Increased activation of the human cerebellum during pitch discrimination: a positron emission tomography (PET) study.

Recent years have seen a growing debate concerning the function of the cerebellum. Here we used a pitch discrimination task and PET to test for cerebellar involvement in the active control of sensory data acquisition. Specifically, we predicted greater cerebellar activity during active pitch discrimination compared to passive listening, with the greatest activity when pitch discrimination was most difficult. Ten healthy subjects were trained to discriminate deviant tones presented with a slightly higher pitch than a standard tone, using a Go/No Go paradigm. To ensure that discrimination performance was matched across subjects, individual psychometric curves were assessed beforehand using a two-step psychoacoustic procedure. Subjects were scanned while resting in the absence of any sounds, while passively listening to standard tones, and while detecting deviant tones slightly higher in pitch among these standard tones at four different performance levels. Consistent with our predictions, 1) passive listening alone elicited cerebellar activity (lobule IX), 2) cerebellar activity increased during pitch discrimination as compared to passive listening (crus I and II, lobules VI, VIIB, and VIIIB), and 3) this increase was correlated with the difficulty of the discrimination task (lobules V, VI, and IX). These results complement recent findings showing pitch discrimination deficits in cerebellar patients (Parsons et al., 2009) and further support a role for the cerebellum in sensory data acquisition. The data are discussed in the light of anatomical and physiological evidence functionally connecting auditory system and cerebellum.

Pitch discrimination in cerebellar patients: evidence for a sensory deficit.

In the last two decades, a growing body of research showing cerebellar involvement in an increasing number of nonmotor tasks and systems has prompted an expansion of speculations concerning the function of the cerebellum. Here, we tested the predictions of a hypothesis positing cerebellar involvement in sensory data acquisition. Specifically, we examined the effect of global cerebellar degeneration on primary auditory sensory function by means of a pitch discrimination task. The just noticeable difference in pitch between two tones was measured in 15 healthy controls and in 15 high functioning patients afflicted with varying degrees of global cerebellar degeneration caused by hereditary, idiopathic, paraneoplastic, or postinfectious pancerebellitis. Participants also performed an auditory detection task assessing sustained attention, a test of verbal auditory working memory, and an audiometric test. Patient pitch discrimination thresholds were on average five and a half times those of controls and were proportional to the degree of cerebellar ataxia assessed independently. Patients and controls showed normal hearing thresholds and similar performance in control tasks in sustained attention and verbal auditory working memory. These results suggest there is an effect of cerebellar degeneration on primary auditory function. The findings are consistent with other recent demonstrations of cerebellar-related sensory impairments, and with robust cerebellar auditorily evoked activity, confirmed by quantitative meta-analysis, across a range of functional neuroimaging studies dissociated from attention, motor, affective, and cognitive variables. The data are interpreted in the context of a sensory hypothesis of cerebellar function.

Cerebellum and auditory function: an ALE meta-analysis of functional neuroimaging studies.

Over the past two decades neuroimaging data have accumulated showing that the cerebellum, traditionally viewed only as a motor structure, is also active in a wide variety of sensory and cognitive tasks. We have proposed that instead of explicit involvement in any particular motor, sensory, or cognitive task, the cerebellum performs a much more fundamental computation involving the active acquisition of sensory data. We carried out an activation likelihood estimate (ALE) meta-analysis to determine whether neuroimaging results obtained during a wide range of auditory tasks support this proposal. Specifically, we analyzed the coordinates of 231 activation foci obtained in 15 different auditory studies selected through an extensive search of the positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) literature. The studies selected represent a wide variety of purely auditory tasks using highly controlled synthesized acoustic stimuli. The results clearly revealed that in addition to temporal auditory areas of cerebral cortex, specific regions in the cerebellum are activated consistently across studies regardless of the particular auditory task involved. In particular, one area in left lateral crus I area showed the greatest volume and ALE peak value among the extratemporal regions. A subanalysis was carried out that ruled out the specific association of this cerebellar cluster with attentional demand. The results are consistent with the hypothesis that the cerebellum may play a role in purely sensory auditory processing, and are discussed in light of the broader idea of the cerebellum subserving a fundamental sensory function.