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SummaryNon-human primate neuroimaging is a rapidly growing area of research that promises to transform and scale translational and cross-species comparative neuroscience. Unfortunately, the technological and methodological advances of the past two decades have outpaced the accrual of data, which is particularly challenging given the relatively few centers that have the necessary facilities and capabilities. The PRIMatE Data Exchange (PRIME-DE) addresses this challenge by aggregating independently acquired non-human primate magnetic resonance imaging (MRI) datasets and openly sharing them via the International Neuroimaging Data-sharing Initiative (INDI). Here, we present the rationale, design, and procedures for the PRIME-DE consortium, as well as the initial release, consisting of 25 independent data collections aggregated across 22 sites (total = 217 non-human primates). We also outline the unique pitfalls and challenges that should be considered in the analysis of non-human primate MRI datasets, including providing automated quality assessment of the contributed datasets.

Abstract-Persistent elevated neuronal activity has been identified as the neuronal correlate of working memory. It is generally assumed in the literature and in computational and theoretical models of working memory that memory-cell activity is stable and replicable; however, this assumption may be an artifact of the averaging of data collected across trials, and needs experimental verification. In this study, we introduce a classification scheme to characterize the firing frequency trends of cells recorded from the cortex of monkeys during performance of working memory tasks. We examine the frequency statistics and variability of firing during baseline and memory periods. We also study the behavior of cells on individual trials and across trials, and explore the stability of cellular firing during the memory period. We find that cells from different firing-trend classes possess markedly different statistics. We also find that individual cells show substantial variability in their firing behavior across trials, and that firing frequency also varies markedly over the course of a single trial. Finally, the average frequency distribution is wider, the magnitude of the frequency increases from baseline to memory smaller, and the magnitude of frequency decreases larger than is generally assumed. These results may serve as a guide in the evaluation of current theories of the cortical mechanisms of working memory. © 2007 IBRO. Published by Elsevier Ltd. All rights reserved.Key words: spike trains, monkeys, memory networks, parietal cortex, prefrontal cortex, computational models.The electrophysiological study of the neuronal basis of working memory in primates has traditionally focused on the changes in single-cell average frequency that may occur during the mnemonic retention of a stimulus cue in delayed-response tasks. Experiments dealing with this issue have led to the identification of cells, generally labeled "memory cells," that show a persistent increase in their average firing frequency (AF) during the memory period of a memory task (Fuster, 1997). Memory cells have been identified in multiple cortical regions, including prefrontal (Fuster and Alexander, 1971;Fuster, 1973;Niki, 1974;Niki and Watanabe, 1976;Funahashi et al., 1989;Miller et al., 1996;Rao et al., 1997;Romo et al., 1999), parietal (Gnadt and Andersen, 1988;Koch and Fuster, 1989;Andersen et al., 1990;Barash et al., 1991; Fuster, 1996, 1997), and inferotemporal Jervey, 1981, 1982;Miyashita and Chang, 1988;Fuster, 1990;Miller et al., 1993;Chelazzi et al., 1993Chelazzi et al., , 1998Colombo and Gross, 1994;Gibson and Maunsell, 1997) cortex. A variety of studies have shown that memory cells in all three of these associative regions are involved in the retention of a given sensory cue for a prospective motor response. It has also been shown that cells within a given region can retain associated items of more than one modality (Haenny et al., 1988;Maunsell et al., 1991;Colombo and Gross, 1994;Bodner et al., 1996;Gibson and Maunsell, 1997; Fuster, 1997,...

Recent studies show that cells in the somatosensory cortex are involved in the short-term retention of tactile information. In addition, some somatosensory cells appear to retain visual information that has been associated with the touch of an object. The presence of such cells suggests that nontactile stimuli associated with touch have access to cortical neuron networks engaged in the haptic sense. Thus, we inferred that somatosensory cells would respond to behaviorally associated visual and tactile stimuli. To test this assumption, single units were recorded from the anterior parietal cortex (Brodmann's areas 3a, 3b, 1, and 2) of monkeys performing a visuo-haptic delay task, which required the memorization of a visual cue for a tactile choice. Most cells responding to that cue responded also to the corresponding object presented for tactile choice. Significant correlations were observed in some cells between their differential reactions to tactile objects and their differential reactions to the associated visual cues. Some cells were recorded in both the cross-modal task and a haptic unimodal task, where the animal had to retain a tactile cue for a tactile choice. In most of these cells, correlations were observed between stimulusrelated firing in corresponding cue periods of the two tasks. These findings suggest that cells in somatosensory cortex are the components of neuronal networks representing tactile information. Associated visual stimuli may activate such networks through visuo-haptic associations established by behavioral training.somatosensory cortex ͉ monkey ͉ single units A natomical and physiological studies indicate that somatosensory information is processed both in parallel and sequentially through areas 3, 1, and 2 of anterior parietal cortex (1-6). Cells in these areas respond not only to the passive touch of the hand (7, 8) but also to the active grasping of objects (9-13). Recent work (14) indicates that cells in somatosensory cortex significantly change their firing frequency while the animal has to memorize information about a tactile stimulus for a later behavioral choice. In some cells, that change in firing is selective (stimulus dependent). Furthermore, in a cross-modal (visuohaptic) delay task (15), some cells appear to participate in the short-term retention of associated nontactile (visual) information for a later tactile choice. This evidence suggests that somatosensory cells are part of widely distributed cortical networks that are active in the perception and short-term memory of haptic information. In haptic behavior, one such network and its constituent neurons may be activated by any of the stimuli behaviorally associated with a tactile discrimination, including those of other sensory modalities. Following this reasoning, we assumed that, during the performance by the animal of a cross-modal visuo-haptic task, somatosensory cells would show similar responses to pairs of visual and tactile stimuli that have been associated with each other by prior training. Electrophysiologica...

Single-unit activity was recorded from the hand areas of the somatosensory cortex of monkeys trained to perform a haptic delayed matching to sample task with objects of identical dimensions but different surface features. During the memory retention period of the task (delay), many units showed sustained firing frequency change, either excitation or inhibition. In some cases, firing during that period was significantly higher after one sample object than after another. These observations indicate the participation of somatosensory neurons not only in the perception but in the short-term memory of tactile stimuli. Neurons most directly implicated in tactile memory are (i) those with object-selective delay activity, (ii) those with nondifferential delay activity but without activity related to preparation for movement, and (iii) those with delay activity in the haptic-haptic delayed matching task but no such activity in a control visuo-haptic delayed matching task The results indicate that cells in early stages of cortical somatosensory processing participate in haptic short-term memory.For more than two decades it has been known that certain neurons in the association cortex of the primate undergo sustained activation while the animal is memorizing an item of sensory information for the execution of a behavioral action in the near term (1). These so-called memory cells were first discovered in prefrontal cortex (2-5), where they appear to be part of neuronal networks that encode a large variety of sensory memoranda associated with impending action. Visual memory cells have been found in inferotemporal assQciation cortex (6-8), and tactile memory cells have been found in parietal association cortex (9). Whereas thus far memory cells have been reported almost exclusively in association cortex, there are indications that they may be found also in somatosensory (9) and visual (10) cortex. Their presence in these cortices may reflect the role of short-term memory in sensory perception, including haptics-that is, the perception by active touch (11). The recognition of an object by palpation requires the integration of temporally separate tactile impressions, which in turn presumably requires some degree of short-term memory already at early stages of the somatic sensory system. The present study explores the somatosensory cortex for evidence of haptic memory cells in monkeys performing a tactile working memory task. The results reveal a substantial proportion of such cells in hand representation areas. METHODSThree adult, male rhesus monkeys (Macaca mulatta), weighing 8-10 kg, were the subjects of this research. The monkeys were individually housed and fed an ad libitum diet of chow and, periodically, some fruit. Intake of fluid was restricted before experimental sessions. In the course of several months, the animals were trained to perform the haptic delayed matching to sample task described below. After training, microelectrode recording devices were surgically implanted (Nembutal anesthesia) over parietal co...

This paper considers a proportional hazards model, which allows one to examine the extent to which covariates interact nonlinearly with an exposure variable, for analysis of lifetime data. A local partial-likelihood technique is proposed to estimate nonlinear interactions. Asymptotic normality of the proposed estimator is established. The baseline hazard function, the bias and the variance of the local likelihood estimator are consistently estimated. In addition, a one-step local partial-likelihood estimator is presented to facilitate the computation of the proposed procedure and is demonstrated to be as efficient as the fully iterated local partial-likelihood estimator. Furthermore, a penalized local likelihood estimator is proposed to select important risk variables in the model. Numerical examples are used to illustrate the effectiveness of the proposed procedures.Comment: Published at http://dx.doi.org/10.1214/009053605000000796 in the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

The logistic regression model M1, can predict which PULs will become failing PULs, IUPs and, most importantly, EPs based on the patient's HCG ratio alone.

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