Effect of interstimulus interval on cortical proprioceptive responses to passive finger movements
Date
2017Author
Smeds, Eero
Piitulainen, Harri
Bourguignon, Mathieu
Jousm€ak, Veikko
Har, Riitta
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Smeds, E., Piitulainen, H., Bourguignon, M., Jousmäki, V. and Hari, R. (2017), Effect of interstimulus interval on cortical proprioceptive responses to passive finger movements. Eur J Neurosci, 45: 290–298. doi:10.1111/ejn.13447
Abstract
Shortening of the interstimulus interval (ISI) generally leads to attenuation of cortical sensory responses. For proprioception, however,
this ISI effect is still poorly known. Our aim was to characterize the ISI dependence of movement-evoked proprioceptive cortical
responses and to find the optimum ISI for proprioceptive stimulation. We measured, from 15 healthy adults, magnetoencephalographic
responses to passive flexion and extension movements of the right index finger. The movements were generated by a movement actuator
at fixed ISIs of 0.5, 1, 2, 4, 8, and 16 s, in separate blocks. The responses peaked at ~ 70 ms (extension) and ~ 90 ms (flexion) in
the contralateral primary somatosensory cortex. The strength of the cortical source increased with the ISI, plateauing at the 8-s ISI.
Modeling the ISI dependence with an exponential saturation function revealed response lifetimes of 1.3 s (extension) and 2.2 s (flexion),
implying that the maximum signal-to-noise ratio (SNR) in a given measurement time is achieved with ISIs of 1.7 s and 2.8 s
respectively. We conclude that ISIs of 1.5–3 s should be used to maximize SNR in recordings of proprioceptive cortical responses to
passive finger movements. Our findings can benefit the assessment of proprioceptive afference in both clinical and research settings.