Spatial updating in amnesia using an eye movement analogue of a path integration task

Area of Science:

• Neuroscience
• Cognitive Psychology
• Human Navigation

Background:

• Path integration (PI) enables organisms to track their location relative to a starting point.
• Previous research linked the hippocampus/medial temporal lobes (MTL) to whole-body PI and self-position updating.
• The role of the hippocampus/MTL in updating gaze position during navigation remained unclear.

Purpose of the Study:

• To investigate whether the hippocampus/MTL is essential for the spatial updating of gaze position.
• To examine the neural underpinnings of gaze spatial updating using a PI-analog task.
• To compare navigation strategies in individuals with hippocampal lesions versus controls.

Main Methods:

• Utilized an eyetracking version of a path integration (PI) analog task.
• Tested two individuals (DA, BL) with hippocampal lesions and healthy control participants.
• Participants tracked visual cues along routes and were cued to return to start or mid-route locations.

Main Results:

• Individual DA, despite extensive MTL damage, showed near-control accuracy but altered saccade latency and fewer gaze revisits.
• Individual BL, with more circumscribed hippocampal damage and parietal involvement, exhibited reduced accuracy and increased reliance on overt revisits.
• Distinct behavioral patterns emerged between the two patients and controls, highlighting differential contributions.

Conclusions:

• Spatial updating of gaze position involves interactive processes supported by the hippocampus/MTL and posterior parietal cortex.
• The hippocampus/MTL and posterior parietal cortex play distinct but interactive roles in supporting gaze spatial updating.
• Lesion-specific effects on navigation behavior suggest complex neural interactions underlying spatial cognition.