Medial Frontal Cortex

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The involvement of metabotropic glutamate receptors in the induction of long-term potentiation in the medial frontal cortex of the rat

The involvement of metabotropic glutamate receptors in the induction of long-term potentiation in the medial frontal cortex of the rat

The involvement of group I mGluRs in the induction of LTP in the medial frontal cortex was investigated in a total of 9 slices, obtained from 5 rats. The bath application of 100 pM DHPG was paired with the TBS conditioning protocol and the effect on LTP incidence investigated. DHPG was bath applied for 10 min, starting 6 min prior to the delivery of TBS. DHPG reduced the size of the field response prior to TBS. LTP was elicited following TBS in the presence of DHPG in 7 slices. Of the remaining 2 slices, one showed STD, whereas the other exhibited no effect. An example of an experiment in which LTP of both the peak-to-peak amplitude and the slope of the population spike was elicited by TBS in the presence DHPG is illustrated in figure 4.7i, A and B. It is interesting to note that the first point following the completion of TBS is a still at control levels. This is typical of LTP evoked by this induction protocol. All 7 slices exhibiting LTP show this slow-onset, the time between the completion of TBS and the appearance of the maximal effect ranging between 2 and 10 min. This is likely to the consequence of the reversal of the DHPG depressant effect following washout of the drug. The response is almost completely abolished by the bath application of CNQX. The pooled data for all 9 slices are
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A causal role for posterior medial frontal cortex in choice-induced preference change

A causal role for posterior medial frontal cortex in choice-induced preference change

Based on participantÕs action during the stage 2 of the Switch and No-switch 9 trials, each image was categorized as either "preferred" or "unpreferred." Similarly, based 10 on participa[r]

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Neural correlates of visuospatial working memory in the ‘at risk mental state’

Neural correlates of visuospatial working memory in the ‘at risk mental state’

Kuperberg et al. (2003) found significant cortical thin- ning in the medial frontal areas of adult schizophrenic patients, and grey matter reductions have been re- ported in the medial premotor cortex (Honey et al. 2003). Imaging studies suggest that the medial frontal gyrus (Stevens et al. 1998 ; Paillere-Martinot et al. 2001) and the medial prefrontal cortex (Ananth et al. 2002) are affected early in psychosis. Suzuki et al. (2005) found the SMA to be reduced in subjects with recent- onset schizophrenia whereas Exner et al. (2006) showed that reduced volume of the SMA in FEP sub- jects was related to impaired implicit learning. Medial frontal cortex dysfunction is compatible with the hy- pothesis of a core deficit in early stages of psychosis involving a failure to monitor actions generated in- ternally (Exner et al. 2006). Activation in the cuneus and precuneus increased in the second half of the run, during the harder versions of the task, in all three groups. However, this increase itself was greatest in the FEP group, least in the controls, and intermediate in the ARMS cohort. Given that behavioural perform- ance improved, it is likely that this differential acti- vation of the precuneus may underpin such a learning
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Altered Diffusion in the Frontal Lobe in Parkinson Disease

Altered Diffusion in the Frontal Lobe in Parkinson Disease

Maps of Anisotropy. Analysis of DTIs of the whole brain, including the brain stem and cerebellum, revealed a significant decrease in FA values in patients with PD bilaterally in the medial frontal cortex, including the supplementary motor area; the pre-supplementary motor area; the right rostral me- dial frontal gyrus; the left anterior cingulate gyrus; the right and left rostral cingulate gyrus; the right superior, middle, and inferior frontal gyri; and the bilateral middle frontal gyri at the frontal pole. The right superior longitudinal fasciculus and left corpus callosum were also involved within the significant clus- ter (Fig 2 and Table 2). There were no areas with significantly increased FA. A difference in z-scores and volume of signifi- cant voxels was noted between hemispheres, which was pri- marily due to involvement in the dorsolateral prefrontal cor- tex and medial frontal lobes. The cluster was larger and z-scores were higher in the left hemisphere. However, the SPM analysis does not directly compare the 2 hemispheres.
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Altered microstructure of brain white matter in females with anorexia nervosa: a diffusion tensor imaging study

Altered microstructure of brain white matter in females with anorexia nervosa: a diffusion tensor imaging study

Results: Compared with CW, AN patients revealed a significant decrease in FA maps in the left superior frontal gyrus, medial frontal gyrus, anterior cingulate cortex, middle frontal gy[r]

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Cortical control of hering-breuer reflexes in anesthetized rats

Cortical control of hering-breuer reflexes in anesthetized rats

Prefrontal cortex (PFC) has long been implicated in autonomic control playing a key role in the coordina- tion of affective and autonomic responses [1, 2]. Dys- function of PFC can lead to disturbances in autonom- ic regulation and neuroendocrine responses that are associated with mood disorders [3]. An increasing knowledge of associations between PFC lesions and stroke-induced executive deficits, such as cardiac com- plications and respiratory dysfunction [4-8], stimulates interest concerning the role of the central autonomic nervous system in cardiovascular and respiratory con- trol. It has been found that there is a distinct interac- tion of the insular cortex (IC, lateral PFC) with heart rate and blood pressure control [9-11]. Our previous studies have confirmed that IC and infralimbic cortex (IL, ventromedial PFC) are involved in the respiratory
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Optical Properties of In1 xGaxN Epilayers Grown by HPCVD

Optical Properties of In1 xGaxN Epilayers Grown by HPCVD

The case for EEG asymmetry connectedness to affective science has continued to build. Davidson, Taylor, and Saron (1979) may have been the earliest to report that positive affect (e.g., happiness) resulted in significantly higher “frontal ratio” scores with a left-sided reduction in the quantity of the alpha (α) 8-13 Hz bandwidth. Conversely, negative affect (e.g., disgust) was associated with a reversal of the frontal α ratio score. Parietal asymmetry did not differentiate between positive and negative affect. Activity in the α bandwidth was used as an index of inverse cortical activity, which assumes that a brain region producing α rhythms is in a state of cortical idling. Thus, the more α appearing in the EEG of a region the less active or engaged it is. Appendix A provides a detailed explanation of this assumption. In summarizing Davidson’s findings, Shaw (2003) notes that responses to emotional experiences such as films associate with frontal rather than posterior α asymmetry, a nod to the functional specificity of α in the PFC.
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The role of the frontal cortex in memory: an investigation of the Von Restorff effect

The role of the frontal cortex in memory: an investigation of the Von Restorff effect

Evidence from neuropsychology and neuroimaging indicate that the pre-frontal cortex (PFC) plays an important role in human memory. Although frontal patients are able to form new memories, these memories appear qualitatively different from those of controls by lacking distinctiveness. Neuroimaging studies of memory indicate activation in the PFC under deep encoding conditions, and under conditions of semantic elaboration. Based on these results, we hypothesize that the PFC enhances memory by extracting differences and commonalities in the studied material. To test this hypothesis, we carried out an experimental investigation to test the relationship between the PFC-dependent factors and semantic factors associated with common and specific features of words. These experiments were performed using Free-Recall of word lists with healthy adults, exploiting the correlation between PFC function and fluid intelligence. As predicted, a correlation was found between fluid intelligence and the Von-Restorff effect (better memory for semantic isolates, e.g., isolate “cat” within category members of “fruit”). Moreover, memory for the semantic isolate was found to depend on the isolate’s serial position. The isolate item tends to be recalled first, in comparison to non-isolates, suggesting that the process interacts with short term memory. These results are captured within a computational model of free recall, which includes a PFC mechanism that is sensitive to both commonality and distinctiveness, sustaining a trade-off between the two.
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Laminar degeneration of frontal and temporal cortex in Parkinson disease dementia

Laminar degeneration of frontal and temporal cortex in Parkinson disease dementia

Parkinson’s disease (PD) with dementia (PDD) is characterized by reduced gray matter volume in allocortical and neocortical regions including parietal and frontal cortices, cingulate gyrus (CG), and in temporal lobe regions such as the hippocampus and amygdala [1]. Histologically, a complex synucleinopathy is present comprising Lewy bodies (LB), Lewy neurites (LN), and Lewy grains (LG) [2,3]. The laminar distribution of a pathology in the cerebral cortex may represent degeneration of specific cortical pathways that have their cells of origin or axon terminals located within specific lamina [4]. The spread of pathology into and among cortical areas could be an important factor in the development of PDD. Hence, to investigate cortical degeneration in PDD, changes in density of the LB, LN, and LG together with abnormally enlarged neurons (EN), surviving neurons, vacuoles, and glial cell nuclei were studied across the cortical laminae in gyri of frontal and temporal lobes in fifteen cases of the disease.
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Quantification of white matter fibre pathways disruption in frontal transcortical approach to the lateral ventricle or the interventricular foramen in diffusion tensor tractography

Quantification of white matter fibre pathways disruption in frontal transcortical approach to the lateral ventricle or the interventricular foramen in diffusion tensor tractography

Pathologies occupying the interventricular foramen (foramen of Monro — FM) or the anterior part of lateral ventricle (LV) are accessed by the transcortical or transcallosal route. As severing of rostral corpus callosum has been deemed inferior to cortical incision, the approaches through various points of frontal lobe have been developed. Superior (F1), middle (F2) frontal gyrus or occasionally superior frontal sulcus are used as an entry of neurosurgical corridor. In spite of the fact that every approach to LV or FM causes its characteristic irreversible damage to white matter, to date all of transcortical routes are regarded as equivalent. The current study compared the damage of main neural bundles between virtual trans-F1 and trans-F2 corridors by means of diffusion tensor tractography method (DTT) in 11 magnetic resonance imaging (MRI) exams from clinical series (22 he- mispheres, regardless of dominance). Corpus callosum, cingulum, subdivisions I and II of superior longitudinal fasciculus (SLF I and SLF II), corticoreticular as well as pyramidal tracts crossing both approaches were subjected to surgical violation. Both approaches served a similar total number of fibres (0.94 to 1.78 [× 10 3 ]).
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Selective impairment in executive functions: A test of the selective executive deficit hypothesis in adults with treatment-discontinued phenylketonuria

Selective impairment in executive functions: A test of the selective executive deficit hypothesis in adults with treatment-discontinued phenylketonuria

There is evidence for the impact of these factors on performance in the nback task. For example, Cohen & Servan-Schreiber (1997) demonstrated a distributed network of regions involved in nback performance with greater prefrontal activation as the working memory span demands of the task increased, yet loci within the dorsolateral PFC evinced exclusively an inverted-U shaped neurophysiological response ffom lowest to highest load, consistent with a capacity-constrained response. The results of this study were used to suggest that regionally specific nodes within the working memory network are capacity-constrained in the physiological domain, providing a missing link in current explorations o f the capacity characteristic o f working memory (Callicott et al., 1999). There is further evidence that working memory emerges ffom the formation o f a dynamic cortical network linking task-specific processes with non­ specific, capacity-limited, higher-order attentional processes (McEvoy, Smith & Gervins, 1998). Thus, there appear to be a number of processes involved in nback task performance, some of which are affected by working memory capacity and others which are not. It may be the case that the demonstrated activation in particular regions o f the dorsolateral preffontal cortex interacts with the modulatory effects of dopamine in such a way that there is not a straightforward relationship between dopamine depletion and deficits in capacity for processing information with a high working memory load.
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Development of insula connectivity between ages 12 and 30 revealed by high angular resolution diffusion imaging

Development of insula connectivity between ages 12 and 30 revealed by high angular resolution diffusion imaging

myelination [Bartzokis et al., 2010]. All age-related increases in fiber density were found in the temporal cortex. One of these, upon examination of the raw fiber density matrices, switched directions. Of the five significant developmental effects in the temporal cortex, four were increases in fiber density, and one was a decrease in fiber density. Prior work has shown different developmental trajectories across the cortex [Sowell et al., 2003; Gogtay et al., 2004] and these results of more age-related increases in connections of the temporal cortex and decreases in connections of the frontal cortex are consistent with previous results found in a larger, overlapping cohort when the whole connectome was examined [Dennis et al., 2012]. The differences we found could be partly due to differences in the developmental trajectories of the frontal and temporal cortex and their connections. Giedd et al. [1999] found the temporal cortex had a later age of peak when measuring gray matter volume than other cortices. In Sowell et al. [2003], we found the gray matter density (GMD) of the superior frontal sulcus decreased from age 7 on, but the GMD of the superior temporal sulcus increased until age 30. Sowell et al. [2002] also found that the posterior-superior temporal and inferior parietal cortices increased the most in gray matter density between ages 7-30. The insula is one of the first cortical structures to develop [Chi et al., 1977], but it continues to mature throughout childhood, with continued cortical thinning across ages 6-10 [Muftuler et al., 2011]. Similarly, the limbic fibers are among the first to develop [Huang et al., 2006], but the afferent and efferent connections of the insula also continue to develop into adulthood. These include the uncinate fasciculus [Hasan et al., 2009; Kalani et al., 2009], internal capsule fibers, and the arcuate fasciculus [Paus et al., 1999]. Additionally, the white matter of the insula itself changes with age; as Herting et al. [2012], for example, found the FA of the right insula increased with pubertal status.
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Linear measures of atrophy in mild Alzheimer disease

Linear measures of atrophy in mild Alzheimer disease

The linear measurements that were taken, on both sides when appropriate (Fig 2), are as follows. The bifrontal index, measured on a plane parallel to the temporal lobe plane at the level of the maximal width between the tips of the frontal horns of the lateral ventricles (31), and defined as the ratio of this measure to the width of the brain at the same level multiplied by 100 (Fig 2A) (31). The interhemi- spheric fissure width, measured on the same plane as the bifrontal index, and defined as the greatest distance be- tween the mesial aspects of the cerebral cortex in the interhemispheric fissure. The interuncal distance, mea- sured on a plane parallel to the bicommissural plane at the level of the suprasellar cistern, as the distance between the unci of the temporal lobes (32) (Fig 2B). The minimum thickness of the medial temporal lobe, measured on a plane parallel to the temporal lobe plane, as the thickness of the medial temporal lobe considered at its narrowest point on the scan section that best represents the medial temporal lobe between its superior and inferior limits (fur- ther details can be found in the original article by Jobst et al [9]). The hippocampal height, measured on a plane parallel to the brain stem axis plane where the hippocam-
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Clinical Applications of Simultaneous PET/MR Imaging Using (R) [11C] Verapamil with Cyclosporin A: Preliminary Results on a Surrogate Marker of Drug Resistant Epilepsy

Clinical Applications of Simultaneous PET/MR Imaging Using (R) [11C] Verapamil with Cyclosporin A: Preliminary Results on a Surrogate Marker of Drug Resistant Epilepsy

tients with epilepsy to compare the expression of Pgp between patients with DRE and healthy controls, by using the percentage changes in verapamil influx or the efflux rate before and after Pgp inhibitor injection. However, to our knowledge, there has been no study for MRI-negative neocortical epilepsies, and previous methods were applied only to medial temporal lobe epilepsy (TLE). Furthermore, they confirmed that the change in the vera- pamil influx rate was smaller in patients with DRE compared with healthy controls; this difference necessitated the use of complex analytic methods, including invasive serial arterial sampling, which has limited applicability in clinical practice.
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The effect of occipital nerve field stimulation on the descending pain pathway in patients with fibromyalgia: a water PET and EEG imaging study

The effect of occipital nerve field stimulation on the descending pain pathway in patients with fibromyalgia: a water PET and EEG imaging study

Our results also demonstrate increased activation of the parahippocampus during ONS. The parahippocam- pus is associated with contextual processing and is im- portant in pain processing [61–65]. It has been shown that fibromyalgia is associated with metabolite abnor- malities within the right (para)hippocampus that correl- ate with patient symptoms due to chronic stress [66, 67]. This is consistent with the notion of a generalized aver- sion/distress network consisting of the parahippocam- pus, cerebellum, hypothalamus, and subgenual anterior cingulate cortex [68]. Parahippocampal involvement in pain might be due to contextual memory, which can modulate pain via its influence on the descending pain pathway, thereby encoding aversive pain memory [39, 69]. In fibromyalgia, it is known that this contextual pain suppression mechanism is dysfunctional, leading to a subsequent dysregulation of emotional contextual pain suppression [42, 70]. Based on these findings it is hypothesized that the parahippocampal area is a control switch for the involvement of the ascending medial pathway in the affective component of pain and the descending pain inhibitory pathway [71]. Conceptually, stimulation of the greater occipital nerves activates the parahippocampus, which subsequently controls the mobilization of the medial pain and descending inhibi- tory pathway [72].
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Neuronal representation of working memory in the medial prefrontal cortex of rats

Neuronal representation of working memory in the medial prefrontal cortex of rats

Working memory is a process for short-term active maintenance of information. Behavioral neurophysiological studies in monkeys have demonstrated that the dorsolateral prefrontal cortex (dlPFC) is a key cortical region for working memory. The medial prefrontal cortex (mPFC) in rats is a cortical area similar to the dlPFC in monkeys in terms of anatomical connections, and is also required for behavioral performance on working-memory tasks. However, it is still controversial regarding whether and how mPFC neurons encode working memory. In the present study, we trained rats on a two-choice spatial delayed alternation task in Y maze, a typical working memory task for rodents, and investigated neuronal activities in the mPFC when rats performed the task. Our results show that, (1) inactivation of the mPFC severely impaired the performance of rats on the task, consistent with previous studies showing the importance of the mPFC for working-memory tasks; (2) 93.7% mPFC cells (449 in 479) exhibited changes in spiking frequency that were temporally locked with the task events, some of which, including delay-related cells, were tuned by spatial information; (3) differential delay activities in individual mPFC cells appeared transiently and sequentially along the delay, especially during the early phase of the delay; (4) some mPFC cells showed no change in discharge frequency but exhibited differential synchronization in firing during the delay. The present results suggest that mPFC neurons in rats are involved in encoding working memory, via increasing firing frequency or synchronization.
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Brain and Law: An EEG Study of How We Decide or Not to Implement a Law

Brain and Law: An EEG Study of How We Decide or Not to Implement a Law

YA arguments were socially driven, which was typical for arguments in favor of any gun control in a variety of societies. ToM refers to the ability to attribute mental states to others and the ability to infer the emotional experiences of others (empathy), which are important processes in social cognition. Brain imaging studies in healthy subjects have described a brain system involving the medial prefrontal cortex, inferior frontal gyrus (IFG), superior temporal sulcus and temporal pole in ToM processing [7] [26]. In addition, the role of IFG in ToM circuits has been thought to block self-centered reasoning [8] [10] [27] [28]. YA sources were located at all these areas (Figure 2 and Figure 3) and while IFG located at BA 47 is common to both YA and NA analysis, IFG located at BA 45 is part of P 2 in YA case but not in NA case. Taken together, these results corroborate the
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Neural mechanisms of economic commitment in the human medial prefrontal cortex

Neural mechanisms of economic commitment in the human medial prefrontal cortex

food item to consume (Rushworth et al., 2011). These decisions depend on the momentary utility of a stimulus, that is, the reward that would accrue if that stimulus were to be consumed or disbursed all at once, whether immediately or (as in inter-temporal choice) after a delay (Kable and Glimcher, 2007). However, many (perhaps most) economic behaviours are not well captured by this paradigm, because rather than involving successive, independent choices, they require investment—that is, long-term commitment to a prospect in anticipation of sustained economic return, and with penalties incurred by any future change of mind. For example, the benefits of choosing the right employment could persist for many years into the future, whereas a poor decision about which mobile telephone to purchase might cause frustration for several months. Other decisions reverse a previous commitment, for example when deciding to sell stock options or to end a failing relationship. In these types of decision, which we refer to as economic ‘commitments’, prospects are irreversibly ‘ruled in’ (i.e., by acceptance) or ‘ruled out’ (i.e., by rejection) of a portfolio of assets that yield sustained positive or negative return to the individual. Unlike the choices made in most current lab-based approaches, economic commitments are not independent: a decision made at a time t continues to contribute to economic return at a later time t + 1, and may influence other choices made at that time. The aim of the current work was to understand the computational mechanisms by which economic commitments are made in humans, and to investigate their neural implementation in the reward circuitry of the medial prefrontal cortex.
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Category-Specific Item Recognition and the Medial Temporal Lobe

Category-Specific Item Recognition and the Medial Temporal Lobe

A comprehensive model of MTL contributions to recognition memory that can account for extant neuropsychological and fMRI evidence and accommodate the results presented in the current thesis is currently lacking. Given the seeming importance of categorical information in the ventral visual stream together with its high degree of connectivity with the MTL, a framework for the development of such a model should be consistent with the organizational structure of representations pertaining to visually presented stimuli in the ventral temporal cortex. Results from a number of studies suggest that VTC codes categorical information in distributed and overlapping representations (e.g., Haxby et al., 2001; Kriegeskorte et al., 2008). Importantly, similar conclusions can be drawn from findings revealed using MVPA to decode categorical information from PrC and PhC (e.g., Diana et al., 2008; Liang et al., 2013; Huffman and Stark, 2014). The ability to decode category membership from such representations is predicated on greater similarity in distributed responses for stimuli from the same category than for distributed responses from a different category (i.e., representations generalize across stimuli from the same category). The work that I have presented here extends this general framework by revealing that patterns of activity in PrC and PhC that differentiate familiar from novel recognition responses generalize across stimuli from the same category, but not to other categories (i.e., inability to cross-classify in Chapters 2 and 3). For example, at one level, distributed PrC responses corresponding to faces are more similar to one another than they are to those corresponding to stimuli from different categories (e.g., chairs). At another level, the distributed responses corresponding to familiar faces are also more comparable to one another than they are to those corresponding to faces judged to be novel (see Grill-Spector and Weiner, 2014, for related proposals regarding VTC).
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An investigation of the functional neuroanatomy of action ideation

An investigation of the functional neuroanatomy of action ideation

Several neuroimaging studies have also investigated the observation of gestures (Bonda et al., 1996; Decety et al., 1994,1997; Grafton et al., 1996; Grezes et al., 1998, 1999). These experiments suggest a segregation of the neural correlates for the conceptual (ideational) and production (ideomotor) components of action. The left frontal and temporal regions appear to be involved in a conceptual action system since they are preferentially activated when the observed gestures have meaning as compared to no meaning (Decety et al., 1994,1997; Grezes et al. 1998). As to the role of the anterior inferior parietal region (BA 40; AIP) the evidence is divided. In Chapter 2, the intraparietal sulcus (between AIP and the superior parietal lobule) was found to be involved in associating a manual response with a visual symbol (see Table 1.3). For this reason I suggested that it could be involved in action planning/ideation. The surrounding AIP cortex has also been implicated in praxis tasks (Heilman et al. 1982; Haaland et al. 1999). Also in the primate, neurons in a homologous region have been found to respond both to the presentation of objects and during grasping movements directed toward these objects (Sakata 1995; Taira 1990). However the precise function of AIP in human praxis has not been clearly established. The neuroimaging literature, in contrast to the neuropsychological and primate literature, suggests that AIP may be involved in the production rather than the conceptualisation of manual actions. For example, functional neuroimaging experiments have shown it to be activated by:
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