Cerebellum Neuroanatomy and Function

Flashcards covering the anatomical structure, development, functional organization, and cognitive roles of the cerebellum based on the Week 6 Lecture 11 transcript.

Cerebellum

Latin for “the little brain,” this structure makes up $11\%$ of total brain mass and contains between $50\%$ and $80\%$ of the brain’s neurons.

• Damage to the cerebellum leads to impairments in motor control and posture on the ipsilateral side of the body

Maintenance of balance and posture

A core function of the cerebellum where it monitors input from vestibular receptors and proprioceptors to make unconscious adjustments to motor neurons.

Correction of voluntary movements

A cerebellar function where it coordinates the timing and force of different muscle groups to produce fluid limb or body movements by comparing intended and actual movements.

• requires sensory input (visual, proprioception, etc) and processing from the cerebral cortex

Motor learning

The process of adapting and fine-tuning motor programs through trial-and-error, involving a shift from conscious to unconscious control (“muscle memory”).

Folia

The finely spaced parallel grooves on the cerebellar surface that form a continuous thin layer of tissue folded like an accordion.

Rhombic lips

The edges of the $4^{th}$ ventricle from which the cerebellum begins to develop starting on the $5^{th}$ week of development.

Cerebellar plate

A structure formed by the fusion of the rhombic lips in the midline, which by the $12^{th}$ week of development forms the vermis and two lateral hemispheres.

Vermis

The unpaired, midline portion of the cerebellum that connects the two hemispheres; it is composed of lobules assigned Roman Numerals I-IX

Cerebellar cortex

The external gray matter of the cerebellum consisting of neuron cell bodies.

Cerebellar medulla

The internal white matter of the cerebellum composed of incoming and outgoing myelinated axon fibers.

Deep nuclei

Centrally located nuclei within the cerebellar white matter that serve as the primary output from the cerebellum.

1. Granule cell layer

The innermost layer of the cerebellar cortex made of tightly packed granule neurons.

2. Purkinje neuron layer

The middle layer of the cerebellar cortex, only $1$-cell thick, containing large neurons with elaborate branching dendrites.

3. Molecular layer

The outer layer of the cerebellar cortex consisting of granule motor axons and Purkinje neuron dendrites, but containing no somas.

Arbor vitae

Latin for “tree of life,” referring to the tree-like appearance of white matter tracts within the cerebellum seen in sagittal sections.

Superior cerebellar peduncle (SCP)

Connects the cerebellum to the midbrain (mesencephalon) and primarily carries efferent tracts leaving the cerebellum.

Middle cerebellar peduncle (MCP)

The largest peduncle; it connects the pons to the contralateral cerebellar hemisphere and carries motor tracts from the cerebral cortex via the pontine nuclei.

Inferior cerebellar peduncle (ICP)

Connects the cerebellum to the medulla and carries afferent tracts from the spinal cord/brainstem and efferent tracts to the vestibular nuclei and inferior olives.

Vesticulocerebellum

Functional region consisting of the flocculonodular lobe and parts of the posterior lobe/vermis that regulates balance and eye movements.

Spinocerebellum

Functional region consisting of the vermis and intermediate hemispheres that regulates muscle tone and coordinates skilled voluntary movement using proprioceptive input.

Cerebrocerebellum

Functional region consisting of the lateral parts of the hemispheres involved in movement planning and non-motor cognitive functions.

Dentate nucleus

The largest deep nucleus; it receives information related to fine dexterity and is important for the timing, planning, and inception of voluntary motor activity. Its neurons projects to the red nucleus and the ventrolateral (VL) thalamic nucleus

Interposed nuclei

A collective term for the emboliform and globose nuclei which receive spinal, somatosensory, auditory, and visual information. Their neurons project to the red nucleus in the brainstem

Fastigial nuclei

Deep nuclei associated with the vermis that project to the vestibular nuclei in the brainstem for the maintenance of balance. Its neurons project out to vestibular nuclei in the brainstem and sends its efferent fibers to the proximal and trunk muscles for maintenance of balance.

‘Don’t eat greasy food’

A mnemonic for the lateral-to-medial location of deep cerebellar nuclei: Dentate, Emboliform, Globose, and Fastigial.

Ipsilateral control

The principle that cerebellar inputs and outputs concern the same side of the body, meaning injury to one side affects the musculature of the same side.

Prediction center

A description of the cerebellum reflecting its role in calculating and monitoring predicted versus actual sensory, social, language, and threat outcomes.

Motor: predicting motor commands and outcomes (movements) and using actual sensory data about body position for future error correction/predictions

• Non-motor: calculating and monitoring predicted sensory/social/language/threat outcomes with actual sensory data and updating predictions based on this (non-motor error correction)

Internal models

Predictive estimates of the sensory state of the body and environment encoded in the cerebellum, allowing for faster motor adjustments than cortical processing allows.

Color constancy

A phenomenon in internal models where the brain uses prior knowledge (e.g., that strawberries are red) to perceive colors even when the actual sensory input (pixels) differs.

purkinje cells

one of the largest neurons in the human brain with an elaborate branching dendrites that are only found in the cerebellum

cerebellar lobes

• anterior lobe

• posterior lobe

• flocculonodular lobe

cerebellar output

Output remains ipsilateral therefore injury to the cerebellum itself will affect function on the SAME SIDE of the body

cerebellar monitoring of motor commands

The cerebellum monitors motor commands produced by the cortex and the actual body position and motor responses by integrating sensory tract input.

comparison of movement

The cerebellum compares motor commands (intended movements) to sensory feedback (actual movements) to determine if the produced movement is correct.

motor: intended movement

sensory: actual movement