The Flocculonodular Lobe
The flocculonodular lobe is the oldest part of the cerebellum – in lower vertebrates, it is actually the cerebellum. It regulates balance and coordinates eye movements, and its name literally translates as “flake nodule lobe.”
Scientific support: Prof. Dr. Jochen F. Staiger
Published: 05.08.2025
Difficulty: intermediate
he flocculonodular lobe, with its paw-like protrusions, makes up only a small part of the cerebellum, but it is a very important one: it regulates balance.
The flocculonodular lobe is named after its two components, the paired flocculus (flake) and the unpaired nodulus (nodule). It is the oldest segment of the cerebellum in terms of evolutionary development, which is why it is sometimes referred to as the archicerebellum.
The nodulus is a slightly thickened part of the cerebellar vermis, located at its lowest point. Via the pedunculus flocculi, a lamina of white, medullary brain substance, it connects on both sides to the flocculus, which belongs to the hemispheres. However, it is quite difficult to find the flocculus in anatomical illustrations, as it is only a few centimeters wide and hidden under the cerebellar peduncles on the side facing the brain stem. It is separated from the hemispheres by a deep groove, the fissura posterolateralis. Its shape is reminiscent of two cat paws: it is broad and flat and almost toe-shaped at the ends.
Coordination center for the sense of balance
The flocculonodular lobe is where it all began for the cerebellum: as its oldest part, it is found in all vertebrates – in lower representatives such as lampreys or hagfish (an early research subject of Sigmund Freud), it even constitutes the entire cerebellum. It always involves vestibular impulses, but in different forms. In frogs, for example, the flocculonodular lobe still appears as fairly large ear-shaped bulges, while in other reptiles and birds it is only an inconspicuous lateral appendage.
However, this does not mean that this ancient part of the cerebellum no longer plays an important role in modern humans – on the contrary: It forms the vestibulocerebellum, which ensures balance and stabilizes sitting, standing, and walking by influencing the trunk and limb extensor muscles. It also coordinates eye movements, i.e., the muscles of the eyeball.
In order to perform this task, it receives processed balance information from the vestibular nuclei and even directly from the balance organ in the inner ear. This is remarkable because no other sensory channel sends such primary sensory information to the cerebellum. Via the inputs from the vestibular nuclei, the flocculonodular lobe keeps track of whether the head is tilted downwards or turning to the right at that moment, for example. It sends its signals to the fastigial nucleus in the medulla oblongata below the upper cerebellar vermis, which in turn activates the vestibular nuclei. At the same time, some fibers from its cortex – always inhibitory – also run directly to the vestibular nuclei without first being switched in a cerebellar nucleus –another example of the close connection between the sense of balance and the cerebellum.
If the flocculonodular lobe fails, an important reflex arc of balance is disrupted; the patient experiences dizziness and vomiting. In addition, they can no longer sit or stand upright, but sway constantly. Eye movements are also disrupted, with the eyeball twitching rhythmically and uncontrollably back and forth. The neurologist refers to this phenomenon as pathological nystagmus.
First published on August 23, 2011
Last updated on August 5, 2025
