Gray Matter Predictors of Reading Disability

As described in a recent eNeuro manuscript, we examined the consistency of gray matter findings from published reading disability studies and then attempted to replicate those findings in a relatively large multi-site dataset. This study was part of a larger project to establish methods for multi-site studies.  Orbitofrontal and superior temporal sulcus gray matter volume was consistently lower in people with reading disability compared to controls across published studies and in the multi-site dataset. Results from the multi-site dataset were due to reading disability cases with relatively low total brain volume.  It appears then that the most consistent gray matter findings in the reading disability literature are driven by cases with low total gray matter volume. Interestingly, the orbitofrontal and superior sulcus gray matter effects were in locations where migrational errors were observed in post-mortem brains from people who had reading disability,; migrational errors that were most pronounced for a case with the lowest brain weight (Galaburda et al., 1985) . For those also interested in multi-site methods, please consider eNeuro manuscript as an example of how to deal with missing data across different research sites.

Bilateral Perisylivan Syndrome Case with a Dyslexia Profile

As part of our project to develop methods for multi-site studies, we unexpectedly received data collected from a child with Bilateral Perisylvian Syndrome (BPS).  This was unexpected for a dataset involving children with dyslexia because BPS often presents with epilepsy, mental retardation, and motor impairments.  This case did not exhibit these more severe phenotypes and instead had relatively specific deficits on measures of  phonological processing tasks compared to higher level language and cognitive abilities.  This observation is important because it shows that the BPS clinical profile can include  relatively mild impairments that includes reading disability.  Additional details about this case and BPS have been published in the journal Cortex. BPS

Neuromelanin contributes to locus coeruleus contrast in MRI scans

The locus coeruleus (LC) attention system is a target for understanding cognitive difficulties in children and older adults. Recent neuroimaging studies have suggested that LC can be structurally identified.  We now have direct evidence from an ex vivo imaging and histologic study that this contrast is impacted by the density of neuromelanin that normally accumulates in LC neurons with age (picture below: neuromelanin across histological sections corresponds to contrast in the MRI scan).  It is not clear that there is a direct correspondence between LC contrast, neuromelanin, and the number of healthy LC neurons, but the demonstration that neuromelanin contributes to LC contrast in MRI scans is a first step in  developing a biomarker that could be used to track disease and benefit from interventions.

LC_neuromelaninLC_neuromelanin

Cingulo-opercular Activity Provides Word Recognition Benefit

 

Recognizing speech in challenging listening conditions often produces increased activity in frontal cortex, particularly in cingulo-opercular regions, but the significance of this activity has been unclear.  This network of frontal cortex is thought to monitor performance and signal when cognitive resources are required to ensure successful performance.  Findings from earlier visuospatial studies indicated that cingulo-opercular activity can be predictive of performance on the next trial, so we investigated whether cingulo-opercular activity could also predict word recognition when words were presented in a multi-talker babble.  The results of our fMRI experiment demonstrated that elevated activity in cingulo-opercular cortex provided word recognition benefit on the following trial.  While elevated cingulo-opercular activity was not necessary for word recognition, up to 13% more words were recognized when activity was high compared to when it was low suggesting that elevated activity provided for optimal word recognition.  These results are important because they support the premise that cingulo-opercular activity can enhance ongoing task performance and does not only reflect difficulty or error.  They also suggest the intriguing possibility that we can enhance our performance on a variety of tasks and especially speech recognition by engaging cingulo-opercular cortex.  These findings have been published in the Journal of Neuroscience.