Severe distortion in the representation of foveal visual image locations in short-term memory.

The foveal visual image region provides the human visual system with the highest acuity. However, it is unclear whether such a high fidelity representational advantage is maintained when foveal image locations are committed to short-term memory. Here, we describe a paradoxically large distortion in foveal target location recall by humans. We briefly presented small, but high contrast, points of light at eccentricities ranging from 0.1 to 12°, while subjects maintained their line of sight on a stable target. After a brief memory period, the subjects indicated the remembered target locations via computer controlled cursors. The biggest localization errors, in terms of both directional deviations and amplitude percentage overshoots or undershoots, occurred for the most foveal targets, and such distortions were still present, albeit with qualitatively different patterns, when subjects shifted their gaze to indicate the remembered target locations. Foveal visual images are severely distorted in short-term memory.

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.

Focal Cortical Surface Cooling is a Novel and Safe Method for Intraoperative Functional Brain Mapping.

OBJECTIVE: Electric cortical stimulation (ECS) has been the gold standard for intraoperative functional mapping in neurosurgery, yet it carries the risk of induced seizures. We assess the safety of focal cortical cooling (CC) as a potential alternative to ECS. METHODS: We reviewed 40 patients (13 with tumor and 27 with mesial temporal lobe epilepsy) who underwent intraoperative CC at the University of Iowa Hospital and Clinics (CC group), of whom 38 underwent ECS preceding CC. Intraoperative and postoperative seizure incidence, postoperative neurologic deficits, and new postoperative radiographic findings were collected to assess CC safety. Fifty-five patients who underwent ECS mapping without CC (ECS-alone group) were reviewed as a control cohort. Another 25 patients who underwent anterior temporal lobectomy (ATL) without CC or ECS (no ECS/no CC-ATL group) were also reviewed to evaluate long-term effects of CC. RESULTS: Seventy-nine brain sites in the CC group were cooled, comprising inferior frontal gyrus (44%), precentral gyrus (39%), postcentral gyrus (6%), subcentral gyrus (4%), and superior temporal gyrus (6%). The incidence of intraoperative seizure(s) was 0% (CC group) and 3.6% (ECS-alone group). The incidence of seizure(s) within the first postoperative week did not significantly differ among CC (7.9%), ECS-alone (9.0%), and no ECS/no CC-ATL groups (12%). There was no significant difference in the incidence of postoperative radiographic change between CC (7.5%) and ECS-alone groups (5.5%). Long-term seizure outcome (Engel I+II) for mesial temporal epilepsy did not differ among CC (80%), ECS-alone (83.3%), and no ECS/no CC-ATL groups (83.3%). CONCLUSIONS: CC when used as an intraoperative mapping technique is safe and may complement ECS.

Discrimination of residents during neurosurgical training in Mexico: Results of a survey prior to SARS-CoV-2.

BACKGROUND: Recent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic represents an important negative impact on global training of neurosurgery residents. Even before the pandemic, discrimination is a challenge that neurosurgical residents have consistently faced. In the present study, we evaluated discriminatory conditions experienced by residents during their neurosurgical training in Mexico before the SARS-CoV-2 pandemic. METHODS: An electronic survey of 18 questions was sent among residents registered in the Mexican Society of Neurological Surgery (MSNS), between October 2019 and July 2020. Statistical analysis was made in IBM SPSS Statistics 25. The survey focused on demographic characteristics, discrimination, personal satisfaction, and expectations of residents. RESULTS: A response rate of 50% (132 of 264 residents' members of MSNS) was obtained and considered for analysis. Median age was 30.06 ± 2.48 years, 5.3% (n = 7) were female and 16.7% (n = 22) were foreigners undergoing neurosurgical training in Mexico. Approximately 27% of respondents suffered any form of discrimination, mainly by place of origin (9.1%), by gender (8.3%) or by physical appearance (6.1%). About 42.9% (n = 3) of female residents were discriminated by gender versus 6.4% (n = 8) of male residents (P = 0.001); while foreign residents mentioned having suffered 10 times more an event of discrimination by place of origin compared to native Mexican residents (36.4% vs. 3.6%, P < 0.001). CONCLUSION: This manuscript represents the first approximation to determine the impact of discrimination suffered by residents undergoing neurosurgical training in Mexico before the SARS-CoV-2 pandemic.

99mTc-UBI 29-41 bone SPECT/CT scan in craniofacial Actinomyces israelii: Misdiagnosis of cranial bone tumor - A case report.

BACKGROUND: Actinomycosis is a rare infection, frequently misdiagnosed as a neoplasia. This chronic and granulomatous disease is caused by Actinomyces israelii species. Cervicofacial actinomycosis occurs in 60% of cases and the diagnosis is commonly made by histopathology study. CASE DESCRIPTION: We report a case of fronto-orbital osteomyelitis initially misdiagnosed as a cranial bone meningioma, but later proved to be a case of actinomycosis. 99mTechnetium (99mTc) three-phase bone single-photon emission computed tomography/computed tomography (SPECT/CT) and 99mTc-ubiquicidin (UBI) 29-41 bone SPECT/CT scans were performed to corroborate the control of the infection. CONCLUSION: Craniofacial actinomycosis is the most common presentation of actinomycosis. However, it continues to be a rare and difficult disease to diagnose and is often confused with a neoplastic process. The 99mTc-UBI 29-41 bone SPECT/CT scan could be an auxiliary noninvasive diagnostic alternative and a follow-up method for these patients.

Working memory representation of empty sets in the primate parietal and prefrontal cortices.

For the brain, representing empty sets as a precursor to zero is a challenge because it requires the active coding of a quantitative category that, by definition, contains no items. Recent neurophysiological recordings show that empty sets are distinctively encoded by neurons in the primate ventral intraparietal area (VIP) and the prefrontal cortex (PFC). However, how empty sets are represented in working memory is unknown. We simultaneously recorded from VIP and PFC while rhesus monkeys performed a delayed numerosity matching task that required the maintenance of numerosities in memory for a brief period. Countable numerosities (1-4) and empty sets ('numerosity 0') were included as stimuli. Single neurons in PFC, and to a lesser extent neurons in VIP, actively encoded empty sets during the delay period. In both cortical areas, empty sets were progressively differentiated from countable numerosities with time during the ongoing trial. Moreover, the tuning of neuron populations in VIP and PFC shifted dynamically towards empty sets so that they became increasingly overrepresented in working memory. Compared to VIP, the prefrontal representation of empty sets was more stable in time and more independent of low level visual features. Moreover, PFC activity correlated better with behavioral performance in empty set trials. These findings suggest that the representation of null quantity in working memory relies more on prefrontal and less on parietal processing. Overall, our results show that empty sets are dynamically and distinctly represented in working memory.

Memory-guided microsaccades.

Despite strong evidence to the contrary in the literature, microsaccades are overwhelmingly described as involuntary eye movements. Here we show in both human subjects and monkeys that individual microsaccades of any direction can easily be triggered: (1) on demand, based on an arbitrary instruction, (2) without any special training, (3) without visual guidance by a stimulus, and (4) in a spatially and temporally accurate manner. Subjects voluntarily generated instructed "memory-guided" microsaccades readily, and similarly to how they made normal visually-guided ones. In two monkeys, we also observed midbrain superior colliculus neurons that exhibit movement-related activity bursts exclusively for memory-guided microsaccades, but not for similarly-sized visually-guided movements. Our results demonstrate behavioral and neural evidence for voluntary control over individual microsaccades, supporting recently discovered functional contributions of individual microsaccade generation to visual performance alterations and covert visual selection, as well as observations that microsaccades optimize eye position during high acuity visually-guided behavior.

Neuronal Representation of Numerosity Zero in the Primate Parieto-Frontal Number Network.

Neurons in the primate parieto-frontal network represent the number of visual items in a collection, but it is unknown whether this system encodes empty sets as conveying null quantity. We recorded from the ventral intraparietal area (VIP) and the prefrontal cortex (PFC) of monkeys performing a matching task including empty sets and countable numerosities as stimuli. VIP neurons encoded empty sets predominantly as a distinct category from numerosities. In contrast, PFC neurons represented empty sets more similarly to numerosity one than to larger numerosities, exhibiting numerical distance and size effects. Moreover, prefrontal neurons represented empty sets abstractly and irrespective of stimulus variations. Compared to VIP, the activity of numerosity neurons in PFC correlated better with the behavioral outcome of empty-set trials. Our results suggest a hierarchy in the processing from VIP to PFC, along which empty sets are steadily detached from visual properties and gradually positioned in a numerical continuum. These findings elucidate how the brain transforms the absence of countable items, nothing, into an abstract quantitative category, zero.

Effects of biotin on pyruvate carboxylase, acetyl-CoA carboxylase, propionyl-CoA carboxylase, and markers for glucose and lipid homeostasis in type 2 diabetic patients and nondiabetic subjects.

BACKGROUND: Several studies have shown that biotin affects glucose homeostasis. Serum biotin concentrations are lower in subjects with type 2 diabetes than in control subjects. Lymphocyte propionyl-CoA carboxylase (PCC; EC 6.4.1.3) activity has proved to be a sensitive indicator of biotin status that is more accurate than is serum biotin concentration. OBJECTIVE: We studied the activity of PCC, pyruvate carboxylase (PC; EC 6.4.1.1), and acetyl-CoA carboxylase (ACC; EC 6.4.1.2) in type 2 diabetic and nondiabetic subjects. The effect of biotin administration (6.14 micro mol/d) on the activity of these enzymes and on several plasma metabolites was also studied. DESIGN: We compared the activities of carboxylases in circulating lymphocytes from patients with type 2 diabetes (n = 24) with those in circulating lymphocytes from nondiabetic subjects (n = 30). We also assessed the effect of biotin administration for 14 and 28 d on the activity of these enzymes and on the concentrations of several metabolites (type 2 diabetic patients, n = 10; nondiabetic subjects, n = 7). RESULTS: No significant differences in lymphocyte carboxylase activities were found between the type 2 diabetic patients and the nondiabetic subjects. Biotin administration increased the activity of PCC, PC, and ACC in all the subjects. No significant change in glucose, insulin, triacylglycerol, cholesterol, or lactate concentration was observed with the treatment in either the diabetic or the nondiabetic subjects. CONCLUSIONS: The activity of carboxylases does not differ significantly between type 2 diabetic and nondiabetic subjects. Pharmacologic doses of biotin increase lymphocyte PCC, PC, and ACC activities.

Guías de diagnóstico y tratamiento de la diabetes gestacional. ALAD, 2016 / Guidelines of diagnosis and treatment of gestational diabetes. Alad, 2016

En los últimos años el aumento de la prevalencia de obesidad y diabetes mellitus tipo 2 (DM2), la aparición a edades más tempranas de DM2, así como el desplazamiento del embarazo a edades mayores conllevan a un aumento de casos de diabetes (DM) en el embarazo. En algunas pacientes la diabetes no se diagnostica y obviamente no se trata. Este hecho puede complicar un embarazo, especialmente en el período embriogénico. La aplicación de nuevos criterios de diagnóstico para la diabetes gestacional, la controversia en el uso y la seguridad de los antidiabéticos orales durante el embarazo, así como el uso de determinados análogos de insulina hacen indispensable que Latinoamérica, a través del Grupo de Trabajo de Diabetes y Embarazo de la Asociación Latinoamericana de Diabetes (ALAD), actualice sus recomendaciones. El desarrollo de las mismas se realizó en varias reuniones y trabajo conjunto del grupo. Se tuvo en cuenta el grado de nivel de evidencia, la experiencia de los referentes y la adaptación cultural según las regiones donde se implementarán las recomendaciones descriptas