title: Stimulus pacing affects the activation of the medial temporal lobe during a semantic classification task: an fMRI study.
abstract: Our purpose was to explore the influence of stimulus pacing in blocked functional MRI studies on the activation pattern elicited by a semantic retrieval task. Twenty-two participants performed both a fixed-paced and a self-paced functional MR imaging experiment in which a semantic categorization (animal/object) task was contrasted with a perceptual (small/capital letter string) categorization task. Group and single-subject ROI analyses were computed. In both the fixed-paced and self-paced experiments, semantic categorization contrasted with perceptual categorization elicited a cerebral network generally accepted to be involved in semantic processing comprising left inferior prefrontal, left lateral temporal, paracingular and right cerebellar areas. Our main finding was that the self-paced stimulus modality additionally yielded significant activation in the medial temporal lobe (MTL) structures including the hippocampus and the parahippocampal gyrus. More elaborative single-subject ROI analyses revealed MTL activation in 86% of the subjects for the self-paced design, but only in 21% of subjects for the fixed-paced design. The discussion focuses on possible explanations for this finding. We conclude that a self-paced as opposed to a fixed-paced semantic retrieval paradigm is able to detect significant MTL activation in groups as well as in single-subjects. This offers opportunities for the application of such a design in clinical practice.
authors.affiliation: Department of Neuroradiology, Ghent University, Belgium. ann.tieleman@ugent.be
authors.forename: Ann
authors.initials: A
authors.lastname: Tieleman
authors.forename: Ruth
authors.initials: R
authors.lastname: Seurinck
authors.forename: Karel
authors.initials: K
authors.lastname: Deblaere
authors.forename: Pieter
authors.initials: P
authors.lastname: Vandemaele
authors.forename: Guy
authors.initials: G
authors.lastname: Vingerhoets
authors.forename: Eric
authors.initials: E
authors.lastname: Achten
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D002965:Classification; D003627:Data Interpretation, Statistical; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006624:Hippocampus / Q000502:physiology; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008568:Memory / Q000502:physiology; D008606:Mental Processes / Q000502:physiology*; D008875:Middle Aged; D009415:Nerve Net / Q000502:physiology; D020534:Parahippocampal Gyrus / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D012107:Research Design; D013238:Stereotaxic Techniques; D013702:Temporal Lobe / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*