Eye-head-hand coordination during visually guided reaches in head-unrestrained macaques

Area of Science:

• Neuroscience
• Primate behavior
• Motor control

Background:

• Previous studies focused on eye-head or eye-hand coordination separately in nonhuman primates.
• The combined coordination of eye, head, and hand movements remained unexamined.

Purpose of the Study:

• To investigate the interplay between reaching and eye-head coordination in rhesus macaques.
• To determine if reaching influences gaze control and vice versa.

Main Methods:

• Recorded eye, head, and hand motion using search coil and touch screen technology in two rhesus macaques.
• Compared movement kinematics during a visually guided reach-to-touch task versus gaze-control tasks.
• Varied initial hand and gaze positions to assess their influence on coordination.

Main Results:

• Reaching tasks elicited prolonged head motion toward the target, increasing head velocity and amplitude.
• Eye-in-head range decreased during reaching compared to gaze-only control.
• Gaze shifts were faster, more precise, and had shorter latencies during reaching.
• Initial gaze position affected reach latency, but initial hand position did not influence gaze.

Conclusions:

• Eye-head coordination is adapted to optimize visually guided reaching.
• Gaze is rapidly and accurately directed to the target to guide the hand.
• Head movements help center the eyes, potentially enhancing binocular vision for depth perception during reach.