Grant Number: 5F31MH072059-02
Project Title: Neural Mechanisms for Emotion in the Amygdala
PI Information: KEVIN M. SPITLER,
[email protected]
Abstract: DESCRIPTION (provided by applicant): The fast pace
and increased psycho-social stress of life in developed countries is
correlated with a large increase in affective disorders. Thirty-seven
million Americans suffer from a form of anxiety or depression (Narrow et
al., 1998; Robins and Regier, 1990). Conventional treatments are only
partially successful in combating these disorders because the neural
mechanisms underlying normal and pathological emotion are not fully
understood. One well-established finding is that the amygdala, a cluster
of deep brain nuclei, is a key structure in the complex brain circuit of
emotions. In this circuit, incoming signals from all sensory modalities
converge in the amygdala where they are converted into modulatory
signals directed at memory structures and to autonomic centers of
emotional response. The goal of this project is to use
neurophysiological techniques to elucidate the neural mechanisms that
underlie the differentiation of emotional stimuli, the formation of
emotional memories, and the orchestration of somatic and autonomic
responses in the primate amygdala
Thesaurus Terms:
amygdala, emotion, memory, neural information processing,
neuropsychology
arousal, heart rate, psychophysiology, visual stimulus
Macaca mulatta, behavioral /social science research tag,
neuropsychological test, predoctoral investigator
Institution: UNIVERSITY OF ARIZONA
PO BOX 3308
TUCSON, AZ 857223308
Fiscal Year: 2006
Department: DIVISION OF NEUROBIOLOGY
Project Start: 09-SEP-2005
Project End: 08-SEP-2007
ICD: NATIONAL INSTITUTE OF MENTAL HEALTH
IRG: ZRG1
Neural Responses to Facial Expression and Face
Identity in the Monkey Amygdala
K. M. Gothard1, F. P. Battaglia2,
C. A. Erickson3, K. M. Spitler1
and D. G. Amaral4
1Department of Physiology,
College of Medicine, The University of Arizona, Tucson, Arizona;
2Graduate School of Neurosciences
Amsterdam, Faculty of Science, Swammerdam Institute for Life Sciences,
Center for Neuroscience, University of Amsterdam, Amsterdam, The
Netherlands; 3Helen Wills
Neuroscience Institute, University of California–Berkeley, Berkeley; and
4Department of Psychiatry and
Behavioral Sciences, The California National Primate Research Center and
The Music Intelligence Neural Development Institute, University of
California–Davis, Sacramento, California
Submitted 12 July 2006; accepted in final form 2 November 2006
J Neurophysiol 97: 1671-1683, 2007
Surgical procedures
All surgical procedures were carried out in compliance with National
Institutes of Health guidelines and were approved by the IACUC at the
University of Arizona. Two adult male rhesus monkeys (Macaca mulatta)
(monkeys S and H) were surgically prepared for multielectrode recordings
from the amygdala using a two-step surgical procedure. For both surgical
procedures the monkeys were preanesthetized with ketamine (10–15 mg/kg),
administered intramuscularly, and brought to surgical levels of
anesthesia with isoflurane (1–1.5%) supplemented with fentanyl (7–10 µg
• kg–1 • h–1). During the first procedure, monkeys were implanted with
three titanium tripod plates, custom-manufactured by Thomas Recording
(Giessen, Germany). Each tripod plate had an elevated center with a
threaded screw hole and three flat radial support arms emerging at 120°
intervals. The three support arms were 10 mm long, 2 mm wide, and were
perforated at the end to accommodate a 2-mm-diameter bone screw. The
arms were bent to match the curvature of the skull and affixed to the
bone with screws. Two plates were affixed posteriorly, 15 mm lateral
from midline and approximately 20 mm posterior from the interaural line.
The third plate was affixed straddling the midline 2 cm anterior to the
interaural line. The temporalis muscle and the scalp were closed over
the plates and the bone was allowed to heal and grow around the plates
(about 4–12 mo). Once substantial bone growth had occurred around the
screws and the arms of the plates (verified by CT scan), the second
procedure was undertaken in which the scalp above the plates was
perforated and small threaded head posts (3-mm-diameter shaft, 15-mm
length, 5-mm-diameter spherical head) were screwed into the center of
each of the tripod plates. The posts served as anchors for a removable
stainless steel ring that was secured in a rigid frame during
experiments. Such an arrangement distributed the torque generated by
head immobilization across the three head posts.
During the second surgical procedure, a recording chamber was secured
with bone screws and bone cement to the skull above the amygdala. The
chamber was placed at stereotaxic coordinates calculated from a
structural MRI carried out before surgery. Magnetic search coils were
also implanted in the left eye of one of monkey (S) following standard
procedures (Judge et al. 1980 ; Robinson 1963 ). After a 10-day recovery
period, monkeys were trained to tolerate head immobilization and to
fixate on objects presented on a computer monitor. When behavioral
training was complete, a 6- to 8-mm-diameter craniotomy was performed
within the chamber.
Behavioral training
The monkeys were trained to fixate on a white square that subtended 0.5
degree of visual angle (dva). The eye movements of monkey S were tracked
with a resolution of 0.25 dva and were digitized at 500 Hz using an
analog eye tracker (DNI, Newark, DE). Eye movements of monkey H were
monitored with the infrared eye tracker (Iscan, Burlington, MA) with a
resolution of 0.5 dva. Both eye trackers were connected to the CORTEX
experimental control system (NIMH-supported freeware from the website:
http://www.cortex.salk.edu) .
When the eyes were fixated for 150 ms at the white square, the fixation
icon was removed from the monitor and a stimulus image, subtending 12
dva, was displayed. The monkeys were allowed to freely scan the image,
with the requirement to maintain gaze within the boundaries of the
image. If this requirement was met for the entire duration of the
display (500 ms or 1 s) the monkeys received a 0.5- to 1-ml reward
droplet. The reward consisted of a paste of mashed granola, rice cereal,
and fruit juice or simple fruit juice mixed with applesauce. To
disambiguate the effect of the reward from the effect of the stimuli,
monkeys received a reward on only 50% of the trials, so that each image
was followed an equal number of times by reward or no reward. The
duration of the intertrial interval (ITI) was 1 s. When the monkey's
eyes moved outside the boundary of the image, the trial was terminated
by removing the image from the monitor. Error trials were not rewarded
and were followed by a 2-s time-out period. Error trials were excluded
from the analysis. To prevent habituation and blunting of the emotional
response to face stimuli, the sets of images used for training or used
during the period when we searched for neurons in the amygdala did not
contain monkey faces or images intended for presentation during
neurophysiological recordings. |