29- Emotion

Question 1

define emotion

Answer 1

feelings we experience; mental states brought on by neurophysiological changes

Question 2

outline the theories regarding the neural basis of emotion

Answer 2

James-Lange theory = emotions arise as a result of a physiological response to stimuli - e.g. you cry so you feel sad. one-to-one correspondence between an emotion and reaction

Cannon-Bard theory = as a result of thalamic activity, emotional reactions and physiological responses can occur simultaneously but independently. doesn’t limit a physiological reaction to a specific emotion

both theories are compatible for Papez circuitry

Question 3

describe the Papez circuitry and the limbic system

Answer 3

Papez circuitry - limbic system structures involved in emotional processing and the emotional experience

brain experiences an emotional stimulus

signal to neocortex for emotional colouring

signal to cingulate cortex for emotional experience

signal to hippocampus - important in connecting specific emotions to memories

to hypothalamus via fornix (bundle of axons) = neuroendocrine and autonomic NS responses

hypothalamus sends signal to anterior nuclei of thalamus, signal back to cingulate cortex in a cycle - emotional experience elicited by cingulate cortex stimulates emotional reaction by hypothalamus and vice versa

lesions in the Papez circuitry = defects in emotional processing

Question 4

describe Broca’s limbic lobe

Answer 4

structures that surround the corpus callosum in a ring, involved in emotional processing

• cingulate gyrus = emotional experience
• parahippocampal gyrus and hippocampus
• medial surface of temporal lobe

Question 5

list structures of the limbic system

Answer 5

cingulate gyrus = emotional experience

amygdala = emotional processing and learning, contains three nuclei involved especially in fear, anxiety and aggression

parahippocampal gyrus and hippocampus proper = connects emotions to memories

hippocampal cortex = CA1-4 subfields, subiculum and dental gyrus

Question 6

describe the structure and role of the amygdala

Answer 6

almond-like structure next to the hippocampus, important in fear, aggression and anxiety

consists of three nuclei with different roles in mediating emotion - basolateral, central and corticomedial

basolateral = receives input from neocortex, processes emotional colouring

central = receives info. from sensory systems

corticomedial = sends output of amygdala to hypothalamus
- involved in two pathways: stria terminalis and ventral amygdalofugal pathway

Question 7

effects of lesions (Kluver-Bucy syndrome) or removal of the amygdala (amygdalectomy)

Answer 7

oral tendencies

hypersexuality

reduced ability to recognise fearful expressions

reduced fear and aggression

visual agnosia

Question 8

what is Kluver-Bucy syndrome?

Answer 8

rare neuropsychiatric disorder of lesions affecting the temporal lobes/ hippocampus and amygdala

causes changes in behaviour - oral tendencies, hypersexuality, visual agnosia, reduced fear

Question 9

the role of the amygdala in fear

Answer 9

involved in forming memories of emotional and painful events - hyperactivity and sensitivity linked to learned fears and PTSD

stimuli activates auditory and somatosensory cortexes

signal sent to basolateral nucleus of amygdala, to central nucleus

induces neuroplasticity through:
- hypothalamus = autonomic response
- PAG grey matter of brainstem = behavioural response
- cerebral cortex = emotional experience

Question 10

the role of the amygdala in aggression

Answer 10

neural mechanism:

stimulus > cerebral cortex > amygdala projections to:
- hypothalamus
- VTA via the medial forebrain bundle = predatory aggression
- PAG in brainstem via dorsal longitudinal fasciculus = affective aggression

removal of the amygdala reduces aggressive behaviour and relieves anxiety

animals experience change from dominance to subordinance - removes the need for social hierarchy

Question 11

key experiments which helped us understand the neural basis of emotions

Answer 11

removing regions of the hypothalamus affects sham rage

cerebral cortex and anterior hypothalamus removal = sham rage

no sham rage when the posterior hypothalamus is removed = important in aggressive behaviour

Question 12

describe aggression

Answer 12

aggression is multifaceted - controlled by endocrine mechanisms with increased testosterone, and different neural mechanism for different types of aggression

two types of aggression:

1. affective aggression = for showing social dominance, threatening. vocalisation and increased sympathetic activity.
2. predatory aggression = for killing or attacking prey. no vocalisation or sympathetic activity