Fitness and exercise Aerobic exercise increases the production of neurotrophic factors (compounds that promote growth or survival of neurons), such as brain-derived neurotrophic factor (BDNF), insulin-like growth factor 1 (IGF-1), and vascular endothelial growth factor (VEGF). Exercise-induced effects on the hippocampus are associated with measurable improvements in spatial memory. Consistent aerobic exercise over a period of several months induces marked clinically significant improvements in executive function (i.e., the "cognitive control" of behavior) and increased gray matter volume in multiple brain regions, particularly those that give rise to cognitive control. The brain structures that show the greatest improvements in gray matter volume in response to aerobic exercise are the prefrontal cortex and hippocampus; moderate improvements are seen in the anterior cingulate cortex, parietal cortex, cerebellum, caudate nucleus, and nucleus accumbens. Higher physical fitness scores (measured by VO2 max) are associated with better executive function, faster processing speed, and greater volume of the hippocampus, caudate nucleus, and nucleus accumbens. Deafness and loss of hearing Due to hearing loss, the auditory cortex and other association areas of the brain in deaf and/or hard of hearing people undergo compensatory plasticity. The auditory cortex is usually reserved for processing auditory information in hearing people now is redirected to serve other functions, especially for vision and somatosensation. Deaf individuals have enhanced peripheral visual attention, better motion change but not color change detection ability in visual tasks, more effective visual search, and faster response time for visual targets compared to hearing individuals. Altered visual processing in deaf people is often found to be associated with the repurposing of other brain areas including primary auditory cortex, posterior parietal association cortex (PPAC), and anterior cingulate cortex (ACC). A review by Bavelier et al. (2006) summarizes many aspects on the topic of visual ability comparison between deaf and hearing individuals. Brain areas that serve a function in auditory processing repurpose to process somatosensory information in congenitally deaf people. They have higher sensitivity in detecting frequency change in vibration above threshold and higher and more widespread activation in auditory cortex under somatosensory stimulation. However, speeded response for somatosensory stimuli is not found in deaf adults. Cochlear implant Neuroplasticity is involved in the development of sensory function. The brain is born immature and then adapts to sensory inputs after birth. In the auditory system, congenital hearing loss, a rather frequent inborn condition affecting 1 of 1000 newborns, has been shown to affect