Minnesota Primate Freedom Project

High Resolution Imaging of Primate Cortex

6 monkeys- Rhesus

At the end of the study, monkeys are killed by drug overdose of “Thiopental (150 MG/KG) or Pentobarbitol (120 MG/KG)

Magnetic Resonance Imaging:

“These studies will focus on developing high resolution imaging techniques…” The Rhesus primates are anesthetized and “…placed in a primate chair, and secured via a surgical implanted plastic headpost.” After that, the primate’s brains are scanned with a “new high field strength magnet (9.4 T).” Then, after using anesthetized monkeys, Ghose “…will apply these protocols to trained awake animals.” Primates will sit in a “primate chair and be head fixed as with the anesthetized animals. 30 db foam earplugs will be used to minimize distraction from the magnet. Animals will perform visual tasks and be rewarded for correct responses by liquid delivered by a juice tube. Eye movements will be monitored using a non-invasive video camera system.”

Optical Imaging:

“After behavioral training (see below), an imaging chamber will be surgically implanted in a sterile recovery procedure. A craniotomy will be performed and the dura reflected to expose the cortical surface. An optically transparent and biologically inert plastic (Tecoflex) will then be implanted to protect the cortex and serve as an artificial dura.” Then, the monkey’s head is attached to a post. After that, “A lens and illumination assembly is then secured to the imaging chamber. The animal is placed in the recording room and a CCD camera is secured to the lens assembly. When the day’s imaging is completed, the camera is removed and the animal is returned to the prep area.”

Head Post Surgery:

First, a “…crescent-shaped incision is made in scalp so that a flap of skin can be retracted. The retracted flap is wrapped with saline-soaked gauze.” Then, “A plastic (PEEK) headpost whose base is composed of 5 plates is placed on the skull. Each plate has 2 to 3 screw holes. Holes are dilled and tapped in the skull and screws are inserted through the plates and into the bone.” After that, “The skin incisions are then closed using either nondigestible sutures (Ethicon) or stainless steel staples. When all procedures are completed, the animal is removed from the sterotaxic holder and anesthesia is discontinued.”

Recording/Imaging Device Implant:

First, the skin is cut to make a flap. Then, the recording device is put on the correct place on the skull. After that, holes are drilled in the monkey’s skull and the recording device is attached with screws and dental cement.

---The monkeys are under 15 MG/KG of Ketamin and 25 MG/KG of Pentothal. It is also worth noting that the “Animals are typically maintained from 2 to 5 years after initial head post surgery.” Also, one to two more recording chambers are put in later because “…the chambers have a limited useful lifetime.”

***The information above may be incomplete due to insufficient data provided to the Minnesota Primate Freedom Project from the University of Minnesota***