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Christos Constantinidis - One of the best experts on this subject based on the ideXlab platform.
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Lower neuronal variability in the monkey dorsolateral prefrontal than Posterior Parietal cortex
Journal of neurophysiology, 2015Co-Authors: Christos ConstantinidisAbstract:The dorsolateral prefrontal and Posterior Parietal cortex are two brain areas involved in cognitive functions such as spatial attention and working memory. When tested with identical tasks, only subtle differences in firing rate are present between neurons recorded in the two areas. In this article we report that major differences in neuronal variability characterize the two areas during working memory. The Fano factors of spike counts in dorsolateral prefrontal neurons were consistently lower than those of the Posterior Parietal cortex across a range of tasks, epochs, and conditions in the same monkeys. Variability differences were observed despite minor differences in firing rates between the two areas in the tasks tested and higher overall firing rate in the prefrontal than in the Posterior Parietal sample. Other measures of neuronal discharge variability, such as the coefficient of variation of the interspike interval, displayed the same pattern of lower prefrontal variability. Fano factor values were negatively correlated with performance in the working memory task, suggesting that higher neuronal variability was associated with diminished task performance. The results indicate that information involving remembered stimuli is more reliably represented in the prefrontal than the Posterior Parietal cortex based on the variability of neuronal responses, and suggest functional differentiation between the two areas beyond differences in firing rate.
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Representation of remembered stimuli and task information in the monkey dorsolateral prefrontal and Posterior Parietal cortex.
Journal of neurophysiology, 2014Co-Authors: Anthony C. Elworthy, Bryce C. Lambert, Christos ConstantinidisAbstract:Both dorsolateral prefrontal and Posterior Parietal cortex have been implicated in spatial working memory and representation of task information. Prior experiments training animals to recall the first of a sequence of stimuli and examining the effect of subsequent distractors have identified increased ability of the prefrontal cortex to represent remembered stimuli and filter distractors. It is unclear, however, if this prefrontal functional specialization extends to stimuli appearing earlier in a sequence, when subjects are cued to remember subsequent ones. It is also not known how task information interacts with persistent activity representing remembered stimuli and distractors in the two areas. To address these questions, we trained monkeys to remember either the first or second of two stimuli presented in sequence and recorded neuronal activity from the Posterior Parietal and dorsolateral prefrontal cortex. The prefrontal cortex was better able to represent the actively remembered stimulus, whereas the Posterior Parietal cortex was more modulated by distractors; however, task effects interfered with this representation. As a result, large proportions of neurons with persistent activity and task effects exhibited a preference for a stimulus when it appeared as a distractor in both areas. Additionally, prefrontal neurons were modulated to a greater extent by task factors during the delay period of the task. The results indicate that the prefrontal cortex is better able than the Posterior Parietal cortex to differentiate between distractors and actively remembered stimuli and is more modulated by the task; however, this relative preference is highly context dependent and depends on the specific requirements of the task.
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Influence of monkey dorsolateral prefrontal and Posterior Parietal activity on behavioral choice during attention tasks.
The European journal of neuroscience, 2014Co-Authors: Fumi Katsuki, Mizuki Saito, Christos ConstantinidisAbstract:The dorsolateral prefrontal and the Posterior Parietal cortex have both been implicated in the guidance of visual attention. Traditionally, Posterior Parietal cortex has been thought to guide visual bottom-up attention and prefrontal cortex to bias attention through top-down information. More recent studies suggest a parallel time course of activation of the two areas in bottom-up attention tasks, suggesting a common involvement, though these results do not necessarily imply identical roles. To address the specific roles of the two areas, we examined the influence of neuronal activity recorded from the prefrontal and Parietal cortex of monkeys as they performed attention tasks based on choice probability and on correlation between reaction time and neuronal activity. The results revealed that Posterior Parietal but not dorsolateral prefrontal activity correlated with behavioral choice during the fixation period, prior to the appearance of the stimulus, resembling a bias factor. This preferential influence of Posterior Parietal activity on behavior was transient, so that dorsolateral prefrontal activity predicted choice after the appearance of the stimulus. Additionally, reaction time was better predicted by Posterior Parietal activity. These findings confirm the involvement of both dorsolateral prefrontal and Posterior Parietal cortex in the bottom-up guidance of visual attention, but indicate different roles of the two areas in the guidance of attention and a dynamic time course of their effects, influencing behavior at different stages of the task.
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Cognitive Functions of the Posterior Parietal Cortex - Cognitive functions of the Posterior Parietal cortex.
Frontiers in integrative neuroscience, 2013Co-Authors: Christos Constantinidis, David J. Bucci, Michael D. RuggAbstract:The Posterior Parietal cortex has traditionally been associated with visuo-spatial perception and spatial attention, however, accumulating evidence indicates that it is involved in a much wider range of cognitive functions. The articles included in the E-book review experimental data and theoretical considerations, as well as reviews of recent work supporting this idea. Anatomical, lesion, neurophysiological, and functional imaging data are discussed. Animal models (rodent and primate) as well as human studies are covered. Finally, the unique and shared functions of the Posterior Parietal cortex are compared to other brain areas. These contributions provide a primer of the current state of knowledge, identify unresolved questions, highlight recent conceptual and methodological advances, and, we hope, will stimulate future research.
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Neural correlates of learning and working memory in the primate Posterior Parietal cortex
Neurobiology of learning and memory, 2009Co-Authors: Justin B. Rawley, Christos ConstantinidisAbstract:The Posterior Parietal cortex has been traditionally associated with coordinate transformations necessary for interaction with the environment and with visual-spatial attention. More recently, involvement of Posterior Parietal cortex in other cognitive functions such as working memory and task learning has become evident. Neurophysiological experiments in non-human primates and human imaging studies have revealed neural correlates of memory and learning at the single neuron and at the brain network level. During working memory, Posterior Parietal neurons continue to discharge and to represent stimuli that are no longer present. This activation resembles the responses of prefrontal neurons, although important differences have been identified in terms of the ability to resist stimulation by distracting stimuli, which is more evident in the prefrontal than the Posterior Parietal cortex. Posterior Parietal neurons also become active during tasks that require the organization of information into larger structured elements and their activity is modulated according to learned context-dependent rules. Neural correlates of learning can be observed in the mean discharge rate and spectral power of neuronal spike trains after training to perform new task sets or rules. These findings demonstrate the importance of Posterior Parietal cortex in brain networks mediating working memory and learning.
Richard A Andersen - One of the best experts on this subject based on the ideXlab platform.
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Human Posterior Parietal Cortex Plans Where to Reach and What to Avoid
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2010Co-Authors: Axel Lindner, Asha Iyer, Igor Kagan, Richard A AndersenAbstract:In this time-resolved functional magnetic resonance imaging (fMRI) study, we aimed to trace the neuronal correlates of covert planning processes that precede visually guided motor behavior. Specifically, we asked whether human Posterior Parietal cortex has prospective planning activity that can be distinguished from activity related to retrospective visual memory and attention. Although various electrophysiological studies in monkeys have demonstrated such motor planning at the level of Parietal neurons, comparatively little support is provided by recent human imaging experiments. Rather, a majority of experiments highlights a role of human Posterior Parietal cortex in visual working memory and attention. We thus sought to establish a clear separation of visual memory and attention from processes related to the planning of goal-directed motor behaviors. To this end, we compared delayed-response tasks with identical mnemonic and attentional demands but varying degrees of motor planning. Subjects memorized multiple target locations, and in a random subset of trials targets additionally instructed (1) desired goals or (2) undesired goals for upcoming finger reaches. Compared with the memory/attention-only conditions, both latter situations led to a specific increase of preparatory fMRI activity in Posterior Parietal and dorsal premotor cortex. Thus, Posterior Parietal cortex has prospective plans for upcoming behaviors while considering both types of targets relevant for action: those to be acquired and those to be avoided.
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Movement intention is better predicted than attention in the Posterior Parietal cortex
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2006Co-Authors: Rodrigo Quian Quiroga, Lawrence H. Snyder, Aaron P. Batista, He Cui, Richard A AndersenAbstract:We decoded on a trial-by-trial basis the location of visual targets, as a marker of the locus of attention, and intentions to reach and to saccade in different directions using the activity of neurons in the Posterior Parietal cortex of two monkeys. Predictions of target locations were significantly worse than predictions of movement plans for the same target locations. Moreover, neural signals in the Parietal reach region (PRR) gave better predictions of reaches than saccades, whereas signals in the lateral intraParietal area (LIP) gave better predictions of saccades than reaches. Taking together the activity of both areas, the prediction of either movement in all directions became nearly perfect. These results cannot be explained in terms of an attention effect and support the idea of two segregated populations in the Posterior Parietal cortex, PRR and LIP, that are involved in different movement plans.
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Sensorimotor Transformations in the Posterior Parietal Cortex
2004Co-Authors: Richard A Andersen, Daniella Meeker, Bijan Pesaran, Boris Breznen, Christopher A. Buneo, Hans ScherbergerAbstract:The Posterior Parietal cortex (PPC) sits at the interface between sensory and motor areas and performs sensorimotor transformations. Current research is beginning to unravel the details of this transformation process. The first part of this chapter focuses on planning signals found in the PPC. Experiments show that the thought to reach can be read out from the Parietal reach region of monkeys and used to control the position of a computer cursor without any reach movements being made by the monkeys. The second section reviews recent studies of coordinate tral15formations, which are an important aspect of sensorimotor transformations and involve the PPC.
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Intentional maps in Posterior Parietal cortex
Annual review of neuroscience, 2002Co-Authors: Richard A Andersen, Christopher A. BuneoAbstract:The Posterior Parietal cortex (PPC), historically believed to be a sensory structure, is now viewed as an area important for sensory-motor integration. Among its functions is the forming of intentions, that is, high-level cognitive plans for movement. There is a map of intentions within the PPC, with different subregions dedicated to the planning of eye movements, reaching movements, and grasping movements. These areas appear to be specialized for the multisensory integration and coordinate transformations required to convert sensory input to motor output. In several subregions of the PPC, these operations are facilitated by the use of a common distributed space representation that is independent of both sensory input and motor output. Attention and learning effects are also evident in the PPC. However, these effects may be general to cortex and operate in the PPC in the context of sensory-motor transformations.
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Electrical Microstimulation Distinguishes Distinct Saccade-Related Areas in the Posterior Parietal Cortex
Journal of neurophysiology, 1998Co-Authors: Peter Thier, Richard A AndersenAbstract:Thier, Peter and Richard A. Andersen. Electrical microstimulation distinguishes distinct saccade-related areas in the Posterior Parietal cortex. J. Neurophysiol. 80: 1713–1735, 1998. Electrical mic...
René Marois - One of the best experts on this subject based on the ideXlab platform.
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Posterior Parietal cortex activity predicts individual differences in visual short term memory capacity
Cognitive Affective & Behavioral Neuroscience, 2005Co-Authors: J. Jay Todd, René MaroisAbstract:Humans show a severe capacity limit in the number of objects they can store in visual short-term memory (VSTM). We recently demonstrated with functional magnetic resonance imaging that VSTM storage capacity estimated in averaged group data correlated strongly with Posterior Parietal/superior occipital cortex activity (Todd & Marois, 2004). However, individuals varied widely in their VSTM capacity. Here, we examined the neural basis of these individual differences. A voxelwise, individualdifferences analysis revealed a significant correlation between Posterior Parietal cortex (PPC) activity and individuals’ VSTM storage capacity. In addition, a region-of-interest analysis indicated that other brain regions, particularly visual occipital cortex, may contribute to individual differences in VSTM capacity. Thus, although not ruling out contributions from other brain regions, the individual-differences approach supports a key role for the PPC in VSTM by demonstrating that its activity level predicts individual differences in VSTM storage capacity.
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Capacity limit of visual short-term memory in human Posterior Parietal cortex
Nature, 2004Co-Authors: J. Jay Todd, René MaroisAbstract:At any instant, our visual system allows us to perceive a rich and detailed visual world. Yet our internal, explicit representation of this visual world is extremely sparse: we can only hold in mind a minute fraction of the visual scene. These mental representations are stored in visual short-term memory (VSTM). Even though VSTM is essential for the execution of a wide array of perceptual and cognitive functions, and is supported by an extensive network of brain regions, its storage capacity is severely limited. With the use of functional magnetic resonance imaging, we show here that this capacity limit is neurally reflected in one node of this network: activity in the Posterior Parietal cortex is tightly correlated with the limited amount of scene information that can be stored in VSTM. These results suggest that the Posterior Parietal cortex is a key neural locus of our impoverished mental representation of the visual world.
Kyungjin Kim - One of the best experts on this subject based on the ideXlab platform.
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neural correlates of superior intelligence stronger recruitment of Posterior Parietal cortex
NeuroImage, 2006Co-Authors: Kun Ho Lee, Yu Yong Choi, Jeremy R Gray, Sun Hee Cho, Jeongho Chae, Seungheun Lee, Kyungjin KimAbstract:General intelligence (g) is a common factor in diverse cognitive abilities and a major influence on life outcomes. Neuroimaging studies in adults suggest that the lateral prefrontal and Parietal cortices play a crucial role in related cognitive activities including fluid reasoning, the control of attention, and working memory. Here, we investigated the neural bases for intellectual giftedness (superior-g) in adolescents, using fMRI. The participants consisted of a superior-g group (n = 18, mean RAPM = 33.9 +/- 0.8, >99%) from the national academy for gifted adolescents and the control group (n = 18, mean RAPM = 22.8 +/- 1.6, 60%) from local high schools in Korea (mean age = 16.5 +/- 0.8). fMRI data were acquired while they performed two reasoning tasks with high and low g-loadings. In both groups, the high g-loaded tasks specifically increased regional activity in the bilateral fronto-Parietal network including the lateral prefrontal, anterior cingulate, and Posterior Parietal cortices. However, the regional activations of the superior-g group were significantly stronger than those of the control group, especially in the Posterior Parietal cortex. Moreover, regression analysis revealed that activity of the superior and intraParietal cortices (BA 7/40) strongly covaried with individual differences in g (r = 0.71 to 0.81). A correlated vectors analysis implicated bilateral Posterior Parietal areas in g. These results suggest that superior-g may not be due to the recruitment of additional brain regions but to the functional facilitation of the fronto-Parietal network particularly driven by the Posterior Parietal activation.
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Neural correlates of superior intelligence: Stronger recruitment of Posterior Parietal cortex
NeuroImage, 2005Co-Authors: Kun Ho Lee, Yu Yong Choi, Jeremy R Gray, Sun Hee Cho, Jeongho Chae, Seungheun Lee, Kyungjin KimAbstract:Received 20 April 2005; revised 21 July 2005; accepted 22 July 2005 General intelligence (g) is a common factor in diverse cognitive abilities and a major influence on life outcomes. Neuroimaging studies in adults suggest that the lateral prefrontal and Parietal cortices play a crucial role in related cognitive activities including fluid reasoning, the control of attention, and working memory. Here, we investigated the neural bases for intellectual giftedness (superior-g) in adolescents, using fMRI. The participants consisted of a superior-g group (n = 18, mean RAPM = 33.9 T 0.8, >99%) from the national academy for gifted adolescents and the control group (n = 18, mean RAPM = 22.8 T 1.6, 60%) from local high schools in Korea (mean age = 16.5 T 0.8). fMRI data were acquired while they performed two reasoning tasks with high and low g-loadings. In both groups, the high g-loaded tasks specifically increased regional activity in the bilateral fronto-Parietal network including the lateral prefrontal, anterior cingulate, and Posterior Parietal cortices. However, the regional activations of the superior-g group were significantly stronger than those of the control group, especially in the Posterior Parietal cortex. Moreover, regression analysis revealed that activity of the superior and intraParietal cortices (BA 7/40) strongly covaried with individual differences in g (r = 0.71 to 0.81). A correlated vectors analysis implicated bilateral Posterior Parietal areas in g. These results suggest that superior-g may not be due to the recruitment of additional brain regions but to the functional facilitation of the fronto-Parietal network particularly driven by the
Kiyomi Nakamura - One of the best experts on this subject based on the ideXlab platform.
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Auditory spatial discriminatory and mnemonic neurons in rat Posterior Parietal cortex.
Journal of neurophysiology, 1999Co-Authors: Kiyomi NakamuraAbstract:The present study was designed to investigate whether the rat Posterior Parietal cortex is involved in the perception and the representation of the auditory space. We recorded single neural activit...
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Head-centered representation and spatial memory in rat Posterior Parietal cortex
Psychobiology, 1998Co-Authors: Longtang L. Chen, Kiyomi NakamuraAbstract:Rodent Posterior Parietal cortex, similar to its homologue in primates, has been shown to be critically involved in spatial navigation. We summarize here selected neurophysiological data and their relevance to recent lesion-behavioral studies. The findings indicate that the rat Posterior Parietal cortex contains a significant proportion of neurons that code for head-centered (or body-centered) space by making use of the vestibular and proprioceptive inputs. Some Posterior Parietal neurons may store a working representation of space, which appears to be allocentric.
