A. Del Cul, S. Dehaene, P. Reyes, E. Bravo, A. Slachevsky
Article in Brain

Abstract
What neural mechanisms support our conscious perception of briefly presented stimuli? Some theories of conscious access postulate a key role of topdown amplification loops involving prefrontal cortex (PFC). To test this issue, we measured the visual backward masking threshold in patients with focal prefrontal lesions, using both objective and subjective measures while controlling for putative attention deficits. In all conditions of temporal or spatial attention cueing, the threshold for access to consciousness was systematically shifted in patients, particular after a lesion of the left anterior PFC. The deficit affected subjective reports more than objective performance, and objective performance conditioned on subjective visibility was essentially normal. We conclude that PFC makes a causal contribution to conscious visual perception of masked stimuli, and outline a dual-route signal detection theory of objective and subjective decision making.

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From the Dana Foundation: The Dana Foundation released at a news conference on March 4, Learning, Arts, and the Brain, a three-year study at seven universities, which finds strong links between arts education and cognitive development. Speakers included Michael Gazzaniga, Ph.D., UC, Santa Barbara; Michael Posner, Ph.D., University of Oregon;  Elizabeth Spelke, Ph.D., Harvard University  and Brian Wandell, Ph.D., Stanford University.  Guy Mckhann, M.D., Johns Hopkins University gave a summary and Dana Gioia, chairman of the National Endowment for the Arts spoke of the study’s importance to the field of education.

Click here for the webcast archive.

Click here for the event transcript.

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Christoph Börgers, Steven Epstein, and Nancy J. Kopell
Article in Proceedings of the National Academy of Science, USA

Abstract
Simultaneous presentation of multiple stimuli can reduce the firing rates of neurons in extrastriate visual cortex below the rate elicited by a single preferred stimulus. We describe computational results suggesting how this remarkable effect may arise from strong excitatory drive to a substantial local population of fast-spiking inhibitory interneurons, which can lead to a loss of coherence in that population and thereby raise the effectiveness of inhibition. We propose that in attentional states fast-spiking interneurons may be subject to a bath of inhibition resulting from cholinergic activation of a second class of inhibitory interneurons, restoring conditions needed for gamma rhythmicity. Oscillations and coherence are emergent features, not assumptions, in our model. The gamma oscillations in turn support stimulus competition. The mechanism is a form of “oscillatory selection,” in which neural interactions change phase relationships that regulate firing rates, and attention shapes those neural interactions.

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From NY Times (Oct 31, 2008):  The taste of a ripe tomato, the hook of a catchy song, the scent of a lover’s hair. What is it, exactly, that drives us to seek these things again and again?

Neuroscientists who study perception are starting to discover the inner workings of the sensory mind. Starting on Monday at the New York Academy of Sciences, researchers and artists will team up to explore this new research in a series of talks called Science of the Five Senses. Their conversations will raise a question for the amateur hedonist: If we had a better understanding of the signals our bodies send to our brains, might we take more pleasure from them? 

Click here for complete article.

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Heleen A. Slagter, Antoine Lutz, Lawrence L. Greischar, Sander Nieuwenhuis, and Richard J. Davidson.
Article in Journal of Cognitive Neuroscience

Abstract
The information processing capacity of the human mind is limited, as is evidenced by the attentional blink-a deficit in identifying the second of two targets (T1 and T2) presented in close succession. This deficit is thought to result from an overinvestment of limited resources in T1 processing. We previously reported that intensive mental training in a style of meditation aimed at reducing elaborate object processing, reduced brain resource allocation to T1, and improved T2 accuracy [Slagter, H. A., Lutz, A., Greisschar, L. L., Frances, A. D., Nieuwenhuis, S., Davis, J., et al. Mental training affects distribution of limited brain resources. PloS Biology, 5, e138, 2007]. Here we report EEG spectral analyses to examine the possibility that this reduction in elaborate T1 processing rendered the system more available to process new target information, as indexed by T2-locked phase variability. Intensive mental training was associated with decreased cross-trial variability in the phase of oscillatory theta activity after successfully detected T2s, in particular, for those individuals who showed the greatest reduction in brain resource allocation to T1. These data implicate theta phase locking in conscious target perception, and suggest that after mental training the cognitive system is more rapidly available to process new target information. Mental training was not associated with changes in the amplitude of T2-induced responses or oscillatory activity before task onset. In combination, these findings illustrate the usefulness of systematic mental training in the study of the human mind by revealing the neural mechanisms that enable the brain to successfully represent target information.

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Palva S, Palva JM.
Article in Trends in Neurosciences

Abstract
The amplitude of alpha-frequency band (8-14 Hz) activity in the human electroencephalogram is suppressed by eye opening, visual stimuli and visual scanning, whereas it is enhanced during internal tasks, such as mental calculation and working memory. Alpha-frequency band oscillations have hence been thought to reflect idling or inhibition of task-irrelevant cortical areas. However, recent data on alpha-amplitude and, in particular, alpha-phase dynamics posit a direct and active role for alpha-frequency band rhythmicity in the mechanisms of attention and consciousness. We propose that simultaneous alpha-, beta- (14-30 Hz) and gamma- (30-70 Hz) frequency band oscillations are required for unified cognitive operations, and hypothesize that cross-frequency phase synchrony between alpha, beta and gamma oscillations coordinates the selection and maintenance of neuronal object representations during working memory, perception and consciousness.

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Antoine Lutz, Heleen A. Slagter, John D. Dunne and Richard J. Davidson
Review article in Trends in Cognitive Sciences, click here for full article

Abstract:
Meditation can be conceptualized as a family of complex emotional and attentional regulatory training regimes developed for various ends, including the cultivation of well-being and emotional balance. Among these various practices, there are two styles that are commonly studied. One style, focused attention meditation, entails the voluntary focusing of attention on a chosen object. The other style, open monitoring meditation, involves nonreactive monitoring of the content of experience from moment to moment. The potential regulatory functions of these practices on attention and emotion processes could have a long-term impact on the brain and behavior.

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In a recent study, Mika Koivisto and Antti Revonsuo compared the timing and mechanisms of attentional blink (AB) and repetition blindness (RB) directly during the same rapid serial visual presentation stream to examine the relation between the two phenomena.  To do so, they recorded electrophysiological responses over the scalp (EEG, ERP) to repeated and unrepeated targets.

The authors report the following findings:

Comparable to earlier ERP studies on visual awareness, the results showed for both types of targets a negative amplitude difference between ERPs to consciously recognized and unrecognized targets during 250-350 ms from stimulus onset, suggesting that both AB and RB are associated with deficits of conscious perception, occurring at earlier stages than access to working memory. However, the perceptual deficit in RB is more severe, which may be related to higher overall negativity in response to repeated targets observed 150-300 ms after stimulus onset, suggesting stronger cortical baseline activation and higher perceptual threshold for repeated targets as compared with unrepeated ones.

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Abstract of Attention and consciousness: two distinct brain processes, in TRENDS in Cognitive Sciences.

The close relationship between attention and consciousness has led many scholars to conflate these processes. This article summarizes psychophysical evidence, arguing that top-down attention and consciousness are distinct phenomena that need not occur together and that can be manipulated using distinct paradigms. Subjects can become conscious of an isolated object or the gist of a scene despite the near absence of top-down attention; conversely, subjects can attend to perceptually invisible objects. Furthermore, top-down attention and consciousness can have opposing effects. Such dissociations are easier to understand when the different functions of these two processes are considered. Untangling their tight relationship is necessary for the scientific elucidation of consciousness and its material substrate.

For full access to this paper, click here.

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By Rachel Jones

Our sensory system is constantly bombarded with inputs, but owing to the brain’s finite processing power, we are forced to pay attention to only a tiny proportion of these inputs at any given time. In a new study, Richard Davidson and colleagues report [in PLoS Biology] that intensive training in meditation can alter the way in which the brain allocates attentional resources to important stimuli, allowing people to improve their performance on a demanding visual task.

In the “attentional blink” task, volunteers were asked to identify two “target” stimuli—for example, two particular numbers—in a stream of rapidly presented “non-target” stimuli—for example, letters—which are irrelevant to the task. When the first target number appears on the screen, it captures the attention of the subject, and this can prevent the person from spotting the second target if it appears within around half a second of the first (the attentional blink). It is as if the brain is so busy processing the first target that it can’t also process the second, and therefore the second target goes unnoticed. However, the attentional blink does not represent a structural processing bottleneck. Most subjects are able to spot the second target on at least a small proportion of trials. Since this task gauges the ability of subjects to allocate cognitive resources efficiently when multiple stimuli compete for attention, it is perfectly suited for investigations of the effects of mental training on attention.

Read full story at PLoS Biology

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Attention helps us process potentially important objects by selectively increasing the activity of sensory neurons that represent the relevant locations and features of our environment. This selection process requires top-down feedback about what is important in our environment. We investigated how parietal cortical output influences neural activity in early sensory areas. Neural recordings were made simultaneously from the posterior parietal cortex and an earlier area in the visual pathway, the medial temporal area, of macaques performing a visual matching task. When the monkey selectively attended to a location, the timing of activities in the two regions became synchronized, with the parietal cortex leading the medial temporal area. Parietal neurons may thus selectively increase activity in earlier sensory areas to enable focused spatial attention.

Science

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Do your thoughts stray from your work or studies? Do you catch yourself making to-do lists when your attention should be elsewhere? Welcome to the club.

College students reported mind-wandering almost one-third of the time in their daily lives, according to a new study led by faculty and graduate students at The University of North Carolina at Greensboro. The study will be published in the July issue of Psychological Science.

The study followed 124 undergraduates, who carried personal digital assistants for a week. The PDAs signaled the students eight times a day between noon and midnight to report whether their thoughts were wandering away from what they were doing and to answer multiple-choice questions about their current activity, surroundings and state of mind.

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Would we hear things differently if we always kept our eyes closed? The answer is yes! The McGurk Effect is a classic illustration of how the spoken sounds we hear are influenced by whether or not we can see the speaker’s lips.

Click here for a great online example of the McGurk Effect. In this online example, we see a person saying (making lip movements for) “GA GA”, but in reality, we are hearing “BA BA”. When these sounds and lip movements are combined, most adults think that they are hearing “DA DA”.

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Abstract of The Multi-Source Interference Task: an fMRI task that reliably activates the cingulo-frontal-parietal cognitive/attention network, in Nature.

In this protocol we describe how to perform the Multi-Source Interference Task (MSIT), a validated functional magnetic resonance imaging (fMRI) task that reliably and robustly activates the cingulo-frontal-parietal cognitive/attention network (CFP network) within individual subjects. The MSIT can be used to (i) identify the cognitive/attention network in normal volunteers and (ii) test its integrity in people with neuropsychiatric disorders. It is simple to perform, can be completed in less than 15 min and is not language specific, making it appropriate for children, adults and the elderly. Since its validation, over 100 adults have performed the task. The MSIT produces a robust and temporally stable reaction time interference effect (range 200–350 ms), and single runs of the MSIT have produced CFP network activation in approximately 95% of tested subjects. The robust, reliable and temporally stable neuroimaging and performance data make the MSIT a useful task with which to study normal human cognition and psychiatric pathophysiology.

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