Recent Neuropolitics Abstracts

By Darren Schreiber

We’ve got lots of new work showing showing the role of the default mode network, specifically in social cognition (1, 3, 4, 8, 10).  While this was a speculation when I was writing about it five years ago, it seems to be quite cemented now.  We’ve also got a set of articles discussing reward processing (2, 6, 7).  I thought the overview piece on the Allen Brain Atlas was interesting (11).  Currently, the mouse brain is the most complete, but Wired Magazine had a fascinating piece about the work that is currently proceeding on doing the same thing for the human brain.

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1) Functional connectivity and alterations in baseline brain state in humans.
2) The impact of social comparison on the neural substrates of reward processing: an event-related potential study.
3) Neural correlates of social cognition in naturalistic settings: a model-free analysis approach.
4) Understanding others’ actions and goals by mirror and mentalizing systems: a meta-analysis
5) Double dissociation between action-driven and perception-driven conflict resolution invoking anterior versus posterior brain systems.
6) The influence of context valence in the neural coding of monetary outcomes.
7) Different representations of relative and absolute subjective value in the human brain
8) Neural Systems of Social Comparison and the “Above-Average” Effect
9) Experimental evolution of bet hedging
10) What does the retrosplenial cortex do?
11) The Allen Brain Atlas: 5 years and beyond
12) The functional anatomy of the frontal lobes

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1) Martuzzi et al. Functional connectivity and alterations in baseline brain state in humans. Neuroimage (2010) vol. 49 (1) pp. 823-34

This work examines the influence of changes in baseline activity on the intrinsic functional connectivity fMRI (fc-fMRI) in humans. Baseline brain activity was altered by inducing anesthesia (sevoflurane end-tidal concentration 1%) in human volunteers and fc-fMRI maps between the pre-anesthetized and anesthetized conditions were compared across different brain networks. We particularly focused on low-level sensory areas (primary somatosensory, visual, and auditory cortices), the thalamus, and pain (insula), memory (hippocampus) circuits, and the default mode network (DMN), the latter three to examine higher-order brain regions. The results indicate that, while fc-fMRI patterns did not significantly differ (p<0.005; 20-voxel cluster threshold) in sensory cortex and in the DMN between the pre- and anesthetized conditions, fc-fMRI in high-order cognitive regions (i.e. memory and pain circuits) was significantly altered by anesthesia. These findings provide further evidence that fc-fMRI reflects intrinsic brain properties, while also demonstrating that 0.5 MAC sevoflurane anesthesia preferentially modulates higher-order connections.

2) Qiu et al. The impact of social comparison on the neural substrates of reward processing: an event-related potential study. Neuroimage (2010) vol. 49 (1) pp. 956-62

Event-related potentials (ERPs) were recorded to explore the electrophysiological correlates of reward processing in the social comparison context when subjects performed a simple number estimation task that entailed monetary rewards for correct answers. Three social comparison stimulus categories (three relative reward levels/self reward related to the other subject’s) were mainly prepared: Self:Other=1:2 (Disadvantageous inequity condition); Self:Other=1:1 (Equity condition); and Self:Other=2:1 (Advantageous inequity condition). Results showed that: both Disadvantageous and Advantageous inequity elicited a more negative ERP deflection (N350-550) than did Equity between 350 and 550 ms, and the generators of N350-550 were localized near the parahippocampal gyrus and the medial frontal/anterior cingulate cortex, which might be related to monitor and control reward prediction error during reward processing. Then, Disadvantageous and Advantageous inequity both elicited a more late negative complex (LNC1 and LNC2) than did Equity between 550 and 750 ms. The generators of LNC1 and LNC2 were both localized near the caudate nucleus, which might be related to reward processing under social comparison.

3) Wolf et al. Neural correlates of social cognition in naturalistic settings: a model-free analysis approach. Neuroimage (2010) vol. 49 (1) pp. 894-904

Neuroimaging studies have consistently identified a network of brain regions subserving inferences of other humans’ mental states. This network consists of the superior temporal sulcus, temporoparietal junction, medial prefrontal cortex, temporal poles, and precuneus. Little is known, however, about the neural substrate underlying Theory of Mind processes in close to real-life conditions. To investigate those processes in more naturalistic settings, we used an fMRI adaptation of the video-based Movie for the Assessment of Social Cognition (MASC; Dziobek et al., 2006), which considers separate analysis of implicit mental state reasoning during rapidly changing perceptual cues as demanded in naturalistic settings and explicit mental state reasoning. We analyzed fMRI data by means of both a standard general linear model (GLM) approach and a tensor probabilistic independent component analysis (T-PICA), which is a novel model-free approach that allows decomposition of activation into independent spatio-temporally coherent functional networks. The model-based GLM approach revealed the typical explicit mental state reasoning network. Complementary to the GLM approach, the model-free T-PICA approach showed that those regions are also recruited during implicit mental state reasoning and that they are represented in three independent, functionally connected networks. The first component, mediating face processing and recognition, comprises the occipito-parietotemporal cortices, while the second component, involved in language comprehension, comprises the temporal lobes, lateral prefrontal cortex, and precuneus. The dorsomedial prefrontal cortex and the precuneus comprise the third component, which is likely responsible for self-referential mental activity. These results show that the mental state reasoning network can be decomposed into circumscribed functional networks mediating differential aspects of Theory of Mind.

4) Van Overwalle and Baetens. Understanding others’ actions and goals by mirror and mentalizing systems: a meta-analysis. Neuroimage (2009) vol. 48 (3) pp. 564-84

This meta-analysis explores the role of the mirror and mentalizing systems in the understanding of other people’s action goals. Based on over 200 fMRI studies, this analysis demonstrates that the mirror system – consisting of the anterior intraparietal sulcus and the premotor cortex – is engaged when one perceives articulated motions of body parts irrespective of their sensory (visual or auditory) or verbal format as well as when the perceiver executes them. This confirms the matching role of the mirror system in understanding biological action. Observation of whole-body motions and gaze engage the posterior superior temporal sulcus and most likely reflects an orientation response in line with the action or attention of the observed actor. In contrast, the mentalizing system – consisting of the temporo-parietal junction, the medial prefrontal cortex and the precuneus – is activated when behavior that enables inferences to be made about goals, beliefs or moral issues is presented in abstract terms (e.g., verbal stories or geometric shapes) and there is no perceivable biological motion of body parts. A striking overlap of brain activity at the temporo-parietal junction between social inferences and other, non-social observations (e.g., Posner’s cuing task) suggests that this area computes the orientation or direction of the behavior in order to predict its likely end-state (or goal). No conclusions are drawn about the specific functionality of the precuneus and the medial prefrontal cortex. Because the mirror and mentalizing systems are rarely concurrently active, it appears that neither system subserves the other. Rather, they are complementary. There seems, however, to be a transition from the mirror to the mentalizing system even when body-part motions are observed by perceivers who are consciously deliberating about the goals of others and their behavioral executions, such as when perceived body motions are contextually inconsistent, implausible or pretended.

5) Schulte et al. Double dissociation between action-driven and perception-driven conflict resolution invoking anterior versus posterior brain systems. Neuroimage (2009) vol. 48 (2) pp. 381-90

The ability to select and integrate relevant information in the presence of competing irrelevant information can be enhanced by advance information to direct attention and guide response selection. Attentional preparation can reduce perceptual and response conflict, yet little is known about the neural source of conflict resolution, whether it is resolved by modulating neural responses for perceptual selection to emphasize task-relevant information or for action selection to inhibit pre-potent responses to interfering information. We manipulated perceptual information that either matched or did not match the relevant color feature of an upcoming Stroop stimulus and recorded hemodynamic brain responses to these events. Longer reaction times to incongruent than congruent color-word Stroop stimuli indicated conflict; however, conflict was even greater when a color cue correctly predicted the Stroop target’s color (match) than when it did not (nonmatch). A predominantly anterior network was activated for Stroop-match and a predominantly posterior network was activated for Stroop-nonmatch. Thus, when a stimulus feature did not match the expected feature, a perceptually-driven posterior attention system was engaged, whereas when interfering, automatically-processed semantic information required inhibition of pre-potent responses, an action-driven anterior control system was engaged. These findings show a double dissociation of anterior and posterior cortical systems engaging in different types of control for perceptually-driven and action-driven conflict resolution.

6) Hardin et al. The influence of context valence in the neural coding of monetary outcomes. Neuroimage (2009) vol. 48 (1) pp. 249-57

The emotional significance of objects and events depends on the context in which they occur. Using functional magnetic resonance imaging, we examined the modulation of neural responses to monetary outcomes while subjects performed a decision-making task in a positive and a negative economic context. Neural responses indicated a relative regional specialization in the neural coding of outcome valence and followed three distinct patterns. The nucleus accumbens (NAc) and orbital frontal cortex (OFC) appeared to code the most extreme outcome in each context, with a potentiated response for favorable outcomes by a positive context. The amygdala and insula appeared to also code highly salient outcomes, but showed a potentiated response to unfavorable outcomes occurring in a negative context. The medial prefrontal cortex (medPFC), on the other hand, only coded favorable responses occurring in a positive context. Moreover, the medPFC showed large inter-individual variability when responding to outcomes in a negative context, suggesting that its role in a negative context may depend on a number of individual factors. The results of this work provide evidence of complex valence-based regional dissociations that are influenced by contextual factors.

7) Grabenhorst and Rolls. Different representations of relative and absolute subjective value in the human brain. Neuroimage (2009) vol. 48 (1) pp. 258-68

Relative reward value is important for the choice between a set of available rewards, and absolute reward value for stable and consistent economic choice. It is unclear whether in the human brain subjective absolute value representations can be dissociated from relative reward value representations. Using fMRI, we investigated how the subjective pleasantness of an odor is influenced by whether the odor is presented in the context of a relatively more pleasant or less pleasant odor. We delivered two of a set of four odors separated by a delay of 6 s, with the instruction to rate the pleasantness of the second odor, and searched for brain regions where the activations were correlated with the absolute pleasantness rating of the second odor, and for brain regions where the activations were correlated with the difference in pleasantness of the second from the first odor, that is, with relative pleasantness. Activations in the anterolateral orbitofrontal cortex tracked the relative subjective pleasantness, whereas activations in the anterior insula tracked the relative subjective unpleasantness. In contrast, in the medial and midorbitofrontal cortex activations tracked the absolute pleasantness of the stimuli. Thus, both relative and absolute subjective value signals which provide important inputs to decision-making processes about which stimulus to choose are separately and simultaneously represented in the human brain.

8) Beer and Hughes. Neural Systems of Social Comparison and the “Above-Average” Effect. Neuroimage (2009) pp.

Extant neural models of self-evaluation are dominated by associations with medial prefrontal cortex (MPFC) and posterior cingulate cortex (PCC) function and have mostly been developed from studies differentiating self-evaluation from evaluation of other people. Although self-evaluation is robustly characterized by systematic biases, current neural models of self-evaluation cannot speak to their neurobiology because of a lack of research. The few extant studies have made claims about associations between bias and ventral anterior cingulate cortex (vACC) function but have confounded bias with the valence of experimental stimuli. In Study 1, fMRI was used to examine the neurobiology of the “above average” effect, a robust self-evaluation bias. The majority of people judge their personality to be more desirable (i.e. more positive and less negative traits) than their peers’ personalities. MPFC and PCC were significantly more activated by a condition that reduced susceptibility to “above average” judgments. However, MPFC and PFCC activity were not modulated by individual differences in “above average” judgments. VACC activity distinguished positive from negative valence but did not predict individual differences in “above average” judgments. Instead, the extent to which participants viewed themselves as “above average” was negatively correlated with orbitofrontal cortex (OFC) and, to a lesser extent, dorsal anterior cingulate cortex (dACC) activation. A complementary study found that mental load increases “above average” judgments (Study 2). These findings are the first to directly examine the neural systems involved in social judgment bias and have implications for the association between frontal lobe dysfunction and poor insight.

9) Beaumont et al. Experimental evolution of bet hedging. Nature (2009) vol. 462 (7269) pp. 90-3

Bet hedging-stochastic switching between phenotypic states-is a canonical example of an evolutionary adaptation that facilitates persistence in the face of fluctuating environmental conditions. Although bet hedging is found in organisms ranging from bacteria to humans, direct evidence for an adaptive origin of this behaviour is lacking. Here we report the de novo evolution of bet hedging in experimental bacterial populations. Bacteria were subjected to an environment that continually favoured new phenotypic states. Initially, our regime drove the successive evolution of novel phenotypes by mutation and selection; however, in two (of 12) replicates this trend was broken by the evolution of bet-hedging genotypes that persisted because of rapid stochastic phenotype switching. Genome re-sequencing of one of these switching types revealed nine mutations that distinguished it from the ancestor. The final mutation was both necessary and sufficient for rapid phenotype switching; nonetheless, the evolution of bet hedging was contingent upon earlier mutations that altered the relative fitness effect of the final mutation. These findings capture the adaptive evolution of bet hedging in the simplest of organisms, and suggest that risk-spreading strategies may have been among the earliest evolutionary solutions to life in fluctuating environments.

10) Vann et al. What does the retrosplenial cortex do?. Nat Rev Neurosci (2009) vol. 10 (11) pp. 792-802

The past decade has seen a transformation in research on the retrosplenial cortex (RSC). This cortical area has emerged as a key member of a core network of brain regions that underpins a range of cognitive functions, including episodic memory, navigation, imagination and planning for the future. It is now also evident that the RSC is consistently compromised in the most common neurological disorders that impair memory. Here we review advances on multiple fronts, most notably in neuroanatomy, animal studies and neuroimaging, that have highlighted the importance of the RSC for cognition, and consider why specifying its precise functions remains problematic.

11) Jones et al. The Allen Brain Atlas: 5 years and beyond. Nat Rev Neurosci (2009) vol. 10 (11) pp. 821-8

The Allen Brain Atlas, a Web-based, genome-wide atlas of gene expression in the adult mouse brain, was an experiment on a massive scale. The development of the atlas faced a combination of great technical challenges and a non-traditional open research model, and it encountered many hurdles on the path to completion and community adoption. Having overcome these challenges, it is now a fundamental tool for neuroscientists worldwide and has set the stage for the creation of other similar open resources. Nevertheless, there are many untapped opportunities for exploration.

12) Nachev et al. The functional anatomy of the frontal lobes. Nat Rev Neurosci (2009) vol. 10 (11) pp. 829

In their illuminating recent article (Is the rostro-caudal axis of the frontal lobe hier- archical? Nature Rev. Neurosci. 10, 659–669 (2009))1, Badre and D’Esposito generalize to the frontal lobes as a whole a point we recently made about the medial frontal cor- tex2: that the functional architecture suggests a continuous rostro-caudal gradient reflect- ing the conditional complexity of the associ- ated behaviour. Reviewing a broad swathe of behavioural and neurophysiological studies, they argue — convincingly, in our view — that a wealth of data now supports this new conceptual framework for frontal lobe func- tion. However, there are some important consequences of such a perspective that might not be apparent at first glance and that merit some further consideration.


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