Humans are experts at the rapid perception of the broad meaning of ‘gist’ of a scene (forest, beach, etc). Medical images are the ‘scenes’ processed by expert radiologists. We have found that trained radiologists can discriminate normal from abnormal mammograms after as little as a quarter of a second exposure to the image. We believe that this ability to detect a ‘global gist signal’ in the breast results from years of training and practice, tuning their visual system to specific types of images. Critically we show that they can detect the global gist signal in mammograms taken three years prior to the development of any visible signs of cancer.
A gist signal that is detectable in prior exams could be an imaging risk marker. Our goal is to understand the signal, its dynamics and neuronal underpinning and establish how it might be exploited as a perceptual ‘risk factor.’ One of the projects that we are working on now is developing and then using a training protocol for learning the gist of the abnormal in mammograms while recording brain activity of naïve observers with EEG during the learning process. This will allow us to assess changes in the event-related potentials (ERPs) of an observer over time, which provides insight into the learning processes taking place in the brain.
Dr Evans' areas of research include attention, visual cognition and memory, multimodal perception and translational interdisciplinary work.