Abstracts

Lateralizing memory function using fMRI has presented a challenge due to difficulty developing tasks that produce activation in the mesial temporal lobes (MTL). The present study investigated the use of an event-related novelty detection fMRI paradigm using faces of babies as stimuli to capitalize on both the hippocampal response to novelty and the amygdalohippocampal response to emotionally meaningful stimuli. This task has demonstrated MTL activation in healthy controls (Baxter et al., 2004) and sensitivity to hippocampal dysfunction in dementia patients, but its ability to produce activation in the MTL among epilepsy patients has not previously been examined., Sixteen patients undergoing presurgical work-up for epilepsy completed the fMRI task in a 3T GE scanner (Mean Age=33.4 years (10.11); M:F=10:6; 14 right handed; all L hemisphere language dominant per IAT results). After being presented with pictures of 5 baby faces repeatedly for 4 minutes and a 20-minute delay for consolidation, the overlearned familiar faces were presented intermixed with novel baby faces and participants responded whether each face was [ldquo]old[rdquo] or [ldquo]new.[rdquo] Activation during the novel faces was contrasted to the familiar faces (N [gt] F) using SPM2 in a whole-brain analysis. Significant activation was defined as p [lt] .01, (uncorrected) [gt] 50 voxel cluster. The laterality of the participants[apos] MTL activation during the discrimination task was then compared to the findings of their other preoperative studies (i.e., IAT memory testing, neuropsychological memory performance, scalp EEG findings, structural MRI)., Most participants demonstrated MTL activation during the N [gt] F condition. Activation was weak in 4 cases (p = .05). Ten participants demonstrated a lateralized pattern of activation (7 R[gt]L [amp] 2 L[gt]R). There was little concordance between the fMRI laterality pattern and participants[apos] IAT memory asymmetries (4/10) or pattern of neuropsychological memory performance (2/10). Their pattern of activation was highly congruent with their MRI and EEG results. Of the 10 with MTL abnormalities on structural MRI, 8 demonstrated greater activation in the contralesional MTL during the fMRI memory task. Nine of the 10 participants with a lateralized fMRI pattern demonstrated greater activation in the MTL contralateral to the site of their seizure focus as determined by EEG; the one exception had a nonlateralizing EEG., The findings suggest that this fMRI task has promise for assessing MTL reactivity among epilepsy patients, but further investigation is required to better understand the implications of a lateralized pattern of activation. Ultimately, it is the ability of such a task to provide meaningful data regarding patients[apos] postoperative memory outcome that is clinically most important. Further research is needed to examine its predictive value., (Supported by Barrow Neurological Foundation.)