The electroretinogram (ERG) of anaesthetised dark‐adapted macaque monkeys was recorded in response to ganzfeld stimulation and rod‐ and cone‐driven receptoral and postreceptoral components were separated and modelled. The test stimuli were brief (< 4.1 ms) flashes. The cone‐driven component was isolated by delivering the stimulus shortly after a rod‐saturating background had been extinguished. The rod‐driven component was derived by subtracting the cone‐driven component from the mixed rod–cone ERG. The initial part of the leading edge of the rod‐driven a‐wave scaled linearly with stimulus energy when energy was sufficiently low and, for times less than about 12 ms after the stimulus, it was well described by a linear model incorporating a distributed delay and three cascaded low‐pass filter elements. Addition of a simple static saturating non‐linearity with a characteristic intermediate between a hyperbolic and an exponential function was sufficient to extend application of the model to most of the leading edge of the saturated responses to high energy stimuli. It was not necessary to assume involvement of any other non‐linearity or that any significant low‐pass filter followed the non‐linear stage of the model. A negative inner‐retinal component contributed to the later part of the rod‐driven a‐wave. After suppressing this component by blocking ionotropic glutamate receptors, the entire a‐wave up to the time of the first zero‐crossing scaled with stimulus energy and was well described by summing the response of the rod model with that of a model describing the leading edge of the rod‐bipolar cell response. The negative inner‐retinal component essentially cancelled the early part of the rod‐bipolar cell component and, for stimuli of moderate energy, made it appear that the photoreceptor current was the only significant component of the leading edge of the a‐wave. The leading edge of the cone‐driven a‐wave included a slow phase that continued up to the peak, and was reduced in amplitude either by a rod‐suppressing background or by the glutamate analogue, cis‐piperidine‐2,3‐dicarboxylic acid (PDA). Thus the slow phase represents a postreceptoral component present in addition to a fast component of the a‐wave generated by the cones themselves. At high stimulus energies, it appeared less than 5 ms after the stimulus. The leading edge of the cone‐driven a‐wave was adequately modelled as the sum of the output of a cone photoreceptor model similar to that for rods and a postreceptoral signal obtained by a single integration of the cone output. In addition, the output of the static non‐linear stage in the cone model was subject to a low‐pass filter with a time constant of no more than 1 ms. In conclusion, postreceptoral components must be taken into account when interpreting the leading edge of the rod‐ and cone‐driven a‐waves of the dark‐adapted ERG.

Multimedia content analysis is applied in different real-world computer vision applications, and digital images constitute a major part of multimedia data. In last few years, the complexity of multimedia contents, especially the images, has grown exponentially, and on daily basis, more than millions of images are uploaded at different archives such as Twitter, Facebook, and Instagram. To search for a relevant image from an archive is a challenging research problem for computer vision research community. Most of the search engines retrieve images on the basis of traditional text-based approaches that rely on captions and metadata. In the last two decades, extensive research is reported for content-based image retrieval (CBIR), image classification, and analysis. In CBIR and image classification-based models, high-level image visuals are represented in the form of feature vectors that consists of numerical values. The research shows that there is a significant gap between image feature representation and human visual understanding. Due to this reason, the research presented in this area is focused to reduce the semantic gap between the image feature representation and human visual understanding. In this paper, we aim to present a comprehensive review of the recent development in the area of CBIR and image representation. We analyzed the main aspects of various image retrieval and image representation models from low-level feature extraction to recent semantic deep-learning approaches. The important concepts and major research studies based on CBIR and image representation are discussed in detail, and future research directions are concluded to inspire further research in this area.

To assess the contribution of spiking inner retinal neurons to the multifocal electroretinogram (ERG), recordings were made from four monkeys (Macaca mulatta) before and after intravitreal injections of tetrodotoxin (TTX). TTX blocks all sodium-based action potentials and thus terminates spiking activity of amacrine and ganglion cells. TTX eliminated a large component from the control responses, and this TTX-sensitive component was present as early as 10 ms after the stimulus. Before injection with TTX, the 103 focal ERG responses varied in waveform across the retina. After TTX, the response waveforms were largely independent of retinal position, indicating that it was primarily the TTX-sensitive component of the control response that was dependent upon retinal location. Given that retinal ganglion cells compose a sizable proportion of the retinal elements that produce action potentials, it is likely that part of the TTX-sensitive component is due to the spiking activity of these cells. Further, the systematic change in waveform of the TTX-sensitive component with distance from the optic nerve head suggests that part of the TTX-sensitive component may originate from the activity of the ganglion cell axons. Based on these findings, there is reason to be optimistic that the multifocal technique can be employed to study the effects of glaucoma and other diseases that affect the inner retina.

Contributions to the multifocal electroretinogram (ERG) from the inner retina (i.e. ganglion and amacrine cells) were identified by recording from monkeys before and after intravitreal injections of n-methyl DL aspartate (NMDLA) and/or tetrodotoxin (TTX). Components similar in waveform to those removed by the drugs were identified in the human multifocal ERG if the stimulus contrast was set at 50% rather than the typically employed 100% contrast. These components were found to be missing or diminished in the records from some patients with glaucoma and diabetes, diseases which affect the inner retina.

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