NSC 4354 Lecture 22_ Emotion.docx

NSC 4354 Lecture 22: Emotion Textbook: pg, 703; Chapter 31 Aims What pathways are involved in emotions? What is the role of the hypothalamus? What are the functional connections of the hypothalamus? What is the role of the prefrontal cortex, basal ganglia, and amygdala in emotions? Notes:...

NSC 4354 Lecture 22: Emotion Textbook: pg, 703; Chapter 31 Aims What pathways are involved in emotions? What is the role of the hypothalamus? What are the functional connections of the hypothalamus? What is the role of the prefrontal cortex, basal ganglia, and amygdala in emotions? Notes: Emotions as a subjective feeling (703) Emotions are expressed via the “emotional motor system”: Visceral motor changes Involve activation of sympathetic ANS (fight or flight) Somatic motor responses (facial expression) Recruited LMNs Subjective “feeling” The limbic system, amygdala, cortical regions 2 ANS Subdivisions Sympathetic: mobilizes body’s resources Parasympathetic: restore previously expended resources The face of emotion: “fear” The pupils dilate. Hair stands on end. Blood in wounds coagulates. Air intake increases. Bronchioles relax, and more oxygen enters the lungs. Blood pressure rises. Muscles contract. Blood vessels near the surface of the skin contract, causing the skin to pale. Other blood vessels dilate, and the liver releases glucose, providing fuel for muscles. The bladder empties stored urine in cases of extreme fear. Measuring physiological variables associated with emotion Skin conductance (704) Lie detector (polygraph) test Index of sweating measured by electrodes on the palmar surface of the hands/feet Fear and anxiety are linked to high arousal-states What are the functions of emotions? Prepare the body for action Communicate our emotional states to other people Identify favorable and unfavorable outcomes Instantiate healthy behaviors Eating, drinking, sex, caregiving/pro-social Unless it is extreme, arousal enhances intellectual and physical performance Hypothalamus: Critical Center for Integration Philip Bard (1928) removed cerebral hemispheres (front half of brain) in cats, which elicited spontaneous rage he termed ‘sham rage’ → No obvious target (705) Cerebral cortex was cut out Altered visceral motor component = increased blood pressure and heart rate, pupil dilation, piloerection of hairs Altered somatic motor component = arched back, extended claws, tail lashing, snarling ‘Sham rage’ only occurred if the hypothalamus was intact No ‘sham rage’ if the hypothalamus was completely removed “Uninhibited hypothalamic discharge” has 3 known causes in humans: Hypothalamic lesions Carbon monoxide poisoning Hypoglycemia (low blood sugar level) The experience of emotion may depend on the cerebral cortex, but the expression of emotion depends on the connection between the hypothalamus and brainstem Hypothalamus: Critical Emotive Center (705) Walter Hess (Nobel Prize in 1949) Electrical stimulation of parts of the hypothalamus also leads to rage responses and attack behavior Stimulation of other sites of the hypothalamus caused a defensive posture resembling fear Hypothalamus The hypothalamus coordinates the peripheral expression of emotional states Hypothalamus: Where does it project? Hypothalamic projections that influence visceral and somatic motor systems are complex The reticular formation is a major target involved in: Alertness Cardiovascular function Respiration Urination Vomiting Swallowing Reticular formation output to (705): Brainstem and spinal cord Somatic motor Visceral motor Reticular neurons receive hypothalamic input from and feed into both somatic and autonomic effector systems in the brainstem and spinal cord. Multiple motor systems regulate facial expressions Duchenne de Boulogne, 1862 Contrive, voluntary smile “Pyramidal smile” → Motor cortex via pyramidal tract Spontaneous, emotional smile “Duchenne smile” → Anterior cingulate via reticular formation The lesion in descending projection from the motor cortex: Difficulty in producing voluntary movement/ smile The lesion in the extrapyramidal motor pathway: inability to produce an “emotional” smile The limbic lobe 1850s: Paul Broca used the term limbic lobe to refer to the part of the cerebral cortex that forms a rim around the corpus callosum Two prominent components: Cingulate gyrus Parahippocampal gyrus Papez circuit = cortical control of emotional expression (709) Hippocampal fibers project to the Mammillary bodies of the hypothalamus project through the Mammillothalamic tract to the The anterior thalamic nucleus projects to the Cingulate gyrus projects back to the Hippocampal formation projects via Fornix bundle back to the hypothalamus Modern conception of the limbic system (708) The concept of a forebrain circuit has been revised over time to include: Amygdala Parts of the orbital and medial prefrontal cortex Ventral parts of the basal ganglia The mediodorsal nucleus of the thalamus Limbic System – Klüver–Bucy syndrome Klüver–Bucy syndrome is a syndrome resulting from bilateral lesions of the medial temporal lobe Later demonstrated that it can be elicited by the removal of the amygdala alone Visual agnosia: Inability to recognize familiar objects or people Docility and decreased emotional reactions: Diminished fear responses or reactions with unusually low aggression No longer viewed scientists as threatening Dietary changes and/or Hyperphagia: Eating inappropriate objects and/or overeating Hyperorality: "an oral tendency, or compulsion to examine objects by mouth" Hypersexuality: Heightened sex drive or a tendency to seek sexual stimulation from unusual or inappropriate objects The amygdala (710) The amygdala links cortical sensory regions with the hypothalamus and brainstem There are 3 major functional and anatomical subdivisions: Central (CeA) = connections with hypothalamus and brainstem (expression of emotion) Medial (MeA) = extensive connections with olfacy bulb and cortex Basolateral (BLA) = major connections with orbital/medial prefrontal cortex, associational cortex of anterior temporal lobe (sensory convergence, emotional significance) The amygdala plays an important role in mediating emotional behavior and motivation → evaluates the emotional value of sensory stimuli Amygdala Assigns Emotional Significance John Downer, 1950s Unilateral lesion of amygdala AND transection of the optic chiasm and corpus callosum and anterior commissure → Produce monkeys with single amygdala with access to only the visual input from the ipsilateral eye Monkeys that could see only with an eye on the same side of the amygdala lesion → Docile similar to Kluver-Bucy syndrome Monkeys that could see only with an eye on the side of the intact amygdala = reverted back to normal fearful and often aggressive behavior Thus, in the absence of the amygdala, a monkey does not interpret the significance of the visual stimulus presented (approaching human) Applies only to visual information (touching induces a full aggressive behavior) The amygdala mediates neural processes that invest sensory experience with emotional significance Amygdala and learning (712) The amygdala is involved in the association of neutral stimuli with primary reinforcers (positive and negative) → associative learning Fear and the Human Amygdala (713-714) Patient S.M. suffers from a rare condition called Urbach-Wiethe disease Bilateral calcification and atrophy of the anterior-medial temporal lobes, including the amygdala Asked to rate intensity of emotion in photographs Cannot recognize the emotion of fear Patient S.M. encounters with snakes, spiders, haunted house, scary movies = no fear No self reports of fear in daily life over 3 months, all other emotions reported Modern conception of the Limbic System Parts of the orbital and medial prefrontal cortex Phineas Gage 1848 case study of brain and personality change Damage to the ventromedial prefrontal cortex produced erratic behavior demonstrating that activity in the (ventral) orbitofrontal cortex provides inhibitory control over behavior (impulse control) Patients often show no reaction to emotional events, and are unable to make personal or social decisions → “acquired sociopathy”. Affective Disorders (715) Depression, the most common of the major psychiatric disorders, has a lifetime incidence of 10% – 25% in women and 5% – 12% in men. Major depressive disorder and bipolar disorder Abnormal sense of sadness (or mania) Profound despair Inappropriate guilt Excessive thoughts of death Neurobiological disease: genetic disposition and evidence in neuroimaging studies Abnormal blood flow in the amygdala, and prefrontal cortex Correlation between amygdala blood flow and severity of depression Depression abated = normal blood flow in the prefrontal cortex Modern Conception of the Limbic System Ventral parts of the basal ganglia The mediodorsal nucleus of the thalamus Limbic Loop through the basal ganglia Most drugs of abuse influence dopamine in amygdala-basal ganglia connectivity = limbic loop through basal ganglia Nucleus accumbens (NAcc) under dopaminergic modulation from the ventral tegmental area (VTA) Activation causes rewarding effects/emotional reinforcement (food, water, sex, social rewards) Dysregulation when exposed to drugs of abuse Associative learning: DA in VTA The activity of VTA dopamine neurons starts signaling the presence of the reward-predicting stimulus instead of the reward Summed recordings from an awake monkey A: Presentation of unexpected juice reward = burst of activity (shaded area) B: Learning trials = neurons fire to visual or auditory cues before the reward C: Cue presented without reward = VTA neurons suppressed at the same time reward would have been received (lightly shaded area) Phasic release of DA signals the presence of reward to NAcc, prefrontal cortex, and amygdala Lateralization of emotions (716) Lateralization of emotions The left hemisphere more involved with positive emotions Right hemisphere more involved with negative emotions Humans more quickly express positive emotion with left facial muscles (controlled by the right hemisphere) Posttraumatic stress disorder (PTSD) (721) PTSD emerges after exposure to a traumatic stressor It is estimated that 50% of people will have a traumatic experience in their lifetime 5% of men & 9% of women will develop PTSD as a result Symptoms: persistently re-experiencing the traumatic event, avoiding reminders of the event, numbed responsiveness, and heightened arousal lOften accompanied by depression & substance abuse, which complicates treatment & recovery Treatment: Cognitive-behavioral therapies and antianxiety/antidepressant medications There is no cure Can persist for decades Questions Electrical stimulation of which brain structures has been shown experimentally to elicit sham rage in a cat? Hypothalamus Patient S.M., who suffered selective bilateral damage to the amygdala , exhibited