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