IMAGE MEMORABILITY: EFFECTS ON VISUAL PROCESSING IN THE VENTRAL STREAM AND MEDIAL TEMPORAL LOBE

Image memorability captures the probability of an image to be later remembered. We aim to characterize the spatiotemporal profile of memorability-related modulations across functionally distinct areas of the ventral visual stream, from early visual cortex to the medial temporal lobe. Additionally, we investigate the association between memorability and directed functional connectivity between areas early and late in the visual hierarchy.
To address these questions, we recorded local field potentials from 15 patients with pharmaco-resistant epilepsy using stereotactic electroencephalography (sEEG) as they completed an image recognition task. Stimuli comprised 1000 images from the natural scenes dataset. We defined regions of interest using the HCP-MMP1 atlas, from which we extracted time-resolved power estimates of broadband high-frequency activity (HFP). The effect of image memorability on HFP over time and across regions was assessed using linear mixed models.
Preliminary results indicate that increased image memorability is associated with modulations of HFP over multiple areas. The earliest and strongest effects were observed in the fusiform gyrus (TF, VVC) and perirhinal cortex (PeEc), characterized by increases in HFP. These increases preceded decreases in V2, ventromedial (VMV1-3) and parahippocampal areas (PHA1-3). No significant effects were observed in V1, presubiculum (PreS), or entorhinal cortex (EC).
In summary, image memorability is associated with dynamic changes in visual processing. Interestingly, the spatiotemporal profile of HFP modulations form two distinct groups of ventral visual areas. Ongoing analyses of time-varying spectral Granger causality are expected to reveal whether directed information flow between regions within these two groups is distinctly associated with memorability.