Effector‐independent representations of simple and complex imagined finger movements: a combined fMRI and TMS study

Abstract

Kinesthetic motor imagery and actual execution of movements share a common neural circuitry. Functional magnetic resonance imaging was used in 12 right-handed volunteers to study brain activity during motor imagery and execution of simple and complex unimanual finger movements of the dominant and the nondominant hand. In the simple task, a flexible object was rhythmically compressed between thumb, index and middle finger. The complex task was a sequential finger-to-thumb opposition movement. Premotor, posterior parietal and cerebellar regions were significantly more active during motor imagery of complex movements than during mental rehearsal of the simple task. In 10 of the subjects, we also used transcranial magnetic brain stimulation to examine corticospinal excitability during the same motor imagery tasks. Motor-evoked potentials increased significantly over values obtained in a reference condition (visual imagery) during imagery of the complex, but not of the simple movement. Imagery of finger movements of either hand activated left dorsal and ventral premotor areas and the supplementary motor cortex regardless of task complexity. The effector-independent activation of left premotor areas was particularly evident in the simple motor imagery task and suggests a left hemispherical dominance for kinesthetic movement representations in right-handed subjects.

Volition and Imagery in Neurorehabilitation

“…For instance, fMRI studies investigating imagery of finger and hand movements [19][20][21][22] demonstrated activation of the supplementary motor area (SMA), the premotor cortex (PMC), and the cerebellum but also the primary motor cortex contralateral (cM1) to the imagined movements. fMRI and TMS studies 23 demonstrated that cM1 is activated during imagery tasks of increasingly complex movements, a result consistent with a previous finding of more prominent involvement of M1 with performance of complex motor sequences. 24 Further evidence for the existence of common brain regions engaged in performance and imagination of movements comes from work by Li et al 25 These authors illustrated similarities in characteristics of finger interactions during both motor imagery and motor execution.…”

Complexity and familiarity enhance single-trial detectability of imagined movements with electroencephalography

“…The finding that the complex imagery resulted in an enhancement of the SMR compared to the simple imagery within Study 3 aligns well with previous work (e.g., Kuhtz-Buschbeck et al, 2003;Roosink & Zijdewind, 2010;Holper & Wolf, 2011). Moreover, there was more potential variability in the brain responses between participants in the piano imagery for Study 2 versus Study 3 due to variations in the particular pieces that each person chose to imagine in Study 2; this variability likely resulted in less consistent and less robust brain responses between individuals, regardless of their familiarity with the piano.…”

“…In Study 1 (Complexity), participants imagined simple hand actions (squeezes) of the sort typically used with SMR-based BCIs alongside other more complex bimanual actions not commonly used with BCIs. It was predicted that, in accordance with prior evidence of increased brain activity during complex motor imagery (Kuhtz-Buschbeck et al, 2003;Roosink & Zijdewind, 2010;Holper & Wolf, 2011), classification accuracy (versus rest) would be higher when the participant was imagining complex actions than when imagining relatively simpler actions. In Study 2 (Familiarity), groups of experienced pianists, experienced ice hockey players, and age-matched controls were instructed to imagine completing hand squeezes and actions from hockey and piano.…”

“…Indeed, there is evidence that complex imagined actions are associated with more robust brain responses than simpler imagined actions. For instance, there is converging evidence from functional magnetic resonance imaging (fMRI), functional nearinfrared spectroscopy (fNIRS), and transcranial magnetic stimulation (TMS) studies that complex motor imagery is associated with greater hemodynamic change and higher amplitude motor-evoked potentials than simple motor imagery (e.g., Kuhtz-Buschbeck et al, 2003;Roosink & Zijdewind, 2010;Holper & Wolf, 2011). In the latter studies and in this paper, "complex" motor imagery is defined as tasks that involve sequences of movements (e.g., KuhtzBuschbeck et al, 2003;Roosink & Zijdewind, 2010;Holper & Wolf, 2011), and/or more than one body part (e.g., Holper & Wolf, 2011).…”

Cortical activation during executed, imagined, observed, and passive wrist movements in healthy volunteers and stroke patients

“…A reason for this may be that motor imagery is more difficult for patients so that additional neural resources are recruited for task performance. However, most previous studies in healthy subjects showed that neither movement complexity (as an operationalization for movement difficulty and task demands) nor motor imagery proficiency affect the neuroanatomical correlates of MI (Boecker et al, 2002;Gerardin et al, 2000;Guillot et al, 2008;Lehericy et al, 2004) (but see Kuhtz-Buschbeck et al, 2003). Thus, an alternative explanation would be that the extended activations in patients as compared to HVs mimic the pattern observed for overt attempted execution.…”