Control of working memory by phase-amplitude coupling of human hippocampal neurons.

Retaining information in working memory is a demanding process that relies on cognitive control to protect memoranda-specific persistent activity from interference1,2. However, how cognitive control regulates working memory storage is unclear. Here we show that interactions of frontal control and hippocampal persistent activity are coordinated by theta-gamma phase-amplitude coupling (TG-PAC). We recorded single neurons in the human medial temporal and frontal lobe while patients maintained multiple items in their working memory. In the hippocampus, TG-PAC was indicative of working memory load and quality. We identified cells that selectively spiked during nonlinear interactions of theta phase and gamma amplitude. The spike timing of these PAC neurons was coordinated with frontal theta activity when cognitive control demand was high. By introducing noise correlations with persistently active neurons in the hippocampus, PAC neurons shaped the geometry of the population code. This led to higher-fidelity representations of working memory content that were associated with improved behaviour. Our results support a multicomponent architecture of working memory1,2, with frontal control managing maintenance of working memory content in storage-related areas3-5. Within this framework, hippocampal TG-PAC integrates cognitive control and working memory storage across brain areas, thereby suggesting a potential mechanism for top-down control over sensory-driven processes.

Spontaneous sphenoid sinus meningocele with associated amenorrhea and headache: illustrative case.

BACKGROUND: Developmental meningoceles of the sphenoid sinus are uncommon. When encountered, they are often associated with cerebrospinal fluid (CSF) rhinorrhea. OBSERVATIONS: The authors present the case of a 27-year-old female with a large meningocele eroding through the sella turcica and sphenoid sinus into the nasopharynx. The patient presented with intractable headaches and amenorrhea without CSF rhinorrhea. LESSONS: The patient underwent an endoscopic endonasal transsphenoidal reduction of the meningocele with reelevation of the pituitary gland and skull base reconstruction with abdominal fat graft and nasoseptal flap.

Multimodal single-neuron, intracranial EEG, and fMRI brain responses during movie watching in human patients.

We present a multimodal dataset of intracranial recordings, fMRI, and eye tracking in 20 participants during movie watching. Recordings consist of single neurons, local field potential, and intracranial EEG activity acquired from depth electrodes targeting the amygdala, hippocampus, and medial frontal cortex implanted for monitoring of epileptic seizures. Participants watched an 8-min long excerpt from the video "Bang! You're Dead" and performed a recognition memory test for movie content. 3 T fMRI activity was recorded prior to surgery in 11 of these participants while performing the same task. This NWB- and BIDS-formatted dataset includes spike times, field potential activity, behavior, eye tracking, electrode locations, demographics, and functional and structural MRI scans. For technical validation, we provide signal quality metrics, assess eye tracking quality, behavior, the tuning of cells and high-frequency broadband power field potentials to familiarity and event boundaries, and show brain-wide inter-subject correlations for fMRI. This dataset will facilitate the investigation of brain activity during movie watching, recognition memory, and the neural basis of the fMRI-BOLD signal.

Encoding of Predictive Associations in Human Prefrontal and Medial Temporal Neurons During Pavlovian Appetitive Conditioning.

Pavlovian conditioning is thought to involve the formation of learned associations between stimuli and values, and between stimuli and specific features of outcomes. Here, we leveraged human single neuron recordings in ventromedial prefrontal, dorsomedial frontal, hippocampus, and amygdala while patients of both sexes performed an appetitive Pavlovian conditioning task probing both stimulus-value and stimulus-stimulus associations. Ventromedial prefrontal cortex encoded predictive value along with the amygdala, and also encoded predictions about the identity of stimuli that would subsequently be presented, suggesting a role for neurons in this region in encoding predictive information beyond value. Unsigned error signals were found in dorsomedial frontal areas and hippocampus, potentially supporting learning of non-value related outcome features. Our findings implicate distinct human prefrontal and medial temporal neuronal populations in mediating predictive associations which could partially support model-based mechanisms during Pavlovian conditioning.

Dataset of human-single neuron activity during a Sternberg working memory task.

We present a dataset of 1809 single neurons recorded from the human medial temporal lobe (amygdala and hippocampus) and medial frontal lobe (anterior cingulate cortex, pre-supplementary motor area, ventral medial prefrontal cortex) across 41 sessions from 21 patients that underwent seizure monitoring with depth electrodes. Subjects performed a screening task (907 neurons) to identify images for which highly selective cells were present. Subjects then performed a working memory task (902 neurons), in which they were sequentially presented with 1-3 images for which highly selective cells were present and, following a maintenance period, were asked if the probe was identical to one of the maintained images. This Neurodata Without Borders formatted dataset includes spike times, extracellular spike waveforms, stimuli presented, behavior, electrode locations, and subject demographics. As validation, we replicate previous findings on the selectivity of concept cells and their persistent activity during working memory maintenance. This large dataset of rare human single-neuron recordings and behavior enables the investigation of the neural mechanisms of working memory in humans.

CSF-Venous Fistula of the Clival Skull Base: A Unique Case Study and Literature Review.

An adolescent male presented with orthostatic headaches following head trauma. MRI showed cerebellar tonsil displacement and a bony defect in the clival skull base. Digital subtraction myelography (DSM) confirmed a cerebrospinal fluid-venous fistula (CVF). This was repaired endoscopically. CVFs cause uncontrolled flow of CSF into the venous system resulting in symptoms of intracranial hypotension. They're often difficult to identify on initial imaging. This is the first reported CVF originating in the central skull base, and the first treated via endoscopic trans-nasal approach. CVFs may elude initial imaging, making DSM crucial for unexplained spontaneous intracranial hypotension. Laryngoscope, 134:645-647, 2024.

A Prospective, Multicenter, Observational Study of Surgical vs Nonsurgical Management for Pituitary Apoplexy.

CONTEXT: Pituitary apoplexy (PA) has been traditionally considered a neurosurgical emergency, yet retrospective single-institution studies suggest similar outcomes among patients managed medically. OBJECTIVE: We established a multicenter, international prospective registry to compare presentation and outcomes in PA patients treated with surgery or medical management alone. METHODS: A centralized database captured demographics, comorbidities, clinical presentation, visual findings, hormonal status, and imaging features at admission. Treatment was determined independently by each site. Key outcomes included visual, oculomotor, and hormonal recovery, complications, and hospital length of stay. Outcomes were also compared based on time from symptom onset to surgery, and from admission or transfer to the treating center. Statistical testing compared treatment groups based on 2-sided hypotheses and P less than .05. RESULTS: A total of 100 consecutive PA patients from 12 hospitals were enrolled, and 97 (67 surgical and 30 medical) were evaluable. Demographics, clinical features, presenting symptoms, hormonal deficits, and imaging findings were similar between groups. Severe temporal visual field deficit was more common in surgical patients. At 3 and 6 months, hormonal, visual, and oculomotor outcomes were similar. Stratifying based on severity of visual fields demonstrated no difference in any outcome at 3 months. Timing of surgery did not affect outcomes. CONCLUSION: We found that medical and surgical management of PA yield similar 3-month outcomes. Although patients undergoing surgery had more severe visual field deficits, we could not clearly demonstrate that surgery led to better outcomes. Even without surgery, apoplectic tumor volumes regress substantially within 2 to 3 months, indicating that surgery is not always needed to reduce mass effect.

Endoscopic endonasal transclival clipping of a cerebellar arteriovenous malformation feeding vessel and associated aneurysm; a 2D operative video.

Positioned along the ventral surface of the pons, proximal superior cerebellar artery (SCA) aneurysms account for only 1.7% of all intracranial aneurysms [1]. Unlike more commonly encountered basilar artery aneurysms, patients often experience good outcomes when treated via endovascular coiling or surgical clipping [1,2]. These lesions frequently have a lateral projection and paucity of perforator arteries [2]. With further development of endoscopic endonasal techniques, access to this region is possible via a direct frontal exposure to the ventral brainstem, basilar artery and branching vessels. To date, there are only a limited number of reports describing an endoscopic endonasal transclival (EETC) approach for surgical clipping [3-5]. In this operative video, we detail the surgical clipping of a cerebellar arteriovenous malformation feeding vessel and an associated aneurysm using the EETC approach in a 59-year-old woman who presented with sudden onset of a severe headache. The feeding vessel and aneurysm's midline location, just below the take-off of the SCA made it a good candidate for this surgery. Major steps included in this video include 1) transsphenoidal exposure of and subsequent drilling of the clivus, 2) dural opening into the pre-pontine cistern and dissection of the aneurysm, 3) clipping of the aneurysm, and 4) multi-layered closure of the skull base defect. Overall, the patient tolerated the procedure well and was found to have no residual filling of the aneurysm or the AVM feeding vessel at 2-year follow-up. EETC is a viable surgical option for the treatment of aneurysm located along the midline of the pre-pontine cistern.

Abstract representations emerge in human hippocampal neurons during inference behavior.

Humans have the remarkable cognitive capacity to rapidly adapt to changing environments. Central to this capacity is the ability to form high-level, abstract representations that take advantage of regularities in the world to support generalization 1 . However, little is known about how these representations are encoded in populations of neurons, how they emerge through learning, and how they relate to behavior 2,3 . Here we characterized the representational geometry of populations of neurons (single-units) recorded in the hippocampus, amygdala, medial frontal cortex, and ventral temporal cortex of neurosurgical patients who are performing an inferential reasoning task. We find that only the neural representations formed in the hippocampus simultaneously encode multiple task variables in an abstract, or disentangled, format. This representational geometry is uniquely observed after patients learn to perform inference, and consisted of disentangled directly observable and discovered latent task variables. Interestingly, learning to perform inference by trial and error or through verbal instructions led to the formation of hippocampal representations with similar geometric properties. The observed relation between representational format and inference behavior suggests that abstract/disentangled representational geometries are important for complex cognition.

Diagnosis of Skin Disease in Moderately to Highly Pigmented Skin by Artificial Intelligence.

BACKGROUND: Triage of patients with skin diseases often includes an initial assessment by a nurse or general practitioner, followed by a dermatologist. Artificial intelligence (AI) systems have been reported to improve clinician ability to diagnose and triage skin conditions. Previous studies have also shown that diagnosis in patients with skin of color can be more challenging. PURPOSE: This study seeks to determine the performance of AI in the screening and triage of benign-neoplastic, malignant-neoplastic, and non-neoplastic skin conditions for Fitzpatrick skin types IV-VI. METHODS: A set of 163 non-standardized clinical photographs of skin disease manifestations from patients with Fitzpatrick skin types IV-VI were obtained through a publicly available dataset (Scale AI and MIT Research Lab, “Fitzpatrick 17 Dataset”). All photos were diagnosed by a specialist and categorized into three disease classes: benign-neoplastic, malignant-neoplastic, or non-neoplastic. There were 23, 14, and 122 cases of each disease class, respectively. RESULTS: Overall, the AI was able to classify the disease classes with a high degree of accuracy for the Top 1 diagnosis (86.50%). Based on its first prediction, the AI demonstrated the greatest accuracy when classifying non-neoplastic conditions (90.98%), high accuracy in detecting malignant-neoplastic conditions (77.78%), and moderate accuracy of classifying benign-neoplastic conditions (69.57%). CONCLUSION: The AI had an overall accuracy of 86.50% in diagnosing skin disease in Fitzpatrick skin types IV to VI. This is an improvement over reported clinician diagnostic accuracy of 44.3% in darker skin types. Incorporating AI into front-line screening of skin conditions could thereby assist in patient triage and shorten the time to accurate diagnosis. Schneider LG, Mamelak AJ, Tejani I, et al. Diagnosis of skin disease in moderately to highly pigmented skin by artificial intelligence. J Drugs Dermatol. 2023;22(7):647-652. doi:10.36849/JDD.7581.

Postoperative Obstructive Sleep Apnea Management Following Endoscopic Pituitary Surgery: A Systematic Review.

OBJECTIVE: There is currently no consensus on the appropriate timing of noninvasive positive pressure ventilation (PPV) resumption in patients with obstructive sleep apnea (OSA) after endoscopic pituitary surgery. We performed a systematic review of the literature to better assess the safety of early PPV use in OSA patients following surgery. METHODS: The study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Databases in English were searched using the keywords: "sleep apnea," "CPAP," "endoscopic," "skull base," "transsphenoidal" and "pituitary surgery." Case reports, editorials, reviews, meta-analyses, unpublished and abstract-only articles were all excluded. RESULTS: Five retrospective studies were identified, comprising 267 patients with OSA who underwent endoscopic endonasal pituitary surgery. The mean age of patients in four studies (n = 198) was 56.3 years (SD = 8.6) and the most common indication for surgery was pituitary adenoma resection. The timing of PPV resumption following surgery was reported in four studies (n = 130), with 29 patients receiving PPV therapy within two weeks. The pooled rate of postoperative cerebrospinal fluid leak associated with PPV resumption was 4.0% (95% CI: 1.3-6.7%) in three studies (n = 27) and there were no reports of pneumocephalus associated with PPV use in the early postoperative period (<2 weeks). CONCLUSIONS: Early resumption of PPV in OSA patients after endoscopic endonasal pituitary surgery appears relatively safe. However, the current literature is limited. Additional studies with more rigorous outcome reporting are warranted to assess the true safety of re-initiating PPV postoperatively in this population.

Control of working memory maintenance by theta-gamma phase amplitude coupling of human hippocampal neurons.

Retaining information in working memory (WM) is a demanding process that relies on cognitive control to protect memoranda-specific persistent activity from interference. How cognitive control regulates WM storage, however, remains unknown. We hypothesized that interactions of frontal control and hippocampal persistent activity are coordinated by theta-gamma phase amplitude coupling (TG-PAC). We recorded single neurons in the human medial temporal and frontal lobe while patients maintained multiple items in WM. In the hippocampus, TG-PAC was indicative of WM load and quality. We identified cells that selectively spiked during nonlinear interactions of theta phase and gamma amplitude. These PAC neurons were more strongly coordinated with frontal theta activity when cognitive control demand was high, and they introduced information-enhancing and behaviorally relevant noise correlations with persistently active neurons in the hippocampus. We show that TG-PAC integrates cognitive control and WM storage to improve the fidelity of WM representations and facilitate behavior.

Neurons in human pre-supplementary motor area encode key computations for value-based choice.

Adaptive behaviour in real-world environments requires that choices integrate several variables, including the novelty of the options under consideration, their expected value and uncertainty in value estimation. Here, to probe how integration over decision variables occurs during decision-making, we recorded neurons from the human pre-supplementary motor area (preSMA), ventromedial prefrontal cortex and dorsal anterior cingulate. Unlike the other areas, preSMA neurons not only represented separate pre-decision variables for each choice option but also encoded an integrated utility signal for each choice option and, subsequently, the decision itself. Post-decision encoding of variables for the chosen option was more widely distributed and especially prominent in the ventromedial prefrontal cortex. Our findings position the human preSMA as central to the implementation of value-based decisions.

Fluid Restriction Reduces Delayed Hyponatremia and Hospital Readmissions After Transsphenoidal Surgery.

CONTEXT: Postoperative hyponatremia leads to prolonged hospital length of stay and readmission within 30 days. OBJECTIVE: To assess 3 strategies for reducing rates of postoperative hyponatremia and analyze risk factors for hyponatremia. DESIGN: Two retrospective analyses and 1 prospective study. SETTING: Tertiary referral hospital. PATIENTS: Patients undergoing transsphenoidal surgery for pituitary adenomas and other sellar and parasellar pathologies. INTERVENTION(S): Phase 1: no intervention. Phase 2: postoperative day (POD) 7 sodium testing and patient education. Phase 3: fluid restriction to 1 L/day on discharge in addition to phase 2 interventions. MAIN OUTCOME MEASURES: Rates of early and delayed hyponatremia and readmissions. Secondary outcomes were risk factors for hyponatremia and readmission costs. RESULTS: In phase 1, 296 patients underwent transsphenoidal surgery. Twenty percent developed early and 28% delayed hyponatremia. Thirty-eight percent underwent POD 7 sodium testing. Readmission rates were 15% overall and 4.3% for hyponatremia. In phase 2 (n = 316), 22% developed early and 25% delayed hyponatremia. Eighty-nine percent complied with POD 7 sodium testing. Readmissions were unchanged although severity of hyponatremia was reduced by 60%. In phase 3 (n = 110), delayed hyponatremia was reduced 2-fold [12.7%, relative risk (RR) = 0.52] and readmissions 3-fold [4.6%, RR = 0.30 (0.12-0.73)]; readmissions for hyponatremia were markedly reduced. Hyponatremia readmission increased costs by 30%. CONCLUSIONS: Restricting fluid to 1 L/day on discharge decreases rates of delayed hyponatremia and readmissions by 50%. Standardized patient education and POD 7 sodium testing decreases severity of hyponatremia but does not impact readmission rates. These protocols should be considered standard practice for patients undergoing transsphenoidal surgery.

Treatment of Cushing Disease With Pituitary-Targeting Seliciclib.

CONTEXT: Preclinical studies show seliciclib (R-roscovitine) suppresses neoplastic corticotroph proliferation and pituitary adrenocorticotrophic hormone (ACTH) production. OBJECTIVE: To evaluate seliciclib as an effective pituitary-targeting treatment for patients with Cushing disease (CD). METHODS: Two prospective, open-label, phase 2 trials, conducted at a tertiary referral pituitary center, included adult patients with de novo, persistent, or recurrent CD who received oral seliciclib 400 mg twice daily for 4 consecutive days each week for 4 weeks. The primary endpoint in the proof-of-concept single-center study was normalization of 24-hour urinary free cortisol (UFC; ≤ 50 µg/24 hours) at study end; in the pilot multicenter study, primary endpoint was UFC normalization or ≥ 50% reduction in UFC from baseline to study end. RESULTS: Sixteen patients were consented and 9 were treated. Mean UFC decreased by 42%, from 226.4 ± 140.3 µg/24 hours at baseline to 131.3 ± 114.3 µg/24 hours by study end. Longitudinal model showed significant UFC reductions from baseline to each treatment week. Three patients achieved ≥ 50% UFC reduction (range, 55%-75%), and 2 patients exhibited 48% reduction; none achieved UFC normalization. Plasma ACTH decreased by 19% (P = 0.01) in patients who achieved ≥ 48% UFC reduction. Three patients developed grade ≤ 2 elevated liver enzymes, anemia, and/or elevated creatinine, which resolved with dose interruption/reduction. Two patients developed grade 4 liver-related serious adverse events that resolved within 4 weeks of seliciclib discontinuation. CONCLUSION: Seliciclib may directly target pituitary corticotrophs in CD and reverse hypercortisolism. Potential liver toxicity of seliciclib resolves with treatment withdrawal. The lowest effective dose requires further determination.

Surgery as a first-line option for prolactinomas.

INTRODUCTION: Treatment of prolactinomas with dopamine agonists has been the established first-line treatment option for many years, with surgery reserved for refractory cases or medication intolerance. This approach may not be the best option in many cases. AREAS COVERED: Review of the epidemiology, biology, and treatment options available for prolactinomas, including best available data on outcomes, costs, and morbidities for each therapy. These data are then used to propose a 'surgery-first' treatment approach for a subset of prolactinomas as an alternative to primary medical management. EXPERT OPINION: Based on the available data, there is a strong rationale that transsphenoidal surgery should be considered a first-line treatment option for both micro- and macro-prolactinomas that do not demonstrate high grade cavernous sinus invasion on MRI imaging, with dopamine agonists administered as a secondary therapy for tumors not in remission following surgery, and for giant tumors. This 'surgery-first' approach assumes the availability of skilled and experienced pituitary surgeons to ensure optimal outcomes. This approach should result in high cure rates and reduced DA requirements for patients not cured from initial surgery. Further, it will reduce medical costs over a patient's lifetime and the chronic morbidities associated with protracted dopamine agonist usage.

The geometry of domain-general performance monitoring in the human medial frontal cortex.

Controlling behavior to flexibly achieve desired goals depends on the ability to monitor one's own performance. It is unknown how performance monitoring can be both flexible, to support different tasks, and specialized, to perform each task well. We recorded single neurons in the human medial frontal cortex while subjects performed two tasks that involve three types of cognitive conflict. Neurons encoding conflict probability, conflict, and error in one or both tasks were intermixed, forming a representational geometry that simultaneously allowed task specialization and generalization. Neurons encoding conflict retrospectively served to update internal estimates of conflict probability. Population representations of conflict were compositional. These findings reveal how representations of evaluative signals can be both abstract and task-specific and suggest a neuronal mechanism for estimating control demand.