Independent coding of target distance and direction in visuo-spatial working memory

Area of Science:

• Cognitive Neuroscience
• Human Motor Control
• Spatial Cognition

Background:

• Manual reaching movements exhibit independent programming of direction and distance.
• The representation of visually-presented locations in short-term memory is hypothesized to be motoric and independent.

Purpose of the Study:

• To investigate whether spatial working memory encodes visual location direction and distance independently.
• To explore the role of motoric coding in spatial short-term memory.

Main Methods:

• Two experiments tested adult humans' ability to remember visual target locations presented egocentrically in darkness.
• Experiment 1 examined temporal decay of location memory (4-30s).
• Experiment 2 assessed interference effects when remembering sequential locations.

Main Results:

• Memory for both direction and distance decayed over time, with distance errors greater in left hemispace.
• Direction and distance errors were uncorrelated, indicating independent encoding.
• Encoding a second location selectively interfered with directional memory, not distance memory.

Conclusions:

• Spatial working memory encodes egocentric visual locations with independent direction and distance parameters.
• Findings strongly suggest the use of motor-related representations in spatial working memory.
• The study contributes to understanding multiple spatial representations in visuo-spatial short-term memory.