Social neuroscience: undoing the schism between neurology and psychiatry

Multiple disorders once jointly conceived as “nervous diseases” became segregated by the distinct institutional traditions forged in neurology and psychiatry. As a result, each field specialized in the study and treatment of a subset of such conditions. Here we propose new avenues for interdisciplinary interaction through a triangulation of both fields with social neuroscience. To this end, we review evidence from five relevant domains (facial emotion recognition, empathy, theory of mind, moral cognition, and social context assessment), highlighting their common disturbances across neurological and psychiatric conditions and discussing their multiple pathophysiological mechanisms. Our proposal is anchored in multidimensional evidence, including behavioral, neurocognitive, and genetic findings. From a clinical perspective, this work paves the way for dimensional and transdiagnostic approaches, new pharmacological treatments, and educational innovations rooted in a combined neuropsychiatric training. Research-wise, it fosters new models of the social brain and a novel platform to explore the interplay of cognitive and social functions. Finally, we identify new challenges for this synergistic framework.     

Neuropathology in Pitié-Salpêtrière hospital: Past,present and prospect

Pitié and La Salpêtrière, both founded in the17th century, were for long two distinct hospitals until they merged in 1964. The name La Salpêtrière is inherited from the initial purpose of the buildings designed to produce saltpeter for gun powder. But the place was soon transformed into an asylum to shelter the poor and the insane. From the care of this underprivileged population, alienists such as Pinel have paved the way for modern medicine for the mentally ill at the time of the French Revolution. In the second half of the 19th century, Jean-Martin Charcot and his students laid the foundations of modern neurology from the observation of the large population hosted in La Salpêtrière, mostly women with severe chronic diseases. Charcot led clinicopathological studies in almost all the fields of nervous system disorders. His successors (including Raymond, Dejerine, Pierre Marie) maintained the same close relationship between clinical neurology and neuropathology. In parallel with the development of neurosurgery at Pitié hospital, neuropathology first spread through small laboratories attached to clinical departments. The merger of the two hospitals in the early '60s coincided with the creation of a large university hospital in which the care and study of diseases of the nervous system were preponderant. An independent laboratory of neuropathology was created, led by Raymond Escourolle. This period was on the eve of important developments in neuroscience around the world. Today, the Pitié-Salpêtrière neuropathology laboratory still plays a central role between neurology and neurosurgery clinics and major research institutes such as the Brain Institute, callled Institut du Cerveau et de la Moelle (ICM), and the Institute of Myology.     

Comparing brains by matching connectivity profiles

The great promise of comparative neuroscience is to understand why brains differ by investigating the relations between variations in the organization of different brains, their evolutionary history, and their current ecological niche. For this approach to be successful, the organization of different brains needs to be quantifiable. Here, we present an approach to formally comparing the connectivity of different cortical areas across different brains. We exploit the fact that cortical regions can be characterized by the unique pattern of connectivity, the so-called connectivity fingerprint. By comparing connectivity fingerprints between cortical areas in the human and non-human primate brain we can identify between-species homologs, but also illustrate that is driving differences between species. We illustrate the approach by comparing the organization of the frontal cortex between humans and macaques, showing general similarities combined with some differences in the lateral frontal pole.     

My face in yours: Visuo-tactile facial stimulation influences sense of identity

Abstract

Self-face recognition is crucial for sense of identity and self-awareness. Finding self-face recognition disorders mainly in neurological and psychiatric diseases suggests that modifying sense of identity in a simple, rapid way remains a “holy grail” for cognitive neuroscience. By touching the face of subjects who were viewing simultaneous touches on a partner's face, we induced a novel illusion of personal identity that we call “enfacement”: The partner's facial features became incorporated into the representation of the participant's own face. Subjects reported that morphed images of themselves and their partner contained more self than other only after synchronous, but not asynchronous, stroking. Therefore, we modified self-face recognition by means of a simple psychophysical manipulation. While accommodating gradual change in one's own face is an important form of representational plasticity that may help maintaining identity over time, the surprisingly rapid changes induced by our procedure suggest that sense of facial identity may be more malleable than previously believed. “Enfacement” correlated positively with the participant's empathic traits and with the physical attractiveness the participants attributed to their partners. Thus, personality variables modulate enfacement, which may represent a marker of the tendency to be social and may be absent in subjects with defective empathy.     

A comparison of neural responses to appetitive and aversive stimuli in humans and other mammals

Distinguishing potentially harmful or beneficial stimuli is necessary for the self-preservation and well-being of all organisms. This assessment requires the ongoing valuation of environmental stimuli. Despite much work on the processing of aversive- and appetitive-related brain signals, it is not clear to what degree these two processes interact across the brain. To help clarify this issue, this report used a cross-species comparative approach in humans (i.e. meta-analysis of imaging data) and other mammals (i.e. targeted review of functional neuroanatomy in rodents and non-human primates). Human meta-analysis results suggest network components that appear selective for appetitive (e.g. ventromedial prefrontal cortex, ventral tegmental area) or aversive (e.g. cingulate/supplementary motor cortex, periaqueductal grey) processing, or that reflect overlapping (e.g. anterior insula, amygdala) or asymmetrical, i.e. apparently lateralized, activity (e.g. orbitofrontal cortex, ventral striatum). However, a closer look at the known value-related mechanisms from the animal literature suggests that all of these macroanatomical regions are involved in the processing of both appetitive and aversive stimuli. Differential spatiotemporal network dynamics may help explain similarities and differences in appetitive- and aversion-related activity.     

Magnetic resonance spectroscopy with transcranial direct current stimulation to explore the underlying biochemical and physiological mechanism of the human brain: A systematic review

A large body of molecular and neurophysiological evidence connects synaptic plasticity to specific functions and energy metabolism in particular areas of the brain. Furthermore, altered plasticity and energy regulation has been associated with a number of neuropsychiatric disorders. A favourable approach enabling the modulation of neuronal excitability and energy in humans is to stimulate the brain using transcranial direct current stimulation (tDCS) and then to observe the effect on neurometabolites using magnetic resonance spectroscopy (MRS). In this way, a well‐defined modulation of brain energy and excitability can be achieved using a dedicated tDCS protocol to a predetermined brain region. This systematic review was guided by the preferred reporting items for systematic reviews and meta‐analysis and summarises recent literature studying the effect of tDCS on neurometabolites in the human brain as measured by proton or phosphorus MRS. Limitations and recommendations are discussed for future research. The findings of this review provide clear evidence for the potential of using tDCS and MRS to examine and understand the effect of neurometabolites in the in vivo human brain.     

Gray matter structures associated with neuroticism: A meta‐analysis of whole‐brain voxel‐based morphometry studies

Neuroticism is major higher‐order personality trait and has been robustly associated with mental and physical health outcomes. Although a growing body of studies have identified neurostructural markers of neuroticism, the results remained highly inconsistent. To characterize robust associations between neuroticism and variations in gray matter (GM) structures, the present meta‐analysis investigated the concurrence across voxel‐based morphometry (VBM) studies using the anisotropic effect size signed differential mapping (AES‐SDM). A total of 13 studies comprising 2,278 healthy subjects (1,275 females, 29.20 ± 14.17 years old) were included. Our analysis revealed that neuroticism was consistently associated with the GM structure of a cluster spanning the bilateral dorsal anterior cingulate cortex and extending to the adjacent medial prefrontal cortex (dACC/mPFC). Meta‐regression analyses indicated that the neuroticism‐GM associations were not confounded by age and gender. Overall, our study is the first whole‐brain meta‐analysis exploring the brain structural correlates of neuroticism, and the findings may have implications for the intervention of high‐neuroticism individuals, who are at risk of mental disorders, by targeting the dACC/mPFC.     

Comparison of cerebral activation between motor execution and motor imagery of self-feeding activity

Motor imagery is defined as an act wherein an individual contemplates a mental action of motor execution without apparent action. Mental practice executed by repetitive motor imagery can improve motor performance without simultaneous sensory input or overt output. We aimed to investigate cerebral hemodynamics during motor imagery and motor execution of a self-feeding activity using chopsticks. This study included 21 healthy right-handed volunteers. The self-feeding activity task comprised either motor imagery or motor execution of eating sliced cucumber pickles with chopsticks to examine eight regions of interest: pre-supplementary motor area, supplementary motor area, bilateral prefrontal cortex, premotor area, and sensorimotor cortex. The mean oxyhemoglobin levels were detected using near-infrared spectroscopy to reflect cerebral activation. The mean oxyhemoglobin levels during motor execution were significantly higher in the left sensorimotor cortex than in the supplementary motor area and the left premotor area. Moreover, significantly higher oxyhemoglobin levels were detected in the supplementary motor area and the left premotor area during motor imagery, compared to motor execution. Supplementary motor area and premotor area had important roles in the motor imagery of self-feeding activity. Moreover, the activation levels of the supplementary motor area and the premotor area during motor execution and motor imagery are likely affected by intentional cognitive processes. Levels of cerebral activation differed in some areas during motor execution and motor imagery of a self-feeding activity. This study was approved by the Ethical Review Committee of Nagasaki University(approval No. 18110801) on December 10, 2018.