Delineation of somatosensory finger areas using vibrotactile stimulation, an ECoG study

Abstract

BackgroundIn surgical planning for epileptic focus resection, functional mapping of eloquent cortex is attained through direct electrical stimulation of the brain. This procedure is uncomfortable, can trigger seizures or nausea, and relies on subjective evaluation. We hypothesize that a method combining vibrotactile stimulation and statistical clustering may provide improved somatosensory mapping.MethodsSeven pediatric candidates for surgical resection underwent a task in which their fingers were independently stimulated using a custom designed finger pad, during electrocorticographic monitoring. A cluster‐based statistical analysis was then performed to localize the elicited activity on the recording grids.ResultsMid‐Gamma clusters (65–115 Hz) arose in areas consistent with anatomical predictions as well as clinical findings, with five subjects presenting a somatotopic organization of the fingers. This process allowed us to delineate finger representation even in patients who were sleeping, with strong interictal activity, or when electrical stimulation did not successfully locate eloquent areas.ConclusionsWe suggest that this scheme, relying on the endogenous neural response rather than exogenous electrical activation, could eventually be extended to map other sensory areas and provide a faster and more objective map to better anticipate outcomes of surgical resection.

Brain changes following four weeks of unimanual motor training: Evidence from behavior, neural stimulation, cortical thickness, and functional MRI

“…Specifically, the location of clusters in the pre‐ and post‐central gyri were relatively consistent with our fMRI maps, our TMS maps (Fig. ), and with areas responsible for sensorimotor representation of the fingers elucidated through electrocorticographic and brain stimulation techniques [Penfield and Boldrey, ; Wahnoun et al, ]. The neighboring clusters seen in the right SMA were also within the TMS and fMRI maps from our study, and consistent with previous findings that this area plays a role in motor training [Taubert et al, ].…”

“…Although these five clusters did not survive multiple comparisons correction ( P < 0.05 FWE) all changes were observed in regions that are likely to be involved with motor tasks, and all were in the right (“trained”) hemisphere. Notably, clusters at the pre‐ and postcentral gyri were consistent with the expected location of sensory and motor finger representations [Penfield and Boldrey, ; Wahnoun et al, ], and close to peaks in the (post time point) TMS and fMRI maps. All clusters were within the group‐wise region of successful TMS excitation, and all but the prefrontal cluster were consistent with regions of group‐wise fMRI activation.…”

Vibrotactile Discrimination Training Affects Brain Connectivity in Profoundly Deaf Individuals

“…Using magnetoencephalography (MEG), Caetano and Jousmäki (2006) demonstrated the convergence of vibrotactile input on the superior temporal cortex of normal-hearing adults, as had been reported previously in a congenitally deaf adult ( Levänen et al, 1998 ). Recently, a vibrotactile-related endogenous neural response was mapped for purposes of surgical resection ( Wahnoun et al, 2015 ). Hegner et al (2010) found that different neuronal mechanisms underlie tactile and vibrotactile cortical processing, in which cortical representations vary depending on the nature of the stimuli.…”

Measuring motor-training induced neuroplasticity using diffusion and functional MRI: a sensitive, pathology-robust approach

“…The location of clusters in the pre-and post-central gyri were consistent with our fMRI maps, our TMS maps ( Figure 20), and with areas responsible for sensorimotor representation of the fingers elucidated through electrocorticographic and brain stimulation techniques. 233,234 The neighbouring clusters seen in the right SMA were also within the TMS and fMRI maps from our study, and consistent with previous findings that this area plays a role in motor learning. 237 That these changes appeared near the peaks of fMRI and TMS maps adds further credibility to the suggestion that changes in fMRI and TMS patterns were a reflection of altered neurite organisation, density, and/or connection strength in regions that, at baseline, were already predominantly responsible for execution of the (to-be) learned sequence, rather than altered responsibility of surrounding areas.…”

“…Although these five clusters did not survive multiple comparisons correction (p<0.05 FWE) all changes were observed in regions that are likely to be involved with motor tasks, and all were in the right ('trained') hemisphere. Notably, clusters at the pre-and postcentral gyri were consistent with the expected location of sensory and motor finger representations, 233,234 and close to peaks in the (post time-point) TMS and fMRI maps. All clusters were within the group-wise region of successful TMS excitation, and all but the prefrontal cluster were consistent with regions of group-wise fMRI activation.…”