Melbourne School of Psychological Sciences - Research Publications
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ItemVisual mismatch responses index surprise signalling but not expectation suppression( 2020-06-24)Abstract The ability to distinguish between commonplace and unusual sensory events is critical for efficient learning and adaptive behaviour. This has been investigated using oddball designs in which sequences of often-appearing (i.e. expected) stimuli are interspersed with rare (i.e. surprising) deviants. Resulting differences in electrophysiological responses following surprising compared to expected stimuli are known as visual mismatch responses (VMRs). VMRs are thought to index co-occurring contributions of stimulus repetition effects, expectation suppression (that occurs when one’s expectations are fulfilled), and expectation violation (i.e. surprise) responses; however, these different effects have been conflated in existing oddball designs. To better isolate and quantify effects of expectation suppression and surprise, we adapted an oddball design based on Fast Periodic Visual Stimulation (FPVS) that controls for stimulus repetition effects. We recorded electroencephalography (EEG) while participants (N=48) viewed stimulation sequences in which a single face identity was periodically presented at 6 Hz. Critically, one of two different face identities (termed oddballs) appeared as every 7th image throughout the sequence. The presentation probabilities of each oddball image within a sequence varied between 10-90%, such that participants could form expectations about which oddball face identity was more likely to appear within each sequence. We also included ‘expectation neutral’ 50% probability sequences, whereby consistently biased expectations would not be formed for either oddball face identity. We found that VMRs indexed surprise responses, and effects of expectation suppression were absent. That is, ERPs were more negative-going at occipitoparietal electrodes for surprising compared to neutral oddballs, but did not differ between expected and neutral oddballs. Surprising oddball-evoked ERPs were also highly similar across the 10-40% appearance probability conditions. Our findings indicate that VMRs which are not accounted for by repetition effects are best described as an all-or-none surprise response, rather than a minimisation of prediction error responses associated with expectation suppression. Highlights -We used a recently-developed oddball design that controls for repetition effects -We found effects of surprise but not expectation suppression on ERPs -Surprise responses did not vary by stimulus appearance probability
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ItemNo Preview AvailablePerceptual decision confidence is sensitive to forgone physical effort expenditure( 2020-06-10)Contemporary theoretical accounts of metacognition propose that action-related information is used in the computation of perceptual decision confidence. We investigated whether the amount of expended physical effort, or the ‘motoric sunk cost’ of a decision, influences perceptual decision confidence judgements in humans. In particular, we examined whether people feel more confident in decisions which required more effort to report. Forty-two participants performed a luminance discrimination task that involved identifying which of two flickering grayscale squares was brightest. Participants reported their choice by squeezing hand-held dynamometers. Across trials, the effort required to report a decision was varied across three levels (low, medium, high). Critically, participants were only aware of the required effort level on each trial once they had initiated their motor response, meaning that the varying effort requirements could not influence their initial decisions. Following each decision, participants rated their confidence in their choice. We found that participants were more confident in decisions that required greater effort to report. This suggests that humans are sensitive to motoric sunk costs and supports contemporary models of metacognition in which actions inform the computation of decision confidence.
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ItemAn initial ‘snapshot’ of sensory information biases the likelihood and speed of subsequent changes of mind( 2020-11-27)Abstract: We often need to rapidly change our mind about perceptual decisions in order to account for new information and correct mistakes. One fundamental, unresolved question is whether information processed prior to a decision being made (‘pre-decisional information’) has any influence on the likelihood and speed with which that decision is reversed. We investigated this using a luminance discrimination task in which participants indicated which of two flickering greyscale squares was brightest. Following an initial decision, the stimuli briefly remained on screen, and participants could change their response. Using psychophysical reverse correlation, we examined how moment-to-moment fluctuations in stimulus luminance affected participants’ decisions. This revealed that the strength of even the very earliest (pre-decisional) evidence was associated with the likelihood and speed of later changes of mind. To account for this effect, we propose an extended diffusion model in which an initial ‘snapshot’ of sensory information biases ongoing evidence accumulation. Author Summary: To avoid harm in an ever-changing world we need to be able to rapidly change our minds about our decisions. For example, imagine being unable to overrule a decision to run across a street when you realise a speeding car is approaching. In this study, we examined the information processing dynamics which underlie perceptual judgements and changes of mind. By reverse correlating participants decisions with the moment-to-moment sensory evidence they received, we show that the very earliest information, processed prior to an initial decision being made, can have a lasting influence over the speed and likelihood of subsequent changes of mind. To account for this, we develop a model of perceptual decisions in which initial sensory evidence exerts a lasting bias over later evidence processing. When fit to participants’ behavioural responses alone, this model predicted their observed information usage patterns. This suggests that an initial ‘snapshot’ of sensory information may influence the ongoing dynamics of the perceptual decision process, thus influencing the speed and likelihood of decision reversals.
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ItemDecoding Changes of Mind in Voluntary Action-Dynamics of Intentional Choice Representations(OXFORD UNIV PRESS INC, 2020-03)Voluntary actions rely on appropriate flexibility of intentions. Usually, we should pursue our goals, but sometimes we should change goals if they become too costly to achieve. Using functional magnetic resonance imaging, we investigated the neural dynamics underlying the capacity to change one's mind based on new information after action onset. Multivariate pattern analyses revealed that in visual areas, neural representations of intentional choice between 2 visual stimuli were unchanged by additional decision-relevant information. However, in fronto-parietal cortex, representations changed dynamically as decisions evolved. Precuneus, angular gyrus, and dorsolateral prefrontal cortex encoded new externally cued rewards/costs that guided subsequent changes of mind. Activity in medial frontal cortex predicted changes of mind when participants detached from externally cued evidence, suggesting a role in endogenous decision updates. Finally, trials with changes of mind were associated with an increase in functional connectivity between fronto-parietal areas, allowing for integration of various endogenous and exogenous decision components to generate a distributed consensus about whether to pursue or abandon an initial intention. In conclusion, local and global dynamics of choice representations in fronto-parietal cortex allow agents to maintain the balance between adapting to changing environments versus pursuing internal goals.
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ItemPredictions drive neural representations of visual events ahead of incoming sensory information(NATL ACAD SCIENCES, 2020-03-31)The transmission of sensory information through the visual system takes time. As a result of these delays, the visual information available to the brain always lags behind the timing of events in the present moment. Compensating for these delays is crucial for functioning within dynamic environments, since interacting with a moving object (e.g., catching a ball) requires real-time localization of the object. One way the brain might achieve this is via prediction of anticipated events. Using time-resolved decoding of electroencephalographic (EEG) data, we demonstrate that the visual system represents the anticipated future position of a moving object, showing that predictive mechanisms activate the same neural representations as afferent sensory input. Importantly, this activation is evident before sensory input corresponding to the stimulus position is able to arrive. Finally, we demonstrate that, when predicted events do not eventuate, sensory information arrives too late to prevent the visual system from representing what was expected but never presented. Taken together, we demonstrate how the visual system can implement predictive mechanisms to preactivate sensory representations, and argue that this might allow it to compensate for its own temporal constraints, allowing us to interact with dynamic visual environments in real time.
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ItemThe gamma model analysis (GMA): Introducing a novel scoring method for the shape of components of the event-related potential(ELSEVIER, 2020-04-01)BACKGROUND: Research using the event-related potential (ERP) method to investigate cognitive processes has usually focused on the analysis of either individual peaks or the area under the curve as components of interest. These approaches, however, do not analyse or describe the substantial variation in size and shape across the entire individual waveforms. NEW METHOD: Here we show that the precision of ERP analyses can be improved by fitting gamma functions to components of interest. Gamma model analyses provide time-dependent and shape-related information about the component, such as the component's rise and decline. We demonstrated the advantages of the gamma model analysis in a simulation study and in a two-choice response task, as well as a force production task. RESULTS: The gamma model parameters were sensitive to experimental variations, as well as variations in behavioural parameters. COMPARISON WITH EXISTING METHODS: Gamma model analyses provide researchers with additional reliable indicators about the shape of an ERP component's waveform, which previous analytical techniques could not. CONCLUSION: This approach, therefore, provides a novel toolset to better understand the exact relationship between ERP components, behaviour and cognition.
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ItemEmotion Regulation Modulates Dietary Decision-Making via Activity in the Prefrontal-Striatal Valuation System(OXFORD UNIV PRESS INC, 2020-11)The consumption of indulgent, carbohydrate- and fat-rich foods is often used as a strategy to cope with negative affect because they provide immediate self-reward. Such dietary choices, however, can severely affect people's health. One countermeasure could be to improve one's emotion regulation ability. We used functional magnetic resonance imaging to examine the neural activity underlying the downregulation of incidental emotions and its effect on subsequent food choices. We investigated whether emotion regulation leads to healthier food choices and how emotion regulation interacts with the brain's valuation and decision-making circuitry. We found that 1) the downregulation of incidental negative emotions was associated with a subsequent selective increase in decisions for tasty but also for healthy foods, 2) food preferences were predicted by palatability but also by the current emotional state, and 3) emotion regulation modulated decision-related activation in the ventromedial prefrontal cortex and ventral striatum. These results indicate that emotional states are indeed important for food choice and that the process of emotion regulation might boost the subsequent processing of health attributes, possibly via neural reward circuits. In consequence, our findings suggest that increasing emotion regulation ability could effectively modulate food choices by stimulating an incidental upvaluation of health attributes.
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ItemNo Preview AvailableNeural patterns during anticipation predict emotion regulation success for reappraisal(SPRINGER, 2020-08)The ability to exert control over emotions, termed emotion regulation (ER), is vital for everyday functioning. ER success may be influenced by processes relating to the anticipation (prior to active regulation) and implementation (during active regulation) of ER strategy use. We investigated whether brain activity patterns recorded using electroencephalography (EEG) during the first second of anticipation and implementation of two ER strategies-distraction and reappraisal-were related to regulation success. Participants viewed negative images that evoked disgust and sadness. Before each image was presented, participants were cued to either passively view the image or decrease their emotional responses. ER success scores were calculated from subsequent self-reported disgust and sadness ratings. Using multivariate support vector regression, ER success scores were predicted from spatiotemporal patterns of event-related potentials during the first second of anticipation and implementation phases of each ER strategy. For both sadness and disgust, reappraisal success could be predicted during anticipation, while distraction success could be predicted during implementation. These findings suggest that early anticipatory cognitive processes are a key determinant of reappraisal success, but may not be similarly important for distraction. This may be because reappraisal is more cognitively demanding than distraction, requiring enhanced preparation of mental resources.
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ItemMoral judgements of fairness-related actions are flexibly updated to account for contextual information(NATURE PORTFOLIO, 2020-10-20)In everyday life we are constantly updating our moral judgements as we learn new information. However, this judgement updating process has not been systematically studied. We investigated how people update their moral judgements of fairness-related actions of others after receiving contextual information regarding the deservingness of the action recipient. Participants (N = 313) observed a virtual 'Decision-maker' share a portion of $10 with a virtual 'Receiver'. Participants were aware that the Decision-maker made these choices knowing the Receiver's previous offer to another person. Participants first made a context-absent judgement of the Decision-maker's offer to the Receiver, and then a subsequent context-present judgement of the same offer after learning the Receiver's previous offer. This sequence was repeated for varying dollar values of Decision-makers' and Receivers' offers. Patterns of judgements varied across individuals and were interpretable in relation to moral norms. Most participants flexibly switched from relying on context-independent norms (generosity, equality) to related, context-dependent norms (relative generosity, indirect reciprocity) as they integrated contextual information. Judgement of low offers varied across individuals, with a substantial minority of participants withholding their context-absent judgements of selfishness, and another minority that was lenient towards selfishness across both judgements. Our paradigm provides a novel framework for investigating how moral judgements evolve in real time as people learn more information about a given situation.
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ItemOrientation-dependency of perceptual surround suppression and orientation decoding of centre-surround stimuli are preserved with healthy ageing(Elsevier BV, 2020-11)A key visual neuronal property that is mirrored in human behaviour is centre-surround contrast suppression, which is orientation-dependent. When a target is embedded in a high-contrast surround, the centre appears reduced in contrast, the magnitude of which depends on the relative orientation between centre and surround. Previous reports demonstrate changes in perceptual surround suppression with ageing; however, whether the orientation-dependency of surround suppression is impacted by ageing has not been explored. Here, we tested 18 younger (aged 19–33) and 18 older (aged 60–77) adults. Perceptual surround suppression was stronger for parallel than orthogonal stimuli; however contrary to previous work, here we found no difference in perceptual suppression strength between age-groups. In the same participants, we measured event-related potentials (ERPs) and conducted multivariate pattern analysis to confirm that parallel and orthogonal centre-surround stimuli elicit distinguishable brain activity, predominantly over occipital areas. Despite a delay in the first prominent ERP component (P1) in response to each pattern, older adults showed similar decoding of orientation information (i.e. distinguish between parallel and orthogonal centre-surround stimuli from 70 ms post-stimulus onset) as younger adults. This suggests that sufficient information to distinguish orientation in centre-surround stimuli becomes available to the older human brain as early as in younger adults.