The Limbic System Flashcards
1
Q
What are emotions?
A
- A natural instinctive state of mind derived from one’s circumstances, mood, or relationships with others
- Generated in response to: stimuli (seeing a snake), thought (thinking of your friends / family), or action (eating your favourite food)
- No known single emotion system
- Emotions can be both a cause of a motivated behaviour or an effect of a motivated behaviour
2
Q
What are emotional memories?
A
- Involves associating stimuli, thoughts, or responses with specific emotional outcomes
- Amygdala involved: stamps memories into LTM – things with strong emotional components are stored as memories
3
Q
What are the 4 components of emotions?
A
- Behaviour
- Physiology
- Feeling
- Awareness
4
Q
Explain the role of emotional memories in motivated behaviour.
A
- Motivated behaviours (e.g., eating, sex) can generate emotions
- We are motivated to obtain positive emotions and to avoid negative emotions
- Motivated behaviour can generate a rise in dopamine from the mesolithic DA pathway, which creates emotion. The amygdala then associates rises in DA with the memory of the stimulus and/or action. Emotional associations are then made with those behaviours.
- Emotions can also drive motivated behaviours. Memories make you more or less likely to repeat a particular behaviour.
5
Q
What are the two components of an emotion?
A
- Physiological response to a stimulus: CNS involved in changes in attention, memory processing, decision making. PNS is involved in visceral nervous system activation, endocrine responses, GI changes, heart rate, musculoskeletal responses.
- Conscious feelings in response to stimuli: Perception of physiological change
- Physiological and psychological components can often (but not always) occur together
6
Q
What is the James-Lange theory of emotion?
A
- Stimulus occurs
- Physiological change in response
- Body reacts to sensory input without any emotional context
- Emotions are the reaction to physiological changes
- At the time, most people thought the opposite (that physiological changes were the response to an emotional reaction)
7
Q
Why were Cannon and Bard critical of the James-Lange theory of emotion?
A
- Emotional experience can occur independently of emotional expression (sensory input). Subjects with severed spinal cords who had no sensory inputs could still show emotions (however, emotions were diminished). Therefore, emotions can occur in the absence of physiological changes.
- Inconsistencies in the correlation between physiological changes and emotional experience: physiological response seen in fear is identical to that seen in anger, illness, etc.
8
Q
What is the Cannon-Bard theory of emotion?
A
- Emotions are produced by activating (directly or indirectly) the thalamus, irrespective of physiological changes
- Type of emotion is determined by specific pattern of activation in the thalamus
- Thalamus relays sensory information to the hypothalamus and cortex
- The cortex produces conscious feelings of emotions while the hypothalamus produces behavioural responses through connections with the brainstem
9
Q
Explain Cannon and Bard’s ‘sham rage’ experiment with cats.
A
- Removed cerebral hemispheres (cortex, white matter, and BG) in cats
- Pre-surgery, cats were friendly. However, when the anesthesia wore off, the cats were behaviourally enraged. They demonstrated increased blood pressure, heart rate, piloerection, arching of back, snarling, etc.
- ‘Sham rage’ because there was no target / reason for the rage
- Severed cat brain either above or below the hypothalamus. If severed below the hypothalamus, it eliminated the rage response. If severed above the hypothalamus, it did not prevent the display of rage.
- Suggests that the hypothalamus is critical centre for coordination of expressing both visceral and somatic motor components of emotional behaviour
- However, subjective experience of emotion might be different
10
Q
Explain the study that investigated whether emotions are a reflex to motor activity.
A
- Individuals were given muscle by muscle instructions of cranial muscles that resulted in “emotional” facial expressions
- Subjects were not told which emotion they were re-enacting
- Each pattern of facial muscle activity was accompanied by specific and reproducible differences in visceral motor activity (heart rate, skin conductance, skin temperature, etc.)
- Suggested that a major source of emotion is actually feedback from muscles and internal organs. Also identified muscles and muscle groups that were not under conscious control but that were recruited following emotional stimuli.
11
Q
How did Paul Broca originally define the limbic lobe?
A
- Cortex around the corpus callosum (cingulate gyrus)
- Cortex on the medial surface of the temporal lobe
- Hippocampus
- Connects sensations to behavioural responses
12
Q
Who was Phineas Gage?
A
- One of the first cases that linked brain structures to emotional regulation
- Tamping iron entered under left eye, passed through the left frontal lobe, and exited the top of his head
- Experienced damage to the cerebral cortex in both hemispheres, particularly to the frontal lobe
- Recovered, but personality was drastically and permanently changed: He became fitful, irreverent, and used profane language. Also impatient, irrational, and irregular thoughts.
- Lived for 12 years after injury
13
Q
What are the 5 structures included in the Paper circuit?
A
- Cortex: involved in conscious experience of emotion. Emotion required cognitive function. Sensory input from the thalamus to the cortex does not carry any emotional salience (required for being aware, but needs integration with the hypothalamus).
- Neocortical structures: Provide “emotional colouring” to experiences. They can separate different types of emotions and subcategories of emotions.
- Cingulate cortex: Lies dorsal to the CC and is primarily responsible for activating neocortex. It integrates inputs from the hypothalamus and sensory cortex and associates the identity of a stimulus with emotional salience.
- Parahippocampal gyrus: Lies in medial temporal lobe. Thought it was involved because rabies patients showed misfolded proteins in the cytoplasm of hippocampal neurons.
- Hypothalamus: Governs behavioural expression of emotion.
14
Q
Explain the finer tracts that connect the structures in the Paper circuit.
A
- Fornix is the large bundle of fibres that leaves the hippocampus and connects to the hypothalamus
- Mammillary bodies of the posterior hypothalamus connect to the anterior thalamus, which projects to the cingulate cortex
- Cingulate cortex and other cortical regions project directly to the hippocampus
- Bidirectional flow of information: supports both the James-Lange and Cannon-Bard theories
15
Q
How has the Papez circuit been revised? What structures have been added and excluded?
A
- Now includes:
1) orbital and medial PFC
2) ventral BG
3) mediodorsal nucleus of thalamus
4) amygdala - Hippocampus, parahippocampal gyrus, mammillary bodies, and anterior nucleus of thalamus no longer considered important
