PLAD is a medically unrecognized disorder where one has learned a small amount of a different langauge, and has episodes of only being able to remember that language. However, due to the lack of fluency, the affected struggles to think.
Symptoms Include
An inability to remember the native language, or other fluently known languages, during the episodes
Unable to communicate with others or think properly during episodes
An urge to be alone during episodes
Often comorbid with anxiety disorders
The disorder can, in theory, be cured by fully learning the language(s) that one experiences PLAD with