Calibration of a color monitor for visual psychophysics

It has become common for stimuli used in visual psychophysical experiments to be presented on high-resolution color cathode-ray tubes (CRTs) such as the Barco CDCT 6551. These enable a flexibility of color, spatial-frequency content, temporal-frequency content, duration, size, and position that is not provided by most other media. CRTs are, however, not perfect; they suffer from the effects of temporal instability, spatial variability, lack of phosphor constancy, gun interdependence, and gun nonlinearity. This paper describes methods of assessing these aspects of monitor performance with respect to how significant each may be in psychometric terms. Although every application of CRT use in visual psychophysics is different, some general rules can be formulated to help ensure that unwanted effects are kept to a minimum. For the CRT used in this study (Barco CDCT 6551), a warm-up time of 30-45 min is necessary before chromatic and luminous stability ensues. Restriction of individual gun outputs to within 10%-90% of the possible range ensures that the effects of gun interdependence and lack of phosphor constancy are negligible. Calibration methods dealing with the linearization of gun output are also discussed.     

The social risk hypothesis of depressed mood: evolutionary, psychosocial, and neurobiological perspectives

The authors hypothesize that depressed states evolved to minimize risk in social interactions in which individuals perceive that the ratio of their social value to others, and their social burden on others, is at a critically low level. When this ratio reaches a point where social value and social burden are approaching equivalence, the individual is in danger of exclusion from social contexts that, over the course of evolution, have been critical to fitness. Many features of depressed states can be understood in relation to mechanisms that reduce social risk in such circumstances, including (a) hyper-sensitivity to signals of social threat from others, (b) sending signals to others that reduce social risks, and (c) inhibiting risk-seeking (e.g., confident, acquisitive) behaviors. These features are discussed in terms of psychosocial and neurobiological research on depressive phenomena.     

Co-localisation of abnormal brain structure and function in specific language impairment

We assessed the relationship between brain structure and function in 10 individuals with specific language impairment (SLI), compared to six unaffected siblings, and 16 unrelated control participants with typical language. Voxel-based morphometry indicated that grey matter in the SLI group, relative to controls, was increased in the left inferior frontal cortex and decreased in the right caudate nucleus and superior temporal cortex bilaterally. The unaffected siblings also showed reduced grey matter in the caudate nucleus relative to controls. In an auditory covert naming task, the SLI group showed reduced activation in the left inferior frontal cortex, right putamen, and in the superior temporal cortex bilaterally. Despite spatially coincident structural and functional abnormalities in frontal and temporal areas, the relationships between structure and function in these regions were different. These findings suggest multiple structural and functional abnormalities in SLI that are differently associated with receptive and expressive language processing.     

The Impact of Right Temporal Lobe Epilepsy On Nonverbal Memory: Meta-regression of Stimulus- and Task-related Moderators

Neuropsychology Review - Nonverbal memory tests have great potential value for detecting the impact of lateralized pathology and predicting the risk of memory loss following right temporal lobe...     

Masking by uniform field flicker: some practical problems

The technique of uniform field flicker (UFF) masking has frequently been used to address issues concerning the relative performance of sustained and transient neural channels in the human visual system. Unfortunately there has been an artifact in the implementation of this method in most published experiments which has meant that the contrast of the target has been flickered in synchrony with the mean luminance. A study is reported in which the artifact was corrected and the effects of UFF masking on the contrast sensitivity function then examined. With this correction, masking was still restricted to low spatial frequencies but it was much weaker than reported originally. It is argued that the original evidence suggesting that UFF masking can be used to examine the functioning of transient and sustained channels has not been interpreted correctly and that the basis for such a claim is weak.     

Failures of cognitive control or attention? The case of stop-signal deficits in schizophrenia

We used Bayesian cognitive modelling to identify the underlying causes of apparent inhibitory deficits in the stop-signal paradigm. The analysis was applied to stop-signal data reported by Badcock et al. (Psychological Medicine 32: 87-297, 2002) and Hughes et al. (Biological Psychology 89: 220-231, 2012), where schizophrenia patients and control participants made rapid choice responses, but on some trials were signalled to stop their ongoing response. Previous research has assumed an inhibitory deficit in schizophrenia, because estimates of the mean time taken to react to the stop signal are longer in patients than controls. We showed that these longer estimates are partly due to failing to react to the stop signal (“trigger failures”) and partly due to a slower initiation of inhibition, implicating a failure of attention rather than a deficit in the inhibitory process itself. Correlations between the probability of trigger failures and event-related potentials reported by Hughes et al. are interpreted as supporting the attentional account of inhibitory deficits. Our results, and those of Matzke et al. (2016), who report that controls also display a substantial although lower trigger-failure rate, indicate that attentional factors need to be taken into account when interpreting results from the stop-signal paradigm.     

Training and the attentional blink: Limits overcome or expectations raised?

The attentional blink (AB) refers to a deficit in reporting the second of two sequentially presented targets when they are separated by less than 500 ms. Two decades of research has suggested that the AB is a robust phenomenon that is likely attributable to a fundamental limit in sequential object processing. This assumption, however, has recently been undermined by a demonstration that the AB can be eliminated after only a few hundred training trials (Choi, Chang, Shibata, Sasaki, & Watanabe in Proceedings of the National Academy of Sciences 109:12242–12247, 2012). In the present work, we examined whether this training benefited performance directly, by eliminating processing limitations as claimed, or indirectly, by creating expectations about when targets would appear. Consistent with the latter option, when temporal expectations were reduced, training-related improvements declined significantly. This suggests that whereas training may ameliorate the AB indirectly, the processing limits evidenced in the AB cannot be directly eliminated by brief exposure to the task.     

Development and Evaluation of a Telephone Communication Protocol for the Delivery of Personalized Melanoma Genomic Risk to the General Population

Communicating personalized genomic risk results for common diseases to the general population as a form of tailored prevention is novel and may require alternative genetic counseling service delivery models. We describe the development and evaluation of a communication protocol for disclosing melanoma genomic risk information to the asymptomatic general population and assess participants’ satisfaction and acceptability. Participants (n?=?117) were aged 22–69 years, living in New South Wales, Australia and unselected for family history. They provided a saliva sample and had genomic testing for melanoma for low to moderate penetrant melanoma susceptibility variants in 21 genes. Participants could choose to receive their results from a genetic counselor via telephone, followed by a mailed booklet or to receive their risk result via mailed booklet only with a follow-up call for those at high risk. A follow-up questionnaire was completed by 85% of participants 3-months later. Most participants (80%) elected to receive their result via telephone. Participants were highly satisfied with the delivery of results (mean 3.4 out of 4, standard deviation 0.5), and this did not differ by delivery mode, risk category, age or sex. On follow-up, 75% accurately recalled their risk category, 6% indicated a preference for a different delivery mode, either electronic or face-to-face. The process of disclosing genomic risk results to the general population over the telephone with accompanying written material was feasible and acceptable, and may be useful for communicating polygenic risk for common diseases in the context of increasing demands for genomic testing.