When collecting large amounts of neuroimaging data associated with psychiatric disorders, images must be acquired from multiple sites because of the limited capacity of a single site. However, site differences represent a barrier when acquiring multisite neuroimaging data. We utilized a traveling-subject dataset in conjunction with a multisite, multidisorder dataset to demonstrate that site differences are composed of biological sampling bias and engineering measurement bias. The effects on resting-state functional MRI connectivity based on pairwise correlations because of both bias types were greater than or equal to psychiatric disorder differences. Furthermore, our findings indicated that each site can sample only from a subpopulation of participants. This result suggests that it is essential to collect large amounts of neuroimaging data from as many sites as possible to appropriately estimate the distribution of the grand population. Finally, we developed a novel harmonization method that removed only the measurement bias by using a traveling-subject dataset and achieved the reduction of the measurement bias by 29% and improvement of the signal-to-noise ratios by 40%. Our results provide fundamental knowledge regarding site effects, which is important for future research using multisite, multidisorder resting-state functional MRI data.

No abstract

Pupil dilation and blinks provide complementary, mutually exclusive indices of information processing. Though each index is associated with cognitive load, the occurrence of a blink precludes the measurement of pupil diameter. These indices have generally been assessed in independent literatures. We examine the extent to which these measures are related on two cognitive tasks using a novel method that quantifies the proportion of trials on which blinks occur at each sample acquired during the trial. This measure allows cross-correlation of continuous pupil-dilation and blink waveforms. Results indicate that blinks occur during early sensory processing and following sustained information processing. Pupil dilation better reflects sustained information processing. Together these indices provide a rich picture of the time course of information processing, from early reactivity through sustained cognition, and after stimulus-related cognition ends.

Objective-Suicide rates are very high in old age, and the contribution of cognitive risk factors remains poorly understood. Suicide may be viewed as an outcome of an altered decision process. We hypothesized that impairment in a component of affective decision-making -reward/ punishment-based learning -is associated with attempted suicide in late-life depression. We expected that suicide attempters would discount past reward/punishment history, focusing excessively on the most recent rewards and punishments. Further, we hypothesized that this impairment could be dissociated from executive abilities such as forward planning.Method-We assessed reward/punishment-based learning using the Probabilistic Reversal Learning task in 65 individuals aged 60 and older: suicide attempters, suicide ideators, nonsuicidal depressed elderly, and non-depressed controls. We used a reinforcement learning computational model to decompose reward/punishment processing over time. The Stockings of Cambridge test served as a control measure of executive function.Results-Suicide attempters but not suicide ideators showed impaired probabilistic reversal learning compared to both non-suicidal depressed elderly and to non-depressed controls, after controlling for effects of education, global cognitive function, and substance use. Model-based analyses revealed that suicide attempters discounted previous history to a higher degree, compared to controls, basing their choice largely on reward/punishment received on the last trial. Groups did not differ in their performance on the Stockings of Cambridge.Conclusions-Older suicide attempters display impaired reward/punishment-based learning. We propose a hypothesis that older suicide attempters make overly present-focused decisions, ignoring past experiences. Modification of this 'myopia for the past' may have therapeutic potential.Please address correspondence to: Dr. Katalin Szanto, Western Psychiatric Institute and Clinic, 100 N Bellefield Ave, Pittsburgh, Pennsylvania 15213. Phone: 412-586-9601; szantok@upmc.edu. All authors report no competing interests. NIH Public Access Author ManuscriptAm J Psychiatry. Author manuscript; available in PMC 2011 January 13. Worldwide, suicide is more common in the elderly than in any other age group (1). Suicide attempts in late life are more lethal than in mid-life (2), with up to one-half ending in death in older men (3). Though cognitive decline is prevalent in old age and may contribute to the heightened suicide risk, little is known about the role of cognitive factors. Initial evidence links late-life suicidal behavior to poor performance on screening measures of cognitive control (4,5).Evidence from younger suicide attempters indicates impaired performance on tests of cognitive control (6-9) and poor problem-solving (10). To the extent that findings from younger adults generalize to late-life suicide, they suggest a deficit in cognitive abilities relevant to dealing with life's problems and making decisions. Yet, cognitive mechanisms that underpin...