Melasma Causes. Melasma is usually caused by the sun, hormones in birth control pills, hormone replacement therapy, medications and pregnancy. When Melasma is caused by pregnancy it is called chloasma. In some women, when the skin is exposed to sunlight, brown blotches of excess pigment form due to the interaction with hormones or chemicals. Melasma is believed to be hereditary and woman with darker skin tones tend to be more at risk for this disorder.
Some research suggests that the hippocampus may participate only in consolidation processes lasting a few years. The entorhinal cortex, on the other hand, gives evidence of temporally graded changes extending up to 20 years, suggesting that it is this region that participates in memory consolidation over decades. The entorhinal cortex is damaged in the early stages of Alzheimerâs disease.
Three brain structures the hippocampus, amygdala and prefrontal cortex help the brain determine what is stressful and how to respond. The hippocampus stores memories of events and responds to stress hormones in the blood. Many mental disorders, including depression, may cause it to shrink or weaken. In the dentate gyrus, part of the hippocampal formation, new neurons (brain cells) are produced throughout adult life. Repeated stress slows the production of new neurons in the dentate gyrus and may also cause neurons in the hippocampus to shrink.