We would also like to clarify the figure legends of Figures 2, 4C

We would also like to clarify the figure legends of Figures 2, 4C–4E, S1B, S3A, and S3B. Western blots were developed using the Odyssey Imaging System (LI-COR Biosciences), which allows detection of multiple primary antibodies probed on the same blot. Thus, the beta-actin loading controls are the same for two different primary antibodies—for example, Figures 2A and 4C. “
“(Neuron 73, 713–728; February 23, 2012) The data sets in this paper have been now deposited and released in NCBI with the

GEO accession numbers GSE40431, GSE40506, and GSE40510. “
“The mammalian IGF2 mRNA-binding protein family (Gene symbol: IGF2BP) comprises three RNA-binding proteins with a conserved domain structure Wnt inhibitor including two N-terminal RNA recognition motifs (RRM) and four C-terminal hnRNP K homology (KH) domains (Fig. 1a; reviewed in: [1]). Diverse biological roles and distinct target mRNAs identified for the individual IGF2BP family members account for the numerous synonyms and aliases assigned to protein family (CRD-BP, KOC, ZBP, VICKZ or Vg1RBP/Vera ABT-888 purchase in Xenopus). The first family member described was IGF2BP1, which was initially identified as a protein involved in the stabilization of the MYC mRNA [2]. The protein prevents MYC

mRNA degradation by binding to the coding region instability determinant (CRD) and thereby promotes tumor cell proliferation and survival in various cancer contexts (reviewed in: [1]). Later on, IGF2BP1 was found to control the subcellular sorting of the ACTB mRNA in primary fibroblasts and neurons by binding to the cis-acting zipcode in the ACTB mRNA’s 3′UTR [3]. By controlling the spatially restricted translation of the ACTB mRNA, IGF2BP1 was proposed to enhance neurite outgrowth and axonal guidance ([4]; reviewed

in: [1]). The human IGF2BP2 was first described in 1999 due to its association with the IGF2 mRNA [5]. Later on the protein, Oxygenase also termed p62, was proposed as an auto-antigen in hepatocellular carcinoma [6]. Most notably, however, single nucleotide polymorphisms (SNPs) have been identified in the second intron of the human IGF2BP2 gene. These were correlated with an elevated risk of type two diabetes by various studies (reviewed in: [7]). Consistently, IGF2BP was recently identified as a modulator of mTOR signaling and IGF2 mRNA translation [8]. The human IGF2BP3, which of all human family members shows the highest similarity to Xenopus Vg1/RBP, was initially termed KOC and identified due to its high abundance in pancreatic cancer tissue [9]. Since its first identification a bulk of literature reported IGF2BP3 to be the mainly expressed family member in human cancer (reviewed in: [10]). Despite their high degree of similarity the IGF2BP proteins exhibit quite different expression patterns (reviewed in: [1]).

Enhancement at the injection site was largely cleared by 2 months

Enhancement at the injection site was largely cleared by 2 months postinjection (Figure S4C, red line), similar to the time course of the transported compound in VPL (Figure 4B). Thus, in both the injection site and the transport targets, the time course of GdDOTA-CTB enhancement was fully consistent with neuronal uptake of the selleck inhibitor tracer CTB; presumably extracellular diffusion of GdDOTA alone would clear much faster. To confirm the latter, we directly measured the rate of extracellular diffusion by injecting GdDOTA alone into S1 (n = 4). GdDOTA injections immediately produced a strong signal enhancement throughout a large region of the cortex, as one would expect

from rapid extracellular diffusion (Figure S4B, blue line in S4C). Moreover, the enhancement due to GdDOTA alone cleared extremely rapidly: it peaked at the first data point, immediately after injection, and it cleared completely within 24 hr. Thus, the GdDOTA was completely cleared well before the enhancement due to neuronal transport (i.e., from the GdDOTA-CTB) peaked (days 5–7, cf. red versus blue lines in Figure S4C). buy CP-673451 An additional control experiment was designed to further rule out the possibility that GdDOTA-CTB transport can be mediated by nonselective, passive uptake and diffusion. To test that hypothesis,

we injected another contrast compound, Gd-Albumin, in which the gadolinium was conjugated with bovine serum albumin (a protein that has a molecular weight similar to CTB). Although the injected gadolinium concentration Carnitine dehydrogenase from Gd-Albumin was comparable to the GdDOTA-CTB (i.e., 65–75 mM), and the protein concentration from Gd-Albumin was also very high (30% protein), we found that the signal intensity at the

Gd-Albumin injection sites was much weaker (compare Figure S4, red line, and Figure S5, solid black line), and the enhancement was much smaller, indicating that Gd-Albumin was rapidly cleared immediately after injection. The signal intensity at the injection core continued to decrease on day 4, returning to baseline values by day 7 (Figure S5). Except for the focal injection cores, no enhancement was present anywhere in the brain, including the thalamus, at any MR imaging time point. Overall, these data further support the conclusion that the GdDOTA-CTB conjugate is actively and selectively taken up and transported within the brain, as a MR-visible anatomical tracer. To clarify the relative advantages or disadvantages of GdDOTA-CTB, we compared GdDOTA-CTB results with comparable data using the tract-tracing contrast agent manganese. For both tracers, the signal intensity was measured at both the S1 injection site and the thalamic transport site, at comparable time points across tracers (i.e., immediately postinjection, at and after peak transport times for the two tracers). The two contrast agents were injected at the same concentration and volume.

Incomplete penetrance of ventral remodeling in double mutants

Incomplete penetrance of ventral remodeling in double mutants

was also observed by imaging. In unc-55; hbl-1 double mutants, we observed patches of the ventral nerve cord that contained an approximately normal number of synapses, while other regions totally lacked synapses (data not shown). A transgene expressing hbl-1 in the VD and DD neurons of unc-55; hbl-1 double mutants (using the unc-25 promoter) decreased the ventral IPSC rate to that observed in unc-55 single mutants ( Figure 3F) but did not rescue the non-neuronal hbl-1 defects ( Figure S3A). These results suggest that HBL-1 acts in VD neurons to promote ectopic remodeling. To further document the functional integrity of the ventral VD synapses, we analyzed the locomotion behavior of unc-55; hbl-1 double mutants. A prior study showed that ectopic remodeling of VD synapses in unc-55 mutants was accompanied by a locomotion defect ( Zhou and Walthall, 1998). During backward KPT-330 movement, unc-55 mutants assume a ventrally coiled body posture, presumably due to the absence of inhibitory input to the ventral body muscles ( Figure 3I). This unc-55 coiling defect was significantly reduced (but not eliminated) in unc-55; hbl-1 double mutants ( Figure 3I). The coiling defect was restored by transgenes driving hbl-1 expression in the D neurons (using either the unc-25 GAD or the unc-30 promoter) in unc-55; hbl-1 double mutants ( Figure 3I and Figure S3E),

as would be predicted if HBL-1 acts in VD neurons to PD-0332991 in vitro promote remodeling. Thus,

the imaging, electrophysiology, and behavioral assays all support the idea that hbl-1 is a functionally important UNC-55 target whose expression promotes ectopic remodeling of VD synapses in unc-55 mutants. The partial suppression and incomplete penetrance observed in the unc-55; hbl-1 double Rolziracetam mutants indicate that the hbl-1(mg285) mutation did not completely abolish remodeling of VD synapses. The persistent VD remodeling observed in double mutants could reflect residual hbl-1 activity in hbl-1(mg285) mutants, or the activity of other UNC-55 target genes ( Lin et al., 2003). Consistent with the latter idea, transgenic expression of hbl-1 in DD and VD neurons (with the unc-25 promoter) was not sufficient to cause ectopic remodeling of VD synapses ( Figure S3F). Thus, hbl-1 is unlikely to be the only UNC-55 target involved in D neuron remodeling. Thus far, our results show that hbl-1 promotes ectopic remodeling of unc-55 mutant VD neurons but that hbl-1 expression alone is not sufficient to cause VD remodeling. We next analyzed DD remodeling, which occurs in wild-type animals ( Walthall, 1990 and White et al., 1978). Prior to hatching, DD neurons form ventral NMJs, which can be identified as ventral UNC-57::GFP puncta. During the L1 stage, these ventral DD synapses are eliminated and new dorsal synapses are formed (visualized as dorsal UNC-57 or RAB-3 puncta; Figure 4A and Figure S4A).

Depolarizing prepulses suppressed firing even after short prepuls

Depolarizing prepulses suppressed firing even after short prepulse durations (<5 msec) that evoked only a single spike, whereas hyperpolarizing prepulses suppressed firing only after longer prepulse durations (>20 msec) (Figure 2B). Thus, the differences

in the time dependence on prepulse duration suggest that depolarizing and hyperpolarizing prepulses act by different mechanisms. As discussed above (see Introduction), an intrinsic mechanism that suppresses firing at high contrast should recover with a time course longer than the interval between periods of firing; in this way, firing in one period could activate a suppressive mechanism that would affect the subsequent period (i.e., >100 msec for recovery). We therefore examined the recovery

of suppression ZD1839 cost after depolarizing or hyperpolarizing prepulses. Both types of prepulse suppressed firing and required >300 msec buy CX-5461 for complete recovery (Figure 2C). The fitted half-maximum time constants for recovery were 182 msec and 195 msec for depolarizing and hyperpolarizing prepulses, respectively. Thus, both hyperpolarization and depolarization can suppress subsequent excitability and have the appropriate recovery time to contribute to contrast adaptation to physiological stimuli. We tested the influence of depolarizing and hyperpolarizing prepulses on the complete input-output function of the test-pulse response. We varied test-pulse amplitude to mimic different contrast levels (up to +480 pA). The current-firing (I-F) relationship during the test pulse was measured under control conditions

(prepulse, 0 pA) and in the two prepulse conditions (+400, −160 pA). The I-F relationships were relatively linear and could therefore for be characterized by a slope and an offset (Figure 3A). Both types of prepulse suppressed the firing by reducing the slope, indicating a reduction in gain (Figure 3B). However, there were different effects on the offset (Figure 3C). The depolarizing prepulse increased the offset, so that a larger test-pulse was required to evoke spiking. The hyperpolarizing prepulse decreased the offset, so that in most cases the firing near threshold was slightly enhanced by the prepulse, and the suppression of firing occurred primarily for the largest test pulses. Thus, hyperpolarizing prepulses suppress subsequent firing primarily for strong stimuli, whereas depolarizing prepulses suppress subsequent firing for all stimuli. We repeated the above experiment substituting different contrast levels for the test pulse: a spot (1 mm diameter) that decreased contrast by variable amounts (9%–100%). We varied the timing of stimulus onset so that lower contrast stimuli occurred earlier in time; this ensured that firing at all contrast levels would begin ∼25 msec after prepulse offset (see Experimental Procedures; Figure 3D).

, 2004 and Tobler et al , 2005) Predictive coding addresses a ge

, 2004 and Tobler et al., 2005). Predictive coding addresses a general challenge that an animal faces: developing an accurate model of the expected value of all

incoming inputs. Thus, predictive coding models can be applied beyond the context of reward prediction to cortical processing more generally. In fact, predictive coding was initially suggested as a model for visual perception (Barlow, 1961, Gregory, 1980 and Mumford, 1992), using a visual error code that preferentially encodes unexpected visual information. The key benefit of such a code, proponents suggest, is to increase neural efficiency, by devoting more neural resources to new, unpredictable information. By contrast to the single population of reward prediction error neurons, predictive coding in the massively hierarchical structure of cortical processing poses a series of challenges. If sensory neurons respond to prediction errors, there must exist other Volasertib price neurons to provide http://www.selleckchem.com/Wnt.html the prediction. Thus predictive coding models require at least two classes of neurons: neurons that formulate predictions for sensory inputs (“predictor” neurons, also called “representation” neurons; Summerfield et al., 2008 and Clark, 2013), and neurons that respond to deviations from the predictions (“error” neurons). Because sensory input passes through many hierarchically organized levels of processing (DiCarlo et al., 2012, Felleman and Van Essen, 1991, Logothetis and

Sheinberg, 1996, Desimone et al., 1984 and Maunsell and Newsome, 1987), a predictive model of sensory processing requires medroxyprogesterone an account of the interactions between prediction and error signals, both within a single level and across levels. To illustrate the idea, we provide our own sketch of a hierarchical predictive coding model. This proposal is a hybrid

of multiple approaches (Friston, 2010, Clark, 2013, Wacongne et al., 2012, de-Wit et al., 2010 and Spratling, 2010), seems to capture the essential common ideas, and is reasonably consistent with existing data. The key structural idea is that predictor neurons code expectations about the identity of incoming sensory input and pass down the prediction to both lower level predictor neurons and lower level error neurons. Error neurons act like gated comparators: they compare sensory input from lower levels with the information from predictor neurons. When the information that is being passed up from lower levels matches the information carried by the predictor neurons, the error neurons’ response to the input is reduced. This type of inhibition is the classic signature of predictive coding, “explaining away” predictable input (Rao and Ballard, 1999). However, when predictor neurons at a higher level fail to predict the input (or lack of input), there is a mismatch between the top-down information from the predictor neurons and the bottom-up information from lower levels, and error neurons respond robustly.

For criterion 2, the confidence interval was computed by using th

For criterion 2, the confidence interval was computed by using the variance of distance between gaze position in the Entity video and gaze position in the No_Entity video. We scored the character as attention grabbing (AG) when all three criteria were satisfied for at least four consecutive frames. If this was not satisfied after 25 frames (1 s) the character was scored as non-attention grabbing (NoAG). In the preliminary study, this procedure

identified 15 attention grabbing and 10 non-attention grabbing characters. For attention grabbing characters we parameterized the processing times (A_time), considering the first frame when all three criteria were satisfied, and the amplitude of the shifts (A_ampl), considering see more the shift VEGFR inhibitor of the gaze position at the end of the four-frame window (see Figure 2D). Our main SPM analyses (SPM8, Wellcome Department of Cognitive Neurology) utilized orienting efficacy parameters computed in the preliminary study to analyze fMRI data acquired during covert viewing of the videos. We also performed more targeted ROI analyses of the covert fMRI runs using parameters based on in-scanner eye movement recordings (see Supplemental Experimental Procedures), and used in-scanner parameters to analyze imaging data acquired during overt viewing of the videos (eye movements allowed

during fMRI). All analyses included first-level within-subject analyses and second-level (random effects) analyses for statistical inference at the group level (Penny and Holmes, 2004). The aim of the fMRI analysis of the No_Entity video was to highlight regions of the brain where activity covaried with the level of salience in the visual input, Idoxuridine areas where activity reflected the tendency of the subjects to pay attention toward/away from the most salient location of the image (efficacy of salience), and areas modulated by attention shifting irrespective of salience. The first-level models included three covariates

of interest: S_mean, SA_dist, and Sac_freq. Each model included also losses of fixation modeled as events of no interest, plus the head motion realignment parameters. The time series were high-pass filtered at 0.0083 Hz and prewhitened by means of autoregressive model AR(1). Contrast images averaging the estimated parameters for the two relevant fMRI runs (see Table S1 in Supplemental Experimental Procedures) entered three one-sample t tests assessing separately the effect of S_mean, SA_dist and Sac_freq at the group-level. The aim of the fMRI analysis of the Entity video was to identify regions showing transient responses to the human-like characters, and to assess whether the attention-grabbing efficacy of each character modulated these transient responses.

For example, the value-related vmPFC/mOFC BOLD signal observed in

For example, the value-related vmPFC/mOFC BOLD signal observed in experiments on willingness to pay (Plassmann et al., 2007 and Plassmann et al., 2010)

disappears when subjects are given no option to choose but instead are instructed on which response they should make. Perhaps more of a concern is that when experimental participants watch other individuals playing a public goods game without taking part themselves, the vmPFC/mOFC BOLD signal may reflect aspects of the expected value of choices for the other playing individuals (Cooper et al., 2010). One possibility is that vmPFC/mOFC BOLD signal reflects the value of choices to the individuals to whom the scanned participant’s attention is drawn; the vmPFC/mOFC signal in public good games is larger when the scanned participant’s attention is directed to the common good of the group by the experimental instructions. An alternative interpretation, however, might be that the vmPFC selective HDAC inhibitors signal recorded by Cooper et al. (2010) does actually reflect something about how rewarding the situation is to the subject. The vmPFC/mOFC signal may reflect the fact that the subject is likely to have “other regarding preferences”

(Fehr and Camerer, 2007 and Behrens et al., 2009) and is therefore unlikely to solely consider his or her own best interests when judging whether an action is rewarding but instead to naturally perceive choices SP600125 price as rewarding when they benefit others. out In contrast to the view that vmPFC/mOFC activity automatically reflects the value of options there is also evidence that vmPFC/mOFC valuation signals reflect a comparison between the values of different options that might be chosen (Boorman et al., 2009, FitzGerald et al., 2009, Basten et al., 2010 and Philiastides et al., 2010). In other words, even if value signals in vmPFC/mOFC appear to be automatically generated and present in the absence of choice they are closely tied to the guidance of decisions. For example, Boorman et al. (2009) showed that vmPFC/mOFC BOLD signal is positively correlated with the value of an option that a

subject chooses and negatively correlated with the value of an option that a subject rejects (Figures 3Bi and 3Bii). In other studies, however, this value comparison signal is not seen (Wunderlich et al., 2010). Nevertheless, even in the absence of a clear value comparison signal the value of both options is represented at the beginning of the choice period but only the value of the chosen option is represented at later stages in a trial (Wunderlich et al., 2010). A difficulty for an account of vmPFC/mOFC function emphasizing value comparison and decision-making is its activation in any experiment that does not require a decision from participants (Lebreton et al., 2009 and Cooper et al., 2010). Particularly intriguing is the finding that vmPFC/mOFC value comparison signals reflect the value of the chosen option minus the value of the unchosen option (Boorman et al., 2009).

, 2007; Robbins and Everitt, 1996; Wise, 1996) The VP receives G

, 2007; Robbins and Everitt, 1996; Wise, 1996). The VP receives GABAergic projections from the VS and, in turn, projects to many brain areas involved in control of motivation such as the ventral tegmental area (VTA), substantia nigra pars

compacta (SNc), and pars reticulata (SNr), thalamic mediodorsal nucleus (MD), and lateral habenula (LHb) (Haber and Knutson, 2010; Humphries and Prescott, 2010). We chose the VP as a first step to answer the question, because its activity should be more directly correlated with changes in the animal’s performance due to the close connectivity between the VP and motor output regions. It has been suggested that the VP may serve as a “limbic final common pathway” for processing of reward (Smith et al., 2009). In Pavlovian tasks, KU-55933 in vitro neurons in the rat VP responded to sensory stimuli that predicted an upcoming reward as well as to the reward itself (Smith et al., 2011; Tindell et al., 2004). Lesions, inactivations, and chemical manipulations of the rodent VP enhance or suppress Erastin reward-seeking behaviors (Cromwell and Berridge, 1993; Farrar et al., 2008; Johnson et al., 1996; McAlonan et al., 1993;

Smith and Berridge, 2005). Chemical activation of the monkey VP by local bicuculline injection induced stereotyped, non-purposive behavior (Grabli et al., 2004). In humans, bilateral lesions of the globus pallidus (GP) and the VP lead to a lack of motivation and pleasure (Bhatia and Marsden, 1994; Miller et al., 2006). Recent human imaging studies have demonstrated that the VP is activated during various kinds of motivational tasks associated with the primary (food and waters) and secondary (monetary gains) reward (Beaver et al., 2006; Pessiglione Oxalosuccinic acid et al., 2007). However, few studies have examined how individual VP neurons encode motivational/emotional states (Ito and Doya, 2009; Smith et al., 2011; Tindell

et al., 2004) and how they modulate goal-directed behavior. In our experiments we manipulated the value of an upcoming action by asking two macaque monkeys to perform a reward-biased saccade task. We found that many VP neurons showed differential activity encoding expected reward values. The role of the VP neuronal activity in motivating or demotivating the goal-directed saccade was supported by chemical inactivations of the VP in one of the monkeys. To examine the functional roles of the VP in reward-oriented actions, we recorded activity of single neurons in the VP while two monkeys (P and H) were performing a reward-biased memory-guided saccade task (Ding and Hikosaka, 2006; Kawagoe et al., 1998; Nakamura et al., 2008), in which reward size was associated with the direction of saccade (Figures 1A and 1B). A trial started with the appearance of a central point that the monkey had to fixate.

Gain fields for hand

and gaze position were accounted for

Gain fields for hand

and gaze position were accounted for separately in the model by the parameters gH and gG (see Experimental Procedures for more details about the model). The cell shown in Figure 3 was well fit by the model (r2 = 0.87) and had a weight parameter, w, of 0.03, which corresponds to a hand-centered reference frame and is consistent Dactolisib datasheet with the results from the separability analysis. A six-parameter hand-centered model with x = T-H fit the firing rates for this cell just as well as the full seven-parameter model (F test, p = 0.43; r2 = 0.87), whereas models with x = T-G (gaze-centered) and x = T (body- or screen-centered) fit the data significantly worse than the full model (r2 = 0.47 and r2 = 0.54 respectively, p < 0.00001

for both F tests). Figure 6 shows the distribution GSK1120212 datasheet of the weight parameter w across the population of recorded cells (n = 128). The median value was 0.04, and the modal bin was the one centered on w = 0 (hand centered). Consistent with other recent reports ( McGuire and Sabes, 2011), the population was not homogeneous and contained some gaze-centered cells (w∼ = 1) as well as cells with an intermediate reference frame (0 < w < 1). However, the overall trend in the population was toward a hand-centered representation, supporting the results from the SVD/gradient analysis. The hand-centered model fit as well as the full model in 38% of cells (F test,

p > 0.01), whereas the gaze-centered model fit as well as the full model in only 17% of cells. The full model fit better than either reduced model in 29% of cells and both reduced models fit as well as the full model in the remaining 16% of cells. The model uses a Gaussian function for fitting, which is appropriate for cells with a Sodium butyrate peaked response. Most of our recorded cells (108/128; 84%) had a response peak within the working range. The shape of the weights distribution when including only these cells was very similar to that for the entire population (Figure S3A), as was the distribution for the subset of cells with values of r2 greater than 0.6 (n = 75; Figure S3B). We found that the reach vector, or target position relative to the hand, is the principal representation in parietal area 5d during planning of reaches, and that there is a marked absence of coding for the position of the hand relative to gaze (Figures 4, 5, and 6). This hand-centered coding is distinct from the predominantly gaze-centered reference frame reported for the neighboring PRR (Batista et al., 1999; Buneo et al., 2002; Pesaran et al., 2006) and suggests that the two regions subserve different functions.

This raised questions about the relative

This raised questions about the relative U0126 ic50 positions of these two inputs just before EO. The overall “opposing gradient” pattern of innervation was also observed before EO (Figures 3A–3G). Of the 124 Thy1 eGFP pups with both retina and cortical labeling surgeries on P9, both inputs were successfully labeled on only one P11 DOV neuron with sufficient dendritic labeling to unambiguously identify it as a DOV neuron. We found retinal axons in close contact with the proximal dendrites and dorsal

somata of this neuron, whereas cortical axons were mostly restricted to the ventral portion of the soma (Figures 3F and 3G). This apparent difference in location of the cortical and retinal axons before and after EO in young adults suggests that cortical inputs move to dendrites and displace existing retinal terminals to more distal dendritic sites during high quality pattern vision. In support of such invasive

ability, it is only after EO that corticocollicular inputs become the primary inhibitor of dorsally directed sprouting of the ipsilateral retinal projection following an early contralateral retinal lesion (Colonnese and Constantine-Paton, 2001). GFP-labeled DOV neurons at P13, 1 day after EO, have abundant dendritic protrusions and appear “hairy” (Figures 4A–4D). Densities of spines and filopodia Angiogenesis inhibitor were examined across the dendritic arbor of developing DOV neurons, with dendrites classed by caliber rank. Filopodia (length > 3 width) have been characterized as new or particularly (-)-p-Bromotetramisole Oxalate dynamic protrusions, whereas spines (length ≤ 3 width) are more likely to contain matured, stronger, or stabilized synapses (see Supplemental Experimental Procedures). These criteria were used to quantify structural changes

indicative of synaptogenesis on dually innervated DOV neurons before (P11) and 24 hr after controlled EO (P13) as well as 4 days AEO (P16) and at least 20 days AEO (adult) (Figures 4E and 4F). Dendrites of all calibers had few filopodia at P11, but rapidly developed a high density of filopodia by P13 that were eliminated by P16 (Figure 4F). These changes reached significance on the thinnest and most abundant dendrites, caliber 3 and caliber 4. Significant changes in spine density were not observed with age (one-way ANOVA, p > 0.05, calibers 2, 3, 4). Between the youngest and oldest ages studied (P11 and “Adult”), there were detectable but small mean increases in both total dendritic branch length and the complexity of arbors (Figure S3). Small increases in apical dendritic complexity and length occurred proximal, but not distal, to the soma, suggesting that maturing cells added new synaptic space proximally. We tested whether the surge in filopodia at EO required visual experience by comparing P13 littermates whose eyes were opened (EO) or closed (EC) (Figure 5A).