When a biological sentient being is uploaded into an electronic substrate, or an already uploaded entity is transferred to a radically different matrix there is a sense of dislocation, incongruity and unease. This so-called Substrate Shock is a not-uncommon psychological affliction amongst a significant fraction of baselines (and allegedly higher-rated intellects) upon changing to a new substrate. It is exacerbated by radical changes in perception, autonomic functioning, and others.
One of the most common forms are uploads who begin to feel 'hunger pains' regardless of the autonomic response offered by their environment. Others include 'pulse lack', 'respiration lack', and similar radical changes, especially in formerly life-supporting behaviors.
Most experts suggest returning appropriate sensation via virch or equivalent setting and slowly weaning the being off of the expected, prior 'normal' stimuli one at a time. A few suggest that the most effective treatment for such ailments is massive psychological support without altering the perception base of the affected being, helping them get through the crises as they occur via peer support, peer pressure, and other methods.
Note that not all beings suffer substrate shock, nor is it a solely meat-to-computronium problem. A significant fraction of computronium beings expressing individuality in a single format (rather than on an open computronium field, be this single format a virch or real life) may suffer similar patterns of panic response of similar pattern. Those virtual entities which chose to be downloaded into meat bodies, a process known as incarnation or embodiment, sometimes have severe substrate shock symptoms as well.
Common preparatory exercises designed to minimize substrate shock include virches preprogrammed with the sensorium the being will experience in the newer form.
Note that early forms of substrate shock were known to be fatal amongst early uploads and downloads, but all but the most primitive technological settings have appropriate techniques available to ease the suffering of such beings.
Additionally, there are some sophonts who consider Substrate Shock to be directly related to Translation Metamorphosis, while others dispute this. Both approaches have had significant successes in treatments over time.