Establishing a Developmentally Appropriate fMRI Paradigm Relevant to Presurgical Mapping of Memory in Children

Abstract

Functional magnetic resonance imaging (fMRI) is an established eloquent cortex mapping technique that is now an integral part of the pre-operative work-up in candidates for epilepsy surgery. Emerging evidence in adults with epilepsy suggests that material-specific fMRI paradigms can predict postoperative memory outcomes, however these paradigms are not suitable for children. In pediatric age, the use of memory fMRI paradigms designed for adults is complicated by the effect of developmental stages in cognitive maturation, the impairment experienced by some people with temporal lobe epilepsy (TLE) and the normal representation of memory function during development, which may differ from adults. We present a memory fMRI paradigm designed to activate mesial temporal lobe structures that is brief, independent of reading ability, and therefore a novel candidate for use in children. Data from 33 adults and 19 children (all healthy controls) show that the paradigm captures the expected leftward asymmetry of mesial temporal activation in adults. A more symmetrical pattern was observed in children, consistent with the progressive emergence of hemispheric specialisation across childhood. These data have important implications for the interpretation of presurgical memory fMRI in the pediatric setting. They also highlight the need to carefully consider the impact of cognitive development on fMRI tools used in clinical practice.

Concordance of verbal memory and language fMRI lateralization in people with epilepsy

“…32,33 Although there are clinical fMRI studies where tasks are specifically designed to engage verbal memory skills and activate memory-related anatomical regions for the assessment of verbal memory lateralization in presurgical patients with epilepsy, 26,[34][35][36][37][38] the dominant trend is to infer the verbal memory lateralization through language lateralization in tasks that involve a combination of word encoding (WE) and semantic decision-making. 24,25,29,[39][40][41][42][43] In terms of the anatomical regions used for quantification and subsequent assessment of functional laterality, several studies have focused on the activation of mesiotemporal structures. These studies demonstrated correlations between those presurgical activations and the emergence of postsurgical verbal memory deficits.…”

“…However, there is significant diversity among memory fMRI evaluation procedures at the level of task design, as well as at the level of anatomical fMRI signal activation 32,33 . Although there are clinical fMRI studies where tasks are specifically designed to engage verbal memory skills and activate memory‐related anatomical regions for the assessment of verbal memory lateralization in presurgical patients with epilepsy, 26,34–38 the dominant trend is to infer the verbal memory lateralization through language lateralization in tasks that involve a combination of word encoding (WE) and semantic decision‐making 24,25,29,39–43 . In terms of the anatomical regions used for quantification and subsequent assessment of functional laterality, several studies have focused on the activation of mesiotemporal structures.…”

Developing fMRI protocol for clinical use Comparison of 6 Arabic paradigms for brain language mapping in native Arabic speakers

“…Internationally, fMRI replaces the more invasive Wada test )also known as the intracarotid sodium amobarbital procedure( in lateralizing language and memory at some centers. 6,7 Language is a highly complex system that markedly varies across individuals. Patients native language affects brain activation responses during fMRI scans.…”