1,720,975 research outputs found
Determining monkey free choice long before the choice is made: the principal role of prefrontal neurons involved in both decision and motor processes
Full text linkWhen choices are made freely, they might emerge from pre-existing neural activity. However, whether neurons in the prefrontal cortex (PF) show this anticipatory effect and, if so, in which part of the process they are involved is still debated. To answer this question, we studied PF activity in monkeys while they performed a strategy task. In this task when the stimulus changed from the previous trial, the monkeys had to shift their response to one of two spatial goals, excluding the one that had been previously selected. Under this free-choice condition, the prestimulus activity of the same neurons that are involved in decision and motor processes predicted future choices. These neurons developed the same goal preferences during the prestimulus presentation as they did later in the decision phase. In contrast, the same effect was not observed in motor-only neurons and it was present but weaker in decision-only neurons. Overall, our results suggest that the PF neuronal activity predicts upcoming actions mainly through the decision-making network that integrate in time decision and motor task aspects
A temporal gap in sensory streams amplifies the influence of subsequent input on decision making
No full textDecision making involves evaluating options and predicting their likely outcomes. Traditional laboratory studies of decision making often employ tasks involving the discrimination of perceptual evidence, where sensory information is constant and presented continuously. However, during natural behavior, decision making usually involves intermittent information streams, punctuated by periods with no input. To investigate decision making under such conditions, we designed a perceptual task where participants observed tokens sequentially jumping from a central circle to one of two peripheral targets, disappearing shortly after. Participants were required to report which target they believed would have received most tokens by the trial’s end. Half of the trials included a temporal gap, during which no information was displayed. To better understand decision-making dynamics, we introduced specific patterns of token jumps. We found that participants made choices with less available information and disproportionally weighted the information presented immediately after the gap more heavily than they did when no gap was present. Traditional computational models, which assume uniform or gradual decay or increase of weighting of information over time, could not account for this effect. A control task with randomly presented information further confirmed that the disproportionate weighting of post-gap information is a robust feature of the decision-making process. These findings highlight the importance of studying decision making in environments with intermittent information and temporal gaps, where the timing and structure of inputs critically shape behavior
Interference between Space and Time Estimations: From Behavior to Neurons
Full text linkInfluences between time and space can be found in our daily life in which we are surrounded by numerous spatial metaphors to refer to time. For instance, when we move files from one folder to another in our computer a horizontal line that grows from left to right informs us about the elapsed and remaining time to finish the procedure and, similarly, in our communication we use several spatial terms to refer to time. Although with some differences in the degree of interference, not only space has an influence on time but both magnitudes influence each other. Indeed, since our childhood our estimations of time are influenced by space even when space should be irrelevant and the same occurs when estimating space with time as distractor. Such interference between magnitudes has also been observed in monkeys even if they do not use language or computers, suggesting that the two magnitudes are tightly coupled beyond communication and technology. Imaging and lesion studies have indicated that same brain areas are involved during the processing of both magnitudes and have suggested that rather than coding the specific magnitude itself the brain represents them as abstract concepts. Recent neurophysiological studies in prefrontal cortex, however, have shown that the coding of absolute and relative space and time in this area is realized by independent groups of neurons. Interestingly, instead, a high overlap was observed in this same area in the coding of goal choices across tasks. These results suggest that rather than during perception or estimation of space and time the interference between the two magnitudes might occur, at least in the prefrontal cortex, in a subsequent phase in which the goal has to be chosen or the response provided
Independent coding of absolute duration and distance magnitudes in the prefrontal cortex
Full text linkThe estimation of space and time can interfere with each other, and neuroimaging studies have shown overlapping activation in the parietal and prefrontal cortical areas. We used duration and distance discrimination tasks to determine whether space and time share resources in prefrontal cortex (PF) neurons. Monkeys were required to report which of two stimuli, a red circle or blue square, presented sequentially, were longer and farther, respectively, in the duration and distance tasks. In a previous study, we showed that relative duration and distance are coded by different populations of neurons and that the only common representation is related to goal coding. Here, we examined the coding of absolute duration and distance. Our results support a model of independent coding of absolute duration and distance metrics by demonstrating that not only relative magnitude but also absolute magnitude are independently coded in the PF
Autocorrelation structure in the macaque dorsolateral, but not orbital or polar, prefrontal cortex predicts response-coding strength in a visually cued strategy task
No full textIn previous work, we studied the activity of neurons in the dorsolateral (PFdl), orbital (PFo), and polar (PFp) prefrontal cortex
while monkeys performed a strategy task with 2 spatial goals. A cue instructed 1 of 2 strategies in each trial: stay with
the previous goal or shift to the alternative goal. Each trial started with a fixation period, followed by a cue. Subsequently,
a delay period was followed by a “go” signal that instructed the monkeys to choose one goal. After each choice, feedback
was provided. In this study, we focused on the temporal receptive fields of the neurons, as measured by the decay in
autocorrelation (time constant) during the fixation period, and examined the relationship with response and strategy
coding. The temporal receptive field in PFdl correlated with the response-related but not with the strategy-related
modulation in the delay and the feedback periods: neurons with longer time constants in PFdl tended to show stronger
and more prolonged response coding. No such correlation was found in PFp or PFo. These findings demonstrate that the
temporal specialization of neurons for temporally extended computations is predictive of response coding, and neurons
in PFdl, but not PFp or PFo, develop such predictive properties
Outcome modulation across tasks in the primate dorsolateral prefrontal cortex
Full text linkAnimals need to learn and to adapt to new and changing environments so that appropriate actions that lead to desirable outcomes are acquired within each context. The prefrontal cortex (PF) is known to underlie such function that directly implies that the outcome of each response must be represented in the brain for behavioral policies update. However, whether such PF signal is context dependent or it is a general representation beyond the specificity of a context is still unclear. Here, we analyzed the activity of neurons in the dorsolateral PF (PFdl) recorded while two monkeys performed two perceptual magnitude discrimination tasks. Both tasks were well known by the monkeys and unexpected changes did not occur but the difficulty of the task varied from trial to trial and thus the monkeys made mistakes in a proportion of trials. We show a context-independent coding of the response outcome with neurons maintaining similar selectivity in both task contexts. Using a classification method of the neural activity, we also show that the trial outcome could be well predicted from the activity of the same neurons in the two contexts. Altogether, our results provide evidence of high degree of outcome generality in PFdl
Coding of self and other's future choices in dorsal premotor cortex during social interaction
Full text linkRepresenting others’ intentions is central to primate social life. We explored the role of dorsal premotor cortex (PMd) in discriminating between self and others’ behavior while two male rhesus monkeys performed a non-match-to-goal task in a monkey-human paradigm. During each trial, two of four potential targets were randomly presented on the right and left parts of a screen, and the monkey or the human was required to choose the one that did not match the previously chosen target. Each agent had to monitor the other's action in order to select the correct target in that agent's own turn. We report neurons that selectively encoded the future choice of the monkey, the human agent, or both. Our findings suggest that PMd activity shows a high degree of self-other differentiation during face-to-face interactions, leading to an independent representation of what others will do instead of entailing self-centered mental rehearsal or mirror-like activities. Understanding others’ intentions is essential to successful primate social life. Cirillo et al. explore the role of dorsal premotor cortex (PMd) in discriminating between self and others’ behavior while macaques interacted with humans. They show that the majority of neurons encoding the future choice did so selectively for the monkey or the human agent. PMd thus differentiates self from others’ behavior, leading to independent representations of future actions
Neural variability in premotor cortex is modulated by trial history and predicts behavioral performance
No full textIn the study of decision making, emphasis is placed on different forms of perceptual integration, while the influence of other factors, such as memory, is ignored. In addition, it is believed that the information underlying decision making is carried in the rate of the neuronal response, while its variability is considered unspecific. Here we studied the influence of recent experience on motor decision making by analyzing the activity of neurons in the dorsal premotor area of two monkeys performing a countermanding arm task. We observe that the across-trial variability of the neural response strongly correlates with trial history-dependent changes in reaction time. Using a theoretical model of decision making, we show that a trial history-monitoring signal can explain the observed behavioral and neural modulation. Our study reveals that, in the neural processes that culminate in motor plan maturation, the evidence provided by perception and memory is reflected in mean rate and variance respectivel
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
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