The unconscious mind: From classical theoretical controversy to controversial contemporary research and a practical illustration of the “error of our ways”

In this manuscript, the authors present an overview of the history, an account of the theoretical and methodological controversy, and an illustration of contemporary and revised methods for the exploration of unconscious processing. Initially we discuss historical approaches relating to unconsciousness that are, arguably, defamed and considered extraneous to contemporary psychological research. We support that awareness of the history of the current subject is pedagogically essential to understand the transition to empirical research and the reasons for which the current area is still so contentious among contemporary psychologists. We proceed to explore the current experimental canon. Contemporary theoretical and methodological issues relating to unconscious processing are discussed in detail and key issues and key advancements in contemporary research are presented. Developments that have, in recent years, being suggested to contribute to a possibly reliable method for the assessment of unconscious processing are practically - methodologically and statistically – illustrated using easy-to-follow steps applied in real experimental data. Mindful of our own place in the long history of this topic, we conclude the manuscript with suggestions concerning the future of the current area

Cortical activity reduction with stimulus repetition: A whole-head MEG analysis

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Distractor-resistant short-term memory is supported by transient changes in neural stimulus representations

Goal-directed behavior in a complex world requires the maintenance of goal-relevant information despite multiple sources of distraction. However, the brain mechanisms underlying distractor-resistant working or short-term memory (STM) are not fully understood. While early single-unit recordings in monkeys and fMRI studies in humans pointed to an involvement of lateral prefrontal cortices, more recent studies highlighted the importance of posterior cortices for the active maintenance of visual information also in the presence of distraction. Here, we used a delayed match-to-sample task and multivariate searchlight analyses of fMRI data to investigate STM maintenance across three extended delay phases. Participants maintained two samples (either faces or houses) across an unfilled pre-distractor delay, a distractor-filled delay, and an unfilled post-distractor delay. STM contents (faces vs. houses) could be decoded above-chance in all three delay phases from occipital, temporal, and posterior parietal areas. Classifiers trained to distinguish face vs. house maintenance successfully generalized from preto post-distraction delays and vice versa, but not to the distractor delay period. Furthermore, classifier performance in all delay phases was correlated with behavioral performance in house, but not face trials. Our results demonstrate the involvement of distributed posterior, but not lateral prefrontal, cortices in active maintenance during and after distraction. They also show that the neural code underlying STM maintenance is transiently changed in the presence of distractors, and re instated after distraction. The correlation with behavior suggests that active STM maintenance is particularly relevant in house trials, whereas face trials might rely more strongly on contributions from long-term memory

Neural origins of human sickness in interoceptive responses to inflammation

BACKGROUND: Inflammation is associated with psychological, emotional, and behavioral disturbance, known as sickness behavior. Inflammatory cytokines are implicated in coordinating this central motivational reorientation accompanying peripheral immunologic responses to pathogens. Studies in rodents suggest an afferent interoceptive neural mechanism, although comparable data in humans are lacking. METHODS: In a double-blind, randomized crossover study, 16 healthy male volunteers received typhoid vaccination or saline (placebo) injection in two experimental sessions. Profile of Mood State questionnaires were completed at baseline and at 2 and 3 hours. Two hours after injection, participants performed a high-demand color word Stroop task during functional magnetic resonance imaging. Blood samples were performed at baseline and immediately after scanning. RESULTS: Typhoid but not placebo injection produced a robust inflammatory response indexed by increased circulating interleukin-6 accompanied by a significant increase in fatigue, confusion, and impaired concentration at 3 hours. Performance of the Stroop task under inflammation activated brain regions encoding representations of internal bodily state. Spatial and temporal characteristics of this response are consistent with interoceptive information flow via afferent autonomic fibers. During performance of this task, activity within interoceptive brain regions also predicted individual differences in inflammation-associated but not placebo-associated fatigue and confusion. Maintenance of cognitive performance, despite inflammation-associated fatigue, led to recruitment of additional prefrontal cortical regions. CONCLUSIONS: These findings suggest that peripheral infection selectively influences central nervous system function to generate core symptoms of sickness and reorient basic motivational states. PMID:19409533[PubMed - indexed for MEDLINE] PMCID: PMC2885492Free PMC Articl

Shared and selective neural correlates of inhibition, facilitation, and shifting processes during executive control

A network of prefrontal and parietal regions has been implicated in executive control processes. However, the extent to which individual regions within this network are engaged in component control processes, such as inhibition of task-irrelevant stimulus attributes or shifting (switching) between attentional foci, remains controversial. Participants (N = 17) underwent functional magnetic resonance imaging while performing a global–local task in which the global and local levels could facilitate or interfere with one another. Stimuli were presented in blocks in which participants either constantly shifted between the global and local levels, or consistently responded to one level only. Activations related to inhibition and shifting processes were observed in a large network of bilateral prefrontal, parietal, and basal ganglia regions. Region of interest analyses were used to classify each region within this network as being common to inhibition and shifting, or preferential to one component process. Several regions were classified as being preferential to inhibition, including regions within the dorsolateral and ventrolateral prefrontal cortex, the parietal lobes, and the temporal–parietal junction. A limited set of regions in the parietal lobes and left dorsolateral prefrontal cortex were classified as preferential to shifting. There was a very large set of regions displaying activation common to both inhibition and shifting processes, including regions within the dorsolateral prefrontal cortex, anterior cingulate, and basal ganglia. Several of these common regions were also involved during facilitation, suggesting that they are responsive to the number of task-salient channels of information, rather than purely to demands on control processes.National Institute of Mental Health (U.S.) (MH061426)National Institute on Aging (AG021847

Executive deficits are related to the inferior frontal junction in early dementia

Executive functions describe a wide variety of higher order cognitive processes that allow the flexible modification of thought and behaviour in response to changing cognitive or environmental contexts. Their impairment is common in neurodegenerative disorders. Executive deficits negatively affect everyday activities and hamper the ability to cope with other deficits, such as memory impairment in Alzheimer's disease or behavioural disorders in frontotemporal lobar degeneration. Our study aimed to characterize the neural correlates of executive functions by relating respective deficits to regional hypometabolism in early dementia. Executive functions were assessed with two classical tests, the Stroop and semantic fluency test and various subtests of the behavioural assessment of the dysexecutive syndrome test battery capturing essential aspects of executive abilities relevant to daily living. Impairments in executive functions were correlated with reductions in brain glucose utilization as measured by [18F]fluorodeoxyglucose positron emission tomography and analysed voxelwise using statistical parametric mapping in 54 subjects with early dementia, mainly Alzheimer's disease and frontotemporal lobar degeneration, and its prodromal stages: subjective and mild cognitive impairment. Although the analysis revealed task-specific frontoparietal networks, it consistently showed that hypometabolism in one region in the left lateral prefrontal cortex—the inferior frontal junction area—was related to performance in the various neuropsychological tests. This brain region has recently been related to the three component processes of cognitive control—working memory, task switching and inhibitory control. Group comparisons additionally showed hypometabolism in this area in Alzheimer's disease and frontotemporal lobar degeneration. Our study underlines the importance of the inferior frontal junction area for cognitive control in general and for executive deficits in early dementia