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