Mice were placed in the center of an open-field arena (40 × 40 ×

Mice were placed in the center of an open-field arena (40 × 40 × 30 cm3) for 60 min and then habituated by daily placing in the same chamber for 10 min per day for three consecutive days. After the 3-day habituation, the general locomotion was assessed for a 30 min period. Specifically, we measured, 1) distance moved in the arena, 2) rearing, as the number of times the mice lifted both forepaws from

the ground, and 3) grooming, as the time that the mice groomed with its mouth and/or paws. Additional adult male mice at 90 ± 2 days old of age were used in the hidden platform versions of the Morris water maze tests using Stoelting poo-60135 as described before (Tu et al., 2010, see also Supplemental Experimental Procedures). Kinase Inhibitor Library supplier The forebrain was isolated from mice and placed

in RNAlater solution (QIAGEN) and tissues were homogenized using a TissueRuptor homogenizer (50/60 Hz) according Selleck Autophagy inhibitor to the manufacturer’s protocol. Total RNA was prepared from harvested hippocampal tissue with the miRNeasy Mini Kit (QIAGEN) and treated with an RNase-free DNase (QIAGEN) according to the manufacturer’s instructions. The RNA concentration was measured by spectrophotometer (DU 640; BECKMAN). RNA integrity was verified by electrophoresis in a 1% agarose gel. For microRNA expression profiling analysis, Mouse OneArray v2 (RmiOA.2) chips with 785 unique miRNA probes and 105 experimental control probe sets (Phalanx Biotech Group) were used. For gene expression profiling analysis, mouse whole genome OneArray microarray Resveratrol v2 (MOA-002) chips with 26,423 mouse genome probes and 872 experimental control probes were used. Datasets for single and dual channel experiments were analyzed with GeneChip Robust Multichip

Average (GC-RMA) and normalized using OneArray Software (Phalanx Biotech Group). All hybridized chips met standard quality control criteria were calculated as the fold-changes. The statistical relevance was expressed as the p values. The miscript cDNA synthesis kit (QIAGEN) was used for the reverse transcription reaction according to the manufacturer’s instructions. We used 1 μg total RNA, with 4 μl 5 × miscript reaction mix and 1 μl miscript reverse transcriptase. The total volume was 20 μl. Samples were incubated for 5 min at 25°C. All samples were then heated to 42°C for 30 min, and reactions were stopped by heating to 85°C for 5 min. For quantitative PCR (qPCR) all specific primers were selected using Beacon Designer Software (BioRad) and synthesized by IDT (Coralville, IA), as listed in Table S1. The PCR amplification of each product was further assessed using 10-fold dilutions of mouse brain cDNA library as a template and found to be linear over five orders of magnitude and at greater than 95% efficiency. All the PCR products were verified by sequencing.

We then estimated Granger causalities for each direction of influ

We then estimated Granger causalities for each direction of influence (OFC-to-amygdala and amygdala-to-OFC)

in the frequency domain (Geweke, 1982) from the AR parameters (Brovelli et al., 2004). We examined the evolution of Granger mTOR inhibitor causality by analyzing brief segments of LFP signal starting 0.5 s before CS onset until US onset (200 ms window, stepped by 50 ms, yielding 43 steps). The short window ensured that the LFPs within it could be considered stationary. For each step, the 200 ms LFP segments from trials of the same type (positive or negative) were concatenated separately and the parameters of the AR model for the resulting time series were estimated using the Nutall-Strand method (Schlögl, 2006). We fixed the AR model order to 50, and assessed model fit by testing for lack of residual correlations (Li and Mcleod, 1981). We determined the statistical significance INCB018424 price for Granger causality at each time-frequency bin using the frequency-domain test described by Breitung and Candelon (2006). To average Granger causality

values, we first normalized these values for each pair to the value estimated for the first time window (−0.5 to −0.3 s relative to CS onset). This was performed separately for each frequency bin between 0 and 100 Hz. For each pair and trial type, we only averaged data from pairs that yielded Granger causality values with four consecutive significant time bins (p < 0.01, spanning 350 ms). To compare the Granger causality in the two different directions of influence (Figure 9A), all trials of the reversal block were combined as described above. At each time bin, the Granger causality values for all frequencies from 5 to 100 Hz were averaged together. We determined the statistical significance of the difference between the two directions (OFC-to-amygdala and amygdala-to-OFC) using a permutation test (10,000 shuffles). To assess the effect of learning on the influence between the amygdala and OFC (Figures 9B and 9C), only the six first trials of each type (12 total) after reversal

and the last six next trials of each type in the experiment were used. Granger causality was computed for these two sets of trials, and we compared its relative magnitude in both directions during and after reversal learning. For each set of trials, the Granger causality values were averaged across pairs and trial types as described above. The difference between the mean Granger causality in the two directions was then compared for the during-learning and postlearning sets in the time domain (Figure 9B) by averaging across frequencies from 5 to 100 Hz; Figure 9C does this in the frequency domain by averaging across times from CS onset until the end of the trace interval. The significance of the difference between during-learning and postlearning was assessed by permutation test (10,000 shuffles).

The anesthetized mice were then moved to a sitting posture, with

The anesthetized mice were then moved to a sitting posture, with their heads fixed and their forelimbs hanging free (Figure 3A, center). With prolonged stimulus trains (500 ms), the forelimb tended to reach a final position within ∼300 ms and remain there for the duration of the stimulus. Stimulation

of Mab caused the contralateral forelimb to be raised and then brought learn more toward the midline, whereas stimulation of Mad typically produced rhythmic movements lower in space, often coupled with movement of the hindlimb (Figure 3B). These movements were reproduced in anesthetized mice where ChR2 was locally expressed using adeno-associated virus (Figure S2) and in awake, freely moving ChR2 transgenic mice stimulated within

Mab and Mad via optical fibers (Figures 3A and 3B, right; Movie S2). In both anesthetized and awake mice, the displacement of the limb from its starting position was buy Veliparib significantly greater when Mab was stimulated rather than Mad (Figures 3B and 3C). Although movement trajectories (Figure 3B) and displacements (Figure 3C) were clearly dependent on stimulus site for both awake and anesthetized mice, the speed profiles of Mab and Mad movements were nearly identical (Figure 3D). Movements evoked from each site were remarkably consistent from trial to trial, and the variability that they did exhibit had a temporal structure that depended on the site of stimulation (Figure S3). Increasing stimulus duration generally had little effect on movement map structure, despite changes observed in movement trajectories (Figure S4). Consistent with previous results from electrical stimulation (Ramanathan et al., 2006), modulating optogenetic stimulus intensity did not affect movement trajectories evoked by prolonged stimulation (Figure S5). These experiments complement the mapping study by exposing the distinct Cediranib (AZD2171) types of complex movement that

can be evoked from Mab and Mad by prolonged stimulation in both anesthetized and awake mice. To determine whether these complex movements require selective stimulation of layer 5B neurons, we compared optogenetic stimulation (500 ms train of 5 ms, 5 mW pulses at 100 Hz) with trains of electrical intracortical microstimulation (ICMS) targeted to layer 5 of cortex (500 ms trains of 200 μs, 100 μA pulses at 200 Hz) (Ramanathan et al., 2006). Given the differences between ICMS and optogenetic stimulation, we were surprised to discover that ICMS was able to closely reproduce the complex movements characteristic of transgenic or viral optogenetic stimulation of Mab and Mad (Figure 4A, Figure S2). In addition to their overlapping trajectories, movements evoked by either method had comparable peak displacements, time to peak, and angle from origin at peak displacement (Figure 4B).

(2012) showed that predicting the stimulus from population activi

(2012) showed that predicting the stimulus from population activity could be done just as well after replacing the firing rates of all their neurons with a few numbers summarizing the activation of each mode. Why would the brain waste valuable resources using a hundred neurons to encode a single number? Although this question cannot be answered at present, this type of organization has some remarkable similarities with some selleckchem long-hypothesized theories of cortical function, which we now describe. One of the most influential theories for cortical function is the “cell assembly hypothesis,” first proposed over half a century ago (Hebb,

1949; see Harris, 2005, for a more recent review). A cell assembly was hypothesized to be a group of neurons that are reciprocally connected by excitatory synapses, so that once a sufficient subset of the assembly fires, the whole assembly will be activated through mutual excitation. In Hebb’s original formulation, assemblies were sculpted by experience-dependent plasticity, with frequently coactivated neurons wired together through what is now called Hebb’s rule. The benefit of this scheme is that when an animal later experiences a stimulus that is similar but not identical

to the stimulus that created the assembly (such as a visual image that is partly occluded), the whole assembly will be reactivated, allowing the animal to respond as it would to the original stimulus. Later computational work made this idea precise by constructing formal models of selleck chemical recurrent network dynamics (e.g., Gardner-Medwin, 1976;

Hopfield, 1982). In these models, the stored assembly patterns heptaminol are “attractors”—stable activity patterns to which network activity evolves. The response modes described by Bathellier et al. (2012) are similar to attractors in their all-or-none nature, their discrete spatial patterns, and the fact that locally, only one mode can be activated at a time. Nevertheless, there are differences between the organization reported by Bathellier et al. (2012) and the simplest attractor models. First, the assemblies of superficial auditory cortex are spatially localized, unlike the disordered patterns typically stored in a Hopfield net; second, it is presumably possible for several spatially separated cortical assemblies to be active simultaneously (as illustrated in Figure 1C); and third, the number of assemblies expressed (1 assembly for at least 100 neurons) is much lower than the predicted capacity of most autoassociative networks (Tsodyks and Feigelman, 1988). Some of these discrepancies are rectified in a class of models known as “bump attractor” networks, in which localized recurrent excitation and lateral inhibition cause firing in localized groups of neurons (Amari, 1977). These models are often proposed as a mechanism to memorize continuous variables such as an animal’s location in space (McNaughton et al., 2006).

5 t test)  Similarly, measurements of frequencies and amplitudes

5 t test). Similarly, measurements of frequencies and amplitudes of mIPSCs in cells expressing GPHN.FingR-GFP (Figures 7H and 7I; f = 4.2 ± 0.5 s−1, A = 14.1 ± 1.0 pA, n = 8 cells) were not significantly different from comparable measurements in control cells (f = 4.3 ± 0.5 s−1, A = 13.5 ± 1.1 pA, n = 9 cells; p > 0.1 t test). Thus, our results Selleckchem Screening Library indicate that expressing PSD95.FingR-GFP and GPHN.FingR-GFP does not cause changes in synaptic physiology and has no effect on the number or neurotransmitter receptor content of individual synapses. To determine

whether GPHN.FingR-GFP signals represent functional inhibitory synapses, we measured IPSCs evoked by GABA photolysis at individual green punta. Hippocampal CA1 pyramidal neurons were transfected with GPHN.FingR-GFP and TdTomato to visualize inhibitory synapses and neuronal structure (Figure 8A). Two-photon GABA uncaging 0.5 μm away from puncta of GPHN.FingR-GFP triggered IPSCs. IPSC amplitude diminished when uncaging

occurred further away from the dendrite, demonstrating that IPSCs originated from the activation of receptors localized in dendrites of the recorded neuron (Figures 8B and 8C). When GABA was photoreleased on the dendritic shaft at locations where GPHN.FingR-GFP was present, robust IPSCs were evoked. However, GABA photorelease at two locations, one in a dendritic spine and a second on a dendritic shaft, where there was no GPHN.FingR-GFP signal elicited small or negligible IPSCs (Figures 8D and 8E). These data confirm that GPHN.FingR-GFP does indeed label functional Rutecarpine inhibitory synapses. PSD95.FingR and GPHN.FingR label their endogenous target proteins in dissociated check details neurons, as well as in neurons in slices. To determine whether FingRs can be used to label endogenous proteins in vivo, we transfected PSD95.FingR-GFP into neurons in mouse embryos in utero using electroporation and then assessed expression at approximately 7 weeks of age. Images of dendrites of layer V cortical pyramidal neurons coexpressing HA-mCherry and taken from unstained sections cut from perfused, fixed brains clearly show punctate patterns of GFP expression consistent

with labeling of PSD-95 (Figures 9A and 9B). In addition, lower-magnification images show labeling of layer V and layer II/III pyramidal neurons that is also consistent PSD-95 labeling (Figures 9C and 9D). Finally, an image obtained from a living animal of PSD95.FingR-GFP expressed in an apical tuft from a cortical pyramidal neuron (Figure 9E) demonstrates that PSD95.FingR-GFP can be imaged in vivo. In this paper we demonstrate that Fibronectin intrabodies generated with mRNA display (FingRs) can be used to visualize the localization of the endogenous postsynaptic proteins Gephyrin and PSD-95 in living neurons without affecting neuronal structure and function. FingRs represent a substantial improvement over traditional antibody approaches that, in general, require that cells be fixed and permeabilized prior to staining.

3% Triton X-100 (PBST) and 4% bovine serum albumin (BSA, Sigma) f

3% Triton X-100 (PBST) and 4% bovine serum albumin (BSA, Sigma) for 1 day at 4°C; (2) a biotinylated antirabbit IgG solution (1:1000, Vector Laboratories) in PBST; and (3) an ABC-peroxidase

solution (1:1000, Vector Laboratories) both for 60 min at room temperature. Finally, sections were stained using 3,3′-diaminobenzidine-4 HCl and Nickel solution (DAB-Ni; Vector Laboratories) in order to obtain dark purple staining. Four washes in PBST were performed between each step. The c-Fos-stained sections were incubated in a goat antiserum to orx/hcrt (1:4000; Ku-0059436 price Santa Cruz) in PBST/BSA 4% for 2 days at 4°C. Amplification steps were similar to those described above but the final step was performed in DAB solution without nickel in order to obtain brown staining. Finally, the sections were mounted on slides, dried, and coverslipped with permaslip. Orx/hcrt-positive and orx/hcrt+c-Fos-positive neurons were counted by an investigator blind to experimental conditions, within at least six coronal sections per animal evenly spaced throughout the rostrocaudal extent of the lateral hypothalamus (Bregma −1.06 to −2.14) to avoid rostrocaudal bias. Colocalization of c-Fos and orx/hcrt immunostaining was detected using a high magnification objective.

No significant differences were found in the number of c-Fos-positive orx/hcrt neurons between vehicle injection experiments. This work was funded primarily by the European CHIR 99021 Research Council (ERC FP7 Starting Grant to D.B.). M.M.K. was also supported by Osk. Huttunen Foundation (PhD studentship). L.d.L. was supported by the NIH, and A.A. by the NIH, FRS-FNRS, and NARSAD. L.F. was funded by the

Lundbeck Foundation and the MRC in UK and Denmark. We thank Dr. Methisazone Peter Voshol and Sylvia Osborn of mouse core facilities at Medical Research Council Centre for Obesity and Related Metabolic Diseases (MRC CORD) for assisting with experiments in Figure 2. MMK performed and designed most experiments, analyzed data, and contributed to writing of the paper. J.A.-S. contributed to the experiments shown in Figure 2. A.A. and L.d.L. contributed to the experiments shown in Figure 3. L.F. and L.T.J. created and provided orx/hcrt-eGFP mice used in the project. DB conceived the idea, obtained funding, coordinated the project, and wrote the paper. “
“Mammalian central neurons rely on the dynamic interplay between transmitter receptors and voltage-gated ion channels on their dendrites for signal processing. For example, the A-type voltage-gated K+ channels (IA) on the dendrites of CA1 hippocampal pyramidal neurons regulate neuronal signaling by filtering fast synaptic potentials and regulating action potential back propagation, synaptic integration and long-term potentiation (LTP) (Kim and Hoffman, 2008). This IA derives primarily from Kv4.2 (Birnbaum et al., 2004, Kim et al.

This caused the tail region to relax and lose its curvature

This caused the tail region to relax and lose its curvature.

A second more telling experiment used the genetically encoded calcium reporter GCaMP3 to show that the body wall muscles are more active on the inside of the curve than on the outside of the curve. They then did something rather clever. They used a pneumatic microfluidic device to change the curvature of the trapped worm and examine what happens to more posterior segments. Rapidly changing the channel curvature from a dorsal to ventral bias, or vice versa, resulted in a corresponding change in the curvature of the posterior body ( Figure 1B). From these experiments, they concluded that the body of the worm senses curvature and is able to relay this information to more posterior segments, which then follow suit. What is the cellular mechanism that allows worms to sense body curvature and propagate the bending movement to more posterior segments? Doxorubicin manufacturer Could the body wall muscles themselves propagate this proprioceptive signal,

given that they are coupled by gap junctions? A combination of classical genetics and optogenetic manipulation was employed to rule this possibility out. Mutant worms that lack functional gap junctions between muscle cells were still able to sense and propagate bending. There Cytoskeletal Signaling inhibitor was also no change in the curvature of the posterior body when muscles located within the channel were hyperpolarized with NpHR, nor did localized channelrhodopsin-induced contraction of these muscles cause the flanking body segments to bend either ventrally or dorsally. This makes it highly unlikely that the

muscle cells themselves signal stretch or curvature to each other. What about motor neurons, as these cells have elongated cellular processes that could potentially function as a stretch organ? Not surprisingly, expression of NpHR in all cholinergic neurons (A- and B-type) abolished the bending of the body, while mutations that alter the dorsal B-type motor neurons caused the ventral bias in the bending. Most tellingly, inactivation of B-type motor neurons as opposed to A-type or D-type motor neurons disrupted the correlation between the curvature of the trapped region and more posterior segments, indicating that the worms can no longer sense curvature. Montelukast Sodium Using calcium imaging, they observed a very close correlation between bending and the activation of the B-type motor neurons. The evidence, while largely correlative, clearly points to B-type motor neurons being the cellular substrate for this proprioceptive signal. A number of questions still remain. Is the proprioceptive signal transferred directly from motor neuron to motor neuron? One way of testing this might be to inactivate or ablate a single B-type motor neuron in the chain and ask if posterior propagation of the signal is disrupted.

chagasi To our knowledge, this is the first morphometrical appro

chagasi. To our knowledge, this is the first morphometrical approach of inflammation and the first report of occurrence of apoptosis in inflammatory cells in vivo involving natural infection with L. (L.) chagasi. A total of 16 positive and six negative-tested dogs previously examined for VL were used. Macroscopic skin lesions due to secondary infections in the pinna region were considered as criteria of exclusion. To confirm Autophagy inhibitor L. chagasi infection, blood samples were taken to detect anti-Leishmania antibodies by IFA and ELISA and needle aspiration of the popliteal lymph node and bone marrow was performed in each dog, to

direct visualization of the parasite and culture. Once confirmed the infection, they were euthanatized and submitted to necropsy for sample collection. Before fixation of the samples (spleen, liver, skin and lymph nodes), imprints of the cut surface on cleaned slides were taken to direct visualization of the parasite and confirm visceralization of the infection. Myelograms and imprints of popliteal lymph nodes, spleen, liver and skin were stained with Giemsa, for parasitological visualization ( Mikel, 1994).

Aspirates from spleen, liver, bone marrow and lymph node were also cultured for promastigotes in NNN-phase Schneider’s liquid medium. Polymerase Chain Reaction was performed to detect parasites only in pinna skin extracted DNA, using a target sequence of Leishmania donovani complex. Anti-Leishmania antibodies were selleck detected in all infected animals, the titers ranging from 1:40 through 1:640. All infected animals (symptomatic and asymptomatic) were positive in PCR and at least two of the three parasitological tests (Giemsa,

culture and immunohistochemistry) in different organs. Animals regarded as non-infected controls had negative results in all tests, including PCR. Efforts were made to avoid all unnecessary distress to the animals. Housing, anesthesia and all procedures concurred with the guidelines established by our local Institutional Animal Care and Use Committee that also reviewed and approved this work (CETEA, Universidade Federal de Minas Gerais, protocol n° 198/2007, approved on 03/27/08). Eight VL-positive Sitaxentan dogs (by serological and parasitological analysis) were used in this experiment, with the exception of the control group. Animals were divided into three groups: (a) Eight VL-positive animals with clinical signs of the disease; (b) eight positive animals, with no clinical signs; and (c) six VL-negative control animals. Standards used to group the animals followed the Pozio et al. (1981) classification. The animals were tranquilized with Acepromazine 1%, anesthetized with Sodium thiopental 2.5%. After this procedure, the animals were euthanatized with an overdose of sodium thiopental 7.5% (75 mg/kg) for further pos-mortem examination. Skin fragments from the pinna region were collected and routinely processed for histological analysis.

The flies remained in a 32°C incubator at 70% humidity for a pred

The flies remained in a 32°C incubator at 70% humidity for a predefined period. In all cases, flies were returned to 23°C at least 15 min prior to a retrieval test. Cold-shock experiments were performed by transferring trained flies to a precooled glass vial in an ice-water bath (∼0°C).

The flies were anesthetized almost immediately and remained in the bath for 2 min and then returned to a food vial at 23°C. Appetitive olfactory memory experiments were performed as described (Krashes and Waddell, 2008). Briefly, flies were first starved for 16–24 hr prior to appetitive training on 0.8% nonnutritive agar. The CS+ and CS− odors and their concentrations were as described above for aversive conditioning. Flies were first exposed to the CS− odor for 2 min in Capmatinib cell line a tube containing a dry filter paper previously saturated with water followed by 30 s of air. The flies were then transferred to a second tube containing a dry filter paper previously saturated with a 2 M sucrose solution and exposed for 2 min to a second odor (CS+). After conditioning, flies were maintained in nonnutritive agar vials at either

23°C or 32°C. Memory testing was performed as described above following aversive conditioning. http://www.selleckchem.com/products/Bafilomycin-A1.html Acquisition curves for Canton-S and damb mutants were conducted as follows. Flies were exposed to 1, 2, 3, 6, or 12 shock pulses evenly distributed over 1 min of CS+ exposure such that the last shock pulse (or the only shock pulse) was always given at the last 1.25 s of odor exposure. After 30 s of air and the 1 min CS− exposure, flies were immediately tested for memory recall. Reversal-learning experiments were conducted by training with an odor-pair contingency (for example, CS+ = OCT, CS− = MCH), waiting 1 min, training

to the reverse odor-pair contingency (for example, CS+ = MCH, CS− = OCT), and immediately testing memory why performance. If flies remember both contingencies equally, then one expects a PI of zero, while a positive PI would suggest a stronger memory performance with respect to the reversal contingency. Odor avoidance tests were conducted by allowing naive flies to choose for 2 min in a T maze between an odor on one side and fresh air on the other. An avoidance index is calculated as the ([number of flies in fresh air arm] – [number of flies in odor arm]) / (number of flies in both arms). Shock avoidance tests were conducted by allowing naive flies to choose for 2 min in a T maze between one arm containing an electrified copper grid (same as used for training above) and the other arm containing a nonelectrified copper grid. The side that is electrified is alternated to account for any side-to-side T maze bias. TH-gal4 virgin females were crossed to male UAS-GCaMP3.0, UAS-RFP flies.

In socially isolated animals one to two neurons were produced for

In socially isolated animals one to two neurons were produced for every NSC in the total dentate exhibiting a linear stoichiometry unlikely to be associated with a transit-amplifying cell. Given that many

adult-born neurons undergo apoptosis, but there is no direct way to assess cell death over time, we examined whether our behavioral interventions could affect cellular survival to SB431542 datasheet account for differences in lineage trajectories (Figure S4A). We found that social isolation did not decrease cellular survival and that enrichment increased survival (Figure S4B) by a magnitude that could not account for the observed lineage gains (Figure 7J). We also assessed the numbers of cells undergoing apoptosis at time of sacrifice in each group in this study (Figures S4C–S4F). We did not detect differences in the number of apoptotic cells between our behavioral interventions (Figure S4C). Moreover, the number of cells undergoing apoptosis did not correlate with accumulation of EYFP+ cells across the groups (Figure S4D). We also did not detect differences in the number of cells undergoing apoptosis between the different age groups used in this study (at different time points) (Figures S4E and S4F). Thus, social isolation promoted accumulation of EYFP+ NSCs and instructed NSCs toward a linear relationship Selleckchem TSA HDAC with their terminal neuronal progeny. EEE promoted accumulation of EYFP+ neurons and instructed NSCs toward a variable relationship

with their terminal neuronal progeny. Here we report the first system that allows for inducible cre-mediated recombination in adult hippocampal radial GFAP-expressing NSCs, but not GFAP−Tbr2-expressing neural progenitors. Surprisingly, Thymidine kinase we observed an increase in the absolute number of EYFP+ NSCs over time. In the adult brain, radial astrocyte-like stem cells are currently considered to be “quiescent,” self-renewing, and are not thought to accumulate (Encinas et al., 2006). One recent lineage study suggested that NSCs undergo a limited and constant number of asymmetric divisions resulting in self-renewal only, followed by differentiation

into terminal astrocytes suggesting that NSCs are depleted with age (Encinas et al., 2011). However, an inherent limitation of genetically defined lineage studies is the potential for functional heterogeneity within the genetically defined stem cell. NSC heterogeneity was recently proposed in a report describing a nonradial multipotent cell with astrocyte-like properties (Lugert et al., 2010). While the lineal relationship of these horizontal cells to radial NSCs remains to be established, more horizontal cells were present in animals subjected to experimental seizure protocols. The latter finding suggests a stem cell dormancy hypothesis that is further supported by historical observations that even in aged animals, when baseline proliferation is minimal, EEE induces a robust increase in neurogenesis (Kempermann et al., 1998).