Abstract
Deficits in sustained visual attention are common in various populations, such as older adults or individuals with traumatic brain injury, leading to measures of sustained attention being standard in neuropsychological batteries. However, many of these populations also have higher rates of primary visual function deficits, highlighting the need to determine the extent to which performance on sustained attention tasks is dependent on primary visual functions. This study investigated the impact of image contrast and resolution on an adapted version of the gradual-onset continuous performance task where participants discriminated between city and mountain images. Healthy, normal vision participants (N=36; mean age=20.8) completed two blocks of 600 trials of this discrimination task where images were either blurred or reduced in contrast to simulate low vision deficits. Each block tested six levels of image degradation (Blur filter radius: 0/5/10/15/25/40 pixels; Contrast rescaled intensity range: (1/0.164/0.128/0.092/0.056/0.020). For half of the subjects, scenes faded from one to the next every 800ms (dynamic condition) while the other half saw static scenes that stayed on until a response was made (static condition). Hierarchical regression models were fit to the data comparing models with separate slopes and intercepts to models with a shared slope parameter. For the contrast conditions, accuracy was found to decrease at a faster rate in the dynamic condition relative to the static condition where few errors were made across all six contrast levels (p=0.0016). However, for the blur conditions, accuracy was found to decrease at a similar rate regardless of how long stimuli were presented (p=0.1889). While reducing image contrast had little impact on performance for static presentations, these results demonstrate that under dynamic conditions more representative of real-world environments, changes in both image contrast and resolution lead to performance deficits that may be misinterpreted as attentional failures.