The evaluation of visual, motor and somatosensory cortex integration by non-invasive electrophysiological methods

Corticospinal excitability may be affected by various sensory inputs under physiological conditions. Studies about the connection and interaction between the primary motor cortex and these cortical sensory areas indicate that the relationships are relatively indirect. These studies are usually performed in relation to the interaction of the motor cortex with a single sensory modality. However; the effect of multiple sensory effects on motor cortical excitability is unknown. The aim of this study is to investigate the cortical excitability of somatosensory and visual-Goggle_LED stimulations using multimodal conditioning of transcranial magnetic stimulation (TMS) for the first time in order to understand the effect of multisensory effect on cortical excitability. Fourteen healthy volunteers participated in the study. The test-TMS was applied to 50, 60, 70, 80, 90, 100, 110, 120ms interstimulus intervals (ISI) after Goggle-LED as a conditioning stimulus. The average of 10 conditioned-motor evoked potential (MEP) amplitudes obtained in each ISI and the ISI-MEPGoggle_condition_ort parameters were obtained. In order to evaluate the dual sensory modality, Goggle-LED as a conditioning stimulus was applied, then electrical and then TMS was applied as a conditioning stimulus in 23 msec. As a result, inhibition was detected in 50 and 60 msec ISIs after Goggle_LED conditioning stimulation alone (p = 0.005; p = 0.007). However, in 110 ms ISI there was no statistically significant difference (p = 0.077). After dual conditioning stimulation in goggle_LED and somatosensory-electrical conditions, significant difference (inhibition) was observed in responses to all other ISIs, while no significant difference (inhibition) was observed in 110ms (p = 0.053). In 50 and 60ms ISIs did not reach statistical significance, but an increase in inhibition was observed according to electrical conditioning-stimulation alone (p = 0.051; p = 0.069).