[Study of Successful Emotional Memory Encoding with Functional Magnetic Resonance Imaging: A Meta-Analysis Comparing the Affective Salience of Words Versus Images].

Background: Functional magnetic resonance imaging (fMRI) studies examining emotional memory encoding often use event-related designs with stimuli in the form of words or pictures. Prior research has suggested differential hemispheric specialization for these stimulus types, yet no meta-analysis has directly compared the neural systems involved in each.

Methods: A meta-analysis was conducted using peer-reviewed, event-related fMRI studies. The Activation Likelihood Estimation (ALE) method was applied via GingerALE software to compare brain activations associated with the encoding of affective visual stimuli presented as either words or photographs. Three contrasts were assessed: pictures > neutral + control, words > neutral + control, and overlap between both.

Results: Picture stimuli elicited bilateral activation in the medial parahippocampus, while word stimuli produced left-lateralized activation in the lateral parahippocampus. The overlap analysis identified a shared region in the parahippocampal amygdala. All three contrasts revealed significant activations in key medial temporal lobe (MTL) regions involved in emotional memory, including the hippocampus and amygdala.

Conclusions: Both stimulus types engaged medial temporal networks specialized in emotional memory encoding. Word stimuli selectively activated regions lateralized to the left hemisphere, whereas picture stimuli produced bilateral activation with a leftward bias. This study provides the first meta-analytic evidence of a medial-lateral differentiation in the parahippocampal gyrus based on emotional stimulus type.