The role of delta and theta oscillations during ego-motion in healthy adult volunteers

Abstract

The successful cortical processing of multisensory input typically requires the integration of data represented in different reference systems to perform many fundamental tasks, such as bipedal locomotion. Animal studies have provided insights into the integration processes performed by the neocortex and have identified region specific tuning curves for different reference frames during ego-motion. Yet, there remains almost no data on this topic in humans.In this study, an experiment originally performed in animal research with the aim to identify brain regions modulated by the position of the head and eyes relative to a translational ego-motion was adapted for humans. Subjects sitting on a motion platform were accelerated along a translational pathway with either eyes and head aligned or a 20° yaw-plane offset relative to the motion direction while EEG was recorded.Using a distributed source localization approach, it was found that activity in area PFm, a part of Brodmann area 40, was modulated by the congruency of translational motion direction, eye, and head position. In addition, an asymmetry between the hemispheres in the opercular-insular region was observed during the cortical processing of the vestibular input. A frequency specific analysis revealed that low-frequency oscillations in the delta- and theta-band are modulated by vestibular stimulation. Source-localization estimated that the observed low-frequency oscillations are generated by vestibular core-regions, such as the parieto-opercular region and frontal areas like the mid-orbital gyrus and the medial frontal gyrus.

Vestibular-Evoked Cerebral Potentials

“…By contrast, event-related synchronizations/desynchronizations are time-locked events, but not phase-locked events, reflecting more neuronal and synaptic characteristics, network connectivity, and modulation on more or less extended neuronal assemblies ( 220 ). A few studies investigated both VestEPs and responses in the time-frequency domain ( 32 , 111 , 166 , 167 , 171 ). Rotations were found to induce alpha rhythm desynchronization in central and parietal scalp regions ( 32 , 171 ).…”

“…More recent studies using body translations revealed a positive component with a peak latency of 199 ms, best observed under electrode Cz [( 33 , 166 , 167 ); Figure 5B ]. As for the n80, the p199 amplitude increased with body acceleration and this increase was best explained by increased activity in the cingulate sulcus visual area.…”

“…This is consistent with fMRI studies showing activity in the cingulate cortex following CVS ( 75 , 164 , 165 ) and GVS ( 89 ). Other studies reported positive individual components around 40 ms following whole-body rotations [( 163 ); 38.9 ms] and translations [( 33 , 166 , 167 ); p38.2 ms under parietal electrodes]. More recently, IAS on the left mastoid was also found to evoke n25, p40, and n53 components under Bz, an electrode placed over the cerebellum, two rows below Iz at the midline [( 150 ); following a nomenclature proposed by Heine et al ( 168 )].…”

“…Whole-body translation evoked the n80, a negative component with a peak latency of 80 ms [( 33 , 166 , 167 ); Figure 5B ]. The n80 was most prominent under frontal electrodes, but a weaker occipital positivity was also observed with the same latency.…”

“…Various responses have been described within the 300–500 ms time window after active ( 58 , 59 ) and passive body rotations ( 32 , 44 , 47 – 49 , 51 , 52 , 171 , 174 , 176 , 185 ), as well as after body translation ( 33 , 166 , 167 , 186 ). A seminal study compared human responses to animal responses that were already accepted as vestibular in origin ( 48 ).…”