The document summarizes the inputs, circuits, and outputs of the cerebellum in 3 parts: 1) The main inputs to the cerebellum come from the cerebral cortex, spinal cord, and vestibular system via several tracts. 2) Within the cerebellum, there are circuits between the mossy fibers, climbing fibers, Purkinje cells, deep nuclei, and other areas that process information. 3) The outputs from the cerebellum influence motor control and are sent to various areas like the spinal cord, brainstem, thalamus, and motor cortex via different tracts.

1. Interactive cerebellar circuits Dr Sanjoy Sanyal MBBS, MS, MSc, ADPHA, ADHRD

2. Overview of cerebellar circuits Inputs to cerebellum Intracerebellar circuits Outputs from cerebellum 9-click summary of cerebellar circuits Guide to abbreviations In order to make the study of cerebellum easy it has been divided into three sections, followed by a summary slide at the end. In order to make it interesting, it has been rendered as interactive as possible. Click on any link above to go to the appropriate slide. Click on the appropriate links in individual slides (if any) to go to further slides. Click on back button at bottom right of any slide to come back to menu / sub-menu slide. The 2 nd last slide summarizes the entire cerebellar circuitry in 9 clicks. Guide to abbreviations is in last slide

3. Inputs to cerebellum Corticopontocerebellar Cerebro-olivocerebellar Cerebroreticulocerebellar Dorsal spinocerebellar Ventral spinocerebellar Cuneocerebellar Primary vestibular fibers Vestibulocerebellar Spinal cord Vestibular system Cerebral cortex CBLM

4. Inputs to cerebellum CORTICO-PONTO-CEREBELLAR TRACT CBLM Pons Cerebral cortex

5. Inputs to cerebellum CEREBRO-OLIVO-CEREBELLAR TRACT Only Climbing fibers ; all others are Mossy fibers CBLM Inferior olivary nucleus Cerebral cortex

6. Inputs to cerebellum CEREBRO-RETICULO-CEREBELLAR TRACT CBLM Reticular (Pons) Cerebral cortex

7. Inputs to cerebellum CEREBRO-RETICULO-CEREBELLAR TRACT CBLM Reticular (Medulla) Cerebral cortex

8. Inputs to cerebellum DORSAL SPINO-CEREBELLAR TRACT Uncrossed tract CBLM ICP Spinal cord

9. Inputs to cerebellum VENTRAL SPINO-CEREBELLAR TRACT Crossed tract CBLM SCP Spinal cord

10. Inputs to cerebellum CUNEO-CEREBELLAR TRACT Uncrossed tract CBLM Cuneate nucleus (Medulla) Spinal cord

11. Inputs to cerebellum CBLM (FN lobe) ICP Primary Vestibular fibers

12. Inputs to cerebellum VESTIBULO-CEREBELLAR TRACT CBLM ICP Vestibular nucleus

13. Intracerebellar circuits Specific direct excitation General indirect excitation All inputs Mossy fibers Climbing fibers Purkinje cell Granular cell Purkinje cell Deep nuclei Deep nuclei

14. Intracerebellar circuits Left click once outside to see all circuits, or click on any link above to see that circuit Lateral vestibular nucleus Flocculonodular lobe Dentate nucleus Lateral hemisphere Interposed nuclei Intermediate hemisphere Fastigial nucleus Vermis Deep nuclei in medulla and outside Purkinje cells from

15. Intracerebellar circuits From Vermis From intermediate hemisphere From lateral hemisphere From FN lobe Left click once to see an individual circuit Lat vestib nucleus Dentate nucleus Interposed nucleus Fastigial nucleus Purkinje cells

16. Intracerebellar circuits From Vermis Left click once to see next circuit Fastigial nucleus Purkinje cells

17. Intracerebellar circuits From intermediate hemisphere Left click once to see next circuit Interposed nucleus Purkinje cells

18. Intracerebellar circuits From lateral hemisphere Left click once to see next circuit Dentate nucleus Purkinje cells

19. Intracerebellar circuits From FN lobe Lateral vestibular nucleus Purkinje cells

20. Outputs from cerebellum Left click once outside to see all outputs, or click on any link above to see that output VL nucleus in thalamus Dentate nucleus Red nucleus in midbrain Interposed nuclei (Globose, Emboliform) Reticular formation in brainstem Fastigial nucleus Lateral vestibular nucleus in brainstem Fastigial nucleus Nuclei outside cerebellum Deep nuclei in cerebellar medulla

21. Outputs from cerebellum Vestibulospinal tract (uncrossed) Reticulospinal tract (uncrossed) Rubrospinal tract (double-crossed) Thalamocortical tract (double-crossed) Fastigial-vestibular Fastigial-reticular Interposed-rubral Dentato-thalamic Left click once to see an individual output Motor cortex Spinal cord Spinal cord Spinal cord Fastigial Interposed Dentate Vestib n Retic n Red n Thalamus

22. Outputs from cerebellum ICP Vestibulospinal tract (uncrossed) Left click once to see next output Spinal cord Fastigial nucleus Vestibular nuclei

23. Outputs from cerebellum ICP Reticulospinal tract (uncrossed) Left click once to see next output Spinal cord Fastigial nucleus Reticular formation

24. Outputs from cerebellum SCP decussation Rubrospinal tract (double-crossed) Left click once to see next output Spinal cord Interposed nuclei Red nucleus

25. Outputs from cerebellum SCP decussation Thalamocortical tract (double-crossed) Cerebral cortex (motor) Dentate nucleus Thalamus VL nucleus

26. Spinal cord Cerebral cortex Primary vestibular fibers Vermis Intermediate hemisphere Lateral hemisphere FN lobe Fastigial nucleus Interposed (Globose, Emboliform) Dentate nucleus Lat vestibular nucleus Vestibular nucleus Brainstem reticular formation Red nucleus VL nu thalamus Pontine nuclei Inf oliv n (medulla) Br st ret formation F-V (ICP) F-R (ICP) Vest spinal tract (Uncrossed) Ret spinal (Uncrossed) G-E Rubral (SCP decussation) Rubro spinal (Crossed) Dorsal SCB (ICP) Ventral SCB (SCP) Cuneo CB (ICP) CPC (MCP) COC (ICP) CRC (ICP, MCP ) Dentato-thalamic (SCP decussation) Thalamo-cortical (Internal capsule, Corona radiata) ICP ICP ICP Corticospinal (decussation) 8 th cranial nerve Click once and wait for one complete circuit animation before clicking for the next circuit. Click 9 times in total.

27. Abbreviations guide Br st ret : Brainstem Reticular CB : Cerebellar COC : Cerebro-Olivo-Cerebellar CPC : Cortico-Ponto-Cerebellar CRC : Cerebro-Reticulo-Cerebellar FN : Flocculo-Nodular FR : Fastigial-Reticular FV : Fastigial-Vestibular GE : Globose-Emboliform ICP : Inferior Cerebellar Peduncle Inf oliv n : Inferior Olivary Nucleus Lat : Lateral MCP : Middle Cerebellar Peduncle Nu : Nucleus SCB : Spinocerebellar SCP : Superior Cerebellar Peduncle VL : Ventral Lateral