scholarly journals Camouflage, communication and thermoregulation: lessons from colour changing organisms

2008 ◽  
Vol 364 (1516) ◽  
pp. 463-470 ◽  
Author(s):  
Devi Stuart-Fox ◽  
Adnan Moussalli
Keyword(s):  
Visual Perception ◽  
Visual Processing ◽  
Comparative Studies ◽  
Visual Cues ◽  
Colour Change ◽  
Visual Environment ◽  
Multiple Predators ◽  
Physiological Colour Change ◽  
Colour Patterns ◽  
Insight Into

Organisms capable of rapid physiological colour change have become model taxa in the study of camouflage because they are able to respond dynamically to the changes in their visual environment. Here, we briefly review the ways in which studies of colour changing organisms have contributed to our understanding of camouflage and highlight some unique opportunities they present. First, from a proximate perspective, comparison of visual cues triggering camouflage responses and the visual perception mechanisms involved can provide insight into general visual processing rules. Second, colour changing animals can potentially tailor their camouflage response not only to different backgrounds but also to multiple predators with different visual capabilities. We present new data showing that such facultative crypsis may be widespread in at least one group, the dwarf chameleons. From an ultimate perspective, we argue that colour changing organisms are ideally suited to experimental and comparative studies of evolutionary interactions between the three primary functions of animal colour patterns: camouflage; communication; and thermoregulation.

Object Perception

2018 ◽  
Author(s):  
Scott P. Johnson
Keyword(s):  
Visual Perception ◽  
Visual Processing ◽  
Time Course ◽  
Three Dimensional ◽  
Object Perception ◽  
Developmental Time ◽  
Visual Deprivation ◽  
Visual Features ◽  
Visual Environment ◽  
3D Space

Visual scenes tend to be very complex: a multitude of overlapping surfaces varying in shape, color, texture, and depth relative to the observer. Yet most observers effortlessly perceive that the visual environment is composed of distinct objects, laid out across space, each with a particular shape that can be inferred from partial views and incomplete information. Moreover, observers generally expect objects to be continuous across space and time, to have a certain shape, and to be solid in three-dimensional (3D) space. The cortical visual system processes information for objects first by coding visual features, then by linking features into units, and last by interpretation of units as objects that may be recognizable or otherwise relevant to the observer. This way of conceptualizing object perception maps roughly onto processes of lower-, middle-, and higher-level visual processing that have long formed the basis for investigations of visual perception in adults, as well as theories of object perception, the ways visual deprivation reduces object perception skills, and the developmental time course of object perception in infancy.

Behavioural and EEG atypicalities during rest, visual perception, and cognitive control in autistic adults

2020 ◽  
Author(s):  
Amandine Lassalle ◽  
Michael X Cohen ◽  
Laura Dekkers ◽  
Elizabeth Milne ◽  
Rasa Gulbinaite ◽  
...  
Keyword(s):  
Visual Perception ◽  
Cognitive Control ◽  
Visual Processing ◽  
Autism Spectrum ◽  
Neural Dynamics ◽  
Simple Explanation ◽  
Control Task ◽  
Neural Structure ◽  
Eeg Power ◽  
Autistic Adults

Background: People with an Autism Spectrum Condition diagnosis (ASD) are hypothesized to show atypical neural dynamics, reflecting differences in neural structure and function. However, previous results regarding neural dynamics in autistic individuals have not converged on a single pattern of differences. It is possible that the differences are cognitive-set-specific, and we therefore measured EEG in autistic individuals and matched controls during three different cognitive states: resting, visual perception, and cognitive control.Methods: Young adults with and without an ASD (N=17 in each group) matched on age (range 20 to 30 years), sex, and estimated Intelligence Quotient (IQ) were recruited. We measured their behavior and their EEG during rest, a task requiring low-level visual perception of gratings of varying spatial frequency, and the “Simon task” to elicit activity in the executive control network. We computed EEG power and Inter-Site Phase Clustering (ISPC; a measure of connectivity) in various frequency bands.Results: During rest, there were no ASD vs. controls differences in EEG power, suggesting typical oscillation power at baseline. During visual processing, without pre-baseline normalization, we found decreased broadband EEG power in ASD vs. controls, but this was not the case during the cognitive control task. Furthermore, the behavioral results of the cognitive control task suggest that autistic adults were better able to ignore irrelevant stimuli.Conclusions: Together, our results defy a simple explanation of overall differences between ASD and controls, and instead suggest a more nuanced pattern of altered neural dynamics that depend on which neural networks are engaged.

Visual and Tactile Information About Object-Curvature Control Fingertip Forces and Grasp Kinematics in Human Dexterous Manipulation

2000 ◽  
Vol 84 (6) ◽  
pp. 2984-2997 ◽  
Author(s):  
Per Jenmalm ◽  
Seth Dahlstedt ◽  
Roland S. Johansson
Keyword(s):  
Visual Processing ◽  
Visual Cues ◽  
Grip Force ◽  
Center Of Mass ◽  
Precision Grip ◽  
Sensory Information ◽  
Afferent Input ◽  
Dependent Manner ◽  
Tactile Sensibility ◽  
Grasp Stability

Most objects that we manipulate have curved surfaces. We have analyzed how subjects during a prototypical manipulatory task use visual and tactile sensory information for adapting fingertip actions to changes in object curvature. Subjects grasped an elongated object at one end using a precision grip and lifted it while instructed to keep it level. The principal load of the grasp was tangential torque due to the location of the center of mass of the object in relation to the horizontal grip axis joining the centers of the opposing grasp surfaces. The curvature strongly influenced the grip forces required to prevent rotational slips. Likewise the curvature influenced the rotational yield of the grasp that developed under the tangential torque load due to the viscoelastic properties of the fingertip pulps. Subjects scaled the grip forces parametrically with object curvature for grasp stability. Moreover in a curvature-dependent manner, subjects twisted the grasp around the grip axis by a radial flexion of the wrist to keep the desired object orientation despite the rotational yield. To adapt these fingertip actions to object curvature, subjects could use both vision and tactile sensibility integrated with predictive control. During combined blindfolding and digital anesthesia, however, the motor output failed to predict the consequences of the prevailing curvature. Subjects used vision to identify the curvature for efficient feedforward retrieval of grip force requirements before executing the motor commands. Digital anesthesia caused little impairment of grip force control when subjects had vision available, but the adaptation of the twist became delayed. Visual cues about the form of the grasp surface obtained before contact was used to scale the grip force, whereas the scaling of the twist depended on visual cues related to object movement. Thus subjects apparently relied on different visuomotor mechanisms for adaptation of grip force and grasp kinematics. In contrast, blindfolded subjects used tactile cues about the prevailing curvature obtained after contact with the object for feedforward adaptation of both grip force and twist. We conclude that humans use both vision and tactile sensibility for feedforward parametric adaptation of grip forces and grasp kinematics to object curvature. Normal control of the twist action, however, requires digital afferent input, and different visuomotor mechanisms support the control of the grasp twist and the grip force. This differential use of vision may have a bearing to the two-stream model of human visual processing.

scholarly journals Familiarity affects the same event-related brain potential components in note readers and non-note readers

2018 ◽  
Vol 1 ◽  
pp. 205920431877823 ◽  
Author(s):  
Linda Becker
Keyword(s):  
Visual Perception ◽  
Neural Plasticity ◽  
Visual Processing ◽  
Music Perception ◽  
Reaction Times ◽  
Future Research ◽  
Familiarity Effect ◽  
Professional Musicians ◽  
Brain Potential ◽  
Cognitive Domains

Musical expertise can lead to neural plasticity in specific cognitive domains (e.g., in auditory music perception). However, not much is known about whether the visual perception of simple musical symbols (e.g., notes) already differs between musicians and non-musicians. This was the aim of the present study. Therefore, the Familiarity Effect (FE) – an effect which occurs quite early during visual processing and which is based on prior knowledge or expertise – was investigated. The FE describes the phenomenon that it is easier to find an unfamiliar element (e.g., a mirrored eighth note) in familiar elements (e.g., normally oriented eighth notes) than to find a familiar element in a background of unfamiliar elements. It was examined whether the strength of the FE for eighth notes differs between note readers and non-note readers. Furthermore, it was investigated at which component of the event-related brain potential (ERP) the FE occurs. Stimuli that consisted of either eighth notes or vertically mirrored eighth notes were presented to the participants (28 note readers, 19 non-note readers). A target element was embedded in half of the trials. Reaction times, sensitivity, and three ERP components (the N1, N2p, and P3) were recorded. For both the note readers and the non-note readers, strong FEs were found in the behavioral data. However, no differences in the strength of the FE between groups were found. Furthermore, for both groups, the FE was found for the same ERP components (target-absent trials – N1 latency; target-present trials – N2p latency, N2p amplitude, P3 amplitude). It is concluded that the early visual perception of eighth note symbols does not differ between note readers and non-note readers. However, future research is needed to verify this for more complex musical stimuli and for professional musicians.

scholarly journals Shared and Independent Neural Representation Between Visual Perception and Mental Imagery

2021 ◽  
Author(s):  
Yingying Huang ◽  
Frank Pollick ◽  
Ming Liu ◽  
Delong Zhang
Keyword(s):  
Visual Perception ◽  
Mental Imagery ◽  
Activity Patterns ◽  
Neural Representation ◽  
Gabor Features ◽  
Visual Areas ◽  
Neural Substrate ◽  
Early Visual Cortex ◽  
Human Participants ◽  
Insight Into

Abstract Visual mental imagery and visual perception have been shown to share a hierarchical topological visual structure of neural representation. Meanwhile, many studies have reported a dissociation of neural substrate between mental imagery and perception in function and structure. However, we have limited knowledge about how the visual hierarchical cortex involved into internally generated mental imagery and perception with visual input. Here we used a dataset from previous fMRI research (Horikawa & Kamitani, 2017), which included a visual perception and an imagery experiment with human participants. We trained two types of voxel-wise encoding models, based on Gabor features and activity patterns of high visual areas, to predict activity in the early visual cortex (EVC, i.e., V1, V2, V3) during perception, and then evaluated the performance of these models during mental imagery. Our results showed that during perception and imagery, activities in the EVC could be independently predicted by the Gabor features and activity of high visual areas via encoding models, which suggested that perception and imagery might share neural representation in the EVC. We further found that there existed a Gabor-specific and a non-Gabor-specific neural response pattern to stimuli in the EVC, which were shared by perception and imagery. These findings provide insight into mechanisms of how visual perception and imagery shared representation in the EVC.

scholarly journals The lantern shark's light switch: turning shallow water crypsis into midwater camouflage

2010 ◽  
Vol 6 (5) ◽  
pp. 685-687 ◽  
Author(s):  
Julien M. Claes ◽  
Jérôme Mallefet
Keyword(s):  
Shallow Water ◽  
Deep Sea ◽  
Light Emission ◽  
Colour Change ◽  
Hormonal Control ◽  
Nervous Control ◽  
Luminous Bacteria ◽  
Physiological Colour Change ◽  
Physiological Suppression

Bioluminescence is a common feature in the permanent darkness of the deep-sea. In fishes, light is emitted by organs containing either photogenic cells (intrinsic photophores), which are under direct nervous control, or symbiotic luminous bacteria (symbiotic photophores), whose light is controlled by secondary means such as mechanical occlusion or physiological suppression. The intrinsic photophores of the lantern shark Etmopterus spinax were recently shown as an exception to this rule since they appear to be under hormonal control. Here, we show that hormones operate what amounts to a unique light switch, by acting on a chromatophore iris, which regulates light emission by pigment translocation. This result strongly suggests that this shark's luminescence control originates from the mechanism for physiological colour change found in shallow water sharks that also involves hormonally controlled chromatophores: the lantern shark would have turned the initial shallow water crypsis mechanism into a midwater luminous camouflage, more efficient in the deep-sea environment.

Comparative studies on glial markers

1981 ◽  
Vol 95 (1) ◽  
pp. 167-180
Author(s):  
B. I. Roots
Keyword(s):  
Manduca Sexta ◽  
Comparative Studies ◽  
Nervous Tissue ◽  
Functional Role ◽  
Functional Interactions ◽  
Lower Vertebrates ◽  
Fresh Insight ◽  
Insight Into ◽  
Biochemical Differentiation

Macromolecular markers for glial cells have been sought for a variety of reasons. One of the earliest was the need for a means of assessing the purity of cell and subcellular fractions prepared from nervous tissue. While there is still a requirement for this kind of tool, emphasis has shifted towards seeking information on biochemical differentiation among cells and their functional interactions. A brief general review will be made of glial markers and two of these, 2′,3′-cyclic nucleotide 3′-phosphohydrolase (CNP) and glutamine synthetase (GS), will be considered in detail. Until recently studies of markers have been concentrated on the higher vertebrates and those on lower vertebrates and invertebrates have hardly begun. However, such comparative studies may lead to fresh insight into old problems. For example, CNP has long been regarded as a marker for myelin and oligodendrocytes but it has not been possible to attribute a functional role to it and its relation to myelination has remained obscure. The finding that it is present in the glia of a moth Manduca sexta which lacks myelin provides a stimulus for a fresh approach to the problem. Another example is provided by studies on GS. This enzyme is found in astrocyte feet and preliminary results indicate that it is localized also in the perineurial glia of Aplysia ganglia. These results lead to a reconsideration of the perennial question of the possible role of astrocyte feet in barrier mechanisms. Extension of comparative studies may not only raise new questions but also provide some answers.

Principles of Binocular Stereoscopic Imaging

2014 ◽  
pp. 38-58
Author(s):  
Geoff Ogram
Keyword(s):  
Visual Perception ◽  
Depth Perception ◽  
Visual Cues ◽  
Stereoscopic Images ◽  
Stereoscopic Imaging ◽  
Recorded Image

The relation between visual perception and the recorded image is discussed in this chapter, emphasising the historical growth of the understanding of depth perception and its visual cues. The stereoscopic principle is explained in detail, and figures are given for comfortable viewing of stereoscopic images.

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