BIOLOGY

WHAT IS EMOTION? Characteristics Accompanied by both physiological and cognitive changes “Valenced” – either positive or negative Influence behaviour

Components physiological reactions expressions of emotion cognitions and subjective emotion social influences

Autonomic Nervous System (ANS) Sympathetic nervous system (SNS) – “Fight or flight” response Parasympathetic nervous system (PNS)

Sympathetic Nervous System (SNS) Supplies glucose and oxygen to skeletal muscles Heart rate increases during sympathetic activation as does breathing rate and bronchiole expansion Peripheral vasoconstriction; arterial constriction and increased heart rate lead to higher blood pressure; peristalsis reduced

Parasympathetic Nervous System (PNS) Opposite effect Heart rate slows Bronchiole constriction Facilitation of digestion

Sympathetic and parasympathetic nervous systems work together like two rheostats Both systems always on but they will vary in their strength/weakness Two systems work together to manage the state of the body ANS relies on neurons for activation

Hormones also play important role e.g. adrenaline (epinephrine), cortisol an oestrogen Change in level, as opposed to the absolute level itself, of some hormones is instrumental in mood change e.g. oestrogen (Payne, 2003)

Brain structures The Papez circuit (Papez, 1937) – centred around the hippocampus - emotional expression and emotional feeling Papez circuit later became the limbic system (MacLean, 1952), implicating the septum and the amygdala

Limbic system (paleopallium brain) Emotions and instincts, feeding, fighting, fleeing, sexual behaviour Limbic system includes: –amygdala –dentate gyrus –cingulate gyrus –hippocampus –orbitofrontal cortex –and other structures

Limbic system (paleopallium brain) Amygdala – emotion generation Cingulate gyrus – accessing emotional memories anterior cingulate cortex – attention to emotional stimuli Hippocampus – consolidation of emotional memories from short- to long-term storage Orbitofrontal cortex representation of emotion in decision-making

Amygdala Almond-shaped cluster of neurons near base of brain Bilateral – one in each hemisphere Input from the senses Stores memories of fearful stimuli and triggers fear responses Fast "low road" from thalamus to amygdala, Slower "high road" from thalamus to neocortex

Amygdala Amygdala damage implied in having difficult naming facial expressions (Boucsein et al, 2001) Amygdala responds strongly to sadness expression (fMRI studies) (Wang et al, 2005) Amygdala responds strongly to happy expressions only in extraverts (Canli et al, 2002)

Low road may respond to long, thin object as dangerous snake, and trigger fear response, while slower high road determines that object is harmless stick "We know that lots of people have fears that they can't come to conscious terms with, people who have pathological fears may be treating sticks as snakes all the time, metaphorically." LeDoux (2002) (p.40)

Kluver-Bucy Syndrome Evidence for the role of the limbic system in emotional behaviour Kluver and Bucy bilaterally removed temporal lobes (including amygdala) of Rhesus monkeys Found normally aggressive animals became docile and exhibited odd behaviours

“Psychic blindness”- inability to recognize objects Indiscriminate eating patterns Place objects in their mouth to recognise the object

Compulsion to examine things (touch everything) Hypermetamorphosis (grabbing any object within reach and throwing or shredding it) Decrease in fear

The amygdala and fear Electrical stimulation of amygdala in animals produces behaviour associated with fear In humans, stimulation of amygdala can result in verbal reports of fear and anxiety, or terrified screaming Experiments using classical conditioning of fear found that the amygdala responds to the conditioned stimuli after pairing of UCS and US (Kapp et al, 1979;1984)

Frontal Lobes One third of human cerebral cortex Bi-directional connections with thalamus and amygdala Genesis and expression of affective states

The prefrontal cortex (PFC) Planning, working memory and decision making Appropriate decisions use emotional data (Damasio, 1994) Experience of emotion: –Dorsolateral – attending to stimulus –Ventromedial – emotion language –orbitofrontal PFC – filters sensory information

The prefrontal cortex (PFC) Damage to PFC leads to flat emotion and poor decision making (Damasio, 1994) and reduced empathy levels (Shamay-Tsoory et al, 2004) Damage to left PFC, but not equivalent areas of right PFC, increases likelihood of depressive symptoms Positive emotional stimuli increase activity in left PFC; negative stimuli increase activation of right PFC

The prefrontal cortex (PFC) Lesions to ventromedial PFC result in failure to anticipate positive or negative consequences of actions Lesions to orbitofrontal PFC reduce inhibition of behaviour and impairs ability to translate judgements about events into appropriate feelings and behaviours

The case of Phineas Gage Head injury Personality change Damasio et al (1994) used imaging to determine that frontal lobes of both hemispheres damaged particularly left orbitofrontal cortex

Frontal lobe surgery Frontal lesion produced calming effect in chimpanzee Moniz and Lima’s leucotomy procedure –Holes were drilled in patient's skull on either side Flat wire knife inserted through each hole

Frontal lobe surgery Moniz recommended that leucotomy only be used as last resort in cases regarded as otherwise hopeless In 1949, Moniz received Nobel prize for his work (Moniz no longer practised surgery as he had been shot in the spine and permanently paralyzed by one of his ex-patients)

The case of HM Henry Molaison (d. 2009) 1953 temporal medial resection –Hippocampi, parahippocampal gyri and amygdala removed –Anterograde amnesia –Could encode but not store or retrieve new emotional memories –Ongoing debate re role of amygdala and temporal medial lobe in emotion memory