Preserved Extra-Foveal Processing of Object Semantics in Alzheimer’s Disease

Abstract

Alzheimer’s disease (AD) patients underperform on a range of tasks requiring semantic processing, but it is unclear whether this impairment is due to a generalised loss of semantic knowledge or to issues in accessing and selecting such information from memory. The objective of this eye-tracking visual search study was to determine whether semantic expectancy mechanisms known to support object recognition in healthy adults are preserved in AD patients. Furthermore, as AD patients are often reported to be impaired in accessing information in extra-foveal vision, we investigated whether that was also the case in our study. Twenty AD patients and 20 age-matched controls searched for a target object among an array of distractors presented extra-foveally. The distractors were either semantically related or unrelated to the target (e.g., a car in an array with other vehicles or kitchen items). Results showed that semantically related objects were detected with more difficulty than semantically unrelated objects by both groups, but more markedly by the AD group. Participants looked earlier and for longer at the critical objects when these were semantically unrelated to the distractors. Our findings show that AD patients can process the semantics of objects and access it in extra-foveal vision. This suggests that their impairments in semantic processing may reflect difficulties in accessing semantic information rather than a generalised loss of semantic memory.

Locations of objects are better remembered than their identities in naturalistic scenes: An eye-tracking experiment in mild cognitive impairment.

“…Nevertheless, our findings remain at odds with studies looking at measures related to the critical object, such as the gaze duration, especially for changes of feature conjunctions (i.e., a change in location and identity), which was expected to generate a clear differential between the two groups (Fernández et al, 2018). The evidence of persevered patterns of overt attention, instead, corroborates recent findings by Cimminella et al (2022) showing that extrafoveal capture by object semantics is intact in people with AD. Regardless of the group, we observed significant differences in the eye-movement measures associated with the type of change.…”