HNS05 Thalamus And Cerebral Cortex Flashcards
Thalamus
- Large ovoid mass of gray matter —> forms major part of Diencephalon
—> Anterior end: narrow, rounded
—> Posterior end: expanded to form the Pulvinar - Situated on each side of ***Third ventricle (將Third ventricle夾係中間)
- 2 halves of thalamus joined by ***interthalamic adhesion
- very important RELAY station of most sensory systems
Topographic location of thalamus
Anterior: Interventricular foramen
Posterior: Pulvinar
Superior: Stratum zonale (White mater) and Stria terminalis
Inferior: Tegmentum of **midbrain
Medial: Lateral wall of **third ventricle
Lateral: Nerve fibres of ***internal capsules
Topological location of Thalamus
Dissection from lateral side has to go through Caudate nucleus and Putamens
Dorsal view of Diencephalon and Mesencephalon
兩邊Thalamus夾住中間下面Mesencephalon (見到Superior and Inferior colliculi)
Coronal sections for Diencephalon
see slides
***4 components of Diencephalon
- Epithalamus
- **Pineal gland: secretes **melatonin
- smallest region of diencephalon - Thalamus
- relays **ALL sensory input (perception of touch, pressure, temperature) to all parts of cortex
- **movement control - Subthalamus
- connects Subthalamic nuclei + Basal ganglia (Caudate nucleus + Putamen + Globus pallidus)
—> control body movement and emotion control - Hypothalamus
- **release hormones to regulate **Pituitary gland
- controls body ***temperature
- eating and drinking behaviour
- emotion
- circadian rhythms + wake/sleep pattern
***Thalamic nuclei
Left/Right connected by interthalamic adhesion
Groups separated by internal / external medullary lamina
Anterior group:
- part of ***limbic system
- **memory and **emotion
Medial group:
- **emotional output to **prefrontal cortex
- awareness of emotions
- subgroups: Medial dorsal (MD), Medial group (M), Midline nuclei
Ventral group:
- **somesthetic output to **postcentral gyrus
- signals from Cerebellum and Basal nuclei —> ***motor areas of cortex
- subgroups: VA, VL, VP (VI+VPM+VPL)
Lateral group:
- **somesthetic output to **association areas of cortex
- contributes to ***emotional function of limbic system
- subgroups: LD, LP
Posterior group:
- relay of **visual signals to occipital lobe (via **lateral geniculate nucleus)
- relay of **auditory signals to temporal lobe (via **medial geniculate nucleus)
Internal medullary lamina
Intralaminar nuclei + Centromedian nuclei
***Anterior, VA, VL, VP, Lateral geniculate, Medial geniculate, MD
(Receives signals FROM, Send signals TO)
Learning and Memory:
- Anterior (part of Limbic system):
- from Mammillothalamic tract, Fornix (learning, memory) —> ***Cingulate cortex (posterior part)
Emotion:
- MD:
- from Substantia nigra, Ventral pallidum, Olfactory cortex, Amygdala —> ***Prefrontal cortex
Motor:
- ***VA:
- from Globus pallidus —> Prefrontal cortex (motor) - ***VL:
- from Globus pallidus —> Supplementary motor area
- from Cerebellum —> Motor cortex
Sensory:
- ***VP (most important):
- from Spinothalamic tract, Trigeminothalamic tract, Dorsal column-medial lemniscus pathway —> Somatic sensory cortex - ***Lateral geniculate:
- from Optic tract —> Primary visual cortex - ***Medial geniculate:
- from Inferior colliculi —> Primary auditory cortex
VP nucleus
- VPL: receives all somatosensory signals from ***upper + lower extremities (Dorsal column-medial lemniscus pathway + Spinothalamic tract)
- VPM: receives all somatosensory signals from ***head + neck region (Trigeminothalamic tract)
(Somatosensory signals: Mechanoreception + Proprioception + Thermoception + Nociception)
***Functions / Roles of Thalamus in neuro-network
***ALL sensory signals (from Spinothalamic tract + Dorsal-medial lemniscal pathway) has to go through thalamus, but NOT motor control
Sensation:
Example: Pain sensation:
Sensation —> Dorsal horn —> Spinothalamic tract —> Medulla, Pons, Midbrain —> **Thalamus (form synapse) —>
1. **Learning and memory cortex (avoid pain sensation in the future again)
2. ***Sensory cortex (Parietal lobe) —> Motor cortex —> Corticospinal tract —> Brainstem (Cerebral peduncle, Pyramid) —> Ventral horn
Motor control:
1. Corpus striatum, Diencephalon, Cerebellum
—> ***Thalamus
—> Cerebral cortex
—> go straight back to Corpus striatum, Diencephalon, Cerebellum
2. Brainstem, Spinal cord —> ***Thalamus —> Cerebral cortex —> go straight back to Brainstem, Spinal cord —> Muscle
Involvement of Thalamus in Basal Ganglion circuit
Thalamus: modulate eventual motor output (NOT a part of basal ganglia)
Basal ganglia: Fine tuning of motor movement (finger movement, gait)
Basal ganglia components:
- Striatum
- Globus pallidus
- Subthalamic nucleus
- Substantia nigra
Direct pathway: Cortex —(glutamate)—> Striatum —(more GABA)—> Globus pallidus (internal segment) —(less GABA)—> Thalamus (VL) —(more glutamate)—> Supplementary motor area
Indirect pathway: Cortex —(glutamate)—> Striatum —(more GABA)—> Globus pallidus (external segment) —(less GABA)—> Subthalamic nucleus —(more glutamate)—> Globus pallidus (internal segment) —(more GABA)—> Thalamus (VL) —(less glutamate)—> Supplementary motor area
***Balance between direct / indirect pathway go to Thalamus eventually
—> control motor area
Substantia nigra:
- release dopamine (inhibitory/excitatory) —> Striatum
- fine tuning of direct / indirect pathway
Compacta:
- also fine tuning of direct / indirect pathway
Cerebral cortex / Telencephalon
凸起: Gyrus
中間d隙: Sulcus
Components:
- Frontal lobe (***motor control + emotion, also receives input from thalamus to tell how good motor control is)
- Parietal lobe (ultimate analysis of ALL ***sensory signals from thalamus)
- Occipital lobe (***vision centre —> primary visual cortex)
- Temporal lobe (**learning, **memory, emotion)
Central sulcus: separate frontal / parietal lobe
—> gyrus in front (Precentral gyrus): Primary motor cortex
—> gyrus behind (Postcentral gyrus): Primary somatosensory cortex
Frontal lobe
- Primary motor cortex (Area 4)
- Motor association area (Area 6: Premotor area + SMA)
- Pre-frontal cortex
- ***Broca’s area (language area)
(5. Olfactory association area)
Occipital lobe
- Primary visual cortex
2. Visual association area
Temporal lobe
- Primary auditory cortex
- Auditory association area
- Primary olfactory cortex
Parietal lobe
- Primary somatosensory cortex
- Somatosensory association area
- Primary gustatory cortex (taste)
- ***Wernicke’s area (comprehension of language)
Grey matter
Collection of Cell bodies
- Insula (physio, psychological pain, olfactory sensation) (enclosed within other gyrus)
- Caudate nucleus + Putamen —> Striatum
- Basal ganglia (Globus pallidus, Substantia nigra)
Broca’s area + Wernicke’s area
joined by ***Arcuate Fasciculus (several axons grouped together)
—> from Wernicke’s area (Parietal lobe) to Broca’s area (Frontal lobe)
Fibres of white matter of Cerebrum
- Arcuate fibres (最短)
- interconnect gyri within a lobe - Association fibres
- interconnect cortical areas within same hemisphere / linking several gyri together - Longitudinal fasciculi (前後)
- interconnect frontal lobe with other cerebral lobes - Corona radiata (上下)
6 layers of cortex
- Molecular layer
- External granular layer
- External pyramidal layer
- Internal granular layer
- Internal pyramidal layer
- Multiform layer
Differ in distribution of neurons
Different staining methods
- Golgi stain: cell bodies + axons
- Nissl stain: cell bodies only
- Weigert stain: axons only
Corpus callosum
Connect left + right hemisphere
Learning and memory
- Limbic system
- Basal nucleus of Meynert
- Septal nucleus (headquarter of cholinergic neuron to pre-frontal cortex)
***Limbic system
Learning + Memory + Emotion
Diencephalon components:
- ***Anterior group of thalamic nuclei
- ***Hypothalamus
- Mamillary body
Cerebrum components:
- ***Cingulate gyrus
- ***Hippocampal formation (Hippocampus + Dentate gyrus + Subicular complex)
- Parahippocampal gyrus
- Entorhinal cortex
Other components:
- Fornix + Fimbria
- ***Amygdala (negative emotion)
***Learning loop (Papez circuit)
Repeated stimulation of Hippocampus:
Cingulate gyrus —> Parahippocampal gyrus —> Entorhinal cortex —> Hippocampus (Dentate gyrus) —> Fimbria —> Fornix —> Mamillary body (of Hypothalamus) —> Mammillothalamic tract —> ***Anterior nucleus of Thalamus —> Cingulate gyrus (posterior) —> Parahippocampal gyrus —> Hippocampus
(—> Cingulate gyrus (anterior) —> Basal nuclei —> Occipitofrontal nucleus —> Subcallosal area of cortex)
Amygdaloid complex
Amygdala + Stria terminalis
Anterior to Hippocampus
Functions:
- Involve in defence and attack, fear, rage (***negative emotions)
- Influence ***endocrine function of hypothalamus
Hippocampal formation
Entorhinal cortex (within Parahippocampus gyrus) —> sends signals to Dentate gyrus (within Hippocampus)
Functions:
- ***Learning, recent memory
- ***Emotion
***Summary of memory
Long term memory
- Explicit memory (declarative): **Hippocampus, **Nucleus Basalis, Medial temporal lobe
—> Remembering events (episodic memory)
—> Remembering facts (semantic memory) - Implicit memory (non-declarative)
—> Skills and habits: **Striatum, Motor areas of cortex, Cerebellum (muscle memory)
—> Emotional associations: **Amygdala, Insula
—> Conditioned reflex: ***Cerebellum
Working memory: ***Prefrontal cortex (PFC)
—> Non-spatial (colour, shape): Ventrolateral PFC
—> Spatial memory: Dorsolateral PFC
Clinical relevance of cerebral cortex
- Alzheimer’s disease
- shrinkage / atrophy of whole brain, enlarged lateral ventricle
- start with Hippocampus —> temporal lobe: affect memory, language - Frontotemporal lobe dementia
- atrophy of frontal lobe - Creutzfeldt-Jakob disease
- prion change brain protein to beta-sheet —> neuron die
- vacuoles / holes formed in the cortex
- affect mental acuity + memory (limbic system)
