scholarly journals Direction of Movement of Glacially Transported Boulders Not Necessarily Shown By Preserved Ice Movement Direction Indicators, Baker Lake, District of Keewatin

1981 ◽  
Author(s):  
M Schau
Keyword(s):  
Movement Direction ◽  
Lake District ◽  
Direction Of Movement ◽  
Baker Lake

Changes in motor cortex activity during reaching movements with similar hand paths but different arm postures

1995 ◽  
Vol 73 (6) ◽  
pp. 2563-2567 ◽  
Author(s):  
S. H. Scott ◽  
J. F. Kalaska
Keyword(s):  
Motor Cortex ◽  
Sagittal Plane ◽  
Single Cells ◽  
Reaching Movements ◽  
Movement Direction ◽  
Tonic Activity ◽  
Population Vector ◽  
Significant Difference ◽  
Direction Of Movement ◽  
Kinematics And Kinetics

1. Neuronal activity was recorded in the motor cortex of a monkey that performed reaching movements with the use of two different arm postures. In the first posture (control), the monkey used its natural arm orientation, approximately in the sagittal plane. In the second posture (abducted), the monkey had to adduct its elbow nearly to shoulder level to grasp the handle. The path of the hand between targets was similar in both arm postures, but the joint kinematics and kinetics were different. 2. In both postures, the activity of single cells was often broadly tuned with movement direction and static arm posture over the targets. In a large proportion of cells, either the level of tonic activity, the directional tuning, or both, varied between the two postures during the movement and target hold periods. 3. For most directions of movement, there was a statistically significant difference in the direction of the population vector for the two arm postures. Furthermore, whereas the population vector tended to point in the direction of movement for the control posture, there was a poorer correspondence between the direction of movement and the population vector for the abducted posture. These observed changes are inconsistent with the notion that the motor cortex encodes purely hand trajectory in space.

scholarly journals Local interactions and their group-level consequences in flocking jackdaws

2019 ◽  
Vol 286 (1906) ◽  
pp. 20190865 ◽  
Author(s):  
Hangjian Ling ◽  
Guillam E. Mclvor ◽  
Kasper van der Vaart ◽  
Richard T. Vaughan ◽  
Alex Thornton ◽  
...  
Keyword(s):  
Group Structure ◽  
Three Dimensional ◽  
Movement Direction ◽  
Gravitational Potential Energy ◽  
Wingbeat Frequency ◽  
Local Interactions ◽  
Interaction Forces ◽  
Short Range Repulsion ◽  
Direction Of Movement ◽  
Repulsive Forces

As one of nature's most striking examples of collective behaviour, bird flocks have attracted extensive research. However, we still lack an understanding of the attractive and repulsive forces that govern interactions between individuals within flocks and how these forces influence neighbours' relative positions and ultimately determine the shape of flocks. We address these issues by analysing the three-dimensional movements of wild jackdaws ( Corvus monedula ) in flocks containing 2–338 individuals. We quantify the social interaction forces in large, airborne flocks and find that these forces are highly anisotropic. The long-range attraction in the direction perpendicular to the movement direction is stronger than that along it, and the short-range repulsion is generated mainly by turning rather than changing speed. We explain this phenomenon by considering wingbeat frequency and the change in kinetic and gravitational potential energy during flight, and find that changing the direction of movement is less energetically costly than adjusting speed for birds. Furthermore, our data show that collision avoidance by turning can alter local neighbour distributions and ultimately change the group shape. Our results illustrate the macroscopic consequences of anisotropic interaction forces in bird flocks, and help to draw links between group structure, local interactions and the biophysics of animal locomotion.

Dynamical Organization of Directional Tuning in the Primate Premotor and Primary Motor Cortex

2003 ◽  
Vol 89 (2) ◽  
pp. 1136-1142 ◽  
Author(s):  
Yoram Ben-Shaul ◽  
Eran Stark ◽  
Itay Asher ◽  
Rotem Drori ◽  
Zoltan Nadasdy ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Primary Motor Cortex ◽  
Hand Movement ◽  
Movement Direction ◽  
Cortical Surface ◽  
Preferred Direction ◽  
Preparation Period ◽  
Direction Of Movement ◽  
The Mean ◽  
Movement Parameters

Although previous studies have shown that activity of neurons in the motor cortex is related to various movement parameters, including the direction of movement, the spatial pattern by which these parameters are represented is still unresolved. The current work was designed to study the pattern of representation of the preferred direction (PD) of hand movement over the cortical surface. By studying pairwise PD differences, and by applying a novel implementation of the circular variance during preparation and movement periods in the context of a center-out task, we demonstrate a nonrandom distribution of PDs over the premotor and motor cortical surface of two monkeys. Our analysis shows that, whereas PDs of units recorded by nonadjacent electrodes are not more similar than expected by chance, PDs of units recorded by adjacent electrodes are. PDs of units recorded by a single electrode display the greatest similarity. Comparison of PD distributions during preparation and movement reveals that PDs of nearby units tend to be more similar during the preparation period. However, even for pairs of units recorded by a single electrode, the mean PD difference is typically large (45° and 75° during preparation and movement, respectively), so that a strictly modular representation of hand movement direction over the cortical surface is not supported by our data.

scholarly journals Coding movement direction by burst firing in electrosensory neurons

2011 ◽  
Vol 106 (4) ◽  
pp. 1954-1968 ◽  
Author(s):  
Navid Khosravi-Hashemi ◽  
Eric S. Fortune ◽  
Maurice J. Chacron
Keyword(s):  
Spike Train ◽  
Afferent Input ◽  
Direction Selectivity ◽  
Burst Firing ◽  
Weakly Electric Fish ◽  
Movement Direction ◽  
Directional Bias ◽  
Threshold Criterion ◽  
Direction Of Movement

Directional selectivity, in which neurons respond strongly to an object moving in a given direction (“preferred”) but respond weakly or not at all to an object moving in the opposite direction (“null”), is a critical computation achieved in brain circuits. Previous measures of direction selectivity have compared the numbers of action potentials elicited by each direction of movement, but most sensory neurons display patterning, such as bursting, in their spike trains. To examine the contribution of patterned responses to direction selectivity, we recorded from midbrain neurons in weakly electric fish and found that most neurons responded with a combination of both bursts and isolated spikes to moving object stimuli. In these neurons, we separated bursts and isolated spikes using an interspike interval (ISI) threshold. The directional bias of bursts was significantly higher than that of either the full spike train or the isolated spike train. To examine the encoding and decoding of bursts, we built biologically plausible models that examine 1) the upstream mechanisms that generate these spiking patterns and 2) downstream decoders of bursts. Our model of upstream mechanisms uses an interaction between afferent input and subthreshold calcium channels to give rise to burst firing that occurs preferentially for one direction of movement. We tested this model in vivo by application of calcium antagonists, which reduced burst firing and eliminated the differences in direction selectivity between bursts, isolated spikes, and the full spike train. Our model of downstream decoders used strong synaptic facilitation to achieve qualitatively similar results to those obtained using the ISI threshold criterion. This model shows that direction selective information carried by bursts can be decoded by downstream neurons using biophysically plausible mechanisms.

scholarly journals The Determination of the Direction of Movement on Glacier Surfaces by Terrestrial Photogrammetry

1966 ◽  
Vol 6 (45) ◽  
pp. 359-367 ◽  
Author(s):  
Ulrich Voigt
Keyword(s):  
Present Method ◽  
Movement Direction ◽  
Base Line ◽  
Line System ◽  
Direction Of Movement ◽  
Longitudinal Profiles ◽  
Terrestrial Photogrammetry

In order to determine longitudinal profiles of movement on glacier surfaces from photogrammetric surveys, it is necessary to know the direction of movement. The present method requires at least two base lines with overlapping ranges of photographs. The establishment of a base-line system for a given glacier form depends on the demands of accuracy. The method is applied to the movement of the glacier Kongsvegen (Vestspitsbergen) and the accuracy obtained is discussed. The movement direction of the points on the medial moraine of Kongsvegen does not coincide with the moraine direction.

scholarly journals The Determination of the Direction of Movement on Glacier Surfaces by Terrestrial Photogrammetry

1966 ◽  
Vol 6 (45) ◽  
pp. 359-367 ◽  
Author(s):  
Ulrich Voigt
Keyword(s):  
Present Method ◽  
Movement Direction ◽  
Base Line ◽  
Line System ◽  
Direction Of Movement ◽  
Longitudinal Profiles ◽  
Terrestrial Photogrammetry

In order to determine longitudinal profiles of movement on glacier surfaces from photogrammetric surveys, it is necessary to know the direction of movement. The present method requires at least two base lines with overlapping ranges of photographs. The establishment of a base-line system for a given glacier form depends on the demands of accuracy. The method is applied to the movement of the glacier Kongsvegen (Vestspitsbergen) and the accuracy obtained is discussed. The movement direction of the points on the medial moraine of Kongsvegen does not coincide with the moraine direction.

Rocker Switch Tactile Coding and Direction of Motion Stereotypes

1985 ◽  
Vol 29 (5) ◽  
pp. 437-441 ◽  
Author(s):  
Daniel D. Jack
Keyword(s):  
Movement Direction ◽  
Passenger Compartment ◽  
Coding Schemes ◽  
Initial Control ◽  
Direction Of Movement

This paper presents the results of a series of direction of motion stereotype studies which were conducted to determine how tactile switch coding influenced drivers' choices of initial control movement direction. First encounters with automotive rocker switches which had been mounted in various locations and orientations throughout the passenger compartment were evaluated. Motion stereotypes for these bi-directional switches were found to vary from chance levels (50% of drivers preferring either direction of movement) to a 99%/l% preference depending upon tactile coding schemes, switch orientations, labeling and switch locations.

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