Augmented Reality in Breast Surgery Education.

Introduction: Augmented reality (AR) has demonstrated a potentially wide range of benefits and educational applications in the virtual health ecosystem. The concept of real-time data acquisition, machine learning-aided processing, and visualization is a foreseen ambition to leverage AR applications in the healthcare sector. This breakthrough with immersive technologies like AR, mixed reality, virtual reality, or extended reality will hopefully initiate a new surgical era: that of the use of the so-called surgical metaverse. Methods: This paper focuses on the future use of AR in breast surgery education describing two potential applications (surgical remote telementoring and impalpable breast cancer localization using AR), along with the technical needs to make it possible. Conclusion: Surgical telementoring and impalpable tumors noninvasive localization are two examples that can have success in the future provided the improvements in both data transformation and infrastructures are capable to overcome the current challenges and limitations.

View cells in the hippocampus and prefrontal cortex of macaques during virtual navigation.

Cells selectively activated by a particular view of an environment have been found in the primate hippocampus (HPC). Whether view cells are present in other brain areas, and how view selectivity interacts with other variables such as object features and place remain unclear. Here, we explore these issues by recording the responses of neurons in the HPC and the lateral prefrontal cortex (LPFC) of rhesus macaques performing a task in which they learn new context-object associations while navigating a virtual environment using a joystick. We measured neuronal responses at different locations in a virtual maze where animals freely directed gaze to different regions of the visual scenes. We show that specific views containing task relevant objects selectively activated a proportion of HPC units, and an even higher proportion of LPFC units. Place selectivity was scarce and generally dependent on view. Many view cells were not affected by changing the object color or the context cue, two task relevant features. However, a small proportion of view cells showed selectivity for these two features. Our results show that during navigation in a virtual environment with complex and dynamic visual stimuli, view cells are found in both the HPC and the LPFC. View cells may have developed as a multiarea specialization in diurnal primates to encode the complexities and layouts of the environment through gaze exploration which ultimately enables building cognitive maps of space that guide navigation.

Stable Working Memory and Perceptual Representations in Macaque Lateral Prefrontal Cortex during Naturalistic Vision.

Primates use perceptual and mnemonic visuospatial representations to perform everyday functions. Neurons in the lateral prefrontal cortex (LPFC) have been shown to encode both of these representations during tasks where eye movements are strictly controlled and visual stimuli are reduced in complexity. This raises the question of whether perceptual and mnemonic representations encoded by LPFC neurons remain robust during naturalistic vision-in the presence of a rich visual scenery and during eye movements. Here we investigate this issue by training macaque monkeys to perform working memory and perception tasks in a visually complex virtual environment that requires navigation using a joystick and allows for free visual exploration of the scene. We recorded the activity of 3950 neurons in the LPFC (areas 8a and 9/46) of two male rhesus macaques using multielectrode arrays, and measured eye movements using video tracking. We found that navigation trajectories to target locations and eye movement behavior differed between the perception and working memory tasks, suggesting that animals used different behavioral strategies. Single neurons were tuned to target location during cue encoding and working memory delay, and neural ensemble activity was predictive of the behavior of the animals. Neural decoding of the target location was stable throughout the working memory delay epoch. However, neural representations of similar target locations differed between the working memory and perception tasks. These findings indicate that during naturalistic vision, LPFC neurons maintain robust and distinct neural codes for mnemonic and perceptual visuospatial representations.SIGNIFICANCE STATEMENT We show that lateral prefrontal cortex neurons encode working memory and perceptual representations during a naturalistic task set in a virtual environment. We show that despite eye movement and complex visual input, neurons maintain robust working memory representations of space, which are distinct from neuronal representations for perception. We further provide novel insight into the use of virtual environments to construct behavioral tasks for electrophysiological experiments.

Distinct neural codes in primate hippocampus and lateral prefrontal cortex during associative learning in virtual environments.

The hippocampus (HPC) and the lateral prefrontal cortex (LPFC) are two cortical areas of the primate brain deemed essential to cognition. Here, we hypothesized that the codes mediating neuronal communication in the HPC and LPFC microcircuits have distinctively evolved to serve plasticity and memory function at different spatiotemporal scales. We used a virtual reality task in which animals selected one of the two targets in the arms of the maze, according to a learned context-color rule. Our results show that during associative learning, HPC principal cells concentrate spikes in bursts, enabling temporal summation and fast synaptic plasticity in small populations of neurons and ultimately facilitating rapid encoding of associative memories. On the other hand, layer II/III LPFC pyramidal cells fire spikes more sparsely distributed over time. The latter would facilitate broadcasting of signals loaded in short-term memory across neuronal populations without necessarily triggering fast synaptic plasticity.

Ketamine disrupts naturalistic coding of working memory in primate lateral prefrontal cortex networks.

Ketamine is a dissociative anesthetic drug, which has more recently emerged as a rapid-acting antidepressant. When acutely administered at subanesthetic doses, ketamine causes cognitive deficits like those observed in patients with schizophrenia, including impaired working memory. Although these effects have been linked to ketamine's action as an N-methyl-D-aspartate receptor antagonist, it is unclear how synaptic alterations translate into changes in brain microcircuit function that ultimately influence cognition. Here, we administered ketamine to rhesus monkeys during a spatial working memory task set in a naturalistic virtual environment. Ketamine induced transient working memory deficits while sparing perceptual and motor skills. Working memory deficits were accompanied by decreased responses of fast spiking inhibitory interneurons and increased responses of broad spiking excitatory neurons in the lateral prefrontal cortex. This translated into a decrease in neuronal tuning and information encoded by neuronal populations about remembered locations. Our results demonstrate that ketamine differentially affects neuronal types in the neocortex; thus, it perturbs the excitation inhibition balance within prefrontal microcircuits and ultimately leads to selective working memory deficits.

Diagnosis and locoregional treatment of patients with breast cancer during the COVID-19 pandemic / Diagnostico y tratamiento locorregional de las pacientes con cancer de mama durante la pandemia de la COVID-19

We are facing a pandemic that is going to affect a significant part of the population. At the end of April in the world there are about 3,000,000 cases, with 205,000 deaths and 860,000 patients recovered. The response to this pandemic has in many cases led to a significant change in the daily work of caring for cancer patients, the good results of which depend largely on time-adjusted protocols and multidisciplinary treatments. We present a review of local, surgical and radiotherapy treatment together with authors' recommendations made from personal experience on ways to act in the diagnosis and surgical treatment of breast cancer during the COVID-19 pandemic. The multidisciplinary Breast Committees must continue to meet weekly in videoconference format. All surgical actions and irradiations must be carried out with maximum safety for both the patients and the participating teams. Hypofractionation in radiation therapy should be the standard treatment. Sometimes it is recommended to apply a primary systemic treatment or even a primary irradiation. Great coordination between the surgical and oncology teams, both medical and radiotherapeutic, is essential

Nos enfrentamos a una pandemia que afecta a una parte importante de la población.  A finales de abril de 2020, en el mundo hay cerca de 3.000.000 de casos, con 205.000 muertes y 860.000 pacientes recuperados. La respuesta a esta pandemia en muchos casos ha supuesto modificaciones importantes en el cuidado diario de las pacientes con cáncer, dependiendo el buen resultado en buena parte del ajuste de los protocolos a las circunstancias especiales y a los tratamientos multidisciplinarios. Presentamos una revisión del tratamiento quirúrgico y radioterapia junto con las recomendaciones de los autores basadas en su experiencia personal a la hora del diagnóstico y tratamiento locorregional del cáncer de mama durante la pandemia del COVID-19. Los comités multidisciplinarios deben seguir reuniéndose semanalmente en formato de videoconferencia. Todos las intervenciones quirúrgicas e irradiaciones deben ser llevadas a cabo con la máxima seguridad tanto para las pacientes como para el personal sanitario que participa. El hipofraccionamiento debe ser el tratamiento radioterápico estándar. En algunos casos se utilizará tratamiento sistémico primario o incluso radioterapa preoperatoria. Es esencial una coordinación importante entre los equipos quirúrgicos y los oncológicos, tanto radioterápicos como médicos

Customizable cap implants for neurophysiological experimentation.

BACKGROUND: Several primate neurophysiology laboratories have adopted acrylic-free, custom-fit cranial implants. These implants are often comprised of titanium or plastic polymers, such as polyether ether ketone (PEEK). Titanium is favored for its mechanical strength and osseointegrative properties whereas PEEK is notable for its lightweight, machinability, and MRI compatibility. Recent titanium/PEEK implants have proven to be effective in minimizing infection and implant failure, thereby prolonging experiments and optimizing the scientific contribution of a single primate. NEW METHOD: We created novel, customizable PEEK 'cap' implants that contour to the primate's skull. The implants were created using MRI and/or CT data, SolidWorks software and CNC-machining. RESULTS: Three rhesus macaques were implanted with a PEEK cap implant. Head fixation and chronic recordings were successfully performed. Improvements in design and surgical technique solved issues of granulation tissue formation and headpost screw breakage. COMPARISON WITH EXISTING METHODS: Primate cranial implants have traditionally been fastened to the skull using acrylic and anchor screws. This technique is prone to skin recession, infection, and implant failure. More recent methods have used imaging data to create custom-fit titanium/PEEK implants with radially extending feet or vertical columns. Compared to our design, these implants are more surgically invasive over time, have less force distribution, and/or do not optimize the utilizable surface area of the skull. CONCLUSIONS: Our PEEK cap implants served as an effective and affordable means to perform electrophysiological experimentation while reducing surgical invasiveness, providing increased strength, and optimizing useful surface area.

Resultados y complicaciones quirúrgicas de la aplicación de la cinta transobturadora / Outcomes and surgical complications in the application of transobturator tape

Resumen OBJETIVO Evaluar el éxito subjetivo y analizar las complicaciones de la aplicación de la cinta transobturadora en el tratamiento de pacientes con incontinencia urinaria de esfuerzo. MATERIALES Y MÉTODOS Estudio de cohorte simple, retrospectivo, al que se incluyeron pacientes a quienes entre los años 2008-2016 se les colocó una cinta transobturadora. Se consideró éxito subjetivo cuando la paciente negó la pérdida de orina por interrogatorio; se registraron las complicaciones intra y posoperatorias. Se realizó estadística descriptiva (SPSS 24.0.), χ2 para variables cualitativas y t de Student para cuantitativas; para determinar los factores de riesgo se obtuvieron la razón de momios y el IC95%. RESULTADOS Se incluyeron 292 pacientes con edad promedio de 51 ± 10 años, 48.6% (n = 141) con diagnóstico de incontinencia urinaria de esfuerzo, 47.2% (n = 139) con incontinencia urinaria mixta, 3.4% (n = 10) con alto riesgo de incontinencia urinaria de novo posterior a la cirugía de prolapso pélvico, 0.68% (n = 2) con incontinencia urinaria oculta. A 214 (73.2%) pacientes se les realizó cirugía concomitante por prolapso de órganos pélvicos. La tasa de curación subjetiva de incontinencia urinaria de esfuerzo fue de 95%; las complicaciones transquirúrgicas fueron: lesión vesical (n = 3) y lesión uretral (n = 1) e inmediatas: retención urinaria 11.3% (n = 33). Las pacientes con falla quirúrgica eran de mayor edad y paridad que las que tuvieron éxito subjetivo (4 ± 2.4 vs 2.72 ± 1.9, p = 0.045 y 56.44 ± 11.6 vs 51.29 ± 9.8, p = 0.007, respectivamente). CONCLUSIONES En el tratamiento de la incontinencia urinaria de esfuerzo la colocación de una cinta transobturadora tiene altas tasas de curación subjetiva y bajos índices de complicaciones. La edad y la paridad son factores asociados con la falla del tratamiento quirúrgico.

Abstract OBJECTIVE To evaluate the subjective success and analyze the complications of transobturator tape application in the treatment of stress urinary incontinence. MATERIAL AND METHODS Retrospective single cohort study. Patients who were placed to transobturator tape application from 2008-2016 were included. Subjective success of Stress Urinary Incontinence was defined when the patient denied urine loss by questioning, intra and postoperative complications were recorded. With the SPSS 24.0 program was done descriptive statistics, χ2 for qualitative variables and t student for quantitative. Odds Ratio and Confidence Intervals of 95% (95% CI) to determine the risk factors. RESULTS 292 patients, average age of 51 ± 10 years, 48.6% (n = 141) with a diagnosis of SUI, 47.2% (n = 139) mixed urinary incontinence, 3.4% (n = 10) with high risk of de novo urinary incontinence after pelvic prolapse surgery, 0.68% (n = 2) with occult urinary incontinence. To 214 (73.2%) concomitant surgery for pelvic organ prolapse was performed. The subjective cure rate of stress urinary incontinence was 95%, the trans-surgical complications: bladder injury (n = 3) and urethral injury (n = 1) and immediate complications: urinary retention in 11.3% (n = 33). Patients with surgical failure was increased age and parity than patients with subjective success (4 ± 2.4 vs 2.72 ± 1.9, p = 0.045 and 56.44 ± 11.6 vs 51.29 ± 9.8, p = 0.007, respectively). CONCLUSIONS Transobturator tape application placement has high subjective cure rates for the treatment of stress urinary incontinence and low complication rates.

Cáncer y embarazo, experiencia del Instituto Nacional de Perinatología / Cancer during pregnancy: experience in Perinatology National Institute

Resumen Objetivo: Describir el esquema de tratamiento indicado a pacientes con cáncer y embarazo y las repercusiones perinatales. Materiales y métodos: Estudio retrospectivo, longitudinal, observacional y descriptivo de una cohorte simple de pacientes con diagnóstico de cáncer (corroborado por estudio histopatológico) y embarazo atendidas en el Instituto Nacional de Perinatología entre los meses de enero de 2009 a diciembre de 2014. Los datos se analizaron con el programa SPSS versión 20.0 con medidas de tendencia central, frecuencias, proporciones y desviación estándar. Resultados: Se incluyeron 47 pacientes con media de edad de 28.1 ± 7.3 años, el diagnóstico de cáncer se estableció en 46 pacientes, en promedio, a las 19.4 ± 8.5 semanas y en un caso en el puerperio tardío. Los cánceres más frecuentes fueron: 28% leucemia (n = 13), 26% mama (n = 12), 17% cuello uterino (n = 8) y 15% ovario (n = 7). Durante el embarazo 55% de las pacientes recibieron quimioterapia (n = 27) y 28% tratamiento quirúrgico (n = 13). Se obtuvieron 42 nacidos vivos (91%) de que: 53% fueron a término (n = 25), 22% pretérmino tardío (n = 10), 9% pretérmino moderado (n = 4) y 6% pretérmino extremo (n = 3). Se registraron 2 nacimientos inmaduros (4%), 3 abortos espontáneos (6%) y 3 muertes maternas indirectas (6%). Conclusiones: La cirugía y la quimioterapia durante el segundo trimestre del embarazo son seguras para la madre y el feto.

Abstract Objective: To describe the management and perinatal outcomes in patients with cancer and pregnancy. Materials and method: Retrospective, longitudinal, observational and descriptive study of a simple cohort of women with a diagnosis of Cancer (corroborated by histopathological study) and pregnancy from January 2009 to December 2014. The data was analyzed with the SPSS program version 20.0 with central tendency measures, frequencies, proportions and standard deviation. Results: We included 47 patients with an average age of 28.1 ± 7.3 years, the diagnosis of cancer was made in 46 patients on average at 19.4 ± 8.5 weeks and in a case in the late puerperium. The most frequent cancers were: 28% leukemia (n = 13), 26% breast (n = 12), 17% cervical (n = 8) and 15% ovarian (n = 7). During pregnancy 55% patients received chemotherapy (n = 27) and 28% surgical treatment (n = 13). We obtained 42 live births (91%) of which: 53% were full term (n = 25), 22% late preterm (n = 10), 9% moderate preterm (n=4) and 6% extreme preterm (n = 3). There were 2 immature births (4%), 3 miscarriages (6%) and 3 indirect maternal deaths (6%). Conclusions: Surgery and chemotherapy during the second trimester of pregnancy are safe for the mother and the fetus.

Task-driven intra- and interarea communications in primate cerebral cortex.

Neural correlations during a cognitive task are central to study brain information processing and computation. However, they have been poorly analyzed due to the difficulty of recording simultaneous single neurons during task performance. In the present work, we quantified neural directional correlations using spike trains that were simultaneously recorded in sensory, premotor, and motor cortical areas of two monkeys during a somatosensory discrimination task. Upon modeling spike trains as binary time series, we used a nonparametric Bayesian method to estimate pairwise directional correlations between many pairs of neurons throughout different stages of the task, namely, perception, working memory, decision making, and motor report. We find that solving the task involves feedforward and feedback correlation paths linking sensory and motor areas during certain task intervals. Specifically, information is communicated by task-driven neural correlations that are significantly delayed across secondary somatosensory cortex, premotor, and motor areas when decision making takes place. Crucially, when sensory comparison is no longer requested for task performance, a major proportion of directional correlations consistently vanish across all cortical areas.

[Vaginal impingement of uterine arteries (Zea technique) prior to cervical curettage in cervical ectopic pregnancy: three case report and literature review]. / Pinzamiento de arterias uterinas por vía vaginal previo a legrado cervical en embarazo ectópico cervical: reporte de tres casos y revisión bibliogrifica.

Cervical ectopic pregnancy is a rare and danger clinical presentation because it has high risk of massive bleeding. The incidence is reported in 1:2500 pregnancies and has high relation with a history of cervical dilatation and curettage and assisted reproductive techniques. Advances in ultrasound resolution and use of beta fraction of human chorionic gonadotropin allow early diagnosis and provide conservative treatment with decreased morbidity, mortality and fertility preservation. Various techniques have been reported associated with cervical curettage, to reduce bleeding at the implantation site. In this report three cases of cervical ectopic pregnancy managed with cervical curettage, prior vaginal impingement of uterine arteries (Zea Technique) at the Instituto Nacional de Perinatología Isidro Espinosa de los Reyes are described. The Zea technique represents an effective option in the control of obstetric hemorrhage, including patients diagnosed with cervical ectopic pregnancy in who the bleeding volume decrease after its placement. The Zea Technique is easy to apply and preserves fertility. The success of combining this technique with endocervical curettage for the management of cervical ectopic pregnancy is demonstrated. Training for performing this technique does not require highly specialized or highly complex resources since the required material is the usual every area of obstetric care.

[Obstetric management in patients with severe pulmonary hypertension]. / Algoritmo para la atención de pacientes con hipertensión arterial pulmonar severa durante el embarazo.

BACKGROUND: Pulmonary hypertension is a disease of poor prognosis when is associated with pregnancy. A maternal mortality of 30-56% and a neonatal survival of approximately 85% is reported. Surveillance of patients with severe pulmonary hypertension during pregnancy must be multidisciplinary, to provide information and optimal treatment during and after gestation. Targeted therapy for pulmonary arterial hypertension during pregnancy significantly reduces mortality. The critical period with respect to mortality, is the first month after birth. OBJECTIVE: Propose an algorithm for management during pregnancy for patients with severe pulmonary hypertension who want to continue with it. CONCLUSIONS: The recommendations established with clinical evidence for patients with severe pulmonary hypertension and pregnancy are presented: diagnosis, treatment, obstetrics and cardiology management, preoperative recommendations for termination of pregnancy, post-partum care and contraception. The maternal mortality remains significantly higher in patients with severe pulmonary hypertension and pregnancy, in these cases should be performed multidisciplinary management in hospitals that have experience in the management of this disease and its complications.

Amyloid beta: multiple mechanisms of toxicity and only some protective effects?

Amyloid beta (Aß) is a peptide of 39-43 amino acids found in large amounts and forming deposits in the brain tissue of patients with Alzheimer's disease (AD). For this reason, it has been implicated in the pathophysiology of damage observed in this type of dementia. However, the role of Aß in the pathophysiology of AD is not yet precisely understood. Aß has been experimentally shown to have a wide range of toxic mechanisms in vivo and in vitro, such as excitotoxicity, mitochondrial alterations, synaptic dysfunction, altered calcium homeostasis, oxidative stress, and so forth. In contrast, Aß has also shown some interesting neuroprotective and physiological properties under certain experimental conditions, suggesting that both physiological and pathological roles of Aß may depend on several factors. In this paper, we reviewed both toxic and protective mechanisms of Aß to further explore what their potential roles could be in the pathophysiology of AD. The complete understanding of such apparently opposed effects will also be an important guide for the therapeutic efforts coming in the future.

Coding perceptual discrimination in the somatosensory thalamus.

The sensory thalamus is classically viewed as a relay station of sensory information to cortex, but recent studies suggest that it is sensitive to cognitive demands. There are, however, few experiments designed to test whether this is so. We addressed this problem by analyzing the responses of single neurons recorded in the somatosensory thalamus while trained monkeys reported a decision based on the comparison of two mechanical vibration frequencies applied sequentially to one fingertip. In this task, monkeys must hold the first stimulus frequency (f1) in working memory and compare it to the current sensory stimulus (f2) and must postpone the decision report until a cue triggers the decision motor report, i.e., whether f2 > f1 or f2 < f1. We found that thalamic somatosensory neurons encoded the stimulus frequency either in their periodicity and firing-rate responses, but only during the stimulus periods and not during the working memory and decision components of this task. Furthermore, correlation analysis between behavior and stimulus coding showed that only the firing rate modulations accounted for the overall psychophysical performance. However, these responses did not predict the animal's decision reports on individual trials. Moreover, the sensitivity to changes in stimulus frequency was similar when the monkeys performed the vibrotactile discrimination task and when they were not required to report discrimination. These results suggest that the somatosensory thalamus behaves as a relay station of sensory information to the cortex and that it is insensitive to the cognitive demands of the task used here.

Dynamics of cortical neuronal ensembles transit from decision making to storage for later report.

Decisions based on sensory evaluation during single trials may depend on the collective activity of neurons distributed across brain circuits. Previous studies have deepened our understanding of how the activity of individual neurons relates to the formation of a decision and its storage for later report. However, little is known about how decision-making and decision maintenance processes evolve in single trials. We addressed this problem by studying the activity of simultaneously recorded neurons from different somatosensory and frontal lobe cortices of monkeys performing a vibrotactile discrimination task. We used the hidden Markov model to describe the spatiotemporal pattern of activity in single trials as a sequence of firing rate states. We show that the animal's decision was reliably maintained in frontal lobe activity through a selective state sequence, initiated by an abrupt state transition, during which many neurons changed their activity in a concomitant way, and for which both latency and variability depended on task difficulty. Indeed, transitions were more delayed and more variable for difficult trials compared with easy trials. In contrast, state sequences in somatosensory cortices were weakly decision related, had less variable transitions, and were not affected by the difficulty of the task. In summary, our results suggest that the decision process and its subsequent maintenance are dynamically linked by a cascade of transient events in frontal lobe cortices.

α-Oscillations in the monkey sensorimotor network influence discrimination performance by rhythmical inhibition of neuronal spiking.

Extensive work in humans using magneto- and electroencephalography strongly suggests that decreased oscillatory α-activity (8-14 Hz) facilitates processing in a given region, whereas increased α-activity serves to actively suppress irrelevant or interfering processing. However, little work has been done to understand how α-activity is linked to neuronal firing. Here, we simultaneously recorded local field potentials and spikes from somatosensory, premotor, and motor regions while a trained monkey performed a vibrotactile discrimination task. In the local field potentials we observed strong activity in the α-band, which decreased in the sensorimotor regions during the discrimination task. This α-power decrease predicted better discrimination performance. Furthermore, the α-oscillations demonstrated a rhythmic relation with the spiking, such that firing was highest at the trough of the α-cycle. Firing rates increased with a decrease in α-power. These findings suggest that α-oscillations exercise a strong inhibitory influence on both spike timing and firing rate. Thus, the pulsed inhibition by α-oscillations plays an important functional role in the extended sensorimotor system.

Beta oscillations in the monkey sensorimotor network reflect somatosensory decision making.

The neuronal correlate of perceptual decision making has been extensively studied in the monkey somatosensory system by using a vibrotactile discrimination task, showing that stimulus encoding, retention, and comparison are widely distributed across cortical areas. However, from a network perspective, it is not known what role oscillations play in this task. We recorded local field potentials (LFPs) from diverse cortical areas of the sensorimotor system while one monkey performed the vibrotactile discrimination task. Exclusively during stimulus presentation, a periodic response reflecting the stimulus frequency was observed in the somatosensory regions, suggesting that after initial processing, the frequency content of the stimulus is coded in some other way than entrainment. Interestingly, we found that oscillatory activity in the beta band reflected the dynamics of decision making in the monkey sensorimotor network. During the comparison and decision period, beta activity showed a categorical response that reflected the decision of the monkey and distinguished correct from incorrect responses. Importantly, this differential activity was absent in a control condition that involved the same stimulation and response but no decision making required, suggesting it does not merely reflect the maintenance of a motor plan. We conclude that beta band oscillations reflect the temporal and spatial dynamics of the accumulation and processing of evidence in the sensorimotor network leading to the decision outcome.

Do sensory cortices process more than one sensory modality during perceptual judgments?

Recent studies have reported that sensory cortices process more than one sensory modality, challenging the long-lasting concept that they process only one. However, both the identity of these multimodal responses and whether they contribute to perceptual judgments is unclear. We recorded from single neurons in somatosensory cortices and primary auditory cortex while trained monkeys discriminated, on interleaved trials, either between two tactile flutter stimuli or between two acoustic flutter stimuli, and during discrimination sets that combined these two sensory modalities. We found neurons in these sensory cortices that responded to stimuli that are not of their principal sensory modality during these tasks. However, the identity of the stimulus could only be decoded from responses to their principal sensory modality during the stimulation periods and not during the processing steps that link sensation and decision making. These results suggest that multimodal encoding and perceptual judgments in these tasks occur outside the sensory cortices studied here.

Decoding a perceptual decision process across cortex.

Perceptual decisions arise from the activity of neurons distributed across brain circuits. But, decoding the mechanisms behind this cognitive operation across brain circuits has long posed a difficult problem. We recorded the neuronal activity of diverse cortical areas, while monkeys performed a vibrotactile discrimination task. We find that the encoding of the stimuli during the stimulus periods, working memory, and comparison periods is widely distributed across cortical areas. Notably, during the comparison and postponed decision report periods the activity of frontal brain circuits encode both the result of the sensory evaluation that corresponds to the monkey's possible choices and past information on which the decision is based. These results suggest that frontal lobe circuits are more engaged in the readout of sensory information from working memory, when it is required to be compared with other sensory inputs, than simply engaged in motor responses during this task.

Procedure for recording the simultaneous activity of single neurons distributed across cortical areas during sensory discrimination.

We report a procedure for recording the simultaneous activity of single neurons distributed across five cortical areas in behaving monkeys. The procedure consists of a commercially available microdrive adapted to a commercially available neural data collection system. The critical advantage of this procedure is that, in each cortical area, a configuration of seven microelectrodes spaced 250-500 mum can be inserted transdurally and each can be moved independently in the z axis. For each microelectrode, the data collection system can record the activity of up to five neurons together with the local field potential (LFP). With this procedure, we normally monitor the simultaneous activity of 70-100 neurons while trained monkeys discriminate the difference in frequency between two vibrotactile stimuli. Approximately 20-60 of these neurons have response properties previously reported in this task. The neuronal recordings show good signal-to-noise ratio, are remarkably stable along a 1-day session, and allow testing several protocols. Microelectrodes are removed from the brain after a 1-day recording session, but are reinserted again the next day by using the same or different x-y microelectrode array configurations. The fact that microelectrodes can be moved in the z axis during the recording session and that the x-y configuration can be changed from day to day maximizes the probability of studying simultaneous interactions, both local and across distant cortical areas, between neurons associated with the different components of this task.