Neuroscience 1998

Abstract submitted for presentation at the
1998 meeting of the Society for Neuroscience

WAYFINDING IN A VIRTUAL ENVIRONMENT:
BEHAVIORAL AND ELECTROPHYSIOLOGICAL EFFECTS OF OPTIC FLOW AND DISTINCTIVE VISUAL LANDMARKS Michael Kahana, Robert Sekuler, Joseph Madsen, Matt Kirschen & Jeremy Caplan
Volen Center, Brandeis University, Waltham MA 02254, and Children's Hospital, Boston MA 02215

What role do visual and cognitive factors play in sequence learning and wayfinding? To answer such questions, we had human subjects navigate multiple-T junction mazes in a computer rendered, virtual 3D environment. Over repeated encounters with the same maze layout, subjects' responses at choice points became faster and less error-prone. To explore the representations being learned in this task, we created mazes that vary along three dimensions:

the number of T-junctions

the presence or absence of distinctive landmarks at decision points, and

the presence or absence of compelling optic flow as subjects move through maze corridors.

For mazes exceeding the span of immediate memory, learning is significantly facilitated by either optic flow or distinctive landmarks.

To perform this task successfully, subjects must overcome massive associative interference generated when only two different responses (left or right turns) are mappped onto many, identical choice points. Distinctive visual landmarks help to differentiate choice points, thereby reducing associative interference. Optic flow may play a similar role by allowing subjects to construct a cognitive map that can be used to distinguish otherwise identical choice points.

In addition to behavioral studies on normal subjects, we report electrophysiological results from epileptic patients who had subdural electrodes implanted as part of a pre-surgical evaluation. ERPs, time locked to responses at maze decision points, were obtained at multiple electrode sites across the surface of the medial temporal lobe and near the hippocampus.