Najat Saddiki1, Sophie Hennion2, Romain Viard1, Nassima Ramdane3, Renaud Lopes1, Marc Baroncini4, William Szurhaj2, Nicolas Reyns4, Jean Pierre Pruvo1, Christine Delmaire5. 1. Inserm U1171, Department of Neuroradiology, Hospital Roger-Salengro, University Medical Centre, Degenerative & Vascular Cognitive Disorders, 59000 Lille, France. 2. Department of Neurophysiology, Hospital Roger-Salengro, University Medical Centre, Inserm U1171, 59000 Lille, France. 3. Department of Biostatistical Methodology and Data Management, Maison Régionale de la Recherche Clinique, University Medical Centre, 59000 Lille, France. 4. Department of Neurosurgery, Hospital Roger-Salengro, University Medical Centre, 59000 Lille, France. 5. Inserm U1171, Department of Neuroradiology, Hospital Roger-Salengro, University Medical Centre, Degenerative & Vascular Cognitive Disorders, 59000 Lille, France. Electronic address: christine.delmaire@chru-lille.fr.
Abstract
PURPOSE: Medial lobe temporal structures and more specifically the hippocampus play a decisive role in episodic memory. Most of the memory functional magnetic resonance imaging (fMRI) studies evaluate the encoding phase; the retrieval phase being performed outside the MRI. We aimed to determine the ability to reveal greater hippocampal fMRI activations during retrieval phase. MATERIALS AND METHODS: Thirty-five epileptic patients underwent a two-step memory fMRI. During encoding phase, subjects were requested to identify the feminine or masculine gender of faces and words presented, in order to encourage stimulus encoding. One hour after, during retrieval phase, subjects had to recognize the word and face. We used an event-related design to identify hippocampal activations. RESULTS: There was no significant difference between patients with left temporal lobe epilepsy, patients with right temporal lobe epilepsy and patients with extratemporal lobe epilepsy on verbal and visual learning task. For words, patients demonstrated significantly more bilateral hippocampal activation for retrieval task than encoding task and when the tasks were associated than during encoding alone. Significant difference was seen between face-encoding alone and face retrieval alone. CONCLUSIONS: This study demonstrates the essential contribution of the retrieval task during a fMRI memory task but the number of patients with hippocampal activations was greater when the two tasks were taken into account.
PURPOSE: Medial lobe temporal structures and more specifically the hippocampus play a decisive role in episodic memory. Most of the memory functional magnetic resonance imaging (fMRI) studies evaluate the encoding phase; the retrieval phase being performed outside the MRI. We aimed to determine the ability to reveal greater hippocampal fMRI activations during retrieval phase. MATERIALS AND METHODS: Thirty-five epilepticpatients underwent a two-step memory fMRI. During encoding phase, subjects were requested to identify the feminine or masculine gender of faces and words presented, in order to encourage stimulus encoding. One hour after, during retrieval phase, subjects had to recognize the word and face. We used an event-related design to identify hippocampal activations. RESULTS: There was no significant difference between patients with left temporal lobe epilepsy, patients with right temporal lobe epilepsy and patients with extratemporal lobe epilepsy on verbal and visual learning task. For words, patients demonstrated significantly more bilateral hippocampal activation for retrieval task than encoding task and when the tasks were associated than during encoding alone. Significant difference was seen between face-encoding alone and face retrieval alone. CONCLUSIONS: This study demonstrates the essential contribution of the retrieval task during a fMRI memory task but the number of patients with hippocampal activations was greater when the two tasks were taken into account.