NOTICE: Posting schedule is irregular. I hope to get back to a regular schedule as the day-job allows.

Wednesday, February 16, 2011

From the Mailbag 1

Whew.  Taking a bit of a breather tonight. 

One of the challenges of academic research is the paperwork, and this week is no exception.  Today alone saw me correcting proofs on a research manuscript, completing a research grant application, handling budgets and writing a progress report.

With all of that office work, you may wonder who actually runs the lab?

Well, many labs jokingly refer to the technicians as lab rats, in Teddy's Rat Lab, we have some literal LabRats (tm).  No, that's not Speaker to Lab Animals over there to the right, no matter what Sarah Hoyt says.

Actually, he's just a cousin.  You can tell because he's a white rat.  The LabRats are "Rattus norvegicus", or Hooded Norway rats just like Ratley over there to the left. Ratley is the boss, and he's in charge of the mailbag.  Right, Ratley?


Oh, yeah, right, they don't understand you.


Anyway, Ratley has also been keeping the lab running in my absence, assisted by Ratso, Ratface, Ratfink, YouDirtyRat and Nestor.  Well, mostly helped.  Ratface keeps getting his tail stuck in the doors. 

The hardest part is keeping up with the mail.  Last week Teddy's Rat Lab got two big questions that have been saved *especially* for this blog:

William asks:  How can a sensory neuron respond to very low signals or even wavelengths that are larger than the cell itself?

Neil asks:  Is there really such a thing as an automatic reaction or "muscle memory"?


Right., Ratley. He reminded me that there are two particular adaptations of visual and auditory neurons that handle just those problems asked by William.   The outer segment of rod and cone cells in the retina have a membrane that folds over itself to pack lots of rhodopsin into a small space.  In this manner, the light-sensitive cells of the retina *amplify* the signal in response to limited space.  For auditory neurons, the neuron itself doesn't respond to the sound wavelength, but the long, tapering Basilar Membrane vibrates in response to sound.  The membrane is long enough to respond to frequencies from 200-20,000 hz.  In fact, different frequencies reach a maximum vibration at different points along the membrane, thus auditory neurons simply have to be organized according to *where* they connect along the length of the basilar membrane.  The neuron itself doesn't have to respond to the wavelength of the sound, but merely to any vibration.  All of the sorting of sound pitch and frequency is donw by the connections between neurons.  We'll talk more about that in later blogs as we work our way through various systems of the brain.


Ratley also mentioned that I should not forget the guy with the big feet.  I guess he means you, Neil, and the answer is yes, there is a special subset of memory commonly called "skill memory."  While it might seem like a type of "reference memory" (that is memory of rules, skills, techniques, etc.) in fact it is not stored or processed through the same parts of the brain as other types of memory. 

To further explain, I present the case of H.M.  Back in the 50's, the patient known only by his initials, H.M., had epilepsy.  It could not be controlled by the drugs of the time, but the brain area in which it originated could be located by electroencephalogram, EEG, the recording of brain electrical activity from the surface of the head.  So the surgeon performed brain surgery and removed the critical area, the inside surface of the temporal lobe on both halves of the brain.  In that region lies the hippocampus - essential to making and storing *new* memory.  Like the man in the movie "Memento," H.M. was no longer able to store new memories, although he could easily recall memories from before his surgery.  For instance, he would read a newspaper, put it down, pick it up 15 minutes later and read it again, never remembering that he had already read it.  Yet, when given a game of skill (Towers of Hanoi - look it up, it's a fascinating game), he continually got better, until he could solve the puzzle perfectly every time.  When asked, he would tell the doctors that he had never seen it before, and would be surprised at his own skill.

Neuroscientists now know that phsyical skills are processed through the cerebellum, caudate and putamen (and other subcortical structures) and do not require the *conscious* memory regions of the brain.  Pretty neat stuff!   So yes, there is "muscle memory" and it is every bit as automatic and mysterious as it seems.

So for now, keep those questions com....


... No, Ratface, watch where you put your... ... tail.

...too late.  I guess Ratley and I need to get back to the lab before Nestor makes an Rat's Nest out of everything.

Until next time...

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