Emotional Processing
Summary of the organisation of some of the brain mechanisms underlying emotion, showing dual routes to the initiation of action in response to rewarding and punishing, that is emotion-producing, stimuli. The inputs from different sensory systems to brain structures such as the orbitofrontal cortex and amygdala allow these brain structures to evaluate the reward- or punishment-related value of incoming stimuli, or of remembered stimuli. The different sensory inputs allow evaluations within the orbitofrontal cortex and amygdala based mainly on the primary (unlearned) reinforcement value for taste, touch and olfactory stimuli, and on the secondary (learned) reinforcement value for visual and auditory stimuli. In the case of vision, the 'association cortex' which sends representations of objects to the amygdala and orbitofrontal cortex is the inferior temporal visual cortex. One route for the outputs from these evaluative brain structures is via projections directly to structures such as the basal ganglia (including the striatum and ventral striatum) to allow implicit, direct behavioral responses based on the reward or punishment-related evaluation of the stimuli to be made. The second route is via the language systems of the brain, which allow explicit (verbalizable) decisions involving multistep syntactic planning to be implemented. After The Brain and Emotion, Fig. 9. 4.
Some of the pathways involved in emotion described in the text are shown on this lateral view of the brain of the macaque monkey. Connections from the primary taste and olfactory cortices to the orbitofrontal cortex and amygdala are shown. Connections are also shown in the 'ventral visual system' from V1 to V2, V4, the inferior temporal visual cortex, etc., with some connections reaching the amygdala and orbitofrontal cortex. In addition, connections from the somatosensory cortical areas 1, 2 and 3 that reach the orbitofrontal cortex directly and via the insular cortex, and that reach the amygdala via the insular cortex, are shown. as, arcuate sulcus; cal, calcarine sulcus; cs, central sulcus; lf, lateral (or Sylvian) fissure; lun, lunate sulcus; ps, principal sulcus; io, inferior occipital sulcus; ip, intraparietal sulcus (which has been opened to reveal some of the areas it contains); sts, superior temporal sulcus (which has been opened to reveal some of the areas it contains). AIT, anterior inferior temporal cortex; FST, visual motion processing area; LIP, lateral intraparietal area; MST, visual motion processing area; MT, visual motion processing area (also called V5); PIT, posterior inferior temporal cortex; STP, superior temporal plane; TA, architectonic area including auditory association cortex; TE, architectonic area including high order visual association cortex, and some of its subareas TEa and TEm; TG, architectonic area in the temporal pole; V1 - V4, visual areas 1 - 4; VIP, ventral intraparietal area; TEO, architectonic area including posterior visual association cortex. The numerals refer to architectonic areas, and have the following approximate functional equivalence: 1, 2, 3, somatosensory cortex (posterior to the central sulcus); 4, motor cortex; 5, superior parietal lobule; 7a, inferior parietal lobule, visual part; 7b, inferior parietal lobule, somatosensory part; 6, lateral premotor cortex; 8, frontal eye field; 12, part of orbitofrontal cortex; 46, dorsolateral prefrontal cortex. From The Brain and Emotion, Fig. 4. 1.
FIGURE 1: Schematic diagram depicting the processing and storage of exteroceptive sensory information as a cognitive mosaic. Information initially processed by the somesthetic (S), auditory (A), and visual (V) konio- and related-cortices is sent to the medial temporal limbic system via convergent-parallel, multisynaptic pathways (heavier lines). The amygdala suffuses the information with intrapersonal affective tone and the hippocampal formation processes the information into recent memory by consolidating it in the neocortex as a cognitive mosaic anatomically organized by sensory and taxonomic attributes (thinner lines and small arrows). Most likely, the affective tone is cognitively consolidated in the neocortex separately from the sensory and taxonomic attributes. Focal lesions of attribute areas give rise to agnosias, disorders of recognition that involve both recent and remote memory, whereas lesions of the medial temporal lobe give rise to either global or fractional disorders of recent but not remote memory that are multimodal. Bilateral lesions that disconnect a koniocortex from the medial temporal lobes produce a sensory-specific (unimodal) disorder of recent memory with associated hypoemotionality. The role of the frontal cortex in the modulation of cognition and emotion is discussed in section 6.
FIGURE 2: Schematic diagram to illustrate the difference between an attribute memory trace stored as a recent versus a remote memory. If it is stored as a recent memory trace (Oa), then it can only be pulled in and out of storage by another area of cortex (Fa) via the medial temporal (mT) limbic system (thinner lines), similar to indirect memory addressing in computers. If the recent memory trace is converted over time into a remote memory trace, then it can be pulled directly in and out of storage (heavier line) without the participation of the medial temporal lobe, similar to direct memory addressing in computers. Since both recent and remote memories of a sensory or taxonomic cognitive attribute are stored in the same area of cortex, bilateral lesions of that area will produce a recognition deficit or apperceptive agnosia. If the attribute storage area is a dominant brain function, then a unilateral lesion is also capable of producing a recognition deficit, e.g. Wernicke aphasia, the inability to recognize and process the phonetic content of a complex auditory signal, or sensory aprosodia, the inability to recognize and process the affective-prosodic content of a complex auditory signal.
The first paper in the April 2004 issue of CNS
Spectrums, titled
Neuroimaging of Emotions in Psychiatry,
is
Functional Neuroimaging Studies of Human
Emotions, by K. Luan Phan, MD, Tor D. Wager, PhD, Stephan F. Taylor,
MD, and Israel Liberzon, MD. The paper is a survey of 55 PET and fMRI studies
that were done to assess various aspects of brain function in response to
emotional stimuli. They set out to basically develop an atlas of corellations
between different emotional responses and different parts of the brain. This is
something that is inherently difficult to do. As you might expect, different
brains can have widely different responses to the same stimuli. In order to try
to make sense of this, it is necessary to study several different people and
average the results. One of the strongest corellations they found was the
relationship between fear and increased metabolic activity in the
amygdala.
Another strong correlation they found was that the
medial prefrontal cortex often is
activated in response to generic emotional stimuli. By this I mean that the
activation occurred without regard to the type of emotion involved. As they put
it: "The findings suggest that the MPFC may have a 'general' role in emotional
processing." Although they found that "no single brain region is commonly
activated by all emotional tasks," the MPFC was the one that was turned on most
often. Its location in the prefrontal cortex suggests that it may be a linkage
point between emotional processing and cognitive processing: one of the bridges
between thinking and feeling. They point out that "several studies have been
recently published demonstrating that when subjects turn their attention inward
toward themselves, as often required during general emotional processing,
activity within the MPFC is increased. Studies requiring subjects to determine
if personality trait adjectives are descriptive of themselves (versus someone
else) or to reflect on their own abilities/traits/attitudes have observed
engagement of the MPFC."
Another area of interest in emotional neuroscience is the
anterior cingulate cortex. It has been
know for a long time that injury to the ACC can lead to wither apathy or
lability (instability). Therefore, it is tempting to speculate that the ACC is
involved in the regulation or modulation of emotional responses. Their review
of neuroimaging studies of the ACC shows that it is involved in detecting
emotional cues. For example, when watching a movie, your brain is flooded with
all kinds of stimuli, but only some of them have any emotional significance.
The ACC seems to be involved in distinguishing the emotional
figure from the background
noise. The authors speculate about some
possible functions: "As a detector of salient information in general, the ACC
could serve to allocate brain resources, heighten sensitivity and direct
attention to environmental cues produced by the evocative stimulus." They found
also that the ACC is activated when people are asked to recall events that are
linked to a particular emotional state.
Another finding with regard to the ACC is that it often is activated when people
feel sad. In fact, activity there is increased during the depressive phase of
some types of major depressive disorder. This kind of finding is interesting
because it indicates that neuroimaging studies may someday be useful in the task
of making diagnoses that are more specific than those made using current
descriptive methods. This, in turn, could lead to better selection of
treatments.
The third and final brain region described in the article is the
insula. The insula, like the ACC, is
activated during emotional recall tasks. Unlike the ACC, the insula is not
activated by viewing external cues, such as movies, with emotional content.
This finding has been duplicated in studies of non-human primates. It appears
that the insula is activated most strongly in response to aversive or
threat-related emotions. Some, but no all, studies showed a specific activation
of the insula in response to disgust. It is activated when the brain receives
visceral (primarily gastrointestinal) aversive sensations. the authors
speculate that the insula may be the center that is responsible for literal "gut
feelings."
The authors conclude that there is emerging evidence that some brain structures
are involved in specific emotional states, whereas others serve a more general
function of emotional processing. They are hopeful that these and future
studies will permit the understanding of the functional neuroanatomy of
emotion.
Sad
versus neutral. Recalling of powerful and personal autobiographical
emotional episodes invoking sadness versus recalling emotionally neutral life
episodes. WOEXP: 483.
Mario Pelletier; Alain Bouthillier; Johanne Levesque; Serge
Carrier; Claude Breault; Vincent Paquette; Boualem Mensour; Jean-Maxime Leroux;
Gilles Beaudoin; Pierre Bourgouin;
Mario
Beauregard. Separate neural circuits for primary emotions? Brain activity
during self-induced sadness and happiness in professional actors.
NeuroReport 14(8):1111-1116, 2003. PMID: 12821792.
DOI: 10.1097/01.wnr.0000075421.59944.69.
FMRIDCID: . WOBIB: 157.
Emotion - Sadness
Happy
versus neutral. Recalling of powerful and personal autobiographical
emotional episodes invoking happiness versus recalling emotionally neutral life
episodes. WOEXP: 484.
Mario Pelletier; Alain Bouthillier; Johanne Levesque; Serge
Carrier; Claude Breault; Vincent Paquette; Boualem Mensour; Jean-Maxime Leroux;
Gilles Beaudoin; Pierre Bourgouin;
Mario
Beauregard. Separate neural circuits for primary emotions? Brain activity
during self-induced sadness and happiness in professional actors.
NeuroReport 14(8):1111-1116, 2003. PMID: 12821792.
DOI: 10.1097/01.wnr.0000075421.59944.69.
FMRIDCID: . WOBIB: 157.
Emotion - Happiness