Brains were quickly removed and placed into ice-cold sectioning solution. A block of brain tissue was glued to the stage of a Campden Vibroslice for slicing while immersed in ice-cold sectioning solution. After a 1 hr recovery period at 35°C in ACSF, slices were used for recordings within ∼8 hr. ACSF was continuously gassed with 95% O2 and 5% CO2 and contained (in mM): 125 NaCl, 2.5 KCl, 2 MgCl2, 2 CaCl2, 1.2 NaH2PO4, 21 NaHCO3, and 1 glucose (except where indicated otherwise). Sectioning solution contained (in mM): 95 NaCl, 1.8 KCl, 1.2 CaCl2, 26 NaHCO3, 1.2 KH2PO4, 7 MgSO4, 50 sucrose,

and 15 glucose. Two types of intracellular (pipette) solutions were used. “High-Cl” pipette solution contained (in mM): 130 KCl, 0.1 EGTA, 10 HEPES, 5 K2ATP, 1 NaCl, 2 MgCl2 (pH 7.3) with KOH. “Low-Cl” pipette PFI-2 nmr solution contained (in mM): 120 K-gluconate, 10 KCl, 0.1 EGTA, 10 HEPES, 5 K2ATP, 1 NaCl, 2 MgCl2 (pH 7.3) with KOH. Liquid junction potential for the low-Cl solution was estimated to be 10 mV and has not been subtracted from the measurements. The low-Cl solution, which mimics the ionic composition in a typical central neuron, was used in all experiments except

those in Figures 3A–3C (where we see more used high-Cl solution) and Figure 1H (where we used ACSF). All AAs used were L-isoforms and glucose was D-(+)-glucose. The concentrations of AAs in the control and “low” AA mixes are given in Table S1 (called “AA mix” and “low AA mix,” respectively). Purity of the AA mix was examined by ion-exchange chromatography followed by ninhydrin analysis (Department of Biochemistry Analytical Facility, University of Cambridge), where threshold for detection was 0.5 μM. No GABA or glutamate contamination was detected and glycine concentration was within 10% of the intended value. Classification of amino acids as essential Casein kinase 1 or nonessential in Figure 3B was based on Gietzen and Rogers (2006). In the upper panel of Figure 3D, we omitted cysteine

because it is toxic and not found in CSF (Choi et al., 1999 and Nishimura et al., 1995), glutamate to avoid excitation through glutamate receptors, and glycine because at high concentrations it may modulate orx/hcrt neurons through glycine receptors (Karnani et al., 2010). In the upper panel of Figure 3D, other AAs listed in Table S1 were present in 100 μM concentration making the total concentration for essential AA mix 1.1 mM, and nonessential AA mix 0.6 mM. In the lower panel of Figure 3D, the concentrations for AAs were from “AA mix” in Table S1. “FA mix” contained (in μM): 5 oleic acid, 5.4 palmitic acid, and 1.8 palmitoleic acid (Oomura et al., 1975 and Wang et al., 2006).

Panella et al. (1997) reported LC50/90 for (+)-terpinen-4-ol for I. scapularis. The concentrations resulting in 50% lethality (LC50) for R. (B.) microplus larvae ranged from 1.31 mg/mL (LGRA-201) to 4.34 mg/mL (LGRA-108), and the LC90 values ranged from 2.18 mg/mL (LGRA-201) to 6.02 mg/mL (LGRA-109) ( Table 3). These values demonstrate the high efficiency of the L. gracilis PI3K inhibitor essential oil for the control of

ticks along with the efficiency of their major components carvacrol (0.22 mg/mL) and thymol (3.86 mg/mL). The essential oil isolated from the LGRA-201 genotype proved to be the most lethal to tick larvae, with high mortality rates observed even at low concentrations. One possible explanation for this finding is the presence of carvacrol as major component and synergic effect with other monoterpenes, such as α-thujene, α-terpinene and γ-terpinene. Similarly, by investigating the effect of the essential oil of Lippia javanica in several

Boophilus subgenus, Madzimure et al. (2011) observed high efficiency of the essential oil in both larvae and adults. The observed patterns for lethal concentrations in engorged females were similar to those observed in larvae. However, LC50 for genotype LGRA-106 (4.66 mg/mL) and LC90 for genotype LGRA-201 (8.87 mg/mL) indicated higher efficacy relative to the other samples against engorged females (Table 3). With regard to the major components, carvacrol was found to have superior effect, with high lethality PFT�� molecular weight even at low concentrations. Similarly, Cetin et al. (2010) obtained LC50 of 3.18 mg/mL using pure carvacrol in adults of the Mediterranean tick Hyalomma marginatum. The use of natural products as acaricides may represent an important alternative for the control of animal parasites since

they are rich sources of bioactive compounds that are biodegradable, and potentially suitable for use as pesticides. The present findings demonstrate that L. gracilis essential oil may be used as a natural acaricide. Thymol and carvacrol are the major compounds in L. gracilis essential oil and may act synergistically to produce the acaricidal action against R. (B.) microplus observed. The authors wish to acknowledge CNPq, FAPITEC/SE and CAPES for supporting funds. “
“Trypanosoma theileri belongs to the however subgenus Megatrypanum. It was first described in cattle by Theiler, Laveran and Bruce in 1902 ( Hoare, 1972). This species is a cosmopolitan parasite of cattle and may occur with a high incidence. There is increasing evidence of immunosuppression involvement and association with a concomitant disease ( Doherty et al., 1993). However, its life cycle is not fully understood. The vectors are Tabanidae and Hyalomma anatolicum anatolicum. T. theileri in tabanids is typically characterized by stercorarian transmission ( Böse and Heister, 1993 and Latif et al., 2004). An experimental rodent model has not been established. The epimastigote and large trypomastigote forms can be revealed in peripheral blood. T.

In the same study, those who would later develop schizophrenia (“converters”) could be distinguished from the nonconverters on the basis

of smaller gray matter volume mainly in limbic and temporal areas. These findings may support biological models positing progressive cortical volume loss as a risk factor ATM inhibitor for schizophrenia (Wood et al., 2008). Biomarkers derived from pattern classification do not come with clear cut-off points and depend strongly on the experimental parameters (e.g., numbers of scanned voxels) and analytical approches (e.g., the algorithm used for feature selection), and their practical relevance therefore needs to be demonstrated in multicenter studies, where the prediction accuracy of a template derived from one scanner is tested in data sets from others (Klöppel et al., 2008). Such confirmation in independent test samples is also needed to overcome doubts about the prediction estimates obtained through cross-validation in small samples (Isaksson et al., 2008). However, based on the promising results obtained so far, it can reasonably be expected that pattern classification of brain imaging data, in combination with clinical and psychometric data, will improve our ability to predict the course of psychiatric diseases. Although the reliability of structural

imaging measures is high on the same scanner, it is insufficient when tested IOX1 cost across scanners (Kruggel et al., 2010). However, improvements are to be expected

from wider use of high-field scanners with better image quality and segmentation results. Replication is also likely to be better if at least the field strength is kept constant across sites. The successful discrimination of AD patients from controls in a multicenter study of structural imaging data is promising in this respect (Klöppel et al., 2008). Less information is available about the reliability of specific functional imaging measures, because these would many in principle have to be computed for each individual cognitive paradigm. The literature on reproducibility of task-related activation converges to report consistency in the qualitative activation patterns, but considerable intraindividual variability, across scanning sessions (Gountouna et al., 2010) (Table 1). We are thus still far away from fMRI-based biomarkers at the individual level. The situation is similar for resting state measures, which have been too heterogeneous across individuals to allow for the development of stable biomarkers of disease (Greicius, 2008). However, recent work on graph theoretical metrics of functional connectivity has yielded promising results for the intraindividual reliability of some metrics (Braun et al., 2012). A first step toward the development of biomarkers from resting state activation metrics would thus be to achieve agreement on standardized analysis procedures based on the measures with the highest reproducibility.

In contrast, neither the Munc13-1W464R mutation nor the infusion of the CaM-inhibitory peptide in WT or Munc13-1W464R calyces had any deleterious effect on the recovery time course of the slowly releasing SV pool (Figure 3E). A reduced recovery rate of SV pools in Munc13-1W464R calyces was also evident when monitoring SV fusion by means of presynaptic membrane capacitance measurements, although the effect was less prominent, since this method reports the sum of fast and slow components (Figure S2). As elevations of presynaptic [Ca2+]i, e.g., upon changes in Ca2+ influx, strongly influence the recovery

of releasable SV pools (Dittman and Regehr, 1998; Sakaba and Neher, 2001; Stevens and Wesseling, 1998; Wang and Kaczmarek, 1998), we compared amplitudes of presynaptic Selleck KU-55933 Ca2+ currents resulting from the depolarizing pulses between WT and Munc13-1W464R mutant calyces but found no significant differences (WT, 1238 ± 79 pA, n = 6; Munc13-1W464R, 1283 ± 56 pA, n = 6; p > 0.05). Likewise, no differences were observed in the recovery time course of presynaptic Histone Methyltransferase inhibitor Ca2+ currents, as the ratios between the Ca2+ current amplitudes triggered by the second versus the first depolarization stimulus were identical for all interstimulus intervals (Figure 3C). These data show that in young calyx synapses the W464R mutation in Munc13-1 selectively affects the recovery of the

fast releasing SV pool, much like CaM inhibitors do, indicating that the Ca2+-CaM effect on releasable SV pool refilling is mediated by Munc13-1. The lack of CaM binding to Munc13-1W464R in the KI mutant does not appear to affect presynaptic Ca2+

channels, which are known to bind CaM (DeMaria et al., 2001; Lee et al., 1999; Peterson et al., 1999; Zühlke et al., 1999). Calyx of Held synapses undergo a structural and functional many refinement during postnatal development that transforms these synapses into fast and reliable relays. These developmental modifications include changes in SV pools, release probability, postsynaptic receptor desensitization, and expression of Ca2+ binding proteins (Crins et al., 2011; Erazo-Fischer et al., 2007; Sonntag et al., 2011; Taschenberger et al., 2002; Taschenberger et al., 2005; Taschenberger and von Gersdorff, 2000; Wang et al., 2008). In light of these changes, we decided to study the recovery rates of the two SV pools and the dependency of the recovery rates on CaM in more mature WT and Munc13-1W464R calyces (P14–P17). We measured the recovery of the fast and slowly releasing SV pools following their depletion by a 50 ms depolarizing pulse in P14–P17 calyces under the same conditions as with P9–P11 calyces (see Figure 3). The cumulative release in WT calyces of P14–P17 animals exhibited two components (τ1 = 1.3 ± 0.5 ms, 60% of the total fit; τ2 = 11.

Based on our findings, we propose the following scheme for this visuo-auditory cross-modal modulation (Figure 8C). Ipsilateral visual inputs can click here evoke bursting activity in hypothalamic dopaminergic neurons, possibly leading to dopamine secretion around the area of VIIIth nerve-Mauthner cell circuits, and then exert D1R-dependent neuromodulatory actions within a time window of a few hundred milliseconds on both the VIIIth nerve and its synapses on the

Mauthner cell. These actions include a reduction of spontaneous spiking activity and resultant increased S/N ratio of sound-evoked spiking activity in the VIIIth nerve as well as an increased efficacy of VIIIth nerve-Mauthner cell synapses. These effects cooperatively enhance the sound-evoked responses of Mauthner cells, leading to the enhancement of auditory C-start escape behavior. Thus, by addressing cross-modal modulation from behavioral level to circuit and synaptic level, our study illustrates a cooperative neural mechanism

for visual modulation of audiomotor processing, and reveals a role of dopaminergic system in cross-modal modulation. This 17-AAG nmr two-step cooperative mechanism, i.e., decreasing presynaptic spontaneous activity and increasing downstream synaptic efficacy, represents an efficient strategy to improve signal detection. Obviously, increasing synaptic efficacy alone can increase neural responsivity to sensory stimuli. However, it also inevitably amplifies noise responses, which could be generated by background sensory input or presynaptic spontaneous activity, resulting in increased energy consumption. On the other hand, decreasing spontaneous activity is capable of reducing noise response and thus increases S/N ratio (Foote et al., 1975; Hestrin, 2011; Hurley et al., 2004; Kuo and Trussell, 2011). To our knowledge, the coexistence of these two cooperative mechanisms in single neural circuits has not yet been experimentally

demonstrated. In the present work, we found that decreasing presynaptic noise and increasing downstream synaptic efficacy take place concurrently to enhance the detection of auditory signals. With a preceding light flash, the spontaneous spiking activity all of VIIIth nerves is significantly suppressed, whereas its sound-evoked activity is less affected. Thus the S/N ratio of sound-evoked spiking activity in the VIIIth nerve is increased by the preceding flash. Besides the increase in S/N ratio, the reduction in presynaptic spontaneous activity may also indirectly increase the efficacy of downstream synaptic transmission by partially removing presynaptically originated short-term depression of sound-evoked responses (Hestrin, 2011; Kuo and Trussell, 2011). This contribution to increase in synaptic efficacy can be limited, because the low spontaneous firing rate of the VIIIth nerve (see Figure 4) restricts the degree of short-term depression.

For VAMP7 knockdown, two constructs were used: VAMP7 KD3 5′-CTGAAGCATCACTCCGAGATTCAAGAGATCTCGGAGTGATGCTTCAG-3′ and VAMP7 KD4 5′-CTGAAAGGCATCATGGTCATTCAAGAGATGACCATGATGCCTTTCAG-3′.

In all cases, shRNA sequences were inserted into Xhol through Xbal cloning sites in the L307 lentiviral transfer vector, downstream of the human H1 promoter. Lentiviruses encoding pHluorin-tagged syb2, VAMP4, vti1a, VAMP7, mOrange-tagged syb2, and all shRNA constructs were prepared by transfection of human embryonic kidney (HEK) 293-T cells with FUGENE 6 and necessary viral coat and packaging protein constructs (pVSVG, pRsv-Rev, and pPRE). Three days selleck chemicals llc after transfection, virus www.selleckchem.com/products/chir-99021-ct99021-hcl.html was harvested from HEK293-T cell-conditioned media and added to neuronal media at 4 DIV. Lentiviral constructs to decrease expression of all four isoforms of the Doc2 protein family (Doc2A, Doc2B, Doc2G, and rabphilin) were a gift of Dr. Thomas C. Südhof (Stanford University) (Pang et al., 2011). Electrophysiological experiments were performed on dissociated hippocampal neurons as in Nosyreva

and Kavalali (2010) (see Supplemental Experimental Procedures for further details). Reelin was prepared and purified as described previously (Beffert et al., 2002) (see Supplemental Experimental Procedures for further details). Single-wavelength experiments were performed using an Andor iXon+ back-illuminated EMCCD camera using MetaFluor 7.6 software as described previously (Leitz and Kavalali, 2011) (see Supplemental Experimental Procedures for further details). Dual color experiments were performed using a Zeiss LSM510 confocal microscope using LSM5 software as described previously (Ramirez et al., 2012 and Raingo et al., 2012) (see Supplemental Experimental Procedures for further details). All error bars represent SEM and all statistical analyses were done using Microsoft Excel Software or

Sigma next Plot (see Supplemental Experimental Procedures for further details). We thank Drs. Megumi Adachi, Elena Nosyreva, and Catherine Wasser for discussions and comments on the manuscript. We also thank Brent Trauterman for his excellent technical assistance. We are grateful to Drs. Mikhail Khvotchev and Yildirim Sara for their insight at early stages of this project. This work was supported by National Institutes of Health grants MH066198 (E.T.K.), NS075499 (E.T.K.), T32 NS069562 (J.L.), MH070727 (L.M.M.) and HL063762 (J.H.) as well as funding from the from the Brain & Behavior Research Foundation (L.M.M. and E.T.K.) and International Mental Health Research Organization (L.M.M.). “
“At a synapse, neurotransmitters are released by Ca2+-triggered synaptic vesicle exocytosis (Katz, 1969) that is mediated by synaptotagmins (Südhof, 2012).

003 ± 0.004 ΔG/R [±SD] in spines, n = 22, 4 cells; 0.002 ± 0.002 ΔG/R in spiny branchlets, n = 18, 4 cells). The average spatial profile of the CFCT was obtained by pooling data from 13 cells. In the smooth dendrites, the CFCT remained constant up to ∼70 μm from the soma and decreased markedly in more distal parts (Figure 1E).

Half-maximum occurred at 91 μm from the soma with a steepness of 18 μm (exponential space constant of the logistic fit). In contrast, the amplitude of the CFCTs in spiny branchlets and in spines decreased approximately exponentially with distance from the soma (space constant; λ = 54.5 μm) (Figure 1F). This spatial profile of calcium influx is reminiscent of the electrotonic distribution of membrane potentials in Purkinje cells upon proximal depolarization (Roth and Häusser, 2001), suggesting that calcium

transients result from electrotonic Vorinostat activation of calcium channels in spiny dendrites. In Purkinje cells of Cav3.1 knockout (KO) mice, lacking the main T-type subunit, the amplitude of the CFCTs was reduced to 31% of wild-type (WT) mice (n = 23 cells, p < 0.001) in smooth dendrites and to 25% of WT (n = 24 cell, p < 0.001) in spines and spiny branchlets Enzalutamide mw (Figures 1G and 1H). In contrast, the CFCTs were not significantly inhibited in Cav2.3 KO mice lacking R-type calcium channels (Figures 1G and 1H). The role of Cav3 channels was confirmed by pharmacological block with 1 μM mibefradil (McDonough and Bean, 1998), which reduced

the CFCTs to 61% (p = 0.012) (Figure 1G) and to 46% (p < 0.001) of control in smooth dendrites and in spines and spiny branchlets (Figure 1H), respectively. The spatial profile of the CFCTs recorded from Cav3.1 KO mice was similar to that observed in WT mice, with a half decrement at 93.5 μm (steepness of 16.3 μm) in the smooth dendrites and a λ = 56.3 μm in the spiny dendrites (Figures 1I and 1J). In conclusion, electrotonic filtering of the CF excitatory postsynaptic potential (EPSP) in spiny branchlets reduces calcium signaling at distal PF synapses, which is mainly mediated by T-type channels. We explored whether PF input-mediated glutamatergic signaling might promote CF-evoked dendritic calcium electrogenesis. Selective mGluR1 activation by DHPG potentiated CFCTs by 350% ± 80% in spiny branchlets and by 320% ± STK38 120% in smooth dendrites (n = 8 cells; paired data) (Figures 2A–2D). This effect developed in a few tens of seconds, as DHPG penetrated into the slice and was accompanied by a slower increase of basal calcium concentration (slope 4% ± 1%.min−1 [±SD]) (Figure 2B). The somatic complex spike remained unchanged (Figure S2), confirming that 20 μM DHPG did not depress the CF EPSP (Maejima et al., 2005). Strikingly, the potentiated CFCT no longer showed decrease with distance from the soma (Figure 2E), an effect that cannot be attributed to dye saturation (see Supplemental Information).

5 but is substantially decreased by E12.5 ( Figures 1A–1D; data not shown). Consistent with previous studies showing a requirement for GDE2 in interneuron generation, Gde2 transcripts extend dorsally from E10.5, coincident with the timing of ventral and dorsal interneuron formation ( Figures 1B and 1C; Yan et al., 2009). Similarly, GDE2 protein is expressed in postmitotic somatic motor neurons from E9.5 and is detected dorsally from E10.5 ( Figures 1E and 1F). Examination of GDE2 expression in relation to columnar-specific

motor neuron markers at fore- and hindlimb levels of the spinal cord shows that GDE2 is localized to newly differentiating motor neurons and to MMC and lateral and medial LMC motor neurons ( Figures 1E–1G’; Tsuchida et al., 1994; data not shown). By E12.5, GDE2 protein is reduced within motor neuron check details cell bodies but is enriched within motor axons, suggesting that GDE2 may have later roles in postmitotic motor neuron development ( Figures 1H and 1I). Thus, GDE2 is expressed in somatic motor

neuron cell bodies coincident with the period of motor neuron neurogenesis. To test the requirement for GDE2 in regulating motor click here neuron generation, we generated stable mouse lines that lack functional GDE2 (Gde2−/−) using Cre-lox technology (see Figure S1 available online). We confirmed GDE2 ablation using a combination of PCR, direct sequencing, western blot, aminophylline and immunohistochemical analyses ( Figure 7C; Figure S1). Examination of Gde2−/− and wild-type (WT) littermates at the onset of motor neuron differentiation at E9.5 showed an approximately 50% loss of Isl1/2+ and HB9+ motor neurons ( Figures 2A, 2B, 2D, 2E, and 2G; Nornes and Carry, 1978). However, the number of Olig2+ motor neuron progenitors and the dorsal-ventral patterning of spinal progenitors were not affected ( Figures 2C, 2F, and 2G; Figure S2). No increase in TUNEL

staining was detected in Gde2−/− animals, suggesting that the loss of GDE2 does not compromise motor neuron survival but instead disrupts motor neuron formation ( Figure S2). Consistent with this model, Gde2 null mutants showed a decrease in the number of progenitors exiting the cell cycle ( Figures 2J, 2M, and 2N). Although no changes in the proportion of cells in S phase and M phase were detected, the total number of cells in S phase after a 16 hr BrdU pulse was increased, suggesting that the length of the cell cycle is extended in the absence of GDE2 ( Figures 2H–2N; Yan et al., 2009). These data collectively support previous findings in the chick showing that GDE2 is required to regulate motor neuron generation but does not affect progenitor patterning and specification ( Rao and Sockanathan, 2005). Some motor neurons are generated in the absence of GDE2, suggesting that GDE2 function might be redundant with its family members Gde3 and Gde6 ( Nogusa et al., 2004 and Yanaka et al., 2003).

(2009) of their meta-analysis of regions involved in top-down and bottom-up attention, with previously published analyses of top-down and bottom-up effects in episodic PD-1/PD-L1 inhibitor 2 remembering ( Ciaramelli et al., 2008 and Vilberg and Rugg, 2008), did not support the idea of overlap between perceptual attention and memory processes, especially for ventral parietal cortex. And, as noted above, Sestieri et al. (2010) found different parietal areas associated with their perceptual and memory search tasks. Nevertheless, as Wagner et al. (2005) suggested,

parietal activity is associated with a number of factors important for memory judgments, including a subjective sense that the relevant information is old or new (independent of the memory’s Navitoclax veracity, Johnson, 2006), level of detail that the memory supports, and retrieval orientation—the type of detail that participants are asked to retrieve about target memories. That is, parietal mechanisms may be involved in attending to internal, mnemonic representations, act as a buffer to integrate details that have been activated, reflect the overall strength of memories, and/or play a role in the evaluation of the task relevance of what is remembered (Wagner et al., 2005, Cabeza et al., 2008, Vilberg and Rugg, 2008 and Shimamura, 2011). Importantly, the PRAM

framework assumes that the distinction between perceptual and reflective attention is orthogonal to the distinction between top-down and bottom-up attention (Chun et al., 2011 and Corbetta and Shulman, 2002). Thus, efforts to compare control mechanisms for perceptual and reflective information should attempt to equate whether attention is directed to the task stimuli in a top-down or bottom-up manner. Studies to date typically relied on top-down manipulations (Nee and Jonides, 2009, Henseler et al., 2011 and Roth et al., 2009). It would

be helpful to introduce stimuli that capture attention in a the bottom-up manner to assess the extent to which a common ventral network is engaged in both perceptual and reflective tasks. That is, it would be useful to directly compare four conditions: top-down and bottom-up attentional conditions in both perceptual and reflective tasks. Perception and reflection both need selective mechanisms to resolve interference. Perception requires focusing on task-relevant information from among perceptually present task-irrelevant information. Perceptual competition makes it more difficult to find a T among Ls than among Os in visual search and can even produce quite dramatic examples of blindness to unattended information (Simons and Chabris, 1999; reviewed in Marois and Ivanoff, 2005). Resolution of competition (successful selection) occurs when goals bias activation in favor of goal relevant features (Desimone and Duncan, 1995). During perceptual identification, the strength of sensory evidence for a target can be measured by the strength of activity within a cortical region for the target category.

The length of an individual trial was 60 × the length of stimulation train or 60 × 1 s, whichever was longer. For stimulation lengths of 20 pulses or greater, a new stimulation train could be earned as soon as the previous train had finished. For stimulation OSI-744 research buy lengths of ten pulses or fewer, there was a short timeout (1 s – length of stimulation train) before the next train could be earned. This was to ensure that it was physically possible for subjects to respond for all available trains regardless of the stimulation length used. At the end of each trial, the house light and the white noise were turned

off. After an inter-trial interval of approximately 1 min, the next trial began. BI 2536 mw During this 1.5 hr test session subjects were initially given 30 min of regular FR1 training. Subsequently, a within-session extinction period began. During this phase, responses at the active port were recorded but had no consequence. After 30 min of extinction had elapsed, 5 stimulation trains (each train 1 s long, intertrain interval = 1 s) were delivered to signal the renewed availability of reinforcement at the active port. For the rest of the session rats were reinforced on an FR1 basis for responses at the active port. On the day before the contingency

degradation test, subjects were given an additional 1 hr FR1 training session. The number of stimulation trains delivered during this session (dependent on subjects’ responses at the active port) was used to calculate the average rate of stimulation for the contingency degradation portion of the experiment. The next day, rats were given 30 min of regular FR1 training. Subsequently, a within-session contingency degradation period began. During this phase, stimulation trains were delivered pseudorandomly Cell press and noncontingently at a rate that was matched to each subjects’ performance during FR1 training on the previous day. After a further 30 min had elapsed, a reacquisition

phase was initiated. During this phase, stimulation was once again contingent on a response made at the active port. The total length of this test was 1.5 hr. During this experiment, whenever a stimulation train was delivered (regardless of whether it had been earned by a nosepoke response or was delivered non-contingently) the LED lights in the active port were concurrently illuminated. The behavioral data was analyzed with nonparametric tests as specified (e.g., Wilcoxon signed-rank rest for paired data, Mann Whitney test for unpaired data) coupled with Bonferroni tests to control for multiple comparisons where appropriate. This statistical approach resulted in a conservative measure of statistical significance. Given that the behavioral data was distributed in a non-Gaussian manner, and the different behavioral conditions varied greatly in their variance (e.g.