Brendan S. Weekes

Differential Effects of Number of Letters on Word and Nonword Naming Latency

The issue addressed in this study is whether there are differential effects of number of letters on word and nonword naming latency. Experiment 1 examined the effect of number of letters on latency for naming high-frequency words, low-frequency words, and nonwords. Number of letters affected latency for low-frequency words and nonwords but did not affect latency for high-frequency words. Number of letters was also negatively correlated with number of orthographic neighbours, number of friends, and average grapheme frequency. Number of letters continued to affect nonword naming latency, but not low-frequency word naming latency, after the effects of orthographic neighbourhood size, number of friends, and average grapheme frequency had been accounted for. Experiment 2 found that number of letters had no effect on the latency of delayed naming of the same words and nonwords. It is concluded that the effect of number of letters on nonword naming reflects a sequential, non-lexical reading mechanism.

Processing of Visually Presented Sentences in Mandarin and English Studied with fMRI

Comprehension of visually presented sentences in fluent bilinguals was studied with functional magnetic resonance imaging (fMRI) using a set of conceptually similar sentences in two orthographically and phonologically distinct languages, Mandarin and English. Responses were monitored during scanning. Sentence comprehension in each language was compared to fixation in nine subjects and Tamil-like pseudo-word strings in five subjects. Spatially congruent activations in the prefrontal, temporal, and superior parietal regions and in the anterior supplementary motor area were observed for both languages and in both experiments at the individual and group levels of analysis. Proficient bilinguals exposed to both languages early in life utilize common neuroanatomical regions during the conceptual and syntactic processing of written language irrespective of their differences in surface features.

Overlap and dissociation of semantic processing of Chinese characters English words and pictures: Evidence from fMRI

The functional anatomy of Chinese character processing was investigated using fMRI. Right-handed Mandarin-English bilingual participants made either semantic or perceptual size judgements with characters and pictures. Areas jointly activated by character and picture semantic tasks compared to size judgement tasks included the left prefrontal region (BA 9, 44, 45), left posterior temporal, left fusiform, and left parietal regions. Character processing produced greater activation than picture processing in the left mid and posterior temporal as well as left prefrontal regions. The lateral occipital regions were more active during picture semantic processing than character semantic processing. A similar pattern of activation and contrasts was observed when English words and pictures were compared in another set of bilingual participants. However, there was less contrast between word and picture semantic processing than between character and picture processing in the left prefrontal region. When character and word semantic processing were compared directly in a third group, the loci of activation peaks was similar in both languages but Chinese character semantic processing was associated with a larger MR signal change. The semantic processing of Chinese characters, English words, and pictures activates a common semantic system within which there are modality-specific differences. The semantic processing of Chinese characters more closely resembles English words than pictures.

Visual and phonological pathways to the lexicon: evidence from Chinese readers.

In this study, we investigated the role of visual and phonological information in lexical access of Chinese characters. Homophonic English words have been the main source of stimuli for word recognition research. However, since these stimuli also often look alike, visual and phonological information may be confounded in reported experiments. In contrast, many homophonic Chinese characters are visually distinct. In addition, visually similar characters often have very different pronunciations. These characteristics allow a more controlled investigation of the roles of visual and phonological information in activation of meaning. In the present study, two types of Chinese characters were used in a semantic categorization paradigm: integrated characters, which contain strokes that are not separable; and compound characters, which contain at least two clearly identifiable components. The results show that the recognition of a Chinese integrated character depends primarily on visual information, whereas the recognition of a Chinese compound character relies on visual, phonological, and semantic information. It is concluded that visual information plays a greater role in Chinese character recognition than has previously been documented.

Surface Dyslexia and Surface Dysgraphia: Treatment Studies and Their Theoretical Implications

We report studies of a patient with acquired surface dyslexia and dysgraphia. His reading impairment was treated using the methods previously reported to be successful for surface dyslexia by Byng and Coltheart (1986); these methods were also successful with our patient. In addition, we observed, as Byng and Coltheart did, that when these methods are used there is incomplete but significant generalisation to the reading of untreated words. Connectionist simulations of the effects of damage to the language processing system have taken this generalisation effect to be evidence that words are represented in a distributed fashion in that system ; we challenge this inference, on the basis of data from our and Byng and Colthearts patient. Our patients spelling impairment was treated using the methods previously reported to be successful for surface dysgraphia by Behrmann (1987); these methods were also successful for our patient, and we found in addition, as did Behrmann, that the treatment effects upon spell...

Language proficiency modulates the engagement of cognitive control areas in multilinguals

Language proficiency should modulate the regions involved in language control in predictable ways during language switching. However, prior studies reveal inconsistent effects on the regions involved in language monitoring [pre-Supplementary Motor Area/Anterior Cingulate Cortex (pre-SMA/ACC)] and language selection (left caudate) conceivably because variations in relative proficiency are confounded with other between-group differences. We circumvented this problem in an fMRI (functional Magnetic Resonance Imaging) study of overt picture naming in trilingual participants. In this case, the difference between a high-proficient and a low-proficient further language can be assessed within subjects with no between-group confound. We also used a monolingual group to assess the neural correlates of switching between two categories of response within the same language. We report a novel result: relative language proficiency dissociates response of the pre-SMA/ACC and left caudate during language switching. Switching between languages increased pre-SMA/ACC response regardless of proficiency differences. By contrast, left caudate response did vary with proficiency differences. Switching from the most to the least proficient language increased the response. Within-language switching, as contrasted with between-language switching, elicited a comparable increase in pre-SMA/ACC response but a decrease in left caudate response. Taken together, our data support a wider role of pre-SMA/ACC in task monitoring and establish the critical role of the left caudate in the selection of the less proficient language in language switching.

Bilingualism protects anterior temporal lobe integrity in aging.

Cerebral gray-matter volume (GMV) decreases in normal aging but the extent of the decrease may be experience-dependent. Bilingualism may be one protective factor and in this article we examine its potential protective effect on GMV in a region that shows strong age-related decreases-the left anterior temporal pole. This region is held to function as a conceptual hub and might be expected to be a target of plastic changes in bilingual speakers because of the requirement for these speakers to store and differentiate lexical concepts in 2 languages to guide speech production and comprehension processes. In a whole brain comparison of bilingual speakers (n = 23) and monolingual speakers (n = 23), regressing out confounding factors, we find more extensive age-related decreases in GMV in the monolingual brain and significantly increased GMV in left temporal pole for bilingual speakers. Consistent with a specific neuroprotective effect of bilingualism, region of interest analyses showed a significant positive correlation between naming performance in the second language and GMV in this region. The effect appears to be bilateral though because there was a nonsignificantly different effect of naming performance on GMV in the right temporal pole. Our data emphasize the vulnerability of the temporal pole to normal aging and the value of bilingualism as both a general and specific protective factor to GMV decreases in healthy aging.

Anomia without dyslexia in Chinese

It is often assumed that oral reading of Chinese script proceeds from print to phonological output via semantic representations (e.g. Wang WS-Y. The Chinese language. Scientific American 1973; 228: 50-60). However, it is possible (at least in principle) that Chinese characters can be read aloud without access to the mappings between semantic representations and phonological output that are presumed to underlie normal spoken word production. We report the confrontation naming and oral reading performance of a Chinese anemic patient, YQS, whose word comprehension, word repetition and oral reading skills are intact. When her retrieval of names from pictures is compared with her retrieval of the same names from print, there is a highly significant advantage of oral reading over picture naming (P < 0.0001). Indeed, her oral reading of hundreds of Chinese characters is flawless. We argue that the data from YQS show that oral reading in Chinese does not require access to the mappings between semantic representations and phonological output, but instead can proceed via a non-semantic reading pathway that maps orthographic units, such as radicals and characters, directly onto phonological output.

Bilingualism provides a neural reserve for aging populations.

It has been postulated that bilingualism may act as a cognitive reserve and recent behavioral evidence shows that bilinguals are diagnosed with dementia about 4-5 years later compared to monolinguals. In the present study, we investigated the neural basis of these putative protective effects in a group of aging bilinguals as compared to a matched monolingual control group. For this purpose, participants completed the Erikson Flanker task and their performance was correlated to gray matter (GM) volume in order to investigate if cognitive performance predicts GM volume specifically in areas affected by aging. We performed an ex-Gaussian analysis on the resulting RTs and report that aging bilinguals performed better than aging monolinguals on the Flanker task. Bilingualism was overall associated with increased GM in the ACC. Likewise, aging induced effects upon performance correlated only for monolinguals to decreased gray matter in the DLPFC. Taken together, these neural regions might underlie the benefits of bilingualism and act as a neural reserve that protects against the cognitive decline that occurs during aging.

Pupil size changes during recognition memory

Pupils dilate to a greater extent when participants view old compared to new items during recognition memory tests. We report three experiments investigating the cognitive processes associated with this pupil old/new effect. Using a remember/know procedure, we found that the effect occurred for old items that were both remembered and known at recognition, although it was attenuated for known compared to remembered items. In Experiment 2, the pupil old/new effect was observed when items were presented acoustically, suggesting the effect does not depend on low-level visual processes. The pupil old/new effect was also greater for items encoded under deep compared to shallow orienting instructions, suggesting it may reflect the strength of the underlying memory trace. Finally, the pupil old/new effect was also found when participants falsely recognized items as being old. We propose that pupils respond to a strength-of-memory signal and suggest that pupillometry provides a useful technique for exploring the underlying mechanisms of recognition memory.