RESUMO
The ongoing reproducibility crisis in psychology and cognitive neuroscience has sparked increasing calls to re-evaluate and reshape scientific culture and practices. Heeding those calls, we have recently launched the EEGManyPipelines project as a means to assess the robustness of EEG research in naturalistic conditions and experiment with an alternative model of conducting scientific research. One hundred sixty-eight analyst teams, encompassing 396 individual researchers from 37 countries, independently analyzed the same unpublished, representative EEG data set to test the same set of predefined hypotheses and then provided their analysis pipelines and reported outcomes. Here, we lay out how large-scale scientific projects can be set up in a grassroots, community-driven manner without a central organizing laboratory. We explain our recruitment strategy, our guidance for analysts, the eventual outputs of this project, and how it might have a lasting impact on the field.
Assuntos
Eletroencefalografia , Projetos de Pesquisa , Humanos , Reprodutibilidade dos TestesRESUMO
A recent Cyberball study has indicated that the experience of loss of control can affect how people process subsequent social exclusion. This "preexposure effect" supports the idea of a common cognitive system involved in the processing of different types of social threats. To test the validity of this assumption in the current study, we reversed the sequence of the preexposure setup. We measured the effects of social exclusion on the subsequent processing of loss of control utilizing event-related brain potentials (ERPs) and self-reports. In the control group (CG, n = 26), the transition to loss of control elicited significant increases in both the P3 amplitude and the self-reported negative mood. Replicating the results of the previous preexposure study, these effects were significantly reduced by the preexposure to an independent social threat (here: social exclusion). In contrast to previous findings, these effects were not modulated by the discontinuation (EG1disc, n = 25) or continuation (EG2cont, n = 24) of the preexposure threat. Given that the P3 effect is related to the violation of subjective expectations, these results support the notion that preexposure to a specific social threat has widespread effects on the individuals' expectancy of upcoming social participation and control.
Assuntos
Eletroencefalografia , Percepção Social , Humanos , Potenciais Evocados/fisiologia , Encéfalo/fisiologia , Isolamento SocialRESUMO
An important issue facing the empirical study of consciousness concerns how the contents of incoming stimuli gain access to conscious processing. According to classic theories, facial stimuli are processed in a hierarchical manner. However, it remains unclear how the brain determines which level of stimulus content is consciously accessible when facing an incoming facial stimulus. Accordingly, with a magnetoencephalography technique, this study aims to investigate the temporal dynamics of the neural mechanism mediating which level of stimulus content is consciously accessible. Participants were instructed to view masked target faces at threshold so that, according to behavioral responses, their perceptual awareness alternated from consciously accessing facial identity in some trials to being able to consciously access facial configuration features but not facial identity in other trials. Conscious access at these two levels of facial contents were associated with a series of differential neural events. Before target presentation, different patterns of phase angle adjustment were observed between the two types of conscious access. This effect was followed by stronger phase clustering for awareness of facial identity immediately during stimulus presentation. After target onset, conscious access to facial identity, as opposed to facial configural features, was able to elicit more robust late positivity. In conclusion, we suggest that the stages of neural events, ranging from prestimulus to stimulus-related activities, may operate in combination to determine which level of stimulus contents is consciously accessed. Conscious access may thus be better construed as comprising various forms that depend on the level of stimulus contents accessed. NEW & NOTEWORTHY The present study investigates how the brain determines which level of stimulus contents is consciously accessible when facing an incoming facial stimulus. Using magnetoencephalography, we show that prestimulus activities together with stimulus-related activities may operate in combination to determine conscious face detection or identification. This finding is distinct from the previous notion that conscious face detection precedes identification and provides novel insights into the temporal dynamics of different levels of conscious face perception.
Assuntos
Ritmo alfa/fisiologia , Córtex Cerebral/fisiologia , Estado de Consciência/fisiologia , Potenciais Evocados P300/fisiologia , Reconhecimento Facial/fisiologia , Magnetoencefalografia/métodos , Mascaramento Perceptivo/fisiologia , Reconhecimento Psicológico/fisiologia , Adulto , Feminino , Humanos , Masculino , Fatores de Tempo , Adulto JovemRESUMO
An Electroencephalography (EEG) dataset utilizing rich text stimuli can advance the understanding of how the brain encodes semantic information and contribute to semantic decoding in brain-computer interface (BCI). Addressing the scarcity of EEG datasets featuring Chinese linguistic stimuli, we present the ChineseEEG dataset, a high-density EEG dataset complemented by simultaneous eye-tracking recordings. This dataset was compiled while 10 participants silently read approximately 13 hours of Chinese text from two well-known novels. This dataset provides long-duration EEG recordings, along with pre-processed EEG sensor-level data and semantic embeddings of reading materials extracted by a pre-trained natural language processing (NLP) model. As a pilot EEG dataset derived from natural Chinese linguistic stimuli, ChineseEEG can significantly support research across neuroscience, NLP, and linguistics. It establishes a benchmark dataset for Chinese semantic decoding, aids in the development of BCIs, and facilitates the exploration of alignment between large language models and human cognitive processes. It can also aid research into the brain's mechanisms of language processing within the context of the Chinese natural language.
Assuntos
Eletroencefalografia , Semântica , Humanos , Encéfalo/fisiologia , Interfaces Cérebro-Computador , China , Idioma , Linguística , Processamento de Linguagem Natural , LeituraRESUMO
Experiencing a social threat, such as social exclusion, is a painful event. In contrast to previous studies providing insight into the processing of a single short-termed threat, we exposed healthy individuals to the simultaneous onset of different social threats. This approach allowed us to track whether these threats are processed independently-or whether they interact in a common system. Using a virtual ball-throwing game (Cyberball), electrophysiological (event-related brain potentials, ERPs) and behavioral (self-reports) responses were collected. We assigned undergraduates to three experimental groups: single threat exclusion (n = 24), single threat loss of control (n = 26), and joint onset of both threats (dual-threat, n = 25). Self-reports indicated an increase in threats (i.e., in perceived exclusion and loss-of-control) in the latter group. The ERPs disentangled the neural responses to each threat: In the dual-threat group, the amplitudes of the P3 responses to exclusionary and intervention events were enhanced. This indicates that individuals are sensitized to each of the threats when the other threat is present simultaneously. Our findings support the theoretical notion of a common cognitive system responding to violations in subjective expectations.
Assuntos
Encéfalo , Potenciais Evocados , Humanos , Potenciais Evocados/fisiologia , Encéfalo/fisiologia , Isolamento Social/psicologia , Jogos ExperimentaisRESUMO
[This corrects the article DOI: 10.3389/fphar.2021.621359.].
RESUMO
Previous studies indicated that the onsets of different social threats, such as threats to "belonging" and "control", are inconsistent with the subjective beliefs of social participation and require readjustment of expectations. Because a common cognitive system is assumed to be involved, the adjustment triggered by the experience of a single social threat should affect the processing of subsequent social interactions. We examined how preexposure to a loss of control affected social exclusion processing by using the Cyberball paradigm. An event-related brain component (P3) served as a probe for the state of the expectancy system, and self-reports reflected the subjective evaluations of the social threats. In the control group (n = 23), the transition to exclusion elicited a significant P3 effect and a high threat to belonging in the self-reports. Both effects were significantly reduced when the exclusion was preceded by preexposure to a loss of control (EG1disc, n = 23). These effects, however, depend on the offset of the preexposure. In case of a continuation (EG2cont, n = 24), the P3 effect was further reduced, but the threat to belonging was restored. We conclude that the P3 data are consistent with predictions of a common expectancy violation account, whereas self-reports are supposed to be affected by additional processes.
RESUMO
The ability to detect faces in the environment is of utmost ecological importance for human social adaptation. While face categorization is efficient, fast and robust to sensory degradation, it is massively impaired when the facial stimulus does not match the natural contrast statistics of this visual category, i.e., the typically experienced ordered alternation of relatively darker and lighter regions of the face. To clarify this phenomenon, we characterized the contribution of natural contrast statistics to face categorization. Specifically, 31 human adults viewed various natural images of nonface categories at a rate of 12 Hz, with highly variable images of faces occurring every eight stimuli (1.5 Hz). As in previous studies, neural responses at 1.5 Hz as measured with high-density electroencephalography (EEG) provided an objective neural index of face categorization. Here, when face images were shown in their naturally experienced contrast statistics, the 1.5-Hz face categorization response emerged over occipito-temporal electrodes at very low contrast [5.1%, or 0.009 root-mean-square (RMS) contrast], quickly reaching optimal amplitude at 22.6% of contrast (i.e., RMS contrast of 0.041). Despite contrast negation preserving an image's spectral and geometrical properties, negative contrast images required twice as much contrast to trigger a face categorization response, and three times as much to reach optimum. These observations characterize how the internally stored natural contrast statistics of the face category facilitate visual processing for the sake of fast and efficient face categorization.
Assuntos
Encéfalo , Eletroencefalografia , Adulto , Encéfalo/fisiologia , Eletroencefalografia/métodos , Humanos , Reconhecimento Visual de Modelos/fisiologia , Estimulação Luminosa/métodos , Percepção VisualRESUMO
Compound Dihuang Granule (CDG) is widely used in traditional Chinese medicine (TCM) for the treatment of Parkinson's disease (PD). It has been shown to alleviate PD symptoms. However, the molecular mechanisms of its action have not been established. To establish the molecular mechanisms of CDG against PD, we used TCM network pharmacology methods to predict its molecular targets and signaling pathways, followed by experimental validation. The Core Protein protein interaction (PPI) network of the 150 intersections between CDG and PD-related genes, comprising 23 proteins, including CASP3 (caspase-3), MAPK8 (JNK), FOS (c-Fos), and JUN (c-Jun). KEGG and GO analyses revealed that apoptotic regulation and MAPK signaling pathways were significantly enriched. Since c-Jun and c-Fos are AP-1 subunits, an important downstream JNK effector, we investigated if the JNK/AP-1 pathway influences CDG against apoptosis through the nigrostriatal pathways in PD rat models. Molecular docking analysis found that the top three bioactive compounds exhibiting the highest Degree Centrality following online database and LC-MS analysis had high affinities for JNK. Experimental validation analysis showed that CDG decreased the number of rotating laps and suppressed the levels of phosphorylated c-Jun, c-Fos, and JNK, as well as the number of TUNEL positive cells and the cleaved caspase-3 level in the nigrostriatal pathway. Furthermore, CDG treatment elevated the number of TH neurons, TH expression level, and Bcl-2/Bax protein ratio in a 6-OHDA-induced PD rat. These findings are in tandem with those obtained using SP600125, a specific JNK inhibitor. In conclusion, CDG suppresses the apoptosis of the nigrostriatal pathway and relieves PD symptoms by suppressing the JNK/AP-1 signaling pathway.
RESUMO
ETHNOPHARMACOLOGICAL RELEVANCE: Rheum palmatum L; Astragalus membranaceus (Fisch.), is referred to as 'Dahuang, Huangqi' in China. As an important medicinal plant, the rhizome of rhubarb and astragalus is traditionally used in the treatment of kidney diseases associated with renal failure, inflammation and tumors. AIM OF THE STUDY: This study aimed to investigate the effect of a drug-containing serum of rhubarb-astragalus capsules (composed of rhubarb and astragalus) and to elucidate its mechanism in the epithelial-mesenchymal transformation of renal tubular epithelial cells. MATERIALS AND METHODS: Epithelial-mesenchymal transformation (EMT) of HK-2 cells was induced by TGF-ß1, and rhubarb-astragalus and losartan drug-containing serum from rats, as well as SB203580 (a specific inhibitor of p38 MAPK), were used. High-performance liquid chromatography analysis was performed to determine the main components of the drug-containing serum of rhubarb-astragalus from rats. Western blotting and immunofluorescence analysis were used to determine the levels of protein expression, and real-time quantitative PCR analysis was used to detect the levels of gene expression. RESULTS: The drug-containing serum of rhubarb-astragalus contained emodin (0.36 µg/ml) and danthraquinone (0.96 µg/ml). Rhubarb-astragalus significantly decreased the protein expression levels of α-SMA, FN, vimentin and N-cadherin in HK-2 cells that were increased by TGF-ß1, while it significantly increased the E-cadherin protein expression level that was decreased by TGF-ß1. Rhubarb-astragalus also significantly decreased the protein expression levels of TGF-ß1 and p38 MAPK and the mRNA expression levels of α-SMA, vimentin, TGF-ß1, p38 MAPK, Smad2 and Smad3 in HK-2 cells that were increased by TGF-ß1. It is worth noting that SB203580 (a p38 MAPK inhibitor) had similar effects as rhubarb-astragalus in this study. CONCLUSION: The drug-containing serum of rhubarb-astragalus can inhibit EMT in HK-2 cells by downregulating the TGF-ß1/p38 MAPK/Smad2/3 pathway.
Assuntos
Astrágalo , Células Epiteliais/efeitos dos fármacos , Transição Epitelial-Mesenquimal/efeitos dos fármacos , Rheum , Fator de Crescimento Transformador beta1/metabolismo , Animais , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Regulação para Baixo/efeitos dos fármacos , Emodina/administração & dosagem , Emodina/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Imidazóis/farmacologia , Túbulos Renais/citologia , Masculino , Piridinas/farmacologia , Ratos , Ratos Sprague-Dawley , Proteína Smad2/genética , Proteína Smad2/metabolismo , Proteína Smad3/genética , Proteína Smad3/metabolismo , Fator de Crescimento Transformador beta1/genética , Proteínas Quinases p38 Ativadas por Mitógeno/genética , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
Brainhack is an innovative meeting format that promotes scientific collaboration and education in an open, inclusive environment. This NeuroView describes the myriad benefits for participants and the research community and how Brainhacks complement conventional formats to augment scientific progress.
Assuntos
Comunicação , Internet , Neurociências/organização & administração , Congressos como Assunto , Guias de Prática Clínica como AssuntoRESUMO
The human brain is tuned to recognize emotional facial expressions in faces having a natural upright orientation. The relative contributions of featural, configural, and holistic processing to decision-making are as yet poorly understood. This study used a diffusion decision model (DDM) of decision-making to investigate the contribution of early face-sensitive processes to emotion recognition from physiognomic features (the eyes, nose, and mouth) by determining how experimental conditions tapping those processes affect early face-sensitive neuroelectric reflections (P100, N170, and P250) of processes determining evidence accumulation at the behavioral level. We first examined the effects of both stimulus orientation (upright vs. inverted) and stimulus type (photographs vs. sketches) on behavior and neuroelectric components (amplitude and latency). Then, we explored the sources of variance common to the experimental effects on event-related potentials (ERPs) and the DDM parameters. Several results suggest that the N170 indicates core visual processing for emotion recognition decision-making: (a) the additive effect of stimulus inversion and impoverishment on N170 latency; and (b) multivariate analysis suggesting that N170 neuroelectric activity must be increased to counteract the detrimental effects of face inversion on drift rate and of stimulus impoverishment on the stimulus encoding component of non-decision times. Overall, our results show that emotion recognition is still possible even with degraded stimulation, but at a neurocognitive cost, reflecting the extent to which our brain struggles to accumulate sensory evidence of a given emotion. Accordingly, we theorize that: (a) the P100 neural generator would provide a holistic frame of reference to the face percept through categorical encoding; (b) the N170 neural generator would maintain the structural cohesiveness of the subtle configural variations in facial expressions across our experimental manipulations through coordinate encoding of the facial features; and (c) building on the previous configural processing, the neurons generating the P250 would be responsible for a normalization process adapting to the facial features to match the stimulus to internal representations of emotional expressions.
RESUMO
A variant of the picture-word interference paradigm was used in three experiments to investigate the horizontal information flow of semantic and phonological information between nouns in spoken Mandarin Chinese sentences. Experiment 1 demonstrated that there is a semantic interference effect when the word in the second phrase (N3) and the first noun in the initial phrase (N1) are semantically related, while there is no effect when N3 and the second noun in the initial phrase (N2) are semantically related. Experiments 2 and 3 showed that there is a phonological facilitation effect only when the two phonologically related words are both in the initial phrase, and there is no effect when they are in different phrases. Reinforcing the findings of an earlier study of horizontal information flow by Smith and Wheeldon (2004), our results indicate that there is a temporal overlap in the access of the nouns in spoken Mandarin Chinese sentences and a flow of semantic and phonological information between these nouns. Moreover, our results are incompatible with a wholly parallel view of horizontal information flow and instead provide support for a view which is partly serial and partly parallel in nature.
Assuntos
Idioma , Fonética , Psicolinguística , Semântica , Fala , China , HumanosRESUMO
In music, chords are organized into hierarchical structures on the basis of musical syntax and the syntax of Western music can be implicitly acquired by listeners growing up in a Western musical culture. Here, we investigated whether Western musical syntax of different complexities can be implicitly acquired by non-native listeners growing up in China. This study used electroencephalography (EEG) to measure how the neural responses to musical sequences that either follow a simple rule, i.e., finite state grammar (FSG), or a complex rule, i.e., phrase structure grammar (PSG), are affected. We tested three groups of Chinese listeners who varied in their proficiency and experience in Western music. Only the high-proficiency group had received formal Western musical training, whereas the low- and moderate-proficiency groups varied in their degree of exposure to Western music. The results showed that in the FSG condition, the event-related potentials (ERPs) evoked by regular and irregular final chords were not significantly different in the low-proficiency group. In contrast, in the moderate- and high-proficiency groups, the irregular final chords evoked an ERAN-N5 biphasic response. In the PSG condition, however, only the high-proficiency group showed an ERAN-N5 biphasic response evoked by irregular final chords. This study provides evidence that although simple structures of Western music, such as FSG, can be acquired by long-term implicit learning, the acquisition of more complex structures, such as PSG, merely from exposure to western music may not be as easy.
Assuntos
Percepção Auditiva/fisiologia , Encéfalo/fisiologia , Aprendizagem/fisiologia , Música , Cultura , Eletroencefalografia , Potenciais Evocados Auditivos , Feminino , Humanos , Masculino , Competência Profissional , Adulto JovemRESUMO
In music, chords are organized into hierarchical structures based on recursive or embedded syntax. How the brain extracts recursive grammar is a central question in musical cognition and other cognitive neuroscience, but the precise mechanism remains unclear. By analyzing event related potentials (ERPs) and neural oscillatory activity, the present study investigated neurocognitive mechanisms underlying the processing of center-embedded structure in music by examining the differences in center-embedded and non-embedded structure processing and evaluating how these differences are affected by musical proficiency. Based on Western musical proficiency, the subjects were divided into two groups, non-experts and experts. The results revealed that for non-experts, the processing of center-embedded structure elicited greater early right-anterior negativity (ERAN) and N5 components as well as, reduced alpha and gamma activities than did the non-embedded structure. For experts, no significant difference in the ERP response was observed between the processing of non-embedded and center-embedded structures; however, the processing of center-embedded structure elicited increased beta activity compared to non-embedded structure. These findings indicate that listeners different in proficiency would rely on different cognitive neural mechanisms in music processing with the syntactic complexity increases.
RESUMO
When we observe a dynamic emotional facial expression, we usually automatically anticipate how that expression will develop. Our objective was to study a neurocognitive biomarker of this anticipatory process for facial pain expressions, operationalized as a mismatch effect. For this purpose, we studied the behavioral and neuroelectric (Event-Related Potential, ERP) correlates, of a match or mismatch, between the intensity of an expression of pain anticipated by the participant, and the intensity of a static test expression of pain displayed with the use of a representational momentum paradigm. Here, the paradigm consisted in displaying a dynamic facial pain expression which suddenly disappeared, and participants had to memorize the final intensity of the dynamic expression. We compared ERPs in response to congruent (intensity the same as the one memorized) and incongruent (intensity different from the one memorized) static expression intensities displayed after the dynamic expression. This paradigm allowed us to determine the amplitude and direction of this intensity anticipation by measuring the observer's memory bias. Results behaviorally showed that the anticipation was backward (negative memory bias) for high intensity expressions of pain (participants expected a return to a neutral state) and more forward (memory bias less negative, or even positive) for less intense expressions (participants expected increased intensity). Detecting mismatch (incongruent intensity) led to faster responses than detecting match (congruent intensity). The neuroelectric correlates of this mismatch effect in response to the testing of expression intensity ranged from P100 to LPP (Late Positive Potential). Path analysis and source localization suggested that the medial frontal gyrus was instrumental in mediating the mismatch effect through top-down influence on both the occipital and temporal regions. Moreover, having the facility to detect incongruent expressions, by anticipating emotional state, could be useful for prosocial behavior and the detection of trustworthiness.
Assuntos
Emoções/fisiologia , Dor/patologia , Adulto , Encéfalo/fisiologia , Mapeamento Encefálico , Eletroencefalografia , Potenciais Evocados/fisiologia , Expressão Facial , Feminino , Humanos , Masculino , Memória , Estimulação Luminosa , Adulto JovemRESUMO
The scope of lexical planning, which means how far ahead speakers plan lexically before they start producing an utterance, is an important issue for research into speech production, but remains highly controversial. The present research investigated this issue using the semantic blocking effect, which refers to the widely observed effects that participants take longer to say aloud the names of items in pictures when the pictures in a block of trials in an experiment depict items that belong to the same semantic category than different categories. As this effect is often interpreted as a reflection of difficulty in lexical selection, the current study took the semantic blocking effect and its associated pattern of event-related brain potentials (ERPs) as a proxy to test whether lexical planning during sentence production extends beyond the first noun when a subject noun-phrase includes two nouns, such as "The chair and the boat are both red" and "The chair above the boat is red". The results showed a semantic blocking effect both in onset latencies and in ERPs during the utterance of the first noun of these complex noun-phrases but not for the second noun. The indication, therefore, is that the lexical planning scope does not encompass this second noun-phrase. Indeed, the present findings are in line with accounts that propose radically incremental lexical planning, in which speakers plan ahead only one word at a time. This study also provides a highly novel example of using ERPs to examine the production of long utterances, and it is hoped the present demonstration of the effectiveness of this approach inspires further application of ERP techniques in this area of research.
Assuntos
Formação de Conceito/fisiologia , Potenciais Evocados/fisiologia , Idioma , Semântica , Fala/fisiologia , Comportamento Verbal/fisiologia , Adulto , Análise de Variância , Eletroencefalografia , Eletroculografia , Humanos , Estimulação Luminosa , Psicolinguística/métodos , Tempo de Reação/fisiologia , Medida da Produção da Fala/métodos , Adulto JovemRESUMO
OBJECTIVE: To investigate whether the Tiam1 gene expression enhances the invasive and metastatic capabilities of colorectal carcinoma cells. METHODS: Endogenous expression of Tiam1 in five colorectal carcinoma cell lines was investigated by RT-PCR. Tiam1/C1199HA cDNA was transfected into HT29, a colorectal carcinoma cell line without endogenous Tiam1 expression. RNA and protein expression of Tiam1 gene in the transfectants were detected by RT-PCR, immunohistochemistry and Western blot respectively. The biological behaviors of the transfectants were investigated by MTT and in-vitro invasion assays. RESULTS: Tiam1 gene was highly expressed in LoVo and SW620 cells. Low level expression was seen in HCT116 and SW480 and no expression was found in HT29. Transfection of Tiam1 significantly increased the proliferation of HT29 cells along with markedly enhanced in-vitro invasion and metastasis. CONCLUSIONS: Tiam1 gene plays an important role in the invasion and metastasis of colorectal carcinoma. It may be a useful marker for metastasis of colorectal carcinoma.
Assuntos
Proliferação de Células , Neoplasias Colorretais/patologia , Fatores de Troca do Nucleotídeo Guanina/genética , Biomarcadores Tumorais , Linhagem Celular Tumoral , Neoplasias Colorretais/genética , Neoplasias Colorretais/metabolismo , Regulação Neoplásica da Expressão Gênica , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Fatores de Troca do Nucleotídeo Guanina/fisiologia , Células HT29 , Humanos , Invasividade Neoplásica , Metástase Neoplásica , Proteína 1 Indutora de Invasão e Metástase de Linfoma de Células T , TransfecçãoRESUMO
OBJECTIVE: To construct the vector using specific nasopharynx tissue promoter plunc to establish transgeneic mouse model. METHODS: Plunc-EGFP plasmid was digested with XhoI, the purified linearized DNA fragments were recovered by gel extraction and diluted to the final concentration of 4 microg/ml, before introduced into fertilized one-cell mouse eggs by pronuclear microinjection. RESULTS: Thirteen founder mice were obtained, 12 of which were positive for the integrated EGFP gene as detected by PCR, and 3 were positive shown by Southern blotting. CONCLUSION: Specific nasopharynx tissue promoter plunc can effectively induce exogenous gene integration into the mouse genome.