October 5, 2009
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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April 10, 2009
Ken A. Paller, Joel L.Voss, Carmen E. Westerberg
Article in Perspectives on Psychological Science
Abstract
There is a marked lack of consensus concerning the best way to learn how conscious experiences arise. In this article, we advocate for scientific approaches that attempt to bring together four types of phenomena and their corresponding theoretical accounts: behavioral acts, cognitive events, neural events, and subjective experience. We propose that the key challenge is to comprehensively specify the relationships among these four facets of the problem of understanding consciousness without excluding any facet. Although other perspectives on consciousness can also be informative, combining these four perspectives could lead to significant progress in explaining a conscious experience such as remembering. We summarize some relevant findings from cognitive neuroscience investigations of the conscious experience of memory retrieval and of memory behaviors that transpire in the absence of the awareness of remembering. These examples illustrate suitable scientific strategies for making progress in understanding consciousness by developing and testing theories that connect the behavioral expression of recall and recognition, the requisite cognitive transactions, the neural events that make remembering possible, and the awareness of remembering.
Click here for the full paper.
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March 5, 2008
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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October 31, 2007
 Combining the latest research foci and treatment modalities, the Second Annual International Brain Conference at UCF offers physicians, scientists, pharmaceuticals, medical device manufacturers, nurses, allied medical professionals and students the opportunity to learn about the absolute latest in brain research and practice. Participants will also be able to earn Continuing Medical & Psychological credits.
Held at UCF’s beautiful Rosen College of Hospitality Management in the heart of Orlando’s tourist district, the Second International
Brain Conference at UCF features keynote speaker Dr. Konrad Beyreuther, recipient of the Potamkin Prize and the Henry M. Wisniewski Award for Lifetime Achievement in Alzheimer’s Disease Research. Beyreuther’s work laid the foundation for understanding the molecular processes that lead to Alzheimer’s Disease.
On opening night Special Guest Mark McEwen, weatherman and entertainment reporter on the CBS Early Show for 16 years, will tell his inspiring personal story: “Stroke: My Recovery Story and the Regenerative Powers of Hope and Rehabilitation.”
Take advantage of early registration rates that end December 1. Special rates are also available for ADI members. Register now at
www.brainconference.org or call 407-882-1576 for more information.
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October 18, 2007
 The role of the prefrontal cortex in decision making is today placed on a solid scientific foundation. But for the ventromedial prefrontal cortex (VMF), it is still uncertain whether it plays a role in decision making under uncertainty or whether it is a “pure” decision structure per se. In a paper by Fellows and Farah, it is argued that “VMF plays a necessary role in certain as well as uncertain decision making in humans”
September 15, 2007
From MindHacks
 An article in this week’s Science News discusses whether the brain stem may play a more central role in consciousness than it’s usually given credit for.
It focuses on children with hydranencephaly, a where the cortex fails to develop in children and instead, the space is filled with cerebral spinal fluid.
Typically, affected children survive only a few months after birth, but those that do survive seem to remarkably more conscious than you would guess based on theories that suggest the cortex is where all the action happens to support consciousness.
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August 2, 2007
 Does the ventromedial prefrontal cortex play a role in personal moral judgment? Medscape.com has a nice report on 7 patients with lesions in the ventromedial prefrontal cortex that find that “the ventromedial prefrontal cortex is necessary to oppose personal moral violations, possibly by mediating anticipatory, self-focused, emotional reactions that may exert strong influence on moral choice and behavior.”
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 Neuroscientists and engineers are developing ways to help patients overcome paralysis and stroke. But what about mental function itself? Can medical intervention restore consciousness?
Nature runs a story on thalamic stimulation after severe stroke. Could this method be applied to help patients in coma or vegetative state regain their mental life?
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June 12, 2007
 As if it was not bad enough to suffer from a brain injury following such as stroke, many sufferers of injury to visual areas also report experiences of hallucinations.
Interestingly, these reports should not necessarily be understood as the result of neuropathology or as unimportant symptoms, but rather as the result of functional reorganization - aka plasticity - of the neural underpinnings of visual perception.
Visual hallucinations during spontaneous and training-induced visual field recovery
D.A. Poggel et al.
Neuropsychologia
Volume 45, Issue 11, 2007, Pages 2598-2607
Visual hallucinations after post-geniculate visual system lesions were shown to be associated with spontaneous recovery of visual functions. We investigated the occurrence of hallucinations during spontaneous recovery and additionally tested whether hallucinations were re-instated in a phase of vision restoration therapy (VRT). Nineteen patients with post-geniculate lesions and homonymous visual loss participated in a prospective study, and 121 patients with various lesions were included in a retrospective study using a questionnaire including verbal descriptions as well as drawings of hallucinations experienced by the patients. In both samples, visual-field size was determined before and after 6 months of VRT. Many patients in both groups experienced post-lesion hallucinations (mostly colors, objects, motion) which subsided after spontaneous recovery of visual functions (increase of visual field size, recovery of more complex visual function) was ended. Hallucinations re-emerged during training. However, the majority of patients reported simple, unformed visual hallucinations (uncolored phosphenes, spots, flashes), especially when visual field recovery was most intense. Hallucinations were mainly found in patients with large shifts of the visual field border. They occurred in blind areas, particularly in areas of residual vision where recovery was predominantly observed. Hallucinations may reflect functional recovery in partially lesioned brain areas. While the colored/formed hallucinations during spontaneous recovery may represent non-specific activation of higher visual areas, the simple, unformed training-related hallucinations may indicate recovery in the primary visual cortex during treatment. Hallucinations should not generally be discarded as pathological or unimportant symptoms, but they may be functional indicators of visual system plasticity.
ScienceDirect
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April 6, 2007
 In a most interesting paper by Ceri Trevethan, Arash Sahraie and Larry Weiskrantz, it is suggested that blindsight patients are actually superior on certain visual stimulus detection tasks. In this paper, published in Cognition, the authors also provide experimental evidence that this is indeed the case.
The study highlights the neural dynamics that take place in the case of brain damage. While the areas that are damaged have been responsible for a given task (i.e. vision) it is likely that such injury leads to unmasking of previously suppressed functions in adjacent or other connected areas. As such, brain damage might indeed not only lead to reduced functions, but unmasking — and enhancement — of other functions. As in this study,
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February 16, 2007
 Adding to the recent surge of studies on future thinking, Hassabis and colleagues recently reported the results they obtained from testing amnesic patients with bilateral hippocampal damage. Compared to healthy control participants, who were matched for age, education and IQ, the amnesic group tested in this study demonstrated impairment on a task that required the imagination of new experiences. The authors noted that the patients’ imagined experiences were strikingly deficient in spatial coherence, leading to fragmented constructions of the future that were lacking in richness. In light of the results of this study, the authors suggested that the hippocampus may provide the spatial context, a critical contribution, for the creation of new experiences. Clickthrough for abstract.
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January 21, 2007
 TIME and CNN present an interesting video on Sarah Scantlin, a patient who suffers from severe brain damage. After being stuck in what was thought to be a vegetative state for 20 years, Sarah has recently regained her ability to speak. Scientists now think that Sarah was in a minimally conscious state, described as having a low level of awareness but conscious nonetheless, for the past two decades. It is noted that while some regions of Sarah’s brain are damaged, other regions are struggling to make new connections. (Image from the video.)
When asked whether she felt asleep or trapped for the last 20 years, Sarah reported having felt trapped. Amongst other challenges, Sarah seems to lack a concept of time, leaving her to believe that she is still 18 (the age at which she incurred her brain injury) when in fact she is now at the age of 40 years.
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January 14, 2007
 When the neuro-talk falls on emotions, most start thinking about the amygdala. Little do we associate with that hind-brain structure we call the cerebellum. Although it is known that this structure is involved in more than movements, little is really known about it’s cognitive functions, let alone in emotions.
In an article by Turner et al. in Neuropsychologia, the function of the cerebellum in emotions is explored by comparing six patients with cerebellar injury and healthy subjects. By applying both behavioural and PET methods, the results demonstrate that cerebellum plays a role in both positive and negative emotions.
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December 21, 2006
 Steven Laureys and colleagues ask whether functional imaging methods such as fMRI and PET can be used to detect consciousness in individual patients. Recent studies have showed activation patterns in a vegetative patient that are comparable to helahty subjects. One pertinent question is therefore whether we can move from group studies towards individual scans. Here, Laureys et al. still have reservations, saying that “[published] data are insufficient to make recommendations for or against any of the neurorehabilitative treatments in vegetative state and minimally conscious state patients.”
How should functional imaging of patients with disorders of consciousness contribute to their clinical rehabilitation needs? Laureys S, Giacino JT, Schiff ND, Schabus M, Owen AM. 2006 Dec ; 19 (6): 520-527
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March 27, 2006
What happens following injury to the thalamus? In this case study Edelstyn, Hunter & Ellis demonstrate a patient with dorsolateral thalamic damage with specific deficits in conscious processing.
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