BG and Brain Stem

What is the technically-correct name for the 'basal ganglia' and why is 'basal ganglia' a misnomer?

Basal nuclei; 'ganglia' refers to PNS clusters while 'nuclei' refers to CNS clusters.

List the three structures that compose the striatum.

Caudate nucleus, putamen, nucleus accumbens.

Which two structures form the lentiform nucleus?

Putamen and globus pallidus.

Name the two major parts of the globus pallidus and one motor role for each.

Globus pallidus external (GPe) — inhibits subthalamic nucleus to fine tune movement initiation/termination. Globus pallidus internal (GPi) — inhibits motor thalamus and suppresses unwanted actions.

Which basal nuclei structure contains most of the brain's dopamine neurons and what is its primary modulatory role?

Substantia nigra pars compacta (SNpc); modulates likelihood of movement and provides dopaminergic input for reward prediction/error.

Multiple Choice: The nucleus accumbens is primarily involved in: A) Visual reflexes B) Reward and motivation C) Balance D) Language production

B

Explain in one sentence the Selection/Inhibition theory of basal ganglia function.

The basal ganglia select appropriate motor programs and inhibit competing ones to enable execution of the chosen action.

What role does the subthalamic nucleus (STN) play and why is it targeted in Parkinson's disease treatment?

STN excites output pathways to suppress unwanted movement; in Parkinson's it becomes overactive due to loss of GPe inhibition, and DBS of STN reduces excessive activity improving motor symptoms.

True/False: The thalamus is part of the basal ganglia.

FALSE

Match: Putamen — (A) executes habitual learned motor programs (B) initiates goal-directed reward sequences (C) disinhibits thalamus

A

Describe the functional difference between SNpr and SNpc.

SNpc contains dopaminergic neurons providing modulatory input (input); SNpr contains GABAergic output neurons that send inhibitory outputs (output) to thalamus and brainstem.

Which basal nuclei structure is most associated with motivation, reinforcement learning and addiction?

Nucleus accumbens.

Multiple Choice: The internal capsule separates which structures? A) Caudate from lentiform nucleus B) Substantia nigra from red nucleus C) Superior and inferior colliculi D) Pons from medulla

A

Short Answer: Name three non-motor functions attributed to the basal nuclei.

Executive functions (decision making, working memory), reward/valuation and motivation, impulse control/affect regulation.

Explain the concept of overlapping loops in basal ganglia function.

Basal nuclei participate in multiple overlapping cortico-basal ganglia-thalamo-cortical loops (motor, oculomotor, prefrontal, limbic), and the same neurons can contribute to different functions depending on cortical input context.

Which structure is ventral to the globus pallidus, associated with reward and motivation, but not strictly part of the basal nuclei?

Ventral pallidum.

MCQ: Deep brain stimulation (DBS) of the GPi primarily aims to: A) increase GPi output B) reduce abnormal GPi inhibitory output to thalamus C) activate dopamine production D) lesion the STN

B

Short Answer: What is the pallidum complex?

The pallidum complex comprises the internal and external globus pallidus plus the ventral pallidum.

True/False: The ventral tegmental area (VTA) is considered part of the basal nuclei.

False (it is not part of basal nuclei but functionally connected).

Short Answer: Give one clinical consequence of SNpc dopamine neuron loss.

Parkinson's disease symptoms: bradykinesia, rigidity, resting tremor, postural instability.

MCQ: Which basal ganglia nucleus sends major inhibitory output to the motor thalamus? A) GPe B) GPi C) Putamen D) Nucleus accumbens

B

Short Answer: Describe one experimental evidence linking nucleus accumbens activity to social reward.

Fiber photometry recordings show nucleus accumbens activity increases during rewarding social interactions and mice choose social interaction over objects, indicating reward valuation. (e.g., Gunaydin et al., Cell 2014).

Short Answer: Name the three major parts of the brainstem.

Midbrain, pons, medulla oblongata.

MCQ: Which cerebellar peduncle connects pons to cerebellum? A) Superior B) Middle C) Inferior D) Lateral

B

Short Answer: What is the main function of the middle cerebellar peduncle?

Carries fibers from pontine nuclei to the contralateral cerebellum (input from cortex), enabling motor planning and error correction.

True/False: The tectum (superior/inferior colliculi) is present throughout the entire brainstem.

False (tectum is present only in the midbrain).

Short Answer: What senses are associated with the superior and inferior colliculi respectively?

Superior colliculus — vision; Inferior colliculus — audition.

Short Answer: Where is the periaqueductal gray (PAG) located and name two of its functions.

Around the cerebral aqueduct in the midbrain; functions include pain modulation and defensive/aversion behaviors and autonomic regulation.

MCQ: The pyramids on the ventral medulla contain: A) ascending sensory tracts B) descending corticospinal and corticobulbar tracts C) cerebellar afferents D) vestibular fibers

B

Short Answer: What and where is the pyramidal decussation?

The crossing of corticospinal fibers at the caudal medulla where the pyramids decussate; below this the spinal cord begins.

Short Answer: Name the dorsal column nuclei in the caudal medulla.

Nucleus gracilis and nucleus cuneatus.

MCQ: The inferior olivary nuclei are most involved in: A) auditory processing B) cerebellar motor-learning C) visual reflexes D) taste

B

Short Answer: Which cranial nerve conveys vestibular information to the vestibular nuclei?

Cranial nerve VIII (vestibulocochlear nerve).

Short Answer: What causes motion sickness in terms of sensory mismatch?

Conflict between vestibular inputs (sensing motion) and visual inputs (sensing stationary environment), leading to a mismatch processed by cerebellum/brainstem.

MCQ: Dramamine (an anti-motion sickness drug) primarily acts as: A) a dopamine agonist B) an antihistamine C) an opioid D) a serotonin reuptake inhibitor

B

Short Answer: What are the three functional roles of the brainstem listed in the lecture?

Relay/conduit, integration and regulation of sensory information (reticular formation), and origin/termination of cranial nerves.

MCQ: The reticular activating system (RAS) projects to: A) spinal cord only B) thalamus and cortex C) cerebellum only D) basal ganglia only

B

Short Answer: Name two functions modulated by the reticular formation.

Arousal/wakefulness (consciousness), pain modulation, autonomic regulation (respiration, cardiac), motor tone and spinal reflex modulation.

True/False: The RAS filters out repetitive and weak sensory input and can transmit salient stimuli to awaken sleeping cortex.

TRUE

Short Answer: Where are the dorsal columns (gracile & cuneate fasciculi) located in relation to the medulla and what happens to them there?

They are present in the caudal medulla and synapse in the gracile and cuneate nuclei; second-order neurons decussate and form the medial lemniscus.

MCQ: The medial lemniscus carries: A) proprioception and fine touch B) pain and temperature C) visual information D) motor commands

A

Short Answer: Which tract carries anterior spinocerebellar fibers into the cerebellum and through which peduncle do they enter?

Anterior spinocerebellar tract; enters via the superior cerebellar peduncle (SCP).

Short Answer: Which spinocerebellar tract enters the cerebellum via the inferior cerebellar peduncle?

Posterior spinocerebellar tract (and cuneocerebellar tract).

MCQ: In cross sections, presence of the red nucleus indicates which level? A) Rostral midbrain B) Caudal medulla C) Mid pons D) Caudal midbrain

A

Short Answer: What is the general location and function of the tegmentum?

Tegmentum is the central core/floor of the midbrain (and present throughout the brainstem) containing nuclei like red nucleus and substantia nigra; it participates in motor pathways and autonomic/control functions.

MCQ: Which structure forms the ventral surface 'bulge' with transverse fibers of the pons? A) Cerebral peduncle B) Pontine nuclei C) Medial lemniscus D) Superior colliculus

B

Short Answer: Name three disorders associated with disruption of the RAS.

Coma/vegetative state, narcolepsy, depression, schizophrenia, PTSD, AD/PD, ADHD, autism (sensory over-responsivity). (Any three)

MCQ: Which nucleus in the medulla is the second-order synapse for dorsal column fibers from the lower limb? A) Lateral cuneate nucleus B) Nucleus gracilis C) Inferior olivary nucleus D) Vestibular nucleus

B

Short Answer: What landmark distinguishes rostral midbrain from caudal midbrain in cross sections?

Presence of the superior colliculus/red nucleus (rostral) vs inferior colliculus/decussation of SCP (caudal).

Short Answer: Explain why the middle cerebellar peduncle fibers appear as transverse pontine fibers.

Axons from pontine nuclei project contralaterally into the middle cerebellar peduncle; their transverse crossing as they course to the cerebellum create the pontine transverse fibers on the ventral pons.

MCQ: The lateral vestibular nuclei primarily send outputs to: A) occipital cortex B) spinal cord for postural adjustments C) auditory cortex D) thalamus only

B

Short Answer: What is the function of the red nucleus and where is it located?

Red nucleus in rostral midbrain tegmentum is involved in motor coordination and origin of rubrospinal tract for fine control of limb/hand movements.

True/False: Spinothalamic tracts run laterally through the brainstem carrying pain and temperature.

TRUE

Short Answer: Provide three identifying features of a rostral medulla cross-section.

Inferior olivary nuclei (IO), pyramids (Py), and open 4th ventricle/floor near rostral medulla; presence of vestibular nuclei.

MCQ: Which tract decussates in the medulla to form the medial lemniscus? A) Spinothalamic B) Corticospinal C) Dorsal column (gracile/cuneate) D) Rubrospinal

C

Short Answer: What is locked-in syndrome and which structures are typically intact vs damaged?

Locked-in syndrome: consciousness and cognitive function intact (RAS and cortex preserved) but corticospinal/corticobulbar tracts damaged (ventral pons), producing paralysis with preserved vertical eye movements and blinking.

MCQ: EEG is limited for detecting activity in which brain regions? A) Cortical surface B) Deep brain regions (e.g., brainstem) C) Superficial gyri D) Frontal cortex

B

Short Answer: Name four basal nuclei and four brainstem nuclei you should be able to identify in cross-sections (give any examples).

Basal nuclei: Caudate, Putamen, GPi, GPe, STN, SNpc/SNpr, NAcc. Brainstem nuclei: Red nucleus, inferior olive, vestibular nuclei, pontine nuclei, gracile/cuneate nuclei, PAG.

MCQ: Which loop of the basal ganglia is primarily involved in eye movements? A) Motor loop B) Oculomotor loop C) Limbic loop D) Prefrontal loop

B

Short Answer: Give one example illustrating that basal nuclei perform similar computations for motor and non-motor functions.

The caudate can influence movement when communicating with motor cortex but also participate in cognitive decision-making when communicating with prefrontal cortex, showing suppression and selection computations across domains.