Brianna M. Paul

Cognitive development following early brain injury: evidence for neural adaptation.

Over the past few decades a large body of work from developmental neurobiology has shown that mammalian brain development is the product of dynamic and adaptive processes operating within highly constrained, but continually changing, biological and environmental contexts. The recent study of children with prenatal focal brain injury supports this dynamic view of development for humans. Childrens injuries often affect substantial portions of one cerebral hemisphere, resulting in damage that would compromise cognitive ability in adults. However, longitudinal behavioral studies of this population have revealed only mild deficits. It is suggested here that childrens capacity for adaptation reflects normal developmental processes operating against a backdrop of serious neural perturbation. Data from three behavioral domains--linguistics, spatial cognition and affective development--illustrate this complex profile of change.

Face and place processing in Williams syndrome: evidence for a dorsal-ventral dissociation

Individuals with Williams syndrome (WMS) show an interesting dissociation of ability within the visuospatial domain, particularly between face perception and other visuospatial tasks. In this population, using tasks matched for stimuli, required response, and difficulty (for controls) is critical when comparing performance across these areas. We compared WMS individuals with a sample of typically developing 8- and 9-year-old children, and with a sample of adults, closer to the WMS participants in chronological age, in order to investigate performance across two precisely matched perceptual tasks, one assessing face processing and the other assessing proficiency in processing stimuli location. The pattern of performance seen in WMS, but not in controls, implicates a specific deficit of dorsal stream functioning in this syndrome.

Amygdala response to faces parallels social behavior in Williams syndrome

Individuals with Williams syndrome (WS), a genetically determined disorder, show relatively strong face-processing abilities despite poor visuospatial skills and depressed intellectual function. Interestingly, beginning early in childhood they also show an unusually high level of interest in face-to-face social interaction. We employed functional magnetic resonance imaging (fMRI) to investigate physiological responses in face-sensitive brain regions, including ventral occipito-temporal cortex and the amygdala, in this unique genetic disorder. Participants included 17 individuals with WS, 17 age- and gender-matched healthy adults (chronological age-matched controls, CA) and 17 typically developing 8- to 9-year-old children (developmental age controls, DA). While engaged in a face discrimination task, WS participants failed to recruit the amygdala, unlike both CA and DA controls. WS fMRI responses in ventral occipito-temporal cortex, however, were comparable to those of DA controls. Given the integral role of the amygdala in social behavior, the failure of WS participants to recruit this region during face processing may be a neural correlate of the abnormally high sociability that characterizes this disorder.

What does diffusion tensor imaging (DTI) tell us about cognitive networks in temporal lobe epilepsy

Diffusion tensor imaging (DTI) has provided considerable insight into our understanding of epilepsy as a network disorder, revealing subtle alterations in white matter microstructure both proximal and distal to the epileptic focus. These white matter changes have been shown to assist with lateralizing the seizure focus, as well as delineating the location/anatomy of key white matter tracts (i.e., optic radiations) for surgical planning. However, only recently have studies emerged describing the utility of DTI for probing cognitive networks in patients with epilepsy and for examining the structural plasticity within these networks both before and after epilepsy surgery. Here, we review the current literature describing the use of DTI for understanding language and memory networks in patients with temporal lobe epilepsy (TLE), as well as the extant literature on networks associated with executive functioning and global intelligence. Studies of memory and language reveal a complex network of frontotemporal fibers that contribute to naming and fluency performance in TLE, and demonstrate that these networks appear to undergo adaptive changes in response to surgical intervention. Although studies of executive functioning and global intelligence have been less conclusive, there is accumulating evidence that aberrant communication between frontoparietal and medial temporal networks may underlie working memory impairment in TLE. More recently, multimodal imaging studies have provided evidence that disruptions within these white matter networks co-localize with functional changes observed on functional MRI. However, structure-function associations are not entirely coherent and may breakdown in patients with TLE, especially those with a left-sided seizure focus. Although the reasons for discordant findings are unclear, small sample sizes, heterogeneity within patient populations and limitations of the current tensor model may account for contradictory and null findings. Improvements in imaging hardware and higher field strengths have now paved the way for the implementation of advanced diffusion techniques, and these advanced models show great promise for improving our understanding of how network dysfunction contributes to cognitive morbidity in TLE.

Restriction spectrum imaging reveals decreased neurite density in patients with temporal lobe epilepsy

Diffusion tensor imaging (DTI) has become a popular tool for delineating the location and extent of white matter injury in temporal lobe epilepsy (TLE). However, DTI yields nonspecific measures that are confounded by changes occurring within both the intracellular and extracellular environments. This study investigated whether an advanced diffusion method, restriction spectrum imaging (RSI) could provide a more robust measure of white matter injury in TLE relative to DTI due to RSIs ability to separate intraaxonal diffusion (i.e., neurite density; ND) from diffusion associated with extraaxonal factors (e.g., inflammation; crossing fibers).

Neuroimaging correlates of language network impairment and reorganization in temporal lobe epilepsy

Advanced, noninvasive imaging has revolutionized our understanding of language networks in the brain and is reshaping our approach to the presurgical evaluation of patients with epilepsy. Functional magnetic resonance imaging (fMRI) has had the greatest impact, unveiling the complexity of language organization and reorganization in patients with epilepsy both pre- and postoperatively, while volumetric MRI and diffusion tensor imaging have led to a greater appreciation of structural and microstructural correlates of language dysfunction in different epilepsy syndromes. In this article, we review recent literature describing how unimodal and multimodal imaging has advanced our knowledge of language networks and their plasticity in epilepsy, with a focus on the most frequently studied epilepsy syndrome in adults, temporal lobe epilepsy (TLE). We also describe how new analytic techniques (i.e., graph theory) are leading to a refined characterization of abnormal brain connectivity, and how subject-specific imaging profiles combined with clinical data may enhance the prediction of both seizure and language outcomes following surgical interventions.

Does bilingualism increase brain or cognitive reserve in patients with temporal lobe epilepsy

Bilingual healthy adults have been shown to exhibit an advantage in executive functioning (EF) that is associated with microstructural changes in white matter (WM) networks. Patients with temporal lobe epilepsy (TLE) often show EF deficits that are associated with WM compromise. In this study, we investigate whether bilingualism can increase cognitive reserve and/or brain reserve in bilingual patients with TLE, mitigating EF impairment and WM compromise.

Multimodal imaging of language reorganization in patients with left temporal lobe epilepsy

HighlightsMultimodal imaging can help to localize language networks in LTLE.Interhemispheric language reorganization is associated with alternations to the ARC.Structural and functional shifts mitigate language impairment in LTLE. ABSTRACT This study explored the relationships among multimodal imaging, clinical features, and language impairment in patients with left temporal lobe epilepsy (LTLE). Fourteen patients with LTLE and 26 controls underwent structural MRI, functional MRI, diffusion tensor imaging, and neuropsychological language tasks. Laterality indices were calculated for each imaging modality and a principal component (PC) was derived from language measures. Correlations were performed among imaging measures, as well as to the language PC. In controls, better language performance was associated with stronger left‐lateralized temporo‐parietal and temporo‐occipital activations. In LTLE, better language performance was associated with stronger right‐lateralized inferior frontal, temporo‐parietal, and temporo‐occipital activations. These right‐lateralized activations in LTLE were associated with right‐lateralized arcuate fasciculus fractional anisotropy. These data suggest that interhemispheric language reorganization in LTLE is associated with alterations to perisylvian white matter. These concurrent structural and functional shifts from left to right may help to mitigate language impairment in LTLE.

Clinical Reasoning: Seizures from the neglected lobe

An 11-year-old, right-handed girl with normal development, no significant medical history, and no known epilepsy risk factors presented to the clinic for evaluation of new-onset epilepsy.