Forebrain 2 Flashcards
(190 cards)
1
Q
What are the 2 divisions of the visual association cortex?
Where are these pathways?
A
- Where Pathway –> Dorsal Part of the Parietal Lobe
- What Pathway –> Temporal Lobe
2
Q
Which brodmann area is premotor cortex?
A
- Area 6
3
Q
What is on the medial surface of the hemisphere of the premotor cortex?
A
- Supplementary Motor Cortex
4
Q
Which brodmann area is important for visually guided movements?
Which lobe and what part of it is this found?
A
- Area 7
- Medial Surface of the Occipital Lobe
5
Q
What is the whole language area called and where is it found?
A
- Wernicke’s Area
- Present on the Dominant Side (Left Side)
6
Q
Where is the primary auditory cortex found?
Is it found on both sides or one side?
A
- Small & Pale Part
- Top of the Superior Temporal Gyrus
- Temporal Lobe
- Found on both sides for either ear
7
Q
What is the function of the primary auditory cortex? (generally)
A
- This is where auditory information first arrives in the cerebral cortex
8
Q
What happens if you get a lesion (e.g. vascular) in one primary auditory cortex?
A
- Become deaf in one ear
NB: Not both as the other would still be receiving auditory information
9
Q
Where is Wernicke’s Area found?
Which hemisphere?
A
- Present only in the left (dominant) hemisphere
- Large & poorly defined area around the primary auditory cortex
- Starts –> infront of the auditory cortex (temporal lobe)
- Extends –> into the parietal lobe
-
Very close to the primary auditory cortex (& other forms of language)
*
10
Q
What is Wernicke’s Area responsible for?
A
- Sensory Language Centre
- Different forms of language (e.g. speech)
- Interprets & formulates language (e.g. speech)
- Allows for meaningful sentences to be spoken
NB: Not to do with speech fluency
11
Q
Where are other forms of language areas found? Which lobe?
A
- Parietal Lobe (other forms of language)
12
Q
Summarise function of Broca’s Area and Wernicke’s Area
A
- Broca’s Area –> responsible for fluent speech
- Wernicke’s Area –> responsible for meaninful speech
13
Q
What is a function of the angular gyrus?
Which lobe is it found in?
A
- Parietal Lobe
- Writing & Reading
14
Q
What are the effects of an angular gyrus stroke (small stroke)?
A
- Small strokes involving angular gyrus
- These can affect writing
- Almost complete loss of writing ability
- Takes hours to write a single word
NB: Their ability to drive a car however remains the same
15
Q
What is the parahippocampal gyrus responsible for?
A
- Place Area –> where you identify different places
Present in both hemispheres
16
Q
Where is the Fusiform Face Area (FFA) found?
Which visual part is it a part of?
Which gyrus is it found in?
Which hemisphere is it found in?
A
- Fusiform Gyrus
- Part of the Visual Association Cortex
- Active in Both Hemispheres when Identifying faces
17
Q
What happens if there is an FFA lesion?
A
- Only FFA lesions on the right seem to cause a big effect
- Lose ability to recognise faces
NB: Weirdly both are activated when you are trying to recognise faces but only the right has a signfiicant effect
18
Q
Where is the primary visual cortex found?
A
- Buried in the Calcirine Sulcus
- Extends to the Occipital Lobe
- V1 / Area 17
19
Q
Generally, what is the visual stream pathway in terms of the cortex?
A
Visual Information first arrives in V1 –> sent to V2 for interpretation –> then sent to other visual areas for further interpretation
20
Q
Where is the uncus?
A
- Bump on the medial side of the temporal lobe
21
Q
What is the function of the uncus?
A
- Primary Olfactory Cortex
(Small in humans but big in fish)
22
Q
Where is the sensory & motor areas for the lower limb found?
A
- Paracentral Lobule
- Medial surface of the cerebral hemispheres found on the medial surface of the gyri infront of & behind the central sulcus
- Motor Cortex (lower limb) –> Infront of the Central Sulcus
- Somatosensory Cortex (lower limb) –> Behind the Central Sulcus
23
Q
Where is the angular gyrus?
A
- Dominant Hemisphere –> right side
- Parietal Lobe
- Part of Wernicke’s Area
- Follow the Superior Temporal Gyrus?
24
Q
What is the angular gyrus responsible for?
A
- Reading (alexia)
- Writing (agraphia)
- Interpretation & Control of Language
Important for Meaningful Speech
25
What is the function of **Broca's** **Area**?
* **Fluent** **Speech**
* Can get around it by **singing** a **sentence** flowingly (compromise)
* Thus giving them ability to form **synchronised** **speech**
26
What is the **bulge** in the **middle** **section** of **M1 (post-central gyrus)** called?
* Hand Knob
27
What is found in the **superior** **parietal** **lobule**?
Why is it vitally important if the **cerebellum** is **not** working?
* **Visually Guided Movement centre**
* Vital if the cerebellum isn't working as you need to **interpret** **_where_** **objects** are to be able to **manually** **follow** **them**
28
What is **sterognosis**?
* To be able to feel **texture** & **shape** & **weight**
29
What are the **effects** of a **lesion** in the **parietal** **lobe**?
* Behind the **Hand** **Area** is the **Sterognosis** **Area**
* Thus this is where you **compare** **past** **experiences** to **present**
* To be able to **feel** & **interpret** an **object**
* Lose this ability
30
Where is **sterognosis area** found?
* Behind the Hand Area
31
Give **2** **parietal** **lobe** **functions**.
1. Constriction Ability (non-dominant hemisphere)
2. Body Image
32
What happens if you get a **body** **image** **lesion**?
* **_Right_** **Hemisphere** usually
* Can **lose** **part** of your **body** **image**
* Lose ability to recognise the **left** **side** of your **body** **as your own**
* Allows you to know when you will **fit** **through** **something**
Also important for **men** & **women** who think they are **too** **big** or **small**
33
What happens if the **somatosensory** **cortex** is **stimulated**?
* **Tingling** **sensation** on **contralateral** **side** of the body
*
34
What is the **protrusion** found on the **somtosensory** **area** called?
* **Somatosensory Hand Knob**
* Visible on **MRIs**
(Equivalent to the hand knob in M1)
35
What areas does the **dominant** & **non-dominant** **parietal** **cortex** include?
* **Dominant** (usually left) --\> **LANGUAGE FUNCTIONS** (i.e. wenicke's area)
* **Non-Dominant** Hemisphere (usually right) --\> **CONSTRUCTIONAL** **ABILITY**
36
What are the effects of a **lesion** on the **parietal** **lobe** on the **non-dominant** **side**?
* Despite normal intelligence
* Subject will **not** be able to do a **3 piece jigsaw (child level)**
* **Lost construction ability**
**Construction** **centre** is **_more_** **developed** in **males** as they have a **more** **developed** **parietal** **lobe** which usually means they are **better** at **making** **things**
37
**What** is body image?
**Where** is it found?
* **Image of our own body**
* So we can **walk** **through** a **doorway**
* Recognise how **tall** & **wide** we are
* Found in the **_parietal lobe_**
If someone **loses ability to recognise own limb** --\> this is characteristic of **parietal** **lobe** **lesion**
38
Do most people have **bilateral** or **unilateral** strokes?
* **One side (unilateral)**
NB: Very unlikely if you get both sides at the same time
39
What is the difference between a **lesion** & **swelling**?
* **Swelling** --\> has a **similar** **effect** as a **lesion**
* It can affect parts of the **brain** but it will only be **temporary** (e.g. parietal lobe)
40
What is the **intra**-**parietal** **sulcus** important for?
* Area in Cerebral Cortex (parietal lobe)
* Important in **Arithmacy (sums)**
41
What happens when there is a **parietal** **lobe** **lesion** on the **right** **side**?
* **More** **common** in the **_right_** **parietal** **lobe**
* (left lobe usually affects broca's area too meaning they cannot tell you that they do not recognise their limb cause they cannot talk fluently)
* If **swelling** then can be **temporary**
42
Name **3 motor areas.**
1. **Primary Motor Cortex (M1)**
2. **Pre-Motor Cortex**
3. **Frontal Eye Field**
There are lots of cortex in frontal lobe which are not motor --\> thus called pre-frontal cortex --\> important in personality & behaviour & future planning & interaction with other people & future --\> this is **personality** (pyschologist find this important)
43
What happened to Phineas Gage?
* Metal Rod up his **Orbit**
* Destroyed **Prefrontal** **Cortex** **bilaterally**
* Completely changes **personality** & **future** **plans** & **people** **interaction**
44
What is **infront** of & **behind** the **central** **sulcus**?
* In Front --\> M1
* Behind --\> S1
45
What are the **areas** **in** **front** of the **main** **motor** **areas** (M1 & premotor)?
Which **lobe** is this?
* **Frontal Eye Field**
* **Broca's Area** (not motor but important inf luent speech)
This is in the **frontal** **lobe**
46
What is directly **in front** of the **primary motor cortex (M1)?**
* Premotor Area
47
What do **mirror** **neurones** do?
* **Electrically active** when performing the **same movement as someone** **else** who is also **doing** the **same movement** (i.e. copying)
48
Where are **mirror** **neurones** found?
1. Pre-Motor Cortex
2. Intra-Parietal Sulcus
3. Lower Part of Intra-Parietal Sulcus
NB: Exists in many parts of the brain thus is not very significant with neuroanatomists
49
Which condition may **mirror** **neurones** be involved in?
* Mirror Neurones
50
Where are the following found?
* Corpus Callosum
* Fornix
* Septum Pellucidum
51
Name the **4** **functions** the **cingulate** **gyrus** is involved in?
1. Nociception
2. Autonomic Control
3. Micturition
4. (Memory in Next Lecture)
52
What are the **effects** of a **cut corpus callosum**?
Does **agenesis** of **corpus** **callosum** in kids have the **same** **effect**?
* Almost **_No_** **Effect** on a **Patient** (maybe only in choosing clothes)
* **Agensis** in **Kids** --\> has a **big effect congenitally** --\> however if **cut later on** after brain formation if **complete** --\> there is **no** **big effect**
This is because if you **feed** **information** into the **right** **hemisphere** from the **left** **visual** **field** from **both** **eyes** they **cannot** **communicate --\>** thus patient could **not** tell you what was in their **left hemisphere** because they need the **sides** to **speak** to **each** **other**
53
In what situations is the **corpus** **callosum** **cut**?
* **Epilepsy**
* To **reduce** **fitting**
* Stops it **spreading** from **one** **hemisphere** to **another**
54
**Image** of the **cerebral** **arteries**
55
Generally where do the **anterior**, **posterior** & **middle** **cerebral** **arteries** go?
* **_Anterior_** --\> **Front** of the **Hemisphere**
* **_Posterior_** --\> **Back** of the **Hemisphere**
* **_Middle_** --\> **Sides** of the **Hemisphere**
56
What is the problem with **joints** & **movements**?
* **Movement of Joints** --\> causes **temporary** **occlusion** of **blood**
* **Anastomoses/collaterals around joints** --\> allows **constant** **perfusion** (important in the brain)
Thus anastomoses ensures **perfusion** even if there is a **reduction** of **blood** **flow** to **one** of the **arteries**
57
What is the **circle of willis**?
* Forms **anatomoses** at the **base of the brain**
* Forms this from **_internal carotid_** + **_vertebral (basilar) artery_**
* This allows for **constant** **blood** supply despite **movements** **of** **joint**
58
How does the **internal** **carotid** contribute?
* Comes out of the **cavernous** **sinus**
* Forms **_anterior_** & **_middle_** **cerebral arteries**
* (**Middle** **cerebral** **artery** goes into the **lateral** **fissure** between the **frontal** & **temporal** lobes)
59
What does **MRI** **work** on the **basis** of?
* Basis of blood flow changes
* However this occurs very slightly
* Brain is generally well perfused all the time
60
**Where** does the **middle** **cerebral** **artery** go?
* Comes from the **circle** of **willis** (lots from internal carotid)
* **Runs** **along** the **lateral fissure**
NB: Not seen unless you open up lateral fissure
61
What areas does the **middle** **cerebral** **artery** supply?
* **Somatosensory Cortex**
* **Motor Cortex**
(These include hand areas)
* **Language Centres (only on _dominant/left_ side)** --\> including broca's & burner's area
* Covers the **majority** of the **_lateral_** **surface** of the **hemispheres**
* Does **_not_** quite reach the **front** & **back** & **ring** **around**
62
What are the **signs** of a **middle** **cerebral** **artery** lesion?
Paralysis of **contralateral** **_upper_** **limb** (remember lower limb is medial side not lateral)
* **Problems** with **language** **centres** (e.g. **fluent** **speech**) - if lesion on left/dominant side
* **Face** **Muscles** (these are controlled by both sides of the brain)
63
Where does the **_anterior_** **cerebral artery** go?
* Around the **Corpus** **Callosum**
64
What does the **Anterior Cerebral Artery (ACA)** generally supply?
What effects would you see?
* **Medial** **Surface** of the **Frontal** **Lobe**
* **Paracentral Lobule (lower limbs)** - thus motor & somatosensory cortex for lower limb
* Region around the **central** **sulcus**
**ACA lesion** --\> causes **paralysis** of **lower** **limb**
65
Where does the **posterior cerebral** **artery** go?
* **Deep** into the **calcarine** **sulcus**
66
What does the **posterior** **cerebral** **artery** supply?
* Primary Visual Cortex (V1)
67
What happens if there is a **lesion** of the **posterior** **cerebral** **artery**?
* **Lose** the **Contralateral** **Visual** **Field** from **_Both_** **Eyes**
68
Where is the division between the **Anterior** & **Posterior** **Cerebral** **Artery** blood supply?
Do they supply them **medial** or **lateral** side?
* Medial Side
69
What are the effects of a **lesion** in the **occipital** **lobe**?
* **Cortical Blindness**
* Unable to see the **_contralateral_** **visual** **field** from **_both_** **eyes**
70
What is a **consequence** of a **berry** **aneurysm**?
* Potentially death
71
What are **two** ways of **treating** **cerebral** **aneurysm**?
* **Coil** --\> via a canula a COIL which is placed into ANEURYSM --\> which forms a CLOT
* **Clip** --\> this is places onto the NECK of the ANEURYSM
**NB:** Clip requires drilling into the brain whereas coil does not
72
Which **cerebral** **aneurysm** **treatment** is associated with a **quicker** **recovery**?
* Treat from **_Inside_** the **blood** **vessel**
* Patient gets better **much** **more** **quickly**
Drilling through the head causes a much **bigger** **effect** & **larger** **surgery**
**Endovascular methods are better**
73
What is the result of a **ruptured** **berry**/**cerebral** **aneurysm**?
* Blood in CSF
* Subarachnoid Haemorrhage
74
Where are **cerebral** **aneurysms** usually found?
* Circle of Willis
75
What are the **3 brain changes** associated with **ageing** but **even more profound** in **alzeihmers**?
* **Gyri** --\> SHRINK
* **Sulci** --\> EXPAND
* **Vesicles** --\> EXPAND (get larger)
This is due to loss of neurones from the brain
**Beta-Amyloids** --\> are involved in **alzheimers** as **mutations** give rise to **familial alzeheimer's disease**
76
77
What is the importance of **cholinergic** **supply** to the **cerebral** **cortex**?
* **Increases** the **level of the activity** in the cortex
* Does **_not_** **convey** **specific** **information**
* **Increases** **activity** generally allowing for **faster thinking**
78
Where does the **cholinergic** **supply** **go**?
What **2 nuclei** supplies **cholinergic** **fibres**?
1. Neocortex
2. Hippocampus (temporal lobe)
1. **Septal Nuclei**
2. **Basal Nucleus of Meynert**
79
What happens to **cholinergic** **nuclei** in **Alzeihmer's** **disease**?
Effects?
* **Degenerate early & rapidly**
* Early cognitive deficits
80
What is the current only **treatment** for Alzheimer's?
What does the drug do?
* **Anti-Cholinesterase Drugs**
* **Inhibits ACh Breakdown** in Cerebral Cortex
* This gives **temporary** **effects** on **cognitive** **function**
* Due to **_increased_** **ACh levels** in the **cerebral** **cortex**
**NB**: Alzheimer's is associated with low levels of ACh in the cerebral cortex due to loss of cholinergic neurones lost over time
Fast Brain Processing --\> needs **GOOD** & **HIGH** LEVELS of ACh
81
What is found **_below_** the **Nucleus** **Basalis** of **Meynert**?
* Anterior Perforated Substance (holes in it)
Lateral to Optic Chiasm
* Above it is the Nucleus Basalis of Meynert (ACh)
82
What are the **basal** **ganglia**?
* **Nuclei** **deep** in the **brain** with **_motor_** **functions**
83
What **diseases** are involved in **degeneration** of certain parts of the **basal** **ganglia**?
What **condition** do they give rise to?
* **Huntington Disease**
* **Parkinson's Disease**
(problems with motor function)
Dyskinesia
84
What **basal** **ganglia** is associated with **Parkinson's** **disease**?
Where is this found?
* Substantia Nigra Degeneration
* Midbrain
85
What **basal** **ganglia** **degeneration** is associated with **Huntington's** **Disease**?
* Striatal Degeneration
Striatum/Neostriatum = Putamen + Caudate Nucleus
86
What **basal** **ganglia** **degeneration** is involved in **Hemiballismus**?
* Subthalamic Nucleus **_Lesion_**
87
**Coronal** **section** of the **basal** **ganglia**.
88
What **2 parts** make up the **lentiform** **nucleus**?
1. **Putamen**
2. **Globus Pallidus** (internal & external segments)
89
What **2 parts** make up the **neostriatum / striatum**?
1. **Putamen**
2. **Caudate Nucleus**
90
What are the signs & symptoms of Parkinson's disease?
* Lots of **difficulty intiating movements**
* **Resting Tremor**
* **Mask-like face** (due to lost emotional control over facial muscles however it can be done voluntarily)
* **Demented** **after 10-20 years**
91
What is the **sign**/**effect** of **huntington** **disease**?
* Too many movements
92
Where is the **subthalamic** **nucleus**?
What happens when it **degenerates**?
* **Small** **Nucleus** found **under** the **Thalamus**
* **Degenerates** --\> causing **Hemiballismus**
* Causes **jerky movement** (e.g. jerky cricket ball movement)
93
Where are the **basal** **ganglia** found?
* **Most** --\> Forebrain
* **Substantia Nigra** --\> Midbran
94
Image of the **corpus** **striatum**.
95
What is the **nucleus** **accumbens**?
* **Limbic** **region** of the **striatum**
96
Where does **cocaine** have an effect on?
What is the effect there?
What does it do?
* Nucleus Accumbens
* **Raises dopamine levels** (part of reward pathway)
* Lots of **addictions** involve nucleus accumbens
* Responsible for connections between **memory** & **emotion**
**NB**: Usually emotional memory is difficult to forget
97
Where is the **putamen** found?
* Big Basal Ganglia
* **Middle of the Hemisphere**
98
What is the **size** & **shape** of the **caudate** **nucleus**?
Where is it found?
* Has a **tail**
* **Large Head**
* **Continuous** **_anteriorly_** with the **putamen** (forming striatum)
99
What are the **basal** **ganglia** **separated** by?
* **White Matter**
* However they **look** **like** **1 structure**
100
What is found at the **end** of the **tail** of the **caudate** **nucleus**?
Where does the tail go? (which lobe)
* **Thin tail**
* Goes into the **Temporal** **Lobe**
* **Ends** at the **Amygdala** (not part of basal ganglia)
101
What is the **amygdala**?
* It is **_not_** **part** of the **basal** **ganglia**
* **Important** & **old** part of the brain
* Besides **olfactory cortex (uncus)**
* **Controls** lots of **emotions**
* **Processes** **pain** & **memory**
**NB**: Close proximity of **uncus** & **amygdala** may mean you are **emotionally** **connected** with the things you **smell**
102
What are the effects of a **bilaterally** **ablated** **amygdala**?
* Placidity
It usually causes **fear** & **anger** when stimulated
103
Where is the nucleus accumbens found?
* **Ventral** to (large) **caudate nucleus**
* **Limbic** **part** of the **corpus** **striatum**
104
What does the **amygdala** do?
* **_Not_** part of **basal** **ganglia**
* **Nociceptive Inputs**
**Notable connections with:**
1. Hippocampal formation (memory)
2. Dorsomedial thalamus
3. Medial prefrontal cortex
Basolateral Nucleus of the Amygdala --\> largest division --\> key role in attaching emotional significance to a stimulus
**Outputs** include **fibres** passing to the **cerebral** **cortex** - including:
1. Limbic Association cortex
2. Hippocampus
3. Prefrontal Cortex
105
What part of the **lateral** **ventricle** is separated by the **septum pallucidum**?
* **Anterior** **Horn** of the **Lateral** **Ventricle**
106
What is the **shape** of the **3rd ventricle** and what is found **either** **side**?
* **Narrow Slit**
* **Mid-line**
* **Thalamus** is **either** **side**
107
What is the **cortex** **buried** in the **lateral** **fissure** called?
* Insular Cortex
108
What is found **deep** to the **insular** **cortex**?
* Basal Ganglia
109
What **bulges** into the **anterior** **horn** of the **lateral** **ventricle**?
* **Anterior** **Head** of the **Caudate**
110
Is the globus pallidus **pale** or **dark**?
* Pale region
111
What are the **different** **areas** of this **_horizontal_** **plane**?
112
What are the different sections of the **internal** **capsule**? (axial/horizontal sections)
NB: Internal capsule is white matter
113
What does the **posterior** **limb** of the **internal** **capsule** carry?
* **Motor** **fibres** for the **contralateral** **side** of the **body**
114
What makes up the **internal** **capsule**?
* White matter
* Makes up the **anterior** & **posterior** **limb**
* These contain **fibres** which go between the **_cerebral cortex_** & **_lower part of the brain_**
The majority of fibres going **to** & **from** the **cerebral** **cortex** are found in the **internal** **capsule**
115
What **pathways** does the **posterior** **limb** carry?
Where do they go?
1. Corticospinal Tract
2. Corticobulbar Tract
They go to the **brainstem**
116
What does the **anterior** **limb** do?
* Connects the **_thalamus_** & **_pre-frontal cortex_**
This is associated with 'worrying'
117
What happens if there is a **blood** **vessel** **lesion** in the **posterior** **limb**?
* Paralysis on Contralateral Side (motor)
118
What is found **_directly_** **deep** to the **insular** **cortex**?
What is it **associated** with?
* **Claustrum**
* **Associated** with **consciousness**
* **Claustrum** is **connected** to the **rest of the cerebral cortex**
119
What occurs in a **capsular** **stroke**?
* **Posterior Limb** --\> contains **_all_** **descending** **motor** **fibres** coming from **cerebral** **cortex**
* Therefore a **small** **lesion** in **posterior** **limb** can **destroy** **_all_** **motor fibres** going to **contralateral** **side** of the **body** causing **paralysis**
120
What usually causes a **stroke**?
* Thrombi --\> i.e. blocked blood vessels (rather than bleed/haemorrhage)
121
Name this **coronal** **brain section**.
NB: Remember the **internal** **capsule** is **deep** to the **insular** **cortex** (which is found deep in the lateral fissure)
Section taken at **frontal** **lobes** at the **level** of the **anterior** **limb**
122
Name the 2 structures that are pointed at.
Which part of the internal capsule is this?
* Putamen + Globus Pallidus
* **The Genu (a bend)**
123
Name the structures pointed at.
Which level is this at?
* Level of **posterior** **limb** of the **internal** **capsule**
124
Diagramatic section of the basal ganglia
125
Is the input from the **cerebral** **cortex** to the **striatum** excitatory or inhibitory?
* **Excitatory**
NB: All the output is excitatory
126
What is the **green** arrow pointing towards?
* Posterior Limb
127
What is the green arrow here pointing to?
What is it found between?
What is the space above called?
* Green Arrow --\> **3rd Ventricle**
* Found **between** the **Thalamus**
* **Above** it is the **Lateral** **Ventricle**
128
What 2 structures make up the **striatum** (aka. **neostriatum**)?
1. Putamen
2. Caudate Nucleus
129
What 2 structures make up the **lentiform** **nucleus**?
* Putamen
* Globus Pallidus
130
Where do the neurones from the **cerebral** **cortex** go to in the **basal** **ganglia**?
* **Corpus Striatum/Neostriatium/Striatum**
This includes:
1. Putamen
2. Caudate Nucleus
NB: **Striatum** gets a lot of **excitatory** **input** from the **neocortex**
**NB:** Information comes via the inner capsule
131
Is the **_output_** from the **striatum** to the **globus** **pallidus** excitatory or inhibitory?
* **Inhibitory**
**NB**: All output from the **striatum** is **inhibitory (GABA)**
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What type of neurones are found in the **striatum**?
* Medium Spiny GABAergic Projection Neurones
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Where in the basal ganglia does the main output come from?
Are these inhibitory or excitatory?
Where do they pass to?
* Globus Pallidus
* Inhibitory
* Thalamus
NB: Sends inhibitory fibres from the Globus Pallidus to the Thalamus
134
Are the fibres from the **thalamus** to the **cerebral** **cortex** inhibitory or excitatory?
What effect does the **Globus** **Pallidus** have on the **thalamus**?
* **Excitatory**
Therefore the Globus Pallidus action on the thalamus is to inhibit these excitatory neurones thus reduce action in Thalamus
This will reduce excitation in M1 --\> reducing movement
135
What does the **direct** and **indirect** pathway generally do in terms of movement?
* **Direct** Pathway --\> Increases Movement (start movement)
* **Indirect** Pathway --\> Decreases Movement (stop movement)
136
What **2 other nuclei** does the **_indirect_** pathway involve?
1. Globus Pallidus External Segment
2. Subthalamic Nucleus
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What is the **role** of the **striatum**?
* Striatum has a **lot** **of** **programs** for **different** **desired** **movements**
* **Striatum** decides on a **program of activity**
* There are **competing** **programs** of **activity** which can **produce motor functions**
* One of these programs are needed to **produce** the **desired movement** the cortex wants
138
Learn the following diagram and try to memorise it off by heart.
139
What does the **thalamus** do?
What does **disinhibition** of the **signals** **to** **the** **thalamus** do? (Direct pathway)
* **Thalamus** --\> **continuously** sending **excitatory** signals to the cerebral cortex
* **Disinhibition** of the **signals to the thalamus** will allow the **thalamus** to **fire** **more** --\> therefore **increase excitation to M1**
140
Where does the direct pathway work through?
* **Internal Segment of the Globus Pallidus** (directly)
141
What does the **thalamus** generally do?
What does the **direct** **pathway** do to the **thalamus**?
* **Activates motor cortex**
* **Disinhibits** the **thalamus**
**NB:** Thalamus is constantly sending signals to the cortex to excite it
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What does a lesion/degeneration of the **subthalamic** **nucleus** cause?
* Hemiballismus
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What is the **overall** **effect** of the **indirect** **pathway**?
* **Inhibition** of the **Thalamo-Cortical Fibres**
* **Reduction** of Movement (stop)
The more you **inhibit** the **thalamus** --\> the **less** **excitation** of the **motor** **cortex** you get
144
What are the arrows pointing at?
145
What structure degenerates in **parkinson's** **disease**?
* Substantia Nigra
146
What are the **2** **parts** of the **substantia** **nigra**?
1. Pars Compacta (parkinson's)
2. Pars Reticulata
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When do you start seeing **symptoms** associated with **Parkinson's** **disease**?
* When **70% or more** of the **dopaminergic** **neurones** in the **substantia** **nigra** die
148
Give **3 symptoms** that are seen in **parkinson's** **disease**.
* **Resting Tremor**
* **Difficulty** **Initiating** **movement**
* **Mask-like face**
149
Other than Parkinson's disease, what **2 other ways** can cause **destruction** of the substantia nigra.
* MTPT Toxicity (drug)
* Week Killers
150
What is the **overall effect** of the **substantia** **nigra (dopamine)** on movement?
What is the effect on the **indirect** & **direct** pathways?
* **Overall** **Effect** --\> promote the likelihood of producing movement
Effect on **Direct** Pathway --\> Increase Activity
Effect on **Indirect** Pathway --\> Decrease Activity
**NB**: Both the direct & indirect pathways are affected by dopaminergic neurones
151
What is this a section of?
* **Midbrain**
152
What does **MTPT (amphetamine)** do?
* **Complete paralysis (cannot move)**
* Loss/death of the substantia nigra
* Basically induced parkinson's disease
* Complete rigidness
NB: Used on animals to test parkinson's drugs on them
153
From where exactly is **dopamine** released in the **midbrain**?
* Substantia Nigra Pars Compacta
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What is the effect of **dopamine** from the **substantia** **nigra**?
* **Excite** the **Direct** **Pathway**
* **Inhibit** the **Indirect** **Pathway**
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What is the **general** **role** of the following in **movement**?
* Cerebral Cortex
* Basal Ganglia
* Motor Cortex
* Cerebellum
* **Cerebral Cortex** --\> decides on the movement that it wants to produce
* **Basal Ganglia** --\> selects the program & inhibits other programs
* **Motor Cortex (M1)** --\> executes the motor program
* **Cerebellum** --\> corrects errors in the movement & sends information to thalamus (then to M1)
156
What does the **direct** & **indirect** pathway finally exert its action on?
* **Thalamus**
This then affects the **Motor Cortex**
157
What happens when there is a **lack** of **dopamine** (e.g. parkinson's)?
* **Hypokinetic Disorder** (difficulty moving)
158
Give **2 forms of treatment** for **Parkinson's** **disease**.
* Deep Brain Stimulation
* L-DOPA
159
Where is the **electrode** for deep brain stimulation for **Parkinson's disease** placed?
* Subthalamic Nucleus
160
How does **deep brain stimulation (DBS)** work?
* **Electrode** placed down through the brain
* Placed on **either side** for each **subthalamic nucleus**
* Using an **appropriate** **frequency** of **stimulation** they are stimulated
* They work as a **'depolarising block' mechanism** (over depolarising them so they cannot fire)
* They effectively **block** the **indirect** **pathway**
NB: Safe mechanism
The pattern frequency can be adjusted to alleviate the symptoms by turning it up or down (on/off) using external button
161
What **nucleus** **bulges** into the **lateral** **ventricle**?
* Caudate Nucleus
162
How else can you treat Parkinson's disease?
* **Burn** **out** the **subthalamic** **nucleus**
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How does **L**-**DOPA** tratment work for **Parkinson's** **disease**?
Why not give **dopmine**?
How long is the treatment good for?
* L-DOPA is the precurdor of Dopamine
* Replenish the deficit of dopamine in the brain by giving L-DOPA
* Dopamine itself cannot pass blood-brain barrier
* Treatment is good for around 5 years
* After --\> effects are lost --\> need higher dosage
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What is the problem with **high** **dosages** of **L-DOPA**?
* They can give **squermy** **side** **effects**
Patients end up choosing between inability to produce movements or movements where they cannot fully control it
* Uncontrollable Movements (diskinesis)
This gives rise to **athetoid** **movement** (uncontrollable writing movements) when drug is taken
165
What is the **blood** **supply** to the **_posterior_** **limb** of the **internal** **capsule** (white matter next to basal ganglia)?
Where do they pass through to do this?
* **Striate** **Arteries** from the **Middle** **Cerebral** **Artery**
* **Anterior Perforated Substance**
166
Where is the internal capsule?
What does the internal capsule do?
* Found **among** the **basal** **ganglia**
* It is **white** **matter** where **tracts run through it**
* It is the main pathway **to** & **from** the **cerebral** **cortex** (connecting it to the body & brainstem)
167
What fibres are found in the **posterior** **limb** of the **internal** **capsule**?
* All the **motor** **fibres** that control the **contralateral** **side** of the **body**
168
What 2 areas are invovled in motor fibres?
* Putamen
* Thalamus
169
Where are the **striate** **arteries** found?
What can happen to them?
What is the effect?
* **Base of the Brain**
* They are **narrow** & **thin** vessels
* They can be **easily** **blocked** by a **thrombus** (common)
* This causes a **lesion** in the **posterior** **limb** of the **internal** **capsule**
* This will destroy **descending** **motor** **fibres** destined for **contralateral** **side**
170
Where does the **blood** **supply** for the **thalamus** come from?
* **Posterior** Cerebral Artery
NB: Thalamus is **not** supplies by striate artery (MCA)
171
Where can the **middle** **cerebral** **artery** be found?
* Lateral Fissure
172
Describe the course of the **MCA** from the beginning (including its source).
* **Internal Carotid Artery** --\> becomes the Middle Cerebral Artery
* Winds around the **stem** of the **lateral** **fissure** (not go through the middle of the brain)
* Goes **around** the **brainstem**
* Gives off **fine hair-like branches (striate arteries)** --\> these go to the **base** of the **brain** (striatum & posterior limb supplied)
* Goes down the **lateral** **fissure**
173
What **2 things** does the **striate** **arteries** supply?
Which **cerebral** **artery** supplies it?
1. **Corpus Striatum** (Neostriatum = Striatum)
2. **Posterior** **Limb** of the **Internal** **Capsule**
174
Why are **striate** **arteries** vulnerable?
* **Fine Vessels**
* Come up at **right** **angles** from the **stem** (at brain base)
* Usually **blocked** due to **thrombus** or **bleed**
175
What is the **condition** associated with a **lesion** of the **posterior limb of the internal capsule**?
* Hemiplegic Stroke
Paralysis on the contralateral side of the body
176
177
What type of scan can show you where dopamine is found?
What kind of person will have a lot of dopamine in their brain?
* PET Scan
* Cocaine Patient
178
What is the **limbic** **part** important for?
**Where** is it found?
* **Addictive Behaviour**
* **Nucleus Accumbens**
NB: Cocaine can affect the limbic part a lot
179
Name the following arrowed structures.
180
What is the effect of cocaine on the brain?
* **Activation** of **dopamine** **receptors**
* These are active in the **nucleus** **accumbens** (limbic part of the striatum)
NB: **Limbic** **part** of **corpus** **striatum** is important in **addictions**
181
**Where** is the **nucleus** **accumbens** found?
Which part of the **thalamus** does it project to?
Which part of the **cortex** does this project to?
* **Ventral** to **Septum** **Pallicidum**
* Projects to **dorsal-medial thalamus** (then pre-frontal cortex)
182
What **2** **characteristics** is the **pre**-**frontal** **cortex** important for?
* Personality
* Emotion
183
What is the **nucleus** **accumbens**?
* Limbic Part of the Striatum
184
What does the **ventral** **tegmental** **area** do?
* **Dopaminergic** **nucleus** for the **nucleus** **accumbens** (limbic part of striatum)
**NB**: This projects to the **thalamus** then **pre-frontal cortex**
**NB:** Important pathway for pyschologists & pyschiatrists
185
186
What are the more widespread & less known effects of Parkinson's disease in the brain?
Dopaminergic Neurone death in:
* **Substantia Nigra Pars Compacta**
* **Ventral Tegmental Area**
Other Monoaminergic Neurones involved too:
* **Locus Ceralias (NA)**
187
What are the effects of **degeneration** of **locus** **ceralias** in **Parkinson's**?
* **Widespread fibres** (go all over the brain)
* **Modulate** **activity** in **all parts** of the **brain**
* Affect **cognition** (due to widespread distribution & control of synaptic activity)
* **Loss of speech** too
188
What is the cause of Parkinson's Disease?
* Genetic
* Environmental
NB: Can be affects environmentally due to things like pesticides which kull dopaminergic neurones
NB: Smoking has a good effect of parkinson's but bad on alzeihmer's
189
**Label** this **diagram** of the **midbrain**.
190
What is the **ventral** **tegmental** **area** and **what** **does** **it** **do**?
* Another **dopaminergic** **nucleus**
* **Sends** **axons** to the **nucleus** **accumbens**
