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Anna Shafer-Skelton, Julie Golomb; Decoding of visual stimulus location in the human hippocampus. Journal of Vision 2016;16(12):873. doi: 10.1167/16.12.873.
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© ARVO (1962-2015); The Authors (2016-present)
The hippocampus is an area well known for its role in memory and spatial navigation, and it has recently been implicated in visual perception. Surprisingly, there has been little research investigating how locations of visual stimuli are represented in the hippocampus. Here, we ask: 1) Does the hippocampus contain representations of stimulus location?, 2) What type of location does it represent?, and 3) Is location represented in the same areas of hippocampus as stimulus category? Using a blocked design, we presented participants with stimuli (objects or scenes) in a given location (left or right of fixation) while they maintained a given gaze position (left or right side of screen). We used fMRI MVPA to test whether hippocampus contained different types of information about visual stimuli, e.g. category information, "within-fixation location information" (for conditions that shared the same gaze position), and "across-fixation location information" (for conditions that differed in gaze position). In the right hippocampus, we could decode information about both the category and location of a stimulus. Notably, this location information was preserved across different gaze positions in retinotopic (gaze-centered) coordinates, with a similar magnitude to within-fixation location information. These results were similar to what has been found in higher-level visual cortex (Golomb & Kanwisher, 2012). We next performed searchlight analyses within hippocampus to examine the distribution of each type of information. We found a strong correlation between the searchlight outputs for within-fixation location information and across-fixation retinotopic information, suggesting that these two types of location information could share a similar neural representation. In contrast, neither type of location information was correlated with category information, and the location-location correlations were significantly stronger than the location-category correlations. This suggests that different parts of the hippocampus may be responsible for location vs. category information, which could have important implications for object-location binding.
Meeting abstract presented at VSS 2016
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