Week 9 Neuro

• The thalamus is the largest part of the diencephalon, making up about 80% of it.
• It is an egg-shaped structure situated above the brainstem in the middle of the brain.
• The thalamus looks like just one structure, it is actually made up of two halves, with one in either hemisphere.
• The two halves are connected across the third ventricle via the interthalamic adhesion.
• It is a hub with nerve fibers connecting it to other brain regions
• Located deep within the brain, below the thalamus and above the pituitary gland.
• It is organized into the anterior, medial dorsal, and lateral nuclear groups, divided by the Y-shaped intramedullary lamina.
• The reticular nucleus covers it and influences the other nuclei within it.

Thalamic Nuclei

• Consists of nuclei made up of excitatory neurons that project to the cortex
• Divided into relay, association, nonspecific, and reticular groups.

Relay Nuclei

• Transmit sensory information directly to the cerebral cortex.
• Examples:
  • Lateral geniculate nucleus (LGN) for vision
  • Medial geniculate nucleus (MGN) for auditory information
  • Ventral posterolateral (VPL) nucleus for somatosensory input

Association Nuclei

• Integrate sensory information from different areas of the cortex
• Projects it back to association areas.

Non-specific Nuclei

• Send projections to large regions of the cortex
• Involved in arousal and attention

Reticular Nuclei

• Modulates the activity of other thalamic nuclei by inhibiting them
• Acts as a gatekeeper, regulating the flow of sensory information to the cortex
• Plays a role in attention, arousal, and sensory processing.

Ventral Lateral Nucleus (VL)

• A key motor-related nucleus that relays information from the cerebellum and basal ganglia to primary motor cortex, premotor cortex, and supplementary motor cortices.
• The anterior part (VLa) is associated with proximal muscle control
• The posterior part (VLp) is associated with distal muscle control

Ventral Posterolateral (VPL) and Ventral Posteromedial (VPM) Nuclei:

• The VPL nucleus acts as a relay center for somatosensory information from the body (trunk and limbs) and projects to the primary somatosensory cortex.
• Receives signals from the spinal cord via the dorsal column medial lemniscus pathway and the spinothalamic tract
• The VPM nucleus relays sensory information from the head (face and head), receiving inputs from the trigeminal nerve (CN V) and projecting to the primary somatosensory cortex.

Medial Geniculate Nucleus (MGN) and Lateral Geniculate Nucleus (LGN):

• The MGN acts as the primary auditory relay station and projects to the auditory cortex in the temporal lobe
• The LGN serves as the primary visual relay station and sends projections to the primary visual cortex in the occipital lobe.

Thalamic Reticular Nucleus (TRN)

• Functions as a gatekeeper by inhibiting the activity of other thalamic nuclei
• Regulates the flow of sensory information to the cortex, and playing a key role in attention, arousal, and sensory processing

Corticocortical Communications

• The thalamus has reciprocal connections, projecting from the nuclei to the cortex and back
• It serves as a "pit stop" for these connections, helping sensorimotor integration through perceptions of sensation and guiding the motor system
• All thalamic nuclei, except the reticular nucleus, have reciprocal excitatory connections with the cerebral cortex

Clinical Implications of Thalamic Damage

• Sensory Changes:
  • Deficits.
  • Impaired facial sensation affecting touch, pain, and temperature.
  • Thalamic pain syndrome is a chronic pain condition marked by spontaneous contralateral pain
  • Burning, constrictive pain, allodynia, hyperalgesia, paresthesia, and temperature changes can occur.
• Motor Impairments:
  • Weakness, Ataxia or tremors and Impaired movements
• Cognitive and Behavioral Changes:
  • Memory loss, Aphasia, Cognitive changes, Difficulties with attention and Trouble processing sensory information
  • Mood changes or apathy can occur
• Other potential issues:
  • Vision changes, Speech and balance problems occur along with sleep disturbances
  • Potential unconsciousness and even permanent coma may manifest

Hypothalamus, Subthalamus, and Epithalamus

• All are components of the diencephalon.

Hypothalamus

• Serves as a "smart control" for the brain
• Located deep within the brain, below the thalamus and above the pituitary gland
• Sits above the brainstem
• About the size of an almond
• Is the main link between the endocrine system and nervous system

Subthalamus

• A small region of the brain located below the thalamus
• Plays a crucial role in regulating movement by modulating the activity of the basal ganglia
• The subthalamic nucleus is the main structure

Epithalamus

• Most dorsal, smallest, and oldest part of the diencephalon
• Lies posterior to the thalamus and forms the posterior part of the roof of the third ventricle
• Connects the limbic system to other brain areas
• It has the pineal gland, the habenular nuclei, and the stria medullaris

Functions of the Hypothalamus

• Maintains the body's balanced and stable state, known as homeostasis
• The main link between the endocrine and nervous systems, coordinating the autonomic nervous system and the pituitary gland's activity.
• Manages heart rate, blood pressure, and body temperature
• Regulates hunger, thirst, mood, sex drive, and sleep and releases hormones that direct other glands to manage bodily functions
• Produces dopamine neurotransmitter essential for smooth movements and attention
• Works with the pituitary gland and makes oxytocin and vasopressin in the posterior pituitary

Subthalamus Function

• Plays a crucial role in regulating movement by modulating basal ganglia activity
• Helps to fine-tune and coordinate muscle movements
• Has a rule in reward motivation, memory and regulation
• The subthalamic nucleus is important, and dysfunction is related to motor issues

Epithalamus Function

• Connects the limbic system to other brain areas
• The pineal gland secretes melatonin
• Habenular nuclei receive afferents from forebrain and project to the midbrain
• Stria medullaris connects habenular nuclei with other brain regions
• Regulates sleep, circadian rhythms, emotions, sensory integration, motor control, and endocrine functions

Hypothalamus Clinical Implications

• Dysfunction can result from head injuries, infection, tumors, surgery, chemotherapy, birth defects and genetic disorders
• Symptoms
  • Hypertension or hypotension, Water retention or dehydration
  • Weight loss or gain, Infertility
  • Poor bone health, Sleep disturbances
  • Delayed puberty and body temperature fluctuations
• Specific Disorders:
  • Disorders, Hypopituitarism, Diabetes insipidus, Prader-Willi syndrome, Kallmann syndrome,
  • Pituitary gigantism and Inappropriate antidiuretic hormone
  • Central hypothyroidism, Functional hypothalamic amenorrhea and Hyperprolactinemia

Subthalamus Clinical Implications

• Damage can result in motor dysfunction
• Damage can cause hemiballismus with sudden involuntary movements
• Dysfunction contributes to tremors and rigidity seen in Parkinson's
• The nucleus is targeted for deep brain stimulation to treat Parkinson's disease

Epithalamus

• Dysfunction is linked to mood disorders, schizophrenia, and sleep disorders

Limbic System Components

Amygdala

• Processing emotions like fear or pleasure
• Function: Helps in responding to emotional stimuli and linking emotions with memories
• Damage can impair recognizing emotions

Hippocampus

• Forming new memories
• Function: influences behavior
• Damage can result in memory loss

Hypothalamus

• Regulating bodily functions
• Function: Regulates bodily functions and influences emotions and the stress response
• Dysfunctions manifest hypertension, weight change, temperature fluctuations or trouble sleeping

Thalamus

• Directing sensory and motor signals
• Function: Is a regulator of functions
• Damage issues range weakmess, balance and sensory changes

Cingulate and Function

• Processing emotions and behavior
• Function: plays a role in empathy
• Damage impairs and effects interactions

Basal Gangila

• A group of nuclei located in the forebrain plays a role in movement, learning and various emotional functions

Functions of Components of Basal Gangila

• Regulating voluntary movement
• Integrating activity to ensure movements
• Collaborating integrating motivational stages
• Communication to direct behaviors

Components of Ganalia:

• Striatum: serving as main input from the role Caudate nucleus: Putman: Nucleus accumbens:
• Globus pallidus: In motor control together putman with the form : The internal parts and inhibits from the straitum outputs to the thalmus
• Substanla nigra: Retciulata SNr: Compacrta: for the controlling the moving the produce dompaine and fluencing the learning
• Subthalami nuclei: palys a role in lumbic function in basal hanglu and is it glutaminergic structure

Pathologies and dysfunctions

Parkinson's Disease

• Neurodegerative disease it and losing the in the substantia levels
• Reduced in dopamine level to the function through the meditation

Huntington's Disease

• Is neuroregenterative and breakdown of nerve, and effect cognition of help with manage medications

Hemiballismus:

• Fliging the with the the movement of the treatment with the DBA Balance and coordination problems: Focusing or thinking difficulty:

Cnections of related

• Cerebro cortex: ganalia receive inputs from the straitum System that influencing behavior integrating and related with emotions

Motors Control

• Have main circuits with the main pathways : direct and the pathways

Direct pathway

Factors that impact the basal Ganalia

• Neurstransomitters: Projections are excitatory inhibtory
• Domapine: Promotes the movement by the enmaching
• Summary of internal process: Critea of the the to decrease

Four Basic Cortico-Basal Ganglia-Thalamo-Cortical

• It conatins the circuit and the cerebral cortex

The loops are

: Motor Loop: to the learning movement Planning and inhibating bad behavior Limbic Loop: and related and playing role for the emotion and reward Oculomotor Loop: for in the eye movements