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GNA13 is the most frequently mutated gene in germinal center (GC)-derived B-cell lymphomas, including nearly a quarter of Burkitt lymphoma and GC-derived diffuse large B-cell lymphoma. These mutations occur in a pattern consistent with loss of function. We have modeled the GNA13-deficient state exclusively in GC B cells by crossing the Gna13 conditional knockout mouse strain with the GC-specific AID-Cre transgenic strain. AID-Cre+ GNA13-deficient mice demonstrate disordered GC architecture and dark zone/light zone distribution in vivo, and demonstrate altered migration behavior, decreased levels of filamentous actin, and attenuated RhoA activity in vitro. We also found that GNA13-deficient mice have increased numbers of GC B cells that display impaired caspase-mediated cell death and increased frequency of somatic hypermutation in the immunoglobulin VH locus. Lastly, GNA13 deficiency, combined with conditional MYC transgene expression in mouse GC B cells, promotes lymphomagenesis. Thus, GNA13 loss is associated with GC B-cell persistence, in which impaired apoptosis and ongoing somatic hypermutation may lead to an increased risk of lymphoma development.

This study investigates the phonological processing that Taiwanese deaf signers engage in when recognizing Chinese characters and words. The deaf participants’ orthography–phonology transformation (OPT) abilities were tested using an explicit Chinese homophone judgment task, and their implicit phonological activations were tested using lexical decision tasks. Chinese characters, whose phonetic radicals are not always reliable guides to pronunciation, are a useful tool for dissociating the influence of phonology and orthography. Experiment 1 manipulated sound-based phonological similarity (similar, dissimilar) and orthographical similarity (similar, dissimilar). Accuracy, sensitivity (d′), and reaction times (RTs) were recorded for hearing participants, but only accuracy and sensitivity (d′) recorded for deaf participants, who are fluent signers of Taiwanese Sign Language (TSL). Additionally, the predictive abilities of log word frequency and the consistency values for homophone judgment performance were analyzed. Experiment 2-1 was designed to compare the effects of three primes (semantically related, sound-based phonologically related, and unrelated primes) on the performance of deaf and hearing participants on a lexical decision task. In Experiment 2-2, TSL phonologically related primes were compared with unrelated primes for deaf and hearing subjects. The results of Experiment 1 show that the accuracy of deaf subjects was poor (.66) and was lower than that of hearing subjects (.87). Particularly, the deaf subjects’ accuracy and sensitivity in the orthographically dissimilar condition were significantly lower than in the orthographically similar condition. For hearing subjects, log word frequency significantly predicted their accuracy and RTs, whereas the consistency values predicted only the RTs. For the deaf participants, the accuracy could be efficiently predicted by both log word frequency and consistency values, which reflect knowledge of OPT rules. We suggested that although deaf individuals had acquired knowledge of OPT rules, this knowledge was neither complete nor sufficiently robust to make homophone judgments. In Experiment 2-1, the results show that there was a semantic priming effect but no sound-based phonological priming effect for the deaf participants. The results further reveal that deaf people with a limited hearing ability did not automatically process the sound-based phonological representations under time-constrained conditions. In Experiment 2-2, there was an action-based phonological priming effect for deaf signers but not for hearing subjects, indicating that deaf signers automatically activated related action-based phonology to access the semantic meaning of words when reading Chinese. This study finds that deaf signers acquire OPT rules but that their OPT rules are not sufficiently robust or complete to allow them to make explicit phonological judgments and homophone judgments. Deaf signers automatically activated action-based representations rather than sound-based phonological representations when reading Chinese characters.

Visual half-field experiments have been used to investigate perceptual differences in reading different types of writing scripts. It has been observed that tachistoscopic recognition of phonetic-based scripts (such as the English alphabet and Japanese Kana) tends to show a right visual field–left hemisphere (RVF-LH) superiority effect1,2whereas recognition of logographic symbols (for example, Chinese characters) tends to show a left visual field–right hemisphere (LVF-RH) superiority effect3,4. A cerebral orthography-specific localisation hypothesis has been proposed to account for these data. We have conducted three experiments to examine the visual lateralisation effect in reading logographic symbols such as Chinese characters. Chinese subjects in the first experiment were exposed to brief tachistoscopic presentation of a single character, and their task was to name the character as soon as possible. A LVF-RH superiority was found. In the second experiment, the stimuli were two vertically arranged characters and the subjects were asked to name the stimulus terms as soon as possible. The third experiment was the same as the second except that the task was to decide whether these character-strings were correct semantic terms with a manual response. A RVF-LH superiority effect was found in both the second and third experiments. These differential visual lateralisation results were interpreted as reflecting the function-specific property of the two hemispheres and cast doubt on the orthography-specific localisation hypothesis proposed by earlier investigators.

THE systematic study of behavioural differences related to differential functioning of the cerebral hemispheres has increased markedly in recent years. The studies of Sperry and his collaborators1on cerebral commissurotomy patients have stimulated many investigations into the hemisphere specialisations of normally functioning subjects. There are now many reports2,3of statistically significant differences in hemisphere performance. Although hemisphere differences are consistent across independent experiments, they are small, occasionally inconsistent, and found within a limited experimental context, and so the generality of hemisphere differences remains to be established. We present here brief accounts of six experiments on cerebral lateralisation, four of which failed to find any differences and two which produced highly significant hemisphere differences. On the basis of this and published work, we believe that we can offer both a possible explanation for both the presence and absence of cerebral lateralisation effects in visual half-field experiments and also procedural guidelines that will produce cerebral lateralisation effects.

A MAJOR concern of current memory research is to identify how information is encoded and transferred from short term memory (STM) to long term memory (LTM)1,2. It has been reasoned that while an item remains in STM, it can be maintained through rehearsal; as a consequence, the corresponding LTM trace is built up. Thus, one may postulate that the adequacy of an item's registration in LTM is a positive function of the length of its stay in STM. Such a mechanical and simplistic account of memory has been challenged by a series of experiments which showed that when short term storage times were measured, these times did not predict long term retention3,4. We report here an experiment which manipulated the processing time as well as the processing context and showed that the processing time had differential effects, sometimes beneficial, sometimes harmful, and sometimes neutral, on an item's long term retention, depending in which type of processing context the item was embedded. Such results argue for a perceiver–environment interactive theory of memory.