The specificity of the Aβo-induced current of PrPC-mGluR5 oocytes

The specificity of the Aβo-induced current of PrPC-mGluR5 oocytes was examined. Although mGluR1 expression leads to equally strong Glu-induced current (Figures 3A and 3B), there is no detectable

Aβo-induced current (Figures 3A and 3C). PrPC lacking the Aβo binding domain, PrPΔ23–111 (Chen et al., 2010, Laurén et al., 2009 and Um et al., 2012), fails to support Aβo-induced signaling through mGluR5 (Figure 3C). The anti-PrPC antibody, 6D11, binds to residues 95–105 and prevents Aβo interaction (Chung et al., 2010, Laurén et al., 2009 and Um et al., 2012). Preincubation with 6D11 blocks Aβo responses, but not Glu responses, in PrPC-mGluR5 oocytes (Figures 3B and 3C). The Aβo-induced response has an XAV-939 solubility dmso EC50 of 1 μM monomer equivalent, an estimated 10 nM oligomer concentration (Figure 3D). A characteristic of G protein-mediated responses in Xenopus oocytes is strong desensitization. Maximal Glu stimulation nearly eliminates subsequent responses to Glu for 10–15 min. Consistent with the Aβo-PrPC-mGluR5 responses

sharing this pathway, pretreatment with Glu eliminates the response to subsequent Aβo ( Figure 3E). In addition, pretreatment with cell Vorinostat supplier permeable BAPTA-AM to chelate intracellular calcium abrogated the Aβo-induced signal ( Figure 3E), as for Glu ( Saugstad et al., 1996). Thus, Aβo interaction with a PrPC-mGluR5 complex mobilizes calcium stores. Although mGluR5-mediated signaling to Fyn is as robust with Aβo-PrPC as with Glu, signaling to calcium mobilization is substantially less effective for Aβo-PrPC than with Glu as the mGluR5 ligand, so Aβo does not mimic Glu precisely. We considered whether Aβo regulates neuronal calcium signaling through mGluR5 directly and acutely. Chronic else Aβo-PrPC-Fyn signaling can indirectly alter NMDA receptor (NMDAR) trafficking to modulate NMDA-induced calcium responses (Um et al., 2012). We used a calcium-sensitive fluorescent

dye to assess direct immediate response to Aβo in 21 days in vitro (DIV) cortical cultures. In low-density cultures, there is little direct calcium response to Aβo under the conditions that modulate NMDAR responses (data not shown; Um et al., 2012). With microscopic imaging, Aβo occasionally induces local calcium transients, but there is no generalization and measurement across a microtiter well does not detect a change (not shown). Higher density cultures exhibit spontaneous synchronized calcium increases (Figure S3A) that depend on network connectivity being suppressed by tetrodotoxin (TTX), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), or 2-amino-5-phosphonopentanoic acid (APV) (Figures S3B and S3C) (Dravid and Murray, 2004). Under these conditions, Aβo induces an increase of intracellular calcium (Figure 4A). Averaging multiple wells smoothes random spontaneous signals (Figure S3A), and Aβo-induced responses are apparent (Figure 4A). This response is oligomer specific; no response is detected with monomeric Aβ (Figure 4C).

A constant current isolated stimulator (Digitimer, Welwyn Garden

A constant current isolated stimulator (Digitimer, Welwyn Garden City, Hertfordshire, UK) delivered continuous electrical pulses to the STN electrodes at an intensity below the threshold for induced movement (50–250 μA). The motor performance of the hemi-Parkinsonian rat before (5 min), during (2 min), and after (5 min) STN-DBS were compared with the spontaneous exploratory movement (5 min) of intact rats (ANY-maze 4.70 software; Stoelting,Wood Dale, IL). The dependence of the efficacies of DBS-STN on stimulation frequencies (0.2, 1, 5, 10, 50, 125, 200, and 250 Hz) and pulse width (10, 20, 40, 60,

80, and 100 μs) were studied systematically. While the animals were performing in the open field test, both extracellular Sirolimus order spike trains and the local field potentials (LFPs) in MI were recorded simultaneously using a 32-channel electrophysiological data acquisition system (OmniPlex system, Plexon, Dallas, TX). In the behavioral assessment, muscle contractions in the contralateral face and limb could be induced when the stimulation site was located at the lateral STN border (confirmed

postmortem) or the stimulation amplitude used was high (>1 mA). Thus, contralateral muscle contraction at low threshold stimulation was indicative of the possibility that the electrode was very near or inserted NLG919 into the internal capsule and considered unacceptable. For all other cases, the stimulation value was set below the threshold of visible muscular contraction, but at which it could bring behavioral improvement. The t tests were performed to compare the motor performance from different groups. Paired t tests were performed on the data

from hemi-Parkinsonian isothipendyl rats only, comparing the STN-DBS period to both the “pre” and “post” periods. To study the dependence of behavioral improvement on stimulation frequency and pulse width in hemi-Parkinsonian rats, an additional ANOVA repeated-measures analysis (stimulus frequency and pulse width as repeated-measures, respectively) followed by a LSD post hoc test was also performed. All these behavioral test results are shown as mean ± SEM. The stimulus artifact removal and single-unit spike-sorting process were performed in the Off-line Spike Sorter V3 workspace (Plexon, Dallas, TX), using a combination of automatic and manual sorting techniques. Burst discharge was quantified by the Legendy surprise method. Cross-correlation analysis was applied to study the synchronization level among CxFn. The oscillatory rhythm in MI was measured as the spectrum of LFP using fast Fourier transform at 0.2 Hz resolution. When investigating the coherence phase between the spikes of each CxFn and the simultaneously recorded LFP, the polar histogram was built by filtering the LFP into beta band (11–30 Hz). Coronal sections were cut at the STN (20 μm), MI (20 μm), SNc (20 μm), and striatum (200 μm) by freezing microtome.

The Aβ plaque-specific

mE8 antibody might be an attractiv

The Aβ plaque-specific

mE8 antibody might be an attractive candidate therapy to consider for secondary prevention trials for individuals with preclinical AD as well as for treatments of individuals with very mild dementia due to AD. Since those with preclinical AD and mild cognitive impairment or very mild dementia MDV3100 ic50 due to AD already have substantial Aβ deposition in their brain (Jack et al., 2010; Perrin et al., 2009), this type of treatment targeting pre-existing Aβ plaques might be quite promising as a disease modifying treatment. D.M.H. is a cofounder and on the Scientific Advisory Board of C2N Diagnostics. In the last year, he served as a neuroscience therapeutic area Scientific Advisor to Pfizer. “
“Neurons are some of the most complex and highly polarized cells in our body. Their complex dendritic morphologies underlie their ability to integrate synaptic inputs. For this reason, the mechanisms that drive dendritic morphogenesis have been extensively

studied over recent decades (reviewed Whitford et al., 2002). Cytoskeletal dynamics are required for proper formation and maintenance of both dendritic and axonal branches (reviewed Kobayashi and Mundel, 1998; Gallo, 2011). The cytoskeleton is composed of microtubules (MTs), Wnt inhibitor actin filaments, intermediate filaments, and a myriad of regulators that process, order, modify, and remove these structures in a dynamic way. MTs are the largest and longest of these filaments, and are formed by polymerization of α- and β-tubulin dimers. This polymerization

gives rise to an inherent polarity along microtubules with a plus-end (where new dimers are polymerized) and a minus-end (where dimers are depolymerized) (reviewed Baas and Lin, 2011). The site at which microtubules are nucleated in neurons has PAK6 been an important open question. This has been widely studied in nonneuronal cell types, but because of technical limitations is only recently being addressed in neurons. We have learned from nonneuronal cell types that microtubules are often nucleated at the microtubule-organizing center (MTOC), which is coupled to the centrosome. However, microtubules can also be nucleated from the nuclear envelope, melanosomes, plasma membrane, and the Golgi complex in a process called acentrosomal nucleation (reviewed Vinogradova et al., 2009). MT nucleation at the Golgi has received recent attention as it provides asymmetry in the MT arrays of motile cells and might be important for cell polarization. Four main proteins are thought to be responsible for the MT nucleating ability of the Golgi: γ-tubulin, AKAP450, GM130, and CLASPs, which provide a molecular scaffold for the MT nucleation process (Kollman et al., 2010; Rivero et al., 2009; Efimov et al., 2007).

A similar fractionation of mechanisms that contribute to psychiat

A similar fractionation of mechanisms that contribute to psychiatric diseases might be achieved by state and trait mapping, based on psychopathological and personality models. The ultimate hope is that the better understanding of the biological pathways to psychiatric disease will result in the development of new treatments. The insight into the neural mechanisms of psychiatric symptoms achieved through neuroimaging has already informed new nonpharmacological interventions such as deep-brain stimulation, transcranial magnetic stimulation, and neurofeedback that are currently

in clinical testing. Early and prophylactic interventions present an emerging future direction in clinical psychiatry (McGorry et al., 2011), and neuroimaging has the potential to aid the identification of learn more individuals at risk and monitor the effects of these

Galunisertib interventions. Future aims in the development of surrogate treatment markers would involve assessing whether psychological or pharmacological interventions normalize the patterns of brain structure or function that predicted disease risk. Another future direction with considerable clinical benefit would be the development of biomarkers that predict the response to a particular treatment and could then be used for therapeutic stratification. Despite available imaging techniques (Table 1) and molecular targets (Table 2), new ways of targeting intracellular processes are likely needed. A key persisting question for imaging research in psychiatry with respect to developing novel treatments is whether to focus on the detection of the primary pathology, or whether to probe the pathways that underlie resilience and recovery.

There is thus ample scope for ongoing and new psychiatric imaging initiatives to establish biomarkers and targets for diagnostic and therapeutic applications. The author’s work was supported by grants from the Biotechnology and Biological Sciences Research Council (BBSRC) (BB/G021538), the Economic and Social Research Council (ESRC) (RES-062-23-0946), and the Welsh National Centre for Mental Health. Lorraine Woods provided invaluable help designing the figures, and Miles through Cox, Stephen Daniels, Rainer Goebel, Tom Lancaster, Niklas Ihssen, Matthias Munk, Michael O’Donovan, Christian Röder, Krish Singh, Richard G Wise, and Kenneth Yuen commented on earlier versions of the manuscript or provided answers to specific questions. “
“The GABAergic system of the mammalian brain consists of GABA-releasing cells and receptors that bind GABA. GABA-releasing cells are extraordinarily diverse and highly specialized (Freund and Buzsáki, 1996 and Klausberger and Somogyi, 2008), both controlling the activity of local networks (e.g., interneurons) and forming the output of some brain areas and nuclei (e.g., striatal medium spiny neurons and cerebellar Purkinje cells).

, 2005) (see above)

A QUAS version became recently avail

, 2005) (see above).

A QUAS version became recently available (Potter et al., 2010). UAS-Shibirets1 is now widely used to study the acute affects of neuronal silencing on cell morphology and animal behavior, but there are some cautionary notes. Since UAS-Shibirets1 disrupts the recycling step, the vesicles must be released before it becomes effective, making UAS-Shibirets1 a use-dependent blocker. The exact temperature BKM120 threshold and mechanism of dominance are uncertain (Grant et al., 1998) although temperatures ranging from 29°C-34°C are used (see references in Table 2). The level of mutant dynamin required for blockade and the speed of inactivation may depend on neural type. The elevated GS-1101 mouse temperature may affect normal performance of some behaviors. UAS-Shibirets1 also causes build up of microtubules in some cells at permissive temperatures (Gonzalez-Bellido et al., 2009). Flies expressing constitutively dominant-negative and wild-type dynamin are available (Moline et al., 1999) and can be used as controls. Disruption of membrane depolarization is another way to silence neurons. Neurons open voltage-gated sodium channels (encoded by para) in response to membrane depolarization to propagate action potentials or graded changes. It is possible to reduce the number of sodium channels directly using UAS-Para RNAi ( Zhong et al., 2010) or to block para conductance with

tethered toxins ( Wu et al., 2008), but the more common approach has been to increase potassium conductance, which lowers the resting membrane potential or acts as a shunting current to prevent depolarization. UAS-Kir2.1 encodes a mammalian inward rectifying K+ channel and its expression provides the most complete suppression of depolarization of the reagents described

here ( Baines et al., 2001 and Paradis et al., 2001). This channel requires PIP2 ( Hardie et al., 2004), which suggests that levels of this cofactor may modulate Kir2.1′s efficacy in some cells. A recombinase-inducible second version allows temporally controlled expression ( Yang et al., 2009). Another construct, electrical knockout, UAS-EKO, encodes a version of the Shaker voltage-gated K+ channel that cannot inactivate and opens at a voltage threshold closer to the resting potential; it only partially blocks the photoresponse but is an effective neuronal silencer in some cell types ( White et al., 2001b). UAS-dOrk expresses a two-pore leak K+ channel and can suppress neuronal excitability ( Nitabach et al., 2002). Several reviews compare these options and the consensus is that UAS-Kir2.1 is the strongest silencer ( White et al., 2001a and Holmes et al., 2007). This kind of chronic manipulation of membrane potential may result in homeostatic compensation, so inclusion of Tub-GAL80ts to increase temporal control of expression may be advisable.

Similarities in structure have also occasioned comparisons betwee

Similarities in structure have also occasioned comparisons between the function of the olfactory bulb and the thalamus (Kay

and Sherman, 2007). In the mammalian spinal cord it has been shown that genetically silencing certain groups of neurons can have profound behavioral consequences (Gosgnach et al., 2006, Lanuza et al., 2004 and Zhang et al., 2008). For example, silencing excitatory V3a interneurons compromises the rhythmicity and stability of locomotor RO4929097 solubility dmso outputs (Zhang et al., 2008). The coherence of spiking activity in our model network was also similarly compromised by the removal of excitatory interactions. The sequence of bursts generated by the networks constructed here Selleck BIBW2992 qualitatively resembles the kind of dynamics seen in networks that exhibit a form of competition termed winnerless competition (WLC) (Rabinovich et al., 2001). These patterns of activity have been hypothesized to be heteroclinic orbits that connect saddle fixed points or saddle limit cycles in the system’s state space (Rabinovich, 2006). The stability of these sequences and the capacity

of the network to generate sequential patterns have been analyzed in detail. However, the relationship between the structure of the network and the resulting patterns of activation are not yet known. Ahn et al. (2010) derive a computationally efficient and analytically tractable discrete time dynamical system that accurately replicates the dynamics of a more complex Hodgkin-Huxley-type neuronal network. The discrete time model predicts which group of neurons will spike next given that a specific group of neurons spiked during a previous epoch. The constraints imposed on the model include the Ca2+ concentration in the cells, the ionic conductances, the neuronal thresholds, and the number of inputs each neuron receives from a group that spiked in a preceding epoch. Our approach is complementary to that of Ahn et al. (2010). We use a global descriptor Idoxuridine of the network structure (its colorings) to deduce the set of all possible solutions of the system

(a solution is valid only if it respects the coloring of the network). Additional constraints such as the directed connections between neurons, asymmetries in intrinsic parameters, and Ca2+ concentration in the cell (Ahn et al., 2010) can make specific solutions stable. In this study we used the insect olfactory system to derive a structure-dynamics relationship in neuronal networks. This relationship can be tested in other well-charted networks such as central pattern generators (Marder and Calabrese, 1996). In the stomatogastric ganglion, where reciprocal inhibition is ubiquitous and implicated in generating periodic patterns (Getting, 1989 and Marder and Calabrese, 1996), alternating bursts are produced by a number of different mechanisms.

L , Santiago de Compostela, Spain) The areas of the broad and na

L., Santiago de Compostela, Spain). The areas of the broad and narrow components and the line width at half-height of each component were measured by using MestRenova 7. Effective spin–spin relaxation time (T2*) values were obtained using Eq.  (1). equation(1) T2*s=1π×v1/2Hzwhere T2* represents the effective spin–spin relaxation time and v1/2 represents the line width at half-height. Significant

differences in water mobility (T2*) at different water activities and for different protein configurations were analyzed by ANOVA using the General Linear Model procedure with Tukey’s test at p < 0.05 (IBM SPSS Statistics for Windows, Version 21.0, click here IBM Corp. Armonk, NY). Water mobility has units of milliseconds (ms). Four Salmonella

serovars previously involved in outbreaks in dry foods were used in this study: Salmonella Typhimurium (peanut), Salmonella Tennessee (peanut), Salmonella Agona (dry cereal) and Salmonella Montevideo (pistachios and others). The cultures were stored in cryovials containing beads suspended in phosphate buffered saline, glycerol and peptone (Cryobank, Copan Diagnostics Inc., CA) and kept at − 80 °C. They were prepared for use by Onalespib consecutive culturing in 9 ml of Tryptic Soy Broth (TSB, Becton, Dickinson and Company, Sparks, MD) at 37 °C for 24 h. Following the second culture, a final transfer of 3 ml to 225 ml of TSB was made, followed by incubation for 24 h at 37 °C. Cells from the final culture were collected by

centrifugation (3363 g, 30 min), the supernatant fluid was removed, and the pellet was re-suspended in 2 ml of 1% bacto-peptone (Becton, Dickinson and Company, Sparks, MD). The cell suspension was then dried in a vacuum desiccator over anhydrous calcium sulfate for a minimum of three days to obtain aw levels below 0.1. The dried cells were pooled and manually crushed into a powder. The dried inoculum (0.05 g) was mixed with 0.95 g of Astemizole moisture equilibrated test protein powder to provide a 1 g sample. This inoculation method led to starting concentrations of 109 CFU/g. Re-equilibration of samples to the target aw was not necessary when using this procedure. Inoculated and control samples were packaged in retort pouches under vacuum to minimize moisture transfer to head space during survival studies. Samples were placed into standard retort pouches (Stock America, Inc., Grafton, WI). Retort pouches were then placed in FoodSaver Quart Bags, and the FoodSaver equipment (FoodSaver Silver, model FSGSSL0300-000, Sunbeam Products, Inc., Boca Raton, FL) was used for pulling a vacuum and sealing. After initial sealing of the FoodSaver bag, a second seal was applied to the retort pouch using an impulse sealer. The vacuum-sealed inoculated samples were stored at different temperatures (21 ± 0.6 °C, 36 ± 0.3 °C, 50 ± 0.5 °C, 60 ± 0.5 °C, 70 ± 0.5 °C and 80 ± 0.5 °C).

Katz’s brilliant work built on George Palade’s (1912–2008) studie

Katz’s brilliant work built on George Palade’s (1912–2008) studies on vesicular trafficking (Palay and Palade, 1955) and initiated a series of elegant electrophysiological experiments that characterized the process of synaptic transmission in exquisite detail. Among others, these studies revealed that Ca2+ triggers release in a highly cooperative manner (Dodge and Rahamimoff, 1967) within a few hundred microseconds (Sabatini and Regehr, 1996), which is not much slower than the opening of a voltage-gated ion channel. C59 wnt datasheet What molecular mechanisms enable fast vesicle fusion at a synapse, however, remained a mystery until molecular

biology allowed mechanistic dissection of vesicle fusion and its control by Ca2+ (reviewed in Südhof and Rothman, 2009). Katz’s work posed three basic questions: • How do vesicles fuse? This general question transcends neurobiology and is important for all areas of vesicle traffic selleck inhibitor and cell biology since membrane fusion is a universal process in eukaryotic cells. These three questions lie at the heart of a

molecular understanding of synaptic transmission. As described below, we now have a plausible framework of answers to these three questions, although much remains to be done. In the following, I will first provide a brief broad outline of the general release machinery (Figure 1) and then discuss in greater detail selected questions that in my personal view are particularly interesting. Due to space constraints, I do not aim to provide a comprehensive discussion of the field, and I apologize for the many omissions I am bound to commit. Moreover, owing to the same space constraints, I will focus on physiological studies. In particular, I am unable to give appropriate consideration to PD184352 (CI-1040) the many elegant liposome fusion studies that have recently been performed; for a more complete treatment of this subject, please see Brunger et al. (2009) and Marsden et al. (2011). Work over the lifetime of Neuron—two

and a half decades!—has produced a general framework for understanding neurotransmitter release that will be briefly summarized below ( Figure 1; see also reviews by Rizo and Rosenmund, 2008, Kochubey et al., 2011 and Mohrmann and Sørensen, 2012). Intracellular membrane fusion is generally mediated by SNARE proteins (for “soluble NSF attachment receptor proteins”) and SM proteins (for “Sec1/Munc18-like proteins”) that undergo a cycle of association and dissociation during the fusion reaction ( Figure 2). At the synapse, the vesicular SNARE protein synaptobrevin (aka VAMP) forms a complex with the plasma membrane SNARE proteins syntaxin-1 and SNAP-25 ( Söllner et al., 1993a). Prior to SNARE complex formation, syntaxin-1 is present in a closed conformation that cannot engage in SNARE complex formation; syntaxin-1 has to open for SNARE complex assembly to proceed ( Dulubova et al., 1999 and Misura et al., 2000).

For the majority of axons in the CNS that release neuropeptides,

For the majority of axons in the CNS that release neuropeptides, I favor a third local diffusion hypothesis- that neuropeptides released by most neurons act locally on

cells near the release site, with a distance of action of a few microns. Thus, a peptide’s action would be on its synaptic partners (even if the peptide is not released at the presynaptic specialization) and on immediately adjacent cells. In part this perspective is based on the low frequency of dense core vesicles in most CNS axons and the hours it would take to replenish released peptides from sites of synthesis in the cell body, making it difficult to achieve a substantial extracellular concentration of neuropeptide needed for a long-distance effect. In this context, the relatively slow replenishment of neuropeptide modulators may differ from catecholamine neuromodulators BMN 673 cell line that can be synthesized rapidly within axon terminals to support ongoing release. Furthermore,

as determined with ultrastructural analysis, a complex system of astrocytic processes surrounds many axodendritic synaptic complexes and tends to attenuate long-distance transmitter diffusion from many release sites ( Figure 1; Peters et al., 1991), thereby impeding actions of peptides at far-away targets, and maintaining a higher local extracellular concentration of the peptide. Peters et al. credit Ramon y Cajal with favoring the concept that a central function for glia was isolation of neuronal microdomains. That peptides released by most neurons may act within a few microns of the release site does not negate the fact GS-1101 clinical trial that some peptides can be released in large quantities and can act at longer distances. This may be the exception rather than the rule. For instance, considering the multiple subtypes of highly specialized NPY or somatostatin interneurons second in the hippocampus or cortex, coupled with the multiple peptide responses reported in nearby cells and the highly specialized functions of different nearby interneurons, often with restricted functional

microdomains (Freund and Buzsáki, 1996; Bacci et al., 2002; Klausberger et al., 2003), it seems most likely that released peptides here act primarily on nearby receptive partners. Consistent with the local diffusion perspective are findings related to peptides such as pigment dispersing factor (PDF) which plays a key role in regulating circadian rhythms of invertebrates (Im and Taghert, 2010; Zhang et al., 2010). Although cells that release PDF project to several regions of the Drosophila brain, the response of the releasing cells to PDF appears to be critical for some aspects of circadian function. Secreted PDF acts on PDF autoreceptors expressed by the releasing lateral-ventral pacemaker neurons to regulate the time of day during which behavioral activity occurs ( Choi et al., 2012; Taghert and Nitabach, 2012, this issue of Neuron). Most neuropeptides act by binding to a seven-transmembrane domain G protein-coupled receptor (GPCR).

So in mice where we did not record from PV cells we used this ran

So in mice where we did not record from PV cells we used this range of light intensity, i.e., light intensity was set to 0.05–0.1 mW/mm2, and increased until change in the activity Pyr cells was observed. The population response of the visual cortex to visual stimuli was monitored using local field potential recordings during this process. Light intensities never exceeded 1 mW/mm2. When recording from PV cells while photo stimulating Arch or ChR2 (Figure 2)

cortical illumination started before the visual stimulus selleck compound (to monitor the effect on spontaneous activity) and ended before the end of the visual stimulus (to determine the kinetics of recovery to visually evoked firing rates). Spontaneous spike rate was calculated as the average firing rate during a 0.5 s period before the presentation of the stimulus. The visual response to a given stimulus was the average

rate over the stimulus duration or over the period when both cortical illumination and visual stimulus occurred (1–2 s). Orientation selectivity index (OSI) was calculated as 1 − circular variance (Ringach et al., 1997). Responses to the 12 grating directions were fit with orientation tuning curves i.e., a sum-of-Gaussians (Figure 1, Figure 3 and Figure 4). The Gaussians are forced to peak 180 degrees apart, and to have the same tuning sharpness (σ) but can have unequal height (Apref and Anull, to account for direction selectivity), and a constant baseline B. The tuning sharpness was measured as 17-DMAG (Alvespimycin) HCl σ (2 ln(2))1/2, check details i.e., the half-width at half height (HWHH). Direction selectivity index (DSI) was calculated as (Rpref – Rnull) / (Rpref + Rnull), where Rpref is the response at the preferred direction and Rnull is the response 180 degrees away from the preferred direction.

Contrast-response curves were fit with the hyperbolic ratio equation ( Albrecht and Hamilton, 1982): R(C) = Rmax cn / (C50n + cn) + Roffset, where c is contrast, C50 is the semisaturation contrast, and n is a fitting exponent that describes the shape of the curve, Rmax determines the gain, and Roffset is the baseline response. To obtain the threshold-linear fit, we first computed a summary of Pyr cell responses in layer 2/3. The tuning curves of all cells were aligned to the same preferred orientation, a nominal value of 0 degrees and the maximal response was scaled to a nominal value of 100% (Figure 4A). We then plotted the median Pyr cell response measured during the suppression or activation of PV cells against the median response measured in the control condition (Figure 4B). The bootstrapped distribution of median responses was used to calculate errors bars in OSI, DSI, and HWHH. Please see Supplemental Experimental Procedures for more details. The membrane potential tuning, or net depolarization, as a function of orientation, θ, was modeled as: ΔV(θ)=gLRL+gE(θ)RE+gI(θ)RIgL+gE(θ)+gI(θ)−Vr gx=gmin+(gmin−gmax)e−θ22σ2.