Why are older people generally less astute drivers? To answer this, Professor Duje Tadin and others at the University of Rochester conducted research at the Harvard Medical School that was published in the Journal of Neuroscience. They discovered using transcranial magnetic stimulation (TMS) that the middle temporal visual area (the MT) is responsible for suppressing irrelevant background motion in order to focus more on important motion of smaller foreground objects. Tadin and the team placed magnetic coils at the back of subject’s heads and inhibited the functioning of the MT temporarily by stimulating it for 15 minutes with electrical signals. During this time, they tested how well subjects could identify larger and smaller objects’ motions. They better identified large, background objects’ motions, indicating that a less active or functionally inhibited MT might cause better perception of background motion for older people.
How do they know this? It was previously found that elderly people and schizophrenic or depressed people better perceive background motion. This is due to the brain’s limited power and resources; when more focus is spent on a certain task, there is inevitably less focus on another task using the same resources. Thus, this finding can be useful diagnostically in suggesting or confirming a person’s conditions of schizophrenia or depression, although it seems limited in practical usefulness related to the elderly in general (besides knowledge of the neurobiological reason behind slower driving with age). Hopefully its usefulness in diagnosing such afflictions can also lead to better understanding and treatment of the problems associated with schizophrenia and depression.
