Lateral asymmetry in phonological processing: relating behavioral measures to neuroimaged structures

Recent neuroimaging studies have revealed neuroanatomical centers of activation that appear to be linked specifically to phonological processes. Furthermore, there is evidence that these centers of activation are more likely to be bilaterally represented in women than in men. However, behavioral evidence of such hemispheric asymmetries or of related sex differences is somewhat inconsistent. Two experiments were carried out to determine whether behavioral correlates of the neuroimaging findings could be demonstrated. The first experiment employed a rhyme-matching task used in a recent neuroimaging study, in which two nonsense words were projected successively to the left or right sides of the visual field. The results indicated that the left hemisphere was superior for this task. An analysis of gender effects, however, revealed that the asymmetry was restricted to men. The second experiment employed a lateralized pseudohomophone detection task that was designed to determine whether the results of the first experiment could be confirmed in the context of a phonological task with a simpler structure. This experiment broadly supported the findings of the first experiment. The results support the specialization of the left hemisphere for phonological processing, and the existence of gender differences with respect to these processes.     

The brain's hemispheres and controlled search of the lexicon: evidence from fixated words and pseudowords

Difference between the brain's hemispheres in efficiency of intentional search of the mental lexicon with phonological, orthographic, and semantic strategies was investigated. Letter strings for lexical decision were presented at fixation, with a lateralized distractor to the LVF or RVF. Word results revealed that both hemispheres were capable of using each of the three strategies, but the right hemisphere had better baseline processing of orthography and was better at processing semantics. Pseudoword results supported the right hemisphere advantage for orthography and showed a left hemisphere advantage for phonology and assessment of possible semantic relationships. Taken together, the data support the idea that the right hemisphere uses orthography to make efficient decisions about novelty of an item, while the left engages in grapheme-to-phoneme conversion to test hypotheses about unfamiliar items. The convergence of data with previous research reveals that the procedure, as well as analyses of pseudowords, inform laterality research.     

汉字认知的“复脑效应”的实验研究

该研究探讨了汉字的字形、字音、字义认知上的大脑两半球的功能差异。实验一使用同一的“汉字对”刺激材料,三组被试分别进行了字形、字音、字义异／同判断,结果发现反应时和正确反应率均表明,字形、字音、字义认知均与两个大脑半球有关,显示出了汉字认知的“复脑效应”。实验二使用“汉字－图形”意义整合判断课题进一步检验了字义认知的“复脑效应”,结果与实验一相同。作者认为,汉字认知的“复脑效应”与汉字本身的特点是分不开的。     

认知过程中大脑两半球的协同活动——若干实验结果的分析和再分析

本文对以往裂脑患者、右半球摘除患者和正常被试的若干实验结果进行了综合性的二次分析;同时对双脑协同活动的机制进行了讨论。依据实验资料提出双脑协同话动的两种可能的模式:〈1〉双脑互补模式;〈2〉双脑互扰模式。 统览以往文献,觉得把实验数据的算术平均数或某些概率运算的结果作为大脑一侧优势的指标可能是欠妥当的,因为它忽略了数据本身的性质。依据从三种视野所分别获得的数据可能具有向量性质,故建议: 〈1〉用左、右视野所获数据的向量差作为双脑协同活动中协同程度或协同水平的指标; 〈2〉把三组数据放在平面直角坐标系中分析,把左、右视野数据与中问视野数据之间的夹角差数作为单侧视野相对认知优势的指标。     

Hemispheric asymmetries in the split-fovea model of semantic processing

We report a series of neural network models of semantic processing of single English words in the left and the right hemispheres of the brain. We implement the foveal splitting of the visual field and assess the influence of this splitting on a mapping from orthography to semantic representations in single word reading. The models were trained on English four-letter words, presented according to their frequency in all positions encountered during normal reading. The architecture of the model interacted with the training set to produce processing asymmetries comparable to those found in behavioral studies. First, the cueing effects of dominant and subordinate meanings of ambiguous words were different for words presented to the left or to the right of the input layer. Second, priming effects of groups of related words were stronger in the left input than the right input of the model. These effects were caused by coarser-coding in the right half compared with the left half of the model, an emergent effect of the split model interacting with informational asymmetries in the left and right parts of words in the lexicon of English. Some or all of the behavioral data for reading single words in English may have a similar origin.     

Dissociating prelexical and postlexical processing of affective information in the two hemispheres: effects of the stimulus presentation format

Using a lexical decision task, the authors investigated whether brain asymmetries in the detection of emotionally negative semantic associations arise only at a perceptually discriminative stage at which lexical analysis is accurate or can already be found at crude and incomplete levels of perceptual representation at which word-nonword discrimination is based solely on guessing. Emotionally negative and neutral items were presented near perceptual threshold in the left and right visual hemifields. Word-nonword discrimination performance as well as the bias to classify a stimulus as a "word" (whether or not it actually is a word) were assessed for a normal, horizontal stimulus presentation format (Experiment 1) and for an unusual, vertical presentation format (Experiment 2). Results show that while the two hemispheres are equally able to detect affective semantic associations at a prelexical processing stage (both experiments), the right hemisphere is superior at a postlexical, perceptually discriminative stage (Experiment 2). Moreover, the findings suggest that only an unusual, nonoverlearned stimulus presentation format allows adequate assessment of the right hemisphere's lexical-semantic skills.     

`Theoretical' and `Empirical' Reasoning Modes from the Neurological Perspective

Two modes of reasoning are used by humans – the `theoretical' (formal) and the `empirical' (non-formal), the first operating with inside-the-syllogism information, the second utilising out-of-the-syllogism information. Cross-cultural research (since Lévy-Bruhl, and especially after Luria) and developmental research (since Piaget) discovered respectively that members of `traditional' societies and children up to a certain age are able to operate only in the empirical mode.The paper brings together diverse discussions about usage of these modes in actual discourse (Ennis, Johnson-Laird, Moore, Olson, Ong, etc.). It concentrates on contradictory opinions as to whether contemporary individuals after they acquire the formal mode preserve and utilise the empirical mode. In this connection it discusses results of neurological experiments investigating performance in solving syllogisms under conditions of transitory suppression of the left or the right hemisphere (Deglin et al.) which demonstrated that one and the same person, depending on which hemisphere is suppressed, uses both strategies. The activated right hemisphere utilizes the `empirical' pattern, the activated left hemisphere utilizes the `logical' pattern. Thus both mechanisms of reasoning are present in the brain simultaneously, but each of them is controlled by different hemispheres.     

学生智力与反应时的关系的教育神经心理学研究

通过比较不同智商者的大脑两半球的反应时发现,小学生中智力较高者大脑西半球的反应时较智力较低者明显为短,说明智力水平与大脑反应明显相关;选择反应时与智力水平的关系较简单反应时尤为密切。但正确反应率在两组之间未见有明显差异。     

语篇主题表征在大脑两半球的存贮

使用半视野速示技术和启动—再认探测方法,采用包含两个句子的短语篇作为前行信息、通过主题启动、歧义词启动探测语段阅读时主题表征在大脑两半球的存贮情况,结果发现,无论是主题启动还是歧义词启动,左视野／右半脑和右视野／左半脑对语境相关的目标词反应时间都比不一致目标词更长,说明语段阅读后两半脑对主题表征都有存贮。     

Effects of sentential context on the processing of unambiguous words by the two cerebral hemispheres

The effect of sentence context on the processing of different aspects of meaning of unambiguous nouns by the two cerebral hemispheres was examined. Participants performed a lexical decision task on target words following two primes, an unambiguous noun preceded by an incomplete sentence. Priming sentences were consistent with either the dominant or the subordinate aspect of meaning of their final unambiguous word. Short and long SOAs were used. A principal finding of this study was that, when compared to unrelated aspects of meaning, for both the short and the long SOAs, the dominant and subordinate aspects of meaning of the unambiguous words were activated regardless of context in both hemispheres. However, the activation of the subordinate aspect of meaning of unambiguous words appears to be more sensitive to sentential context, especially when the unambiguous word is being processed by the left hemisphere.