What the brain 'Likes': neural correlates of providing feedback on social media.

Evidence increasingly suggests that neural structures that respond to primary and secondary rewards are also implicated in the processing of social rewards. The 'Like'-a popular feature on social media-shares features with both monetary and social rewards as a means of feedback that shapes reinforcement learning. Despite the ubiquity of the Like, little is known about the neural correlates of providing this feedback to others. In this study, we mapped the neural correlates of providing Likes to others on social media. Fifty-eight adolescents and young adults completed a task in the MRI scanner designed to mimic the social photo-sharing app Instagram. We examined neural responses when participants provided positive feedback to others. The experience of providing Likes to others on social media related to activation in brain circuity implicated in reward, including the striatum and ventral tegmental area, regions also implicated in the experience of receiving Likes from others. Providing Likes was also associated with activation in brain regions involved in salience processing and executive function. We discuss the implications of these findings for our understanding of the neural processing of social rewards, as well as the neural processes underlying social media use

Interactions between the hippocampus and prefrontal cortex in context-dependent overlapping memory retrieval

Activation in the hippocampus (HC) and prefrontal cortex (PFC) is critical to accurately retrieve overlapping sequences. Experiments 1 and 2 tested the hypotheses that activation in and interaction between HC and PFC increases as overlap between sequences increases in a non-spatial task. Experiment 3 tested the hypothesis that theta oscillations are involved in orchestrating interactions between HC and PFC in a spatial task with overlapping elements. In the first two studies, 17 participants (aged 18-34; 11 female) learned sequences consisting of a picture frame, face, and scene. Conditions varied by degree of overlap. Using fMRI, Experiment 1 tested how degree of overlap affected HC and PFC activation. In overlapping sequences, middle and posterior HC were active when predictability of the correct response increased, dorsolateral PFC was active when participants were able to ascertain the correct set of sequences, and ventrolateral PFC was active when inhibition of interfering associations was required. Experiment 2 examined functional connectivity of HC and PFC during disambiguation. Low- and high-overlap conditions were associated with increased connectivity in separate regions at different times indicating that retrieval under the two conditions used different neural networks and strategies. Low-overlap trials were associated with increased connectivity between HC and prefrontal and parietal regions. High-overlap trials showed increased connectivity between lateral PFC and visual areas, indicating that imagery may be necessary for accurate performance. Using EEG recording, Experiment 3 examined theta activity during retrieval of well-learned, overlapping and non-overlapping mazes in 17 participants (aged 18-34, 11 female). Theta activity increased in overlapping mazes during the first of four hallways, suggesting participants were looking ahead to upcoming turns in the maze. Theta activity increased at the beginning and choice point of the third overlapping hallway, possibly in response to interference from the paired, overlapping maze. These studies provide evidence that (1) overlapping associations in non-spatial sequences elicit interactions between hippocampus and lateral prefrontal cortex, (2) increasing the degree of overlap changes the neural processes required to perform the task, and (3) theta power increases in response to increased cognitive demand and maintenance of sequence information needed to differentiate between overlapping spatial routes

Representational organization of novel task sets during proactive encoding

Recent multivariate analyses of brain data have boosted our understanding of the organizational principles that shape neural coding. However, most of this progress has focused on perceptual visual regions (Connolly et al., 2012), whereas far less is known about the organization of more abstract, action-oriented representations. In this study, we focused on humans{\textquoteright} remarkable ability to turn novel instructions into actions. While previous research shows that instruction encoding is tightly linked to proactive activations in fronto-parietal brain regions, little is known about the structure that orchestrates such anticipatory representation. We collected fMRI data while participants (both males and females) followed novel complex verbal rules that varied across control-related variables (integrating within/across stimuli dimensions, response complexity, target category) and reward expectations. Using Representational Similarity Analysis (Kriegeskorte et al., 2008) we explored where in the brain these variables explained the organization of novel task encoding, and whether motivation modulated these representational spaces. Instruction representations in the lateral prefrontal cortex were structured by the three control-related variables, while intraparietal sulcus encoded response complexity and the fusiform gyrus and precuneus organized its activity according to the relevant stimulus category. Reward exerted a general effect, increasing the representational similarity among different instructions, which was robustly correlated with behavioral improvements. Overall, our results highlight the flexibility of proactive task encoding, governed by distinct representational organizations in specific brain regions. They also stress the variability of motivation-control interactions, which appear to be highly dependent on task attributes such as complexity or novelty.SIGNIFICANCE STATEMENTIn comparison with other primates, humans display a remarkable success in novel task contexts thanks to our ability to transform instructions into effective actions. This skill is associated with proactive task-set reconfigurations in fronto-parietal cortices. It remains yet unknown, however, how the brain encodes in anticipation the flexible, rich repertoire of novel tasks that we can achieve. Here we explored cognitive control and motivation-related variables that might orchestrate the representational space for novel instructions. Our results showed that different dimensions become relevant for task prospective encoding depending on the brain region, and that the lateral prefrontal cortex simultaneously organized task representations following different control-related variables. Motivation exerted a general modulation upon this process, diminishing rather than increasing distances among instruction representations

The social brain: neural basis of social knowledge

Social cognition in humans is distinguished by psychological processes that allow us to make inferences about what is going on inside other people—their intentions, feelings, and thoughts. Some of these processes likely account for aspects of human social behavior that are unique, such as our culture and civilization. Most schemes divide social information processing into those processes that are relatively automatic and driven by the stimuli, versus those that are more deliberative and controlled, and sensitive to context and strategy. These distinctions are reflected in the neural structures that underlie social cognition, where there is a recent wealth of data primarily from functional neuroimaging. Here I provide a broad survey of the key abilities, processes, and ways in which to relate these to data from cognitive neuroscience

The role of default mode network in semantic cue integration

Recent accounts of large-scale cortical organisation suggest that the default mode network (DMN) is positioned at the top of a principal gradient, reflecting the separation between heteromodal and unimodal sensory-motor regions in patterns of connectivity and in geodesic distance along the cortical surface (Margulies et al., 2016). This isolation of DMN from external inputs might allow the integration of disparate sources of information that can constrain subsequent cognition. We tested this hypothesis by manipulating the degree to which semantic decisions for ambiguous words (e.g. JAM) were constrained by preceding visual cues depicting relevant spatial contexts (e.g. SUPERMARKET or ROAD) and/or facial emotions (e.g. HAPPY vs. FRUSTRATED). We contrasted (i) the effects of a single preceding cue with a no-cue condition employing scrambled images, and (ii) convergent spatial and emotion cues with single cues. Single cues elicited stronger activation in the multiple demand network relative to no cues, consistent with the requirement to maintain information in working memory. The availability of two convergent cues elicited stronger activation within DMN regions (bilateral angular gyrus, middle temporal gyrus, medial prefrontal cortex, and posterior cingulate), even though behavioural performance was unchanged by cueing – consequently task difficulty is unlikely to account for the observed differences in brain activation. A regions-of-interest analysis along the unimodal-to-heteromodal principal gradient revealed maximal activation for the convergent cue condition at the heteromodal end, corresponding to the DMN. Our findings are consistent with the view that regions of DMN support states of information integration that constrain ongoing cognition and provide a framework for understanding the location of these effects at the heteromodal end of the principal gradient

The Perception and Evaluation of Visual Beauty

What are the perceptual and cognitive processes that underlie our experiences of beauty? In this dissertation, I describe a series of experiments where we used functional magnetic resonance imaging (fMRI) and behavioral methods to explore the mechanisms of perception, reward representation, and decision-making during evaluations of face and place beauty. In our first study, we used fMRI to ask whether evaluative signals in frontal cortex contain category-specific information or whether these signals are encoded as a common currency across reward types. By comparing neural activity correlated with subjective ratings of face and place beauty, we showed overlapping activity in dorsal ventromedial prefrontal cortex (vmPFC), consistence with the common currency hypothesis. At the same time, our results revealed category-specific patterns of activity in ventral vmPFC and in lateral orbitofrontal cortex (latOFC), suggesting at least a partial distinction in the frontal networks recruited during the processing of different types of rewards. In a follow-up study, we used fMRI to further examine face-responsive patches of activity in latOFC by measuring response in these patches while subjects evaluated but did explicitly rate face beauty. Our results demonstrated a similar pattern of response to that observed during explicit ratings, suggesting that reward-related activity in this region is not dependent on a decision-making task. Lastly, in a series of behavioral studies, we developed a novel experimental design to measure the influence of recent trial history on current judgments of face attractiveness. We found that attractiveness judgments are simultaneously contrasted away from the attractiveness of the previous face but assimilated towards the previous numerical rating given. Our results also suggested that these influences are not specific to attractiveness judgments but may be linked to more general properties of perception and decision-making. Collectively, this work furthers our understanding of the neural mechanisms underlying evaluations of face and place beauty, and illuminates some of the specific contextual influences on these evaluations

The fearful face and beyond: fMRI studies of the human amygdala

The amygdala has been labeled as a detector of threat , evidenced by its heightened response to fearful faces in human neuroimaging studies. A critical element of the fearful face is an increase in eye white area, hypothesized to be crucial for the rapid detection of fear in another\u27s face. Yet other facial expressions can also increase eye white area in a manner that is similar (a lateral shift in gaze) or identical (surprise) to fear. It is unknown if the amygdala can differentiate between these types of increases in eye white area and those that are specifically associated with fear when using only the eye region of the face. Furthermore, whether the fearful mouth can elicit an amygdala response when shown in isolation is unknown. Using functional magnetic resonance imaging, we found that the amygdala responded robustly to fearful eyes as well as eye stimuli that were ambiguous in nature. The fearful mouth, on the other hand, was unable to generate a significant response from the amygdala, however the happy condition elicited a slight response from the right amygdala, most likely due to the visual salience of the smile. We also observed a functional laterality between the two amygdalae in that the left amygdala responded only to fearful eyes while the right amygdala activated to any change in the eyes; the same laterality was also evident when eye stimuli were ambiguous in nature indicating that the left amygdala is more tuned to detect fear in the eyes while the right amygdala acts as a general detector of eye changes. This lends more evidence to the existence of parallel mechanisms for processing visual threat. Together, our results indicate that while the amygdala is primarily a detector of fearful faces, it has evolved to respond to other facial expressions that are also behaviorally relevant or potentially threatening to the viewer

Neural correlates of hand-tool interaction

Background: The recent advent of non-invasive functional magnetic resonance image (fMRI) has helped us understand how visual information is processed in the visual system, and the functional organising principles of high-order visual areas beyond striate cortex. In particular, evidence has been reported for a constellation of high-order visual areas that are highly specialised for the visual processing of different object domains such as faces, bodies, and tools. A number of accounts of the underlying principle of functional specialisation in high-order visual cortex propose that visual properties and object domain drive the category selectivity of these areas. However, recent evidence has challenged such accounts, showing that non-visual object properties and connectivity constraints between specialised brain networks can, in part, account for the visual system’s functional organisation. Methodology: Here I will use fMRI to examine how areas along the visual ventral stream and dorsal action stream process visually presented hands and tools. These categories are visually dissimilar but share similar functions. By using different statistical analyses, such as univariate group and single-subject region of interest (ROI) analyses, multivariate multivoxel pattern analyses, and functional connectivity analyses, I will investigate the topics of category-selectivity and the principles underlying the organisation of high-order visual areas in left occipitotemporal and left parietal cortex. Principle Findings: In the first part of this thesis I report novel evidence that, similar to socially relevant faces and bodies, the human high-order visual areas in left occipitotemporal and left parietal cortex houses areas that are selective for the visual processing of human hands. In the second part of this thesis, I show that the visual representation of hands and tools in these areas show large anatomical overlap and high similarity in the response patterns to these categories. As hands and tools differ in visual appearance and object domain yet share action-related properties, the results demonstrate that these category-selective responses in the visual system reflect responses to non-visual action-related object properties common to hands and tools rather than to purely visual properties or object domain. This proposition is further supported by evidence of selective functional connectivity patterns between hand/tool occipitotemporal and parietal areas. Conclusions/Significance: Overall these results indicate that high-order visual cortex is functionally organised to process both visual properties and non-visual object dimensions (e.g., action-related properties). I propose that this correspondence between hand and tool representations in ventral ‘visual’ and parietal ‘action’ areas is constrained by the necessity to connect visual object information to functionally-specific downstream networks (e.g., frontoparietal action network) to facilitate hand-tool action-related processing