Complementary Control of Sensory Adaptation by Two Types of Cortical Interneurons

Reliably detecting unexpected sounds is important for environmental awareness and survival. By selectively reducing responses to frequently, but not rarely, occurring sounds, auditory cortical neurons are thought to enhance the brain\u27s ability to detect unexpected events through stimulus-specific adaptation (SSA). The majority of neurons in the primary auditory cortex exhibit SSA, yet little is known about the underlying cortical circuits. We found that two types of cortical interneurons differentially amplify SSA in putative excitatory neurons. Parvalbumin-positive interneurons (PVs) amplify SSA by providing non-specific inhibition: optogenetic suppression of PVs led to an equal increase in responses to frequent and rare tones. In contrast, somatostatin-positive interneurons (SOMs) selectively reduce excitatory responses to frequent tones: suppression of SOMs led to an increase in responses to frequent, but not to rare tones. A mutually coupled excitatory-inhibitory network model accounts for distinct mechanisms by which cortical inhibitory neurons enhance the brain\u27s sensitivity to unexpected sounds

Directly Imaged L-T Transition Exoplanets in the Mid-Infrared

Gas-giant planets emit a large fraction of their light in the mid-infrared ($\gtrsim$3$\mu$m), where photometry and spectroscopy are critical to our understanding of the bulk properties of extrasolar planets. Of particular importance are the L and M-band atmospheric windows (3-5$\mu$m), which are the longest wavelengths currently accessible to ground-based, high-contrast imagers. We present binocular LBT AO images of the HR 8799 planetary system in six narrow-band filters from 3-4$\mu$m, and a Magellan AO image of the 2M1207 planetary system in a broader 3.3$\mu$m band. These systems encompass the five known exoplanets with luminosities consistent with L$\rightarrow$T transition brown dwarfs. Our results show that the exoplanets are brighter and have shallower spectral slopes than equivalent temperature brown dwarfs in a wavelength range that contains the methane fundamental absorption feature (spanned by the narrowband filters and encompassed by the broader 3.3$\mu$m filter). For 2M1207 b, we find that thick clouds and non-equilibrium chemistry caused by vertical mixing can explain the object's appearance. For the HR 8799 planets, we present new models that suggest the atmospheres must have patchy clouds, along with non-equilibrium chemistry. Together, the presence of a heterogeneous surface and vertical mixing presents a picture of dynamic planetary atmospheres in which both horizontal and vertical motions influence the chemical and condensate profiles.Comment: Accepted to Ap

On the Morphology and Chemical Composition of the HR 4796A Debris Disk

[abridged] We present resolved images of the HR 4796A debris disk using the Magellan adaptive optics system paired with Clio-2 and VisAO. We detect the disk at 0.77 \microns, 0.91 \microns, 0.99 \microns, 2.15 \microns, 3.1 \microns, 3.3 \microns, and 3.8 \microns. We find that the deprojected center of the ring is offset from the star by 4.76$\pm$1.6 AU and that the deprojected eccentricity is 0.06$\pm$0.02, in general agreement with previous studies. We find that the average width of the ring is 14$^{+3}_{-2}$, also comparable to previous measurements. Such a narrow ring precludes the existence of shepherding planets more massive than \about 4 \mj, comparable to hot-start planets we could have detected beyond \about 60 AU in projected separation. Combining our new scattered light data with archival HST/STIS and HST/NICMOS data at \about 0.5-2 \microns, along with previously unpublished Spitzer/MIPS thermal emission data and all other literature thermal data, we set out to constrain the chemical composition of the dust grains. After testing 19 individual root compositions and more than 8,400 unique mixtures of these compositions, we find that good fits to the scattered light alone and thermal emission alone are discrepant, suggesting that caution should be exercised if fitting to only one or the other. When we fit to both the scattered light and thermal emission simultaneously, we find mediocre fits (reduced chi-square \about 2). In general, however, we find that silicates and organics are the most favored, and that water ice is usually not favored. These results suggest that the common constituents of both interstellar dust and solar system comets also may reside around HR 4796A, though improved modeling is necessary to place better constraints on the exact chemical composition of the dust.Comment: Accepted to ApJ on October 27, 2014. 21 pages, 12 figures, 4 table

Climate change 2014 : impacts, adaptation, and vulnerability

Current and future climate-related drivers of risk for small islands during the 21st century include sea level rise (SLR), tropical and extratropical cyclones, increasing air and sea surface temperatures, and changing rainfall patterns (high confidence; robust evidence, high agreement). Current impacts associated with these changes confirm findings reported on small islands from the Fourth Assessment Report (AR4) and previous IPCC assessments. The future risks associated with these drivers include loss of adaptive capacity and ecosystem services critical to lives and livelihoods in small islands.peer-reviewe

The Gray Needle: Large Grains in the HD 15115 Debris Disk from LBT/PISCES/Ks and LBTI/LMIRcam/L' Adaptive Optics Imaging

We present diffraction-limited \ks band and \lprime adaptive optics images of the edge-on debris disk around the nearby F2 star HD 15115, obtained with a single 8.4 m primary mirror at the Large Binocular Telescope. At \ks band the disk is detected at signal-to-noise per resolution element (SNRE) \about 3-8 from \about 1-2\fasec 5 (45-113 AU) on the western side, and from \about 1.2-2\fasec 1 (63-90 AU) on the east. At \lprime the disk is detected at SNRE \about 2.5 from \about 1-1\fasec 45 (45-90 AU) on both sides, implying more symmetric disk structure at 3.8 \microns . At both wavelengths the disk has a bow-like shape and is offset from the star to the north by a few AU. A surface brightness asymmetry exists between the two sides of the disk at \ks band, but not at \lprime . The surface brightness at \ks band declines inside 1\asec (\about 45 AU), which may be indicative of a gap in the disk near 1\asec. The \ks - \lprime disk color, after removal of the stellar color, is mostly grey for both sides of the disk. This suggests that scattered light is coming from large dust grains, with 3-10 \microns -sized grains on the east side and 1-10 \microns dust grains on the west. This may suggest that the west side is composed of smaller dust grains than the east side, which would support the interpretation that the disk is being dynamically affected by interactions with the local interstellar medium.Comment: Apj-accepted March 27 2012; minor correction

First Light LBT AO Images of HR 8799 bcde at 1.65 and 3.3 Microns: New Discrepancies between Young Planets and Old Brown Dwarfs

As the only directly imaged multiple planet system, HR 8799 provides a unique opportunity to study the physical properties of several planets in parallel. In this paper, we image all four of the HR 8799 planets at H-band and 3.3 microns with the new LBT adaptive optics system, PISCES, and LBTI/LMIRCam. Our images offer an unprecedented view of the system, allowing us to obtain H and 3.3$ micron photometry of the innermost planet (for the first time) and put strong upper-limits on the presence of a hypothetical fifth companion. We find that all four planets are unexpectedly bright at 3.3 microns compared to the equilibrium chemistry models used for field brown dwarfs, which predict that planets should be faint at 3.3 microns due to CH4 opacity. We attempt to model the planets with thick-cloudy, non-equilibrium chemistry atmospheres, but find that removing CH4 to fit the 3.3 micron photometry increases the predicted L' (3.8 microns) flux enough that it is inconsistent with observations. In an effort to fit the SED of the HR 8799 planets, we construct mixtures of cloudy atmospheres, which are intended to represent planets covered by clouds of varying opacity. In this scenario, regions with low opacity look hot and bright, while regions with high opacity look faint, similar to the patchy cloud structures on Jupiter and L/T transition brown-dwarfs. Our mixed cloud models reproduce all of the available data, but self-consistent models are still necessary to demonstrate their viability.Comment: Accepted to Ap

Modulating PV activity does not affect frequency tuning, but bidirectionally affects frequency selectivity.

<p>A, B, C. Frequency response function (top) and tuning curve (bottom) of a putative excitatory neuron in the absence of photostimulation (light-Off trials) and during photostimulation of AC(light-On trials). Inset diagram shows circuits targeted by photomodulation. A. PV-ChR2: light activates PVs. B. PV-Arch: light suppresses PVs. C. CamKIIα-ChR2: light activates excitatory neurons. D, E, F. Scatter plot (top) shows distribution of the BF for putative excitatory neurons in light-On and light-Off trials. Histogram (bottom) shows index of change in the BF due to photostimulation. See data in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002308#pbio.1002308.s001" target="_blank">S1 Data</a>. D. PV-ChR2 group: Photoactivation of PVs had no significant effect on the BF of the frequency response function. One-sample <i>t</i> test. <i>n</i> = 233, mean ΔBF = −0.01, t₂₃₂ = 0.94, <i>p</i> = 0.35. E. PV-Arch group: Photosuppression of PVs did not significantly affect the BF of the frequency response function. One-sample <i>t</i> test. <i>n</i> = 83, mean ΔBF = −0.04, t₈₂ = 1.98, <i>p</i> = 0.051. F. CamKIIα-ChR2 group: Direct photoactivation of excitatory neurons did not significantly affect the BF of the frequency response function. One-sample <i>t</i> test. <i>n</i> = 82, mean ΔBF = −0.004, t₈₁ = 0.22, <i>p</i> = 0.82. G, H, I. Scatter plot (top) shows distribution of the tuning width for putative excitatory neurons in light-On and light-Off trials. Histogram (bottom) shows index of change in the tuning width due to photostimulation. See data in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002308#pbio.1002308.s001" target="_blank">S1 Data</a>. G. PV-ChR2 group: Photoactivation of PVs significantly decreased the tuning width of the frequency response function. One-sample <i>t</i> test, mean ΔBW = −0.10, <i>t</i>₂₃₂ = 5.17, <i>p</i> = 5.2e-7. H. PV-Arch group. Photosuppression of PVs significantly increased the tuning width of the frequency response function. One-sample <i>t</i> test mean ΔBW = 0.13, <i>t</i>₈₂ = 4.31, <i>p</i> = 4.5e-5. I. CamKIIα-ChR2 group. Direct photoactivation of excitatory neurons significantly increased the tuning width of the frequency response function. One-sample <i>t</i> test mean ΔBW = 0.09, <i>t</i>₈₁ = 3.77, <i>p</i> = 4.5e-5. J, K, L. Scatter plot (top) shows distribution of sparseness for putative excitatory neurons in light-On and light-Off trials. Histogram (bottom) shows index of change in sparseness due to photostimulation of PVs. J. PV-ChR2 group: Photoactivation of PVs led to an increase in sparseness of the frequency response function. One-sample <i>t</i> test, mean ΔSparseness = −0.09, <i>t</i>₆₃₁ = 11.0, <i>p</i> = 6.6e-26. K. PV-Arch group. Photosuppression of PVs led to a decrease in sparseness. One-sample <i>t</i> test mean ΔSparseness = −0.04, <i>t</i>₁₅₈ = 2.96, <i>p</i> = 0.04. L. CamKIIα-ChR2 group. Direct photoactivation of excitatory neurons led to a decrease in sparseness. One-sample <i>t</i> test, mean ΔSparseness = −0.09, <i>t</i>₁₅₁ = 6.01, <i>p</i> = 1.3e-8. M–O. Change in sparseness due to photostimulation was negatively correlated with the change in tuning width in all tested groups: PV-ChR2 (M, <i>p</i> = 7.4e-61), PV-Arch (N, <i>p</i> = 2.7e-21), CamKIIα-ChR2 (O, <i>p</i> = 6.3e-19). P. Change in sparseness did not significantly correlate with behavioral <i>Th</i> due to manipulation of PVs activity. Each dot represents data averaged for single units from each subject at one light intensity (only subjects with >5 identified single units were included). Blue: PV-ChR2 group (<i>n</i> = 28); Green: PV-Arch group (<i>n</i> = 5). Magenta: CamKIIα-ChR2 group (<i>n</i> = 6, not included in regression analysis). <i>p</i> = 0.21. For PV-ChR2 mice, data are combined over three laser powers used to activate PV interneurons (0.2, 0.5, and 10 mW/mm²). J, K, L Data for putative excitatory neurons that showed increased FR in response to tones (“auditory” neurons). PV-ChR2: <i>n</i> = 632; PV-Arch: <i>n</i> = 159; CamKIIα-ChR2: <i>n</i> = 152. D–I, M–O. Data for “auditory” neurons fitted to Gaussian function at <i>R</i>^<i>2</i> > 0.4. PV-ChR2: <i>n</i> = 233; PV-Arch: <i>n</i> = 83, CamKIIα-ChR2: <i>n</i> = 82.</p

Mutually coupled excitatory–inhibitory neuronal model accounts for differential effects of PV and excitatory neuronal modulation on tone-evoked response magnitude.

<p>A. Diagram of model of inhibitory and excitatory mutually coupled neuronal populations. Closed circles: excitatory inputs; open circles: inhibitory inputs; -: depressing synapse. Blue boxes: excitatory pathway. Red boxes: inhibitory pathway. B. Tone-evoked responses of model neuronal excitatory population under different optogenetic manipulations. Tone is from 200 to 250 ms. Left: ChR2 in inhibitory neurons. Center: Arch in inhibitory neurons. Right: ChR2 in excitatory neurons. Black trace: Light-off condition; Color trace: Light-on condition. See matlab code in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002308#pbio.1002308.s016" target="_blank">S1 Model</a>. C. Mean magnitude of tone-evoked responses under different stimulation conditions.</p

Cortical inhibitory neurons bidirectionally regulate frequency discrimination acuity.

<p>A. Experimental design. On each trial, a sequence of three acoustic stimuli was presented: background tone (f₁, 15 kHz, 10–20 s), prepulse tone (f₂, 10.2–15 kHz, 80 ms), and startle broadband noise (SN, 20 ms). In light-On trials, the laser (1 s, blue bar) was activated overlapping with the prepulse. In light-Off trials, the laser did not overlap with the prepulse. B, D, F. Left. Diagram shows circuits targeted by photomodulation. Right. Representative examples of the ASR (pressure applied by the mouse on the load cell platform in responses to startle noise) in PV-ChR2 (B), PV-Arch (D), and CamKIIα-ChR2 (F) mice. Top. Mean ASR for 10 light-Off trials in one session. Bottom. Mean ASR for 10 light-On trials in the same session. Note that ASRs decrease as the frequency shift between 15 kHz background tone and prepulse tone (f₂) increases. C, E, G. Left. PPI as a function of frequency shift between the prepulse and the background tone on light-On (color) and light-Off (gray) trials. Vertical dashed lines: <i>Th</i>. Error bars: Mean ± SEM. Right. <i>Th</i> threshold for light-On and light-Off trials and for separate “no light” session, in which no photostimulation was presented. C. Photoactivation of PVs in PV-ChR2 group decreased <i>Th</i> (paired t-test with Bonferroni adjustment for comparison between performance on "light-on" trials to "no-light" session and "light-off" trials, <i>t</i>₁₄ = 3.2, <i>p</i> = 0.01; <i>t</i>₁₄ = 3.6, <i>p</i> = 0.006; <i>n</i> = 15 mice). E. Photosupression of PVs in PV-Arch group increased <i>Th</i> PV-Arch group (t₁₅ = 2.6, <i>p</i> = 0.034; <i>t</i>₁₅ = 3.2, <i>p</i> = 0.012; <i>n</i> = 16). G. Increasing activity level of excitatory neurons in CamKIIα-ChR2 mice did not affect behavioral <i>Th</i>. ns: paired <i>t</i> test, <i>n</i> = 6, <i>t</i>₅ = 0.78, <i>p</i> = 0.47; <i>t</i>₅ = 0.36, <i>p</i> = 0.73. Dots depict data for an individual subject. Bars depict mean value for each group. See data in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002308#pbio.1002308.s001" target="_blank">S1 Data</a>.</p