The association between eye movements and cerebellar activation during verbal working memory
Final Report Abstract
The present study investigated whether cerebellar activations in an fMRI-based Sternberg verbal working memory task can be related to oculomotor processing. Oculomotor and cognitive task demands were manipulated by using closely-spaced and widely-spaced stimuli, and high (4 letters) and low (2 letters) cognitive load, respectively. If cerebellar activations merely masqueraded as cognition, activation patterns in the encoding phase of the Sternberg task should reflect phasedependent differences in oculomotor demand. In contrast, if activations reflected direct cerebellar involvement in cognition, activation patterns were expected to be independent of the manipulation of oculomotor demand. The present fMRI results confirm the load effect previously reported for cerebellar activations on the Sternberg task: Encoding of high versus low stimulus load was associated with greater cerebellar activations in right inferior (lobule VIII) and bilateral superior (lobule VI, Crus I) regions. These activations have previously been interpreted in terms of an internal motor (articulatory) representation and contribution to phonological storage. Analysis of eye data confirmed that - trivially - widely-spaced stimuli were associated with more eye movement than closely-spaced stimuli. Encoding of stimuli with wide versus close spacing was associated with greater cerebellar activations in the right posteroinferior cerebellum (lobule VIII) and bilateral vermal regions (vermis VI). This is consistent with previous fMRI studies implicating vermis VI and VII, also referred to as the “oculomotor” vermis, in saccadic eye movements. Involvement of lobule VIII has been shown for other forms of eye movement such as smooth pursuit, while reading-related activity can typically found in lobules VI and VII. There were no cerebellar activations reflecting the interaction between load and spacing. Crucially, loaddependent activations in lateral superior regions (lobule VI/Crus I) and posteroinferior regions (lobule VIIB/VIIIA) of the cerebellum remained largely unchanged when quantity of horizontal eye movement was taken into account. Since this procedure cannot determine if eye movements differentially affected trials with high or low cognitive load, a further analysis was performed, reclassifying trials according to oculomotor behavior and load by using the individual medians of horizontal eye movement. Again, the load effect was confirmed, and no cerebellar activations reflecting the load x oculomotor behavior interaction were found. Taken together, the present data therefore suggest that the cerebellar load effect is independent of oculomotor behavior. This finding refutes the notion that cognitive-load-dependent cerebellar activations solely reflect eye movementrelated processing.
Publications
- Processing of eye movement-related information in the human cerebellum. Johns Hopkins School of Medicine in Baltimore, MD, USA, Clinical Neuroscience Seminar Series, Nov 24, 2014
Peterburs, J.
- The association between eye movements and cerebellar activation in a Sternberg verbal working memory task. Society of Neuroscience’s (SfN) 2014 annual meeting in Washington, DC, Nov. 15-19, 2014
Peterburs, J., Cheng, D.T., Desmond, J.E.
- The association between eye movements and cerebellar activation in a verbal working memory task. Cerebral Cortex, Volume 26, Issue 9, 1 September 2016, Pages 3802–3813
Peterburs, J., Cheng, D.T., Desmond, J.E.
(See online at https://doi.org/10.1093/cercor/bhv187)
