The Brain is Not Flat: Conformal Electrode Arrays Diminish Complications of Subdural Electrode Implantation, A Series of 117 Cases

Mosher

et al. 2021

Preprint

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Intracranial electroencephalographic (icEEG) recordings provide invaluable insights into neural dynamics in humans due to their unmatched spatiotemporal resolution. Yet, such recordings reflect the combined activity of multiple underlying generators, confounding the ability to resolve spatially distinct neural sources. To empirically quantify the listening zone of icEEG recordings, we computed the correlations between signals as a function of distance (expressed as full width at half maximum; FWHM) between 8,752 recording sites in 71 patients implanted with either subdural electrodes (SDE), stereo-encephalography electrodes (sEEG), or high-density sEEG electrodes. As expected, for both SDE and sEEG electrodes, higher frequency signals exhibited a sharper fall off relative to lower frequency signals. For broadband high gamma (BHG) activity, the mean FWHM of SDEs (6.6 ± 2.5 mm) and sEEGs in gray matter (7.14 ± 1.7 mm) was not significantly different, however the FWHM for low frequencies recorded by sEEGs was 2.45 mm smaller than SDEs. White matter sEEG electrodes showed much lower power for frequencies 17 to 200 Hz (q < 0.01) and a much broader decay (11.3 ± 3.2 mm) than gray matter electrodes (7.14 ± 1.7 mm). The use of a bipolar referencing scheme significantly lowered FWHM for sEEG electrodes, as compared with a white matter reference or a common average reference. These results outline the influence of array design, spectral bands, and referencing schema on local field potential recordings and source localization in icEEG recordings in humans. The metrics we derive have immediate relevance to the analysis and interpretation of both cognitive and epileptic data.

Section: Methodsmentioning

confidence: 99%

The Listening Zone of Human Electrocorticographic Field Potential Recordings

Mosher

et al. 2021

Preprint

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“…Electrode Implantation and Data Recording: Data were acquired using either subdural grid electrodes (SDEs; 14 patients) or stereotactically placed depth electrodes (sEEGs; 68 patients). SDEs were subdural platinum-iridium electrodes embedded in a silicone elastomer sheet (PMT Corporation; tophat design; 3mm diameter cortical contact), surgically implanted via a craniotomy following previously described methods (Pieters et al, 2013;Tandon, 2012;Tong et al, 2020). sEEGs were implanted using a Robotic Surgical Assistant (ROSA; Medtech, Montpellier, France) (Rollo et al, 2020;Tandon et al, 2019).…”

Section: Methodsmentioning

confidence: 99%

Event-Related Phase Synchronization Propagates Rapidly across Human Ventral Visual Cortex

Forseth

Rollo

et al. 2021

Preprint

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Visual inputs to early visual cortex integrate with semantic, linguistic and memory inputs in higher visual cortex, in a manner that is rapid and accurate, and enables complex computations such as face recognition and word reading. This implies the existence of fundamental organizational principles that enable such efficiency. To elaborate on this, we performed intracranial recordings in 82 individuals while they performed tasks of varying visual and cognitive complexity. We discovered that visual inputs induce highly organized posterior-to-anterior propagating patterns of phase modulation across the ventral occipitotemporal cortex. At individual electrodes there was a stereotyped temporal pattern of phase progression following both stimulus onset and offset, consistent across trials and tasks. The phase of low frequency activity in anterior regions was predicted by the prior phase in posterior cortical regions. This spatiotemporal propagation of phase likely serves as a feed-forward organizational influence enabling the integration of information across the ventral visual stream. This phase modulation manifests as the early components of the event related potential; one of the most commonly used measures in human electrophysiology. These findings illuminate fundamental organizational principles of the higher order visual system that enable the rapid recognition and characterization of a variety of inputs.

“…1B). SDEs were subdural platinum-iridium electrodes embedded in a silicone elastomer sheet (PMT Corporation; top-hat design; 3mm diameter cortical contact), and were surgically implanted via a craniotomy (Conner et al, 2011;Pieters et al, 2013;Tong et al, 2020;Kohlhase et al, 2021). sEEGs were implanted using a Robotic Surgical Assistant (ROSA; Medtech, Montpellier, France) (Rollo et al, 2020;McCarty et al, 2021).…”

Section: Methodsmentioning

confidence: 99%

Minimal phrase composition revealed by intracranial recordings

Murphy

et al. 2021

Preprint

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The ability to comprehend meaningful phrases is an essential component of language. Here we evaluate a minimal compositional scheme – the ‘red-boat’ paradigm – using intracranial recordings to map the process of semantic composition in phrase structure comprehension. 18 human participants, implanted with penetrating depth or surface subdural intracranial electrode for the evaluation of medically refractory epilepsy, were presented with auditory recordings of adjective-noun, pseudoword-noun and adjective-pseudoword phrases before being presented with a colored drawing, and were asked to judge whether the phrase matched the object presented. Significantly greater broadband gamma activity (70-150Hz) occurred in temporo-occipital junction (TOJ) and posterior middle temporal gyrus (pMTG) for pseudowords over words (300-700ms post-onset) in both first- and second-word positions. Greater inter-trial phase coherence (8-12Hz) was found for words than for pseudowords in posterior superior temporal gyrus (pSTG). Isolating phrase structure sensitivity, we identified a portion of TOJ and posterior superior temporal sulcus (pSTS) that showed increased gamma activity for phrase composition than for non-composition, while left anterior temporal lobe (ATL) showed greater low frequency (2-15Hz) activity for phrase composition, likely coordinating distributed semantic representations. Greater functional connectivity between pSTS-TOJ and pars triangularis, and between pSTS-TOJ and ATL, was also found for phrase composition. STG, ATL and pars triangularis were found to encode anticipation of composition in the beta band (15-30Hz), and alpha (8-12Hz) power increases in ATL were also linked to anticipation. These results indicate that pSTS-TOJ appears to be crucial hub in the network responsible for the retrieval and computation of minimal phrases, and that anticipation of such composition is encoded in fronto-temporal regions.