In normally developing humans
Research on theory of mind in autism led to the view that mentalizing abilities are subserved by dedicated mechanisms that can (in some cases) be impaired while general cognitive function remains largely intact. Neuroimaging research has supported this view, demonstrating specific brain regions consistently engaged during theory of mind tasks. Early PET research on theory of mind, using verbal and pictorial story comprehension tasks, identified a set of regions including the medial prefrontal cortex (mPFC), and area around posterior superior temporal sulcus (pSTS), and sometimes precuneus and amygdala/temporopolar cortex . Subsequently, research on the neural basis of theory of mind has diversified, with separate lines of research focused on the understanding of beliefs, intentions, and more complex properties of minds such as psychological traits.
Studies from Rebecca Saxe’s lab at MIT, using a false belief versus false photograph task contrast aimed to isolate the mentalizing component of the false belief task, have very consistently found activation in mPFC, precuneus, and temporo-parietal junction (TPJ), right-lateralized. In particular, it has been proposed that the right TPJ (rTPJ) is selectively involved in representing the beliefs of others.However, this hypothesis remains controversial, because the same rTPJ region has been consistently activated during spatial reorienting of visual attention; Jean Decety from the University of Chicago and Jason Mitchell from Harvard have thus proposed that the rTPJ subserves a more general function involved in both false belief understanding and attentional reorienting, rather than a mechanism specialized for social cognition.
Functional imaging has also been used to study the detection of mental state information in Heider-Simmel-esque animations of moving geometric shapes, which typical humans automatically perceive as social interactions laden with intention and emotion. Three studies found remarkably similar patterns of activation during the perception of such animations versus a random or deterministic motion control: mPFC, pSTS, fusiform face area (FFA), and amygdala were selectively engaged during the ToM condition.] Another study presented subjects with an animation of two dots moving with a parameterized degree of intentionality (quantifying the extent to which the dots chased each other), and found that pSTS activation correlated with this parameter.
A separate body of research has implicated the posterior superior temporal sulcus in the perception of intentionality in human action; this area is also involved in perceiving biological motion, including body, eye, mouth, and point-light display motion . One study found increased pSTS activation while watching a human lift his hand versus having his hand pushed up by a piston (intentional versus unintentional action). Several studies have found increased pSTS activation when subjects perceive a human action that is incongruent with the action expected from the actor’s context and inferred intention: for instance, a human performing a reach-to-grasp motion on empty space next to an object, versus grasping the object; a human shifting eye gaze toward empty space next to a checkerboard target versus shifting gaze toward the target; a human turning on a light with his knee, versus turning on a light with his knee while carrying a pile of books; and a walking human pausing as he passes behind a bookshelf, versus walking at a constant speed. In these studies, actions in the “congruent” case have a straightforward goal, and are easy to explain in terms of the actor’s intention; the incongruent actions, on the other hand, require further explanation (why would someone twist empty space next to a gear?), and apparently demand more processing in the STS. Note that this region is distinct from the temporo-parietal area activated during false belief tasks. Also note that pSTS activation in most of the above studies was largely right-lateralized, following the general trend in neuroimaging studies of social cognition and perception: also right-lateralized are the TPJ activation during false belief tasks, the STS response to biological motion, and the FFA response to faces.
Neuropsychological evidence has provided support for neuroimaging results on the neural basis of theory of mind. A study with patients suffering from a lesion of the temporoparietal junction of the brain (between the temporal lobe and parietal lobe) reported that they have difficulty with some theory of mind tasks. This shows that theory of mind abilities are associated with specific parts of the human brain. However, the fact that the medial prefrontal cortex and temporoparietal junction are necessary for theory of mind tasks does not imply that these regions are specific to that function. TPJ and mPFC may subserve more general functions necessary for ToM.
Research by Vittorio Gallese, Luciano Fadiga and Giacomo Rizzolatti has shown that some sensorimotor neurons, which are referred to as mirror neurons, first discovered in the premotor cortex of rhesus monkeys, may be involved in action understanding. Single-electrode recording revealed that these neurons fired when a monkey performed an action and when the monkey viewed another agent carrying out the same task. Similarly, fMRI studies with human participants have shown brain regions (assumed to contain mirror neurons) are active when one person sees another person’s goal-directed action. These data have led some authors to suggest that mirror neurons may provide the basis for theory of mind in the brain, and to support simulation theory of mind reading (see above).
However, there is also evidence against the link between mirror neurons and theory of mind. First, macaque monkeys have mirror neurons but do not seem to have a ‘human-like’ capacity to understand theory of mind and belief. Second, fMRI studies of theory of mind typically report activation in the mPFC, temporal poles and TPJ or STS, but these brain areas are not part of the mirror neuron system. Some investigators, like developmental psychologist Andrew Meltzoff and neuroscientist Jean Decety, believe that mirror neurons merely facilitate learning through imitation and may provide a precursor to the development of ToM