Perceptual functions in prosopagnosia

Some patients with prosopagnosia may have an apperceptive basis to their recognition defect. Perceptual abnormalities have been reported in single cases or small series, but the causal link of such deficits to prosopagnosia is unclear. Our goal was to identify candidate perceptual processes that might contribute to prosopagnosia, by subjecting several prosopagnosic patients to a battery of functions that may be necessary for accurate facial perception. We tested seven prosopagnosic patients. Three had unilateral right occipitotemporal lesions, two had bilateral posterior occipitotemporal lesions, and one had right anterior-to-occipital temporal damage along with a small left temporal lesion. These lesions all included the fusiform face area, in contrast to one patient with bilateral anterior temporal lesions. Most patients had impaired performance on face-matching tests and difficulty with subcategory judgments for non-face objects. The most consistent deficits in patients with lesions involving the fusiform face area were impaired perception of spatial relations in dot patterns and reduced contrast sensitivity in the 4 to 8 cycles deg(-1) range. Patients with bilateral lesions were impaired in saturation discrimination. Luminance discrimination was normal in all but two patients, and spatial resolution was uniformly spared. Curvature and line-orientation discrimination were impaired in only one patient, who also had the most difficulty with more basic-level object recognition. We conclude that deficits in luminance, spatial resolution, curvature, line orientation, and contrast at low spatial frequencies are unlikely to contribute to apperceptive prosopagnosia. More relevant may be contrast sensitivity at higher spatial frequencies and the analysis of object spatial structure. Deficits in these functions may impair perception of subtle variations in object shape, and may be one mechanism by which the recognition defect in prosopagnosia can extend to other classes of object subcategorization.     

Describing suicidality: an investigation of qualitative SSF responses

Given the incidence and seriousness of suicidality in clinical practice, the need for new and better ways to assess suicide risk is clear. While there are many published assessment instruments in the literature, survey data suggest that these measure are not widely used. One possible explanation is that current quantitatively developed assessment instruments may fail to capture something essential about the suicidal patient's experience. The current exploratory study examined a range of open ended qualitative written responses made by suicidal outpatients to five assessment prompts from the Suicide Status Form (SSF)--psychological pain, press, perturbation, hopelessness, and self-hate. Two different samples of suicidal outpatients seeking treatment, including suicidal college students (n = 119) and active duty U.S. Air Force personnel (n = 33), provided a wide range of written responses to the five SSF prompts. A qualitative coding manual was developed through a step-by-step methodology; two naive coders were trained to use the coding system and were able to sort all the patients' written responses into the content categories with very high interrater reliability (Kappa > .80). Certain written qualitative responses of the patients were more frequent than others, both within and across the five SSF constructs. Among a range of specific exploratory findings, one general finding was that two thirds of the 636 obtained written responses could be reliably categorized under four major content headings: relational (22%), role responsibilities (20%), self (15%), and unpleasant internal states (10%). Theoretical, research, and clinical implications of the methodology and data are discussed.     

Stability in autobiographical memories

A total of 30 undergraduates recalled the same 20 autobiographical memories at two sessions separated by 2 weeks. At each session they dated their memories and rated them on 18 properties commonly studied in autobiographical memory experiments. Individuals showed moderate stability in their ratings on the 18 scales (r approximately .5), with consistency of dating being much higher (r = .96). There was more stability in the individuals' average rating on each scale (r approximately .8), even when the averages were calculated on different memories in the different sessions. The results are consistent with a constructive view of autobiographical memory, in which stable individual differences in cognitive style are important.     

No pause for a brief disruption: failures of visual awareness during ongoing events

Past research has repeatedly documented the close relationship between visual attention and awareness. Most recently, research exploring change blindness, inattentional blindness, repetition blindness, and the attentional blink has converged on the conclusion that attention to one aspect of a scene or event may lead to a highly circumscribed awareness of only the specific information attended, while other information, even that which is spatially or temporally nearby can go completely unnoticed. In the present report, we extend these observations to the dynamic allocation of attention during a well-structured meaningful event. In two experiments, subjects viewed brief videos of simple events and were told to pay close attention to them. During the events, an unexpected disruption consisting of a brief low spatial frequency motion field occurred. Despite intensive questioning and opportunities for recognition, the majority of subjects reported no awareness of 200, 400, or 600 ms disruptions. In a second experiment, blank-screen disruptions were added, and these resulted in no increase in detection. We conclude that visual attention may result in far more transitory awareness of visual information than previously appreciated.     

Polling and public policy

This commentary distinguishes five reasons why one might want to conduct a survey concerning people's beliefs about death and the permissibility of harvesting organs: (1) simply to learn what people know and want; (2) to determine if current law and practice conform to the wishes of the population; (3) to determine the level of popular support for or opposition to policy changes; (4) to ascertain the causes and effects of popular beliefs and attitudes; and (5) to provide guidance in determining which law and practices are ethical. The commentary expresses qualms about how well surveys in general can perform with respect to the fifth objective, and it provides specific reasons to doubt whether this survey is informative from the perspective of a moral philosopher concerned with the nature of death and the contours of a permissible system of organ procurement.     

Impaired odor recognition memory in patients with hippocampal lesions

In humans, impaired recognition memory following lesions thought to be limited to the hippocampal region has been demonstrated for a wide variety of tasks. However, the importance of the human hippocampus for olfactory recognition memory has scarcely been explored. We evaluated the ability of memory-impaired patients with damage thought to be limited to the hippocampal region to recognize a list of odors. The patients were significantly impaired after a retention delay of 1 h. Olfactory sensitivity was intact. This finding is in agreement with earlier reports that rats with hippocampal lesions exhibited memory impairment on an odor delayed nonmatching to sample task (after 30 min and 1 h) and that patients with damage thought to be limited to the hippocampal region were impaired on an odor span memory task. Olfactory recognition memory, similar to recognition memory in other sensory modalities, depends on the integrity of the hippocampal region.     

Task requirements influence sensory integration during grasping in humans

The sensorimotor transformations necessary for generating appropriate motor commands depend on both current and previously acquired sensory information. To investigate the relative impact (or weighting) of visual and haptic information about object size during grasping movements, we let normal subjects perform a task in which, unbeknownst to the subjects, the object seen (visual object) and the object grasped (haptic object) were never the same physically. When the haptic object abruptly became larger or smaller than the visual object, subjects in the following trials automatically adapted their maximum grip aperture when reaching for the object. This adaptation was not dependent on conscious processes. We analyzed how visual and haptic information were weighted during the course of sensorimotor adaptation. The adaptation process was quicker and relied more on haptic information when the haptic objects increased in size than when they decreased in size. As such, sensory weighting seemed to be molded to avoid prehension error. We conclude from these results that the impact of a specific source of sensory information on the sensorimotor transformation is regulated to satisfy task requirements.     

Assessing the executive function deficits of patients with Parkinson's disease: utility of the Tower of London-Drexel

The aim of the study was to investigate the utility of the Tower of London-Drexel (TOLDX) in assessing the executive deficits associated with Parkinson's disease (PD). We sought to determine whether the TOLDX would differentiate between (a) patients with PD and healthy control participants (HCP), (b) demented and nondemented patients, and (c) depressed and nondepressed patients. A new TOLDX score, stimulus bound, was introduced to assess utilization behaviors. Furthermore, the convergent and divergent validity of the TOLDX was examined. The TOLDX total move, rule and time violation, and stimulus-bound scores of patients with PD significantly differed from the HCP. Demented and nondemented patients also differed significantly in their TOLDX performance, with the stimulus-bound score being the most significantly differentiating score. However, the depressed and nondepressed patients did not differ in their TOLDX performance. Support was found for the convergent and divergent validity of the TOLDX. The clinical and theoretical implications of the findings are discussed.     

The integration of continuous and discrete latent variable models: potential problems and promising opportunities

Structural equation mixture modeling (SEMM) integrates continuous and discrete latent variable models. Drawing on prior research on the relationships between continuous and discrete latent variable models, the authors identify 3 conditions that may lead to the estimation of spurious latent classes in SEMM: misspecification of the structural model, nonnormal continuous measures, and nonlinear relationships among observed and/or latent variables. When the objective of a SEMM analysis is the identification of latent classes, these conditions should be considered as alternative hypotheses and results should be interpreted cautiously. However, armed with greater knowledge about the estimation of SEMMs in practice, researchers can exploit the flexibility of the model to gain a fuller understanding of the phenomenon under study.     

Potential noradrenergic targets for cognitive enhancement in schizophrenia

Substantial evidence suggests that alterations in noradrenergic function contribute to the cognitive impairments of schizophrenia. Activation of post-junctional alpha 2a-adrenergic receptors in the prefrontal cortex by the alpha 2a-selective agonist guanfacine has demonstrated some preliminary benefit in subjects with schizophrenia treated with atypical antipsychotics. alpha 1-adrenergic receptor activity may be less important in mediating the cognitive impairments of schizophrenia. beta-adrenergic receptors may serve as another potential target for cognitive remediation in schizophrenia. However, the potential increase in memory consolidation in schizophrenia patients produced by beta-adrenergic agonists may be outweighed by the impairment in cognitive flexibility and executive functioning produced by beta-adrenergic agonists. Finally, norepinephrine reuptake inhibitors, such as atomoxetine, hold promise as potential cognitive enhancers in schizophrenia because of their ability to indirectly but selectively increase extracellular dopamine concentrations in the prefrontal cortex.