Restricted Attentional Capacity within but Not between Sensory Modalities: An Individual Differences Approach

Background Most people show a remarkable deficit to report the second of two targets when presented in close temporal succession, reflecting an attentional blink (AB). An aspect of the AB that is often ignored is that there are large individual differences in the magnitude of the effect. Here we exploit these individual differences to address a long-standing question: does attention to a visual target come at a cost for attention to an auditory target (and vice versa)? More specifically, the goal of the current study was to investigate a) whether individuals with a large within-modality AB also show a large cross-modal AB, and b) whether individual differences in AB magnitude within different modalities correlate or are completely separate. Methodology/Principal Findings While minimizing differential task difficulty and chances for a task-switch to occur, a significant AB was observed when targets were both presented within the auditory or visual modality, and a positive correlation was found between individual within-modality AB magnitudes. However, neither a cross-modal AB nor a correlation between cross-modal and within-modality AB magnitudes was found. Conclusion/Significance The results provide strong evidence that a major source of attentional restriction must lie in modality-specific sensory systems rather than a central amodal system, effectively settling a long-standing debate. Individuals with a large within-modality AB may be especially committed or focused in their processing of the first target, and to some extent that tendency to focus could cross modalities, reflected in the within-modality correlation. However, what they are focusing (resource allocation, blocking of processing) is strictly within-modality as it only affects the second target on within-modality trials. The findings show that individual differences in AB magnitude can provide important information about the modular structure of human cognition

Properties of the peripersonal space in behaving humans

Humans are equipped with many systems to help protect us from bodily harm. One of them is the peripersonal space that tries to help us avoid collisions or minimize the impact of collisions with external objects. This small network in the brain monitors the spaces immediately surrounding individual body-parts such as the face, hands, torso, legs and engages defensive responses such as moving the body-part away from the direction of impact, or closing the eyes in the event that impact is expected on the face. The interesting thing is that the protective zones around the body parts of independent of each other, and the defensive responses they trigger are also specific to protecting that body part. This defensive mechanism was the focus of this thesis. Initially discovered in primates, research is now being conducted in humans to gain an understanding of it. In the first study of the thesis, we show that humans are not only capable of anticipating where they are to expect an approaching object to make contact, but they are also capable of extracting exactly when the contact is to occur. We show that anticipating physical contact from a moving object facilitates the activity of the PPS mechanism. That is, both the action of the peripersonal space network and the anticipation of touch together help us prepare and respond to an object that is likely to come in contact with us. In other studies we looked at the properties of the peripersonal space. When the speed of a looming object increases, the defensive PPS around the body-part also increases, so as to be able to trigger the defensive response effectively sooner. This result is directly in line with what was observed in the neuronal activity of monkeys. Neurons tended to respond sooner when the object approaching the monkey loomed faster. We also show that the peripersonal space network integrates information from multiple senses, such as vision and touch to form its responses. That is, when you are able to both see an object approach you and feel its initial touch you are likely to detect it sooner than if you only saw it or felt its touch. This thesis looked at the effect of our action capability on our ability to estimate the locations of approaching objects. We showed that the better your action capability, the better you are estimating the location of a looming object. We compared video game players with non-video game players in a virtual reality task where they had to prevent a looming ball from making contact with an object standing next to them. We then asked the participants to estimate the location of the ball when it changed colour. We found that video game players were not only more effective at stopping the ball, they were also more accurate at estimating the location of the ball. Non-video game players, were slower at stopping the ball and also consistently judged the ball to be closer to them than it actually was. We see that when we need to interact with a looming object, our ability to effectively interact with it determines our judgement of its location. The results of this thesis demonstrate the effects of the mechanisms that our brain is equipped with to maintain a safety margin around our body

Properties of the peripersonal space in behaving humans

Humans are equipped with many systems to help protect us from bodily harm. One of them is the peripersonal space that tries to help us avoid collisions or minimize the impact of collisions with external objects. This small network in the brain monitors the spaces immediately surrounding individual body-parts such as the face, hands, torso, legs and engages defensive responses such as moving the body-part away from the direction of impact, or closing the eyes in the event that impact is expected on the face. The interesting thing is that the protective zones around the body parts of independent of each other, and the defensive responses they trigger are also specific to protecting that body part. This defensive mechanism was the focus of this thesis. Initially discovered in primates, research is now being conducted in humans to gain an understanding of it. In the first study of the thesis, we show that humans are not only capable of anticipating where they are to expect an approaching object to make contact, but they are also capable of extracting exactly when the contact is to occur. We show that anticipating physical contact from a moving object facilitates the activity of the PPS mechanism. That is, both the action of the peripersonal space network and the anticipation of touch together help us prepare and respond to an object that is likely to come in contact with us. In other studies we looked at the properties of the peripersonal space. When the speed of a looming object increases, the defensive PPS around the body-part also increases, so as to be able to trigger the defensive response effectively sooner. This result is directly in line with what was observed in the neuronal activity of monkeys. Neurons tended to respond sooner when the object approaching the monkey loomed faster. We also show that the peripersonal space network integrates information from multiple senses, such as vision and touch to form its responses. That is, when you are able to both see an object approach you and feel its initial touch you are likely to detect it sooner than if you only saw it or felt its touch. This thesis looked at the effect of our action capability on our ability to estimate the locations of approaching objects. We showed that the better your action capability, the better you are estimating the location of a looming object. We compared video game players with non-video game players in a virtual reality task where they had to prevent a looming ball from making contact with an object standing next to them. We then asked the participants to estimate the location of the ball when it changed colour. We found that video game players were not only more effective at stopping the ball, they were also more accurate at estimating the location of the ball. Non-video game players, were slower at stopping the ball and also consistently judged the ball to be closer to them than it actually was. We see that when we need to interact with a looming object, our ability to effectively interact with it determines our judgement of its location. The results of this thesis demonstrate the effects of the mechanisms that our brain is equipped with to maintain a safety margin around our body

Polyarteritis Nodosa: an unusual case of paraneoplastic process in renal cell carcinoma

Polyarteritis Nodosa (PAN) is a small and medium vessel necrotizing vasculitis that can affect any system in the human body. Rarely, PAN can be the primary manifestation of an underlying malignancy. The association between malignancy and vasculitis is an ongoing topic of research. Our patient’s presentation suggests malignancy may be a trigger for acute onset vasculitis and therefore once a malignancy is identified, therapy should be targeted towards treating the malignancy rather than the vasculitis alone

Location estimation of approaching objects is modulated by the observer's inherent and momentary action capabilities

Action capability may be one of the factors that can influence our percept of the world. A distinction can be made between momentary action capability (action capability at that particular moment) and inherent action capability (representing a stable action capability). In the current study, we investigated whether there was a biasing effect of these two forms of action capability on visual perception of location. In a virtual reality room, subjects had to stop a moving ball from hitting a pillar. On some trials, the ball disappeared automatically during its motion. Subjects had to estimate the location of the ball's disappearance in these trials. We expected that if action is necessary but action capability (inherent or momentary) is limiting performance, the location of approaching objects with respect to the observer is underestimated. By judging the objects to be nearer than they really are, the need to select and execute the appropriate action increases, thereby facilitating quick action (Cole et al. in Psychol Sci 24(1):34-40, 2013. doi: 10.1177/0956797612446953 ). As a manipulation of inherent action capability in a virtual environment, two groups of participants (video game players vs. non-video game players) were entered into the study (high and low action capability). Momentary action capability was manipulated by using two difficulty levels in the experiment (Easy vs. Difficult). Results indicated that inherent and momentary action capabilities interacted together to influence online location judgments: Non-players underestimated locations when the task was Difficult. Taken together, our data suggest that both inherent and momentary action capabilities influence location judgments

Location estimation of approaching objects is modulated by the observer's inherent and momentary action capabilities

Action capability may be one of the factors that can influence our percept of the world. A distinction can be made between momentary action capability (action capability at that particular moment) and inherent action capability (representing a stable action capability). In the current study, we investigated whether there was a biasing effect of these two forms of action capability on visual perception of location. In a virtual reality room, subjects had to stop a moving ball from hitting a pillar. On some trials, the ball disappeared automatically during its motion. Subjects had to estimate the location of the ball's disappearance in these trials. We expected that if action is necessary but action capability (inherent or momentary) is limiting performance, the location of approaching objects with respect to the observer is underestimated. By judging the objects to be nearer than they really are, the need to select and execute the appropriate action increases, thereby facilitating quick action (Cole et al. in Psychol Sci 24(1):34-40, 2013. doi: 10.1177/0956797612446953 ). As a manipulation of inherent action capability in a virtual environment, two groups of participants (video game players vs. non-video game players) were entered into the study (high and low action capability). Momentary action capability was manipulated by using two difficulty levels in the experiment (Easy vs. Difficult). Results indicated that inherent and momentary action capabilities interacted together to influence online location judgments: Non-players underestimated locations when the task was Difficult. Taken together, our data suggest that both inherent and momentary action capabilities influence location judgments

Visuo-tactile interactions are dependent on the predictive value of the visual stimulus

In this study we aimed to explore the predictive link between visual stimuli moving towards the body and the tactile consequences that follow. More specifically, we tested if information derived from an approaching visual stimulus in the region directly surrounding the body (the peripersonal space) could be used to make judgments about the location and time of impending tactile contact. We used moving arm stimuli, displayed on a computer screen, which appeared to travel either towards the face (middle of the left/right cheek) or slightly a000354596900036way from the subject's face. This stimulus was followed by tactile stimulation of the left/right cheek. The time lag between the visual stimulus and tactile stimulation was also manipulated to simulate tactile contact at a time that was either consistent or inconsistent with the speed of the approaching hand. Reaction time information indicated that faster responses were produced when the arm moved towards the hemispace in which the tactile stimulation was delivered and was insensitive to whether the arm was moving towards the cheek or slightly away from the cheek. Furthermore, response times were fastest when the tactile stimulation arrived at the moment that was consistent with the speed of the moving arm. The effects disappeared when the arm appeared to be retracting from the subject's face. These results suggest the existence of a predictive mechanism that exploits the visual information derived from objects moving towards the body for making judgments about the time and location of impending tactile contact

Visuo-tactile interactions are dependent on the predictive value of the visual stimulus

In this study we aimed to explore the predictive link between visual stimuli moving towards the body and the tactile consequences that follow. More specifically, we tested if information derived from an approaching visual stimulus in the region directly surrounding the body (the peripersonal space) could be used to make judgments about the location and time of impending tactile contact. We used moving arm stimuli, displayed on a computer screen, which appeared to travel either towards the face (middle of the left/right cheek) or slightly a000354596900036way from the subject's face. This stimulus was followed by tactile stimulation of the left/right cheek. The time lag between the visual stimulus and tactile stimulation was also manipulated to simulate tactile contact at a time that was either consistent or inconsistent with the speed of the approaching hand. Reaction time information indicated that faster responses were produced when the arm moved towards the hemispace in which the tactile stimulation was delivered and was insensitive to whether the arm was moving towards the cheek or slightly away from the cheek. Furthermore, response times were fastest when the tactile stimulation arrived at the moment that was consistent with the speed of the moving arm. The effects disappeared when the arm appeared to be retracting from the subject's face. These results suggest the existence of a predictive mechanism that exploits the visual information derived from objects moving towards the body for making judgments about the time and location of impending tactile contact

Cryptococcemia in an HIV-negative patient with decompensated liver cirrhosis

Background: Cryptococcal infections have been mostly associated with immunocompromised individuals, 80–90% of whom have been HIV-positive patients. Increasingly, cryptococcal infections are being reported in cirrhotic patients who are HIV-negative. The underlying immunologic defects in cirrhotic patients seem to play an important role in predisposing them to cryptococcosis and affecting their morbidity and mortality. Case presentation: We present a case of disseminated cryptococcosis in an HIV-negative patient with underlying cirrhosis, who had rapid worsening of his hyponatremia with renal failure and was unable to recover, despite aggressive measures. Conclusion: Cryptococcus is a more common culprit of infections seen in cirrhotic patients than what it was previously known, and a high index of suspicion is required to diagnose these patients. Identification of poor prognostic factors, early diagnosis and intervention is crucial in the management of these patients

Auditory T2 accuracy.

<p>Mean percentage correct report of an auditory T2 given correct report of T1 as a function of lag when presented within (solid line) or between modalities (dotted line).</p