement abnormalities, in conjunction with our recent quantitative findings under isometric conditions, provide evidence for an impaired capacity to generate certain muscle coactivation patterns in the impaired limb. In this article, we examine the parallels that exist between coordination disturbances observed under isometric and movement conditions. Our results suggest that discoordination in stroke may largely represent a manifestation of additional neural constraints on motor outflow. The neurotherapeutic implications of our findings are discussed.

Neural constraints on cognition in sleep

Certain features of Stage NREM sleep – for example, rhythmic voltage oscillation in thalamic neurons – are physiologically inhospitable to “REM sleep processes.” In Stage 2, the sleep spindle and its refractory period must limit the incursion of “covert REM,” and thus the extent of REM-like cognition. If these hyperpolarization-dependent events also inform Stage NREM cognition, does a “1-gen” model suffice to account for REM-NREM differences?[Nielsen]

Color constancy in a rough world

This article introduces a new psychophysical method for a performance-based view of color constancy, in which the task for the observer is to identify similar materials across illuminants despite possible appearance changes, and to simultaneously extract the relative colors of the illuminants.15 The article also examines generality conditions for the task. Physical and neural constraints on chromatic signals make it possible to use simple affine-heuristic algorithms to solve the correspondence problem for most Lambertian surfaces in random spatial arrangements under different illuminants. For rough surfaces, where the relative amounts of interface and body reflections vary with source-object-sensor geometry, the algorithms solve the correspondence problem across illuminants for a constant source-object-sensor geometry, but are not successful for rough surfaces in different spatial arrangements under different illuminants. © 2000 John Wiley & Sons, Inc. Col Res Appl, 26, S192–S200, 2001

Implicit learning of tonality: a self-organizing approach.

Tonal music is a highly structured system that is ubiquitous in our cultural environment. We demonstrate the acquisition of implicit knowledge of tonal structure through neural self-organization resulting from mere exposure to simultaneous and sequential combinations of tones. In the process of learning, a network with fundamental neural constraints comes to internalize the essential correlational structure of tonal music. After learning, the network was run through a range of experiments from the literature. The model provides a parsimonious account of a variety of empirical findings dealing with the processing of tone, chord, and key relationships, including relatedness judgments, memory judgments, and expectancies. It also illustrates the plausibility of activation being a unifying mechanism underlying a range of cognitive tasks.

Plasticity and the Problem of Choice in Food Selection

The interaction of plasticity, choice, and diet breadth is discussed, and the problems faced by generalists highlighted. The case is made that insects with very broad diets, and hence an ability to choose among foods at some time in their life history, have a problem making decisions that are efcient in terms of speed and quality. Reinterpretations of data from some insect groups, such as sower visitors, are presented in the light of such a neural problem, and explicit tests of the concept that there are neural constraints are reviewed. Possible mechanisms underlying changes in diet breadth are discussed. KEY WORDShost plant choice, diet breadth, specialist, generalist, selective attention, neural constraints IAM PLEASEDto provide this article for a commemo-