It is usually diagnosed by a neurologist. There are several types of pseudobulbar affect: motor, vocal, emotional, and functional. Motor pseudobulbar affect results from problems with the brain's motor center, such as stroke or tumor. Vocal pseudobulbar affect occurs when there is a problem with language areas of the brain, so communication is impaired. Emotional pseudobulbar affect arises when there is a problem with feelings toward others, so social interactions are difficult. Functional pseudobulbar affect refers to the abnormal behavior caused by other medical conditions, such as depression or dementia. Nervous laughter is uncontrollable bursts of giggles triggered by thoughts or emotions. It often follows an episode of crying. People who suffer from this condition believe they have shown sensitivity to something funny but can't stop laughing anyway. In fact, nervous laughter is a very common habit among people who try not to show any sign of weakness. In most cases, nervous laughter does not mean that you are showing signs of mental illness. It is simply a natural reaction to certain situations.