Chapter 9 - Mechanisms of Memory formation

Working memory ARMD

- Perform more poorly than young people on complex working memory tasks - Eg. Difficulty repeating string of numbers backwards, doing several tasks at once or dividing attention without interference - Pre-frontal cortex less active and less efficient over 60 yrs of age. o Implications for elderly drivers and their ability to navigate the roads safely?

Frontal lobes of the cerebral cortex

- Working memory - Procedural memory - Episodic memory

Lobes of the cerebral cortex

Declarative memories for some forms of sounds, pictures and words/language

Neurons

Neurons receive information from other neurons, process this information and then communicate it to other neurons. - Neurons are generally comprised of three elements -Dendrites - Soma - Axon

Specific neurotransmitters

Some neurotransmitters help memory storage while others can disrupt it. It is known that memory is helped by the serotonin and acetylcholine neurotransmitters, as well as the hormone noradrenaline. Dopamine and Glutamate are heavily involved in learning, which is a 'memory' process as well.

Long term memory - semantic memory ARMD

(DECLARATIVE) - Perform just as well as young people but it may take longer to encode and retrieve info. - It may take longer to learn the new material but if they are given enough time, they can learn just as well as young people - Implicit knowledge based memories (reading and spelling of familiar words) is not effected and is readily retrieved and used.

Long term memory - episodic memory ARMD

(Declarative) - Older people have autobiographical episodic memory decline - Prospective memory (remembering things to do in the future) is also affected. - Episodic memory is relatively stable but there is a sharp decline after middle age possible due to the fact that older people tend to talk more readily about their lives when they were younger rather than more recent personal events - May remember early events but not more recent - Higher performance for women in old age (only memory with gender difference)

Alzheimers

- An irreversible, progressive and fatal neurodegenerative disease that attacks the brain and kills brain and nerve cells, causing severe cognitive, mental and behavioral decline. - Most common form of dementia and symptoms usually appear after the age of 65 however early onset can occur in ones 30's - It is the 4th largest cause of death and impacts on 25% of those over 85 years old and with an aging population this is only going to increase - Physical changes occurs 10-20 years before AD is presented

Brain Trauma

- Brain Trauma is an umbrella term that is used to describe any brain damage that impairs or interferes with normal functioning of the brain, either temporarily of permanently - It refers to 'organic' or physiologically-based amnesia - It is typically a partial and selective amnesia, total amnesia is extremely rare o Accident resulting in injuring o Surgery o Disease and infection o Drug and alcohol abuse o Seizure o Malnutrition

Dementia

- Dementia refers to a disorder affecting higher mental functions that is characterized by progressive decline, with memory loss one of first signs - Symptoms include loss of mental capacity including memory loss, decline in intellect, poor judgment, poor social skills and abnormal emotional reactions - Not part of the normal aging process - More than 60 diseases and illnesses can cause dementia such as reduced blood supply to the brain or toxins such as alcohol - Alzheimer's disease is a common form of dementia

Organic forms of forgetting

- Forms where memory loss occurs due to physiological/biological factors that cause damage to the brain and therefore interfere with its proper functioning.

Alzheimers Symptoms

- In the other ages the symptoms of Alzheimer's disease can be very subtle. However, it often involves gradual, severe memory loss, confusion, impaired attention disordered thinking and depression (my cat Anna talks delicately) Other objects may include: o Persistent and frequent memory difficulties especially of recent events o Vagueness in everyday conversation o Apparent loss of enthusiasm for previously enjoyed activities o Taking longer to do routine tasks o Forgetting well-known people or places o Inability to process questions and instructions o Deterioration of social skills o Emotional unpredictability Order of memory loss

Dementia symptoms

- It is first increasingly harder to remember people and events (especially recent ones) - Find it difficult to think about and process information - They may misplace things or be unable to do everyday taskas such as eating, dressing, driving or taking care of himself/herself - Display strange or uncharacteristic behaviours - Become easily upset or confused about time and place - Be unusually aggressive or suspicious - Have trouble speaking clearly, jumbling and confusing his or her words - Have problems understanding what others are say and then gradually lose the ability to communicate through written language.

Motivation and confidence ARMD

- Motivation: some loose interest in trying to learn and recall new things - Those who actively try and learn new things into old age suffer less memory loss - Testing on 'word lists' may be seen as not important and not actively try to achieve good results - Confidence: some worry about capacity to learn new things and do not seek opportunities/make as much effort

Measures of retention ARMD

- Older people have more difficulty in retrieving new information rather than encoding new information. - While Recall declines with age, Recognition does not decline with age (even for the same pieces of information) - Implications for memory research which has highlighted that you must choose the right method of retention when testing ARMD

Memory consolidation

- Physical change (A physical change must occur in the synapses) - No Disruption (if the process is disrupted, long term memory is unlikely to form) - Time (Consolidation takes time - 30 minutes)

Long term memory - procedural memory ARMD

- Procedural (implicit) memories not affected - ie. Opening a can, cleaning teeth, cooking a meal

Alzheimers order

- The earliest symptom is usually impaired declarative memory where the patient has difficulty reembering events from the day before, forgets names and has difficulty finding the right word when speaking. (dolly (declarative) never (names) wins (words) round (repetition) robins (recognising) - Next, the patient might repeat stories or questions, and eventually will fail to recognise familiar people and family members. It eventually leads to the death of the patient which usually occurs 4-8 years after diagnosis but may make over 20 years.

What changes occur

1. When a neuron is activated more than once, the presynaptic neuron increases the number of neurotransmitters it releases into the synapse 2. This then prompts the dendrites of the postsynaptic neuron to grow. They become more numerous and also grow towards the presynaptic neuron. They also became more sensitive to the neurotransmitters 3. This then means that new synaptic connections are formed, making it easier for the message to travel from one neuron to another Each time we access a memory or give a memory extra meaning, we strengthen the connection and the memory itself.

Neurodegenerative Disease

A disease characterized by a progressive decline in the structure, activity and function of brain tissue o Neurons (neuro) gradually deteriorate (degenerate) and lose their function o Typically age related, such as Alzheimer's disease and dementia

Axon

A nerve fibre in the neuron along which the electrochemical nerve-impulse is transmitted away from the soma and towards the cells that communicate The information that is transferred through the axon is referred to as action potential which consists of brief changes in the elecrial charge of the axon. Neurotransmitters are secreted by the terminal buttons at the end of an axon after information has been sent down the axon in the form of electrical impulses.

Memory trace

A physical or chemical change that is believed to occur in brain cells as they store information during memory formation.

Amnesia

Amnesia refers to the loss of memory due to any reason, and can be partial or complete, temporary or permanent o Might be caused by brain trauma and injury or degenerative diseases such as Alzheimer's - It includes specific types of amnesia: Anterograde and retrograde amnesia.

Damage to the amygdala

Amygdala damage shows reduced ability to acquire conditioned (learned) emotional responses and to interpret or express a variety of emotions These individuals form conscious explicit memories involving details of the even but not implicit procedural memories that would enable them to produce the fear response.

Cerebral cortex

Associated with the encoding formation and storage of long term declarative memories

Across the synapse

At the axon terminal, neurotransmitters are released from vesicles and they travel across the synaptic gap. This is now a chemical process Neurons never touch

Effects of Alzheimer's disease on the physiology of the brain include:

Beta-amyloid protein plaques (abnormal clusters of dead and dying nerve cells, the products of which have accumulated around sticky molecules of beta-amyloid protein. In Alzheimer's it has been transformed into a form that is toxic to the brain and unable to be metabolized. Neurofibrillary tangles (insoluble, twisted structures caused by the build-up of protein and plaques within nerve cells that clog up the brain. In heathy brains tau helps memory traces stay formed but in areas where tangles are forming, tau collapses into twisted strands called tangles which measn that the tracks can no longer stay straight and they fall apart and disintergrate. Atrophy (wasting away) of brain tissue (especially deterioration of the hippocampus and eventual general brain shrinkage from cell death. At death, the brain of an Alzheimer's patient may have lost up to 50% of its weight). This is caused as nutrients and other essential supplies can no longer move through the cells which eventually die. Destruction of neurons involved in production of some neurotransmitters, especially acetylcholine which is necessary for cognitive functioning and is a memory transmitter

Damage to the hippocampus

Could be damaged by; o Psychological factors: stress, anxiety depression, PTSD (prolonged stress could lead to the shrinking of the hippocampus) o Brain trauma: head injury o Degenerative conditions: Alzheimer's disease, herpes, encephalitis o Surgical: Old fashioned treatment for epilepsy - Damage to the hippocampus does not seem to seriously affect storage or retrieval of procedural memories, but formation and retrieval of declarative memories is affected how ever they are not aware that they ever learnt the information - Damage does not affect short-term storage or working memory in any significant way - Provides evidence that Short Term Memory (or working memory) is different from long term memory and that the hippocampus is not involved in short term storage. - Hippocampus transfers newly encoded memories to other cortical areas for storage. This could be areas of the frontal lobe cortex or temporal lobe cortex - Damage to both hippocampi results in anterograde amnesia (difficulty encoding and recalling any new memories since damage occurred).

Dopamine

Facilitates movement, attention, learning, reinforcement

Short term memory ARMD

For simple tasks there is no difference with age and they can perform just as well on them (for example on remembering a list of numbers) - Newly learnt verbal information is most affected - Newly learnt visual information is less affected

Normal age-related memory decline (ARMD)

Functioning of the Central nervous system begins to slow down which may effect memory After age of 60, there is a reduction in the function of the pre-frontal cortex reduction which leads to deficits in working memory and episodic memory Decline in the bundles of axons (white matter) that connect different regions of the brain causing a disruption of the communication between the difference regions of the brain. There is a hypothetical loss of synapses in the hippocampus which leads to less connections between neurons and therefore a slower rate of learning and a more rapid of forgetting.

Travelling through the neuron

Information (in the form of a neurotransmitter) is received at receptor sites in the dendrites of a neuron, from here the message travels down the neuron through the axon and to the axon terminals This is called an electrical process

Acetylcholine

Memory and memory loss, learning Muscle movement Activates cerebral cortex REM sleep Hippocampus

Memory decline over lifespan

Natural to experience some memory difficulties as you age however it is not an automatic part of the normal ageing process Connected with the organically aging brain In the case of dementia and other degenerative disorders, decline is more rapid and impacts on functioning more seriously

Glutamate

Necessary for the changes in the synapses that occur with memory formation

Serotonin

Regulates mood Eating, sleep, arousal, pain

Long Term Potention

Research shows that memory is formed due to biochemical changes in the synapses in response to different neurotransmitters (chemicals) - Neurons that fire together, wire together

The Medial temporal lobe

The Medial temporal lobe is the inner surface area at the base of and towards the middle ('medial') of the temporal lobe. This area included the hippocampus; the amygdala, which is next to and touches the hippocampus; and other cortical tissue. There is evidence that patients are likely to experience more verbal memory loss afterremoval of their left temporal lobe (language side) whereas patients with loss of their right temporal lobe are likely to have loss of non-verbal memory such as maze-learning.

Amygdala

The amygdala is a small almond structure (about 1.5 centimeters long) located behind the temple and next to and interconnected with each of the hippocampi in the medial temporal lobes.

Role of the amygdala

The amygdala plays crucial roles in processing and regulating emotional reactions, particularly strong emotions such as fear and aggression. In particular, it is involved in the encoding and storage of declarative memories that have a significant emotional component (sometimes called emotional memories) Also highly specialized for remembering emotions shown on faces. More likely to remember events that produce strong emotional reactions One reason is that the amygdala attaches emotional significance is because when adrenalin is released it stimulates the amygdala which activates the hippocampus to encode and store the relevant memories The amygdala contributes to the formation of explicit declarative memories. This is apparent in a specific type of episodic memory known as a flashbulb memory.

Soma

The cell body of a neuron. It is the largest part of the neuron and controls metabolism and maintenance of the cell.

Retrograde amnesia

The difficulty in recalling previously stored memories from before the person sustained the damage o Retro meaning backwards: the memory loss is backwards in time - Memory loss Is usually the period just prior to the injury but may be moments, days, weeks, moths or even years - Oldest memories tend to be left unaffected - Usually temporary, can be caused by a blow or knock to the head or a trauma such as a stroke and if this is the case memory loss usually shrinks with recovery however most immediate memories probably will never be recovered (consolidation disruption) - Common with patients treated with ECT (Electroconvulsive shock therapy) - When occurs in Alzheimer's and dementia patients, lost memory is unlikely to be recovered.

Role of the hippocampus

The hippocampus has a crucial role in forming or encoding new declarative explicit memories (semantic and episodic) but not in forming or retrieving implicit procedural memories It is also responsible for difficult tasks that draw upon declarative memory eg. A child learning to spell unfamiliar words Its role in forming new declarative explicit memoires is sometimes referred to as consolidation, a process that involves strengthening of newly forming memories to enable their permanent storage. It also plays an important role in the relationship between emotion and memory including both the emotions that are generated by particular memories and memories that are triggered by emotions.

The hippocampus

The hippocampus is a medial temporal lobe structure that is crucial for long- term memory formation (but not all long term memory types as after a period of time, a more permanent memory is formed or transferred to somewhere else in the brain for example in the cerebral cortex) There is one 3.5cm long, tubular and curved shaped hippocampus in each hemisphere however it is usually larger in women. Also connected directly with the frontal lobe, thalamus, and amygdala.

Anterograde amnesia

The loss of memory only for information or events that occur after the individual has sustained the brain damage so they have the inability to encode, store or learn new memories. o Antero means forward: the loss is forward in time - Memory for events prior to damage usually remains - This is commonly associated with Alzheimer's disease where damage has occurred to the temporal lobe and hippocampus - Usually results from damage to the hippocampus (particularly a part called CA1 which connects to the storage part for the cortex - H.M had great difficulty forming any new long term declarative memories following his operation o Did not remember names of his doctors o Did not remember events that occurred just moments before.

Communication between the neurons

The synapse is the junction or small gap between two neurons where the enc of the axon on the presynaptic neuron comes into close proximity with the receptor sits of the dendrites of the post-synaptic neuron but never touch. The process of neurons communicating is known as synaptic transmission which is a chemical process. The neurotransmitter that is secreted from the presynaptic neuron affects the activity of the post-synaptic neuron

Dendrites

The tree-like part of a neuron that receives information from other neurons

Cerebellum

Thought to be involved in Procedural memories, particularly motor skills Involved in the implicit process of remembering as skill as well as classically conditioned responses.