The interconnections between neurons in V1 and MT.

<p>The interconnections represented by red (excitatory) and blue (inhibitory) arrows, respectively. Integration neurons receive inputs from both sets of complex and end-stopped cells in V1. They also receive inhibitory connections from segmentation cells. Segmentation cells receive excitatory input from complex cells and are inhibited by end-stopped cells. They also receive a conditional inhibitory connection from integration cells when the neurons in the receptive field center and surround are active. The connection parameters and variables are explained in the text and in Tables <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0164813#pone.0164813.t001" target="_blank">1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0164813#pone.0164813.t002" target="_blank">2</a>.</p

The responses of model end-stopped neurons in V1 (plotted using the same format as in Fig 6).

<p>The neurons at the end-points of the bar have much stronger activity compared to neurons along the edge. In this case, the input stimulus is a bar moving to the right, so neurons at the terminators selective to this direction have higher activity. As a result of lateral inhibition between neurons in V1, the activities of the neurons along the bar are suppressed.</p

A schematic explanation of the aperture problem.

<p>The bar is moving to the right. The component of motion that is parallel to the edge of the bar is not visible in the upper aperture because there is no change in the contrast in this direction. Therefore, it seems that the bar is moving in a direction that is perpendicular to the edge of the bar (arrow labeled “visible”). The correct direction of motion can be estimated when the end-points of the bar are seen through an aperture as shown in the lower aperture.</p

The activity levels of segmentation neurons for a stimulus moving to the right (plotted in the same format as Fig 6).

<p>As expected, these neurons have a high level of activity at the discontinuities of the input image.</p

Schematic diagram of interconnections between neurons in MT.

<p>Nodes with the same color are neurons selective to the same direction. Neurons in columns have the same spatial location but different direction selectivity. A) Red arrows indicate the excitatory connections from neighboring integration neurons with the same directional preference. Neurons receive excitatory inputs from nearby integration neurons and neurons in the surround. B) A schematic diagram of inhibition from distant neighboring neurons selective to different directions. Solid blue arrows represent these long-range inhibitory connections. In addition, integration neurons receive inter-directional inhibition from neurons selective to different directions at the same spatial location; the dotted blue arrows represent these interconnections. C) The inter-connection between integration and segmentation neurons in MT. Segmentation neurons receive excitatory connections from integration neurons with different directional preferences at the same spatial location. They also receive inhibition from segmentation cells when motion in the center and surround of the receptive field of a cell is in the same direction.</p

Activity of V1 neurons and MT integration and segmentation neurons in response to a bar moving to the right.

<p>The spatiotemporal location of the bar is indicated by (1), (2), (3)… A) The activity of the complex V1 neuron selective to rightward motion at the terminator (blue), the activity of a complex V1 neuron selective for downward-right motion along the bar (green), the activity of an end-stopped neuron selective to rightward motion at the terminator (red), and the activity of an end-stopped neuron selective to downward-right motion along the bar (black). B) The activity of an integration neuron (blue) and a segmentation neuron (green), both selective to rightward motion and located at the terminator. C) The activity of an integration neuron (blue) and a segmentation neuron (green) selective to the rightward-down direction located at the middle of the bar. D) The activity of an integration neuron (blue) and a segmentation neurons (green) selective to rightward-down motion located at the middle of the bar (green).</p

The activity of model V1 complex neurons.

<p>Each graph shows the activity of the V1 complex neurons selective to the direction shown by the colored arrow. The angle of each arrow also indicates its direction. The axes represent the location and the gray scale intensity indicates the level of activity. Neurons at the edges have higher activity compared to neurons at the terminators, which have unambiguous motion signals. The cartoon in the middle summarizes the results shown in eight graphs. The colored section of the bar shows neurons selective to the directions that have the highest levels of activity at those locations. For a bar moving towards the right, the terminators, indicated by the purple color, show the correct direction of motion; the colors of the edges represent the directions that are incorrect because of the aperture problem.</p

The average error of the integration neurons in the network to correctly classify the direction of motion with different levels of neural noise.

<p>The represented error is the average of the measured values of the error after 10 experiments and the error bars indicate standard error of the mean. An error of 0 represents an accurate estimation of motion by a majority of the MT neurons while an error of 1 indicates that the majority winning MT neurons have wrong estimates of the direction of motion, measured in a region within three pixels of the edges of the moving bar in one frame of the motion.</p

Illustration of lateral inhibition in integration and segmentation neurons.

<p>A) The area from which an integration neuron, denoted in yellow, receives long range inhibition is represented by blue squares. B) The spatial extent of the surround of the receptive fields of MT neurons covers around nine pixels of the input stimulus. The area from which the segmentation neuron receives surround suppression is the outside of the border represented by the dashed line. The receptive field of the neuron is modelled as a Gaussian filter in which the amplitude decreases gradually from the center of the receptive field, with the yellow color representing the highest value. C) The circle shows the excitatory receptive field of a segmentation MT neuron and its surround area. According to experimental data, when motion in the center and surround of the neuron are in the same direction, the response of the segmentation cell is suppressed. D) Illustration of the effect of surround suppression, where increasing the size of the input stimulus, such that the center and surround are stimulated simultaneously, the activity of a segmentation MT neuron experiences a suppression of its response.</p

The constant parameters used in the model, their values, and their units.

<p>The constant parameters used in the model, their values, and their units.</p