Papers by Pieter Roelfsema
Lorteije et al. found behavioral and physiological evidence that the primate brain can process mu... more Lorteije et al. found behavioral and physiological evidence that the primate brain can process multiple decisions in parallel. Besides decreasing overall processing time, parallel decisions can influence each other and, thereby, maximize the reward income. Lorteije et al., 2015, Neuron 87, 1-13 September 23, 2015 ª2015 Elsevier Inc. http://dx.
Proceedings of the National Academy of Sciences, 2013
Stimuli associated with high rewards evoke stronger neuronal activity than stimuli associated wit... more Stimuli associated with high rewards evoke stronger neuronal activity than stimuli associated with lower rewards in many brain regions. It is not well understood how these reward effects influence activity in sensory cortices that represent low-level stimulus features. Here, we investigated the effects of reward information in the primary visual cortex (area V1) of monkeys. We found that the reward value of a stimulus relative to the value of other stimuli is a good predictor of V1 activity. Relative value biases the competition between stimuli, just as has been shown for selective attention. The neuronal latency of this reward value effect in V1 was similar to the latency of attentional influences. Moreover, V1 neurons with a strong value effect also exhibited a strong attention effect, which implies that relative value and top-down attention engage overlapping, if not identical, neuronal selection mechanisms. Our findings demonstrate that the effects of reward value reach down to the earliest sensory processing levels of the cerebral cortex and imply that theories about the effects of reward coding and top-down attention on visual representations should be unified.
Proceedings of the National Academy of Sciences, 2015
Object Recognition and Image Parsing of Natural Images
Page 1. Object Recognition and Image Parsing of Natural Images Danique JJDM Jeurissen 1 *, Ilia K... more Page 1. Object Recognition and Image Parsing of Natural Images Danique JJDM Jeurissen 1 *, Ilia Korjoukov 1 , Niels Kloosterman 2 , H. Steven Scholte 2 , and Pieter R. Roelfsema 1,3 1 Vision and Cognition Group, Netherlands ...
Attention in mental curve tracing task is not zoom-lens or spotlight based
Cerebral Cortex
Most cognitive functions are based on highly parallel and distributed information processing by t... more Most cognitive functions are based on highly parallel and distributed information processing by the brain. A paradigmatic example is provided by the vertebrate visual system where numerous cortical areas have been described which analyse different types of visual information. At present, it is unclear how information can be integrated and how coherent representational states can be established in such distributed systems. We suggest that this so-called 'binding problem' may be solved in the temporal domain. The hypothesis is that synchronization of neuronal discharges can serve for the integration of distributed neurons into cell assemblies and that this process may underlie the selection of perceptually and behaviourally relevant information. We review experimental results, mainly obtained in the visual system, which support this temporal binding hypothesis.
Most cognitive functions are based on highly parallel and distributed information processing by t... more Most cognitive functions are based on highly parallel and distributed information processing by the brain. A paradigmatic example is provided by the ver tebrate visual system where numerous cortical areas have been described which anal yse different types of visual information. At present, it is unclear how information can be integrated and how coherent representational states can be established in such distributed systems. We suggest that this so-called "binding problem" may be solved in the temporal domain. The hypothesis is that synchronization of neuronal discharges can serve for the integration of distributed neurons into coherent cell assemblies and that this process may underlie the selection of perceptually or behaviourally relevant information. In this paper, we review experimental results, mainly obtained in the visual system, which support this temporal binding hypothe sis. In addition, we discuss the implications of this hypothesis as a heuristic for neu robiological research.
Chronic multiple recordings in behaving animals: Advantages and limitations
Development, Dynamics and Pathology of Neuronal Networks: From Molecules to Functional Circuits
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience
Experiences can alter functional properties of neurons in primary sensory neocortex but it is poo... more Experiences can alter functional properties of neurons in primary sensory neocortex but it is poorly understood how stimulus-reward associations contribute to these changes. Using in vivo two-photon calcium imaging in mouse primary visual cortex (V1), we show that association of a directional visual stimulus with reward results in broadened orientation tuning and sharpened direction tuning in a stimulus-selective subpopulation of V1 neurons. Neurons with preferred orientations similar, but not identical to, the CS+ selectively increased their tuning curve bandwidth and thereby exhibited an increased response amplitude at the CS+ orientation. The increase in response amplitude was observed for a small range of orientations around the CS+ orientation. A nonuniform spatial distribution of reward effects across the cortical surface was observed, as the spatial distance between pairs of CS+ tuned neurons was reduced compared with pairs of CS- tuned neurons and pairs of control directions...
A key function of brains is undoubtedly the abstraction and maintenance of information from the e... more A key function of brains is undoubtedly the abstraction and maintenance of information from the environment for later use. Neurons in association cortex play an important role in this process: by learning these neurons become tuned to relevant features and represent the information that is required later as a persistent elevation of their activity. It is however not well known how such neurons acquire these task-relevant working memories. Here we introduce a biologically plausible learning scheme grounded in Reinforcement Learning (RL) theory that explains how neurons become selective for relevant information by trial and error learning. The model has memory units which learn useful internal state representations to solve working memory tasks by transforming partially observable Markov decision problems (POMDP) into MDPs. We propose that synaptic plasticity is guided by a combination of attentional feedback signals from the action selection stage to earlier processing levels and a g...
How does the brain learn to map multi-dimensional sensory inputs to multi-dimensional motor outpu... more How does the brain learn to map multi-dimensional sensory inputs to multi-dimensional motor outputs when it can only observe single rewards for the coordinated outputs of the whole network of neurons that make up the brain? We introduce Multi-AGREL, a novel, biologically plausible multi-layer neural network model for multi-dimensional reinforcement learning. We demonstrate that Multi-AGREL can learn non-linear mappings from inputs to multi-dimensional outputs by using only scalar reward feedback. We further show that in Multi-AGREL, the changes in the connection weights follow the gradient that minimizes global prediction error, and that all information required for synaptic plasticity is locally present.
BMC Neuroscience
Almost all animal behaviors can be seen as sequences of actions towards achieving certain goals. ... more Almost all animal behaviors can be seen as sequences of actions towards achieving certain goals. How the association cortices learn to link sensory stimuli to a correct sequence of motor responses is not well understood, especially when only a correct sequence of responses is rewarding. We present a biologically plausible neuronal network model that can be trained to perform a large variety of tasks when only stimuli and reward contingencies are varied. The model’s aim is to learn action values in a feedforward neuronal network and we present mechanisms to overcome the structural and temporal credit assignment problems. The temporal credit assignment problem is solved by a form of Q-learning [1]. The structural credit assignment problem is solved by a form of ‘attentional’ feedback from motor cortex to association cortex that delineates the units that should change connectivity to improve behavior [2]. Moreover, the model has a new mechanism to store traces of relevant sensory stimu...
PLoS computational biology, 2015
Intelligence is our ability to learn appropriate responses to new stimuli and situations. Neurons... more Intelligence is our ability to learn appropriate responses to new stimuli and situations. Neurons in association cortex are thought to be essential for this ability. During learning these neurons become tuned to relevant features and start to represent them with persistent activity during memory delays. This learning process is not well understood. Here we develop a biologically plausible learning scheme that explains how trial-and-error learning induces neuronal selectivity and working memory representations for task-relevant information. We propose that the response selection stage sends attentional feedback signals to earlier processing levels, forming synaptic tags at those connections responsible for the stimulus-response mapping. Globally released neuromodulators then interact with tagged synapses to determine their plasticity. The resulting learning rule endows neural networks with the capacity to create new working memory representations of task relevant information as persi...
Journal of vision, 2015
Figure-ground segregation is an important step in the path leading to object recognition. The vis... more Figure-ground segregation is an important step in the path leading to object recognition. The visual system segregates objects ('figures') in the visual scene from their backgrounds ('ground'). Electrophysiological studies in awake-behaving monkeys have demonstrated that neurons in early visual areas increase their firing rate when responding to a figure compared to responding to the background. We hypothesized that similar changes in neural firing would take place in early visual areas of the human visual system, leading to changes in the perception of low-level visual features. In this study, we investigated whether contrast perception is affected by figure-ground assignment using stimuli similar to those in the electrophysiological studies in monkeys. We measured contrast discrimination thresholds and perceived contrast for Gabor probes placed on figures or the background and found that the perceived contrast of the probe was increased when it was placed on a figu...
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2002
Spike and local field potential activity were recorded simultaneously from multiple sites in prim... more Spike and local field potential activity were recorded simultaneously from multiple sites in primary visual cortex of strabismic cats, while monocular stimulation alternated with dichoptic stimulation, inducing interocular rivalry. During interocular rivalry, there is competition between the two nonfusible stimuli presented to the two eyes, and only one stimulus is selected at any time. We biased this competition in three different ways: (1) we exploited the condition that in strabismic cats there is often one dominant eye that is selected for most of the time. (2) We presented the two stimuli with a temporal offset, which biases competition in favor of the newly appearing stimulus. (3) We presented the two stimuli with highly different contrasts, which biases competition in favor of the stimulus with higher contrast. Whenever competition was biased in favor of the stimulus activating the recorded neurons, gamma-frequency synchronization of the respective responses was enhanced, and...
Solutions for the binding problem
Zeitschrift für Naturforschung. C, Journal of biosciences
Visual cortical neurons are broadly tuned to one or a few feature dimensions, like color and moti... more Visual cortical neurons are broadly tuned to one or a few feature dimensions, like color and motion. This is advantageous because broadly tuned neurons can contribute to the representation of many visual scenes. However, if there are multiple objects in a visual scene, the cortex is at risk to combine features of different objects as if they belong to a single object. The term "binding problem" was introduced to refer to the difficulties that may occur in sorting out those responses that are evoked by a single perceptual object. The present article reviews proposals suggesting that the binding problem is solved by labelling an assembly of neurons that is responsive to a single perceptual object. Evidence is reviewed in favor of two possible assembly-labels: rate enhancement due to visual attention and neuronal synchrony. Assembly-labels should be spread through the cortical network to all neurons that have to participate in an assembly. The present article tries to shed li...
Trends in Cognitive Sciences, 2010
Papers in Physics, 2013
We describe the operation of a neuronal device which embodies the computational principles of the... more We describe the operation of a neuronal device which embodies the computational principles of the "paper-and-pencil" machine envisioned by Alan Turing. The network is based on principles of cortical organization. We develop a plausible solution to implement pointers and investigate how neuronal circuits may instantiate the basic operations involved in assigning a value to a variable (i.e., x = 5), in determining whether two variables have the same value and in retrieving the value of a given variable to be accessible to other nodes of the network. We exemplify the collective function of the network in simplified arithmetic and problem solving (blocks-world) tasks. *
Proceedings of the National Academy of Sciences, 2014
This Feature Article is part of a series identified by the Editorial Board as reporting findings ... more This Feature Article is part of a series identified by the Editorial Board as reporting findings of exceptional significance.
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Papers by Pieter Roelfsema