Anxious brain
The emotional brain-Dalgleish
Fathers of affective neuroscience
Darwin(1872)
limited set of fundamental or basic emotions are present across species and cultures (including anger, fear, surprise and sadness)
animal emotions are homologues for human emotions
James(1884)
emotions are no more than the experience of sets of bodily changes that occur in response to emotive stimuli
Early neuroanatomical theories
The Cannon-Bard Theory
The Papez circuit
MacLean's Limbic system
many emotional expressions in humans are vestigial patterns of action
the bear example
Different patterns of bodily changes code different emotions
led to James-Lange theory of emotions
Criticism by Cannon
emphasis on the embodiment of emotion
bodily concomitants of emotions can alter their experienced intensity
Cannon's criticism of the James-Lange theory came from his investigations with Bard about the effects of brain lesions on emotional behavior of cats
Decorticated cats and "sham rage"
if emotions are the perception of bodily changes then they should be dependent on having intact sensory and motor cortices
They proposed that the fact that removal of the cortex did not eliminate emotions must mean that James and Lange were wrong
first theory of the brain mechanisms of emotions
hypothalamus is the brain region that is involved in the emotional response to stimuli
responses are inhibited by evolutionarily more recent neocortical regions
Removal of the cortex frees the hypothalamic circuit from top–down control, allowing uncontrolled emotion displays such as sham rage
A scheme for the central neural
circuitry of emotion
sensory input into the thalamus diverged into
upstream and downstream
The thought stream
transmitted from the thalamus to the sensory cortices and to the cingulate cortex
continues beyond the cingulate cortex to the hippocampus and to the hypothalamus and back to the anterior thalamus
sensations were turned into perceptions, thoughts and memories
The feeling stream
transmitted from the thalamus directly to the mammillary bodies
generation of emotions, and so via the anterior thalamus, upwards to the cingulate cortex
emotional experiences are a function of activity in the cingulate cortex and could be generated through either stream
Projections from the cingulate cortex to the hippocampus and then to the hypothalamus allows top–down cortical control of emotional responses
Elaborated on Papez's and Cannon and Bard's ideas and integrate them with the knowledge from Kluver and Bucy
bilateral removal of the temporal lobes in monkeys led to the Kluver-Bucy syndrome
loss of emotional reactivity
indicated a key role of the temporal lobe in emotion
Brain as 3 parts
The old mammalian brain (thalamus, hypothalamus, hippocampus, cingulate cortex, amygdala and the PFC)
The new mammalian brain (neocortex)
The evolutionary ancient reptilian brain (striatal complex and basal ganglia)
primitive emotions (e.g. fear and aggression)
augments primitive reptilian emotional responses and elaborates the social emotions
interfaces emotion with cognition and exerts top-down control over the emotional responses that are driven by other systems
MacLean’s essential idea
emotional experiences involve the integration of sensations from the world with information from the body
Proposed that events in the world lead to bodily changes
Messages are integrated by hippocampus with ongoing perception of the world
emotional experience
Limbic regions
Amygdala
PFC
ACC
Hypothalamus
social signals of emotions
Fear conditioning
Memory consolidation
Damage to amygdala
Kluver-Bucy signs
impairments in the processing of faces and other social signals
especially fearful faces
even when presenting quickly or having blindsight
no activation if attentional resources are recruited elsewhere
emotional processing in the amygdala is susceptible to top-down control
routes that mediate fear conditioning
direct thalamo-amygdala route
thalamo–cortico–amygdala pathway
process crude sensory aspects of incoming stimuli and directly relay this information to the amygdala,
allows more complex analysis of the incoming stimulus
allowing an early conditioned fear response
slower, conditioned emotional response
Lesions
immune to fear conditioning
Lesions
did not show the usual enhanced memory for
emotional aspects of stories
reward processing
learning the emotional and motivational value of stimuli
PFC regions work together with the amygdala to learn and represent relationships between new stimuli (secondary reinforcers) and primary reinforcers such as food, drink and sex
neurons in the PFC can detect changes or reversals in the reward value of learned stimuli and change their responses accordingly
bodily signals
modified version of the James-Lange approach proposes that bodily signals interact with other forms of information to modulate emotional intensity, rather than being the single determining factor
Similar patterns of bodily arousal can be experienced as anger or happiness depending on the social and cognitive context
somatic marker hypothesis
somatic markers
physiological reactions, such as shifts in autonomic nervous system activity, that tag previous emotionally significant events
Somatic markers provide a signal describing those current events that have had emotion-related consequences in the past
processed in VMPFC
allow decisions to be made in situations where a logical analysis of the available choices proves insufficient
top-down regulation
valence-asymmetry hypothesis
prefrontal regions send ‘bias signals’ to other parts of the brain to guide behavior towards the most adaptive current goal
PFC promotes adaptive goals in the face of strong competition from behavioral alternatives that are linked to immediate emotional consequences
PFC regions
left
involved in approach-related appetitive (positive) goals
right
involved in the maintenance of goals that require behavioral inhibition and withdrawal (negative)
point of integration of visceral, attentional and emotional information
crucially involved in the regulation of affect and other forms of top–down control
important role in approach and avoidance and fear learning
key substrate of conscious emotion experience and of the central representation of autonomic arousal
subdivision
dorsal ‘cognitive’ subdivision
rostral, ventral ‘affective’ subdivision
monitors conflict between the functional state of the organism and any new information that has potential affective or motivational consequences
When such conflicts are detected, the ACC projects information about the conflict to areas of the PFC where adjudications among response options can occur
electrical impulses in the hypothalamus can bring about a coordinated, sophisticated and recognizable emotional response
the response is not stereotyped but can be made in a skilfully targeted manner.
part of an extensive reward network in the brain, also involving the PFC, amygdala and ventral striatum
involved in motivations such as sex
and hunger
emotion systems
Single system models
Dual system models
same neural system underlies all emotions
Proposals of Cannon & Bard, Papez and MacLean and to some extent Damasio
propose a combination of some common brain systems across all emotions
the right-hemisphere hypothesis
emphasized a specialized role of the right hemisphere in all aspects of emotion processing
Davidson’s valence asymmetry model
Other dual system theorists have proposed that the emotions can be broken down into approach and withdrawal components
Like Schneirla
Rolls
dual-system approach that conceptualizes emotions in terms of states elicited by positive (rewarding) and negative (punishing) instrumental reinforcers, within a dimensional space
Multiple-system models
separable regions that are dedicated more closely to the processing of certain individual emotions such as fear, disgust and anger
studies that link fear to the amygdala or disgust to the anterior insular cortex