“The point of the cognitive map is flexibility. It gives animals the ability to plan novel paths within their environment,” said Redish [A. David Redish, University of Minnesota Medical School, USA]. “This replay process may be an animal’s way of learning how the world is interconnected, so it can plan new routes or paths.”

[Source: EurekAlert]

Dr. Redish is talking about studying brain activity in the hippocampus of rats. The hippocampus, a bean-shaped section of the brain in the medial temporal lobe, has long been associated with the memory process, and as a location for ‘replay’ activity. It was thought that’s when the brain replays experienced events in order to consolidate long-term memories. What Dr. Redish along with colleagues at Carnegie Mellon University (Pennsylvania, USA) discovered is that the replay function of the hippocampus is a much more complicated cognitive process. It is an important part of producing the ‘cognitive map’ and is a way the brain organizes experiences so that it can ‘plan novel paths’ – it is part of the decision making process.

The research team used lab rats outfitted with sensors that could pinpoint the firing of specific neurons (brain cells). For example, neurons called place cells fire according to the animal’s current location and contribute to the animal’s internal cognitive map of their environment. This mapping process proved to be the way into understanding the replay process. During replay, the pattern of place neuron activity indicated that the animal was processing information about locations other than where it actually was.

The researchers went on to give the rats specific tasks, say A and B. They found that afterwards the hippocampus would replay the lesser performed of the two tasks. That the rats were most likely to replay tasks performed less often was an indicator that the brain was attempting to get a fix on a broader cognitive map than just things done often or recently. Confirmation of this mental activity was even more pointed; the rats would ‘replay’ connections never physically travelled. For example, if the animal had been in a maze traveling from point A to point B, and from B to C – but never from A to C – it would make the connection A to C in its replay.

These observations led the research team to conclude that hippocampus replay doesn’t just review experiences on the way into long-term memory. It provides an important part of evaluating experiences – often older and less strong experiences – so that a more complete cognitive map can be assembled.

As usually seems to be the case, more research on brain processes reveals them to be more complex than originally thought. The researchers in this study admit that (especially in humans) brain cognition and decision making are poorly understood. There’s something about studying the brain processes by gross location with an EEG or fMRI that is reminiscent of the blind men studying an elephant: It’s not what they can’t see that counts; it’s that their tidbits of insight don’t add up to a whole elephant.

The researchers came to this conclusion after conducting tests to measure how much people observed of small events occurring in short periods of time. In a first round of research in 2009, they used a flashing but dim light at various intervals. They noted – as people sometimes do in real life – that some of the flashing lights were noticed, at other times not. In traditional neurology this missing of details, even repeated flashing of colored lights, was ascribed to ‘lack of attention’, ‘random thought interruption’, or just ‘neural noise’. The researchers thought otherwise. There was a pattern to what was seen when, a rhythm.

After establishing that there was a regularity to perception, that lights were noticed or not noticed in more or less regular sequence, they wondered if this rhythm could be in some way influenced – the word used by psychologists is entrained. Did the mind automatically change rhythms to match a situation so that important details would not be missed? Could this be stimulated artificially?

The answer was, yes. The second experiments involved a faint, rhythmic light followed immediately by a second light that masks the first light so that only the second light is the one seen. The first light is ‘lost’ as a matter of visual information. The technique is called backward masking. The subjects were then told about the first light and told to concentrate on the rhythm of flashes so that they could see the first light – their perception then became entrained. This was the first time in a controlled experiment where the rhythm of visual cognition was trained to make visual perception intentionally focused. This implied that the rhythms and frames used by the brain as part of the ‘filtering’ of reality – the ways used by the brain to avoid sensory overload – and may be common to other brain functions.

“There is this idea that we look out into the world and see this ongoing flow of consciousness that has been compared to a stream,” says Kyle Mathewson, lead author of the paper that appears in the journal Cognition. “This evidence and other evidence are starting to show it might not be like that, it might be more discrete.”

“We’re just flashing something on the screen but if you think about it many of the things around us are rhythmic: our speech has certain rhythmicity to it, cars moving down the street, movement has rhythmicity to it,” Mathewson said. “So this might be a more common mechanism throughout the brain by which the brain starts to process the environment because it picks up on the rhythmicities that are everywhere.

And that means a research line that has many possibilities.

[Source: Futurity]

Many possibilities indeed, as it may turn out many processes in the brain are rhythmic, timed, waveform, cyclical – and partial (discrete) – not continuous, as in stream of consciousness. More like the rhythm of consciousness.

The study extended research done in 2006, which used fMRI on a patient with no apparent sign of consciousness in seven months, but who could respond correctly to direct commands, as seen in brain activity scanned by MRI. Fifty-four patients diagnosed to be in a permanent vegetative state were examined. They were each asked to do two things: First, imagine that they were playing tennis; second, that they were walking near their home. The research team had already determined where in the brain these thought patterns would be expressed in normally functioning brains. Of the fifty-four, five were able to hear the requests, understand what was asked, and do the visualizations. (All five were victims of physical brain damage, not oxygen deprivation, which indicates this type of injury has a better chance of recovery.) One of the five was able to go further and use the brain activity from the two questions as equivalent to ‘yes’ and ‘no’ in response to other questions. In short, he was conscious enough to answer five out of six questions. There was no response to the sixth question.

While from these tests of fMRI activity it was not possible to accurately assess the total damage to the brains of each patient, it was clear some few that are diagnosed as in a permanent vegetative state may have one degree or another of active consciousness.

Does this change our view of consciousness? Some think yes:

“In my view, this paper is a breakthrough in cognitive science and in neurology, and it will probably be the basis for a more open discussion of what it means to be awake, alert, and human,” says Allan Ropper, a neurologist at Brigham and Women’s Hospital in Boston, who wrote a commentary accompanying the paper in the NEJM.

“This is a first case, but at least it shows that technology is challenging the boundaries based on clinical bedside examination,” says Steven Laureys, head of the coma science group at the University of Liege, in Belgium, and one of the authors of the paper. “I’m convinced that we need to adapt our standard of care and our ethical and legal framework to take account of this new technology.” The researchers did not test the other four patients who could do mental imagery, mainly because of the difficulty of carrying out the tests.

[Source: Technology Review]

Others might say that consciousness has long been a difficult state to define. We’ve been aware, for a century or two, of consciousness existing in those with no means for communication. Modern technology is helping to get a better handle on that state, but the qualities of consciousness are still open for debate. This leaves the ethical questions.

For example, is the absence of a ‘positive fMRI scan’ a true indication of a state of no consciousness? Supposing that we can communicate with some patients via fMRI, can we presume they are able (and fit) to make judgments about their condition and treatment? fMRI procedures are cumbersome, difficult for this type of patient, and very expensive – in short, a relatively typical procedure for adverse cost-benefit analysis. (In countries where insurance drives many medical decisions, this too is a pressing ethical decision.)

The intriguing and perhaps astonishing use of fMRI to communicate with a presumed unconscious patient typifies the type of ‘wonderful’ effect technology can have on our sympathy for an individual and the individual’s story. At the same time, it leaves big gaps in the reality where most patients of this type do not recover, and even if there is some response, it is no guarantee of anything resembling a ‘meaningful life’. Put another way: In a public narrative (in extremis, the Terri Schiavo case in the United States) the drama evokes sympathy and even outrage. Outside of a public narrative, in the day-to-day routine of medicine and family life, most decisions fall toward ‘letting them go.’ We’ll see how much MRI or similar technology will change that outcome.