Chapter 4: Learning, Memory, and Language
Objectives
- I will be able to learn about learning and memory with the brain
- I will be able to learn about language and the brain
Learning and Memory
- The patient H.M. brought about a breakthrough in neurology about learning and memory
- H.M had severe seizures
- Traditional treatments did not work for him, so doctors did a surgery
- They removed the medial regions of temporal lobes (hippocampus, amygdala, that area)
- Surgery worked to relieve him of the seizures but left him with amnesia
- He was only able to remember recent events for a few minutes
- H.M. was unable to form explicit memories of new experiences
- However, H.M. could remember his childhood
- This shows the medial temporal lobe was critical in converting short-term memories to long-term ones
- The medial temporal lobe contains the hippocampus and parahippocampal region
- The medial temporal region is not the site of permanent storage but plays a role in the organization and permanent storage of memories somewhere else in the brain
- It’s closely connected to areas of the cerebral cortex including areas responsible for language & thinking
- It’s also crucial for forming, organizing, consolidating, and retrieving memory
- The cerebral cortex is important for long-term storage
Different Facets of Memory
- Declarative/explicit memory: the ability to learn and consciously remember facts and events
- A large network of areas in the cerebral cortex works with the hippocampus to support declarative memory
- This network plays a role in aspects of perception, movement, emotion, cognition
- All these areas contribute to declarative memory
- Incoming information first goes to working memory
- Working memory: a temporary form of declarative memory
- Working memory depends on the prefrontal cortex & other cerebral cortical areas
- Areas in the prefrontal cortex support executive functions like selection, rehearsal, and monitoring of information retrieved from long-term memory
- The prefrontal cortex interacts with a network of posterior cortical areas that encode, maintain, and retrieve types of information & where important events happened & more
- Semantic memory: a form of declarative knowledge that includes general facts and data
- Different cortical networks are specialized for processing kinds of information like faces, houses, tools, actions, language, etc.
- Episodic memories: personal experiences that occurred at a particular place and time
- The medial temporal lobe area serves a critical role in the initial processing and storage of these memories
- Different areas of the parahippocampal region play roles in processing “what”, ”where”, and “when” information about the event
- Hippocampus links these different elements
- These elements are then integrated back into various cortical areas responsible for each type of information
- The brain has multiple memory systems supported by different brain regions
- Non-declarative/Implicit/Procedural memory: the knowledge of how to do something
- This is expressed in skilled behavior and learned habits
- Procedural memory requires processing by basal ganglia and cerebellum
- The cerebellum is involved in motor tasks that involve coordinated timing
- The amygdala plays an important role in the emotional aspect of memory
- Expression of emotional memories involves the hypothalamus and sympathetic nervous system
- The brain processes different types of memories in different ways
Storing Memories
- Memory involves a persistent change in synapses
- Turning on certain genes may lead to modifications in neurons that change the strength and number of synapses
- This stabilizes new memories
- Researchers correlate specific chemical and structural changes in relevant cells with simple forms of memory in the sea slug Aplysia californica
- Long-term potentiation (LTP): a long-lasting increase in strength of synaptic response following stimulation
- Occurs prominently in the hippocampus, areas of the cerebral cortex, & other brain areas involved in forms of memory
- LTP happens due to changes in the strength of synapses at contacts involving N-methyl-d-aspartate (NMDA) receptors
- Molecular reactions to stabilize changes start:
- These reactions begin with the release of calcium ions into the synapse
- This activates a molecule called cyclic adenosine monophosphate (cAMP) in the postsynaptic neuron
- cAMP activates enzymes that increase the number of synaptic receptors & the CREB
- cAMP response element binding protein (CREB): activates genes that direct protein synthesis
- Neurotrophins: molecules that lead to growth in synapse and an increase in responsiveness when stimulated
- This cascade is essential to long-term memory
- There’s no single specific brain center storing memory
- memory is stored in distributed collections of cortical processing systems also involved in perception, processing, and analysis of learned material
- Each part of the brain contributes differently to permanent memory storage
Language
Damage to different regions in the left hemisphere produces aphasias
- Aphasia: a language disorder
Damage to the left frontal lobe can produce nonfluent aphasias
Nonfluent aphasia: aphasias where the individual loses the ability to produce speech or experiences great difficulty in producing speech
An important type of nonfluent aphasia is Broca’s aphasia
Broca’s aphasia: a syndrome in which
speech production abilities are impaired
speech output is slow and halting, requires effort, and often lacks complexity in word or sentence structure
Nonfluent aphasics still understand speech though structurally complex sentences may be poorly understood
Damage to the left temporal lobe can produce fluent aphasia
- Fluent aphasia: aphasias where the individual can still produce speech but that speech lacks any intelligible meaning
- An important type of fluent aphasia is Wernicke’s aphasia
- Wernicke’s aphasia:
- comprehension of speech is impaired
- speech output is of normal fluency and speed but is riddled with errors in sound and word selection
- tends to be gibberish
Damage to the superior temporal lobes in both hemispheres produces word deafness
- Word deafness: the inability to comprehend speech on any level
- However, individuals still have the ability to hear and identify the emotional quality of speech or gender of the speaker
It was once believed all aspects of language were governed by the left hemisphere only
- However, recognition of speech sounds and words involves both the left and right temporal lobes
Speech production is a left-dominant function that relies on frontal and temporal lobe areas
- Important for accessing appropriate words and speech sounds
Rare mutations of the FOXP2 gene impede learning to make sequences of mouth and jaw movements that are involved in speech
- Brings about difficulties that affect both spoken and written language
- FOXP2 gene codes for a protein that switches genes on and off in the brain
- Changes in this gene sequence may have been important for human evolution
The middle and inferior temporal lobes are involved with finding the meanings of words
The anterior temporal lobe may be a participant in sentence-level comprehension
The left posterior temporal lobe has a sensory-motor circuit that may help with systems for speech recognition and production to communicate
- This circuit is involved with speech development and is thought to support verbal short-term memory