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The role of HG in the analysis of temporal iteration and interaural correlation
Reduced structural connectivity between left auditory thalamus and the motion-sensitive planum temporale in developmental dyslexia
Developmental dyslexia is characterized by the inability to acquire typical
reading and writing skills. Dyslexia has been frequently linked to cerebral
cortex alterations; however recent evidence also points towards sensory
thalamus dysfunctions: dyslexics showed reduced responses in the left auditory
thalamus (medial geniculate body, MGB) during speech processing in contrast to
neurotypical readers. In addition, in the visual modality, dyslexics have
reduced structural connectivity between the left visual thalamus (lateral
geniculate nucleus, LGN) and V5/MT, a cerebral cortex region involved in visual
movement processing. Higher LGN-V5/MT connectivity in dyslexics was associated
with the faster rapid naming of letters and numbers (RANln), a measure that is
highly correlated with reading proficiency. We here tested two hypotheses that
were directly derived from these previous findings. First, we tested the
hypothesis that dyslexics have reduced structural connectivity between the left
MGB and the auditory motion-sensitive part of the left planum temporale (mPT).
Second, we hypothesized that the amount of left mPT-MGB connectivity correlates
with dyslexics RANln scores. Using diffusion tensor imaging based probabilistic
tracking we show that male adults with developmental dyslexia have reduced
structural connectivity between the left MGB and the left mPT, confirming the
first hypothesis. Stronger left mPT-MGB connectivity was not associated with
faster RANnl scores in dyslexics, but in neurotypical readers. Our findings
provide first evidence that reduced cortico-thalamic connectivity in the
auditory modality is a feature of developmental dyslexia, and that it may also
impact on reading related cognitive abilities in neurotypical readers
Reading aloud boosts connectivity through the putamen
Functional neuroimaging and lesion studies have frequently reported thalamic and putamen activation during reading and speech production. However, it is currently unknown how activity in these structures interacts with that in other reading and speech production areas. This study investigates how reading aloud modulates the neuronal interactions between visual recognition and articulatory areas, when both the putamen and thalamus are explicitly included. Using dynamic causal modeling in skilled readers who were reading regularly spelled English words, we compared 27 possible pathways that might connect the ventral anterior occipito-temporal sulcus (aOT) to articulatory areas in the precentral cortex (PrC). We focused on whether the neuronal interactions within these pathways were increased by reading relative to picture naming and other visual and articulatory control conditions. The results provide strong evidence that reading boosts the aOT–PrC pathway via the putamen but not the thalamus. However, the putamen pathway was not exclusive because there was also evidence for another reading pathway that did not involve either the putamen or the thalamus. We conclude that the putamen plays a special role in reading but this is likely to vary with individual reading preferences and strategies
Who is that? Brain networks and mechanisms for identifying individuals
Social animals can identify conspecifics by many forms of sensory input. However, whether the neuronal computations that support this ability to identify individuals rely on modality-independent convergence or involve ongoing synergistic interactions along the multiple sensory streams remains controversial. Direct neuronal measurements at relevant brain sites could address such questions, but this requires better bridging the work in humans and animal models. Here, we overview recent studies in nonhuman primates on voice and face identity-sensitive pathways and evaluate the correspondences to relevant findings in humans. This synthesis provides insights into converging sensory streams in the primate anterior temporal lobe (ATL) for identity processing. Furthermore, we advance a model and suggest how alternative neuronal mechanisms could be tested
Curved Gabor Filters for Fingerprint Image Enhancement
Gabor filters play an important role in many application areas for the
enhancement of various types of images and the extraction of Gabor features.
For the purpose of enhancing curved structures in noisy images, we introduce
curved Gabor filters which locally adapt their shape to the direction of flow.
These curved Gabor filters enable the choice of filter parameters which
increase the smoothing power without creating artifacts in the enhanced image.
In this paper, curved Gabor filters are applied to the curved ridge and valley
structure of low-quality fingerprint images. First, we combine two orientation
field estimation methods in order to obtain a more robust estimation for very
noisy images. Next, curved regions are constructed by following the respective
local orientation and they are used for estimating the local ridge frequency.
Lastly, curved Gabor filters are defined based on curved regions and they are
applied for the enhancement of low-quality fingerprint images. Experimental
results on the FVC2004 databases show improvements of this approach in
comparison to state-of-the-art enhancement methods
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