Igor Kagan

German Primate Center | DPZ

Neuroeconomics theories propose that the value associated with diverse rewards or reward-predicting stimuli is encoded along a common reference scale, irrespective of their sensory properties. However, in a dynamic environment with changing stimulus-reward pairings, the brain must also represent the sensory features of rewarding stimuli. The mechan...

Human perception is susceptible to social influences. To determine if and how individuals opportunistically integrate real-time social information about noisy stimuli into their judgment, we tracked perceptual accuracy and confidence in social (dyadic) and non-social (solo) settings using a novel continuous perceptual report (CPR) task with peri-de...

Human perception is susceptible to social influences. To determine if and how individuals opportunistically integrate real-time social information about noisy stimuli into their judgment, we tracked perceptual accuracy and confidence in social (dyadic) and non-social (solo) settings using a novel continuous perceptual report (CPR) task with peri-de...

The dorsal pulvinar has been implicated in visuospatial attentional and perceptual confidence processing. Pulvinar lesions in humans and monkeys lead to spatial neglect symptoms, including an overt spatial saccade bias during free choices. However, it remains unclear whether disrupting the dorsal pulvinar during target selection that relies on a pe...

Spatial accuracy in electrophysiological investigations is paramount, as precise localization and reliable access to specific brain regions help the advancement of our understanding of the brain’s complex neural activity. Here, we introduce a novel, multi camera-based, frameless neuronavigation technique for precise, 3-dimensional electrode positio...

When comparing themselves with others, people often evaluate their own behaviors more favorably. This egocentric tendency is often categorized as a bias of attribution, with favorable self-evaluation resulting from differing explanations of one’s own behavior and that of others. However, studies on information availability in social contexts offer...

Previous tablet studies indicate that children learn object labels better through active initiation rather than passive observation. However, as children typically learn object labels through interactions with familiar partners, this study examines whether the active learning advantage persists in dynamic face-to-face interactions and is influenced...

Visual perceptual learning is traditionally thought to arise in visual cortex. However, typical perceptual learning tasks also involve systematic mapping of visual information onto motor actions. Because the motor system contains both effector-specific and effector-unspecific representations, the question arises whether visual perceptual learning i...

The Cerebral Cortex and Thalamus is guided by two central and related tenets, the thalamus plays an ongoing and essential role in cortical functioning, and the cortex is essential for thalamic functioning. Accordingly, neither the cortex nor the thalamus can be understood in any meaningful way in the absence of the other. With chapters written by m...

We developed a continuous perceptual report (CPR) task that provides, by way of peri-decision wagering, an assessment of multiple dimensions of real-time perceptual decision-making. Using the CPR task, we have measured human behavior in social and non-social settings. We show that performance and perceptual confidence are not only determined by tas...

The dorsal pulvinar has been implicated in visuospatial attentional and perceptual confidence processing. Pulvinar lesions in humans and monkeys lead to spatial neglect symptoms, including an overt spatial saccade bias during free choices. But it remains unclear whether disrupting the dorsal pulvinar during target selection that relies on a percept...

Causal perturbations suggest that primate dorsal pulvinar plays a crucial role in target selection and saccade planning, though its basic neuronal properties remain unclear. Some functional aspects of dorsal pulvinar and interconnected frontoparietal areas—e.g. ipsilesional choice bias after inactivation—are similar. But it is unknown if dorsal pul...

While we fixate an object, our eyes are never stationary but constantly drifting, with miniature movements traditionally thought to be random and involuntary. A new study shows that the orientation of such drift in humans is actually not random but is influenced by the task demands to improve performance.

Many real-world decisions in social contexts are made while observing a partner's actions. To study dynamic interactions during such decisions, we developed a setup where two agents seated face-to-face engage in game-theoretical tasks on a shared transparent touchscreen display ('transparent games'). We compared human and macaque pairs in a transpa...

Dorsal pulvinar has been implicated in visuospatial attentional and perceptual confidence processing. Perturbations of the dorsal pulvinar also induce an overt spatial saccade bias during free choices. But it remains unclear whether the dorsal pulvinar inactivation during an oculomotor target selection based on a perceptual decision will lead to pe...

Standard neuroeconomics theories state that the value of different classes of stimuli, for instance the hedonic value of food versus music, is transformed to a common reference scale that is independent of their sensory properties. However, adaptive behaviour in a multimodal and dynamic environment requires that our brain also encodes information a...

We have developed a novel continuous perceptual report task that allows assessment of perception and perceptual confidence in real-time.

When comparing themselves with others, people often perceive their own actions and behaviour favourably. This phenomenon is often categorised as a bias of attribution, with favourable self-evaluation resulting from differing explanations of one's own behaviour and that of others. However, studies on availability biases offer an alternative explanat...

Visual perceptual learning is traditionally thought to arise in visual cortex. However, typical perceptual learning tasks also involve systematic mapping of visual information onto motor actions. Because the motor system contains both effector-specific and effector-unspecific representations, the question arises whether visual perceptual learning i...

Causal perturbation studies suggest that the primate dorsal pulvinar (dPul) plays a crucial role in target selection and saccade planning, but many of its basic visuomotor neuronal properties are unclear. While some functional aspects of dPul and interconnected frontoparietal areas - such as ipsilesional choice bias after inactivation - are similar...

The thalamic pulvinar and the lateral intraparietal area (LIP) share reciprocal anatomical connections and are part of an extensive cortical and subcortical network involved in spatial attention and oculomotor processing. The goal of this study was to compare the effective connectivity of dorsal pulvinar (dPul) and LIP and to probe the dependency o...

Brain perturbation studies allow detailed causal inferences of behavioral and neural processes. Because the combination of brain perturbation methods and neural measurement techniques is inherently challenging, research in humans has predominantly focused on non-invasive, indirect brain perturbations, or neurological lesion studies. Non-human prima...

Adaptive agents must act in intrinsically uncertain environments with complex latent structure. Here, we elaborate a model of visual foraging-in a hierarchical context-wherein agents infer a higher-order visual pattern (a "scene") by sequentially sampling ambiguous cues. Inspired by previous models of scene construction-that cast perception and act...

The thalamic pulvinar and the lateral intraparietal area (LIP) share reciprocal anatomical connections and are part of an extensive cortical and subcortical network involved in spatial attention and oculomotor processing. The goal of this study was to compare the effective connectivity of dorsal pulvinar (dPul) and LIP and to probe the dependency o...

Brain perturbation studies allow detailed causal inferences of behavioral and neural processes. Because the combination of brain perturbation methods and neural measurement techniques is inherently challenging, research in humans has predominantly focused on non-invasive, indirect brain perturbations, or neurological lesions. Non-human primates hav...

Following the expanding use and applications of virtual reality in everyday life, realistic virtual stimuli are of increasing interest in cognitive studies. They allow for control of features such as gaze, expression, appearance, and movement, which may help to overcome limitations of using photographs or video recordings to study social responses....

14 Adaptive agents must act in intrinsically uncertain environments with complex latent structure. Here, 15 we elaborate a model of visual foraging-in a hierarchical context-wherein agents infer a higher-order 16 visual pattern (a 'scene') by sequentially sampling ambiguous cues. Inspired by previous models of scene 17 construction-that cast percep...

Interactions of group-living primates range from cooperation to competition. Many corresponding real-world decisions critically depend on observing partner’s actions. In classical game theory studies, however, agents act without knowing the partner’s choices. To overcome these limitations, we developed a setup where two agents engage face-to-face i...

Nonhuman primate neuroimaging is on the cusp of a transformation, much in the same way its human counterpart was in 2010, when the Human Connectome Project was launched to accelerate progress. Inspired by an open data-sharing initiative, the global community recently met and, in this article, breaks through obstacles to define its ambitions.

Estimating invested effort is a core dimension for evaluating own and others’ actions, and views on the relationship between effort and rewards are deeply ingrained in various societal attitudes. Internal representations of effort, however, are inherently noisy, e.g. due to the variability of sensorimotor and visceral responses to physical exertion...

Real-world agents, humans as well as animals, observe each other during interactions and choose their own actions taking the partners’ ongoing behaviour into account. Yet, classical game theory assumes that players act either strictly sequentially or strictly simultaneously without knowing each other’s current choices. To account for action visibil...

Sensorimotor cortical areas contain eye position information thought to ensure perceptual stability across saccades and underlie spatial transformations supporting goal-directed actions. One pathway by which eye position signals could be relayed to and across cortical areas is via the dorsal pulvinar. Several studies demonstrated saccade-related ac...

Patients with Parkinson's disease (PD) frequently suffer from visual misperceptions and hallucinations, which are difficult to objectify and quantify. We aimed to develop an image recognition task to objectify misperceptions and to assess performance fluctuations in PD patients with and without self-reported hallucinations. Thirty-two non-demented...

Following the expanding use and applications of virtual reality in every-day life, dynamic virtual stimuli are of increasing interest in cognitive studies. They allow for control of features such as gaze, expression and movement, which may help to overcome limitations of using either static or poorly controlled real stimuli. In using virtual stimul...

Most sensorimotor cortical areas contain eye position information thought to ensure perceptual stability across saccades and underlie spatial transformations supporting goal-directed actions. One pathway by which eye position signals could be relayed to and across cortical areas is via the dorsal pulvinar. Several studies demonstrated saccade-relat...

A Transparent game is a game-theoretic setting that takes action visibility into account. In each round, depending on the relative timing of their actions, players have a certain probability to see their partner’s choice before making their own decision. This probability is determined by the level of transparency. At the two extremes, a game with z...

A Transparent game is a game-theoretic setting that takes action visibility into account. In each round, depending on the relative timing of their actions, players have a certain probability to see their partner's choice before making their own decision. This probability is determined by the level of transparency. At the two extremes, a game with z...

For humans and for non-human primates heart rate is a reliable indicator of an individual’s current physiological state, with applications ranging from health checks to experimental studies of cognitive and emotional state. In humans, changes in the optical properties of the skin tissue correlated with cardiac cycles (imaging photoplethysmogram, iP...

Effort constitutes a major part of cost-benefit calculations underlying decision making. Therefore, estimating the effort someone has spent on a task is a core dimension for evaluating own and others’ actions. It has been previously shown that self-judgments of effort are influenced by the magnitude of obtained rewards. It is unclear, however, whet...

For humans and for non-human primates heart rate is a reliable indicator of an individual’s current physiological state, with applications ranging from health checks to experimental studies of cognitive and emotional state. In humans, changes in the optical properties of the skin tissue correlated with cardiac cycles (imaging photoplethysmogram, iP...

Comparison of imaging photoplethysmogram with a contact photoplethysmogram. (A) Imaging photoplethysmogram (iPPG) aligns with contact photoplethysmogram (PPG) recorded using pulse oximeter P-OX100L (Medlab GmbH, Stutensee; documented accuracy ± 1%) for Session 8 (in addition to the basic reference pulse oximetry, which was the same as for other ses...

Despite many years of intense research, there is no strong consensus about the role of the lateral intraparietal area (LIP) in decision making. One view of LIP function is that it guides spatial attention, providing a "saliency map" of the external world. If this were the case, it would contribute to target selection regardless of which action woul...

The present study aimed at investigating whether associated motivational salience causes preferential processing of inherently neutral faces similar to emotional expressions by means of event-related brain potentials (ERPs) and changes of the pupil size. To this aim, neutral faces were implicitly associated with monetary outcome, while participants...

Real-world agents, such as humans, animals and robots, observe each other during interactions and choose their own actions taking the partners' ongoing behaviour into account. Yet, classical game theory assumes that players act either strictly sequentially or strictly simultaneously (without knowing the choices of each other). To account for action...

Humans and other animals constantly evaluate their decisions in order to learn and behave adaptively. Experimentally, such evaluation processes are accessed using metacognitive reports made after decisions, typically using verbally formulated confidence scales. When subjects report high confidence, it reflects a high certainty of being correct, but...

Humans and other animals constantly evaluate their decisions in order to learn and behave adaptively. Experimentally, such evaluation processes are accessed using metacognitive reports made after decisions, typically using verbally formulated confidence scales. When subjects report high confidence, it reflects a high certainty of being correct, but...

For humans and for non-human primates heart rate is a reliable indicator of an individual’s current physiological state, with applications ranging from health checks to experimental studies of cognitive and emotional state. In humans, changes in the optical properties of the skin tissue correlated with cardiac cycles (imaging photoplethysmogram, iP...

The present study aimed at investigating whether associated motivational salience causes preferential processing of inherently neutral faces similar to emotional expressions by means of event-related brain potentials (ERPs) and changes of the pupil size. To this aim, neutral faces were implicitly associated with monetary outcome, while participants...

Expansion of the dorsal pulvinar in humans and its anatomical connectivity suggests its involvement in higher-order cognitive and visuomotor functions. We investigated visuomotor performance in a 31 year old patient with a lesion centered on the medial portion of the dorsal pulvinar (left > right) due to an atypical Sarcoidosis manifestation. Unlik...

Visual processing depends on rapid parsing of global features followed by analysis of fine detail. A new study suggests that this transformation is enabled by a cycle of saccades and fixational drifts, which reformat visual input to match the spatiotemporal sensitivity of fast and slow neuronal pathways.

Significance statement: Despite a recent surge of interest, the core function of the pulvinar, the largest thalamic complex in primates, remains elusive. This understanding is crucial given the central role of the pulvinar in current theories of integrative brain functions supporting cognition and goal-directed behaviors, but electrophysiological...

Unlabelled: The posterior parietal cortex (PPC) has traditionally been considered important for awareness, spatial perception, and attention. However, recent findings provide evidence that the PPC also encodes information important for making decisions. These findings have initiated a running argument of whether the PPC is critically involved in d...

A method and system of compensating for a damaged brain node is disclosed. The damaged node is determined by techniques such as fMRI or neural recording. A healthy node that can compensate for the function of the damaged node is determined. A stimulating electrode is placed on at least one functioning node to bypass the activity from the damaged no...

Although neuronal responses in behaving monkeys are typically studied while the monkey fixates straight ahead, it is known that eye position modulates responses of visual neurons. The modulation has been found to enhance neuronal responses when the receptive field is placed in the straight-ahead position for neurons receiving input from the periphe...

Even in the most sensitive part of human retina, the fovea, perception is not uniform. To compensate for such non-uniformity, tiny fixational microsaccades direct the optimal foveal locus to relevant parts of the fixated scene, similarly to larger exploratory saccades but on a miniature scale.

The ability to selectively process visual inputs and to decide between multiple movement options in an adaptive manner is critical for survival. Such decisions are known to be influenced by factors such as reward expectation and visual saliency. The dorsal pulvinar connects to a multitude of cortical areas that are involved in visuospatial memory a...

Impairments of spatial awareness and decision making occur frequently as a consequence of parietal lesions. Here we used event-related functional MRI (fMRI) in monkeys to investigate rapid reorganization of spatial networks during reversible pharmacological inactivation of the lateral intraparietal area (LIP), which plays a role in the selection of...

The significance of the miniature eye movements that we make during visual fixation has been intensely debated for the last 80 years. Recent studies have revealed that these motions of the eyes fulfill an important functional role: helping to extract useful information from natural scenes.

Although it has long been routine to classify neurons in V1 of anesthetized animals into simple and complex categories, it has not been easy to apply the original criteria to alert animals because of the omnipresent eye movements. In our experiments, effects of eye movements were minimized by compensating for them and by data processing. Activating...

The majority of cells in monkey V1 have overlapping increment and decrement activating regions (ARs) and nonlinear response properties ("duplex" cells). We have recently shown that responses of these cells to sinusoidal luminance gratings are diverse and can not be predicted from receptive fields' spatial maps. Many of these cells have a significan...

Natural viewing in primates consists of abrupt saccades followed by slower movements. We recorded the activity of single V1 neurons in response to a stationary bar while monkeys performed a fixation task or made voluntary saccades of different sizes. The classical receptive fields (CRFs) were mapped with drifting and flashing bars while compensatin...

Do our cells in V1 respond differently when we look in different places? To answer this question, we have studied neuronal responses to moving bars in V1 of an alert monkey while it maintained different directions of gaze. The monkey was trained to fixate on an LED attached to the stimulus screen while the screen was placed in three positions: stra...

Area V1 is known for its neural cell density and intricate histology. Physiological recordings, however, often are not integrated into this complex anatomy. We have previously shown, in alert monkeys, that physiological properties of single cells reflect an alternating arrangement of anatomical layers. Here we report how orientation selectivity is...

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 retrospectiv...

Author Summary The expected outcome of voluntary actions profoundly shapes human decision making. For instance, expected monetary reward and punishment are powerful modulators of human behavior. Yet how these factors influence brain activity responsible for the preparation of such behavior is not fully understood. This is especially true for demand...

Contralateral hemispheric representation of sensory inputs (the right visual hemifield in the left hemisphere and vice versa) is a fundamental feature of primate sensorimotor organization, in particular the visuomotor system. However, many higher-order cognitive functions in humans show an asymmetric hemispheric lateralization--e.g., right brain sp...

Complex cells constitute the major fraction of primate V1 neurons. Predicting the responses of these cells in natural viewing conditions is a crucial step toward understanding the mechanisms by which visual information is encoded in the brain. Yet, computational studies of V1 have virtually neglected complex cells in favor of the relatively linear...

Although prolonged adaptation is a very useful experimental tool, its relevancy to normal vision, which consists of series of short fixational epochs, is not clear. Directly related to perception is short-term pattern adaptation where a stimulus is quickly followed by an identical one. Recently, strong adaptation effects have been demonstrated in b...