Social cognitive neuroscience
Social cognitive neuroscience is the scientific study of the biological processes underpinning social cognition. Specifically, it uses the tools of neuroscience to study "the mental mechanisms that create, frame, regulate, and respond to our experience of the social world". Social cognitive neuroscience uses the epistemological foundations of cognitive neuroscience, and is closely related to social neuroscience. Social cognitive neuroscience employs human neuroimaging, typically using functional magnetic resonance imaging (fMRI). Human brain stimulation techniques such as transcranial magnetic stimulation and transcranial direct-current stimulation are also used. In nonhuman animals, direct electrophysiological recordings and electrical stimulation of single cells and neuronal populations are utilized for investigating lower-level social cognitive processes.
History and methods
The first scholarly works about the neural bases of social cognition can be traced back to Phineas Gage, a man who survived a traumatic brain injury in 1849 and was extensively studied for resultant changes in social functioning and personality. In 1924, esteemed psychologist Gordon Allport wrote a chapter on the neural bases of social phenomenon in his textbook of social psychology. However, these works did not generate much activity in the decades that followed. The beginning of modern social cognitive neuroscience can be traced to Michael Gazzaniga's book, Social Brain, which attributed cerebral lateralization to the peculiarities of social psychological phenomenon. Isolated pockets of social cognitive neuroscience research emerged in the late 1980s to the mid-1990s, mostly using single-unit electrophysiological recordings in nonhuman primates or neuropsychological lesion studies in humans. During this time, the closely related field of social neuroscience emerged in parallel, however it mostly focused on how social factors influenced autonomic, neuroendocrine, and immune systems. In 1996, Giacomo Rizzolatti's group made one of the most seminal discoveries in social cognitive neuroscience: the existence of mirror neurons in macaque frontoparietal cortex. The mid-1990s saw the emergence of functional positron emission tomography for humans, which enabled the neuroscientific study of abstract social cognitive functions such as theory of mind and mentalizing. However, PET is prohibitively expensive and requires the ingestion of radioactive tracers, thus limiting its adoption.In the year 2000, the term social cognitive neuroscience was coined by Matthew Lieberman and Kevin Ochsner, who are from social and cognitive psychology backgrounds, respectively. This was done to integrate and brand the isolated labs doing research on the neural bases of social cognition. Also in the year 2000, Elizabeth Phelps and colleagues published the first fMRI study on social cognition, specifically on race evaluations. The adoption of fMRI, a less expensive and noninvasive neuroimaging modality, induced explosive growth in the field. In 2001, the first academic conference on social cognitive neuroscience was held at University of California, Los Angeles. The mid-2000s saw the emergence of academic societies related to the field, as well as peer-reviewed journals specialized for the field. In the 2000s and beyond, labs conducting social cognitive neuroscience research proliferated throughout Europe, North America, East Asia, Australasia, and South America.
Starting in the late 2000s, the field began to expand its methodological repertoire by incorporating other neuroimaging modalities, advanced computational methods, and brain stimulation techniques. Due to the volume and rigor of research in the field, the 2010s saw social cognitive neuroscience achieving mainstream acceptance in the wider fields of neuroscience and psychology.
Hyperscanning or inter-brain research is becoming the most frequent approach to studying social cognition. It is thought that exploring the correlation of neuronal activities of two or more brains in shared cognitive tasks can contribute to understanding the relationship between social experiences and neurophysiological processes. In 2024, inspired by research on interpersonal neural synchronization and neuroscience studies on fetal brain responses to auditory stimuli that revealed increased neuronal activity in the fetal brain when it was exposed to an unfamiliar voice stimuli, the mother-fetus neurocognitive model hypothesis has been put forward opening a new research direction. According to this position, interpersonal neurophysiological processes within the biological system of this dyad provide the fetal nervous system with training for proper reactions to stimuli at the onset of cognition. The hypothesis has shown that training is successful because of neural synchronization between nervous systems that occurs through the interference of local neuronal oscillations with the low-frequency electromagnetic field of the mother's heart.
Functional anatomy
Much of social cognition is primarily subserved by two dissociable macro-scale brain networks: the mirror neuron system and default mode network. MNS is thought to represent and identify observable actions that are used by DMN to infer unobservable mental states, traits, and intentions. Concordantly, the activation onset of MNS has been shown to precede DMN during social cognition. However, the extent of feedforward, feedback, and recurrent processing within and between MNS and DMN is not yet well-characterized, thus it is difficult to fully dissociate the exact functions of the two networks and their nodes.Mirror neuron system (MNS)
Mirror neurons, first discovered in macaque frontoparietal cortex, fire when actions are either performed or observed. In humans, similar sensorimotor "mirroring" responses have been found in the brain regions listed below, which are collectively referred to as MNS. The MNS has been found to identify and represent intentional actions such as facial expressions, body language, and grasping. MNS may encode the concept of an action, not just the sensory and motor information associated with an action. As such, MNS representations have been shown to be invariant of how an action is observed and how an action is performed. MNS has even been found to represent actions that are described in written language.Mechanistic theories of MNS functioning fall broadly into two camps: motor and cognitive theories. Classical motor theories posit that abstract action representations arise from simulating actions within the motor system, while newer cognitive theories propose that abstract action representations arise from the integration of multiple domains of information: perceptual, motor, semantic, and conceptual. Aside from these competing theories, there are more fundamental controversies surrounding the human MNS – even the very existence of mirror neurons in this network is debated. As such, the term "MNS" is sometimes eschewed for more functionally defined names such as "action observation network", "action identification network", and "action representation network".
The hypothesis of the mother-fetus neurocognitive model contributes to the theory of the MNS's role in social cognition. It has been shown that MNS mirror neurons are observed only in specific cases of interpersonal dynamics that meet the MFN model conditions. The MFN model is a representation of neurophysiological processes within the biological system of the Mother-Fetus dyad that provides the fetal nervous system with training for proper reactions to stimuli at the onset of cognition. It has been shown that local neuronal oscillations in both nervous systems are synchronized through interference with the low-frequency electromagnetic field of the mother's heart. So that the mother's heart oscillations synchronize the brain oscillations of already excited central and peripheral neuronal ensembles, similar in both organisms, due to physiological entrainment within the shared ecosystem. Therefore, the activation of specific sensorimotor networks in the mother entrains those in the child, and, because of the shared ecosystem, this engagement trains the young nervous system to respond correctly to certain sensory stimuli through statistical mechanisms based on numerous successful and unsuccessful trials. This entrainment provides subliminal perception in the young organism, similar to the Mother's intentional act that initiates the process of cognition.
Premotor cortex
Mirror neurons were first discovered in macaque premotor cortex. The premotor cortex is associated with a diverse array of functions, encompassing low-level motor control, motor planning, sensory guidance of movement, along with higher level cognitive functions such as language processing and action comprehension. The premotor cortex has been found to contain subregions with unique cytoarchitectural properties, the significance of which is not yet fully understood. In humans, sensorimotor mirroring responses are also found throughout premotor cortex and adjacent sections of inferior frontal gyrus and supplementary motor area.Visuospatial information is more prevalent in ventral premotor cortex than dorsal premotor cortex. In humans, sensorimotor mirroring responses extend beyond ventral premotor cortex into adjacent regions of inferior frontal gyrus, including Broca's area, an area that is critical to language processing and speech production. Action representations in inferior frontal gyrus can be evoked by language, such as action verbs, in addition to the observed and performed actions typically used as stimuli in biological motion studies. The overlap between language and action understanding processes in inferior frontal gyrus has spurred some researchers to suggest overlapping neurocomputational mechanisms between the two. Dorsal premotor cortex is strongly associated with motor preparation and guidance, such as representing multiple motor choices and deciding the final selection of action.
Intraparietal sulcus
Classical studies of action observation have found mirror neurons in macaque intraparietal sulcus. In humans, sensorimotor mirroring responses are centered around the anterior intraperietal sulcus, with responses also seen in adjacent regions such as inferior parietal lobule and superior parietal lobule. Intraparietal sulcus has been shown to more sensitive to the motor features of biological motion, relative to semantic features. Intraparietal sulcus has been shown to encode magnitude in a domain-general manner, whether it be the magnitude of a motor movement, or the magnitude of a person's social status. Intraparietal sulcus is considered a part of the dorsal visual stream, but is also thought to receive inputs from non-dorsal stream regions such as lateral occipitotemporal cortex and posterior superior temporal sulcus.Lateral occipitotemporal cortex (LOTC)
LOTC encompasses lateral regions of the visual cortex such as V5 and extrastriate body area. Though LOTC is typically associated with visual processing, sensorimotor mirroring responses and abstract action representations are reliably found in this region. LOTC includes cortical areas that are sensitive to motion, objects, body parts, kinematics, body postures, observed movements, and semantic content in verbs. LOTC is thought to encode the fine sensorimotor details of an observed action. LOTC is also thought to bind together the different means by which a specific action can be carried out.Default mode network (DMN)
The default mode network is thought to process and represent abstract social information, such as mental states, traits, and intentions. Social cognitive functions such as theory of mind, mentalizing, emotion recognition, empathy, moral cognition, and social working memory consistently recruit DMN regions in human neuroimaging studies. Though the functional anatomy of these functions can differ, they often include the core DMN hubs of medial prefrontal cortex, posterior cingulate, and temporoparietal junction. Aside from social cognition, the DMN is broadly associated with internally directed cognition. The DMN has been found to be involved in memory-related processing, self-related processing, and mindwandering. Unlike studies of the mirror neuron system, task-based DMN investigations almost always use human subjects, as DMN-related social cognitive functions are rudimentary or difficult to measure in nonhumans. However, much of DMN activity occurs during rest, as DMN activation and connectivity are quickly engaged and sustained during the absence of goal-directed cognition. As such, the DMN is widely thought the subserve the "default mode" of mammalian brain function.The interrelations between social cognition, rest, and the diverse array of DMN-related functions are not yet well understood and is a topic of active research. Social, non-social, and spontaneous processes in the DMN are thought to share at least some underlying neurocomputational mechanisms with each other.
Medial prefrontal cortex (mPFC)
Medial prefrontal cortex is strongly associated with abstract social cognition such as mentalizing and theory of mind. Mentalizing activates much of the mPFC, but dorsal mPFC appears to be more selective for information about other people, while anterior mPFC may be more selective for information about the self.Ventral regions of mPFC, such as ventromedial prefrontal cortex and medial orbitofrontal cortex, are thought to play a critical role in the affective components of social cognition. For example, ventromedial prefrontal cortex has been found to represent affective information about other people. Ventral mPFC has been shown to be critical in the computation and representation of valence and value for many types of stimuli, not just social stimuli.
The mPFC may subserve the most abstract components of social cognition, as it is one of the most domain general brain regions, sits at the top of the cortical hierarchy, and is last to activate during DMN-related tasks.