4. Learning, Memory, and Emotions Flashcards
H.M.
Led to understanding that learning and memory are tied to biological processes. Following childhood blow to the head, developed seizures and underwent an experimental procedure that removed sections of his medial temporal lobes, including most of his hippocampi. Seizures abated, but was left with permanent amnesia. Could remember events before surgery, but was unable to form new memories
Now know that medial temporal lobe, which includes hippocampus and parahippocampal regions, works with other regions of cerebral cortex regarding memories
Declarative memory
Facts, data, events. Explicit because you consciously recall and describe the information. Semantic or episodic
Semantic memory
Cultural knowledge, ideas, and concepts accumulated about the world. E.g., names of capitals, vocabulary, how to add, dates of historical events. Involves cortical regions beyond hippocampus
Episodic memory
Personal experiences
What brain region mediates emotional significance attached to memories of events?
Amygdala
How is the “what” of episodic memories encoded?
Parahippocampal region aids hippocampus
Semantic and episodic memory are examples of what form of declarative memory?
Long-term
Did H.M. struggle with long-term declarative memory, and why or why not?
He did not, because it is stored throughout a large network of cortical areas
Working memory
Short-term declarative memory
Brain’s capacity for long-term vs short-term memories
Brain seems to possess unlimited capacity for long-term memory, but short-term memories are limited to small amounts of information for small periods of time. Accessible while being processed and manipulated, but unless transferred to long-term memory, will decay after a few seconds
Did H.M. struggle with working memory, and why or why not?
He did not, because it is coordinated by the PFC
Spatial memory - neural basis
Navigational memories involved in creating mental maps are tied to place cells in the hippocampus. Grid cells, located in entorhinal cortex (area near hippocampus), represent coordinates that allow the brain to track your position in space
Nondeclarative memory
Implicit/procedural memory. Stored and retrieved without conscious effort. Used when performing learned motor skills.
Did H.M. struggle with nondeclarative memory, and why or why not?
Did not lose this type of memory, still able to acquire new motor skills despite not being able to remember doing them before
3 important brain areas to nondeclarative memory
Basal ganglia (“habit centre”), PFC, and cerebellum (involved in motor control and coordination)
Why can the brain form memories and rewire itself in response to experience?
Because neural circuits change at synapses
Synaptic plasticity
Ability of synapses to remodel themselves
Encoding a long-term memory involves…
Persistent changes in the number and shape of synapses, the amount of neurotransmitter released, and the number of receptors
What animal was used to study synaptic plasticity, and why?
Sea slug, Aplysia californica, because its nerve cells are relatively few and easy to observe
Two molecular components critical to the formation of long-term memories
Genes governing NMDA receptors (type of glutamate receptor) and cAMP-response element binding protein (CREB)
Two processes key for synaptic plasticity
Long-term potentiation and long-term depression
Long-term potentiation
Long-lasting increase in synaptic strength. Occurs in many areas but especially in hippocampus. Involves increase in glutamate receptors. Once glutamate is bound, calcium and sodium ions flow into cell. Increasing receptors strengthens a synapse by allowing the entry of more ions
Long-term depression
Decreases a synapse’s effectiveness
Effects of LTP and LTD on calcium ion concentration inside post-synaptic cell
LTP boosts concentration of calcium ions inside a postsynaptic cell, LTD increases it to a lesser degree.
Enzymes activated by differences in calcium ion concentration in LTP and LTD
Kinase proteins in LTP, phosphatases for LTD. These enzymes modify synapses, making them more or less efficient
Series of events in LTP that stabilizes synaptic changes
Increase in calcium ions activates cAMP molecules, which activates different enzymes, some of which increase the number of receptors, making the synapse more sensitive. Continued stimulation through repetitive experience activates CREB, which acts in the nucleus of the neuron to switch on genes that direct protein synthesis. Among proteins produced are neurotrophins, which stimulate growth of synapse and structural elements, stabilizing increased sensitivity of synapses
Stabilizing of synaptic changes in LTP is critical for…
Memories becoming long-term
Where are declarative memories encoded?
Hippocampus
Where are declarative memories transferred for long-term storage and consolidation?
Frontal lobes. Over time, hippocampus becomes less important for retrieving older memories as frontal cortex assumes that task
Emotional memory
Nondeclarative memory. Learned emotional responses become attached to stimuli over time
Who identified 6 basic emotions, and what are they?
Paul Ekman; anger, fear, surprise, disgust, joy, and sadness
Structures most closely linked to emotions
Amygdala, insular cortex, periaqueductal grey. Neurons from PFC, amygdala, and insular cortex project to periaqueductal gray, which has connections with amygdala, thalamus, hypothalamus, brainstem, and spinal cord
Role of amygdala in emotion
Integrates emotions and motivation. Interprets fear. Identifies social rewards and how to attain them. Classical conditioning (association of stimulus with reward or punishment) is dependent on amygdala
Role of insula in emotion
Responsible for disgust. Implicated in feeling and anticipating pain. Takes in system-wide inputs and generates subjective feelings about them.
Role of periaqueductal grey in emotion
Tied to pain perception and stress responses. Located where incoming sensory information is acted on by higher brain centres. Receptors for pain-reducing compounds like opioids are clustered in periaqueductal gray
Affective decision making
Making choices under risky conditions. Teens make more risky decisions because PFC isn’t fully developed yet. Older adults also make more risky decisions because PFC function diminishes with age
Why do we remember rewarding things?
Dopamine influences synapses in reward pathway (hippocampus, amygdala, PFC) to create emotional associations with rewards
Reward pathway
Mesolimbic pathway. Connects ventral tegmental area (VTA) to nucleus accumbens.
Is it the reward or the expectation of a reward that most powerfully influences emotional reaction?
Expectation. Reward learning occurs in response to an unexpected reward. If a reward is greater than anticipated, dopamine signalling increases. If less, it decreases. Correctly predicted reward doesn’t change anything.
Go-getters have…
Greater dopamine signalling in striatum and PFC
2 examples of abnormal circuitry in reward system leading to inappropriate aggression
Lateral habenula, major node in reward circuitry, encodes punishment by inhibiting dopamine release. Dysfunction linked to inappropriate aggression.
Stimulating amygdala triggers rage and aggression. Removing parts of it makes animals more docile.
