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.The problem of neural communication in the brain has been little explored traditionally due to the need for simultaneous recordings (1). The arrival of new techniques to record both neural population activity and single-neuron action potentials offers new prospects to study this problem (2, 3). Recently, population recordings have motivated a large number of works on multiunit interactions, including the study of interactions between local field potentials (LFPs) (4–6), LFPs and multiunit activity (5), and LFPs and neuronal spikes (7), but less attention has been paid to interactions between single-unit recordings (8). However, the analysis of simultaneous spike trains becomes critical because it is generally assumed that neurons are key units in distributing information across brain areas (9).An ideal paradigm to study neural communication is the somatosensory discrimination task designed by Romo and coworkers (10). In this task, a trained monkey discriminates the difference in frequency between two mechanical vibrations delivered sequentially to one fingertip (Fig. 1A). Essentially, the monkey must hold the first stimulus frequency (f1) in working memory, must compare the second stimulus frequency (f2) with the memory trace of f1 to form a decision of whether f2 > f1 or f2 < f1, and must postpone the decision until a sensory cue triggers the motor report (11). At the end of every trial, the monkey is rewarded with a drop of liquid for correct discriminations. Previous work on this task has analyzed how single-neuron responses across sensory and motor areas linearly correlate with stimuli and the decision report during the key stages of the task (12). The results show that stimuli are mostly encoded in somatosensory areas, the processes of working memory; that comparison takes place in the secondary somatosensory cortex (S2) and premotor areas; and that behavioral information is primarily found in premotor and motor areas. Thus, the somatosensory discrimination task activates complex processes that are required to communicate information from the areas that encode the stimuli to the areas that integrate them and report the decision.Open in a separate windowFig. 1.Somatosensory discrimination task and cortical recording sites. (A) Sequence of events during the discrimination and passive stimulation tasks (f1, first stimulus; f2, second stimulus; kd, key down; ku, key up; pb, pushbutton; pd, probe down; pu, probe up) (Materials and Methods). (B) Top view of the monkey brain and the recorded cortical areas (green spots).In the present work, we study this communication paradigm through the analysis of simultaneous recordings of neurons engaged in the task (6, 13) from two monkeys. Indeed, by applying nonlinear statistical methods, we estimate modulated cortical correlations that help describe how task-related information flows from sensory to motor areas when a correct decision is made.     

"Above the influence": how college students communicate about the healthy deviance of alcohol abstinence

Consumption of alcohol is widespread in U.S. culture, particularly among college students. Using a communication privacy management framework ( Petronio, 2002 ), this study examined how college students who abstain from alcohol negotiate communication of their nondrinking status and establish meaning in a culture in which drinking is the norm. Through 25 face-to-face interviews, this article explores the experiences of "healthy deviants"-individuals who engage in healthy behavior that violates traditional norms. Interviews identified that participants relied on privacy rules when determining whether and how to disclose their nondrinking status. If participants perceived more costs from the disclosure than rewards, they did not disclose. Participants enacted specific strategies to manage (non)disclosure of their abstinence from alcohol, providing practical ways for people who engage in healthy deviance to avoid or manage stigma.     

Geographic distribution of hantaviruses associated with neotomine and sigmodontine rodents, Mexico

To increase our knowledge of the geographic distribution of hantaviruses associated with neotomine or sigmodontine rodents in Mexico, we tested 876 cricetid rodents captured in 18 Mexican states (representing at least 44 species in the subfamily Neotominae and 10 species in the subfamily Sigmodontinae) for anti-hantavirus IgG. We found antibodies against hantavirus in 35 (4.0%) rodents. Nucleotide sequence data from 5 antibody-positive rodents indicated that Sin Nombre virus (the major cause of hantavirus pulmonary syndrome [HPS] in the United States) is enzootic in the Mexican states of Nuevo León, San Luis Potosí, Tamaulipas, and Veracruz. However, HPS has not been reported from these states, which suggests that in northeastern Mexico, HPS has been confused with other rapidly progressive, life-threatening respiratory diseases. Analyses of nucleotide sequence data from 19 other antibody-positive rodents indicated that El Moro Canyon virus and Limestone Canyon virus are geographically widely distributed in Mexico.     

The spectrum of clinical and pathological manifestations of AIDS in a consecutive series of autopsied patients in Mexico.

OBJECTIVE: Little is known about the clinical profile of AIDS in Latin American populations. This study characterizes the clinical and pathological manifestations of AIDS in a representative series of Mexican AIDS patients at autopsy. DESIGN: The clinical and pathological findings were abstracted retrospectively for a sequential series of autopsied AIDS patients. SETTING: Autopsies were conducted at the four major tertiary level hospitals that serve the majority of AIDS patients in Mexico City. PATIENTS: Subjects included 177 consecutive patients diagnosed with AIDS between March 1984 and January 1989 who subsequently died and were autopsied in the same period in the study hospitals. MAIN OUTCOME MEASURES: Demographic characteristics, including age, gender, residence, socioeconomic status, and risk group; clinical presentation and autopsy findings, including opportunistic infections and malignancies. RESULTS: Sixty per cent of the AIDS patients presented with wasting syndrome. The most common infections were cytomegalovirus (69%), tuberculosis (25%), and Pneumocystis carinii pneumonia (24%). Central nervous system infections were also common and included toxoplasmosis (19%) and cryptococcoses (10%). Kaposi's sarcoma was present in 30% of cases and non-Hodgkin's lymphoma in 9%. CONCLUSION: Clinical manifestation, and types and frequency of opportunistic infections in our Mexican AIDS patients were more similar to those seen in AIDS patients in Africa and Haiti than in the United States and Europe. These findings suggest that the AIDS epidemic in Mexico has an 'intermediate' pattern and may be a prototype for Latin American countries.     

Five-year survival of 728 patients after myocardial infarction. A community study.

This study deals with the five-year survival of 728 myocardial infarction patients who survived the first 28 days after the onset of symptoms. The series was collected by the Helsinki Coronary Register and includes all cases of acute myocardial infarction in the population who were under 66 years of age during the period 1 July 1970 to 30 June 1971. Of the 219 patients who subsequently died, 81.8 per cent died from ischaemic heart disease. The mortality was highest during the first year after the acute phase but did not decrease after the second year. The mortality was higher in patients with a transmural infarction (five-year mortality 34.0%) compared with those with a nontransmural infarction (19.7%). The mortality also was higher for recurrent acute myocardial infractions than for first attacks. The five-year mortality for women was less (20.5%, age-adjusted) than for men (31.6%). This is mainly because of the higher incidence of nontransmural infarcts in women. Acute ischaemic heart disease is more common, more often fatal, and has a poorer long-term prognosis in men than in women in Helsinki. The acute mortality from acute ischaemic heart disease is high in Helsinki when compared with other WHO registers and, in addition, the long-term prognosis seems to be relatively poor in Helsinki.     

Assessment at 6 months may be warranted for patients with chronic myeloid leukemia with no major cytogenetic response at 3 months

Response to tyrosine kinase inhibitors at three months is a predictor for long-term outcome in chronic myeloid leukemia patients treated with tyrosine kinase inhibitors. We analyzed 456 newly diagnosed chronic myeloid leukemia patients treated with tyrosine kinase inhibitors to determine their outcome based on their response at six months. Forty-four (10%) patients did not achieve major cytogenetic response at three months: 18 of 67 (27%) patients treated with imatinib 400; 18 of 196 (9%) with imatinib 800; and 8 of 193 (4%) with 2nd generation tyrosine kinase inhibitors. Among them, 19 (43%) achieved major cytogenetic response at six months and subsequently had an overall outcome similar to the patients who achieved a major cytogenetic response at three months. In conclusion, the response to tyrosine kinase inhibitors at three months is a static, one-time measure. Assessing the response at six months of patients with poor response at three months may provide a better predictor for long-term outcome.     

Structural and Luminescence Properties of Lu2O3:Eu3+ F127 Tri-Block Copolymer Modified Thin Films Prepared by Sol-Gel Method

Lu₂O₃:Eu³⁺ transparent, high density, and optical quality thin films were prepared using the sol-gel dip-coating technique, starting with lutetium and europium nitrates as precursors and followed by hydrolysis in an ethanol-ethylene glycol solution. Acetic acid and acetylacetonate were incorporated in order to adjust pH and as a sol stabilizer. In order to increment the thickness of the films and orient the structure, F127 Pluronic acid was incorporated during the sol formation. Structural, morphological, and optical properties of the films were investigated for different F127/Lu molar ratios (0–5) in order to obtain high optical quality films with enhanced thickness compared with the traditional method. X-ray diffraction (XRD) shows that the films present a highly oriented cubic structure <111> beyond 1073 K for a 3-layer film, on silica glass substrates. The thickness, density, porosity, and refractive index evolution of the films were investigated by means of m-lines microscopy along with the morphology by scanning electron microscope (SEM) and luminescent properties.     

Rapid expression of fibronectin in the rabbit heart after myocardial infarction with and without reperfusion.

The expression of fibronectin in the repair process after myocardial infarction was studied using two protocols of coronary occlusion in the rabbit: a permanent occlusion or 3 h of occlusion followed by reperfusion (too late for salvage). We found a rapid and progressive increase in cardiac fibronectin expression in the infarcted region of the ventricle. Steady-state mRNA levels for fibronectin increased 13- and 16-fold, respectively, in the permanent and reperfused infarcts 1 d postinfarction. Immunological detection of the protein with a polyclonal antibody against plasma fibronectin showed significant increases of the protein fibronectin in the infarcted myocardium by day 3 in the reperfused group and by day 5 in the permanent coronary occlusion group. Ribonuclease protection assays established the induction of EIIIB containing fibronectin mRNA in both models by day 1 and use of a monoclonal antibody showed an increase in the EIIIA isoform 2 d postinfarction. Increases in steady-state mRNA levels for several collagen types were found in both groups, but these changes occurred after those noted for fibronectin. Thus fibronectin mRNA and protein expression increased rapidly postinfarction suggesting a functional role in the repair process.     

Versatile use of skin expanders in facial plastic surgery.

Large soft-tissue resection defects of the face and scalp present an arduous technical problem for the facial plastic surgeon. Successfully matching tissue coverage with similar skin color and texture is usually limited by the amount of available local skin. Also, the need to limit distortion of fixed anatomic sites when harvesting local skin must be addressed. With the advent and utilization of soft-tissue expanders, the availability of local skin is increased and anatomic distortions are limited. This article describes the versatile use of skin expansion in facial plastic and reconstructive surgery. Expansion techniques include long-term expansion for scalp and cervicofacial defects. Acute intraoperative expansion techniques address repair of perioral, labial, and nasal mucosal lining defects. The success, limitations, and complications of these techniques are reviewed.