Event-related potential evidence for a dual-locus model of global/local processing

We investigated the perceptual time course of global/local processing using event-related potentials (ERPs). Participants discriminated the global or local level of hierarchical letters of different sizes and densities. Participants were faster to discriminate the local level of large/sparse letters and the global level of small/dense letters. This was mirrored in early ERP components: The N1/N2 had smaller peak amplitudes when participants made discriminations at the level that took precedence. Only global discriminations for large/sparse letters led to amplitude enhancement of the later P3 component, suggesting that additional attention-demanding processes are involved in discriminating the global level of these stimuli. Our findings suggest a dual-locus time course for global/local processing: (a) Level precedence occurs early in visual processing; (b) extra processing is required at a later stage, but only for global discriminations of large, sparse, stimuli, which may require additional attentional resources for active grouping.     

Multisensory contributions to the perception of motion

The ability to process motion is crucial for coherent perception and action. While the majority of studies have focused on the unimodal factors that influence motion perception (see, for example, the other chapters in this Special Issue), some researchers have also investigated the extent to which information presented in one sensory modality can affect the perception of motion for stimuli presented in another modality. Although early studies often gave rise to mixed results, the development of increasingly sophisticated psychophysical paradigms are now enabling researchers to determine the spatiotemporal constraints on multisensory interactions in the perception of motion. Recent findings indicate that these interactions stand over-and-above the multisensory interactions documented previously for static stimuli, such as the oft-cited 'ventriloquism' effect. Neuroimaging and neuropsychological studies are also beginning to elucidate the network of neural structures responsible for the processing of motion information in the different sensory modalities, an important first step that will ultimately lead to the determination of the neural substrates underlying these multisensory contributions to motion perception.     

The ventriloquist in motion: illusory capture of dynamic information across sensory modalities

Integrating dynamic information across the senses is crucial to survival. However, most laboratory studies have only examined sensory integration for static events. Here we demonstrate that strong crossmodal integration can also occur for an emergent attribute of dynamic arrays, specifically the direction of apparent motion. The results of the present study show that the perceived direction of auditory apparent motion is strongly modulated by apparent motion in vision, and that both spatial and temporal factors play a significant role in this crossmodal effect. We also demonstrate that a split-brain patient who does not perceive visual apparent motion across the midline is immune to this audiovisual dynamic capture effect, highlighting the importance of motion being experienced in order for this new multisensory illusion to occur.     

Covert orienting in the split brain: Right hemisphere specialization for object-based attention

ABSTRACT

The present paper takes as its starting point Phil Bryden's long-standing interest in human attention and the role it can play in laterality effects. Past split-brain research has suggested that object-based attention is lateralized to the left hemisphere [e.g., Egly, R., Rafal, R. D., Driver, J., & Starreveld, Y. (1994). Covert orienting in the split brain reveals hemispheric specialization for object-based attention. Psychological Science, 5(6), 380–382]. The task used to isolate object-based attention in that previous work, however, has been found wanting [Vecera, S. P. (1994). Grouped locations and object-based attention: Comment on Egly, Driver, and Rafal (1994). Journal of Experimental Psychology: General, 123(3), 316–320]; and indeed, subsequent research with healthy participants using a different task has suggested that object-based attention is lateralized to the opposite right hemisphere (RH) [Valsangkar-Smyth, M. A., Donovan, C. L., Sinnett, S., Dawson, M. R., & Kingstone, A. (2004). Hemispheric performance in object-based attention. Psychonomic Bulletin & Review, 11(1), 84–91]. The present study tested the same split-brain as Egly, Rafal, et al. (1994) but used the object-based attention task introduced by Valsangkar-Smyth et al. (2004). The results confirm that object-based attention is lateralized to the RH. They also suggest that subcortical interhemispheric competition may occur and be dominated by the RH.     

The Medusa effect reveals levels of mind perception in pictures

Throughout our species history, humans have created pictures. The resulting picture record reveals an overwhelming preference for depicting things with minds. This preference suggests that pictures capture something of the mind that is significant to us, albeit at reduced potency. Here, we show that abstraction dims the perceived mind, even within the same picture. In a series of experiments, people were perceived as more real, and higher in both Agency (ability to do) and Experience (ability to feel), when they were presented as pictures than when they were presented as pictures of pictures. This pattern persisted across different tasks and even when comparators were matched for identity and image size. Viewers spontaneously discriminated between different levels of abstraction during eye tracking and were less willing to share money with a more abstracted person in a dictator game. Given that mind perception underpins moral judgement, our findings suggest that depicted persons will receive greater or lesser ethical consideration, depending on the level of abstraction.

Human history is awash with pictures. By 40,000 y ago, cave painting was already established (1). Today, humanity uploads billions of photos per day (2). This extraordinary temporal reach is matched by extraordinary geographical reach. Pictures abound on all continents and are produced by virtually all cultures (3, 4). Across this staggering abundance of images, a clear preference in subject matter emerges: things with minds. Cave paintings around the world depict humans, animals, and their interactions (1). Social media services host more images of people than of any other image category (5, 6). This preoccupation with minded subjects suggests that pictures capture something of the mind that is significant to us.In pictorial representations, some features of the depicted reality are lost, and others are preserved. For example, a photo of a tiger loses the scale and motion of the tiger but may preserve its spatial layout and coloration. In this study, we focus on one critical feature of reality that pictures preserve—the capacity to contain pictures. In the same way that reality contains pictures, pictures too may contain pictures. This feature is intriguing, as it introduces a recursive structure in which different levels of abstraction may be nested.Some terminology will be useful in distinguishing these levels of abstraction. We refer to the real world as Level 0 (L0 for short). Most of our visual experiences—including the people and objects in our surroundings—are L0. Pictures within this environment are designated as Level 1 (L1). Cave paintings, family photos, and television images are all examples of L1. Pictures within such pictures are Level 2 (L2). The program for your local art gallery is packed with L2 pictures. Fig. 1 summarizes this scheme.Open in a separate windowFig. 1.Levels of pictorial abstraction and transitions between them. The blue background indicates reality (L0), and the yellow background indicates pictorial representation (L1 and L2). L0 (Left) refers to the visual environment as seen in live viewing. L1 (Center) refers to a picture of the visual environment as seen in photographs. L2 (Right) refers to a picture of a picture as when one photograph contains another. Transition 1 ascends one level of abstraction, from L0 to L1. Transition 2 also ascends one level of abstraction, from L1 to L2. Critically, Transition 1 bridges reality and pictorial representation, whereas Transition 2 occurs within the domain of pictorial representation.The sheer prevalence of minded beings in pictures raises the question of how mind perception and pictorial abstraction interact. Some mental attributes do not survive projection into pictures. We do not expect portraits to strike up a conversation. Nevertheless, some embers of mind perception can be detected. For example, pictures of eyes can direct our attention (7); “being watched” by photographic eyes can enhance prosocial behavior (8). Such findings betray perception of a mind behind the depicted eyes. One possible interpretation is that pictures carry the same signal as reality but at reduced strength.To summarize, on the one hand, pictures allow recursive representation. A picture may contain another picture at a higher level of abstraction. On the other hand, increasing the level of abstraction may decrease the potency of the subject. A picture in the environment just does not have the same force as the environment itself. Combining these two observations suggests a novel hypothesis: L2 pictures should be less potent than L1 pictures. For pictures of people, this raises the prospect of graded mind perception for different levels of abstraction. The purpose of the current experiments is to test this possibility.Comparing degrees of mind perception requires a quantitative framework. There have been various proposals as to how mind perception can be quantified, including its dimensionality (9–11). Perhaps the most influential of these is the two-dimensional framework proposed by Gray, Gray, and Wegner (9). This framework emerged from a principal component analysis of mind perception data from a large-scale survey. The analysis identified a primary factor of Experience (ability to feel), pertaining to moral patiency and rights, and a secondary factor of Agency (ability to do), pertaining to moral agency and responsibility. Adopting this framework, we predicted that attributions of Experience and Agency should distinguish L1 and L2 depictions of people. If successive abstractions temper the perceived mind, observers should attribute lower Experience and Agency to people in L2 pictures compared with people in L1 pictures. In short, we predict that mind perception will differ between pictures and pictures of pictures, even though both are pictorial representations.     

Abnormal Intestinal Permeability Predicts Relapse in Inactive Crohn Disease

Background: Trials of maintenance therapy in quiescent Crohn disease are often underpowered and there is need for objective markers that predict relapse. Intestinal permeability (IP) has been identified as such a marker although it is unknown how this relates to proposed clinical and blood markers of relapse. We aimed to assess the predictive value of intestinal permeability together with clinical and blood markers in a group of patients with inactive Crohn disease. Methods: We assessed 50 patients with inactive Crohn disease. Inactive disease was defined as a Crohn disease activity index of less than 150. Intestinal permeability was measured by the urinary excretion of lactulose and rhamnose and data relating to postulated clinical and blood markers predictive of relapse were collected. Follow-up for one year assessed whether patients had relapsed or remained in remission. Results: Of the 18 patients with abnormal intestinal permeability, 10 remained in remission and 8 relapsed. Of the 32 with a normal result, 31 remained in remission and 1 relapsed. Patients with abnormal intestinal permeability are significantly more likely to relapse than those with a normal result (chi-square = 14.3; P = 0.0001; relative risk 18). Those that relapsed had shorter disease duration. Multiple regression analysis identifies IP to be an independent variable. Conclusions: Abnormal intestinal permeability in patients with inactive Crohn disease predicts relapse. This is superior to clinical and blood markers. It is likely that this is due to ongoing subclinical mucosal inflammation. This may be of use when designing clinical trials of maintenance therapy.     

Disulfiram implants in the treatment of alcoholism some mechanisms of action.

For nearly 20 years, disulfiram implanted subcutaneously, has been used in alcoholics who have failed to respond to other treatment. Significantly positive results have been reported in a large number of cases. Despite this extensive use, many questions remain as to how these effects are exerted. As the reaction to alcohol following disulfiram implantation occurs less frequently and in lower intensity than following oral ingestion, psychological mechanisms probably play a vital role. Based in part on out own recent series of cases, the following explanations are offered regarding the possible mechanisms of action: (1) high motivation to stop drinking is manifested by agreeing to the precedure and reinforced by the procedure; (2) palpable presence of hte drug in the site of implantation; (3) generally sufficient reactivity of the agent to indicate activity to the patient;(4) in obsessional patients there is a removal of the fear of resumption of drinking for an extended period of time. For the more sociopathic patients the implant appears to provide a more structured ego boundary to allow the patient to change.     

Global perception in simultanagnosia is not as simple as a game of connect-the-dots

Simultanagnosia is a neuropsychological disorder characterized by a restriction of visuospatial attention. In addition, patients are able to identify local elements of a scene, but not the global whole. This may be due to a failure to scan and assemble local elements into a global whole (i.e. connect-the-dots). We monitored the eye movements of a simultanagnosic patient while she identified local and global elements of hierarchical letters. Scanning each local element was not necessary, nor sufficient, for successful global level identification. Our results argue against a connect-the-dots strategy of global identification and suggest that residual global processing may be occurring.