Lastly, remove the upper and lower eyelids with fine forceps and micro scissors. Once the cranium is empty, examine the cranial cavity floor and identify nerves three, four, and six. Remove the remaining parts of the brainstem from the head with fine forceps and micro scissors. Cut cranial nerve six on both the left and right side. Tilt the brainstem to one side and observe cranial nerve six, the abducens nerve, emerging from the ventral surface near the junction of the pons and medulla. Cut nerves three and four where they attach to the midbrain. Then cut the left and right ride of the optic nerve, or cranial nerve two. The diameter of nerve four is slightly less than nerve three. Cranial nerve three can be seen in front of cranial nerve four. Then use micro scissors to gentle push the midbrain toward the midline and expose the cranial nerves. Next, used curved forceps to gently pull the cerebrum caudally and produce slight tension on the cranial nerves.Ĭarefully cut away and remove the olfactory bulbs and cerebrum with curved forceps. Continue to irrigate the brain with turtle ringer solution as necessary. Remove enough meninges to allow identification of the olfactory bulbs in the anterior cranial cavity. Use micro scissors to remove the meninges and expose the rest of the brain. Then, make two superficial cuts on the dorsal cranium starting at the foramen magnum and carefully pull off the dorsal cranium. Use rongeurs to remove the vertebral column and other tissue from the cranium by pulling caudally. After identifying the vertebral column at the cavum end of the cranium, bend the vertebral column ventrally to expose the spinal cord, and use micro scissors to the snip the spinal cord. Then, pull off the skin and muscles from their attachments at the dorsal and lateral regions of the cranium. Next, use rongeurs to pull the lower jaw away from the cranium. Then, while working under a dissection microscope, cut the joint connecting the dentary bone to the cranium with the scalpel. Place a blunt dissection probe through the mouth to provide easier handling of the head. Maintain the tissue at four degrees Celsius, by placing ice around the outside of the dish. Have enough turtle ringer solution on hand to irrigate the tissue. Begin with the turtle head in a dissection dish. ![]() The main advantage of this technique is that it does not require training animals to track targets and uses a gimbal to calibrate their eye movements.ĭemonstrating this technique is Steven Nesbit, an undergraduate student in my laboratory. This method can help answer key questions in the ocular-motor field, such as how vision evolved in turtles. The overall goal of this electrophysiological protocol is tho provide the ability to measure the kinematics of eye movements of the red-eared slider turtle using an in vitro isolated head preparation.
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