Experimental motion sickness induced in squirrel monkeys by continuous off-axis horizontal rotation.

Area of Science:

• Neuroscience
• Vestibular System Research
• Animal Behavior Studies

Background:

• Motion sickness is a common human ailment.
• Understanding the physiological basis of motion sickness is crucial for developing countermeasures.
• Animal models provide insights into the mechanisms of motion sickness.

Purpose of the Study:

• To investigate the incidence and characteristics of motion sickness in squirrel monkeys under controlled rotation.
• To quantify the severity of motion sickness by measuring specific physiological responses.
• To explore the influence of visual cues and habituation on motion sickness.

Main Methods:

• Adult male squirrel monkeys were subjected to continuous horizontal rotation at 33 rpm.
• Motion sickness severity was assessed by measuring latencies of sickness-related responses.
• Per- and postrotational nystagmus was recorded using implanted electrodes.
• Visual cues were manipulated by blindfolding a subset of subjects.

Main Results:

• Motion sickness occurred in up to 90% of test sessions with two-hour rotations.
• Transient habituation to motion sickness was observed in only a few monkeys over ten daily sessions.
• The frequency of emetic episodes decreased in the latter half of the rotation series.
• Blindfolding significantly reduced the incidence of vomiting.

Conclusions:

• Rotation duration is a key factor in the incidence of motion sickness.
• While some habituation may occur, it is largely transient.
• Visual input plays a critical role in the manifestation of vomiting in motion sickness.
• Squirrel monkeys serve as a valuable model for studying motion sickness mechanisms.