Brain Plasticity and Memory

• Learning objectives include understanding brain plasticity and how the brain changes
• Learning objectives also include analyzing factors like age, environment, and cognitive activities, as they influence brain plasticity
• Learning objectives also cover exploring encoding, storing, and retrieving memories
• Learning objectives also involve the role of consolidation and retreival cues in memory
• Learning objectives also highlight identifying forms of amnesia and their causes
• Learning alters neural connections due to experience, learning, and injury
• Brain plasticity is influenced by age, environment, and cognitive activities throughout life.
• Memory processes involve encoding, storing, and retrieving information, with the crucial roles of consolidation and retrieval cues
• Forms of amnesia include anterograde and retrograde, caused by brain injury, disease, or psychological trauma

Learning

• Relatively permanent changes in behavior occur due to training, practice, or experience
• Learning is also how experience changes the brain
• Learning is the process of acquiring knowledge about the world
• Learning results in more or less permanent changes in behavior from practice

Stages of Learning

• Acquiring involves mastering a new activity
• Retaining is keeping the new acquisition for a period of time
• Remembering enables the reproduction of learned acts or memorized material
• Memory is a phase of learning

Memory

• Changes are stored and subsequently reactive
• Knowledge gets encoded, stored, and later retrieved

Categories of Memory

• Sensory Memory: Awareness of briefly presented information and perception of its aftereffects
• Echoic Memory: Auditory stimuli stored for a few seconds; necessary for comprehending sounds
• Iconic Memory: Visual representation of information in the environment
• Short-term Memory: Retains small amounts of information for a few seconds or less than 30 seconds
• Long-term Memory: Mental storage of knowledge and experiences for a relatively permanent period

Long-Term Memory (LTM) Categories

• Declarative Memory: Holds information that is easily verbalized and described i.e. names, concepts, events, and experiences
  • Semantic memory is a sub-type
  • Episodic memory is a sub-type
• Procedural Memory: Holds relatively permanent information that is not easily verbalized
• Explicit Memory: Knowledge of facts, people, places, and the meanings of these facts; Conscious memory
• Implicit Memory: Involves information on how to perform something; Recalled unconsciously; Used in trained, reflexive motor or perceptual skills

Memory Storage in the Brain

• Memory is stored diffusely throughout the structures of the brain
• Five areas implicated in memory storage:
  • Inferotemporal Cortex
  • Amygdala
  • Prefrontal Cortex
  • Cerebellum
  • Striatum

Brain Regions and Their Role in Memory

• Inferotemporal Cortex: Involved in the visual perception of objects; participates in storing memories of visual patterns. It is the cortex of the inferior temporal lobe
• Amygdala: Almond-shaped nucleus in the anterior temporal lobe; a role in memory for the emotional significance of experiences
• Prefrontal Cortex: Composed of many anatomically distinct areas with different connections and functions; regions perform fundamental cognitive processes during working memory tasks; involved in memory for the temporal order of events
• Cerebellum: Stores memories of learned sensorimotor skills
• Striatum: Stores memories for consistent relationships between stimuli and responses; the type of memories that develop incrementally over many trials

Hippocampus and Spatial Memory

• The hippocampus is part of the limbic system
• The limbic system is composed of brain structures impacting emotion and motivation
• The hippocampus and surrounding structures play crucial roles in the encoding and retrieval of memories

Spatial Ability

• Ability to visualize rotation and flipping of shapes and diagrams
• Ability to reorient objects from different angles
• Finding relations between different spatial objects
• The hippocampus helps construct a 3D "mental map" of surroundings; crucial for ability to move around in the real world

Brain Surgery Definitions

• Lobectomy: Removal of a lobe or major part of one from the brain
• Lobotomy: Separation of a lobe or a major part of one from the rest of the brain via a large cut (not removed)
• Bilateral Medial Temporal Lobectomy: Removal of the medial portions of both temporal lobes, including most of the hippocampus, amygdala and adjacent cortex

Amnesia

• Amnesia means a deficit in memory caused by brain damage, disease, or psychological trauma
• Retrograde Amnesia: Inability to retrieve information acquired before a particular date (usually the date of an accident or operation)
• Anterograde Amnesia: Inability to transfer new information from short-term to long-term store

Brain Function and Learning

• The brain has the ability to change its functioning in response to experience
• Learning deals with how experience changes the brain
• Memory deals with how these changes are stored and subsequently reactivated

Effects of Bilateral Medial Temporal Lobectomy

• Henry Molaison (H.M.) had his temporal lobes removed in 1953 to treat epilepsy
• His seizures were dramatically reduced, but so was his memory
• He had mild retrograde amnesia and severe anterograde amnesia
• H.M. readily "learns" responses through classical conditioning, but has no memory of conditioning trials

Contributions of H.M.'s Case

• Medial temporal lobes are involved in memory
• STM and LTM are distinctly separate
• H.M. is unable to move memories from STM to LTM; this is a problem with memory consolidation

Amnesia after Concussion

• Concussion definition: A temporary disturbance of consciousness produced by a nonpenetrating head injury
• Posttraumatic Amnesia definition: Amnesia following a nonpenetrating blow in the head
• Concussions may cause retrograde amnesia for the prior period and some anterograde amnesia after
• Such amnesia is correlated with the duration of the coma
• A period of anterograde amnesia suggests a temporary failure of memory consolidation

Retrograde Amnesia and Memory Consolidation

• Concussions disrupt consolidation (storage) of recent memories
• Hebb's theory: Memories are stored in the short term by neural activity
• Interference with this activity prevents memory consolidation; Blows to the head (i.e., concussion) and ECS (electronconvulsive shock) are examples
• Long gradients of retrograde amnesia are inconsistent with consolidation theory

Reconsolidation

• Each time a memory is retrieved from LTM, it is temporarily held in STM
• Memory in STM is susceptible to post-traumatic amnesia until it is reconsolidated
• Patient H.M. has some retrograde amnesia
• The hippocampus stores memories temporarily (standard consolidation theory)
  • This is consistent with temporally graded retrograde amnesia seen in animals with temporal-lobe lesions
• Korsakoff's (Korsakov's) Syndrome
  • Brain disorder caused by lack of thiamine (vit. B₁) in the brain
  • Named after neuropsychiatrist Sergei Korsakoff, who popularized the theory

Major Symptoms of Korsakoff's Syndrome

• Anterograde Amnesia
• Retrograde Amnesia
• Confabulation- invented memories which are taken as true due to gaps in memory
• Meager content in conversation
• Lack of insight
• Apathy

Korsakoff's Syndrome

• Most commonly seen in alcoholics (or others with a thiamine deficiency)
• Includes: Amnesia, confusion, personality changes, and physical problems
• Typified by damage in the prefrontal cortex and medial thalamus + medial hypothalamus
• An amnesia comparable to medial temporal lobe amnesia in the early stages
  • Also features Anterograde amnesia for episodic memories
• Later stages bring severe retrograde amnesia
• It is progressive, complicating its study

Amnesia for Alzheimer's Disease

• Alzheimer's disease is associated with a gradually progressive loss of memory often occurring in old age
• Affects 50% of people over 85
• Early onset is influenced by genes, but 99% of cases are late onset
• About half of all patients with late onset have no known relative with the disease
• Alzheimer's disease is associated with the accumulation and clumping of the following brain proteins:
  • Amyloid beta protein 42, which produces widespread atrophy of the cerebral cortex, hippocampus, and other areas
• An abnormal form of the tau protein, part of the intracellular support system of neurons
• Accumulation of the tau protein results in plaques- structures formed from degenerating neurons
• Accumulation of the tau protein results in tangles- structures formed from degenerating structures within a neuronal body

Alzheimer's treatments

• Damage occurs in the basal forebrain
• Treatment enhances acetylcholine activity
• One experimental treatment stimulates cannabinoid receptors to limits overstimulation by glutamate
• Research with mice suggests stimulation of the production of antibodies against amyloid beta protein could immunize against Alzheimer's