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Mnemonic but not contextual feedback signals defy dedifferentiation in the aging early visual cortex
(2024)
Perception is an intricate interplay between feedforward visual input and internally generated feedback signals that comprise concurrent contextual and time-distant mnemonic (episodic and semantic) information. Yet, an unresolved question is how the composition of feedback signals changes across the lifespan and to what extent feedback signals undergo age-related dedifferentiation, that is, a decline in neural specificity. Previous research on this topic has focused on feedforward perceptual representation and episodic memory reinstatement, suggesting reduced fidelity of neural representations at the item and category levels. In this fMRI study, we combined an occlusion paradigm that filters feedforward input to the visual cortex and multivariate analysis techniques to investigate the information content in cortical feedback, focusing on age-related differences in its composition. We further asked to what extent differentiation in feedback signals (in the occluded region) is correlated to differentiation in feedforward signals. Comparing younger (18–30 years) and older female and male adults (65–75 years), we found that contextual but not mnemonic feedback was prone to age-related dedifferentiation. Semantic feedback signals were even better differentiated in older adults, highlighting the growing importance of generalized knowledge across ages. We also found that differentiation in feedforward signals was correlated with differentiation in episodic but not semantic feedback signals. Our results provide evidence for age-related adjustments in the composition of feedback signals and underscore the importance of examining dedifferentiation in aging for both feedforward and feedback processing.
Background: Despite increasing calls for patient and public involvement in health‐care quality improvement, the question of how patient evaluations can contribute to physician learning and performance assessment has received scant attention.
Objective: The objective of this study was to explore, amid calls for patient involvement in quality assurance, patients' perspectives on their role in the evaluation of physician performance and to support physicians’ learning and decision making on professional competence.
Design: A qualitative study based on semi‐structured interviews.
Setting and Participants: The study took place in a secondary care setting in the Netherlands. The authors selected 25 patients from two Dutch hospitals and through the Dutch Lung Foundation, using purposive sampling.
Methods: Data were analysed according to the principles of template analysis, based on an a priori coding framework developed from the literature about patient empowerment, feedback and performance assessment.
Results: The analysis unearthed three predominant patient perspectives: the proactive perspective, the restrained perspective and the outsider perspective. These perspectives differed in terms of perceived power dynamics within the doctor‐patient relationship, patients' perceived ability, and willingness to provide feedback and evaluate their physician's performance. Patients' perspectives thus affected the role patients envisaged for themselves in evaluating physician performance.
Discussion and conclusion: Although not all patients are equally suitable or willing to be involved, patients can play a role in evaluating physician performance and continuing training through formative approaches. To involve patients successfully, it is imperative to distinguish between different patient perspectives and empower patients by ensuring a safe environment for feedback.
The timing of feedback to early visual cortex in the perception of long-range apparent motion
(2008)
When 2 visual stimuli are presented one after another in different locations, they are often perceived as one, but moving object. Feedback from area human motion complex hMT/V5+ to V1 has been hypothesized to play an important role in this illusory perception of motion. We measured event-related responses to illusory motion stimuli of varying apparent motion (AM) content and retinal location using Electroencephalography. Detectable cortical stimulus processing started around 60-ms poststimulus in area V1. This component was insensitive to AM content and sequential stimulus presentation. Sensitivity to AM content was observed starting around 90 ms post the second stimulus of a sequence and most likely originated in area hMT/V5+. This AM sensitive response was insensitive to retinal stimulus position. The stimulus sequence related response started to be sensitive to retinal stimulus position at a longer latency of 110 ms. We interpret our findings as evidence for feedback from area hMT/V5+ or a related motion processing area to early visual cortices (V1, V2, V3).