Pictorial depth cues always influence reaching distance.

Area of Science:

• Neuroscience
• Cognitive Psychology
• Visual Perception

Background:

• Depth perception is crucial for visually guided actions like reaching.
• The role of pictorial depth cues in modulating reaching behavior is not fully understood.
• Previous research suggests potential involvement of ventral and dorsal visual streams.

Purpose of the Study:

• To investigate the influence of pictorial depth cues on the amplitude of reaching movements.
• To determine the specific components of pictorial depth that affect reaching.
• To explore how factors like visual feedback and visual agnosia impact this influence.

Main Methods:

• Projecting backgrounds with linear perspective and texture gradients onto a tabletop.
• Measuring reaching amplitudes to targets within these projected backgrounds in healthy participants and a patient with visual agnosia.
• Manipulating viewing conditions (monocular), response hand, memory delay, and visual feedback.

Main Results:

• A clear effect of pictorial depth on reaching was observed, driven by background pattern convergence.
• Each degree of pictorial convergence increased reaching distance by 0.5 mm.
• The effect was not altered by monocular viewing, left-hand response, or memory delay.
• Visual feedback during the reach, but not terminal feedback, mitigated the effect.
• Patient DF with visual form agnosia showed a normal response to pictorial depth cues.

Conclusions:

• Pictorial depth cues, particularly convergence, significantly modulate reaching amplitude.
• The findings challenge the notion that pictorial depth effects on reaching originate solely from ventral stream analyses.
• The results support the involvement of dorsal stream or earlier visual processing stages in integrating pictorial depth for action.
• Visual feedback during movement is critical for calibrating reaching based on pictorial depth.