Scaling of neural responses to visual and auditory motion in the human cerebellum

Abstract

The human cerebellum contains approximately half of all the neurons within the cerebrum, yet most experimental work in human neuroscience over the last century has focused exclusively on the structure and functions of the forebrain. The cerebellum has an undisputed role in a range of motor functions (Thach et al., 1992), but its potential contributions to sensory and cognitive processes are widely debated (Stoodley and Schmahmann, 2009). Here we used functional magnetic resonance imaging to test the hypothesis that the human cerebellum is involved in the acquisition of auditory and visual sensory data. We monitored neural activity within the cerebellum while participants engaged in a task that required them to discriminate the direction of a visual or auditory motion signal in noise. We identified a distinct set of cerebellar regions that were differentially activated for visual stimuli (vermal lobule VI and right-hemispheric lobule X) and auditory stimuli (right-hemispheric lobules VIIIA and VIIIB and hemispheric lobule VI bilaterally). In addition, we identified a region in left crus I in which activity correlated significantly with increases in the perceptual demands of the task (i.e., with decreasing signal strength), for both auditory and visual stimuli. Our results support suggestions of a role for the cerebellum in the processing of auditory and visual motion and suggest that parts of cerebellar cortex are concerned with tracking movements of objects around the animal, rather than with controlling movements of the animal itself (Paulin, 1993).

Figure 1.

Human cerebellar anatomy shown in sagittal and coronal planes. The locations of anatomical regions (nomenclature according to Schmahmann et al., 2000) were derived using the probabilistic atlas of the cerebellum by Diedrichsen et al. (2009).

Figure 2.

Mean response times (±1 SE) for the visual and auditory conditions of the motion discrimination task.

Figure 3.

MR brain slices showing mean BOLD activity from the random-effects analysis comparing modality-specific effects. a–c, Visual motion > auditory motion. d–f, Auditory motion > visual motion.

Figure 4.

MR brain slices depicting linear relationships between BOLD signal and the strength of the auditory and visual motion signals. a, Brain areas showing a negative correlation between BOLD signal and motion signal strength. Red shading represents activity for the visual motion condition; green shading represents activity for the auditory motion condition; yellow shading indicates activation overlap between the visual and auditory conditions. b, Brain areas showing a positive correlation between BOLD signal and auditory motion signal strength.