Mirror neurons, discovered by Giacomo Rizzolatti and colleagues in the early 1990s in the premotor cortex of macaque monkeys, fire both when the animal performs a specific action (e.g., grasping a peanut) and when it observes another individual performing the same action. This "mirroring" property has generated enormous interest and controversy, with claims that mirror neurons underlie action understanding, imitation, empathy, language evolution, and that their dysfunction contributes to autism.
Key Structures
- Premotor cortex (F5/ventral) — A frontal motor area anterior to primary motor cortex involved in motor planning, action selection, and movement preparation, particularly in relation to f5/ventral.
- Inferior parietal lobule — A parietal region involved in spatial attention, number processing, and the integration of multisensory information.
- Superior temporal sulcus — A temporal lobe sulcus involved in processing biological motion, voice, gaze direction, and social perception.
- Broca's area (human homologue) — The left inferior frontal region critical for speech production, syntactic processing, and verbal working memory, particularly in relation to human homologue.
- fMRI — Functional magnetic resonance imaging, a neuroimaging technique that measures brain activity by detecting changes in blood oxygenation, providing detailed spatial maps of which brain regions are engag.
Key Functions
Neurons that fire both when an individual performs an action and when observing the same action performed by another, proposed to underlie action understanding, imitation, empathy, and language evolution.
Evidence
In monkeys, mirror neurons have been directly recorded in premotor cortex (F5) and inferior parietal cortex. In humans, indirect evidence from fMRI, TMS, and EEG (mu suppression) suggests a mirror neuron system in homologous regions, though individual mirror neurons have not been directly demonstrated in humans. The human mirror system is activated during action observation, imitation, and understanding of others' actions and intentions.
The mirror neuron concept has been criticized for overinterpretation. Gregory Hickok and others argue that the evidence does not support claims about mirror neurons underlying language or empathy, that action understanding can occur without motor simulation, and that the "broken mirror" theory of autism is not well supported. The core finding — neurons with both motor and observation properties — is established, but the broader theoretical claims remain contentious.
Disorders
- Autism spectrum disorder (broken mirror theory, debated) — A neurodevelopmental condition characterized by differences in social communication, restricted interests, and repetitive behaviors, with distinctive cognitive strengths and challenges.
- Apraxia — An acquired disorder of skilled movement execution not attributable to weakness, sensory loss, or comprehension deficits.
- Aphasia — Acquired language disorders resulting from brain damage, providing crucial evidence about the neural organization of language processing.
- Social cognition deficits — Impairments in the mental processes underlying social interaction, including emotion recognition, theory of mind, and empathy.