Does the Cerebellum Contribute to Human Navigation by Processing Sequential Information?
Objective: Several authors have proposed that the cerebellum has an important role in functions of higher order as a general mode of sequence detection, independently from the nature of the information. The aim of this study was to verify whether the cerebellum mediates the processing of navigational sequential information and to determine whether it is influenced by the modality of the stimuli presentation. Method: We tested 12 cerebellar patients and 12 healthy age-matched participants in 2 comparable navigational tasks (Walking Corsi Test and the Magic Carpet) requiring to memorizing a sequence of spatial locations. The 2 tasks differ each other for the modality of stimuli presentation: in the Walking Corsi Test the sequence is shown by an examiner that walks on the carpet, whereas in the Magic Carpet it is shown by a computer that lights up the tiles in the sequence. We hypothesize that different mental processes are implicated between the Walking Corsi Test and the Magic Carpet. Indeed, whereas watching the examiner, who performs the sequence on the carpet, allows the patient to simulate the action mentally in the Walking Corsi Test, such simulation cannot be triggered in the Magic Carpet. Results: Our results showed that cerebellar patients obtained scores significantly lower than control participants only in the Magic Carpet. Conclusions: We interpreted the patients’ performance as a specific deficit in detecting and ordering single independent stimuli as a sequence, when the maintenance of stimulus–response associations is more demanding.