Dreaming and the brain: toward a cognitive neuroscience of conscious states

Sleep researchers in different disciplines disagree about how fully dreaming can be explained in terms of brain physiology. Debate has focused on whether REM sleep dreaming is qualitatively different from nonREM (NREM) sleep and waking. A review of psychophysiological studies shows clear quantitative differences between REM and NREM mentation and between REM and waking mentation. Recent neuroimaging and neurophysiological studies also differentiate REM, NREM, and waking in features with phenomenological implications. Both evidence and theory suggest that there are isomorphisms between the phenomenology and the physiology of dreams. We present a three-dimensional model with specific examples from normally and abnormally changing conscious states.     

Changes in acetylcholine extracellular levels during cognitive processes

Measuring the changes in neurotransmitter extracellular levels in discrete brain areas is considered a tool for identifying the neuronal systems involved in specific behavioral responses or cognitive processes. Acetylcholine (ACh) is the first neurotransmitter whose diffusion from the central nervous system was investigated and whose extracellular levels variations were correlated to changes in neuronal activity. This was done initially by means of the cup technique and then by the microdialysis technique. The latter, notwithstanding some technical limitations, makes it possible to detect variations in extracellular levels of ACh in unrestrained, behaving animals. This review summarizes and discusses the results obtained investigating the changes in ACh release during performance of operant tasks, exposition to novel stimuli, locomotor activity, and the performance of spatial memory tasks, working memory, and place preference memory tasks. Activation of the forebrain cholinergic system has been demonstrated in many tasks and conditions in which the environment requires the animal to analyze novel stimuli that may represent a threat or offer a reward. The sustained cholinergic activation, demonstrated by high levels of extracellular ACh observed during the behavioral paradigms, indicates that many behaviors occur within or require the facilitation provided by the cholinergic system to the operation of pertinent neuronal pathways.     

Meditation-specific prefrontal cortical activation during acem meditation: an fMRI study

Some of the most popular meditation practices emphasize a relaxed focus of attention in which thoughts, images, sensations, and emotions may emerge and pass freely without actively controlling or pursuing them. Several recent studies show that meditation activates frontal brain areas associated with attention focusing and physical relaxation. The objective of the present study was to assess whether brain activation during relaxed focusing on a meditation sound could be distinguished from similar, concentrative control tasks. Brain activation was measured with functional magnetic resonance imaging (fMRI) in experienced practitioners of Acem meditation. Bilateral areas of the inferior frontal gyrus (BA47) were significantly more activated during repetition of a meditation sound than during concentrative meditation-like cognitive tasks. Meditation-specific brain activation did not habituate over time, but increased in strength with continuous meditation bouts. These observations suggest that meditation with a relaxed focus of attention may activate distinct areas of the prefrontal cortex, with implications for the understanding of neurobiological correlates of meditation.     

Postencoding cognitive processes in the cross-race effect: Categorization and individuation during face recognition

The cross-race effect (CRE) describes the finding that same-race faces are recognized more accurately than cross-race faces. According to social–cognitive theories of the CRE, processes of categorization and individuation at encoding account for differential recognition of same- and cross-race faces. Recent face memory research has suggested that similar but distinct categorization and individuation processes also occur postencoding, at recognition. Using a divided-attention paradigm, in Experiments 1A and 1B we tested and confirmed the hypothesis that distinct postencoding categorization and individuation processes occur during the recognition of same- and cross-race faces. Specifically, postencoding configural divided-attention tasks impaired recognition accuracy more for same-race than for cross-race faces; on the other hand, for White (but not Black) participants, postencoding featural divided-attention tasks impaired recognition accuracy more for cross-race than for same-race faces. A social categorization paradigm used in Experiments 2A and 2B tested the hypothesis that the postencoding in-group or out-group social orientation to faces affects categorization and individuation processes during the recognition of same-race and cross-race faces. Postencoding out-group orientation to faces resulted in categorization for White but not for Black participants. This was evidenced by White participants’ impaired recognition accuracy for same-race but not for cross-race out-group faces. Postencoding in-group orientation to faces had no effect on recognition accuracy for either same-race or cross-race faces. The results of Experiments 2A and 2B suggest that this social orientation facilitates White but not Black participants’ individuation and categorization processes at recognition. Models of recognition memory for same-race and cross-race faces need to account for processing differences that occur at both encoding and recognition.     

Accessing the Eternal: Dreaming "The Dreaming" and Ceremonial Performance

Australian Aboriginal cosmology is centered on The Dreaming, which has an eternal nature. It has been referred to as “everywhen” to articulate its timelessness. Starting with the assumption that “waking” reality is only one type of experienced reality, we investigate the concept of timelessness as it pertains to the Aboriginal worldview. We begin by questioning whether in fact “Dreaming” is an appropriate translation of a complex Aboriginal concept, then discuss whether there is any relationship between dreaming and The Dreaming. We then discuss Aboriginal ceremonial performance, during which actors are said to become Dreaming Ancestors, using as a frame of reference the “flow” experience explicated by Mihaly Csikszentmihalyi together with Alfred Schutz's “mutual tuning‐in relationship.”     

Eye fixations and cognitive processes

This paper presents a theoretical account of the sequence and duration of eye fixation during a number of simple cognitive tasks, such as mental rotation, sentence verification, and quantitative comparison. In each case, the eye fixation behavior is linked to a processing model for the task by assuming that the eye fixates the referent of the symbol being operated on.     

Ability factors and cognitive processes

Several measures of the speed of information processing were related to ability factors derived from the Cattell-Horn theory of fluid and crystallized intelligence. Ninety-one college students took a battery of paper and pencil tests designed to measure four ability factors: fluid intelligence (Gf), crystallized intelligence (Gc), spatial visualization (Gv), and clerical perceptual speed (CPS). They also performed paper and pencil and computerized versions of three information processing tasks: mental rotations, letter matching, and sentence verification. Correlations among the ability measures, among the information processing measures, and between the two domains were analyzed using confirmatory factor analysis. The four ability factors were found to be largely independent in this college population. Speed of letter-matching and sentence verification were highly correlated, but neither was related to speed of mental rotation. Mental rotation speed was strongly correlated with Gv; letter matching speed was correlated with CPS; and sentence verification speed was correlated with both Gc and CPS.     

Synchronous neural oscillations and cognitive processes

The central problem for cognitive neuroscience is to describe how cognitive processes arise from brain processes. This review summarizes the recent evidence that synchronous neural oscillations reveal much about the origin and nature of cognitive processes such as memory, attention and consciousness. Memory processes are most closely related to theta and gamma rhythms, whereas attention seems closely associated with alpha and gamma rhythms. Conscious awareness may arise from synchronous neural oscillations occurring globally throughout the brain rather than from the locally synchronous oscillations that occur when a sensory area encodes a stimulus. These associations between the dynamics of the brain and cognitive processes indicate progress towards a unified theory of brain and cognition.     

Reaching while calculating: scheduling of cognitive and perceptual-motor processes

To address the neglected question of how cognitive and perceptual-motor processes are coordinated, the authors asked participants to move a cursor from one target to another to reveal operators and operands for a running arithmetic task. In Experiment I performance on this task was compared with performance on tasks requiring only aiming or only arithmetic. Aiming was faster in the aiming-only task than in the combined task. More importantly, times for steps requiring calculation were equivalent in the combined and arithmetic-only tasks. The results from this and a second experiment suggest that participants slowed their aiming to allow calculations to be completed before subsequent targets were entered. As a whole, the results suggest that cognitive and perceptual-motor processes are coordinated through scheduling.     

Stress modulation of cognitive and affective processes

This review summarizes the major discussion points of a symposium on stress modulation of cognitive and affective processes, which was held during the 2010 workshop on the neurobiology of stress (Boulder, CO, USA). The four discussants addressed a number of specific cognitive and affective factors that are modulated by exposure to acute or repeated stress. Dr David Morilak discussed the effects of various repeated stress situations on cognitive flexibility, as assessed with a rodent model of attentional set-shifting task, and how performance on slightly different aspects of this test is modulated by different prefrontal regions through monoaminergic neurotransmission. Dr Serge Campeau summarized the findings of several studies exploring a number of factors and brain regions that regulate habituation of various autonomic and neuroendocrine responses to repeated audiogenic stress exposures. Dr Kerry Ressler discussed a body of work exploring the modulation and extinction of fear memories in rodents and humans, especially focusing on the role of key neurotransmitter systems including excitatory amino acids and brain-derived neurotrophic factor. Dr Israel Liberzon presented recent results on human decision-making processes in response to exogenous glucocorticoid hormone administration. Overall, these discussions are casting a wider framework on the cognitive/affective processes that are distinctly regulated by the experience of stress and some of the brain regions and neurotransmitter systems associated with these effects.     

Dreaming and waking: similarities and differences revisited

Dreaming is often characterized as lacking high-order cognitive (HOC) skills. In two studies, we test the alternative hypothesis that the dreaming mind is highly similar to the waking mind. Multiple experience samples were obtained from late-night REM sleep and waking, following a systematic protocol described in Kahan (2001). Results indicated that reported dreaming and waking experiences are surprisingly similar in their cognitive and sensory qualities. Concurrently, ratings of dreaming and waking experiences were markedly different on questions of general reality orientation and logical organization (e.g., the bizarreness or typicality of the events, actions, and locations). Consistent with other recent studies (e.g., [Bulkeley and Kahan, 2008] and [Kozmová and Wolman, 2006] ), experiences sampled from dreaming and waking were more similar with respect to their process features than with respect to their structural features.     

Correlates of Canadian native children's reading performance: From cognitive styles to cognitive processes

Individual differences in reading and cognitive processing among a sample of generally poor readers were studied in order to answer two major questions: Do they have a specific cognitive style that favors global-simultaneous strategies and a weak sequential strategy? If they do not have a distinct cognitive style or strategy, but are merely poor in using sequential (Successive) strategies, then, would the same processes that influence reading performance in the general population determine their performance as well? A sample of 84 Canadian First Nations (FN) children were assessed in word and pseudoword reading, rapid naming speed, and ability to process information using the Planning, Attention, Successive, and Simultaneous (PASS) theory of intelligence. Results confirmed that this sample of children did not exhibit a specific cognitive style. Rather, there was evidence of a weakness in Successive processing only in the subgroup of poor readers. The importance of understanding the role of Successive processing and rapid naming speed relative to reading is further discussed.     

Motivation towards closure and cognitive processes: An individual differences approach

Two studies (N = 212) examined the relationships between elementary cognitive processes and individual differences in the need for cognitive closure. The results indicated that the need for closure is linked with certain cognitive deficits, specifically a restricted pool of cognitive resources allocated to a current activity. It was also found that these cognitive limitations tend to be compensated for by a particularly efficient process of information-selection from the environment. However, the selection process is costly, thus in a situation of drainage of cognitive resources its effectiveness also drops and the selection advantage of high (vs. low) need for closure individuals is eliminated.     

Perfectionism: A contributor to social anxiety and its cognitive processes

The present study aimed to examine how perfectionism is contributing to social anxiety and its cognitive processes of post‐event rumination and self‐perception of performance following a speech task. Forty‐eight undergraduate students completed measures of perfectionism and trait social anxiety prior to performing a 3‐min impromptu speech task. Immediately following the speech task, participants rated their state anxiety and self‐perception of performance, and 24 hr later, their level of post‐event rumination was measured. Structural equation modelling revealed that perfectionism, in the form of socially prescribed perfectionism and doubts about actions, directly influences trait social anxiety, and indirectly influences post‐event rumination and self‐perception of performance through its relationship with trait social anxiety and state anxiety. This is the first study to investigate how perfectionism is contributing to social anxiety and its cognitive processes. The findings of this study provide evidence in support of the potential predictive role of perfectionism in social anxiety.     

Visuo-spatial imagery impairment in posterior cortical atrophy: a cognitive and SPECT study

This study investigated the cognitive profile and the cerebral perfusion pattern in a highly educated 70 year old gentleman with posterior cortical atrophy (PCA). Visuo-perceptual abilities, spatial memory, spatial representation and navigation, visuo-spatial mental imagery, semantic and episodic-autobiographical memory were assessed. Regional cerebral blood flow (rCBF) was imaged with SPECT. Cognitive testing showed visual-perceptual impairment, apperceptive visual and landmark agnosia, topographical disorientation with way-finding deficits, impaired map learning and poor mental image generation. Semantic memory was normal, while episodic-autobiographical memory was impaired. Reduced rCBF was found mainly in the right hemisphere, in the precentral gyrus, posterior cingulate and middle temporal gyri, cuneus and precuneus, in the left superior temporal and lingual gyri and in the parahippocampus bilaterally. Hypoperfusion in occipito-parietal regions was associated with visuo-spatial deficits, whereas deficits in visuo-spatial mental imagery might reflect dysfunction related to hypoperfusion in the parahippocampus and precuneus, structures which are responsible for spatial and imagery processing. Dissociating performance between preserved semantic memory and poor episodic-autobiographical recall is consistent with a pattern of normal perfusion in frontal and anterior temporal regions but abnormal rCBF in the parahippocampi. The present findings indicate that PCA involves visuo-spatial imagery deficits and provide further validation to current neuro-cognitive models of spatial representation and topographical disorientation.