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In JoVE (3)
- Whole-cell Recordings of Light Evoked Excitatory Synaptic Currents in the Retinal Slice
- Using the Horseshoe Crab, Limulus Polyphemus, in Vision Research
- Single-unit In vivo Recordings from the Optic Chiasm of Rat
Other Publications (10)
Articles by Christopher L. Passaglia in JoVE
JoVE General
Whole-cell Recordings of Light Evoked Excitatory Synaptic Currents in the Retinal Slice
1Program in Neuroscience, Boston University, 2Department of Biology, Boston University, 3Department of Biomedical Engineering, Boston University
This video shows the process of whole-cell voltage clamp recordings in the retinal slice of the aquatic tiger salamander. We demonstrate the preparation of the slice as well as how to perform patch clamp recordings during visual stimulation of the retina.
JoVE General
Using the Horseshoe Crab, Limulus Polyphemus, in Vision Research
Department of Biomedical Engineering, Boston University
In this video we perform electroretinogram recording, optic nerve recording, and intraretinal recording with the American horseshoe crab, Limulus Polyphemus. These electrophysiological paradigms can be used for investigating the neural basis of vision in a research or teaching lab.
JoVE Neuroscience
Single-unit In vivo Recordings from the Optic Chiasm of Rat
Department of Biomedical Engineering, Boston University
Retinal ganglion cells transmit visual information from the eye to the brain with sequences of action potentials. Here, we demonstrate how to record the action potentials of single ganglion cells in vivo from anesthetized rats.
Other articles by Christopher L. Passaglia on PubMed
Orientation Sensitivity of Ganglion Cells in Primate Retina
The two-dimensional shape of the receptive field center of macaque retinal ganglion cells was determined by measuring responses to drifting sinusoidal gratings of different spatial frequency and orientation. The responses of most cells to high spatial frequencies depended on grating orientation, indicating that their centers were not circularly symmetric. In general, center shape was well described by an ellipse. The major axis of the ellipse tended to point towards the fovea or perpendicular to this. Parvocellular pathway cells had greater center ellipticity than magnocellular pathway cells; the median ratio of the major-to-minor axis was 1.72 and 1.38, respectively. Parvocellular pathway cells also had centers that were often bimodal in shape, suggesting that they received patchy cone/bipolar cell input. We conclude that most ganglion cells in primate retina have elongated receptive field centers and thus show orientation sensitivity.
Information Transmission Rates of Cat Retinal Ganglion Cells
To assess the information encoded in retinal spike trains and how it might be decoded by recipient neurons in the brain, we recorded from individual cat X and Y ganglion cells and visually stimulated them with randomly modulated patterns of various contrast and spatial configuration. For each pattern, we estimated the information rate of the cells using linear or nonlinear algorithms and for some patterns by directly measuring response probability distributions. We show that ganglion cell spike trains contain information from the receptive field center and surround, that the center and surround have similar signaling capacity, that antagonism between the mechanisms reduces information transmission, and that the total information rate is limited. We also show that a linear decoding algorithm can capture all of the information available in retinal spike trains about weak inputs, but it misses a substantial amount about strong inputs. For the strongest stimulus we used, the information rate of the best linear decoder averaged 40-70 bits/s across ganglion cell types, while the directly measured rate was around 20-40 bits/s greater. This implies that under certain stimulus conditions, visual information is encoded in the temporal structure of retinal spike trains and that a nonlinear decoding algorithm is needed to extract the temporally coded information. Using simulated spike trains, we demonstrate that much of the temporal structure may be explained by the threshold for spike generation and is not necessarily indicative of a complex coding scheme.
Impact of Noise on Retinal Coding of Visual Signals
Neural noise introduces uncertainty about the signals encoded in neural spike trains. Because of the uncertainty neurons can reliably transmit a limited amount of information. This amount is difficult to quantify for neurons that combine signals and noise in a complex manner, as many trials would be needed to estimate the joint probability distribution of stimulus and neural response accurately. The task is experimentally tractable, however, for neurons that combine signals with additive Gaussian noise. For such neurons, the joint probability distribution is well defined and information transmission rates can be computed from estimates of signal-to-noise ratio. Here we use power spectral analysis to specify the contributions of signal and noise to retinal coding of visual information. We show that in the spike trains of cat ganglion cells noise power is minimal and constant at temporal frequencies from 0.3 to 20 Hz and that it increases at higher frequencies to a plateau level that generally depends on stimulus contrast. We also show that trial-to-trial fluctuations in noise amplitude at different frequencies are uncorrelated and normally distributed. Although the contrast dependence indicates that noise at high temporal frequencies contributes nonlinearly to ganglion cell spike trains, cells in the primary visual cortex are not known to respond to stimulus modulations >20 Hz. Hence, noise in the retinal output would appear additive, white, and Gaussian from their perspective. This greatly simplifies analysis of information transmission from the eye to the primary visual cortex and perhaps other regions of the brain.
Tono-Pen XL Calibration Curves for Cats, Cows and Sheep
The objective of this study was to provide calibration curves for correcting intraocular pressure (IOP) measurements obtained using the Tono-Pen XL tonometer in cats, cows and sheep. Twelve eyes from 9 cats, 13 eyes from 7 cows, 10 eyes from 5 sheep were used. The anterior chamber of the eye was cannulated in vivo, in situ (immediately post mortem) or ex vivo with a fine needle and IOP was varied from 10 to 90 mmHg in steps of 10 mmHg by adjusting the height of a saline reservoir connected to the needle. For each pressure setting, several readings of IOP were made using the tonometer. The relationship between Tono-Pen reading and manometer setting was linear over the full range of measurement. However, the slope of the data regression line deviated significantly from 1 and indicated that the instrument systematically underestimated IOP. For cats the average slope was 0.62 and for cows and sheep it was 0.72 and 0.69, respectively. For the latter animals, the regression line also had a nonzero intercept of approximately 4.5 mmHg. Similar results were obtained from in vivo and ex vivo eyes and with different Tono-Pen XL tonometers. Although developed for use on humans, the Tono-Pen XL can provide reproducible and accurate measurement of IOP in cats, cows and sheep when suitably calibrated by manometry. The calibration curves provided here, and by implication those reported for other animals using this tonometer, differ in slope from those measured with earlier models of the Tono-Pen. The reproducibility of the curves we obtained implies that they can be used to correct IOP readings from the Tono-Pen XL when manometry is not possible.
Complex Temporal Response Patterns with a Simple Retinal Circuit
The retina can respond to a wide array of features in the visual input. It was recently reported that the retina can even recognize complicated temporal input patterns and signal violations in the patterns. When a sequence of flashes was presented, ganglion cells exhibited a variety of firing profiles and many cells showed an "omitted stimulus response" (OSR), in which they fired strongly if a flash in the sequence was omitted. We examined the synaptic origins of the OSR by recording excitatory synaptic currents from ganglion cells in the salamander retina in response to periodic flash sequences. Consistent with previous spike recordings, ganglion cells exhibited an OSR in their current response and the OSR shifted in time with a change in flash frequency such that it could predict when the next flash should have occurred. Although the behavior may seem sophisticated, we show that a simple linear-nonlinear model with a spike threshold can account for the OSR in on ganglion cells and that the variety of complex firing profiles seen in other ganglion cells can be explained by adding contributions from the off pathway. We discuss the physiological and simulation results and their implications for understanding retinal mechanisms of visual information processing.
The Maintained Discharge of Rat Retinal Ganglion Cells
Action potentials were recorded from rat retinal ganglion cell fibers in the presence of a uniform field, and the maintained discharge pattern was characterized. Spike trains recorded under ketaminexylazine. The majority of cells had multimodal interval distributions, with the first peak in the range of 25.00.97). Both ON and OFF cells show serial correlations between adjacent interspike intervals, while ON cells also showed second-order correlations. Cells with multimodal interval distribution showed a strong peak at high frequencies in the power spectra in the range of 28.9-41.4 Hz. Oscillations were present under both anesthetic conditions and persisted in the dark at a slightly lower frequency, implying that the oscillations are generated independent of any light stimulus but can be modulated by light level. The oscillation frequency varied slightly between cells of the same type and in the same eye, suggesting that multiple oscillatory generating mechanisms exist within the retina. Cells with high-frequency oscillations were described well by an integrate-and-fire model with the input consisting of Gaussian noise plus a sinusoid where the phase was jittered randomly to account for the bandwidth present in the oscillations.
Effects of Remote Stimulation on the Modulated Activity of Cat Retinal Ganglion Cells
The output of retinal ganglion cells depends on local and global aspects of the visual scene. The local receptive field is well studied and classically consists of a linear excitatory center and a linear antagonistic surround. The global receptive field contains pools of nonlinear subunits that are distributed widely across the retina. The subunit pools mediate in uncertain ways various nonlinear behaviors of ganglion cells, like temporal-frequency doubling, saccadic suppression, and contrast adaptation. To clarify mechanisms of subunit function, we systematically examined the effect of remote grating patterns on the spike activity of cat X- and Y-type ganglion cells in vivo. We present evidence for two distinct subunit types based on spatiotemporal relationships between response nonlinearities elicited by remote drifting and contrast-reversing gratings. One subunit type is excitatory and activated by gratings of approximately 0.1 cycles per degree, while the other is inhibitory and activated by gratings of approximately 1 cycle per degree. The two subunit pools contribute to a global gain control mechanism that differentially modulates ganglion cell response dynamics, particularly for ON-center cells, where excitatory and inhibitory subunit stimulation respectively makes responses to antipreferred and preferred contrast steps more transient. We show that the excitatory subunits also have a profound influence on spatial tuning, turning cells from lowpass into bandpass filters. Based on difference-of-Gaussians model fits to tuning curves, we attribute the increased bandpass selectivity to changes in center-surround strength and relative phase and not center-surround size. A conceptual model of the extraclassical receptive field that could explain many observed phenomena is discussed.
Retinal Ganglion Cell Adaptation to Small Luminance Fluctuations
To accommodate the wide input range over which the visual system operates within the narrow output range of spiking neurons, the retina adjusts its sensitivity to the mean light level so that retinal ganglion cells can faithfully signal contrast, or relative deviations from the mean luminance. Given the large operating range of the visual system, the majority of work on luminance adaptation has involved logarithmic changes in light level. We report that luminance gain controls are recruited for remarkably small fluctuations in luminance as well. Using spike recordings from the rat optic tract, we show that ganglion cell responses to a brief flash of light are modulated in amplitude by local background fluctuations as little as 15% contrast. The time scale of the gain control is rapid (<125 ms), at least for on cells. The retinal locus of adaptation precedes the ganglion cell spike generator because response gain changes of on cells were uncorrelated with firing rate. The mechanism seems to reside within the inner retinal network and not in the photoreceptors, because the adaptation profiles of on and off cells differed markedly. The response gain changes follow Weber's law, suggesting that network mechanisms of luminance adaptation described in previous work modulates retinal ganglion cell sensitivity, not just when we move between different lighting environments, but also as our eyes scan a visual scene. Finally, we show that response amplitude is uniformly reduced for flashes on a modulated background that has spatial contrast, indicating that another gain control that integrates luminance signals nonlinearly over space operates within the receptive field center of rat ganglion cells.
Spike Firing Pattern of Output Neurons of the Limulus Circadian Clock
The lateral eyes of the horseshoe crab (Limulus polyphemus) show a daily rhythm in visual sensitivity that is mediated by efferent nerve signals from a circadian clock in the crab's brain. How these signals communicate circadian messages is not known for this or other animals. Here the authors describe in quantitative detail the spike firing pattern of clock output neurons in living horseshoe crabs and discuss its possible significance to clock organization and function. Efferent fiber spike trains were recorded extracellularly for several hours to days, and in some cases, the electroretinogram was simultaneously acquired to monitor eye sensitivity. Statistical features of single- and multifiber recordings were characterized via interval distribution, serial correlation, and power spectral analysis. The authors report that efferent feedback to the eyes has several scales of temporal structure, consisting of multicellular bursts of spikes that group into clusters and packets of clusters that repeat throughout the night and disappear during the day. Except near dusk and dawn, the bursts occur every 1 to 2 sec in clusters of 10 to 30 bursts separated by a minute or two of silence. Within a burst, each output neuron typically fires a single spike with a preferred order, and intervals between bursts and clusters are positively correlated in length. The authors also report that efferent activity is strongly modulated by light at night and that just a brief flash has lasting impact on clock output. The multilayered firing pattern is likely important for driving circadian rhythms in the eye and other target organs.
Spatial Receptive Field Properties of Rat Retinal Ganglion Cells
The rat is a popular animal model for vision research, yet there is little quantitative information about the physiological properties of the cells that provide its brain with visual input, the retinal ganglion cells. It is not clear whether rats even possess the full complement of ganglion cell types found in other mammals. Since such information is important for evaluating rodent models of visual disease and elucidating the function of homologous and heterologous cells in different animals, we recorded from rat ganglion cells in vivo and systematically measured their spatial receptive field (RF) properties using spot, annulus, and grating patterns. Most of the recorded cells bore likeness to cat X and Y cells, exhibiting brisk responses, center-surround RFs, and linear or nonlinear spatial summation. The others resembled various types of mammalian W cell, including local-edge-detector cells, suppressed-by-contrast cells, and an unusual type with an ON-OFF surround. They generally exhibited sluggish responses, larger RFs, and lower responsiveness. The peak responsivity of brisk-nonlinear (Y-type) cells was around twice that of brisk-linear (X-type) cells and several fold that of sluggish cells. The RF size of brisk-linear and brisk-nonlinear cells was indistinguishable, with average center and surround diameters of 5.6 ± 1.3 and 26.4 ± 11.3 deg, respectively. In contrast, the center diameter of recorded sluggish cells averaged 12.8 ± 7.9 deg. The homogeneous RF size of rat brisk cells is unlike that of cat X and Y cells, and its implication regarding the putative roles of these two ganglion cell types in visual signaling is discussed.
