Mirror motion is the medical term for the representation of passively observed actions in the primate brain. This neuronal representation occurs via mirror neurons. Presumably, the mirror system plays a role in connections of imitation and empathy.
What are mirror movements?
Mirror neurons are neurons in the brain. They are activated during passive observation of an event, showing the same patterns of activity as if the observer were performing the observed activity himself. Mirror neurons are nerve cells in the brain. They are activated during passive observation of a process and show the same activity patterns as if the observer were performing the observed activity himself. In addition to action-related sounds, mirror neurons also show the same activity for observed motor activity that they would show if the observed action were actually performed. Since its initial description in 1992, medical science has assumed mirror neuronal involvement in behavioral patterns of imitation and empathy. The mirror system corresponds to Brodmann area 44 and was discovered by the Italian Giacomo Rizzolatti. Recognition of actions and imitation seem to be directly related to the area. Although the existence of mirror neurons in humans has now been confirmed, the purpose of the neurons has not yet been extensively clarified. In addition to mirror neurons, humans possess anti-mirror neurons, whose activity patterns differ during observation and self-execution of an action. In 2008, researchers observed mirror system brain activity that provides compelling evidence for action involvement of the motor and somatosensory cortex and related mirror system activation. This evidence is also known as mirror movement. Mirror movements are thus the acting out of passively observed movements within one’s mirror system.
Function and task
Humans possess the ability to mimic the intentions of others and understand them through mere observation. Research groups coordinated the ‘Mirror’ research project in the 2000s and investigated the organization of the mirror system, which shows strong involvement in human cognitive functions. The research group investigated the place of the motor cortex in imitated and passively observed actions. The involvement of the brain region was clarified by the 14C-deoxyglucose procedure, which provided a pictorial representation of all brain activity. The procedure is based on the fact that the relative rate of glucose consumed and energetic metabolism reflects the functional activity of brain regions, at least to some extent. The involvement of the mirror system in observed actions was observed much earlier for monkeys. Monkeys viewed humans grasping an object or co-performed the activity themselves. Both imitation and observation involved activation of the corresponding areas in motor and primary somatosensory cortex. Both regions are involved in the mirror system. Monkeys thus showed similar neurological activity patterns during observation and execution of an action. Thus, evidence for a representation of observed actions in the motor cortex in monkeys was considered secure. The research group of the Mirror project assumed a storage of the movement details in the form of the neurological representation within the mirror system. Mirror movement appears to allow monkeys, at least, to better understand the intentions of an observed movement. The mirror neurons of the primates are already active immediately before the actual perception of the movement. The brain thus apparently designs a rough idea of the expected events and stimulates the associated regions. In this way, the human brain presumably also provides a prediction of the unexpected and the future. Motor simulation applies not only by observing other people, but also to observing moving points or machines. Besides mirror movements for the observation of body movements, there are probably also mirror movements for the observation of emotional movements. Researchers today speculate at least about the relevance of the mirror system for passively observed emotional movements and empathy.The existence of emotion mirror neurons is not yet considered proven, but a connection between motor mirror neurons and empathy is discussed as a possibility.
Diseases and disorders
Diseases and ailments of the mirror system are not yet known, as research on this is still in its infancy. Presumably, however, various neurological disease patterns can affect the mirror neurons. For example, inflammation of mirror neuronal nerve tissue, as occurs in the autoimmune disease multiple sclerosis, would be conceivable. Equally conceivable contexts for mirror neuronal lesions are tumors in Brodmann’s area 44 or strokes. Whether complaints with imitation or empathy develop after mirror neuronal lesions remains a subject of research. Research on the mirror system and mirror motion in humans has been exceptional. Mostly, research has been conducted in the context of brain surgery and otherwise untreatable epilepsy. In the case of epilepsy, depth electrodes were transplanted into the corresponding regions of the patients to precisely localize the foci. The electrodes were used for additional scientific measurements after the patients’ consent and in this way contributed to the findings in the mirror movement. In humans, neurons of the areas that are known mirror neuron areas in macaques were nevertheless not examined, because foci of epilepsy are rarely found in these areas. Measurements in other areas were useful to measure the local distribution of mirror neurons, which in humans does not necessarily correspond to the areas distributed among macaques. A small number of mirror neurons could at least be detected in this way. However, since the study participants were exclusively patients with a neurological disease, universal correlations remain controversial. Critics also claim that mirror neurons cannot play a perpetrator role in action understanding because they are not intelligent agents. Complex things like other people’s intentions, they argue, rely on representation in networks that are at least as complex.