Functional Clusters of Neurons in Layer 6 of Macaque V1.

Layer 6 appears to perform a very important role in the function of macaque primary visual cortex, V1, but not enough is understood about the functional characteristics of neurons in the layer 6 population. It is unclear to what extent the population is homogeneous with respect to their visual properties or if one can identify distinct subpopulations. Here we performed a cluster analysis based on measurements of the responses of single neurons in layer 6 of primary visual cortex in male macaque monkeys (Macaca fascicularis) to achromatic grating stimuli that varied in orientation, direction of motion, spatial and temporal frequency, and contrast. The visual stimuli were presented in a stimulus window that was also varied in size. Using the responses to parametric variation in these stimulus variables, we extracted a number of tuning response measures and used them in the cluster analysis. Six main clusters emerged along with some smaller clusters. Additionally, we asked whether parameter distributions from each of the clusters were statistically different. There were clear separations of parameters between some of the clusters, particularly for f1/f0 ratio, direction selectivity, and temporal frequency bandwidth, but other dimensions also showed differences between clusters. Our data suggest that in layer 6 there are multiple parallel circuits that provide information about different aspects of the visual stimulus.SIGNIFICANCE STATEMENT The cortex is multilayered and is involved in many high-level computations. In the current study, we have asked whether there are subpopulations of neurons, clusters, in layer 6 of cortex with different functional tuning properties that provide information about different aspects of the visual image. We identified six major functional clusters within layer 6. These findings show that there is much more complexity to the circuits in cortex than previously demonstrated and open up a new avenue for experimental investigation within layers of other cortical areas and for the elaboration of models of circuit function that incorporate many parallel pathways with different functional roles.

Hardware and software improvements to a low-cost horizontal parallax holographic video monitor.

Displays capable of true holographic video have been prohibitively expensive and difficult to build. With this paper, we present a suite of modularized hardware components and software tools needed to build a HoloMonitor with basic "hacker-space" equipment, highlighting improvements that have enabled the total materials cost to fall to $820, well below that of other holographic displays. It is our hope that the current level of simplicity, development, design flexibility, and documentation will enable the lay engineer, programmer, and scientist to relatively easily replicate, modify, and build upon our designs, bringing true holographic video to the masses.

Hardware and software improvements to a low-cost horizontal parallax holographic video monitor: publisher's note.

This publisher's note corrects a trademark concern in Appl. Opt.57, A122 (2018)APOPAI0003-693510.1364/AO.57.00A122.

Backside emission leaky-mode modulators.

We report on an advancement to leaky-mode modulators that allows for backside emission from the device. This is accomplished by adding a high spatial frequency surface relief grating (~300 nm period) to the backside of the modulator. The outcome being a theoretical arbitrary increase in usable output aperture, at the cost of angular deflection. Using backside emission, it is now possible for leaky mode modulators to be used to create transparent, holographic, direct-view near-eye displays.

Characterization of Anisotropic Leaky Mode Modulators for Holovideo.

Holovideo displays are based on light-bending spatial light modulators. One such spatial light modulator is the anisotropic leaky mode modulator. This modulator is particularly well suited for holographic video experimentation as it is relatively simple and inexpensive to fabricate. Some additional advantages of leaky mode devices include: large aggregate bandwidth, polarization separation of signal light from noise, large angular deflection and frequency control of color. In order to realize these advantages, it is necessary to be able to adequately characterize these devices as their operation is strongly dependent on waveguide and transducer parameters. To characterize the modulators, the authors use a commercial prism coupler as well as a custom characterization apparatus to identify guided modes, calculate waveguide thickness and finally to map the device's frequency input and angular output of leaky mode modulators. This work gives a detailed description of the measurement and characterization of leaky mode modulators suitable for full-color holographic video.