, 2007; Gradin et al , 2011) It has been proposed that insuffici

, 2007; Gradin et al., 2011). It has been proposed that insufficient suppression

of the default network or its hyperactivity might be related to positive symptoms of schizophrenia, such as hallucination and paranoia (Buckner et al., 2008; Anticevic et al., 2012). For example, the amount of task-related suppression is reduced in some areas of the default network (Whitfield-Gabrieli et al., 2009; Selleckchem ABT 888 Anticevic et al., 2013). Given a large overlap between the default network and the brain areas involved in social cognition, hyperactivity, or any abnormal activity patterns in the default network might also underlie impairments in social functions among patients with schizophrenia (Couture et al., 2006). In addition, psychotic symptoms

of schizophrenia tend to emerge after early adulthood, often many years after impaired cognitive functions can be detected (Cornblatt et al., 1999; Cannon et al., 2000). This is consistent with the hypothesis that clinical symptoms of schizophrenia arise from malfunctions ATR inhibitor of the prefrontal cortex and default network, since similar to the extended developmental trajectory of the prefrontal cortex (Lewis, 2012), the functional connectivity of the default network continues to increase during adolescence (Fair et al., 2008). Therefore, it would be important to test whether subjects at risk for schizophrenia are impaired in tasks that require model-based reinforcement learning. Depression and anxiety disorder are both examples of internalizing disorders, namely,

they are largely characterized by disturbances in mood and emotion (Kovacs the and Devlin, 1998; Krueger, 1999). These two conditions show a high level of comorbidity and are accompanied by poor concentration and negative mood states, such as sadness and anger (Mineka et al., 1998). Nevertheless, there are some important differences. Overall, symptoms of anxiety are appropriate for preparing the affected individuals for impending danger, whereas depression might inhibit previously unsuccessful actions and facilitate more reflective cognitive processes (Oatley and Johnson-Laird, 1987). Physiological arousal is an important feature of anxiety, whereas anhedonia and reduced positive emotions occur in depression (Mineka et al., 1998). Both depression and anxiety disorder tend to introduce systematic biases in attentional and mnemonic processes as well as decision making (Mineka et al., 1998; Paulus and Yu, 2012). In particular, individuals with anxiety disorders become hypersensitive to potentially threatening cues without obvious memory bias. In contrast, depressed individuals show a bias to remember negative events (Matt et al., 1992), and to ruminate excessively (Nolen-Hoeksema, 2000). The possible neural changes responsible for the symptoms of these two mood disorders have been extensively studied, and some candidate brain systems have been identified.

Finally, we analyzed dendritic spines and their postsynaptic dens

Finally, we analyzed dendritic spines and their postsynaptic densities in CA1. Like for thorny excrescences, 4 weeks of enrichment led to a marked and comparable increase in stratum radiatum spine densities in β-Adducin−/− click here and wild-type mice ( Figure 6A). In further analogy to AZ densities at thorny excrescences,

a detailed analysis of PSD95-positive postsynaptic densities revealed that frequencies of PSD95 puncta per spine decreased markedly upon enriched environment ( Figure 6B), leading to a suppression of CA1 excitatory synapse increases upon enrichment in β-Adducin−/− mice ( Figure 6B). Taken together, these results provide evidence that the presence of β-Adducin is specifically required to establish new synapses under conditions of enhanced plasticity in the adult. In the absence of β-Adducin, environmental enrichment still leads to an increase in dendritic spine numbers, but this increased density of spines is not matched by a corresponding increase in actual synapses, leading to a failure to increase the densities of excitatory synapses at

LMTs and in CA1. Does the failure to establish new synapses upon enrichment in β-Adducin−/− mice affect the beneficial effects of environmental enrichment on learning? To address this question, we focused on learning protocols involving a hippocampal mossy fiber requirement (e.g., Jessberger et al., 2009), where any learning defect may then be rescued by re-expressing GFP-β-Adducin in granule cells. In a first set of experiments, we compared freezing upon contextual fear conditioning in mice housed under control or enriched (4 weeks) conditions. DAPT datasheet As expected, and consistent with stronger learning, re-exposure to context 1 day after learning elicited stronger freezing in enriched wild-type mice ( Figure 7A). When housed under control conditions β-Adducin−/− mice were not noticeably different from wild-type controls in this associative learning task ( Figure 7A; as mentioned in Experimental Procedures, and in good agreement with a previous study [ Rabenstein et al., 2005], the mutant mice did exhibit Rolziracetam reduced freezing to context when subjected to a milder

conditioning method). However, instead of increasing freezing, enrichment reduced freezing in β-Adducin−/− mice ( Figure 7A). In control experiments the environmental enrichment protocol did enhance fear conditioning-induced freezing in Rab3a−/− mice that lack mossy fiber LTP ( Castillo et al., 1997), indicating that failure by environmental enrichment to increase fear conditioning learning in β-Adducin−/− mice was not just due to a deficit in LTP at this critical synapse ( Figure 7A). Environmental enrichment has been shown to increase neurogenesis in the dentate gyrus in the adult, and adult neurogenesis has been related to improved hippocampal learning ( Deng et al., 2010). Therefore, in a second set of control experiments, we compared adult dentate neurogenesis upon enrichment in wild-type and β-Adducin−/− mice.

, 2008, Schoffelen and Gross, 2009 and Siegel et al , 2008) Furt

, 2008, Schoffelen and Gross, 2009 and Siegel et al., 2008). Furthermore, we investigated functional http://www.selleckchem.com/products/CP-690550.html modulations rather than absolute levels of synchronization. This subtracted out the spatial pattern of synchronization induced by the limited spatial resolution that is common to any two conditions compared. Another crucial but often ignored problem is that interaction measures of neural population signals depend on the relative weighting of different signal components (Nunez and Srinivasan, 2006). Specifically, they depend on the weighting of the neural signal of interest relative to

noise and neural signals that are not of interest. Thus, even if the true interaction between the signal components remains constant, changes in the components’ amplitudes may alter their relative weighting and cause a change in the measured interaction between the population signals. We addressed this problem by comparing changes in synchrony to concurrent changes in signal amplitude (see Supplemental Experimental Procedures available online). Second, we devised a new analysis approach that allows for identifying networks of synchronized cortical regions (Figure S2 available online). In brief,

we employed permutation statistics to identify cortical networks as continuous clusters in a high-dimensional interaction space (see Experimental Procedures). This allowed for directly identifying networks across a full pairwise cortico-cortical space. We applied this approach to source-level coherence estimated from EEG (Gross et al., 2001), which quantifies the frequency-specific phase consistency between regions. This allowed us to effectively Ku-0059436 supplier image synchronized cortical networks across space, time, and frequency. Importantly, no a priori assumptions had to be made about the time and frequency of synchronization or about the number, size, location, and spatial structure of the synchronized networks. We first applied this network-identification approach either to contrast cortico-cortical coherence between the stimulation and baseline

intervals. This revealed a widespread but highly structured cortical network (Figures 3A and 3B, permutation-test, p = 0.0245) that showed enhanced beta-band coherence (15–23 Hz) during stimulation. The network consisted of a largely symmetric pattern of cortical regions spanning extrastriate visual areas implicated in the processing of visual motion as well as higher order association areas. Bilaterally, it included frontal regions consistent with the FEF, posterior parietal cortices along the intraparietal sulcus (IPS), lateral occipitotemporal cortices consistent with the middle temporal area (MT+), and medially extrastriate visual cortex near the transversal occipital sulcus (see Table S1 available online). Beta-band coherence in this network was enhanced for about 1 s around the time of bar overlap (Figure 3B).

, 2011) For example, 19 such developmentally regulated miRNA in

, 2011). For example, 19 such developmentally regulated miRNA in PFC were 24-fold more divergent in human than in chimpanzee. Thus, while gene regulatory pathways have long been proposed as a predominant driver of metazoan evolution (see Gerhart and Kirschner, 1997), miRNA may account for a significant part of

the expansion in cognitive and intellectual capacity in humans. Given the cellular and transcriptional complexity of the nervous system, it is not surprising that miRNAs are highly abundant in this tissue (reviewed by Duvelisib Kosik, 2006). Although initial comprehensive profiling of miRNA expression was limited to broad areas of the brain, the advent of new profiling technology makes it clear that the spatial landscape of miRNA expression may be highly complex at the cellular level. For example, by combining immunoprecipitation of tagged, transgenic Ago2 with the cell-type-specific Cre/Lox system in mouse (a method called “miRAP”; Figure 2A), it has been possible to ascertain the miRNA “finger prints” of different GABAergic interneurons and excitatory pyramidal cells from neocortex or Purkinje

cells from buy Bioactive Compound Library cerebellum (He et al., 2012). Nearly half of the over 500 miRNA assayed were relatively specific between overall neocortex and cerebellum, and roughly one-quarter of the miRNA showed specificity between pyramidal neurons and interneurons or between two subtypes of interneurons (parvalumin [PV] versus neuropeptide somatostatin expressing [SST]; Figure 2B). For example, six of ten miRNA quantified in follow-up experiments were selectively enriched in PV interneurons, despite the fact that these neurons share many properties with SST interneurons (Figure 2C; He et al.,

2012). Thus, while profiling at this single cell-type resolution has just begun, it is clear that crotamiton the miRNA landscape offers many opportunities to fine-tune the distinct developmental and functional properties of neuronal subpopulations. Even within a single neuron, complex functional architecture offers many compartments that could be regulated by different sets of miRNA. An early comparison between miRNA in the cell bodies and neurites of rodent hippocampal neurons showed a graded distribution across a set of 99 candidates, the extremes of which defined miRNA that are selectively enriched in dendrites versus soma (Kye et al., 2007). This study also examined miRNA copy number and estimated an average of 10,000 copies per cell, a number that is within an order of magnitude of average synapse number per neuron, thus raising the intriguing question of whether synaptic miRNA can be locally effective in very small numbers. Nonetheless, the synaptic compartment appears to contain a large fraction of the neuronal miRNA pool. Recent analysis of miRNA representation in synaptoneurosome fractions from five different rodent brain regions showed that roughly half of the miRNA genes tested were enriched in this synaptic material (Pichardo-Casas et al.

Genetic access to nNOS+ GABAergic projection neurons and NGFCs wi

Genetic access to nNOS+ GABAergic projection neurons and NGFCs will facilitate the study of their inputs and outputs, physiological properties, and in vivo functions. The nNOS-CreER driver also efficiently labeled nNOS neurons in olfactory bulb, striatum, amygdala, superioculicullus, and hypothalamus ( Figure S6; Table 2). Corticotropin releasing hormone (CRH; also known as corticotropin releasing factor-CRF) is best known for mediating neuroendocrine stress response (Korosi and Baram, 2008). CRH and its

receptors are widely expressed in the CNS (Korosi and Baram, 2008). CRH modulates a wide range of behaviors, including anxiety, arousal, motor function, learning, and memory (Korosi and Baram, 2008), and has been implicated in early life programming (Korosi and Baram, 2009) and depression Sirolimus molecular weight (Binder and Nemeroff, 2010).

In cerebral cortex, CRH neurons constitute a significant fraction of GABA interneurons (Kubota et al., 2011). The CRH-ires-Cre driver appears to target CRH neurons throughout the brain, including those in the paraventricular nuclei of hypothalamus, bed nucleus of the stria terminalis, locus coeruleus, raphe, and amygdala ( Figure S7, Table 2). In superior culicullus, labeled neurons include bottlebrush cells, which project their dendritic terminals in monostritified arrays selleck screening library (“bottlebrush” dendritic endings) and have been implicated in motion processing ( Major et al., 2000). In hippocampus and neocortex, the subset of targeted interneurons showed no overlap with PV, SST, and only partial overlap with CR (33% ± 5%; n = 816 cells from two mice). The CRH-ires-Cre driver will facilitate studies of the function and development of CRH neurons; it will also allow study of how early life experience and chronic stress alter the connectivity and function of CRH neurons MTMR9 in distributed

neural circuits that mediate stress responses in the adult brain. The calcium binding protein calretinin (CR) is expressed in a subpopulation of GABAergic neurons throughout the brain. In cerebral cortex, CR interneurons include layer 1 GABA neurons and several subpopulations that coexpress SST and VIP (Kubota et al., 2011). Labeling mediated by CR-ires-Cre and CR-CreER driver lines largely recapitulate endogenous CR expression ( Table 2; Figure S8). The CR-CreER shows high or modest Cre activity, depending on brain regions, upon tamoxifen induction ( Figure S8). Cortistatin (CST) is a neuropeptide that shares 11 of its 14 amino acids with SST (de Lecea, 2008). CST is predominantly expressed in cerebral cortex, and in subsets of GABA interneurons with partial overlap to SST. In contrast to SST, CST administration in brain ventricles enhances EEG synchronization by selectively promoting slow-wave sleep (de Lecea, 2008). Steady-state levels of CST mRNAs oscillate during the light:dark cycle and are upregulated upon sleep deprivation.

, 2008a), confirming their neuronal identity For studying the ef

, 2008a), confirming their neuronal identity. For studying the effects of expressing wild-type and chimeric receptors based on GluN2A and GluN2B, constructs were cotransfected with peGFP (ratio 1:1) to identify transfected cells. Coexpression at this ratio was confirmed in the case of pRFP (Papadia et al., 2008). After 48 hr, the transfected neurons were then either

subjected to electrophysiological analysis or their fate following an excitotoxic insult was studied. Pictures of GFP-expressing neurons were taken on a Leica AF6000 LX imaging system, with a DFC350 FX digital camera. Using the automated cell-finder function within the Leica AF6000 software, images of transfected neurons were taken both before and 24 hr after a 1 hr treatment with NMDA (20 μM). Cell death was

assessed by counting the number Docetaxel clinical trial of surviving GFP-positive neurons. In the vast majority of cases, death was easily spotted as an absence of a healthy GFP-expressing cell where one once was. In place of the cell, there was in most cases (>90%) evidence of death in the form of fragmented neurites, fluorescent cell debris, and a pyknotic nucleus (Papadia et al., 2008). This confirmed that the cells were genuinely dying as opposed to more unlikely scenarios, such as quenching of eGFP fluorescence in a subpopulation of neurons. For each condition, 150–200 neurons were studied over several independent experiments. An identical experimental regime was employed for studying the influence of ICER expression

on vulnerability of GluN2B2A(CTR)/2A(CTR) Adriamycin nmr and GluN2B+/+ neurons to NMDA-induced excitotoxicity. Neurons were transfected with vectors encoding eGFP and the inhibitory CREB family member ICER1 (Stehle et al., 1993), or a control vector (encoding β-globin). We have Metalloexopeptidase previously confirmed that ICER1 expression inhibits CRE-mediated gene expression in neurons (Papadia et al., 2005). The fate of transfected neurons following exposure to NMDA was then studied as described previously. To measure extrasynaptic NMDAR currents, synaptically located NMDARs were blocked by quantal activation-mediated blockade by MK-801, as previously described (Martel et al., 2009 and Papadia et al., 2008). Briefly, whole-cell NMDAR currents were recorded (100 μM NMDA, in Mg2+-free and TTX/PTX-containing recording solution), after which the agonist was washed-out the recording chamber for 2 min. Irreversible NMDAR open-channel blocker MK-801 (10 μM; Tocris Bioscience) was then applied for 10 min, effectively antagonizing NMDARs located at the synapse and experiencing the localized, quantal presynaptic glutamate release (Martel et al., 2009 and Nakayama et al., 2005). Following the 10 min incubation period, MK-801 was then washed out (2 min), and the resulting extrasynaptic NMDAR currents were acquired.

, 2009 and Qin et al , 2010) Collectively, these studies support

, 2009 and Qin et al., 2010). Collectively, these studies support the idea that transcription factors can independently regulate two different aspects of axon development, growth and guidance, by inducing different target genes according to the developmental requirements of the cell. Is axon growth regulated by epigenetic mechanisms? Compelling evidence on epigenetic mechanisms selectively regulating axon growth in the mammalian brain U0126 nmr is scarce. Epigenetic regulators including the histone acetyltransferase CBP and the chromatin modifier Sat2b influence cortical and motor neuron projection patterns, but this is also linked to a role in neuronal subtype specification (Alcamo et al., 2008,

Britanova et al., 2008 and Lee et al.,

2009). Loss of function of the methyl-CpG-binding transcriptional repressor MeCP2 has been associated with several abnormalities in neuronal morphogenesis including disrupted axon projections (Belichenko et al., 2009 and Degano et al., 2009). find more Axonal targeting defects observed in MeCP2 knockout mice are attributed to changes in the expression of the guidance factor Semaphorin3F, albeit in a non-cell-autonomous fashion (Degano et al., 2009). Among the genes identified in a screen for axonal sprouting after stroke is ATRX (α-thalassemia/mental retardation syndrome X-linked) (Li et al., 2010b), a chromatin remodeling enzyme linked to mental retardation that has also been implicated in dendrite development and neuronal survival (Bérubé et al., 2005 and Shioda et al., 2011). ATRX appears to be upregulated in sprouting neurons relative to nonsprouting

neurons. Knockdown of ATRX by RNAi reduces basal axon growth of cultured DRG neurons and prevents axonal sprouting after stroke in vivo (Li et al., 2010b). Interestingly, ATRX and MeCP2 can interact in vitro and in cells, and in MeCP2 knockout cells ATRX fails to localize to heterochromatin, displaying instead a diffuse expression pattern (Nan et al., 2007). Thus, some of the neuronal defects observed enough in MeCP2 mutants might be due to abnormal ATRX activity. Future studies will be needed to understand the extent of epigenetic mechanisms in axon growth. As the receptive limbs of neurotransmission in the brain, dendrites have evolved to display immense variety of shape and size. Dendrite architecture strongly influences the processing of information (Spruston, 2008), suggesting that the morphogenesis of dendrite arbors directly impacts the flow of information across the brain. Although we will focus on the role of transcription factors on dendrite morphology in mammalian systems, significant contributions in this field have also come from studies in the fly nervous system. We refer the reader to excellent reviews on this topic (Corty et al., 2009, Jan and Jan, 2003 and Jan and Jan, 2010).

We found that neurons

We found that neurons INK1197 mw in the CD were more likely to encode the temporally discounted value for the chosen target

(n = 22 neurons) than for the unchosen target (n = 9 neurons; χ2 test, p < 0.01; Figure 4B). In the VS, 26 and 21 neurons significantly modulated their activity according to the temporally discounted value of the chosen and unchosen targets, respectively, and this difference was not significant (χ2 test, p > 0.4). We also found that six and nine neurons in the CD and VS, respectively, significantly modulated their activity according to the temporally discounted values for both chosen and unchosen targets (Figure 4B). For the CD, this was significantly more than expected when the temporally discounted values of chosen and unchosen targets influenced the activity of each neuron independently (χ2 test, p < 0.005). In addition, most neurons encoding the temporally discounted values for both chosen and

unchosen targets showed the same signs for their regression coefficients (four and seven neurons in the CD and VS, respectively). For both CD and VS, the correlation coefficient between the regression coefficients for the temporally discounted values of the chosen and unchosen targets was significantly more positive than the see more values obtained from the permutation test (p < 10−4; Figure 4B). To test whether activity seemingly related to temporally discounted values might reflect the effects of different target colors or number of yellow dots used to indicate the reward magnitude and delay, we analyzed the activity recorded during the control task. During the control task, the delay and magnitude of reward were fixed for all targets. Therefore, the activity of neurons encoding temporally discounted values Sclareol should be unrelated to the “fictitious” temporally discounted values that are computed as if the magnitude and delay of reward during the control task varied with the target color and number of yellow dots. Indeed, many of the neurons in the CD and VS that changed their activity according to the difference

in the temporally discounted values for the leftward and rightward targets (Figures 2B and 2C), their sum (Figure 3B), or the difference in the values for the chosen and unchosen targets (Figure 3F) did not change their activity according to the fictitious temporally discounted values in the control task. The number of CD neurons encoding the difference in the fictitious temporally discounted values for the leftward and rightward targets in the control task (n = 8, 8.6%) was significantly smaller than that in the intertemporal choice task (n = 24, 25.8%; χ2 test, p < 0.005; Table S2). In addition, the number of VS neurons encoding the sum of the fictitious temporally discounted values (n = 15, 16.7%) was significantly lower than that in the intertemporal choice task (n = 31, 34.4%, χ2 test, p < 0.01).

In the 1960s, it was demonstrated that X-irradiated sporozoites c

In the 1960s, it was demonstrated that X-irradiated sporozoites confer protective immunity in mice [3]; and the cloning of the gene encoding CSP from the monkey malaria parasite P. knowlesi [4] led to hopes that the homologous protein might form the basis of a vaccine against human malaria parasites. The pace of clinical trials of vaccines based on CSP and other malaria surface Libraries proteins from the two most see more widespread human malaria parasites, P. falciparum and P. vivax, has increased dramatically in the past decade, but so far the results have been mixed [2]. One of the major challenges

facing vaccine developers is the high level of naturally occurring polymorphism at several of the loci encoding surface proteins of P.

falciparum and P. vivax [5]. In the case of the CSP of P. falciparum, polymorphic variants in epitopes for host CD4+ T cell recognition have been shown not to be cross-reactive [6], implying that vaccines which rely on the use of these epitopes selleck compound to stimulate an immune response will fail to provide protection against all naturally occurring parasite variants [5]. At the CSP locus of P. falciparum, there is evidence that the polymorphism in T-cell epitopes is maintained by balancing selection driven by host T cell recognition [7], [8], [9] and [10]. Adenylyl cyclase Likewise, several other loci encoding malaria cell surface proteins show evidence of selectively maintained polymorphism [8], [11], [12] and [13]. Even under balancing selection, because of the role of genetic drift, the level of polymorphism that can be maintained is expected to be a function of the effective population size [14] and [15]. Consistent with theoretical expectations, there is evidence that population bottlenecks can effect the level of polymorphism at antigen-encoding loci of malaria parasites. For example, the

locus encoding apical membrane antigen-1 (AMA-1) of P. vivax shows considerably reduced polymorphism in Brazil in comparison to the Old World, reflecting a bottleneck in colonization of the New World [10] and [16]. Likewise, studies of P. falciparum populations on Pacific islands have revealed relatively low levels of polymorphism at several antigen loci, as expected in the case of founder effects in the colonization of islands by the parasite [17] and [18]. On the other hand, local populations in Old World mainland areas where malaria has long been present, such as Southeast Asia, have revealed substantial levels of polymorphism at antigen-encoding loci [9], [10], [12] and [19]. Given these high levels of polymorphism, the design of a locality-specific vaccine that provides immunity against all locally occurring variants seems problematic.

Some LGN cells are achromatic, responding only to luminous intens

Some LGN cells are achromatic, responding only to luminous intensity, while others are modulated by specific colors, typically classified as belonging to one of three wavelengths: short, medium and long (Wiesel and Hubel, 1966). Later work has shown a rich set of color-opponent pairs in CRFs (Reid and Shapley, 2002). We refer the reader to Solomon and Lennie for a review of color vision physiology (Solomon and Lennie, 2007). Selectivity for long wavelengths in the LGN is most common, in agreement with the large number of cones that are selective for long wavelengths (Wiesel and Hubel, 1966). Krüger determined that color-specific cells made up 90% of the population (Krüger, 1977).

Most cells displayed these characteristics when the stimulus was larger than the receptive field. The visual path is segregated into Nutlin-3a three major divisions at the LGN, magnocellular (M), parvocellular (P), and koniocellular (K), with functional differences between divisions largely consistent across species (Derrington

and Lennie, 1984, O’Keefe et Abiraterone solubility dmso al., 1998, Usrey and Reid, 2000, White et al., 2001 and Xu et al., 2001). M cells are typically achromatic, respond to higher temporal frequencies, and have large CRF centers. P cells have color-opponent structure in primates with input from two cone classes at middle and long wavelengths (Jacobs, 2008), respond to lower temporal frequencies, and have small CRF centers. Most K cells that have been described have strong input from short wavelength cones and have blue-on or blue-off CRF structure ( Hendry and Reid, 2000, Martin et al., 1997 and Tailby et al., 2008). According to Xu et al., a much from larger portion of K cells, 34%, cannot be driven by drifting gratings, compared to only 9% of M cells and 6% of P cells ( Xu et al., 2001). Recent work in primates has shown

the presence of K cells with orientation selectivity that might help explain the findings of weak responses to grating stimuli ( Cheong et al., 2013). K cell characteristics also vary across K layers, suggesting that there might be several classes of K cells, and appear to be more heterogeneous across species ( Hendry and Reid, 2000). Xu and colleagues, as well as O’Keefe et al. (1998), looked only at owl monkeys but their combined findings agree with what Usrey and Reid found in both owl and squirrel monkeys, and with what Norton and Casagrande found in the pro-simian galago ( Norton and Casagrande, 1982). Both Xu et al. and Usrey and Reid’s studies found that spatial summation was Libraries linear for all LGN cells that fit the linearity-testing criterion of responding well to drifting gratings (subsequently some of the recorded K cells were not tested for linearity). Xu et al. focused on the properties of K cells while O’Keefe et al. and Usrey and Reid looked primarily at M and P cell properties. The characteristics of M and P cells that O’Keefe et al.