Left Posterior Parietal Cortex Research Articles

Experimental Manipulation of the Bilateral Posterior Parietal Cortex Strengthens Associative Memory in Healthy Participants: A Continuous Theta-burst Stimulation.

To test whether targeting left and right posterior parietal cortex (PPC) with continuous theta-burst stimulation (cTBS) in healthy adults would strengthen associative memory (AM) performance. This study consisted of two experiments (a behavioral experiment and a formal experiment during each of the two experimental sessions). In Experiment 1, 18 adults (one male, age = 22.83 ± 3.92 years) were included in the behavioral phase and 18 adults (seven males, age = 40.11 ± 12.27 years) in the stimulation phase. There were 120 neutral facial images paired with 120 two-character nouns and then divided into six test versions (10 male faces and 10 female faces paired with 20 different nouns were considered as one version). In the behavioral experiment, participants were tested by six-version tests to assess memory materials, and in the formal experiment, participants' face-word AM performance was measured by certified tests based on a cued recall paradigm. Furthermore, 30 adults (seven males, age = 20.97 ± 1.85 years) and 15 adults (five males, age = 22.27 ± 1.29 years) participated in Experiment 2, respectively. Stimuli and procedure were the same as in Experiment 1, but the AM test was based on a forced-choice paradigm. Experiment 1 did not yield anticipated outcomes; Experiment 2 showed that cTBS of left and right PPC strengthened the AM performance compared with the control condition. In conclusion, cTBS to left and right PPC improved AM in healthy adults, which provided further experimental evidence for strengthening AM by cTBS.

Examining the Effect of Noninvasive Brain Stimulation on Hemispheric Lateralization of Motor Learning During a Functional Fine Motor Task

Abstract Date Presented 03/23/24 This study explores how noninvasive brain stimulation of the left and right posterior parietal cortex influences bilateral fine motor control. Results suggest distinct effects on speed and accuracy to help understand fine motor control modulation. Primary Author and Speaker: Sydney C. Sharp Additional Authors and Speakers: Brooke Dexheimer

Alterations in electroencephalographic functional connectivity in individuals with major depressive disorder: a resting-state electroencephalogram study.

Major depressive disorder (MDD) is the leading cause of disability among all mental illnesses with increasing prevalence. The diagnosis of MDD is susceptible to interference by several factors, which has led to a trend of exploring objective biomarkers. Electroencephalography (EEG) is a non-invasive procedure that is being gradually applied to detect and diagnose MDD through some features such as functional connectivity (FC). In this research, we analyzed the resting-state EEG of patients with MDD and healthy controls (HCs) in both eyes-open (EO) and eyes-closed (EC) conditions. The phase locking value (PLV) method was utilized to explore the connection and synchronization of neuronal activities spatiotemporally between different brain regions. We compared the PLV between participants with MDD and HCs in five frequency bands (theta, 4-8 Hz; alpha, 8-12 Hz; beta1, 12-16 Hz; beta2, 16-24 Hz; and beta3, 24-40 Hz) and further analyzed the correlation between the PLV of connections with significant differences and the severity of depression (via the scores of 17-item Hamilton Depression Rating Scale, HDRS-17). During the EO period, lower PLVs were found in the right temporal-left midline occipital cortex (RT-LMOC; theta, alpha, beta1, and beta2) and posterior parietal-right temporal cortex (PP-RT; beta1 and beta2) in the MDD group compared with the HC group, while PLVs were higher in the MDD group in LT-LMOC (beta2). During the EC period, for the MDD group, lower theta and beta (beta1, beta2, and beta3) PLVs were found in PP-RT, as well as lower theta, alpha, and beta (beta1, beta2, and beta3) PLVs in RT-LMOC. Additionally, in the left midline frontal cortex-right temporal cortex (LMFC-RT) and posterior parietal cortex-right temporal cortex (PP-RMOC), higher PLVs were observed in beta2. There were no significant correlations between PLVs and HDRS-17 scores when connections with significantly different PLVs (all p > 0.05) were checked. Our study confirmed the presence of differences in FC between patients with MDD and healthy individuals. Lower PLVs in the connection of the right temporal-left occipital cortex were mostly observed, whereas an increase in PLVs was observed in patients with MDD in the connections of the left temporal with occipital lobe (EO), the circuits of the frontal-temporal lobe, and the parietal-occipital lobe. The trends in FC involved in this study were not correlated with the level of depression. The study was limited due to the lack of further analysis of confounding factors and follow-up data. Future studies with large-sampled and long-term designs are needed to further explore the distinguishable features of EEG FC in individuals with MDD.

Brain activity during Stroop task performance at age 74 after exposure to the Dutch famine during early gestation

ObjectivePoorer performance on the Stroop task has been reported after prenatal famine exposure at age 58, potentially indicating cognitive decline. We investigated whether brain activation during Stroop task performance at age 74 differed between individuals exposed to famine prenatally, individuals born before and individuals conceived after the famine. MethodIn the Dutch famine birth cohort, we performed a Stroop task fMRI study of individuals exposed (n = 22) or unexposed (born before (n = 18) or conceived after (n = 25)) to famine in early gestation. We studied group differences in task-related mean activation of the dorsolateral prefrontal cortex (DLPFC), anterior cingulate cortex (ACC) and posterior parietal cortex (PPC). Additionally, we explored potential disconnectivity of the DLPFC using psychophysiological interaction analysis. ResultsWe observed similar activation patterns in the DLPFC, ACC and PPC in individuals born before and individuals exposed to famine, while individuals conceived after famine had generally higher activation patterns. However, activation patterns were not significantly different between groups. Task-related decreases in connectivity were observed between left DLPFC-left PPC and right DLPFC-right PPC, but were not significantly different between groups. ConclusionsAlthough not statistically significant, the observed patterns of activation may reflect a combined effect of general brain aging and prenatal famine exposure.

Effect of dopamine on limbic network connectivity at rest in Parkinson's disease patients with freezing of gait.

Freezing of gait (FOG) in Parkinson's disease (PD) has a poorly understood pathophysiology, which hinders treatment development. Recent work showed a dysfunctional fronto-striato-limbic circuitry at rest in PD freezers compared to non-freezers in the dopamine "OFF" state. While other studies found that dopaminergic replacement therapy alters functional brain organization in PD, the specific effect of dopamine medication on fronto-striato-limbic functional connectivity in freezers remains unclear. To evaluate how dopamine therapy alters resting state functional connectivity (rsFC) of the fronto-striato-limbic circuitry in PD freezers, and whether the degree of connectivity change is related to freezing severity and anxiety. Twenty-three PD FOG patients underwent MRI at rest (rsfMRI) in their clinically defined "OFF" and "ON" dopaminergic medication states. A seed-to-seed based analysis was performed between a priori defined limbic circuitry ROIs. Functional connectivity was compared between OFF and ON states. A secondary correlation analyses evaluated the relationship between Hospital Anxiety and Depression Scale (HADS)-Anxiety) and FOG Questionnaire with changes in rsFC from OFF to ON. PD freezers' OFF compared to ON showed increased functional coupling between the right hippocampus and right caudate nucleus, and between the left putamen and left posterior parietal cortex (PPC). A negative association was found between HADS-Anxiety and the rsFC change from OFF to ON between the left amygdala and left prefrontal cortex, and left putamen and left PPC. These findings suggest that dopaminergic medication partially modulates the frontoparietal-limbic-striatal circuitry in PD freezers, and that the influence of medication on the amygdala, may be related to clinical anxiety in freezer.

Functional MRI evaluation of hyperbaric oxygen therapy’s effect on hand motor recovery in a chronic post-stroke patient: a case report and physiological discussion

The objective of the case report was to evaluate a specific HBOT protocol as an effective treatment for stroke rehabilitation, specifically improving hand motor function in chronic post-stroke patients. Stroke is the second leading cause of long-term disability worldwide. About 80% of individuals with acute stroke present upper-limb motor impairment, and 50–60% will have persistent disability or weakness at the chronic phase. Impaired upper-limb motor function is highly associated with low self-care ability, limited mobility and poor quality of life. In recent years, there has been evidence of the neuroplasticity effects of HBOT, and HBOT was found to induce neuroplasticity in chronic stages, even years after brain injury. While the healthcare system is primarily focused on teaching patients to live with their impairments, this case report evaluates the effect of a specific hyperbaric oxygen therapy (HBOT) protocol on true stroke rehabilitation, specifically, improving upper-limb function. This case report studied motor task functional MRI (fMRI) activation and resting-state functional connectivity (rsFC) in a 61-year-old right-handed male patient who suffered hemiparesis and physical weakness in the right upper limb two years after his acute insult, pre- and post-treatment of 60 daily HBOT sessions. Motor functions were assessed at baseline and after the treatment using the Fugl–Meyer assessment (FMA) and the handgrip maximum voluntary contraction (MVC). Following the HBOT protocol, the patient’s FMA score improved from 17 (severe impairment) to 31 (moderate impairment), and there was an increase in fMRI activation in both the supplementary motor cortex (SMA) and the premotor cortex (PMA) bilaterally during trials involving the right hand. The lateralization index (LI) decreased from 1 to 0.63, demonstrating the recruitment of the contralesional hemisphere. The region of interest, ROI-to-ROI, analysis revealed increased post-intervention inter-hemispheric connectivity (P = 0.002) and a between-network connectivity increase (z-score: 0.35 ± 0.21 to 0.41 ± 0.21, P < 0.0001). Seed-to-voxel-based rsFC analysis using the right SMA as seed showed increased connectivity to the left posterior parietal cortex, the left primary somatosensory cortex and the premotor cortex. This case report provides additional insights into HBOT-induced brain plasticity and functional improvement in chronic post-stroke patients, and shows HBOT’s potential as an effective, valuable treatment option for those suffering with lingering symptoms after a stroke. This work was conducted by a research team at the Sagol Center for Hyperbaric Medicine and Research at Shamir Medical Center and Tel Aviv University, and published in Frontiers in Neurology. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Site Dependency of Anodal Transcranial Direct-Current Stimulation on Reaction Time and Transfer of Learning during a Sequential Visual Isometric Pinch Task.

Considering the advantages of brain stimulation techniques in detecting the role of different areas of the brain in human sensorimotor behaviors, we used anodal transcranial direct-current stimulation (a-tDCS) over three different brain sites of the frontoparietal cortex (FPC) in healthy participants to elucidate the role of these three brain areas of the FPC on reaction time (RT) during a sequential visual isometric pinch task (SVIPT). We also aimed to assess if the stimulation of these cortical sites affects the transfer of learning during SVIPT. A total of 48 right-handed healthy participants were randomly assigned to one of the four a-tDCS groups: (1) left primary motor cortex (M1), (2) left dorsolateral prefrontal cortex (DLPFC), (3) left posterior parietal cortex (PPC), and (4) sham. A-tDCS (0.3 mA, 20 min) was applied concurrently with the SVIPT, in which the participants precisely controlled their forces to reach seven different target forces from 10 to 40% of the maximum voluntary contraction (MVC) presented on a computer screen with the right dominant hand. Four test blocks were randomly performed at the baseline and 15 min after the intervention, including sequence and random blocks with either hand. Our results showed significant elongations in the ratio of RTs between the M1 and sham groups in the sequence blocks of both the right-trained and left-untrained hands. No significant differences were found between the DLPFC and sham groups and the PPC and sham groups in RT measurements within the SVIPT. Our findings suggest that RT improvement within implicit learning of an SVIPT is not mediated by single-session a-tDCS over M1, DLPFC, or PPC. Further research is needed to understand the optimal characteristics of tDCS and stimulation sites to modulate reaction time in a precision control task such as an SVIPT.

Bypassing input to V1 in visual awareness: A TMS-EROS investigation

Early visual cortex (V1–V3) is believed to be critical for normal visual awareness by providing the necessary feedforward input. However, it remains unclear whether visual awareness can occur without further involvement of early visual cortex, such as re-entrant feedback. It has been challenging to determine the importance of feedback activity to these areas because of the difficulties in dissociating this activity from the initial feedforward activity. Here, we applied single-pulse transcranial magnetic stimulation (TMS) over the left posterior parietal cortex to elicit phosphenes in the absence of direct visual input to early visual cortex. Immediate neural activity after the TMS pulse was assessed using the event-related optical signal (EROS), which can measure activity under the TMS coil without artifacts. Our results show that: 1) The activity in posterior parietal cortex 50 ms after TMS was related to phosphene awareness, and 2) Activity related to awareness was observed in a small portion of V1 140 ms after TMS, but in contrast (3) Activity in V2 was a more robust correlate of awareness. Together, these results are consistent with interactive models proposing that sustained and recurrent loops of activity between cortical areas are necessary for visual awareness to emerge. In addition, we observed phosphene-related activations of the anteromedial cuneus and lateral occipital cortex, suggesting a functional network subserving awareness comprising these regions, the parietal cortex and early visual cortex.

Impaired flexible reward learning in ADHD patients is associated with blunted reinforcement sensitivity and neural signals in ventral striatum and parietal cortex

Reward-based learning and decision-making are prime candidates to understand symptoms of attention deficit hyperactivity disorder (ADHD). However, only limited evidence is available regarding the neurocomputational underpinnings of the alterations seen in ADHD. This concerns flexible behavioral adaption in dynamically changing environments, which is challenging for individuals with ADHD. One previous study points to elevated choice switching in adolescent ADHD, which was accompanied by disrupted learning signals in medial prefrontal cortex.Here, we investigated young adults with ADHD (n = 17) as compared to age- and sex-matched controls (n = 17) using a probabilistic reversal learning experiment during functional magnetic resonance imaging (fMRI). The task requires continuous learning to guide flexible behavioral adaptation to changing reward contingencies. To disentangle the neurocomputational underpinnings of the behavioral data, we used reinforcement learning (RL) models, which informed the analysis of fMRI data.ADHD patients performed worse than controls particularly in trials before reversals, i.e., when reward contingencies were stable. This pattern resulted from ‘noisy’ choice switching regardless of previous feedback. RL modelling showed decreased reinforcement sensitivity and enhanced learning rates for negative feedback in ADHD patients. At the neural level, this was reflected in a diminished representation of choice probability in the left posterior parietal cortex in ADHD. Moreover, modelling showed a marginal reduction of learning about the unchosen option, which was paralleled by a marginal reduction in learning signals incorporating the unchosen option in the left ventral striatum.Taken together, we show that impaired flexible behavior in ADHD is due to excessive choice switching (‘hyper-flexibility’), which can be detrimental or beneficial depending on the learning environment. Computationally, this resulted from blunted sensitivity to reinforcement of which we detected neural correlates in the attention-control network, specifically in the parietal cortex. These neurocomputational findings remain preliminary due to the relatively small sample size.

Fronto-parietal theta high-definition transcranial alternating current stimulation may modulate working memory under postural control conditions in young healthy adults.

This study aimed to investigate the immediate effects of fronto-parietal θ HD-tACS on a dual task of working memory-postural control. In this within-subject cross-over pilot study, we assessed the effects of 20 min of 6 Hz-tACS targeting both the left dorsolateral prefrontal cortex (lDLPFC) and posterior parietal cortex (PPC) in 20 healthy adults (age: 21.6 ± 1.3 years). During each session, single- and dual-task behavioral tests (working memory single-task, static tandem standing, and a dual-task of working memory-postural control) and closed-eye resting-state EEG were assessed before and immediately after stimulation. Within the tACS group, we found a 5.3% significant decrease in working memory response time under the dual-task following tACS (t = -3.157, p = 0.005, Cohen's d = 0.742); phase synchronization analysis revealed a significant increase in the phase locking value (PLV) of θ band between F3 and P3 after tACS (p = 0.010, Cohen's d = 0.637). Correlation analyses revealed a significant correlation between increased rs-EEG θ power in the F3 and P3 channels and faster reaction time (r = -0.515, p = 0.02; r = -0.483, p = 0.031, respectively) in the dual-task working memory task after tACS. However, no differences were observed on either upright postural control performance or rs-EEG results (p-values <0.05). Fronto-parietal θ HD-tACS has the potential of being a neuromodulatory tool for improving working memory performance in dual-task situations, but its effect on the modulation of concurrently performed postural control tasks requires further investigation.

Unpacking reappraisal: A systematic review of fMRI studies of distancing and reinterpretation.

In recent decades, a substantial volume of work has examined the neural mechanisms of cognitive reappraisal. Distancing and reinterpretation are two frequently-used tactics through which reappraisal can be implemented. Theoretical frameworks and prior evidence have suggested that the specific tactic through which one employs reappraisal entails differential neural and psychological mechanisms. Thus, we were motivated to assess the neural mechanisms of this distinction by examining the overlap and differentiation exhibited by the neural correlates of distancing (specifically via objective appraisal) and reinterpretation. We analyzed 32 published fMRI studies in healthy adults using multilevel kernel density analysis. Results showed that distancing relative to reinterpretation uniquely recruited right DLPFC and left posterior parietal cortex, previously associated with mentalizing, selective attention, and working memory. Reinterpretation relative to distancing uniquely recruited left VLPFC, previously associated with response selection and inhibition. Further, distancing relative to reinterpretation was associated with greater prevalence of bilateral amygdala attenuation during reappraisal. Finally, a behavioral meta-analysis showed efficacy for both reappraisal tactics. These results are consistent with prior theoretical models for the functional neural architecture of reappraisal via distancing and reinterpretation and suggest potential future applications in region-of-interest specification and neural network analysis in studies focusing on specific reappraisal tactics.

Neuroimaging and Neurocognitive Outcomes in Older Patients with Multiple Myeloma Treated with Chemotherapy and Autologous Stem Cell Transplantation.

There is a paucity of research on treatment-related neurotoxicity in older adults with multiple myeloma (MM) treated with high-dose chemotherapy (HDC) and autologous SCT (HDC/ASCT), despite the increasing use of this regimen. We examined resting state functional connectivity (RSFC), gray matter (GM) volume, neurocognitive function (NF), and proinflammatory cytokines (PCy) in older patients with MM pre- and post-HDC/ASCT. Eighteen patients underwent MRI, NF tests, and serum PCy measurements prior to HDC/ASCT, and fifteen patients completed a follow up five-months post-HDC/ASCT. There were significant decreases in RSFC post-HDC/ASCT in (1) the central executive network (CEN) involving the left dorsolateral prefrontal cortex and right posterior parietal cortex (p = 0.022) and (2) the CEN involving the right posterior parietal cortex and the salience network involving the right dorsal anterior cingulate cortex (p = 0.029). There were no significant changes in GM or NF, except for improvements in attention (Digit Span Backward, p = 0.03). There were significant increases in several PCy post-HDC/ASCT (p ≤ 0.05). In conclusion, RSFC decreased in frontal, parietal, and cingulate cortices post-HDC/ASCT, NF was relatively stable, and several PCy increased. These findings are congruent with other studies in cancer patients and provide supporting evidence for the vulnerability of frontoparietal regions to chemotherapy's adverse effects.

Gamma connectivity predicts response to intermittent theta burst stimulation in Alzheimer’s disease: a randomized controlled trial

There is growing evidence that neural network dysfunction is a likely proximate cause of cognitive impairment in Alzheimer’s disease and may represent a promising therapeutic target. Here, we investigated whether a course of intermittent theta burst stimulation (iTBS) could modulate functional connectivity and cognition in mild to moderate Alzheimer’s. In a double-blind parallel randomized sham-controlled trial, 58 participants were randomized to either active or sham iTBS. Stimulation was applied to the left dorsolateral prefrontal cortex, right dorsolateral prefrontal cortex, left posterior parietal cortex, and right posterior parietal cortex in every treatment session. Neurobiological (electroencephalography), cognitive, and behavioral functional assessments were undertaken at baseline and end of treatment. Cognitive and functional assessments were also conducted at 3 (blinded) and 6 month (active group only) follow-ups. Active iTBS increased resting-state gamma connectivity and improved delayed recall on an episodic memory task. Both baseline gamma connectivity and change in gamma connectivity predicted improved delayed recall following active treatment. These findings support future research into iTBS for Alzheimer’s focusing on protocol optimization.

Behavioral and Electrocortical Response to a Sensorimotor Conflict in Individuals with Fibromyalgia.

People with fibromyalgia have been shown to experience more somatosensory disturbances than pain-free controls during sensorimotor conflicts (i.e., incongruence between visual and somatosensory feedback). Sensorimotor conflicts are known to disturb the integration of sensory information. This study aimed to assess the cerebral response and motor performance during a sensorimotor conflict in people with fibromyalgia. Twenty participants with fibromyalgia and twenty-three pain-free controls performed a drawing task including visual feedback that was either congruent with actual movement (and thus with somatosensory information) or incongruent with actual movement (i.e., conflict). Motor performance was measured according to tracing error, and electrocortical activity was recorded using electroencephalography. Motor performance was degraded during conflict for all participants but did not differ between groups. Time-frequency analysis showed that the conflict was associated with an increase in theta power (4-8 Hz) at conflict onset over the left posterior parietal cortex in participants with fibromyalgia but not in controls. This increase in theta suggests a stronger detection of conflict in participants with fibromyalgia, which was not accompanied by differences in motor performance in comparison to controls. This points to dissociation in individuals with fibromyalgia between an altered perception of action and a seemingly unaltered control of action.

Simple shape feature computation across modalities: convergence and divergence between the ventral and dorsal visual streams.

Shape processing, whether by seeing or touching, is pivotal to object recognition and manipulation. Although the low-level signals are initially processed by different modality-specific neural circuits, multimodal responses to object shapes have been reported along both ventral and dorsal visual pathways. To understand this transitional process, we conducted visual and haptic shape perception fMRI experiments to test basic shape features (i.e. curvature and rectilinear) across the visual pathways. Using a combination of region-of-interest-based support vector machine decoding analysis and voxel selection method, we found that the top visual-discriminative voxels in the left occipital cortex (OC) could also classify haptic shape features, and the top haptic-discriminative voxels in the left posterior parietal cortex (PPC) could also classify visual shape features. Furthermore, these voxels could decode shape features in a cross-modal manner, suggesting shared neural computation across visual and haptic modalities. In the univariate analysis, the top haptic-discriminative voxels in the left PPC showed haptic rectilinear feature preference, whereas the top visual-discriminative voxels in the left OC showed no significant shape feature preference in either of the two modalities. Together, these results suggest that mid-level shape features are represented in a modality-independent manner in both the ventral and dorsal streams.

Decoding and geometry of ten finger movements in human posterior parietal cortex and motor cortex

Objective. Enable neural control of individual prosthetic fingers for participants with upper-limb paralysis. Approach. Two tetraplegic participants were each implanted with a 96-channel array in the left posterior parietal cortex (PPC). One of the participants was additionally implanted with a 96-channel array near the hand knob of the left motor cortex (MC). Across tens of sessions, we recorded neural activity while the participants attempted to move individual fingers of the right hand. Offline, we classified attempted finger movements from neural firing rates using linear discriminant analysis with cross-validation. The participants then used the neural classifier online to control individual fingers of a brain–machine interface (BMI). Finally, we characterized the neural representational geometry during individual finger movements of both hands. Main Results. The two participants achieved 86% and 92% online accuracy during BMI control of the contralateral fingers (chance = 17%). Offline, a linear decoder achieved ten-finger decoding accuracies of 70% and 66% using respective PPC recordings and 75% using MC recordings (chance = 10%). In MC and in one PPC array, a factorized code linked corresponding finger movements of the contralateral and ipsilateral hands. Significance. This is the first study to decode both contralateral and ipsilateral finger movements from PPC. Online BMI control of contralateral fingers exceeded that of previous finger BMIs. PPC and MC signals can be used to control individual prosthetic fingers, which may contribute to a hand restoration strategy for people with tetraplegia.

Alpha-tACS Alters Attentional Control but not Cognitive Functions as Video Games Do: A Psychophysical Investigation based on the Theory of Viusal Attention.

Video game players' faster speed of information processing has been shown to coincide with altered posterior alpha power modulation, i.e., brain oscillatory activity around 10 Hz. Thus, it was proposed that improved cognitive processing in video game players may be related to differential alpha activity. However, a causal relationship thereof has not yet been established. We addressed this by conducting a non-invasive brain stimulation study to demonstrate that modulating alpha power using transcranial alternating current stimulation (tACS) may impact on speed of information processing. Furthermore, we aimed to show that this effect correlated with altered attentional control, e.g., visuospatial attention and/or top-down control processing, given that this has been suggested to contribute to video gaming effects. Therefore, we recruited 19 non-video game players to undergo one of five brain stimulation conditions while performing a visual short-term memory task at five different days, respectively. Thus, we applied tACS either at 10 Hz (alpha frequency) or at 16.18 Hz (control frequency) either over their left or right posterior parietal cortex (PPC) or a sham stimulation. Individuals' speed of information processing, visuospatial attention and top-down control processing were operationalized using a computational modeling approach based on the theory of visual attention. We found that alpha-tACS applied over individuals'left PPC altered their visuospatial attention orientation but not their speed of information processing. Thus, we were not able to establish a causal relationship between speed of information processing and altered visuospatial attention processing through alpha power modulation using non-invasive brain stimulation.

Abstract Number ‐ 266: Focal Cerebral CNS Vasculitis due to SARS‐CoV‐2 Infection

Introduction Several neurological manifestations of the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection, including anosmia, encephalopathy, and stroke, have been reported. We report a case of a 42‐year‐old man presenting with ischemic stroke due to cerebral vasculitis in the setting of SARS‐CoV‐2 infection. Methods Case report Results A 42‐year‐old man, recently diagnosed with SARS‐CoV‐2 infection, presented with nonfluent aphasia and right‐sided hemiparesis that started five hours prior. Neurological examination revealed nonfluent aphasia, right‐sided facial palsy, and hemiparesis. Computed tomography (CT) of the head showed left‐sided caudate infarct and early ischemic changes in the left putamen. CT angiography (CTA) revealed occlusion of the proximal left M1 segment. Patient’s symptoms rapidly improved and mechanical thrombectomy was not pursued. Patient was started on dual antiplatelet therapy with aspirin and clopidogrel. Magnetic resonance imaging (MRI) of the brain showed acute infarcts in the left posterior parietal, lentiform nucleus, and frontal cortex. CT of the chest revealed bilateral subsegmental pulmonary emboli. Patient was discharged on apixaban and atorvastatin daily, with mild residual aphasia. A month later, the patient returned with dysarthria and right‐sided paresthesia that began three hours prior. CTA showed severe left proximal M1 stenosis involving a longer segment. He was started on vasopressor. Symptoms resolved within 24 hours with residual mild aphasia. MRI brain revealed multiple foci of cortical infarcts within the left MCA territory with no diffusion/ perfusion mismatch. MRA head showed further pruning of the distal MCA branches within the left sylvian fissure with severe stenosis along the mid‐M1 and minimal flow anteriorly, with contrast enhancement at the site of the stenosis, suggestive of vasculitis. Autoimmune vasculitis panel was unremarkable. Due to suspicion of focal inflammatory vasculopathy related to recent SARS‐CoV‐2 infection, patient was started on intravenous methylprednisolone 1 gram daily for 5 days followed by a prednisone taper. MRA revealed improved blood flow in the left middle cerebral artery and branches. The was discharged on apixaban, aspirin, atorvastatin, and a prednisone taper with mild residual aphasia. Conclusions To our knowledge, this is the first reported case of CNS vasculitis associated with an underlying SARS‐CoV‐2 infection with radiographic improvement of blood flow in the affected vessel within 4 days of treatment with high‐dose steroids. This case supports the use of high‐dose steroids in patients with CNS vasculitis associated with SARS‐CoV‐2 to prevent further stroke burden.

Repetitive transcranial magnetic stimulation over the posterior parietal cortex improves functional recovery in nonresponsive patients: A crossover, randomized, double-blind, sham-controlled study.

Recent studies have shown that patients with disorders of consciousness (DoC) can benefit from repetitive transcranial magnetic stimulation (rTMS) therapy. The posterior parietal cortex (PPC) is becoming increasingly important in neuroscience research and clinical treatment for DoC as it plays a crucial role in the formation of human consciousness. However, the effect of rTMS on the PPC in improving consciousness recovery remains to be studied. We conducted a crossover, randomized, double-blind, sham-controlled clinical study to assess the efficacy and safety of 10 Hz rTMS over the left PPC in unresponsive patients. Twenty patients with unresponsive wakefulness syndrome were recruited. The participants were randomly divided into two groups: one group received active rTMS treatment for 10 consecutive days (n = 10) and the other group received sham treatment for the same period (n = 10). After a 10-day washout period, the groups crossed over and received the opposite treatment. The rTMS protocol involved the delivery of 2000 pulses/day at a frequency of 10 Hz, targeting the left PPC (P3 electrode sites) at 90% of the resting motor threshold. The primary outcome measure was the JFK Coma Recovery Scele-Revised (CRS-R), and evaluations were conducted blindly. EEG power spectrum assessments were also conducted simultaneously before and after each stage of the intervention. rTMS-active treatment resulted in a significant improvement in the CRS-R total score (F = 8.443, p = 0.009) and the relative alpha power (F = 11.166, p = 0.004) compared to sham treatment. Furthermore, 8 out of 20 patients classified as rTMS responders showed improvement and evolved to a minimally conscious state (MCS) as a result of active rTMS. The relative alpha power also significantly improved in responders (F = 26.372, p = 0.002) but not in non-responders (F = 0.704, p = 0.421). No adverse effects related to rTMS were reported in the study. This study suggests that 10 Hz rTMS over the left PPC can significantly improve functional recovery in unresponsive patients with DoC, with no reported side effects. www.ClinicalTrials.gov, identifier: NCT05187000.

Functional impairments in large-scale brain projects in opioid addiction

To assess the functional state of large-scale resting networks of the brain in patients with opioid intoxication. Thirty-one male subjects, aged 27.4+5.1 years, were studied. Resting state functional MRI was performed in 12 patients with heroin intoxication aged 29.1+5.9 years. The control group consisted of 16 healthy volunteers without bad habits aged 26.2+4.2 years. In the group of opioids intoxication, there is a decrease in the functional activity of the salience network with the executive control network and the default mode network of the brain (p<0.05) compared to the control group. A positive correlation of functional connections is found between the anterior cingulate cortex and the medial prefrontal cortex (T=2.74; p=0.041), which is not recorded in the control group. The functional connections between the default mode network and executive control are more highly represented in opioid intoxication in comparison with the control group (medial prefrontal cortex - left posterior parietal cortex T=7.5; p=0.001; medial prefrontal cortex - right posterior parietal cortex T=3.71; p=0.014; posterior cingulate cortex - left posterior parietal cortex T=6.15; p=0.002; posterior cingulate cortex - right posterior parietal cortex T=3.25; p=0.023; posterior cingulate cortex - right dorsolateral prefrontal cortex T=2.83; p=0.037). The results indicate that functional connections in large-scale resting networks are disrupted during opioid intoxication, which indicates a disturbance of the normal functional architectonics of the brain.