The effect of dendritic field size on the frequency response of retinal ganglion cells.

<p>Panels (A–D) show the mean frequency response of A2, C2, D1 and D2 RGC types. Within each RGC type, cells are grouped and their frequency responses averaged according to their dendritic field diameter. Within each RGC type, cells with the largest dendritic fields are shown in black and those with the smallest dendritic fields are shown in grey. For comparison, the frequency response, averaged over all cells of a given type, irrespective of dendritic field size, is shown by the dashed line. Black dots indicate statistically significant differences between large-field and small-field RGC responses (t-tests, p < 0.05). Panels (E–H) show distributions of dendritic field diameter for each of the A2, C2, D1 and D2 RGC types, respectively.</p

Patch-clamp recording of responses to sinusoidal stimulus currents.

<p>Representative membrane potential recordings from an A2o-type retinal ganglion cell, during intracellular injection of sinusoidal stimulation currents (70 pA) at (A) 10 Hz, (B) 25 Hz, and (C) 60 Hz. The frequency and phase of the injected currents are indicated by the sinusoids (gray) shown below each membrane potential recording (black). The dashed line indicates 0 mV.</p

Reconstruction of recorded cell morphology.

<p>Representative confocal image stacks typical of those used for classification of recorded retinal ganglion cells (RGCs) according to their morphological cell type. Examples are shown for representative (A) A-type, (B) B-type, (C) C-type, (D) D-type, (E) ON [C2i], (F) OFF [A2o], and (G) ON-OFF [D2] RGCs. Panels (E–G) show the <i>en face</i> representation (top), revealing the scale and extent of the dendritic arborisation, and a cross-section (bottom), revealing where the dendrites of each cell stratify within the inner plexiform layer (IPL). Long-dashed lines indicate the boundary of the IPL and short-dashed lines indicate the approximate boundary between the two sublaminae. Recorded cells were labelled, via the patch pipette, with Alexa488 (green). Other cells in the ganglion cell layer (GCL) and inner nuclear layer (INL) were labelled with propidium iodide (red).</p

Intrinsic Physiological Properties of RGC Subtypes.

<p>Intrinsic Physiological Properties of RGC Subtypes.</p

The effect of soma size on the frequency response of retinal ganglion cells.

<p>Panels (A–D) show the mean frequency response of A2, C2, D1 and D2 RGC types, respectively. Within each RGC type, cells are grouped and their frequency responses averaged according to their soma diameter. Within each RGC type, cells with the largest soma diameters are shown in black and those with the smallest soma diameters are shown in grey. For comparison, the frequency response, averaged over all cells of a given type, irrespective of soma diameter, is shown by the dashed line. Panels (E–H) show distributions of soma diameter for each of the A2, C2, D1 and D2 RGC types, respectively.</p

Dendritic and electrical receptive fields.

<p>a-b) Sample cells depicting the stimulating array (large black discs) and the patch-clamp recording electrode (denoted by a *). Overlaid on the images are the morphological reconstructions of the cells. The sample cell in (a) is also shown in (c) 16. The sample cell in (b) is also shown in (c) 20. Note that the stimulating electrodes appear large, but the exposed area is only 400 μm. Also visible are the lycra threads used to keep the retina affixed and the stimulating electrode tracks. c) The electrical receptive fields shown together with the dendritic receptive field estimates. The electrodes with stars above them show the approximate location of the optic disc for each preparation.</p

Summary of results.

<p>Summary of results.</p

Recovery of model parameters for a sample cell.

<p>(a) The stimuli are projected onto the first two principal components, and . The grey squares represent the spike probability, where a black value represents 0 probability, and a white value represents a probability of 1. Plotted above and to the right are the histograms of the stimuli (gray) and the spike-triggered stimuli (black) along each component axis. (b) Eigenvalues of the spike-triggered stimuli recovered by principal component analysis (round circles) are plotted. The eigenvalues are normalized by the variance of the input stimuli. The shaded region represents the 95% confidence interval from the statistical hypothesis test. The hypothesis test recovered one significant excitatory and one significant suppressive component. The red arrows show the distance between the two most significant eigenvalues and the mean of the random distribution recovered from the first iteration of the hypothesis test. The length of the arrows represent <i>d</i>₁ and <i>d</i>₂ from Eq (<a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1004849#pcbi.1004849.e057" target="_blank">10</a>). (c) The nonlinear function recovered by fitting a double sigmoid to the spike probability projected onto and . Open circles represent the raw data and the solid line shows the nonlinear equation fit (r² = 0.98). This cell had a positive and negative threshold (parameters <i>c</i>₊ and <i>c</i>₋ in Eq (<a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1004849#pcbi.1004849.e017" target="_blank">5</a>)) of 129 μA and -152 μA proportional to and , respectively. (d) The true and (solid black) are compared to the root mean square (dashed line) of a distribution of and (gray). Stars show which electrodes were significant. In this preparation, electrode 12 was not operational. (e) Representation of the amplitudes that generate the ERFs, (left) and (right). The large circles represent the electrode locations. A correlation coefficient of -0.97 was obtained between and . Three electrodes significantly affected the cell in and in . In this experiment, the retina was placed such that the optic disc was located around electrode 9. The stimulation return electrode was placed distally above electrode 12. The green circle shows the approximate dendritic field of the recorded cell. Stimulus amplitudes ranged up to ±300 μA; however, the range shown here is smaller to make the differences in electrode amplitudes clearer.</p

Recovery of the spike-triggered stimuli for the spike-triggered covariance (STC) analysis.

<p>(a) Discretized sequence of the neural response and stimulus. Each stimulus consists of a combination of biphasic pulses applied to all 20 electrodes. Stimuli that evoked a spike in the neuron are recorded in the stimulus matrix <b>S</b>_D. (b) STC was conducted on the stimuli generating a response, <b>S</b>_D, to separate the stimulus space into a positive and negative region (+ and ×). The x-axis corresponds to the first eigenvector (); the y-axis corresponds to the second eigenvector (). Not all stimuli generated a response in the neuron. Shown in black are the total applied stimuli, <b>S</b>_T, which are overlaid by stimuli <b>S</b>_D (white crosses). Also shown are the projections of the electrical receptive fields, (large diamond) and (large circle).</p

Sample of the random pulses applied to 20 electrodes at a given time.

<p>(a) Snapshot of the random amplitude of biphasic pulses applied to all electrodes; the colors indicate amplitudes in μA. A positive amplitude produces an anodic-first pulse; a negative amplitude produces a cathodic-first pulse. Electrode amplitudes were sampled from a Gaussian distribution with variance σ². Electrode numbers are shown below each electrode. (b) Time course of the biphasic pulse applied to each electrode.</p