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Duke University Primate Experiments Heather L. Dean1, Justin C.
Crowley4,5 and Michael L. Platt1,2,3 1Department of Neurobiology, 2Center for
Cognitive Neuroscience, and 3Department of Biological
Anthropology and Anatomy, Duke University Medical Center, Durham, North
Carolina 27710; and 4Department of Biological Sciences and
5Center for the Neural Basis of Cognition, Carnegie Mellon
University, Pittsburgh, Pennsylvania 15213 Animal subjects Two adult male rhesus macaques (Macaca mulatta) were used as
subjects in these experiments. All animal procedures were
developed in association with Duke University Medical Center
veterinarians and were approved by the Duke University
Institutional Animal Care and Use Committee. These procedures
were designed and conducted in compliance with the Public
Health Service's Guide for the Care and Use of Animals.
Surgical procedures A head-restraint prosthesis and scleral search coil (Fuchs and
Robinson 1966;
Judge et al. 1980)
were implanted in an initial aseptic surgical procedure
performed under isoflurane anesthesia. First, the dorsal
rostrum of the skull was exposed and six 2.5-mm holes were
drilled through the skull with standard orthopedic surgical
instruments. These holes were then tapped for 3.5-mm
fine-thread orthopedic cortical bone screws. Sterile orthopedic
bone cement (Biomet; Palacos) was used to bond a stainless steel
head post (Crist Instruments) lowered to just above the skull
surface to 6 titanium screws (Zimmer) inserted into the tapped
holes. The Teflon-insulated scleral search coil (Cooner Wire
AS634) was implanted beneath the conjunctiva, passing just rostral
to the insertions of the extraocular muscles (Judge et al. 1980).
The wire exited the conjunctiva temporally, exited the orbit
subdermally, was embedded in the bone cement that formed the
restraint prosthesis, and terminated in a gold and plastic
electrical connector (Winchester Electronics/Litton). After
surgery, animals received analgesics for a minimum of 3 days.
Antibiotic prophylaxis was initiated intraoperatively and
continued for 7–10 days. Animals were given a 4- to 6-wk
recovery period after surgery. A second aseptic surgical procedure was performed once animals
could reliably execute all the behavioral tasks used in the
study. A stainless steel recording chamber (Crist Instruments)
was positioned stereotaxically perpendicular to the horizontal
plane over a 15-mm craniotomy and bonded to 4–6 additional
orthopedic bone screws and the original implant with orthopedic
bone cement. The recording chamber was centered stereotaxically
at position 0,0, the intersection of the midsagittal and
interaural planes (cf. Olson et al. 1996).
Postoperatively, animals received analgesics for a minimum of
3 days and antibiotics for 7–10 days. The recording chamber
was kept clean with daily antibiotic washes and sealed with
replaceable sterile Cilux caps. Single-cell recording
experiments began after a 1-wk postoperative period. Behavioral techniques Access to water was controlled during training and testing,
and animals were habituated to head restraint and trained to
perform oculomotor tasks for a fruit-juice reward using a
custom-built software interface (Ryklin Software). Visual
stimuli consisted of light-emitting diodes (LEDs; LEDtronics),
which could be illuminated to appear red, green, or yellow to
normal human observers. The LEDs were fixed on a tangent
screen placed 144.78 cm (57 in.) from the eyes of the animal,
forming a grid of points, separated by 1°, spanning 49°
horizontally and 41° vertically. These LEDs could be
illuminated within 1 ms and extinguished within 7 ms by the
computer system controlling the experiments.
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