This study is part of an effort to map
neural systems involved in the processing of
emotion, and it focuses on the possible cortical
components of the process of recognizing facial
expressions. We hypothesized that the cortical
systems most responsible for the recognition of
emotional facial expressions would draw on
discrete regions of right higher-order sensory
cortices and that the recognition of specific
emotions would depend on partially distinct
system subsets of such cortical regions. We
tested these hypotheses using lesion analysis in
37 subjects with focal brain damage. Subjects
were asked to recognize facial expressions of
six basic emotions: happiness, surprise, fear,
anger, disgust, and sadness. Data were analyzed
with a novel technique, based on
three-dimensional reconstruction of brain
images, in which anatomical description of
surface lesions and task performance scores were
jointly mapped onto a standard brain-space. We
found that all subjects recognized happy
expressions normally but that some subjects were
impaired in recognizing negative emotions,
especially fear and sadness. The cortical
surface regions that best correlated with
impaired recognition of emotion were in the
right inferior parietal cortex and in the right
mesial anterior infracalcarine cortex. We did
not find impairments in recognizing any emotion
in subjects with lesions restricted to the left
hemisphere. These data provide evidence for a
neural system important to processing facial
expressions of some emotions, involving discrete
visual and somatosensory cortical sectors in
right hemisphere.
A
neuromodulatory role for the human amygdala in
processing emotional facial expressions
Brain (1998), 121, 47-57
J. S. Morris, K. J. Friston, C. Buchel, C. D.
Frith, A. W. Young, A. J. Calder and R. J. Dolan
Wellcome Department of Cognitive
Neurology, Royal Free and University College
Hospitals School of Medicine, London and MRC
Applied Psychology Unit, Cambridge, UK
Correspondence to: Professor R. J. Dolan,
Wellcome Department of Cognitive Neurology, 12
Queen Square, London WC1N 3BG, UK
Localized amygdalar lesions in humans produce
deficits in the recognition of fearful facial
expressions. We used functional neuroimaging to
test two hypotheses:
(1) that the amygdala and some of its
functionally connected structures mediate
specific neural responses to fearful
expressions;
(2) that the early visual processing of
emotional faces can be influenced by amygdalar
activity. Normal subjects were scanned using PET
while they performed a gender discrimination
task involving static grey-scale images of faces
expressing varying degrees of fear or
happiness.
In support of the first hypothesis, enhanced
activity in the left amygdala, left pulvinar,
left anterior insula and bilateral anterior
cingulate gyri was observed during the
processing of fearful faces. Evidence consistent
with the second hypothesis was obtained by a
demonstration that amygdalar responses predict
expressionspecific neural activity in
extrastriate cortex.
Verbal and Nonverbal
Emotional Memory Following Unilateral Amygdala
Damage Learning Memory Vol. 8,
No. 6, pp. 326-335, November/December 2001
Tony W. Buchanan,1 Natalie L. Denburg, Daniel
Tranel, and Ralph Adolphs
Department of Neurology,
Division of Cognitive Neuroscience, University
of Iowa, College of Medicine, Iowa City, Iowa
52242, USA
The amygdala is involved in the normal
facilitation of memory by emotion, but the
separate contributions of the left and right
amygdala to memory for verbal or nonverbal
emotional material have not been investigated.
Fourteen patients with damage to the medial
temporal lobe including the amygdala (seven
left, seven right), 18 brain-damaged, and 36
normal controls were exposed to emotional and
neutral pictures accompanied by verbal
narratives. Memory for both narratives and
pictures was assessed with a free recall test 24
h later. Subjects with left amygdala damage
failed to show the normally robust enhancement
of memory for verbal and nonverbal emotional
stimuli. The group with right amygdala damage
showed the normal pattern of facilitation of
memory by emotion for both verbal and nonverbal
stimuli despite an overall reduction in memory
performance. Furthermore, subjects with left
amygdala damage were disproportionately impaired
on memory for emotional narratives as compared
with memory for emotional pictures. The latter
finding offers partial support for a lateralized
and material-specific pattern of the amygdala's
contribution to emotional memory.
The Role of the Primate
Amygdala in Conditioned Reinforcement
The Journal of Neuroscience,
October 1, 2001, 21(19):7770-7780
John A. Parkinson, Harriet S. Crofts, Mike
McGuigan, Davorka L. Tomic, Barry J. Everitt,
and Angela C. Roberts
Departments of Anatomy and
Experimental Psychology, University of
Cambridge, Cambridge CB2 3DY, United Kingdom
Conditioned reinforcement refers to the
capacity of a conditioned stimulus to support
instrumental behavior by acquiring affective
properties of the primary reinforcer with which
it is associated. Conditioned reinforcers
maintain behavior over protracted periods of
time in the absence of, and potentially in
conflict with, primary reinforcers and as such
may play a fundamental role in complex social
behavior. A relatively large body of evidence
supports the view that the amygdala (and in
particular the basolateral area) contributes to
conditioned reinforcement by maintaining a
representation of the affective value of
conditioned stimuli. However, a recent study in
primates (Malkova et al., 1997), using a
second-order visual discrimination task,
suggests that the amygdala is not critical for
the conditioned reinforcement process.
In the present study, excitotoxic lesions of
the amygdala in a new world primate, the common
marmoset, resulted in a progressive impairment
in responding under a second-order schedule of
food reinforcement. In addition, the responding
of amygdala-lesioned animals was insensitive to
the omission of the conditioned reinforcer,
unlike that of control animals, for which
responding was markedly reduced. In contrast,
lesioned animals were unimpaired when responding
on a progression of fixed-ratio schedules of
primary reinforcement. These data confirm that
the amygdala is critical for the conditioned
reinforcement process in primates, and taken
together with other recent work in monkeys,
these results suggest that the contribution of
the amygdala is to provide the affective value
of specific reinforcers as accessed by
associated conditioned stimuli.
