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The medial temporal lobe (MTL) is traditionally considered to be a system that is specialized for long-term memory. Recent work has challenged this notion by demonstrating that this region can contribute to many domains of cognition beyond long-term memory, including perception and attention. One potential reason why the MTL (and hippocampus specifically) contributes broadly to cognition is that it contains relational representations—representations of multidimensional features of experience and their unique relationship to one another—that are useful in many different cognitive domains. Here, we explore the hypothesis that the hippocampus/MTL plays a critical role in attention and perception via relational representations. We compared human participants with MTL damage to healthy age- and education-matched individuals on attention tasks that varied in relational processing demands. On each trial, participants viewed two images (rooms with paintings). On “similar room” trials, they judged whether the rooms had the same spatial layout from a different perspective. On “similar art” trials, they judged whether the paintings could have been painted by the same artist. On “identical” trials, participants simply had to detect identical paintings or rooms. MTL lesion patients were significantly and selectively impaired on the similar room task. This work provides further evidence that the hippocampus/MTL plays a ubiquitous role in cognition by virtue of its relational and spatial representations and highlights its important contributions to rapid perceptual processes that benefit from attention.
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Encoding of visual objects in the human medial temporal lobe
The human medial temporal lobe (MTL) plays a crucial role in recognizing visual objects, a key cognitive function that relies on the formation of semantic representations. Nonetheless, it remains unknown how visual information of general objects is translated into semantic representations in the MTL. Furthermore, the debate about whether the human MTL is involved in perception has endured for a long time. To address these questions, we investigated three distinct models of neural object coding—semantic coding, axis-based feature coding, and region-based feature coding—in each subregion of the MTL, using high-resolution fMRI in two male and six female participants. Our findings revealed the presence of semantic coding throughout the MTL, with a higher prevalence observed in the parahippocampal cortex (PHC) and perirhinal cortex (PRC), while axis coding and region coding were primarily observed in the earlier regions of the MTL. Moreover, we demonstrated that voxels exhibiting axis coding supported the transition to region coding and contained information relevant to semantic coding. Together, by providing a detailed characterization of neural object coding schemes and offering a comprehensive summary of visual coding information for each MTL subregion, our results not only emphasize a clear role of the MTL in perceptual processing but also shed light on the translation of perception-driven representations of visual features into memory-driven representations of semantics along the MTL processing pathway. Significance StatementIn this study, we delved into the mechanisms underlying visual object recognition within the human medial temporal lobe (MTL), a pivotal region known for its role in the formation of semantic representations crucial for memory. In particular, the translation of visual information into semantic representations within the MTL has remained unclear, and the enduring debate regarding the involvement of the human MTL in perception has persisted. To address these questions, we comprehensively examined distinct neural object coding models across each subregion of the MTL, leveraging high-resolution fMRI. We also showed transition of information between object coding models and across MTL subregions. Our findings significantly contributes to advancing our understanding of the intricate pathway involved in visual object coding.
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- Award ID(s):
- 2401398
- PAR ID:
- 10493492
- Publisher / Repository:
- DOI PREFIX: 10.1523
- Date Published:
- Journal Name:
- The Journal of Neuroscience
- ISSN:
- 0270-6474
- Format(s):
- Medium: X Size: Article No. e2135232024
- Size(s):
- Article No. e2135232024
- Sponsoring Org:
- National Science Foundation
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