Emotion xox Flashcards
What are the 6 categories of emotion?
Anger
Fear
Surprise
Sadness
Joy
Disgust
What did Duchenne (1862) find out about emotion?
Used transcutaneous electrical stimulation (Faridization) to activate single muscles in the face, dorsal surface of the head, and neck, and documented the faces of his subjects with photography
He identified muscles that are not controlled by free will (not voluntary) but by emotions, including the obicularis oculi and zygomatic major
Made the distinction between a forced, volitional (pyramidal) smile and the spontaneous, emotional (Duchenne) smile.
Volitional movement = descending “pyramidal” and “extrapyramidal” projections from the motor cortes and brainstem –> voluntary facial paresis -> pyramidal smile
Neural systems for emotional expression = descending “extrapyramidal” projections from medial forebrain and hypothalamus –> emotional facial paresis -> Duchenne smile
What did Bard find in his study of cats and the hypothalamus?
Bard reported a series of experiments that pointed to the hypothalamus as a critical center for coordination of both the visceral and somatic motor components of emotional behavior
Bard removed both cerebral hemispheres in cats
The animals behaved as if they were enraged and angry behavior occurred spontaneously and included the usual AUTONOMIC correlates of this emotion: increased blood pressure and heart rate, retraction of the nictitating membranes and errection of the ahirs onthe back and tail and pupil dilation
Also exhibited SOMATIC motor components of anger, such as arching the back, extending the claws, lashing the tail, and snarling.
This behavior was called sham rage because it had no obvious target.
Bard showed that a complete response occurred as long as the caudal hypothalamus was intact
Sham rage could not be elicited, however, when the brain was transected at the junction of the hypothalamus and midbrain
Bard suggested that whereas the SUBJECTIVE experience of emotion might depend on an INTACT CEREBRAL CORTEX, the expression of coordinated emotional behaviors does not necessarily entail cortical processes.
What did Hess find in his examination of cats?
He showed that electrical stimulation of discrete sites in the hypothalamus of awake, freely moving cats could also lead to a rage response, and even to subsequent attack behavior.
Moreover, stimulation of other sites in the hypothalamus caused a defensive posture that resembled fear.
Together what do the findings of Bard and Hess tell us?
Their findings led to the conclusion that the basic circuits for organised behaviours accompanied by emotion are in the diencephalon and the brainstem structures connected to it.
Their work emphasised that the control of involuntary motor system is not entirely separable from the control of the voluntary pathways- this is important for the understanding of the motor aspects of emotions
What are the major targets of the hypothalamus?
Major targets lie in the reticular formation
Important circuits in the reticular formation control cardiovascular function, respiration, urination, vomiting, and swallowing.
The reticular neurons receive hypothalamic input from and feed into both somatic and autonomic effector systems in the brainstem and spinalcord.
Their activity can therefore produce widespread visceral motor and somatic motor responses, often overriding reflex functions and sometimes involving almost every organ in the body
In addition to the hypothalamus, other sources of descending projections from the forebrain to the brainstem reticular formation contribute to the expression of emotional behavior.
Collectively, these additional centers in the forebrain are considered part of the limbic system and arise outside the classic motor cortical areas in the posterior frontal lobe
The descending control of expression invovled two parallel systems that are anatomically and functionally distinct. What are they?
- The voluntary motor component comprises the classic motor areas of the posterior frontal lobe and related circuitry in the basal ganglia and cerebellum.
The descending pyramidal and extrapyramidal projections from the motor cortex and brainstem ultimately convey the impulses responsible for voluntary somatic movements. - cortical and subcortical structures in the medial frontal lobe and ventral parts of the forebrain, including related circuitry in the ventral part of the basal ganglia and hypothalamus, give rise to separate descending projections that run parallel to the pathways of the volitional motor system.
These descending projections of the medial and ventral forebrain terminate on visceral motor centers in the brainstem reticular formation, pre-ganglionic autonomic neurons, and certain somatic premotor and motor neuron pools that also receive projections from volitional motor centers.
The two types of facial paresis from Duchenne underscore this dual nature of descending motor control
What circuit provides the connections needed for emotional expression?
The Papez Circuit
Papez showed that the cingulate cortex and hypothalamus are interconnected via projections from the mammillary bodies (part of the posterior hypothalamus) to the anterior nucleus of the dorsal thalamus, which projects in turn to the cingulate gyrus. The cingulate gyrus (and many other cortical regionsas well) projects to the hippocampus. Finally, Papez showed that the hippocampus projects via the fornix (a large fiber bundle) back to the hypothalamus.
What forms the limbic system?
There are several important structures within the limbic system: the amygdala, hippocampus, thalamus, hypothalamus, basal ganglia, and cingulate gyrus.
Two especially important components of the limbic system not emphasized in early anatomical accounts are the orbital and medial prefrontal cortex and the amygdala
What is the amygdala?
Amygdala are grey-matter almond-shaped structures lying under the medial temporal lobe
The medial group of subnuclei has extensive connections with the olfactory bulb and the olfactory cortex.
The basolateral group has major connections with the cerebral cortex, especially the orbital and medial pre-frontal cortex of the frontal lobe and the associational cortex of the anterior temporal lobe.
The central and anterior group of nuclei is characterized by con-nections with the hypothalamus and brainstem, including such visceral sensory structures as the nucleus of the solitary tract and the parabrachial nucleus
The amygdala thus links cortical regions that process sensory information with hypothalamic and brainstem effector systems.
What is Kluver-Bucy syndrome and what does it tell us about the importance of the amygdala in emotion?
Kluver & Bucy removed large parts of the medial temporal lobe in rhesus monkey, and when they cut out the amygdala the monkeys developed Kluver-Bucy syndrome
Symptoms:
Visal agnosia
Increased oral tendancy
DECREASED EMOTIONAL REACTION
Hypersexuality and hypermetamorphosis
Monkeys became tame, and motor and vocal reactions generally associated with anger and fear were no longer elicited
Interruping the systems included in the Papez circuit has important effects on their emotional responses e.g. no longer scared of snakes
What did John Downer find when removing the amygdala in rhesus monkeys?
Downer removed one amygdala in rhesus mon-keys, at the same time transecting the optic chiasm and thecommissures that link the two hemispheres
Whenthe monkeys were allowed to see with the eye on the sideof amygdala lesion, they behaved in some respects likethose described by Klüver and Bucy
If they were allowed to see only with the eye on the side of the intact amygdala, they reverted to their usual fearful and aggressive behavior.
Thus, in the absence of the amygdala, a monkey does not interpret the significance of the visual stimulus presented by an approaching human inthe same way as a normal animal.
Importantly, only visual stimuli presented to the eye on the side of the ablation produced this abnormal state- if the animal was touched on either side, a full aggressive reaction occurred, implying that somatosensory information about both sides of the body had access to the remaining amygdala.
What is the role of the amygdala in fear conditioning? What did LeDoux find?
Conditioned fear response in rats- occurs when an initially neutral stimulus is repeatedly paired with an adverse one, over time animal responds to the neutral stimulus with behaviours elicited by threatemning stimuli
LeDoux found that it is difficult to unlearn conditioning
LeDoux worked out the neural circuitry that established the association between the tone and fear
First, they demonstrated that the medial geniculate complex (MGC) is necessary for the development of the conditioned fear response.
They went on to show, that the responses were still elicited if the connections between the MGC and auditory cortex were severed, leaving only a direct projection between the MGC and the basolateral group of nuclei in the amygdala.
Furthermore, if the part of the MGC that projects to the amygdala was also destroyed,the fear responses were abolished.
Subsequent work in LeDoux’s laboratory established that projections from the central group of nuclei in the amygdala to the midbrain reticular formation are critical in the expression of freezing behavior
Since the amygdala is a site where neural activity produced by both tones and shocks can be processed, the amygdala may also be the site where learning about fearful stimuli occurs.
This led to the broader hypothesis that the amygdala participates in establishing associations between neutral sensory stimuli
The finding that LTP occurs in the amygdala providese further support for this.
What can block the acquisiton of conditioned fear in the amygdala?
Infusion to the amygdala of NMDA-receptor antagonists, which prevents the induction of LTP or glutamatergic synapses
What is the role of the medial prefrontal cortex in unlearning fearful stimuli?
Projections back down from the medial prefrontal cortex, we get inputs from the medial prefrontal cortex and cogntive regions at the front of the brain and you need these projections to unlearn fear condioning, to habituate the fear conditioning and stop it
If we present the tone without the fearful stimulus, you unlearn that the tone produces the shock, ‘unlearn’ because we need the medial prefrontal cortex to do this, if we dont have the prefrontal cortex e.g., it dies away, then the fear conditioning becomes reinstated.
