One way to describe brain activity measured by EEG or MEG is by its frequency content. Frequencies can be categorized into one of the following ranges: low, middle and high. The low frequencies include the delta and theta ranges, whereas the middle frequency range consists of the alpha and beta ranges. The gamma wave belongs to the high frequency group.

Different cognitive functions have been associated with these different frequency ranges. Specifically, alpha oscillations have been associated with the inhibition of brain regions that are not required to perform a given task. However, in a past paper, Palva and Palva summarized an accumulating body of evidence that suggested that alpha oscillations play a much larger role in cognition by contributing to mechanisms of attention and consciousness. Click here for full access to the paper.

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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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Meditation can be conceptualized as a complex form of attentional and emotional training that promotes well-being and emotional balance.  In most meditation traditions, a common practice is to focus one’s attention to internal body sensations, and many traditions state that this practice results in an increased awareness of internal body sensations.  In a study by Khalsa and colleagues, two groups of meditators (Tibetan Buddhist and Kundalini) were compared to a group of nonmeditators on their ability to detect their own heartbeat.  (The meditators and nonmeditators were matched for age and body mass index.)  Although the investigators predicted that the experienced meditators would outperform the nonmeditators, no such evidence was found.  Compared to the nonmeditators, however, the experienced meditators consistently rated the difficulty of the heartbeat detection task as easier and their interoceptive performance as superior.  These results suggest that the practice of focusing one’s attention to internal body sensations (a core feature of meditation) does not enhance the ability to sense the heartbeat at rest, but it alters the subjective experience of it.

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Mitchell F Roitman, Robert A Wheeler, R Mark Wightman and Regina M Carelli
Article in Nature Neuroscience

Abstract
Rewarding and aversive stimuli evoke very different patterns of behavior and are rapidly discriminated. Here taste stimuli of opposite hedonic valence evoked opposite patterns of dopamine and metabolic activity within milliseconds in the nucleus accumbens. This rapid encoding may serve to guide ongoing behavioral responses and promote plastic changes in underlying circuitry.

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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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Neuropsychologia hosts a special issue in relation to the work of Larry Weiskrantz. It contains a densely packed number of articles on the topic of blindsight and hindsights.

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Time is an important dimension when individuals make decisions. Specifically, the time until a beneficial outcome can be received is viewed as a cost and is weighed against the benefits of the outcome.

We propose that impulsive individuals experience time differently, that is with a higher cost. Impulsive subjects, therefore, overestimate the duration of time intervals and, as a consequence, discount the value of delayed rewards more strongly than do self-controlled individuals.

The literature on time perception and impulsivity, however, is not clear cut and needs a better theoretical foundation. Here, we develop the theoretical background on concepts of time perception, which could lead to an empirically based notion of the association between an altered sense of time and impulsivity.

Article by Marc Wittmann and Martin P. Paulus in Trends in Cognitive Sciences, Volume 12, Issue 1, January 2008, Pages 13-16

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From physorg.com — Following ground-breaking research showing that neurons in the human brain respond in an abstract manner to particular individuals or objects, University of Leicester researchers have now discovered that, from the firing of this type of neuron, they can tell what a person is actually seeing.

The original research by Dr R Quian Quiroga, of the University’s Department of Engineering, showed that one neuron fired to, for instance, Jennifer Aniston, another one to Halle Berry, another one to the Sydney Opera House, etc. The responses were abstract. For example, the neuron firing to Halle Berry responded to several different pictures of her and even to the letters of her name, but not to other people or names.

This result, published in Nature in 2005 and selected as one of the top 100 scientific stories of the year by Discover Magazine, came from data from patients suffering from epilepsy. As candidates for epilepsy surgery, they are implanted with intracranial electrodes to determine as accurately as possible the area where the seizures originate. From that, clinicians can evaluate the potential outcome of curative surgery.

Dr Quian Quiroga’s latest research, which has appeared in the Journal of Neurophysiology, follows on from this. Dr Quian Quiroga explained:

“For example, if the ‘Jennifer Aniston neuron’ increases its firing then we can predict that the subject is seeing Jennifer Aniston. If the ‘Halle Berry neuron’ fires, then we can predict that the subject is seeing Halle Berry, and so on. “To do this, we used and optimised a ‘decoding algorithms’, which is a mathematical method to infer the stimulus from the neuronal firing. We also needed to optimise our recording and data processing tools to record simultaneously from as many neurons as possible. Currently we are able to record simultaneously from up to 100 neurons in the human brain.

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From physorg.com — Anyone who has bonded with a puppy madly sniffing with affection gets an idea of how scents, most not apparent to humans, are critical to a dog’s appreciation of her two-legged friends. Now new research from Northwestern University suggests that humans also pick up infinitesimal scents that affect whether or not we like somebody. “We evaluate people every day and make judgments about who we like or don’t like,” said Wen Li, a post-doctoral fellow in the Cognitive Neurology and Alzheimer’s Disease Center at Northwestern’s Feinberg School of Medicine and lead author of the study. “We may think our judgments are based only on various conscious bits of information, but our senses also may provide subliminal perceptual information that affects our behavior.”

“Subliminal Smells Can Guide Social Preferences” was published in the December issue of Psychological Science. Besides Li, the
study’s co-investigators include Isabel Moallem, Loyola University; Ken Paller, professor of psychology in the Weinberg College of Arts and Sciences at Northwestern; and Jay Gottfried, assistant professor of neurology at Feinberg and senior author of the paper.

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Our sense of time is altered by our emotions to such an extent that time seems to fly when we are having fun and drags when we are bored. Recent studies using standardized emotional material provide a unique opportunity for understanding the neurocognitive mechanisms that underlie the effects of emotion on timing and time perception in the milliseconds-to-hours range.

We outline how these new findings can be explained within the framework of internal-clock models and describe how emotional arousal and valence interact to produce both increases and decreases in attentional time sharing and clock speed. The study of time and emotion is at a crossroads, and we outline possible examples for future directions

Article by Sylvie Droit-Volet & Warren H. Meck in Trends in Cognitive Sciences, Volume 11, Issue 12, December 2007, Pages 504-513

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This is  probably one of the best illusions ever! Please do the following: look at the above images from your seat in front of the computer; Mr. Angry is on the left, and Ms.Calm is on the right. Now, get up from your seat, and move back 10 or 12 feet. Who’s the angry and calm now?

It’s said that this illusion was made by Phillippe G.Schyns and Aude Oliva. Cudos to Robert Karl Stonjek for showing us this illusion.

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From Mind hacks: The BPS Research Digest has discussed a recent study that analysed recordings of parapsychology experiments and has found that some of the positive findings may be due to experimenters unconsciously prompting the participants as they gave their answers.The experiments used the Ganzfeld technique where one participant has diffuse white light and auditory noise played to them, effectively blocking the key senses, while another tries to ’send’ images to them through mental projection.

Afterwards, the ‘receiver’ tells the experimenter what images came to mind and the research team see if it matches what the ’sender’ was trying to transmit.

Taken as a whole, these sorts of experiments show a weak but positive evidence for extra-sensory perception (ESP), but it’s not clear whether this isn’t just due to a tendency for some negative trials not being reported.

In this new study, psychologist Robin Woofit analysed the tapes of Ganzfeld experiments from the mid-1990s and found that experimenters were more likely to respond decisively to correct responses but give subtle cues (such as saying ‘mm hm’) to give more information when the response wasn’t initially accurate.

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PLOS Biology has a most interesting article from Stanislas Dehaene’s group on the neurodynamics of conscious experience. The researchers studied brain activation using EEG, while subjects rated visually presented stimuli on a scale from unseen to clearly seen. It was found that conscious experience of a stimulus was related to the engagement of a widespread network involving the frontal, parietal and temporal cortices.

SCR note: It is mentioning a recent study using fMRI (Christensen et al. 2006) provided comparable results, and adding two factors; (1) the conscious experience of a visual stimulus involved activation of both thalami, and (2) subjects consistently rated some experiences as vague, i.e., as “detected but not identified”. This experience was associated with both lower activation in those regions involved in conscious experience, and unique activation of additional regions, including some prefrontal regions.

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Melloni et al. have recently demonstrated, in the Journal of Neuroscience, that neural synchrony in the gamma range between distal rain regions is important for conscious perception. The authors say about their work that “the access to conscious perception is the early transient global increase of phase synchrony of oscillatory activity in the gamma frequency range”

Here we link to the article and some related works.

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