High refresh rate display for natural monocular viewing in AOSLO psychophysics experiments.

By combining an external display operating at 360 frames per second with an Adaptive Optics Scanning Laser Ophthalmoscope (AOSLO) for human foveal imaging, we demonstrate color stimulus delivery at high spatial and temporal resolution in AOSLO psychophysics experiments. A custom pupil relay enables viewing of the stimulus through a 3-mm effective pupil diameter and provides refractive error correction from -8 to +4 diopters. Performance of the assembled and aligned pupil relay was validated by measuring the wavefront error across the field of view and correction range, and the as-built Strehl ratio was 0.64 or better. High-acuity stimuli were rendered on the external display and imaged through the pupil relay to demonstrate that spatial frequencies up to 54 cycles per degree, corresponding to 20/11 visual acuity, are resolved. The completed external display was then used to render fixation markers across the field of view of the monitor, and a continuous retinal montage spanning 9.4 by 5.4 degrees of visual angle was acquired with the AOSLO. We conducted eye-tracking experiments during free-viewing and high-acuity tasks with polychromatic images presented on the external display. Sub-arcminute eye position uncertainty was achieved, enabling precise localization of the line of sight on the monitor while simultaneously imaging the fine structure of the human central fovea. This high refresh rate display overcomes the temporal, spectral, and field of view limitations of AOSLO-based stimulus presentation, enabling natural monocular viewing of stimuli in psychophysics experiments conducted with AOSLO.

Threat bias and resting state functional connectivity of the amygdala and bed nucleus stria terminalis.

BACKGROUND: Previous research has distinguished the activations of the amygdala and bed nucleus of stria terminalis (BNST) during threat-related contingencies. However, how intrinsic connectivities of the amygdala and BNST relate to threat bias remains unclear. Here, we investigated how resting state functional connectivity (rsFC) of the amygdala and BNST in healthy controls (HC) and patients with anxiety-related disorders (PAD) associate with threat bias in a dot-probe task. METHODS: Imaging and behavioral data of 30 PAD and 83 HC were obtained from the Nathan Kline Institute - Rockland sample and processed according to published routines. All imaging results were evaluated at voxel p < 0.001 and cluster p < 0.05, FWE corrected in SPM. RESULTS: PAD and HC did not show differences in whole brain rsFC with either the amygdala or BNST. In linear regressions threat bias was positively correlated with amygdala-thalamus/anterior cingulate cortex (ACC) rsFC in HC but not PAD, and with BNST-caudate rsFC in PAD but not HC. Slope tests confirmed group differences in the correlations between threat bias and amygdala-thalamus/ACC as well as BNST-caudate rsFC. LIMITATIONS: As only half of the patients included were diagnosed with comorbid anxiety, the current findings need to be considered with the clinical heterogeneity and require replication in populations specifically with anxiety disorders. CONCLUSIONS: Together, these results suggest amygdala and BNST connectivities as new neural markers of anxiety disorders. Whereas amygdala-thalamus/ACC rsFC support adaptive regulation of threat response in the HC, BNST-caudate rsFC may reflect maladaptive neural processes that are dominated by anticipatory anxiety.

Imaging the effects of age on proactive control in healthy adults.

Previous research has reported reduced efficiency in reactive inhibition, along with reduced brain activations, in older adults. The current study investigated age-related behavioral and neural changes in proactive inhibition, and whether age may influence the relationship between proactive and reactive inhibition. One-hundred-and-forty-nine adults (18 to 72 years) underwent fMRI while performing a stop signal task (SST). Proactive inhibition was defined by the sequential effect, the correlation between the estimated probability of stop signal - p(Stop) - and go trial reaction time (goRT). P(Stop) was estimated trial by trial with a Bayesian belief model; reactive inhibition was defined by the stop signal reaction time (SSRT). Behaviorally the magnitude of sequential effect was not correlated with age, replicating earlier reports of spared proactive control in older adults. Age was associated with greater activations to p(Stop) in the lateral prefrontal cortex (PFC), paracentral lobule, superior parietal lobule, and cerebellum, and activations to goRT in the inferior occipital gyrus (IOG). Granger Causality analysis demonstrated that the PFC Granger caused IOG, with the PFC-IOG connectivity significantly correlated with p(Stop) in older but not younger adults. These findings suggest that the PFC and IOG activations and PFC-IOG connectivity may compensate for proactive control during aging. In contrast, while the activations of the ventromedial prefrontal cortex and caudate head to p(Stop) were negatively correlated with SSRT, relating proactive to reactive control, these activities did not vary with age. These findings highlighted distinct neural processes underlying proactive inhibition and limited neural plasticity to support cognitive control in the aging brain.