Forelimb performance by squirrel monkeys (Saimiri sciureus) before and after dorsal column lesions

Area of Science:

• Neuroscience
• Primate research
• Motor control

Background:

• Old World monkeys with dorsal column lesions display impaired reaching movements.
• The functional role of dorsal columns in primate forelimb control is not fully understood.
• Previous studies focused on Old World monkeys, leaving a gap in understanding New World monkey sensorimotor deficits.

Purpose of the Study:

• To quantify the effects of dorsal column lesions on reaching and catching behaviors in squirrel monkeys (New World monkeys).
• To compare the sensorimotor performance of squirrel monkeys with Old World monkeys following similar lesions.
• To investigate potential discrepancies in forelimb deficits between New World and Old World monkeys.

Main Methods:

• Squirrel monkeys underwent high cervical dorsal column lesions or sham operations.
• Preoperative and postoperative performance was assessed using reaching for stationary bait and catching falling bait tasks.
• Behavioral data were quantified and compared between lesioned and control groups.

Main Results:

• Squirrel monkeys with dorsal column lesions showed significant impairment specifically in catching falling bait.
• No significant deficits were observed in reaching for stationary bait compared to controls.
• This contrasts with Old World monkeys, which exhibit broader reaching impairments.

Conclusions:

• Dorsal column function in sensorimotor control differs between New World and Old World monkeys.
• The specific deficit in catching suggests a critical role for dorsal column-mediated proprioception in dynamic, visually-guided tasks.
• Further research is needed to elucidate the neuroanatomical and functional bases for these interspecies differences.