What's New in Neurofeedback

• Bad Memories Block Out New Memories

• Brain secrets of addiction revealed

• Head injuries' double whammy explained

• Brain implant may restore memory

  All links at: http://news.yahoo.com/fc?tmpl=fc&cid=34&in=science&cat=brain_research

  Neurofeedback and epilepsy.

It may come as a surprise that this question can be answered, and rather easily, I might add. Surely brain structures are like professional sport teams: we all have favorites. Often the ones we learned about first in life (e.g., the Red Sox) or the ones constantly on the local news (e.g., the Yankees). When we think of importance and brain areas in humankind, most of us would presume recent structures, those that evolved to separate us from our simian forebearers such as the frontal lobes or our large neocortex in general. Ahh, these must be the most important areas of the brain.

Well, let's correct a misconception. The outstanding cognitive capabilities of humans are commonly attributed to a disproportionate enlargement of the frontal lobe during evolution. But this didn't happen. Our large brains are mostly cortex (by weight) and the cortex is 35% frontal lobe, 20% parietal, 18% temporal, 16% occipital ( the remainder limbic and insula). Our frontal lobes are approximately 400K cubic millimeters in volume. Pretty good. Compare this to a "mere" 100K cubic mm in chimps, but relatively speaking, our frontal lobes are like our relatives' in size: 38% hemispheric volume in humans, 35% in both chimpanzee species, 37% gorillas, 38% orangutan, and even 30% in (macaque) monkeys. Well, let's assume our frontal lobes are more richly interconnected than our furry brethren's forebrains and that explains our genius (more misconception, perhaps).

So can neuroscientists and other people in the know agree upon the most important brain structure? We don't need people to tell us. We can ask the brain itself. Which part of you do you most cherish, most service? Which part of yourself do you get online first, and keep online most? And given that you need it most, and rely on it most, it probably is as overextended as most of our bank accounts, so which structure is most fragile, most easily run into the ground?

The most important brain structure in humans is the inferior colliculus. (The what?) Overlooked, ignored, it is the geek who controls auditory information flow at its earliest point. It's even called "inferior!" It's not cortical nor even limbic. It's midbrain (and some even mistakenly relegate it to brainstem). Most metabolically active. First myelinated. Most vascularized. Hands down, the most important structure in the brain, human or nonhuman mammalian.

Landau et al. (1955) was the first to investigate the question that opened this article. They detected the highest blood flow in the (cat) brain at the inferior colliculus (IC) -- and they couldn't believe it. The high levels must be an artifact, they thought; their equipment was rather noisy, and thus this early auditory processing area was activated by the measuring device. But when they repeated their experiments with deafened cats, they found the same result. I tell you, the structure gets no respect. Hearing continuously keeps us in touch with the environment, it's on even when we're off (asleep), so should it surprise us to be so serviced, so active (Fisch, 1970). The IC has the greatest capillary supply (Craigie, 1938) and both monkey and rat brains feed the IC more glucose than any other structure. In fact the 2nd most active structure in both animals is the auditory cortex, so even the rat, notoriously called a smell-brain, is underneath it all a hearing brain like us. At 25 gestational weeks (Yakovlev and Lecours, 1967), the IC is already ready for prime time: it is myelinated and thus fully functional. The IC is only one of two brain structures fully functional at birth. We think of cortex when we think of language but the language areas of the temporal and frontal lobes are not myelinated until a child is three or four years of age (and other areas of the frontal lobe will not be fully myelinated until 30 years of age!). Injury of the inferior colliculus causes "word deafness," the inability to comprehend spoken language.

The inferior colliculus is also the first to "go south" when the brain is deprived of oxygen. It is selectively damaged by a few minutes of total asphyxia at birth in newborn monkeys. Some forms of autism may reflect IC impairment; that is, the result of perinatal anoxia. (If so, teach sign language to suspected autistic infants/toddlers to create a linguistic mind without sound processing). Perhaps Asperger syndrome, attention deficit disorder, and learning disabilities reflect mild perinatal hypoxia (clamping the cord before the first breath, with subsequent IC damage) that simply goes unrecognized until latter (school) evaluations.

One essential function served by the IC is that of sentinel: representing the environment preattentively. It scans the room, seeking changes (e.g., emerging threats) in the periphery. Hearing-impaired individuals score like hyperactive ADHDers on tests of visual vigilance, like the TOVA, because they are forced to use vision for both sentinel and conscious spotlight. In fact the lesson that might be taken from the importance of the IC is that preattentive processing may be the source of problems. Forget the cortex, psychiatric illness is probably subcortical -- at least that is where it might start. Disconnecting the IC from the structures above it produces dramatic losses of attention, affect, and motivation, reminiscent of autistic children (Sprague et al, 1961). A focus on preattentive or preconscious states for psychiatry would vindicate Freud AND neurotherapy, as I characterize operant conditioning of the EEG is a volitional but nonconscious process. The work gets done at the preconscious level, the preattentive parallel state. Also, auditory information may be more important in neurofeedback than visual information? Perhaps. There are other factors involved in operant conditioning (motivation, etc), but we may excite the brain with sound before we excite it with images.

From the small to the large:

Each hemisphere of the brain contains within it a trillion connections, between it and the other hemisphere a mere billion or so (200 million fibers, 4-5 collateral connections per fiber). This 3 orders of magnitude difference between intrahemispheric and interhemispheric connectivity suggests that cognition is mostly intrahemispheric. Language provides us with a good example: Phoneme components can be differentiated from each other in as little as 8 ms. It takes 25 ms to send a signal from one temporal lobe to the other, so how do we process language. Quickly and locally, of course.

The dominant (typically left) hemisphere is anatomically and cognitively organized more focally; the non-dominant (right) hemisphere more diffusely. This means that electrode placement is critical over the dominant hemisphere. A centimeter askew and you're training a different set of processors. It's kind of like the eastern and western states. Fifty or a hundred miles off will keep you in the same state if you're in the west (analogous to the nondominant hemisphere), but it will put you a state or two off-target if you were aiming for Connecticut or Massachusetts.

The connections between hemispheres is either 98 or 99% homotopic, meaning that fibers running from, say, the left temporal lobe (e.g., below T3) connect almost entirely to the right temporal lobe (T4), Fp1 to Fp2, O1 to O2, generally. This means that any bipolar placements between non-homologous pairings is either relying on 1% of the callosal fibers, or, far more likely, working through subcortical connections (or not at all!) By subcortical, we're talking subthalamic, because there is no connection between the two thalami (the intermedia massa is so small, and so unknown in function, to be negligible), so the only way to send a signal from one region of a hemisphere to a different region in the other hemisphere is to send it via the midbrain and brainstem. Right through the inferior colliculus' neighborhood.

Of course.

-DK

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