What does degeneration at the cervicothoracic junction tell us? A kinematic MRI study of 93 individuals.

PURPOSE: Current decision-making in multilevel cervical fusion weighs the potential to protect adjacent levels and reduce reoperation risk by crossing the cervicothoracic junction (C7/T1) against increased operative time and risk of complication. Careful planning is required, and the planned distal and adjacent levels should be assessed for degenerative disc disease (DDD). This study assessed whether DDD at the cervicothoracic junction was associated with DDD, disc height, translational motion, or angular variation in the adjacent superior (C6/C7) or inferior (T1/T2) levels. METHODS: This study retrospectively analyzed 93 cases with kinematic MRI. Cases were randomly selected from a database with inclusion criteria being no prior spine surgery and images having sufficient quality for analysis. DDD was assessed using Pfirrmann classification. Vertebral body bone marrow lesions were assessed using Modic changes. Disc height was measured at the mid-disc in neutral and extension. Translational motion and angular variation were calculated by assessing translational or angular motion segment integrity respectively in flexion and extension. Statistical associations were assessed with scatterplots and Kendall's tau. RESULTS: DDD at C7/T1 was positively associated with DDD at C6/C7 (tau = 0.53, p < 0.01) and T1/T2 (tau = 0.58, p < 0.01), with greater disc height in neutral position at T1/T2 (tau = 0.22, p < 0.01), and with greater disc height in extended position at C7/T1 (tau = 0.17, p = 0.04) and at T1/T2 (tau = 0.21, p < 0.01). DDD at C7/T1 was negatively associated with angular variation at C6/C7 (tau = - 0.23, p < 0.01). No association was appreciated between DDD at C7/T1 and translational motion. CONCLUSION: The association of DDD at the cervicothoracic junction with DDD at the adjacent levels emphasizes the necessity for careful selection of the distal level in multilevel fusion in the distal cervical spine.

Neuromodulation in Beta-Band Power Between Movement Execution and Inhibition in the Human Hippocampus.

INTRODUCTION: The hippocampus is thought to be involved in movement, but its precise role in movement execution and inhibition has not been well studied. Previous work with direct neural recordings has found beta-band (13-30 Hz) modulation in both movement execution and inhibition throughout the motor system, but the role of beta-band modulation in the hippocampus during movement inhibition is not well understood. Here, we perform a Go/No-Go reaching task in ten patients with medically refractory epilepsy to study human hippocampal beta-power changes during movement. MATERIALS AND METHODS: Ten epilepsy patients (5 female; ages 21-46) were implanted with intracranial depth electrodes for seizure monitoring and localization. Local field potentials were sampled at 2000 Hz during a Go/No-Go movement task. Comparison of beta-band power between Go and No-Go conditions was conducted using Wilcoxon signed-rank hypothesis testing for each patient. Sub-analyses were conducted to assess differences in the anterior vs posterior contacts, ipsilateral vs contralateral contacts, and male vs female beta-power values. RESULTS: Eight out of ten patients showed significant beta-power decreases during the Go movement response (p < 0.05) compared to baseline. Eight out of ten patients also showed significant beta-power increases in the No-Go condition, occurring in the absence of movement. No significant differences were noted between ipsilateral vs contralateral contacts nor in anterior vs posterior hippocampal contacts. Female participants had a higher task success rate than males and had significantly greater beta-power increases in the No-Go condition (p < 0.001). CONCLUSION: These findings indicate that increases in hippocampal beta power are associated with movement inhibition. To the best of our knowledge, this study is the first to report this phenomenon in the human hippocampus. The beta band may represent a state-change signal involved in motor processing. Future focus on the beta band in understanding human motor and impulse control will be vital.

Primary somatosensory cortex organization for engineering artificial somatosensation.

Somatosensory deficits from stroke, spinal cord injury, or other neurologic damage can lead to a significant degree of functional impairment. The primary (SI) and secondary (SII) somatosensory cortices encode information in a medial to lateral organization. SI is generally organized topographically, with more discrete cortical representations of specific body regions. SII regions corresponding to anatomical areas are less discrete and may represent a more functional rather than topographic organization. Human somatosensory research continues to map cortical areas of sensory processing with efforts primarily focused on hand and upper extremity information in SI. However, research into SII and other body regions is lacking. In this review, we synthesize the current state of knowledge regarding the cortical organization of human somatosensation and discuss potential applications for brain computer interface. In addition to accurate individualized mapping of cortical somatosensation, further research is required to uncover the neurophysiological mechanisms of how somatosensory information is encoded in the cortex.

Beta-band power modulation in the human amygdala differentiates between go/no-go responses in an arm-reaching task.

Objective. Traditionally known for its involvement in emotional processing, the amygdala's involvement in motor control remains relatively unexplored, with sparse investigations into the neural mechanisms governing amygdaloid motor movement and inhibition. This study aimed to characterize the amygdaloid beta-band (13-30 Hz) power between 'Go' and 'No-go' trials of an arm-reaching task.Approach. Ten participants with drug-resistant epilepsy implanted with stereoelectroencephalographic (SEEG) electrodes in the amygdala were enrolled in this study. SEEG data was recorded throughout discrete phases of a direct reach Go/No-go task, during which participants reached a touchscreen monitor or withheld movement based on a colored cue. Multitaper power analysis along with Wilcoxon signed-rank and Yates-correctedZtests were used to assess significant modulations of beta power between the Response and fixation (baseline) phases in the 'Go' and 'No-go' conditions.Main results. In the 'Go' condition, nine out of the ten participants showed a significant decrease in relative beta-band power during the Response phase (p⩽ 0.0499). In the 'No-go' condition, eight out of the ten participants presented a statistically significant increase in relative beta-band power during the response phase (p⩽ 0.0494). Four out of the eight participants with electrodes in the contralateral hemisphere and seven out of the eight participants with electrodes in the ipsilateral hemisphere presented significant modulation in beta-band power in both the 'Go' and 'No-go' conditions. At the group level, no significant differences were found between the contralateral and ipsilateral sides or between genders.Significance.This study reports beta-band power modulation in the human amygdala during voluntary movement in the setting of motor execution and inhibition. This finding supplements prior research in various brain regions associating beta-band power with motor control. The distinct beta-power modulation observed between these response conditions suggests involvement of amygdaloid oscillations in differentiating between motor inhibition and execution.

Beta-band power classification of go/no-go arm-reaching responses in the human hippocampus.

Objective.Can we classify movement execution and inhibition from hippocampal oscillations during arm-reaching tasks? Traditionally associated with memory encoding, spatial navigation, and motor sequence consolidation, the hippocampus has come under scrutiny for its potential role in movement processing. Stereotactic electroencephalography (SEEG) has provided a unique opportunity to study the neurophysiology of the human hippocampus during motor tasks. In this study, we assess the accuracy of discriminant functions, in combination with principal component analysis (PCA), in classifying between 'Go' and 'No-go' trials in a Go/No-go arm-reaching task.Approach.Our approach centers on capturing the modulation of beta-band (13-30 Hz) power from multiple SEEG contacts in the hippocampus and minimizing the dimensional complexity of channels and frequency bins. This study utilizes SEEG data from the human hippocampus of 10 participants diagnosed with epilepsy. Spectral power was computed during a 'center-out' Go/No-go arm-reaching task, where participants reached or withheld their hand based on a colored cue. PCA was used to reduce data dimension and isolate the highest-variance components within the beta band. The Silhouette score was employed to measure the quality of clustering between 'Go' and 'No-go' trials. The accuracy of five different discriminant functions was evaluated using cross-validation.Main results.The Diagonal-Quadratic model performed best of the 5 classification models, exhibiting the lowest error rate in all participants (median: 9.91%, average: 14.67%). PCA showed that the first two principal components collectively accounted for 54.83% of the total variance explained on average across all participants, ranging from 36.92% to 81.25% among participants.Significance.This study shows that PCA paired with a Diagonal-Quadratic model can be an effective method for classifying between Go/No-go trials from beta-band power in the hippocampus during arm-reaching responses. This emphasizes the significance of hippocampal beta-power modulation in motor control, unveiling its potential implications for brain-computer interface applications.

Stereotactic Frame-Based Electrode Insertion: The Accuracy of Increasingly Oblique Insertion Angles.

AIM: To investigate the relationship between planned drill approach angle and angular deviation of the stereotactically placed intracranial electrode tips. MATERIAL AND METHODS: Stereotactic electrode implantation was performed in 13 patients with drug resistant epilepsy. A total of 136 electrodes were included in our analysis. Stereotactic targets were planned on pre-operative magnetic resonance imaging (MRI) scans and implantation was carried out using a Cosman-Roberts-Wells stereotactic frame with the Ad-Tech drill guide and electrodes. Post implant electrode angles in the axial, coronal, and sagittal planes were determined from post-operative computerized tomography (CT) scans and compared with planned angles using Bland-Altman plots and linear regression. RESULTS: Qualitative assessment of correlation plots between planned and actual angles demonstrated a linear relationship for axial, coronal, and sagittal planes, with no overt angular deflection for any magnitude of the planned angle. CONCLUSION: The accuracy of CRW frame-based electrode placement using the Ad-Tech drill guide and electrodes is not significantly affected by the magnitude of the planning angle. Based on our results, oblique electrode insertion is a safe and accurate procedure.

Understanding the human conflict processing network: A review of the literature on direct neural recordings during performance of a modified stroop task.

The Stroop Task is a well-known neuropsychological task developed to investigate conflict processing in the human brain. Our group has utilized direct intracranial neural recordings in various brain regions during performance of a modified color-word Stroop Task to gain a mechanistic understanding of non-emotional human conflict processing. The purpose of this review article is to: 1) synthesize our own studies into a model of human conflict processing, 2) review the current literature on the Stroop Task and other conflict tasks to put our research in context, and 3) describe how these studies define a network in conflict processing. The figures presented are reprinted from our prior publications and key publications referenced in the manuscript. We summarize all studies to date that employ invasive intracranial recordings in humans during performance of conflict-inducing tasks. For our own studies, we analyzed local field potentials (LFPs) from patients with implanted stereotactic electroencephalography (SEEG) electrodes, and we observed intracortical oscillation patterns as well as intercortical temporal relationships in the hippocampus, amygdala, and orbitofrontal cortex (OFC) during the cue-processing phase of a modified Stroop Task. Our findings suggest that non-emotional human conflict processing involves modulation across multiple frequency bands within and between brain structures.

Theta low-gamma phase amplitude coupling in the human orbitofrontal cortex increases during a conflict-processing task.

Objective. The human orbitofrontal cortex (OFC) is involved in automatic response inhibition and conflict processing, but the mechanism of frequency-specific power changes that control these functions is unknown. Theta and gamma activity have been independently observed in the OFC during conflict processing, while theta-gamma interactions in other brain areas have been noted primarily in studies of memory. Within the OFC, it is possible that theta-gamma phase amplitude coupling (PAC) drives conflict processing. This study aims to characterize the coupled relationship between theta and gamma frequency bands in the OFC during conflict processing using a modified Stroop task.Approach. Eight epilepsy patients implanted with OFC stereotactic electroencephalography electrodes participated in a color-word modified Stroop task. PAC between theta phase and gamma amplitude was assessed to determine the timing and magnitude of neural oscillatory changes. Group analysis was conducted using a non-parametric cluster-permutationt-test on coherence values.Main results.Theta-low gamma (LG) PAC significantly increased in five out of eight patients during successful trials of the incongruent condition compared with the congruent condition. Significant increases in theta-LG PAC were most prominent during cue processing 200-800 ms after cue presentation. On group analysis, trial-averaged mean theta-LG PAC was statistically significantly greater in the incongruent condition compared to the congruent condition (p< 0.001, Cohen'sd= 0.51).Significance.For the first time, we report that OFC theta phase and LG amplitude coupling increases during conflict resolution. Given the delayed onset after cue presentation, OFC theta-LG PAC may contribute to conflict processing after conflict detection and before motor response. This explanation follows the hypothesis that global theta waves modulate local gamma signals. Understanding this relationship within the OFC will help further elucidate the neural mechanisms of human conflict resolution.

Baseline hippocampal beta band power is lower in the presence of movement uncertainty.

Objective.This study aimed to characterize hippocampal neural signatures of uncertainty by measuring beta band power in the period prior to movement cue.Approach. Participants with epilepsy were implanted with hippocampal depth electrodes for stereo electroencephalographic (SEEG) monitoring. Hippocampal beta (13-30 Hz) power changes have been observed during motor tasks such as the direct reach (DR) and Go/No-Go (GNG) tasks. The primary difference between the tasks is the presence of uncertainty about whether movement should be executed. Previous research on cortical responses to uncertainty has found that baseline beta power changes with uncertainty. SEEG data were sampled throughout phases of the DR and GNG tasks. Beta-band power during the fixation phase was compared between the DR and GNG task using a Wilcoxon rank sum test. This unpaired test was also used to analyze response times from cue to task completion between tasks.Main results.Eight patients who performed both reaching tasks were analyzed in this study. Movement response times in the GNG task were on average 210 milliseconds slower than in the DR task. All patients exhibited a significantly increased response latency in the GNG task compared to the DR task (Wilcoxon rank-sum p-value < 0.001). Six out of eight patients demonstrated statistically significant differences in beta power in single hippocampal contacts between the fixation phases of the GNG and DR tasks. At the group level, baseline beta power was significantly lower in the GNG task than in the DR task (Wilcoxon rank-sum p-value < 0.001).Significance. This novel study found that, in the presence of task uncertainty, baseline beta power in the hippocampus is lower than in its absence. This finding implicates movement uncertainty as an important factor in baseline hippocampal beta power during movement preparation.

Amygdaloid theta-band power increases during conflict processing in humans.

The amygdala is a medial temporal lobe structure known to be involved in processing emotional conflict. However, its role in processing non-emotional conflict is not well understood. Previous studies have utilized the Stroop Task to examine brain modulation of humans under the color-word conflict scenario, which is non-emotional conflict processing, and found hippocampal theta-band (4-7 Hz) modulation. This study aims to survey amygdaloid theta power changes during non-emotional conflict processing using intracranial depth electrodes in nine epileptic patients (3 female; age 20-62). All patients were asked to perform a modified Stroop task. During task performance, local field potential (LFP) data was recorded from macro contacts sampled at 2 K Hz and used for analysis. Mean theta power change from baseline was compared between the incongruent and congruent task condition groups using a paired sample t-test. Seven patients were available for analysis after artifact exclusion. In five out of seven patients, statistically significant increases in theta-band power from baseline were noted during the incongruent task condition (paired sample t-test p < 0.001), including one patient exhibiting theta power increases in both task conditions. Average response time was 1.07 s (failure trials) and 1.04 s (success trials). No speed-accuracy tradeoff was noted in this analysis. These findings indicate that human amygdaloid theta-band modulation may play a role in processing non-emotional conflict. It builds directly upon work suggesting that the amygdala processes emotional conflict and provides a neurophysiological mechanism for non-emotional conflict processing as well.