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SummaryObjective We investigated reading skills in individuals who have undergone left cerebral hemispherectomy and in readers with developmental dyslexia to understand diverse characteristics contributing to reading difficulty. Although dyslexia is a developmental disorder, left hemispherectomy requires that patients (re)establish the language process needed to perform the language-based tasks in the nondominant (right) hemisphere to become readers. Methods Participants with developmental dyslexia (DD; n = 11) and participants who had undergone left hemispherectomy (HEMI; n = 11) were matched on age and gender, and were compared on timed and untimed measures of single word and pseudo-word reading. The hemispherectomy group was subdivided into prenatal (in utero) and postnatal (>3 years) insult groups, indicating the timing of the primary lesion that ultimately required surgical intervention. Results On an untimed reading measure, the readers with DD were comparable to individuals who had undergone left hemispherectomy due to prenatal insult, but both scored higher than the postnatal hemispherectomy group. Timed word reading differed across groups. The hemispherectomy prenatal subgroup had low average scores on both timed and untimed tests. The group with dyslexia had average scores on untimed measures and below average scores on timed reading. The hemispherectomy postnatal group had the lowest scores among the groups by a significant margin, and the most pronounced reading difficulty. Significance Patients with prenatal lesions leading to an isolated right hemisphere (RH) have the potential to develop reading to a degree comparable to that in persons with dyslexia for single word reading. This potential sharply diminishes in individuals who undergo hemispherectomy due to postnatal insult. The higher scores of the prenatal hemispherectomy group on timed reading suggest that under these conditions, individuals with an isolated RH can compensate to a significant degree.

Objective Many forms of epilepsy are associated with aberrant neuronal connections, but the relationship between such pathological connectivity and the underlying physiological predisposition to seizures is unclear. We sought to characterize the cortical excitability profile of a developmental form of epilepsy known to have structural and functional connectivity abnormalities. Methods We employed transcranial magnetic stimulation (TMS) with simultaneous electroencephalographic (EEG) recording in 8 patients with epilepsy from periventricular nodular heterotopia and matched healthy controls. We used connectivity imaging findings to guide TMS targeting and compared the evoked responses to single-pulse stimulation from different cortical regions. Results Heterotopia patients with active epilepsy demonstrated a relatively augmented late cortical response that was greater than that of matched controls. This abnormality was specific to cortical regions with connectivity to subcortical heterotopic gray matter. Topographic mapping of the late response differences showed distributed cortical networks that were not limited to the stimulation site, and source analysis in 1 subject revealed that the generator of abnormal TMS-evoked activity overlapped with the spike and seizure onset zone. Interpretation Our findings indicate that patients with epilepsy from gray matter heterotopia have altered cortical physiology consistent with hyperexcitability, and that this abnormality is specifically linked to the presence of aberrant connectivity. These results support the idea that TMS-EEG could be a useful biomarker in epilepsy in gray matter heterotopia, expand our understanding of circuit mechanisms of epileptogenesis, and have potential implications for therapeutic neuromodulation in similar epileptic conditions associated with deep lesions. Ann Neurol 2015;77:487–503

Summary Purpose: Periventricular nodular heterotopia (PNH) is a malformation of cortical development associated with epilepsy and dyslexia. Evidence suggests that heterotopic gray matter can be functional in brain malformations and that connectivity abnormalities may be important in these disorders. We hypothesized that nodular heterotopia develop abnormal connections and systematically investigated the structural and functional connectivity of heterotopia in patients with PNH. Methods: Eleven patients were studied using diffusion tensor tractography and resting-state functional connectivity MRI with bold oxygenation level–dependent (BOLD) imaging. Fiber tracks with a terminus within heterotopic nodules were visualized to determine structural connectivity, and brain regions demonstrating resting-state functional correlations to heterotopic nodules were analyzed. Relationships between these connectivity results and measures of clinical epilepsy and cognitive disability were examined. Key Findings: A majority of heterotopia (69%) showed structural connectivity to discrete regions of overlying cortex, and almost all (96%) showed functional connectivity to these regions (mean peak correlation coefficient 0.61). Heterotopia also demonstrated connectivity to regions of contralateral cortex, other heterotopic nodules, ipsilateral but nonoverlying cortex, and deep gray matter structures or the cerebellum. Patients with the longest durations of epilepsy had a higher degree of abnormal functional connectivity (p = 0.036). Significance: Most heterotopic nodules in PNH are structurally and functionally connected to overlying cortex, and the strength of abnormal connectivity is higher among patients with the longest duration of epilepsy. Along with prior evidence that cortico-cortical tract defects underlie dyslexia in this disorder, the current findings suggest that altered connectivity is likely a critical substrate for neurologic dysfunction in brain malformations.

The term brain based is often used to describe learning theories, principles, and products. Although there have been calls urging educators to be cautious in interpreting and using such material, consumers may find it challenging to understand the role of the brain and to discriminate among brain based products to determine which would be suitable for specific educational goals. We offer a framework for differentiating the multiple meanings of the brain based label and guidelines for educators and consumers to use when evaluating educational products labeled as brain based. The guidelines include: identifying educational goals and target student populations, aligning goals and product purposes, reviewing product merits, identifying benefits and limitations of the product, and characterizing the product's impact on behavioral performance.

—The theme of Usable Knowledge in Mind, Brain, and Education will be a special section that will appear regularly in the journal. The section will focus on the synergistic connections between biology, cognitive science, and human development on the one hand and educational thought, policy, and practice on the other. Efforts to create usable knowledge in mind, brain, and education focus on questions that relate research and theory to educational practice, involving pedagogy and learning, discussions of how best to conduct ethical and valid research that crosses disciplinary boundaries, and consideration of how to use such research to promote responsible policy.