Damage to the temporal lobes can leave a person with some impairment of past memories but particularly incapable of forming new memories, without any impairment of intelligence.

Learning as the Storage of Memories

 Amnesia: The Failure of Storage or Retrieval

 Anterograde amnesia is an inability to form new memories

 Retrograde amnesia refers to an inability to recall memories from before the damage. The degree of amnesia is related to how much damage was done and what structures were damaged

The hippocampus, a structure within the temporal lobe, is linked to memory

    Mechanisms of Consolidation and  

   Retrieval

 Consolidation is the process that produces a permanent representation of memory. This process continues for some time after learning

  Retrieval is the process of accessing stored memories

     Where Memories Are Stored

  The hippocampus is not the permanent storage place for memories, but instead directs activities (e.g., associating stimuli with one another, or with responses; storing and retrieving memories)

  Memories are stored in different cortical areas, depending upon where the information was processed

 Two Kinds of Learning

 Declarative memory is memory of facts

 Non-declarative memory involves several kinds of learning not associated with factual material

 Working Memory provides a temporary place for information while it i being used. It is necessary for several activities we perform every day

 Much of the cortex participates in working memory, but the prefrontal area plays a primary role

 The prefrontal area may serve as a central executive, directing the neural traffic of working memory

Brain Changes in Learning

 Long-Term Potentiation (LTP)

 LTP is an increase in synaptic strength following repeated stimulation

The effect can occur in several regions of the brain and last from a few  minutes up to a few months

 Associative long-term potentiation (ALTP) occurs when weak synaptic connections are potentiated because they are on the same  postsynaptic neuron as a strong connection

Long-term Depression occurs when a presynaptic neuron is not firing while the postsynaptic neuron is being fired by other neurons.This  weakens the synapse; it   can block long-term potentiation that has already occurred

Associative Long-Term Depression is the weakening of a synapse  that occurs when two presynaptic neurons fire at different times

Theta rhythm in the hippocampus appears to be necessary for some  kinds of memory formation. It can facilitate LTP or block LTP that  occurred earlier. This indicates a primary role for the hippocampus in

                              managing LTP

Synaptic Changes in LTP

 The presynaptic neuron increases its neurotransmitter output as a result  of   feedback from the postsynaptic neuron

Activation of AMPA glutamate receptors unblocks NMDA glutamate  receptors, allowing the neuron to fire.

As  a result of calcium influx and alteration of gene activity:

The number of and sensitivity of AMPA receptors is increased 

The role of LTP in Learning

Manipulating LTP increases or decreases learning, so LTP may be  fundamental to learning

However, in many cases experimentally induced LTP does not last as  long as some memories

Consolidation

Apparently the hippocampus is involved in short-term memory, while the cortex is required for long-term storage

Long-term memories are subject to reconstruction, particularly at the time of retrieval. They must be reconsolidated after each time they are retrieved, making them vulnerable

 Disorders of Learning

 Aging is associated with memory loss, though it is not inevitable

The hippocampus loses synapses and NMDA receptors

 LTP is impaired

Metabolism decreases in the entorhinal cortex

 Neurons lose myelin

The basal forebrain area loses neurons

 Alzheimer’s Disease is the most common cause of dementia in elderly individuals

The Diseased Brain: Plaques and Tangles

 Plaques are clumps of amyloid, a type of protein that interferes with neural transmission

 Neurofibrillary tangles are webs of neurofilanients that develop inside neurons and are involved with killing brain cells

 Alzheimer’s and Heredity: Four genes have been found that influence the development of Alzheimer’s disease, and it is suspected there are more

Treatment of Alzheimer’s Disease has focused on restoring the neurotransmitter acetylcholine

 Nicotine supplements also have produced improvements in Alzheimer’ s patients

Anticholesterol drugs have been helpful

Estrogen supplements following menopause have helped women

Instead of manipulating the genes responsible for Alzheimer’s, some doctors implant genes for nerve growth factor. This has restored acetylcholine levels

 Korsakoff’s Syndrome is a form of dementia that is almost always caused by alcohol abuse

The cause of the disease is an inadequate diet

 Alcoholics commonly substitute the calories from alcohol for food

                      Thiamine diet can relieve some of the

                     symptoms, but cannot  reverse brain

                     damage