Powell, H. W. et al. Preoperative fMRI predicts memory decline following anterior temporal lobe resection. J. Neurol. Neurosurg. Psychiatry 79, 686-693

Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, UK.
Journal of neurology, neurosurgery, and psychiatry (Impact Factor: 6.81). 07/2008; 79(6):686-93. DOI: 10.1136/jnnp.2007.115139
Source: PubMed


Anterior temporal lobe resection (ATLR) benefits many patients with refractory temporal lobe epilepsy (TLE) but may be complicated by material specific memory impairments, typically of verbal memory following left ATLR, and non-verbal memory following right ATLR. Preoperative memory functional MRI (fMRI) may help in the prediction of these deficits.
To assess the value of preoperative fMRI in the prediction of material specific memory deficits following both left- and right-sided ATLR.
We report 15 patients with unilateral TLE undergoing ATLR; eight underwent dominant hemisphere ATLR and seven non-dominant ATLR. Patients performed an fMRI memory paradigm which examined the encoding of words, pictures and faces.
Individual patients with relatively greater ipsilateral compared with contralateral medial temporal lobe activation had greater memory decline following ATLR. This was the case for both verbal memory decline following dominant ATLR and for non-verbal memory decline following non-dominant ATLR. For verbal memory decline, activation within the dominant hippocampus was predictive of postoperative memory change whereas activation in the non-dominant hippocampus was not.
These findings suggest that preoperative memory fMRI may be a useful non-invasive predictor of postoperative memory change following ATLR and provide support for the functional adequacy theory of hippocampal function. They also suggest that fMRI may provide additional information, over that provided by neuropsychology, for use in the prediction of postoperative memory decline.

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Available from: Mark P Richardson, Feb 21, 2014
    • "The most parsimonious explanation for this hemispheric dissociation is that lateralized left temporal lobe damage is known to produce deficits in verbal learning and LTM (Milner 1971). Our finding of reduced list learning with reduced left thalamo-entorhinal FC is consistent with longitudinal observations showing that magnitudes of verbal LTM loss reflect extents of functional left MTL tissue damage (Powell et al. 2008). Conversely, imaging studies often reveal bilateral fronto-parietal activity during tasks involving STM, thought to reflect stimulus-independent complex processing demands (Nystrom et al. 2000; Wager and Smith 2003; Chein et al. 2011) within widely distributed circuits subserving working memory (Goldman-Rakic 1988). "
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    ABSTRACT: Short-term (STM) and long-term memory (LTM) have largely been considered as separate brain systems reflecting fronto-parietal and medial temporal lobe (MTL) functions, respectively. This functional dichotomy has been called into question by evidence of deficits on aspects of working memory in patients with MTL damage, suggesting a potentially direct hippocampal contribution to STM. As the hippocampus has direct anatomical connections with the thalamus, we tested the hypothesis that damage to thalamic nuclei regulating cortico-cortical interactions may contribute to STM deficits in patients with hippocampal dysfunction. We used diffusion-weighted magnetic resonance imaging-based tractography to identify anatomical subdivisions in patients with MTL epilepsy. From these, we measured resting-state functional connectivity with detailed cortical divisions of the frontal, temporal, and parietal lobes. Whereas thalamo-temporal functional connectivity reflected LTM performance, thalamo-prefrontal functional connectivity specifically predicted STM performance. Notably, patients with hippocampal volume loss showed thalamic volume loss, most prominent in the pulvinar region, not detected in patients with normal hippocampal volumes. Aberrant thalamo-cortical connectivity in the epileptic hemisphere was mirrored in a loss of behavioral association with STM performance specifically in patients with hippocampal atrophy. These findings identify thalamo-cortical disruption as a potential mechanism contributing to STM deficits in the context of MTL damage. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.
    Cerebral Cortex 05/2015; DOI:10.1093/cercor/bhv109 · 8.67 Impact Factor
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    • "This study is based on a modification of the study described previously [Powell et al., 2005]. We omitted the face encoding condition because of poor recognition memory for these stimuli in a previous study [Powell et al., 2005], and greatly divergent anatomical localisation of activity between studies (compare [Powell et al., 2008] with [Bonelli et al., 2010]). We note also recent evidence for poor reliability of BOLD activation for face stimuli [Plichta et al., 2012]. "
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    ABSTRACT: fMRI is increasingly implemented in the clinic to assess memory function. There are multiple approaches to memory fMRI, but limited data on advantages and reliability of different methods. Here, we compared effect size, activation lateralisation, and between-sessions reliability of seven memory fMRI protocols: Hometown Walking (block design), Scene encoding (block design and event-related design), Picture encoding (block and event-related), and Word encoding (block and event-related). All protocols were performed on three occasions in 16 patients with temporal lobe epilepsy (TLE). Group T-maps showed activity bilaterally in medial temporal lobe for all protocols. Using ANOVA, there was an interaction between hemisphere and seizure-onset lateralisation (P = 0.009) and between hemisphere, protocol and seizure-onset lateralisation (P = 0.002), showing that the distribution of memory-related activity between left and right temporal lobes differed between protocols and between patients with left-onset and right-onset seizures. Using voxelwise intraclass Correlation Coefficient, between-sessions reliability was best for Hometown and Scenes (block and event). The between-sessions spatial overlap of activated voxels was also greatest for Hometown and Scenes. Lateralisation of activity between hemispheres was most reliable for Scenes (block and event) and Words (event). Using receiver operating characteristic analysis to explore the ability of each fMRI protocol to classify patients as left-onset or right-onset TLE, only the Words (event) protocol achieved a significantly above-chance classification of patients at all three sessions. We conclude that Words (event) protocol shows the best combination of between-sessions reliability of the distribution of activity between hemispheres and reliable ability to distinguish between left-onset and right-onset patients. Hum Brain Mapp, 2015. © 2015 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.
    Human Brain Mapping 03/2015; 36(4). DOI:10.1002/hbm.22726 · 5.97 Impact Factor
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    • " EZ in or near the hippocampal region but distant from temporal language regions may modulate the later - alization of language representation ( Weber et al . , 2006 ; Hamberger et al . , 2007 ) . Compared with patients without HS , patients with HS are more likely to show atypical hemispheric lateralization of language ( Pataraia et al . , 2004 ; Powell et al . , 2008 ; Labudda et al . , 2010 ; Richard - son , 2010 ) and have better language functioning ( Chelune et al . , 1991 ; Hermann et al . , 1995 ; Davies et al . , 1998 ; Stroup et al . , 2003 ; Gleissner et al . , 2004 ; Baxendale et al . , 2006 ; Lineweaver et al . , 2006 ) . As suggested by Knecht ( 2004 ) , the hippocampus may be crucial to"
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    ABSTRACT: The objective of this review is to resume major neuroimaging findings on language organization and plasticity in patients with focal and refractory epilepsy, to discuss the effect of modulatory variables that should be considered alongside patterns of reorganization, and to propose possible models of language reorganization. The focal and refractory epilepsy provides a real opportunity to investigate various types of language reorganization in different conditions. The ‘ chronic’ condition (induced by the epileptogenic zone or EZ) is associated with either recruitment of homologous regions of the opposite hemisphere or recruitment of intrahemispheric, nonlinguistic regions. In the ‘ acute ’ condition (neurosurgery and EZ resection), the initial interhemispheric shift (induced by the chronic EZ) could follow a reverse direction, back to the initial hemisphere. These different patterns depend on several modulatory factors and are associated with various levels of language performance. As a neuroimaging tool, functional magnetic resonance imaging enables the detailed investigation of both hemispheres simultaneously and allows for comparison with healthy controls, potentially creating a more comprehensive and more realistic picture of brain-language relations. Importantly, functional neuroimaging approaches demonstrate a good degree of concordance on a theoretical level, but also a considerable degree of individual variability, attesting to the clinical importance with these methods to establish, empirically, language localization in individual patients. Overall, the unique features of epilepsy, combined with ongoing advances in technology, promise further improvement in understanding of language substrate.
    Reviews in the neurosciences 02/2015; 26(1):1-19. DOI:10.1515/revneuro-2014-0074 · 3.33 Impact Factor
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