Visual word form processing deficits driven by severity of reading impairments in children with developmental dyslexia.

The visual word form area (VWFA) in the left ventral occipito-temporal (vOT) cortex is key to fluent reading in children and adults. Diminished VWFA activation during print processing tasks is a common finding in subjects with severe reading problems. Here, we report fMRI data from a multicentre study with 140 children in primary school (7.9-12.2 years; 55 children with dyslexia, 73 typical readers, 12 intermediate readers). All performed a semantic task on visually presented words and a matched control task on symbol strings. With this large group of children, including the entire spectrum from severely impaired to highly fluent readers, we aimed to clarify the association of reading fluency and left vOT activation during visual word processing. The results of this study confirm reduced word-sensitive activation within the left vOT in children with dyslexia. Interestingly, the association of reading skills and left vOT activation was especially strong and spatially extended in children with dyslexia. Thus, deficits in basic visual word form processing increase with the severity of reading disability but seem only weakly associated with fluency within the typical reading range suggesting a linear dependence of reading scores with VFWA activation only in the poorest readers.

Multimodal transcranial magnetic stimulation: using concurrent neuroimaging to reveal the neural network dynamics of noninvasive brain stimulation.

Since its introduction in the 1980s, Transcranial Magnetic Stimulation (TMS) has proven to be a versatile method to non-invasively study human brain function by reversibly altering ongoing neural processing. In addition, TMS has been explored as a therapeutic intervention in a number of neurological and neuropsychiatric conditions. However, our understanding of TMS-induced changes in neural activity patterns is still rather limited, particularly when it comes to changes in neural network dynamics beyond the cortical site directly targeted by TMS. In order to monitor both its local and remote neurophysiological effects, TMS has been combined with complementary neuroimaging methods that allow additional insights into how observed TMS effects at the behavioral level can be interpreted by taking into account the full scale of its impact throughout the brain. The current review provides a comprehensive overview of the existing multimodal TMS literature, covering studies in which TMS was combined with one of the three main neuroimaging modalities, namely Electroencephalography, Positron Emission Tomography, and functional Magnetic Resonance Imaging. Besides constituting a reflection of the status quo in this exciting multidisciplinary research field, this review additionally reveals both convergent and divergent observations across modalities that await corroboration or resolution, thereby further guiding ongoing basic research and providing useful constraints to optimize future clinical applications.

Verbal fluency in Parkinson's disease: results of a 2-min fluency test.

BACKGROUND: Patients suffering from Parkinson's disease (PD) are often reported to have an impaired performance on tests measuring executive functioning, such as fluency tasks. AIM: To investigate whether verbal fluency is impaired in PD patients (n = 25) compared with healthy controls (n = 15) using a 2-min semantic and phonemic verbal fluency test. A 2-min version of the fluency task was used to allow for more switches between clusters to study retrieval strategies more adequately. RESULTS: No differences in performance on both semantic and phonemic fluency tasks between the PD patients and the control persons were found. Moreover, both groups appeared to use the same retrieval strategies. CONCLUSION: Patients suffering from PD appear to use the same strategies for producing words as healthy controls do. Different pathways may be involved in switching clusters during the fluency task than in other types of switching that may be impaired in PD, such as motor switching and concept-shifting.