The neural basis of surface dyslexia in semantic dementia.

Semantic dementia (SD) is a neurodegenerative disease characterized by atrophy of anterior temporal regions and progressive loss of semantic memory. SD patients often present with surface dyslexia, a relatively selective impairment in reading low-frequency words with exceptional or atypical spelling-to-sound correspondences. Exception words are typically 'over-regularized' in SD and pronounced as they are spelled (e.g. 'sew' is pronounced as 'sue'). This suggests that in the absence of sufficient item-specific knowledge, exception words are read by relying mainly on subword processes for regular mapping of orthography to phonology. In this study, we investigated the functional anatomy of surface dyslexia in SD using functional magnetic resonance imaging (fMRI) and studied its relationship to structural damage with voxel-based morphometry (VBM). Five SD patients and nine healthy age-matched controls were scanned while they read regular words, exception words and pseudowords in an event-related design. Vocal responses were recorded and revealed that all patients were impaired in reading low-frequency exception words, and made frequent over-regularization errors. Consistent with prior studies, fMRI data revealed that both groups activated a similar basic network of bilateral occipital, motor and premotor regions for reading single words. VBM showed that these regions were not significantly atrophied in SD. In control subjects, a region in the left intraparietal sulcus was activated for reading pseudowords and low-frequency regular words but not exception words, suggesting a role for this area in subword mapping from orthographic to phonological representations. In SD patients only, this inferior parietal region, which was not atrophied, was also activated by reading low-frequency exception words, especially on trials where over-regularization errors occurred. These results suggest that the left intraparietal sulcus is involved in subword reading processes that are differentially recruited in SD when word-specific information is lost. This loss is likely related to degeneration of the anterior temporal lobe, which was severely atrophied in SD. Consistent with this, left mid-fusiform and superior temporal regions that showed reading-related activations in controls were not activated in SD. Taken together, these results suggest that the left inferior parietal region subserves subword orthographic-to-phonological processes that are recruited for exception word reading when retrieval of exceptional, item-specific word forms is impaired by degeneration of the anterior temporal lobe.

Anatomical correlates of sentence comprehension and verbal working memory in neurodegenerative disease.

This study investigates whether sentence comprehension and nonsyntactic verbal working memory (vWM) are sustained by the same or by different neural systems. Scores in a sentence-picture matching task and in digits backward (DB) were correlated with magnetic resonance imaging voxelwise gray matter volumes using voxel-based morphometry in 58 patients with neurodegenerative diseases. Results showed that overall sentence comprehension scores, regardless of grammatical structure, correlated with gray matter volumes in the left temporoparietal region, whereas DB scores correlated with dorsolateral prefrontal and inferior parietal volumes. Comprehension of multiclausal relative sentences (type 3) significantly correlated with voxels in the dorsal portion of the left inferior and middle frontal gyri. When DB and multiclausal relative sentences were directly compared, they showed overlapping neural substrates in the dorsolateral left frontal region, supporting a single source of vWM for syntactic and nonsyntactic tasks. Within this large area of common involvement, a small portion of pars triangularis showed an independent effect of multiclausal sentences, whereas a region in the middle frontal gyrus showed greater correlation with DB. This study reconciles two opposing views, which hold that sentence comprehension and vWM rely on either the same or different anatomical resources.

Twelve tips for effective international clinical placements.

As universities adopt an increasingly international focus, student health professionals are keen to gain clinical experiences in other countries. Such clinical placements provide students with the opportunity to share their knowledge and at the same time acquire new clinical and cultural skills. The experience gained will not only enhance their clinical practice overseas, but will also enhance it in their home country where they are likely to work with people from culturally, linguistically and clinically diverse backgrounds. Careful preparation and adequate supports are critical if students and the host institutions are to gain maximum benefit from cross-cultural clinical placements. The tips below are based on an ongoing collaboration between the Indian Institute of Cerebral Palsy, Kolkata, India and The University of Sydney, as well as recommendations from the burgeoning literature on international clinical placements. The authors are from both the sending and the receiving institutions, and have found that close collaboration between the home and host institutions along with student reflection, evaluation and the opportunity to integrate new knowledge with other clinical experiences are keys to a satisfactory outcome for all concerned.

Key principles underlying research and practice in AAC.

Six principles of AAC research and practice are offered for consideration and discussion within the AAC community. Principle 1 requires the active participation of individuals with complex communication needs (CCN) in all AAC activities. Principle 2 seeks to ensure that theoretical constructs underlying research and development in AAC are grounded, widely accepted, and clearly defined. Principle 3 underscores the need to use ergonomics in the design and development of AAC technologies and instructional strategies. Principle 4 highlights communication partners and the unique roles they play in AAC. Principle 5 accentuates the need to focus on societal roles, relationships, and opportunities made possible by AAC technologies and services. Finally, principle 6 draws attention to the importance of measuring a broad range of AAC outcomes, especially those most significant to primary AAC stakeholders.

Exploring the elements of narrative that emerge in the interactions between an 8-year-old child who uses an AAC device and her teacher.

Narrative abilities have been identified as a link to successful school achievement and, in particular, to the acquisition of literacy. Children who use AAC may be at risk of impaired narrative facility due to the differences in their language learning experiences, limitation of their AAC systems, and limitations from constrained access to physical and social environments. In this study, the elements of narrative that emerged in the interactions between an 8-year-old child who used an AAC device and her teacher are described. This assessment was achieved through use of the Narrative Assessment Profile (Bliss, McCabe, & Miranda, 1998) in the context of five tasks designed to elicit a spectrum of narrative features. Results indicate that the interactions between the child and her teacher made it difficult to assess whether or not the child had control of certain features of narrative. From a purely structural analysis, most narrative discourse dimensions appeared to be severely compromised and therefore in need of immediate intervention. Discussion includes aspects of narrative intervention and suggested topics for further research.

Lesion analysis of the brain areas involved in language comprehension.

The cortical regions of the brain traditionally associated with the comprehension of language are Wernicke's area and Broca's area. However, recent evidence suggests that other brain regions might also be involved in this complex process. This paper describes the opportunity to evaluate a large number of brain-injured patients to determine which lesioned brain areas might affect language comprehension. Sixty-four chronic left hemisphere stroke patients were evaluated on 11 subtests of the Curtiss-Yamada Comprehensive Language Evaluation - Receptive (CYCLE-R; Curtiss, S., & Yamada, J. (1988). Curtiss-Yamada Comprehensive Language Evaluation. Unpublished test, UCLA). Eight right hemisphere stroke patients and 15 neurologically normal older controls also participated. Patients were required to select a single line drawing from an array of three or four choices that best depicted the content of an auditorily-presented sentence. Patients' lesions obtained from structural neuroimaging were reconstructed onto templates and entered into a voxel-based lesion-symptom mapping (VLSM; Bates, E., Wilson, S., Saygin, A. P., Dick, F., Sereno, M., Knight, R. T., & Dronkers, N. F. (2003). Voxel-based lesion-symptom mapping. Nature Neuroscience, 6(5), 448-450.) analysis along with the behavioral data. VLSM is a brain-behavior mapping technique that evaluates the relationships between areas of injury and behavioral performance in all patients on a voxel-by-voxel basis, similar to the analysis of functional neuroimaging data. Results indicated that lesions to five left hemisphere brain regions affected performance on the CYCLE-R, including the posterior middle temporal gyrus and underlying white matter, the anterior superior temporal gyrus, the superior temporal sulcus and angular gyrus, mid-frontal cortex in Brodmann's area 46, and Brodmann's area 47 of the inferior frontal gyrus. Lesions to Broca's and Wernicke's areas were not found to significantly alter language comprehension on this particular measure. Further analysis suggested that the middle temporal gyrus may be more important for comprehension at the word level, while the other regions may play a greater role at the level of the sentence. These results are consistent with those seen in recent functional neuroimaging studies and offer complementary data in the effort to understand the brain areas underlying language comprehension.

Is it bigger than a breadbox? Performance of patients with prefrontal lesions on a new executive function test.

Executive deficits of problem solving and concept formation have been associated with frontal lobe dysfunction. Here we describe a new clinical test of concept formation based on the parlor game, Twenty Questions. The Twenty Questions Test requires examinees to ask the fewest number of yes/no questions possible in order to identify a target item from an array of 30 line drawings. The items belong to a number of categories and subcategories that exist in a hierarchical, semantic structure. Patients with focal prefrontal lesions asked significantly more questions than controls in their attempt to guess the target items and sometimes exhausted the 20-question limit. Qualitative analyses revealed that patients tended to use ineffective categorization strategies, for example, relying exclusively on questions that referred to single items. Taken together with previous findings, we conclude that prefrontal cortex supports the on-line organization and conceptualization of category exemplars in concept-formation tasks.

Role of the precentral gyrus of the insula in complex articulation.

Previous research has suggested that the left anterior insula, specifically the superior precentral gyrus of the insula (SPGI), is a critical brain region for the coordination of complex articulatory movements. However, previous studies have not determined which articulatory factors are specifically dependent on this brain region. In the current study, 33 left hemisphere stroke patients with varying degrees of speech impairment were asked to perform multiple repetitions of single words that varied along three separate dimensions: number of syllables, degree of articulatory travel (i.e., change between places of articulation for consonants), and presence/absence of an initial consonant cluster. The role of the SPGI in performance across the three conditions was determined using voxel-based lesion symptom mapping (VLSM), a statistical approach to lesion analysis that does not require separating patients based on lesion site or symptom profile. Rather, continuous performance data are entered, along with lesions reconstructed in normalized space. Based on preliminary analyses, there was adequate power to detect differences in the SPGI, which was the focus of our predictions. We found that the SPGI was critical for performance on the articulation task across all three conditions, namely, when words were multi-syllabic, required a high degree of travel, or involved an initial consonant cluster. As a control, we also generated a VLSM map for articulation of words with minimal articulatory complexity (i.e., single-syllable words with no initial cluster and a minimal change in place of articulation). In this case, the SPGI was not implicated. The current results suggest that the left SPGI is a critical area for intra- and inter-syllabic coordination of complex articulatory movements, prior to end-stage execution of speech commands.