Brain Structures and Amnesia

Question 1

How many people are affected by a neurological condition? What does a healthy brain determine?

Answer 1

1 in 4 people are effected.
The quality of how healthy our brain is determines how we are, how we feel, and what we do. The quality of our life.

Question 2

What must we consider when attempting to intervene with potential brain health effects?

Answer 2

The brain and the entire nervous system. The brain is only one part of the NS, it influences and is influenced by peripheral regions and by many hormones.
- We must focus on the entire NS

Question 3

What does the nervous system outline look like? What’s it’s structure?

Answer 3

1. Central Nervous system (CNS). Has sub-sections - The brain, and the Spinal cord.
2. The Peripheral Nervous System: connects body muscles and organs with the CNS.
   - Has 2 sub-sections:
   - The Somatic Nervous System: motor nerves to muscles and sensory nerves from body; the cranial and spinal nerves)
   - The Autonomic Nervous System: autonomous actions of internal organs and glands): this further splits into two sub-headings:
   - The Sympathetic Division: (Increase/arousal, for action) fight or flight
   - The Parasympathetic Division: rest and digest

Question 4

How many cells are in the brain? What are these cells called?

Answer 4

On average we have 170billion cells.

Half of these cells are neurons: come in many forms, and allow us to process and transmit information, using axons.

The other half are Glial Cells (Glia): which enable neurons to function. Critical for the quality of neuron brain cells throughout our lives.

Question 5

What are the three main types of Neurons and how can we identify them by their structure?

Answer 5

1. Purkinje cell from the Cerebellum.
   - Translates to ‘little brain’. Looks like a branchy tree/ many tree-like dendrites.
2. Spiny neuron in the basal ganglia - which is a group of structures in the brain involved in coordination nd movement (nucleus accumbens, meaning ‘ adjacent nucleus’, close position near important brain structures ).
   Spiney name because the neurons look alot more spiney and rigidy than the rest.
3. Pyramidal Neuron in the CA1 region, a critical part of the hippocampus. Is branched out in the shape of a pyramid.

Question 6

What are Latin translations for key structures in the brain? (FORNIX, HIPPOCAMPUS, AMYGDALA, OPTIC CHIASMA, MAMMILLARY BODIES, PONS, MEDULLA)

Answer 6

FORNIX: arch, looks like arch
HIPPOCAMPUS: seahorse, looks like one
AMYGDALA: looks like an almond. A.
OPTIC CHIASMA: Chiasm, greek letter x chi. looks like a cross shape
MAMMILLARY BODIES: ‘breasts, two circles
PONS: bridge, acts as a wee bridge
MEDULLA: ‘pyramids’ of medulla. bit in the middle between brain and spinal cord.

Question 7

What happens to the Mammillary Bodies upon excess alcohol consumption?

Answer 7

Severe alcohol abuse can shrink your Mammillary Bodies - associated with Korsakoffs amnesic syndrome.

• Alc excess may lead to the mammillary bodies getting zapped which can have a further impact on the thalamus, as that’s where MB projects to.
• The Thalamus is your brain’s bus station. All info except smell passes through there before being sent to your brain’s cerebral cortex for interpretation.
• The zap of our MB can lead us to hvaing full blown memory disorder

Question 8

How does food quality relate to our brain?

Answer 8

If we don’t expose ourselves to sufficient food quality, it predisposes us to brain damage later on.

Vit B1 is top of the list

Question 9

Explain what ‘two hemispheres’ refers to.

Answer 9

The left and right hemispheres of the Cerebrum: the visible main brain.

These two hemispheres are joined together via the corpus callosum (‘hard body’). A massive band of 200 million axon fibres. These fibres interconnect neurons in the cortex (outer bark) of both hemispheres.

A healthy corpus callosum enables a smooth/seamless integration of information across both hemispheres.

Question 10

Describe what Foetal Alcohol Syndrome/ Spectrum Disorder (FASD) is, and what area of the brain is affected.

Answer 10

If fetuses are exposed to alcohol, a spectrum of FASD can occur.

• The place damaged as a consequence is the corpus callosum, especially the posterior half.
• A third of women in NZ still drink during pregnancy, most of this occurs during the time they don’t know they are pregnant. - their children by the age of 5 have various behaviour disorders

Question 11

What are the features of seeing when our corpus callosum is split? i.e Split brains? and How do we test this?

Answer 11

When seeing:
Our left half of our eyes projects to the right hemisphere, and the right half of our eyes project to the left.
When reading HEART: ‘He’ is projected to the RH, and ‘Art’ is projected to the LH.

To test this: we flash a word in front of someone to stop them from moving their eyes.

Intact CC: registers the word as heart
Split brain: due to the split - the LH is the linguistic hemisphere, and they only register ‘art’ because they don’t have the communication from the RH to piece it all together.

Question 12

What are some basic principles about the different operations of the two hemispheres of the brain, connected by the corpus callosum

Answer 12

Left Hemisphere (LH):

Language: Primarily responsible for language, including speaking, reading, writing, and understanding.
Logical Thinking: Associated with logical reasoning, analytical thinking, and problem-solving.
Math: Handles mathematical calculations and logic-based tasks.
Detail-Oriented: Focuses on details and the ability to process information in a sequential, step-by-step manner.

Right Hemisphere (RH):

• Spatial Abilities: Handles spatial awareness, visual imagery, and recognizing faces and objects.
• Creativity: Associated with creativity, artistic ability, and musical skills.
• Emotion: Processes emotional content, both in recognizing emotions in others and in expressing one’s own emotions.
• Holistic Thinking: More adept at seeing the big picture and processing information in a holistic, integrative way.
  Cross-Control:

Contralateral Control: Each hemisphere controls the opposite side of the body (the LH controls the right side, and the RH controls the left side).
Specialization:

Specialized Functions: While both hemispheres can perform a variety of tasks, they have specialized functions that dominate in each hemisphere.
Integration:

Collaboration: The corpus callosum allows the two hemispheres to communicate and collaborate, ensuring integrated and coherent functioning of the brain.

Question 13

What does the experiment with the split-brain patient and nut tell us?

Answer 13

A patient is at a desk and has a table and screen in front of them.

• Nut is flashed on the left side of the screen, left visual field projects to the right halves of both retinas and thus to the RH only, which then operates the left hand. Although they can’t tell you what the word is because the linguistics side is the left and this is projected to the right, they still picked up the word they saw, the ‘nut’ because the right hemisphere controls the left hand which picked it up.

i.e the RH processes spacial stuff.

Question 14

How does a split-brain patient perceive ‘Hat - Band’ written cue?

Answer 14

Hat goes to the right hemisphere, and band goes to the left. Therefore, they only recall band.

Question 15

Each cerebral hemisphere has Four Lobes of Cortex. What are they and their basic/main purpose?

Answer 15

Frontal Lobe - High level control, spontaneity, and decisions.

Parietal Lobe (side) - Perception/space

Occipital Lobe (back) - Visual Functions

Temporal Lobe - Memory, language

Although different regions have different functions, they’re not explicitly housed there.

Question 16

What is Hemi-neglect and whats the common cause of it?

Answer 16

Stroke typically causes injury in the lobe(s).

Hemi-neglect is after right-sided partial lobe injury: Inattention to the left side of space/ the body - the person neglects the left half of the spatial world. Due to this info not being processed/ picked up.

• Our right hem is associated with spacial things, and the left side of things is projected to the right side.

Question 17

What are the Greek words for describing the brain?

Answer 17

Brain: Encephalon, which means ‘the thing in the head’.

End Brain/ Cerebral Hemispheres: Telencephalon, which means ‘end brain’.
- This houses the Neocortex, Basal Ganglia and Limbic system.

Between Brain: Diencephalon, meaning the brain that’s in between. Di-encephalon.
- This houses the Thalamus and Hippocampus

Mid-brain: Mesencephalon, ‘meso’ means middle’.

Hind Brain: Metencephalon, ‘Met’ means Hind.
- houses the Cerebellum and Pons

Medulla Oblongata: Myelencephalon, ‘myel’ means ‘spinal bit’, this part of the brain is continuous with the spinal cord

Question 18

Explain the process of the Embryonic Development of the Brain.

Answer 18

• It develops at the front end of the neural tube
• It gains 3 buldges (forebrain, midbrain, hindbrain)
• The front bulge (future fore-brain) then develops two other bulges, this is the telencephalon that develops into the left and right hemispheres
• Bulges develop and grow across the hind brain, leaving the spinal part below

Question 18

What do changes in the Myelencephalon infer?

Answer 18

Changes down here, i.e the part of the brain that is continuous with the spinal cord, may be responsible for brain cells in other areas of the brain going wrong. Until eventually the whole Telencephalon is enveloped in abnormal proteins
eg: Parkinson’s disease

Question 19

Explain the key elements of the Limbic System

Answer 19

It is the key region for normal Memory. It is located mostly in the Telencephalon. There are limbic parts in the Thalamus.

Limbic means ‘inner boarder’.

The Limbic system is a system of structures, sits inside the cerebral structure and above the brainstem.

Houses:
- Hippocampus: Essential for memory formation.
- Amygdala: Involved in emotion processing.
-Thalamus: Limbic parts are involved in sensory relay and consciousness.
-Mammillary Bodies: Important for recollective memory, housed in the diencephalon.
-Fornix: A bundle of nerve fibers that connects parts of the limbic system, also in the diencephalon.

However - the Limbic Thalamus, Mammillary bodies, and fornix are housed in the Diencephalon.

Question 20

Explain the case of H.M in relation to Memory. What were the key effects on the brain?

Answer 20

Case of H.M.:

Background: H.M. (Henry Molaison) underwent surgery to remove parts of his medial temporal lobes, including the hippocampus, to treat severe epilepsy.

Key Effects on the Brain:

• Hippocampus Removal: The surgery removed significant portions of the hippocampus.
• Medial Temporal Lobe Damage: Both sides of the medial temporal lobes were affected.

Key Findings:

• Anterograde Amnesia: H.M. could not form new long-term memories after the surgery, demonstrating severe anterograde amnesia.
• Retrograde Amnesia: He had some loss of memories from the years immediately before the surgery but could recall older memories.
• Intact Procedural Memory: H.M. retained the ability to learn new motor skills, showing that procedural memory does not rely on the hippocampus.
• Separation of Memory Systems: The case highlighted the distinction between short-term and long-term memory, and between declarative and procedural memory. Whatever he rehearsed in his mind he could repeat back
• here and now conversations were seen as pretty normal.

Question 21

What happens when our Medial Temporal Lobe (MTL) is injured? What influences this injury?

Answer 21

The more its injured the more severe the memory loss - for new events and more extensive retrograde amnesia (loss of memory before event).

The hippocampus is very vulnerable to viruses, when viruses attack it, it also affects the surrounding cortex.

Question 22

What is your ability to remember events called?

Answer 22

Episodic memory. Remembering unique events around something normal and less-memorable.

Question 23

What is semantic memory?

Answer 23

Long-term memory. Knowing how to drive is semantic memory.

Question 24

What did the H.M case find out about the Medial Temporal Lobe? What are the details of the MTL?

Answer 24

The medial temporal lobe (MTL) memory system, which includes the hippocampus and adjacent cortical areas (like the entorhinal, perirhinal, and parahippocampal cortices), plays a crucial role in long-term memory. This system is essential for both episodic memory (remembering events) and semantic memory (facts and knowledge).

Medial Temporal Lobe (MTL) Memory System: The hippocampus, along with surrounding cortical areas, forms a critical system for memory.

Episodic Memory: The ability to remember specific events and experiences.

Semantic Memory: The ability to remember facts and general knowledge.

Structures Involved: The entorhinal cortex (EC), perirhinal cortex (PR), and parahippocampal cortex (PH) are important parts of this system.

Function: This entire system works together to support different types of long-term memory.

Question 25

Explain what Diencephalic amnesia is.

Answer 25

Severe amnesia is caused by damage to the diencephalon. (different from the Medial Temporal Lobes memory Loss)

• when alcohol abuse PLUS deficiency in thiamine (Vit B1- which is essential for cell function/energy/metabolism) can cause acute brain injury and memory loss.

This is called Korsokoffs Syndrome

Question 26

What is Korsokoffs syndrome and what are the effects physiologically?

Answer 26

It is a form of diencephalic amnesia.

• Main leisons are in the diencephalon.
• The most relevant is damage to the Limbic Thalamus and the Mammillary Bodies.

Question 27

What does the memory impairment of Korsokoffs , H.M, and other cases of severe amnesia have in common?

Answer 27

Concerns with Explicit recall of episodes (events and associated items), brought to mind (conscious recollection of the knowledge) - often both new and personal events (episodic memory) and new general knowledge ( semantic memory loss).

There is intact long-term memory when the memory itself is expressed implicitly.

Question 28

What are some examples of intact memory in H.M and Korsokoffs diabilities?

Answer 28

Skill memory and habit learning.
Without remembering they practised a certain task - they got better at it.

Question 29

What do Ischemic (stroke) lesions cause and what category does it fall under?

Answer 29

This is another form of Diencephalic Amnesia.

We can have small and big strokes. They can be so small that they can just split something, and that’s severe enough to cause damage.

MTT (Mammillothalamic Tract): This is a pathway that goes from the mammillary bodies to the anterior thalamic nuclei. It’s important for memory.

Korsakoff Syndrome: This condition affects the mammillary bodies and anterior thalamic nuclei. People who suffer from strokes often have injuries in this pathway, leading to memory problems.

Connection Disruption: Damage to the connections between these structures can lead to amnesia.

Question 30

In 1997, developmental amnesia was studied between 3 children. What were the causes of this amnesia and what did it lead to?

Answer 30

These kids couldn’t recall what happened in their days, disorientated. BUT their semantic memory was fine/ facts were fine.

They found that the volume of their hippocampus was 50% of what it should be.

This was caused by anoxia (lack of oxygen) in some point of their life.

Question 31

Anoxia causes damage to the hippocampus and what else?

Answer 31

Mammillary bodies. Some patients did not hvae them.

Many people when they’re born will have an anoxic event. 20-40% of them will have extreme injuries to MB.

Question 32

Explain what the Anterior Nucleus of the Thalamus is a part of. What does this tell us about memory?

Answer 32

The anterior nucleus of the thalamus (ATN) is part of a distributed “hippocampal-cortical-diencephalic” memory system, which includes the hippocampus, mammillary bodies, and various cortical areas. This system is normally well-integrated and essential for memory function.

Key Points:

Interactions: Connections between the anterior cingulate cortex (prefrontal cortex) and the retrosplenial cortex (RSC) are crucial for memory function.

Injury Impact: Damage to the mammillary bodies or the mammillothalamic tract (MTT) disrupts the function of the RSC and the ATN, leading to memory dysfunction.

Summary: The ATN and its connections are vital for a well-integrated memory system. Injury to key structures like the mammillary bodies or MTT can cause significant memory problems by affecting the connectivity within this system.