In the early 1980s, neuroscientists such as Torsten Wiesel and David H. Hubel were discovering that different areas of the primate visual cortex were finely tuned to selective features, such as line orientation, luminance, color, movement, etc. These findings prompted the question of how these distinct features are connected into a unified whole. This question has been called the binding problem. For example, when you see a red ball roll by, cells sensitive to movement fire in the medial temporal cortex, while cells sensitive to color, shape and location fire in other areas. Despite all this distinct neuronal firing, you don't perceive the ball as separated by shape, movement and color perceptions; you experience an integrated experience with all these components occurring together. The question of how these elements are combined is the essence of the binding problem, a central focus of research into the late 1990s. A number of possible mechanisms were envisaged, including grandmother cells responding to specific conjunctions of features that uniquely identify a particular object; local cell assemblies onto which the pathways from different feature maps converge, perhaps with adjustable connections allowing flexible routing of signals; a serial scan of different spatial areas selected by an adjustable attention window, conjoining the features that each contains and excluding features from adjacent areas; detection of temporal contiguity – parts and properties whose onset, offset or motion coincide probably belong to the same object synchronised firing of cells responding to features of the same object, perhaps assisted by oscillatory neural activity. Treisman used failures of binding to shed light on its underlying mechanisms. Specifically, she found that left-brain-damaged patients have increasing illusory conjunctions and decreased performance in a spatially cued attention task, which suggests a link between attentional binding and the parietal lobes. Treisman also cited corroborating evidence from positron emission tomography and event-related potential studies which were consistent with the spatial attention account of feature integration.