Neural basis of making mental state inferences about groups of people

Much owing to recent research efforts, understanding of how the human brain represents intentions of other persons has steadily increased. Neuroimaging studies have disclosed several brain regions that are critically involved in enabling humans to have theory of mind of other persons, including medial prefrontal cortex, anterior temporal lobe, temporoparietal junction, and medial parietal cortex. In addition to inferring intentions of another person, however, intentions are often attributed to groups of people (e.g., “cognitive neuroscientists aim to solve the mind-body problem”). It has remained unexplored whether the brain mechanisms that enable one to simulate the mind of another person are the same as (or different from) the cerebral events that take place when mentalizing about the intentions of social groups.

In their recent study, Dr. Juan Manuel Contreras et al. (2013) carried out two experiments in healthy volunteers with functional magnetic resonance imaging. Pictures of groups and individuals were shown to participants during scanning, and they were to make judgments about whether either groups or individuals would enjoy a long car ride (i.e., a mentalizing task) vs. whether either groups or individuals would stay afloat in a raft or with a pair of arm floatation devices (i.e., a judgment task not requiring making inferences about the mental states of others). It was observed that brain regions that responded when making inferences about the mental states of other persons are also responding when inferences were made about the mental states of groups of people, however, multivoxel pattern analysis disclosed that distributed patterns of activity within these areas differed when making inferences about mental states of individuals vs. groups.

These highly exciting and results pave way for an important area of cognitive neuroscience, namely extending research on the neural basis of social cognition to studying how it is possible for one to perceive, understand, and predict social group behavior. Humans are inherently social species, and social groups play a central role in the lives of everyone. Given this, bridging the gap between scientific fields that study social groups (such as social psychology and sociology) and cognitive neuroscience is a very promising and fruitful relatively new area of research.

Reference: Contreras JM, Schirmer J, Banaji MR, Mitchell JP. Common brain regions with distinct patterns of neural responses during mentalizing about groups and individuals. Journal of Cognitive Neuroscience (2013) e-publication ahead of print. http://dx.doi.org/10.1162/jocn_a_00403

Blockade of mu-receptors in striatum subregions differentially regulates monogamous pair bonding in prairie voles

Social neuroscience is a very important area of cognitive neuroscience that deals with fundamental questions such as how social bonding and group formation take place. Pair bonding, i.e., formation of lasting monogamous relationships, is a specific form of social bonding that is observed in humans and also in some other species such as prairie voles.  Neurochemistry, including the opioidergic system, is known to play a pivotal role in pair bonding. Previous animal studies have demonstrated that striatal mu opioidergic receptors regulate pair bonding, however, the relative contributions of striatal subregions have remained unexplored.

In their recent study, Dr. Shanna Resendez et al. (2013) blocked the mu-receptors in different areas of the striatum of female prairie voles during cohabitation with male prairie voles under settings that have been previously observed to result in pair bonding, measured as partner preference following the cohabitation period. Indeed, antagonizing the mu-receptors with one or three microgram doses of H-D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH₂ produced differential effects, with decreases in mating behaviors during the cohabitation period as well as inhibition of subsequently observed partner preference observed with blockade of mu-receptors in dorsal striatum. Blockade of dorsomedial nucleus accumbens shell mu-receptors, in turn, inhibited acquisition of partner preference without reducing mating behavior during the cohabitation period. As an important control measure, mu-receptor blockade did not result in reduced locomotor activity.

These results significantly advance understanding of the role of mu-opioidergic receptors in pair bonding. In the light of these results, the blockade of mu-opioid receptors in dorsal striatum appears to reduce acquisition of partner preference by inhibiting mating behavior. In contrast, antagonizing the mu-receptors in the dorsomedial shell of nucleus accumbens reduces pair bonding by reducing the hedonic and/or rewarding aspects of mating behavior. Overall, this study very nicely demonstrates the power of behavioral-pharmacology paradigms in carefully selected animal models in unraveling the neural basis of higher-order social behaviors such as monogamous pair bonding.

Reference: Resendez SL, Dome M, Gormley G, Franco D, Nevárez N, Hamid AA, Aragona BJ. Mu-opioid receptors within subregions of the striatum mediate pair bond formation through parallel tet distinct reward mechanisms. Journal of Neuroscience (2013) 33: 9140–9149. http://dx.doi.org/10.1523/JNEUROSCI.4123-12.2013

Rapid functional magnetic resonance imaging sequence provides accurate information about timing of neural events

Development of non-invasive neuroimaging methods has been a prerequisite for emergence of and progress in the field of cognitive neuroscience. Indeed, the possibility to measure brain function indirectly in healthy volunteers without penetrating the skull is technologically outright amazing. One of the largest challenges that have remained has been due to the assumed sluggishness of the hemodynamic response that is measured with functional magnetic resonance imaging, which has limited attempts to measure temporal interplay between brain regions during task performance. However, there are some studies that have suggested presence of more accurate response-timing information in the hemodynamics than what has been predominantly believed, and at the same time (even an order of magnitude) faster MR acquisition sequences, such as dynamic magnetic resonance inverse imaging (InI), have been developed that allow whole-head functional volume acquisition as rapidly as 100 msec.

In their recent study, Dr. Fa-Hsuan Lin et al. (2013) combined InI and magnetoencephalography (MEG) to answer the question of whether the faster functional MRI sequences can be utilized to determine differences between response latencies between cortical regions. In the main experiment and two control experiments, altogether 41 subjects performed a simple visuomotor reaction time task during fMRI and MEG. The authors observed that with the faster acquisition rate fMRI could resolve even relatively small temporal delays in responses between cortical areas and the pattern of delays corresponded closely with those estimated with MEG. In one of the control experiments, the order of the visual and motor events was reversed to examine whether latency differences observed between cortical areas were caused by the hemodynamics genuinely measuring the latency of neural responses or, alternatively, whether the latency differences were due to inherent differences in hemodynamic responses properties of the underlying areas. The first hypothesis turned out to be the correct as indeed reversing the order of the visual and motor events reversed the order of hemodynamic responses across the respective areas.

These findings provide a highly exciting and novel methodological demonstration that significantly expands the usability of functional magnetic resonance imaging in cognitive neuroscience research in the future. The results provide evidence in support of the hypothesis that brain hemodynamics do contain (in the eyes of many even surprisingly) accurate information about the latencies of underlying neural events. These findings also stress the importance of methodological advances provided by the development of temporally more accurate fMRI sequences, an area of work that has been at times even belittled due to assumptions that hemodynamics would inherently not hold information about timing of neural events.

Reference: Lin F-H, Witzel T, Raij T, Ahveninen J, Tsai KWN, Chu Y-H, Chang W-T, Nummenmaa A, Polinemi JR, Kuo W-J, Hsieh J-C, Rosen BR, Belliveau JW. FMRI hemodynamics accurately reflects neuronal timing in the human brain measured by MEG. Neuroimage (2013) 78: 372–384. http://dx.doi.org/10.1016/j.neuroimage.2013.04.017

Distinct pattern of structural and functional connectivity changes associated with shyness in healthy adults

Shyness can be described as a personality trait that is reflected as discomfort that takes place especially in social situations that involve new persons or novel situations. Typically the degree of shyness is stronger in childhood, but approximately 10–25% of the adult population can be described as being shy. Importantly, shyness can predict life outcomes involving social relationships and occupational achievement. In neuroimaging studies, shyness and social anxiety have been both associated with enhanced responsiveness in frontal cortical and limbic areas to social stimuli, however, potential overlap between structural and functional connectivity patterns in persons who score high on shyness and social anxiety traits has remained an open question.

In their recent study, Yang et al. (2013) studied a cohort of 61 healthy individuals, assessed for shyness and social anxiety with Cheek and Buss Shyness and Liebowitz Social Anxiety scales, with combination of anatomical and resting-state functional magnetic resonance imaging (MRI/fMRI). Voxel-based gray-matter morphometry was quantified from anatomical MRIs and seed-based resting-state functional connectivity was obtained from the fMRI data. Correlations between these measures and shyness as well as social anxiety were then calculated.

Shyness scores predicted gray matter density in cerebellum, right insula, and bilaterally both superior temporal and parahippocampal gyri. Functional connectivity between several brain regions correlated with shyness, including connectivity between superior temporal gyrus, parahippocampal gyrus and frontal gyri, connectivity between insula, precentral gyrus, and inferior parietal lobule, connectivity between cerebellum and precuneus, as well as connectivity between amygdala and frontal and inferior parietal areas. By contrast, the authors failed to observe any structural or functional connectivity measures correlating with social anxiety.

This study opens up a novel and interesting area of research where research on the neural basis of personality traits is extended to shyness, by suggesting structural and functional connectivity changes in shy persons involving a number of brain areas that have consistently been associated with processing of social and emotional stimuli. Their findings further support the view that shyness should be considered as phenomenon distinct from social anxiety.

Reference: Yang X, Kendrick KM, Wu Q, Chen T, Lama S, Cheng B, Li S, Huang X, Gong Q. Structural and functional connectivity changes in the brain associated with shyness but not with social anxiety. PLoS ONE (2013) 8: e63151. http://dx.doi.org/10.1371/journal.pone.0063151