1,721,004 research outputs found
Neural correlates of cognitive control of reaching movements in the dorsal premotor cortex of rhesus monkeys
Full text linkMirabella G, Pani P, Ferraina S. Neural correlates of cognitive control of reaching movements in the dorsal premotor cortex of rhesus monkeys. J Neurophysiol 106: 1454-1466, 2011. First published June 22, 2011; doi: 10.1152/jn.00995.2010.-Canceling a pending movement is a hallmark of voluntary behavioral control because it allows us to quickly adapt to unattended changes either in the external environment or in our thoughts. The countermanding paradigm allows the study of inhibitory processes of motor acts by requiring the subject to withhold planned movements in response to an infrequent stop-signal. At present the neural processes underlying the inhibitory control of arm movements are mostly unknown. We recorded the activity of single units in the rostral and caudal portion of the dorsal premotor cortex (PMd) of monkeys trained in a countermanding reaching task. We found that among neurons with a movement-preparatory activity, about one-third exhibit a modulation before the behavioral estimate of the time it takes to cancel a planned movement. Hence these neurons exhibit a pattern of activity suggesting that PMd plays a critical role in the brain networks involved in the control of arm movement initiation and suppression.Mirabella G, Pani P, Ferraina S. Neural correlates of cognitive control of reaching movements in the dorsal premotor cortex of rhesus monkeys. J Neurophysiol 106: 1454-1466, 2011. First published June 22, 2011; doi: 10.1152/jn.00995.2010.-Canceling a pending movement is a hallmark of voluntary behavioral control because it allows us to quickly adapt to unattended changes either in the external environment or in our thoughts. The countermanding paradigm allows the study of inhibitory processes of motor acts by requiring the subject to withhold planned movements in response to an infrequent stop-signal. At present the neural processes underlying the inhibitory control of arm movements are mostly unknown. We recorded the activity of single units in the rostral and caudal portion of the dorsal premotor cortex (PMd) of monkeys trained in a countermanding reaching task. We found that among neurons with a movement-preparatory activity, about one-third exhibit a modulation before the behavioral estimate of the time it takes to cancel a planned movement. Hence these neurons exhibit a pattern of activity suggesting that PMd plays a critical role in the brain networks involved in the control of arm movement initiation and suppression
Reply to: Hannah et al. (2021) Commentary: ‘Does action-stopping involve separate pause and cancel processes? A view from premotor cortex’: Action-stopping models must consider the role of the dorsal premotor cortex
No full textDorsal premotor cortex neurons signal the Level of choice difficulty during logical decisions
Full text linkStudies on the neuronal correlates of decision making have demonstrated that the continuous flow of sensorial information is integrated by sensorimotor brain areas in order to select one among simultaneously represented targets and potential actions. In contrast, little is known about how these areas integrate memory information to lead to similar decisions. Using serial order learning, we explore how fragments of information, learned and stored independently (e.g., A > B and B > C), are linked in an abstract representation according to their reciprocal relations (such as A > B > C) and how this representation can be accessed and manipulated to make decisions. We show that manipulating information after learning occurs with increased difficulty as logical relationships get closer in the mental map and that the activity of neurons in the dorsal premotor cortex (PMd) encodes the difficulty level during target selection for motor decision making at the single-neuron and population levels
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Neuronal dynamics of signal selective motor plan cancellation in macaque dorsal premotor cortex
No full textForcing the winning horse: how the amount of force on a push button affects the inhibition of finger release in a stop signal task
No full textSuppressing a pending action is an essential ability when someone must cope with an unpredictable situation. This component of executive control has been extensively studied by the stop-signal task (SST). SST is a task requiring to respond with a movement to a go signal (go trials) but to refrain from the movement when occasionally a stop signal occurs after the go signal (stop trials). A theoretical model describes the outcome in stop trials as a race towards a threshold between a go and a stop process. Every time the go process runs faster than the stop process the movement cannot be interrupted (stop error trials). In addition, it has been hypothesized the go process as a two-stage process including: 1) a controlled stage (CS), that can be inhibited at any time; 2) a ballistic stage (BS), that cannot be inhibited. A point-of-no-return defines the crossing line between CS and BS. It has been reported that perceptual and cognitive variables can affect the duration of CS and influence the probability of the stop process to win the race. Besides these factors, for some effectors, the state of biomechanics variables could influence the start of the go process. For example, we can hypothesize that if we ask someone to push a button and then release it in response to a go signal, the strength applied to push the button at the beginning of a given trial could play a role in influencing the CS of button release and, consequently, the run of the go process against the stop process. Here we tested this hypothesis by studying 20 healthy volunteers performing a button release SST while monitoring the time evolution of CS by a force sensor resistor (FSR) fixed on a mouse button. The analysis of the perturbation of FSR revealed in a proportion of correctly stopped trials, defined as “partial errors”, an initial decline of the force applied on the button (as in go trials), followed by a rising back of it. This FSR pattern was never observed in stop error trials. Looking at the amount of force exerted on the button at the beginning of trials, it was significantly higher in partial error than in stop error trials, suggesting that trials started with an initial high force on the button have higher probability to turn in correct for higher differences between the force at the beginning of CS and that at the time of movement onset. Moreover, in partial errors the velocity of decay of the FSR signal was lower than in stop error trials, allowing subjects to stay within the CS for longer. These results point out that models of movement inhibition need to account for the biomechanical state of the effector before the go-signal
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