An Open Resource for Non-human Primate Imaging.

Non-human primate neuroimaging is a rapidly growing area of research that promises to transform and scale translational and cross-species comparative neuroscience. Unfortunately, the technological and methodological advances of the past two decades have outpaced the accrual of data, which is particularly challenging given the relatively few centers that have the necessary facilities and capabilities. The PRIMatE Data Exchange (PRIME-DE) addresses this challenge by aggregating independently acquired non-human primate magnetic resonance imaging (MRI) datasets and openly sharing them via the International Neuroimaging Data-sharing Initiative (INDI). Here, we present the rationale, design, and procedures for the PRIME-DE consortium, as well as the initial release, consisting of 25 independent data collections aggregated across 22 sites (total = 217 non-human primates). We also outline the unique pitfalls and challenges that should be considered in the analysis of non-human primate MRI datasets, including providing automated quality assessment of the contributed datasets

Chemogenetic Activation of Melanopsin Retinal Ganglion Cells Induces Signatures of Arousal and/or Anxiety in Mice

SummaryFunctional imaging and psychometric assessments indicate that bright light can enhance mood, attention, and cognitive performance in humans. Indirect evidence links these events to light detection by intrinsically photosensitive melanopsin-expressing retinal ganglion cells (mRGCs) [1–9]. However, there is currently no direct demonstration that mRGCs can have such an immediate effect on mood or behavioral state in any species. We addressed this deficit by using chemogenetics to selectively activate mRGCs, simulating the excitatory effects of bright light on this cell type in dark-housed mice. This specific manipulation evoked circadian phase resetting and pupil constriction (known consequences of mRGC activation). It also induced c-Fos (a marker of neuronal activation) in multiple nuclei in the hypothalamus (paraventricular, dorsomedial, and lateral hypothalamus), thalamus (paraventricular and centromedian thalamus), and limbic system (amygdala and nucleus accumbens). These regions influence numerous aspects of autonomic and neuroendocrine activity and are typically active during periods of wakefulness or arousal. By contrast, c-Fos was absent from the ventrolateral preoptic area (active during sleep). In standard behavioral tests (open field and elevated plus maze), mRGC activation induced behaviors commonly interpreted as anxiety like or as signs of increased alertness. Similar changes in behavior could be induced by bright light in wild-type and rodless and coneless mice, but not melanopsin knockout mice. These data demonstrate that mRGCs drive a light-dependent switch in behavioral motivation toward a more alert, risk-averse state. They also highlight the ability of this small fraction of retinal ganglion cells to realign activity in brain regions defining widespread aspects of physiology and behavior

Spatial receptive fields in the retina and dorsal lateral geniculate nucleus of mice lacking rods and cones

In advanced retinal degeneration loss of rods and cones leaves melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) as the only source of visual information. ipRGCs drive non-image-forming responses (e.g., circadian photoentrainment) under such conditions but, despite projecting to the primary visual thalamus [dorsal lateral geniculate nucleus (dLGN)], do not support form vision. We wished to determine what precludes ipRGCs supporting spatial discrimination after photoreceptor loss, using a mouse model (rd/rd cl) lacking rods and cones. Using multielectrode arrays, we found that both RGCs and neurons in the dLGN of this animal have clearly delineated spatial receptive fields. In the retina, they are typically symmetrical, lack inhibitory surrounds, and have diameters in the range of 10–30° of visual space. Receptive fields in the dLGN were larger (diameters typically 30–70°) but matched the retinotopic map of the mouse dLGN. Injections of a neuroanatomical tracer (cholera toxin β-subunit) into the dLGN confirmed that retinotopic order of ganglion cell projections to the dLGN and thalamic projections to the cortex is at least superficially intact in rd/rd cl mice. However, as previously reported for deafferented ipRGCs, onset and offset of light responses have long latencies in the rd/rd cl retina and dLGN. Accordingly, dLGN neurons failed to track dynamic changes in light intensity in this animal. Our data reveal that ipRGCs can convey spatial information in advanced retinal degeneration and identify their poor temporal fidelity as the major limitation in their ability to provide information about spatial patterns under natural viewing conditions

Online calibration and rod control verify silent substitution paradigm.

<p>Online calibration of the rod-isoluminant settings (A) and tests of rod contrast sensitivity (B) were performed both <i>in vitro</i> and <i>in vivo</i>. Displayed are representative data from dLGN. A. A 100 ms blue ‘flash’ (transition from yellow to blue LED) was presented at ND3 to provide conditions preferable to rods. Raster plots and associated PSTHs for an example melanopsin-stepping cell over a range of settings for the blue LED. In the middle (outlined by black dotted box) was the setting at which there was no change in firing, taken as the point of rod isoluminance, while decreasing (plots to left) or increasing (plots to right) the blue LED produced measurable responses in line with the appearance of negative or positive contrast for rods. Numbers above in the grey panels are estimated Michelson contrast for rods and melanopsin calculated according to known pigment absorption nomograms [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0123424#pone.0123424.ref021" target="_blank">21</a>]. B: We determined the ability of fast flicker and extended step stimuli to reveal responses to low contrast rod-isolating stimuli (yellow step on low blue background; values above are estimated Michelson contrast). Rod responses were apparent for estimated rod contrasts ≥15% under both a 4Hz flicker (Bi; raster above and PSTH of mean firing rate) and 30sec step (Bii; mean±SEM firing rate) in this representative cell. Firing rates for both A and B match scale bar (bottom left 5 spikes/s).</p

Retinal responses in <i>rd/rd cl</i> mice.

<p>A: Trial bin count examples (5 second bins of time) of three cells responding to a 20s 71% contrast step (background log 12.8 to step log 13.56 melanopsin photons/cm2/s) in a <i>rd/rd cl</i> retina. Note the variety in the latency of response offset in examples 1 and 2, and the poor response reproducibility that is typical of <i>rd/rd cl</i> mice in example 3. Colour bar to the right of the plot (FR Hz) denotes the firing rate of cells in this and subsequent Trial bin count figures. B: Averaged plots for firing rate over time of melanopsin-step responsive cells (mean±SEM) to a 20s step (Bi n = 15) and a 60s step (Bii n = 17). Both step durations elicit a significant change in firing to the baseline rate (**** P<0.0001). C: A plot of mean onset and offset latencies for each individual responsive cell over multiple stimulus repeats reveals the extremely sluggish nature of light responses in <i>rd/rd cl</i> mice.</p

Responses to melanopsin-isolating steps and gradual irradiance ramps in retina.

<p>A: Trial bin count examples of two cells responding to a 71% contrast step (blue bar at 0 to 20 seconds) presented during protocol 1 (background log 12.75 melanopsin photons/cm²/s to step log 13.5 photons/cm²/s) before (i) and during (ii) synaptic blockade. Before and after graphs are scaled to same axis to show changes in baseline activity upon synaptic blockade. B: Example raster plots and PSTH to a 50ms rod favouring yellow flash from dark (flash intensity log 11.45 rod photons/cm²/s) under normal conditions (aCSF) and under synaptic blockade (5 minutes after application of L-AP4 + NBQX) in a cell that was identified to respond to our melanopsin-isolating stimulus. C: Averaged plots for firing rate over time of consistent (n = 31) melanopsin-step responsive cells (mean±SEM) before (left) and during (right) synaptic blockade. D: Mean response onset and offset latencies for individual melanopsin-step responsive cells in the presence (purple symbols) and absence (green) of synaptic blockade. E: Under protocol 2, retinal cells responding to a melanopsin-step (n = 22/ 314 cellls; 71% contrast) do so over a range of background irradiances on both the upward and downward phases of the ramp (Repeated measures 2-way ANOVA, step vs baseline firing rate x irradiance; main effects of irradiance (p<0.001), step vs baseline (p<0.001) and interaction (p<0.05); Bonferroni post-hoc comparisons marked on figure as ** and *** p<0.01 for ND2 upward ramp and ND1.5 for downward; n = 22 cells). F: Retinal melanopsin-step responsive cells also tracked the gradual change in irradiance during protocol 2, revealed as a change in firing rate (mean± SEM) as a function of ramp progression.</p

Responses of cells sensitive to the melanopsin-step over a range of irradiances.

<p>A: PSTHs for firing rate across melanopsin-isolating steps (71% contrast) over a range of backgrounds (across both increasing and decreasing arms of the ramp; n = 24 responsive cells mean±SEM). See 5Cii for significance values. B: Scatter plot displaying mean onset vs offset latencies for each cell as a function of background irradiance. Ci: Mean change in firing rate associated with the melanopsin-isolating step (firing rate during step—firing rate over previous 10 s) with increasing irradiance during the upwards (dark blue) and downwards (light blue) phases of the ramping protocol. Ci and ii Significant responses were recorded for steps against backgrounds ≥ 12.1 log melanopsin photons/cm²/s (ND2) on the ramp up and 13.1 log melanopsin photons/cm²/s (ND1) on the ramp down (2-way RM ANOVA step vs baseline firing rage x irradiance; main effects of irradiance (p<0.05), step vs baseline (p<0.001) and interaction (p<0.001); Bonferroni post-hoc comparisons p<0.01 for ND2 and above for upward ramp and ND1 for downward). D: Firing rate (mean±SEM; n = 54) of dLGN stepping cells from protocol 1 to a bright blue 10 sec step from dark (log 14.1 melanopsin photons/cm²/s; purple bar). Note sustained activity after the termination of the step, considered to be a feature of the melanopsin light response. E: There was no significant change in time averaged firing rate of cells responsive to the melanopsin step as a function of ramp progression (mean±SEM n = 24).</p