scholarly journals Bilaterally Symmetrical: To Be or Not to Be?

Symmetry ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 326 ◽  
Author(s):  
Michael C. Corballis
Keyword(s):  
Sensory Input ◽  
Biological Evolution ◽  
Bilateral Symmetry ◽  
Natural World ◽  
Mirror Reflection ◽  
Human World ◽  
Left And Right ◽  
High Degree ◽  
Molecular Asymmetries ◽  
The Brain

We belong to a clade of species known as the bilateria, with a body plan that is essentially symmetrical with respect to left and right, an adaptation to the indifference of the natural world to mirror-reflection. Limbs and sense organs are in bilaterally symmetrical pairs, dictating a high degree of symmetry in the brain itself. Bilateral symmetry can be maladaptive, though, especially in the human world where it is important to distinguish between left and right sides, and between left-right mirror images, as in reading directional scripts. The brains of many animals have evolved asymmetries, often but not exclusively in functions not dependent on sensory input or immediate reaction to the environment. Brain asymmetries in humans have led to exaggerate notions of a duality between the sides of the brain. The tradeoff between symmetry and asymmetry results in individual differences in brain asymmetries and handedness, contributing to a diversity of aptitude and divisions of labor. Asymmetries may have their origin in fundamental molecular asymmetries going far back in biological evolution.

scholarly journals Leaf Bilateral Symmetry and the Scaling of the Perimeter vs. the Surface Area in 15 Vine Species

Forests ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 246 ◽  
Author(s):  
Peijian Shi ◽  
Ülo Niinemets ◽  
Cang Hui ◽  
Karl J. Niklas ◽  
Xiaojing Yu ◽  
...  
Keyword(s):  
Surface Area ◽  
Leaf Shape ◽  
Bilateral Symmetry ◽  
Scaling Relationship ◽  
Leaf Surface Area ◽  
Strong Scaling ◽  
Left And Right ◽  
Shape Complexity ◽  
High Degree ◽  
Dissection Index

The leaves of vines exhibit a high degree of variability in shape, from simple oval to highly dissected palmatifid leaves. However, little is known about the extent of leaf bilateral symmetry in vines, how leaf perimeter scales with leaf surface area, and how this relationship depends on leaf shape. We studied 15 species of vines and calculated (i) the areal ratio (AR) of both sides of the lamina per leaf, (ii) the standardized symmetry index (SI) to estimate the deviation from leaf bilateral symmetry, and (iii) the dissection index (DI) to measure leaf-shape complexity. In addition, we examined whether there is a scaling relationship between leaf perimeter and area for each species. A total of 14 out of 15 species had no significant differences in average ln(AR), and mean ln(AR) approximated zero, indicating that the areas of the two lamina sides tended to be equal. Nevertheless, SI values among the 15 species had significant differences. A statistically strong scaling relationship between leaf perimeter and area was observed for each species, and the scaling exponents of 12 out of 15 species fell in the range of 0.49−0.55. These data show that vines tend to generate a similar number of left- and right-skewed leaves, which might contribute to optimizing light interception. Weaker scaling relationships between leaf perimeter and area were associated with a greater DI and a greater variation in DI. Thus, DI provides a useful measure of the degree of the complexity of leaf outline.

Advantages of Complementary Stereo Images as Viewed with the Low-Temperature Field-Emission SEM

1992 ◽  
Vol 50 (2) ◽  
pp. 1314-1315
Author(s):  
William P. Wergin ◽  
Eric F. Erbe
Keyword(s):  
Fold Increase ◽  
Horizontal Displacement ◽  
Three Dimensions ◽  
Stereo Image ◽  
Stereo Pair ◽  
Sem Micrograph ◽  
Left And Right ◽  
The Common ◽  
The Brain ◽  
Pair Analysis

The eye-brain complex allows those of us with normal vision to perceive and evaluate our surroundings in three-dimensions (3-D). The principle factor that makes this possible is parallax - the horizontal displacement of objects that results from the independent views that the left and right eyes detect and simultaneously transmit to the brain for superimposition. The common SEM micrograph is a 2-D representation of a 3-D specimen. Depriving the brain of the 3-D view can lead to erroneous conclusions about the relative sizes, positions and convergence of structures within a specimen. In addition, Walter has suggested that the stereo image contains information equivalent to a two-fold increase in magnification over that found in a 2-D image. Because of these factors, stereo pair analysis should be routinely employed when studying specimens.Imaging complementary faces of a fractured specimen is a second method by which the topography of a specimen can be more accurately evaluated.

scholarly journals An architectonic type principle in the development of laminar patterns of cortico-cortical connections

2021 ◽  
Author(s):  
Sarah F. Beul ◽  
Alexandros Goulas ◽  
Claus C. Hilgetag
Keyword(s):  
Structural Connectivity ◽  
Macaque Monkey ◽  
Brain Regions ◽  
Adult Brain ◽  
Mammalian Brain ◽  
Cortical Connections ◽  
Cortical Projections ◽  
Structural Connections ◽  
High Degree ◽  
The Brain

AbstractStructural connections between cortical areas form an intricate network with a high degree of specificity. Many aspects of this complex network organization in the adult mammalian cortex are captured by an architectonic type principle, which relates structural connections to the architectonic differentiation of brain regions. In particular, the laminar patterns of projection origins are a prominent feature of structural connections that varies in a graded manner with the relative architectonic differentiation of connected areas in the adult brain. Here we show that the architectonic type principle is already apparent for the laminar origins of cortico-cortical projections in the immature cortex of the macaque monkey. We find that prenatal and neonatal laminar patterns correlate with cortical architectonic differentiation, and that the relation of laminar patterns to architectonic differences between connected areas is not substantially altered by the complete loss of visual input. Moreover, we find that the degree of change in laminar patterns that projections undergo during development varies in proportion to the relative architectonic differentiation of the connected areas. Hence, it appears that initial biases in laminar projection patterns become progressively strengthened by later developmental processes. These findings suggest that early neurogenetic processes during the formation of the brain are sufficient to establish the characteristic laminar projection patterns. This conclusion is in line with previously suggested mechanistic explanations underlying the emergence of the architectonic type principle and provides further constraints for exploring the fundamental factors that shape structural connectivity in the mammalian brain.

scholarly journals The Hammer and the Nail: Biomechanics of Striking and Struck Canadian University Football Players

2021 ◽  
Author(s):  
Jeffrey S. Brooks ◽  
Adam Redgrift ◽  
Allen A. Champagne ◽  
James P. Dickey
Keyword(s):  
College Football ◽  
Head Impact ◽  
Football Players ◽  
Video Footage ◽  
Impact Location ◽  
Rule Changes ◽  
Left And Right ◽  
The Brain

AbstractThis study sought to evaluate head accelerations in both players involved in a football collision. Players on two opposing Canadian university teams were equipped with helmet mounted sensors during one game per season, for two consecutive seasons. A total of 276 collisions between 58 instrumented players were identified via video and cross-referenced with sensor timestamps. Player involvement (striking and struck), impact type (block or tackle), head impact location (front, back, left and right), and play type were recorded from video footage. While struck players did not experience significantly different linear or rotational accelerations between any play types, striking players had the highest linear and rotational head accelerations during kickoff plays (p ≤ .03). Striking players also experienced greater linear and rotational head accelerations than struck players during kickoff plays (p = .001). However, struck players experienced greater linear and rotational accelerations than striking players during kick return plays (p ≤ .008). Other studies have established that the more severe the head impact, the greater risk for injury to the brain. This paper’s results highlight that kickoff play rule changes, as implemented in American college football, would decrease head impact exposure of Canadian university football athletes and make the game safer.

The human brain: Chairman’s introduction

1981 ◽  
Vol 292 (1057) ◽  
pp. 151-153
Keyword(s):  
Human Brain ◽  
Cultural Evolution ◽  
Positive Feedback ◽  
Time Scale ◽  
Biological Evolution ◽  
Internal Models ◽  
Adaptive Behaviour ◽  
Myelin Sheaths ◽  
The Brain

Much has been said at the symposium about the pre-eminent role of the brain in the continuing emergence of man. Tobias has spoken of its explosive enlargement during the last 1 Ma, and how much of its enlargement in individual ontogeny is postnatal. We are born before our brains are fully grown and ‘wired up ’. During our long adolescence we build up internal models of the outside world and of the relations of parts of our bodies to it and to one another. Neurons that are present at birth spread their dendrites and project axons which acquire their myelin sheaths, and establish innumerable contacts with other neurons, over the years. New connections are formed; genetically endowed ones are stamped in or blanked off. People born without arms may grow up to use their toes in skills that are normally manual. Tobias, Darlington and others have stressed the enormous survival value of adaptive behaviour and the ‘positive feedback’ relation between biological and cultural evolution. The latter, the unique product of the unprecedentedly rapid biological evolution of big brains, advances on a time scale unknown to biological evolution.

scholarly journals The emulation theory of representation: Motor control, imagery, and perception

2004 ◽  
Vol 27 (3) ◽  
pp. 377-396 ◽  
Author(s):  
Rick Grush
Keyword(s):  
Motor Control ◽  
Sensory Feedback ◽  
Sensory Input ◽  
Neural Circuits ◽  
Sensory Information ◽  
The Body ◽  
Feedback Delay ◽  
Run Off ◽  
Effects Of Feedback ◽  
The Brain

The emulation theory of representation is developed and explored as a framework that can revealingly synthesize a wide variety of representational functions of the brain. The framework is based on constructs from control theory (forward models) and signal processing (Kalman filters). The idea is that in addition to simply engaging with the body and environment, the brain constructs neural circuits that act as models of the body and environment. During overt sensorimotor engagement, these models are driven by efference copies in parallel with the body and environment, in order to provide expectations of the sensory feedback, and to enhance and process sensory information. These models can also be run off-line in order to produce imagery, estimate outcomes of different actions, and evaluate and develop motor plans. The framework is initially developed within the context of motor control, where it has been shown that inner models running in parallel with the body can reduce the effects of feedback delay problems. The same mechanisms can account for motor imagery as the off-line driving of the emulator via efference copies. The framework is extended to account for visual imagery as the off-line driving of an emulator of the motor-visual loop. I also show how such systems can provide for amodal spatial imagery. Perception, including visual perception, results from such models being used to form expectations of, and to interpret, sensory input. I close by briefly outlining other cognitive functions that might also be synthesized within this framework, including reasoning, theory of mind phenomena, and language.

scholarly journals The Informational Underload (Sensory Deprivation) Model in Contemporary Psychiatry

1967 ◽  
Vol 12 (2) ◽  
pp. 105-124
Author(s):  
Peter Brawley ◽  
Robert Pos
Keyword(s):  
Sensory Input ◽  
Genetic Factors ◽  
Sensory Deprivation ◽  
Critical Factor ◽  
Good Evidence ◽  
Psychotic Experience ◽  
Common Pathway ◽  
The Central Nervous System ◽  
Deprivation Model ◽  
The Brain

To summarize briefly: Converging data from many disciplines — psychology, psychiatry, social theory, biochemistry, neuropharmacology, neurophysiology — point to the sensory input regulating mechanism of the central nervous system as a critical factor in the production of hallucinoses and psychotic experience. There is good evidence that what we have called the informational underload model ‘holds considerable promise for improving our understanding of many clinical and non-clinical phenomena of interest to psychiatry. The evidence suggests that a neurophysiological, internal informational underload syndrome may be a final common pathway of psychotic experience. The question as to where such a syndrome might occur in the brain, together with the question of whether such an informational underload syndrome might be due to toxins, genetic factors, conditioning processes, anxiety or dissociation, or other causes, has to be left open. What is needed now, is research directed at these two questions: 1) does such an internal informational underload syndrome occur in the brain, 2) when, where, and under what circumstances does it occur?

The matter of the stick: Storying/(re)storying children’s literacies in the forest

2017 ◽  
Vol 17 (3) ◽  
pp. 336-352 ◽  
Author(s):  
Debra Harwood ◽  
Diane R Collier
Keyword(s):  
Teaching And Learning ◽  
Research Study ◽  
Natural World ◽  
Data Generation ◽  
Children's Play ◽  
Literacy Teaching ◽  
Children’S Play ◽  
Human World ◽  
Forest Schools ◽  
Matter Energy

Children's intra-actions with the natural world offer an important lens to revisit notions of literacies. They allow for a decentring of humans – here children – as actors. Also, forest schools and nature-based learning programmes are increasingly erupting across North America, although more commonplace in Europe for a longer period. In this presentation of our research, we feature a storying/(re)storying of data from a yearlong research study of children's entanglements with the forest as a more-than-human world. We ask what we might learn if educators, children and researchers think with sticks, not separate from, but in relation to sticks? Eight preschool children, two educators and two researchers ventured into the forest twice a week over the course of a year, documenting their interactions with a mosaic of data generation tools, such as notebooks, iPads, Go-Pro cameras. The forest offered diverse materials that provoked “thing-matter-energy- child-assemblages” that were significant for the children's play and literacy framing. Through post-humanist theorizing, we have paid particular attention to the stick within the children's forest play and illustrate the ways in which the stick was entangled with children’s bodies, relations, identities and discourses. The stick was a catalyst, a friend, a momentary and changing text, an agentic force acting relationally with children's play and stories. The post humanism storying/(re)storying of the children's encounters in the forest with sticks invites infinite possibilities for literacy teaching and learning. How might educators foster such relations, enquiring with and alongside children with an openness toward what the sticks (forests) might teach us?

scholarly journals Sequence memory in recurrent neuronal network can develop without structured input

2020 ◽  
Author(s):  
Matthias Loidolt ◽  
Lucas Rudelt ◽  
Viola Priesemann
Keyword(s):  
Sensory Input ◽  
Building Blocks ◽  
Spike Timing ◽  
Synaptic Competition ◽  
Structured Input ◽  
Recurrent Neuronal Network ◽  
Sequence Memory ◽  
The Brain ◽  
Specific Sequences ◽  
Intrinsic Feature

AbstractHow does spontaneous activity during development prepare cortico-cortical connections for sensory input? We here analyse the development of sequence memory, an intrinsic feature of recurrent networks that supports temporal perception. We use a recurrent neural network model with homeostatic and spike-timing-dependent plasticity (STDP). This model has been shown to learn specific sequences from structured input. We show that development even under unstructured input increases unspecific sequence memory. Moreover, networks “pre-shaped” by such unstructured input subsequently learn specific sequences faster. The key structural substrate is the emergence of strong and directed synapses due to STDP and synaptic competition. These construct self-amplifying preferential paths of activity, which can quickly encode new input sequences. Our results suggest that memory traces are not printed on a tabula rasa, but instead harness building blocks already present in the brain.

scholarly journals Loving Nature in João Guimarães Rosa: The Non-human as 'amável'

2020 ◽  
Vol 5 (2) ◽  
pp. 55-74
Author(s):  
Ashley Brock
Keyword(s):  
Present Article ◽  
Natural World ◽  
Critical Discourse ◽  
Political Debates ◽  
Emotional Relationships ◽  
Joao Guimaraes Rosa ◽  
Human World ◽  
Human Capacity ◽  
A Site ◽  
The Cost

In the present article, I locate an implicit environmentalism JoãoGuimarães Rosa’s writing from the 1950s and 1960s. This sensibility is easy tomiss, in part because it transposes political debates on damage inflicted in thename of development and progress onto the affective-ethical plane; however, itdoes so in a way that resists sentimentality or projecting a misplaced innocenceonto the non-human world. Focusing on emotional relationships between humansand non-humans, I read “As margens da alegria” and “Os cimos” as expressingan eco-critical discourse that was already latent in Grande sertão: veredas.Recasting the natural world as a site of both unfathomable otherness and relationsof tenderness, Guimarães Rosa presents the emotional hold that nature has onhumans and the cost of cleaving oneself from it—a cost that includes diminishingthe human capacity for delight, wonder, and eros.

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