User:Itsashleyxu/sandbox

Deafness and Hard-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 repurpose 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, higher and more widespread activation in auditory cortex under somatosensory stimulation. However, speeded response for somatosensory stimuli is not found in deaf adults.

Blindness
Due to vision loss, the visual cortex in blind people will undergo cross-modal plasticity, and therefore other senses may have enhanced abilities. Or the opposite, the lack of visual input weakens the development of other sensory systems, could happen. One study suggests that the right posterior middle temporal gyrus and superior occipital gyrus reveal more activation in the blind than in the sighted people during a sound-moving detection task. Several studies support the latter idea and found weakened ability in audio distance evaluation, proprioceptive reproduction, threshold for visual bisection, and judging minimum audible angle.

Human echolocation
Human echolocation is a learned ability for humans to sense their environment from echoes. This ability is used by some blind people to navigate their environment and sense their surroundings in detail. Studies in 2010 and 2011 using functional magnetic resonance imaging techniques have shown that parts of the brain associated with visual processing are adapted for the new skill of echolocation. Studies with blind patients, for example, suggest that the click-echoes heard by these patients were processed by brain regions devoted to vision rather than audition.

Attention Deficits Hyperactivity Disorder
MRI studies of 1713 participants shows that both children and adults with attention deficits hyperactivity disorder (ADHD) have smaller volumes of nuclues accumbens, amygdala, caudate, hippocampus, putamen, overall cortical and intracranial volume, and have less surface area and cortical thickness, compared to people without ADHD.

Reviews of MRI studies on individuals with ADHD suggest that the long-term treatment of attention deficit hyperactivity disorder (ADHD) with stimulants, such as amphetamine or methylphenidate, decreases abnormalities in brain structure and function found in subjects with ADHD, and improves function in several parts of the brain, such as left ventrolateral prefrontal cortex (VLPFC), and superior temporal gyrus.