When acetylcholine is released at a neuromuscular junction, it crosses
the tiny space (synapse) that separates the nerve from the muscle. It
then binds to acetylcholine receptor molecules on the muscle fiber's
surface. This initiates a chain of events that lead to muscle contraction.
Scientists have shown that muscle fiber contains a scaffold made of
special proteins that hold these acetylcholine receptors in place.
Research led by Jeff W. Lichtman, M.D., Ph.D., at Washington University
School of Medicine in St. Louis, indicates that a loss of nerve signals
-- due to inactivity -- actually disassembles this scaffold and causes a
loss of acetylcholine receptors. When the muscle becomes active again,
however, the scaffold tightens its grip and catches any receptors that
come by.
"So muscle activity is a cue to keep a synapse stable, and synaptic
inactivity is a cue to disassemble a synapse," says Lichtman, a
professor of neurobiology. "So if you lose activity, you lose receptors.
But if you regain activity, you get those receptors back."^2
<http://www.fi.edu/learn/brain/references.html#exercise2>
^
http://www.fi.edu/learn/brain/exercise.html
http://jn.physiology.org/content/83/2/1079.full
Abstract
The purpose of this study was to determine, by using functional magnetic
resonance imaging, the areas of the brain activated during a
memory-timed finger movement task and compare these with those activated
during a visually cued movement task. Because it is likely that subjects
engage in subvocalization associated with chronometric counting to
achieve accurate timing during memory-timed movements, the authors
sought to determine the areas of the brain activated during a silent
articulation task in which the subjects were instructed to reproduce the
same timing as for the memory-timed movement task without any lip
movements or vocalization. The memory-timed finger movement task induced
activation of the anterior lobe of the cerebellum (lobules IV and V)
bilaterally, the contralateral primary motor area, the supplementary
motor area (SMA), the premotor area (PMA), the prefrontal cortex, and
the posterior parietal cortex bilaterally, compared with the resting
condition. The same areas in the SMA and left prefrontal cortex were
activated during the silent articulation task compared with the resting
condition. The anterior lobe of the cerebellum on both sides was also
activated during the silent articulation task compared with the resting
condition, but these activations did not reach statistical significance
(/P/ < 0.05 corrected). In addition, the anterior cerebellum on both
sides showed significant activation during the memory-timed movement
task when compared with the visually cued finger movement task. The
visually cued finger movement task specifically activated the
ipsilateral PMA and the intraparietal cortex bilaterally. The results
indicate that the anterior lobe of the cerebellum of both sides, the
SMA, and the left prefrontal cortex were probably involved in the
generation of accurate timing, functioning as a clock within the CNS,
and that the dorsal visual pathway may be involved in the generation of
visually cued movements.
INTRODUCTION
The generation of rhythmic self-paced movements has recently been the
subject of several neuroimaging studies. To perform rhythmic self-paced
movements, the capacity to time the movements precisely is important.
However, the neural substrates for the explicit timing of movements
remain unclear. Some human neuroimaging studies have investigated this
subject by comparing brain activity during memory-timed movements with
that during externally triggered movements (Larsson et al. 1996
<http://jn.physiology.org/content/83/2/1079.full#ref-28>; Remy et al.
1994 <http://jn.physiology.org/content/83/2/1079.full#ref-49>). However,
these studies focused on the activation of cortical primary and
nonprimary motor areas, but not of other brain areas involved in the
control of voluntary movement. Recently,Rao et al. (1997)
<http://jn.physiology.org/content/83/2/1079.full#ref-48>, by using whole
brain functional magnetic resonance imaging (fMRI), compared the brain
areas activated during memory-timed finger tapping and during auditorily
cued movements. They reported that the supplementary motor area (SMA),
the putamen, the thalamus, and the inferior frontal cortex were
specifically involved in the memory-timed movements. Nevertheless, they
used a series of tones separated by a constant interval as a control
condition for the auditorily cued movements. It is likely that subjects
predict the timing of the movements when sensory cues are presented at
consistent intervals. Thus, the brain areas involved in the timing of
movements are also probably activated in this condition.
RESULTS
The mean ± SD frequency of the memory-timed finger movements during the
fMRI measurements was 0.59 ± 0.11 Hz, which is lower than that noted
during visually cued movements (0.67 Hz). The mean ± SD reaction time
for the visually cued finger movements during the fMRI measurements was
358.5 ± 68.4 ms.
Table 1 <http://jn.physiology.org/content/83/2/1079.full#T1> summarizes
the data on Talairach coordinates (Talairach and Tournoux 1988
<http://jn.physiology.org/content/83/2/1079.full#ref-57>) and the /z/
score of peak activation in each task versus rest. Memory-timed
movements significantly activated the anterior lobe of the cerebellum on
both sides (lobules IV and V), the contralateral primary motor area
(M1), the dorsal premotor areas (PMA) bilaterally, the SMA, the inferior
frontal cortex bilaterally, the left intraparietal cortex, and the right
inferior parietal lobe compared with the control resting condition (Fig.
1 <http://jn.physiology.org/content/83/2/1079.full#F1> /A/). The same
area in the ipsilateral (right) anterior cerebellum, the contralateral
M1, the bilateral dorsal PMA, the left intraparietal cortex, and the
right inferior parietal cortex were also significantly activated during
the visually cued movement task. The SMA was also significantly
activated, but the location of the peak activation was more posterior to
that during the memory-timed movements. In addition, the visually cued
movements activated the ipsilateral ventral PMA, the right middle
frontal cortex, the left inferior parietal cortex, the right superior
temporal cortex, the left insula, and the right thalamus (Fig.1
<http://jn.physiology.org/content/83/2/1079.full#F1> /B/). The
contralateral (left) anterior cerebellum showed slight increases in
activity (/P/ < 0.01: uncorrected; Fig. 2
<http://jn.physiology.org/content/83/2/1079.full#F2>). The silent
articulation task activated the SMA and the left inferior frontal cortex
compared with the control resting condition (Fig. 1
<http://jn.physiology.org/content/83/2/1079.full#F1> /C/). These two
areas were the same as those activated during the memory-timed movement
task. The anterior lobe of the cerebellum was activated bilaterally
during the silent articulation task compared with the resting condition.
However, these activations did not reach statistical significance (/P/ <
0.05: corrected), although an uncorrected significance level of /P/ <
0.001 was observed
DISCUSSION
Our results demonstrate that memory-timed finger movements activated the
anterior lobe of the cerebellum bilaterally, the contralateral M1, the
PMA bilaterally, the SMA, and the parietal cortex and the prefrontal
cortex bilaterally. Among these structures, the anterior lobe of the
cerebellum of both sides, the SMA and the left prefrontal cortex were
probably involved in the generation of accurate timing, functioning as a
clock of the CNS.
Cerebellum
In the present study, the anterior lobe of the cerebellum of the
ipsilateral hemisphere was activated during both memory-timed and
visually cued movement tasks. The results support the traditional role
of the cerebellum in the control of movement and the findings of
anatomic and neurophysiological studies as well as recent human
neuroimaging studies that movement is represented somatotopically on the
ipsilateral side (Allen et al. 1997
<http://jn.physiology.org/content/83/2/1079.full#ref-1>;Colebatch et al.
1991 <http://jn.physiology.org/content/83/2/1079.full#ref-2>; Deiber et
al. 1996 <http://jn.physiology.org/content/83/2/1079.full#ref-6>; Fox et
al. 1985 <http://jn.physiology.org/content/83/2/1079.full#ref-9>;
Grafton et al. 1993
<http://jn.physiology.org/content/83/2/1079.full#ref-13>; Stephan et al.
1995 <http://jn.physiology.org/content/83/2/1079.full#ref-56>; Thach
1996 <http://jn.physiology.org/content/83/2/1079.full#ref-58>; Van Mier
et al. 1998 <http://jn.physiology.org/content/83/2/1079.full#ref-61>).
In addition, we found that the anterior lobes of the cerebellum of both
sides were activated to a greater extent during memory-timed movements
than that during visually cued movements, the silent articulation task,
and the control resting condition (Figs. 2
<http://jn.physiology.org/content/83/2/1079.full#F2> and 3
<http://jn.physiology.org/content/83/2/1079.full#F3>). It is of interest
to note that the self-paced finger movements in association with rapidly
alternating movements of flexion and extension of the fingers activated
only the ipsilateral anterior cerebellum (Fox et al. 1985
<http://jn.physiology.org/content/83/2/1079.full#ref-9>), although, in
this study, self-paced finger movements timed by memory activated the
anterior cerebellum bilaterally. These bilateral activations cannot be
related to the execution of movements, because the number of movements
during the measurement was higher in the visually cued movement task
than in the memory-timed movement task in this study. The silent
articulation task in this study, in which the subjects engaged in
subvocalization associated with chronometric counting to achieve
accurate timing, activated the anterior cerebellum bilaterally (/P/ <
0.001), although this activation did not reach statistical significance
(/P/ < 0.05 corrected). The results are consistent with those reported
by previous neuroimaging studies using SPECT showing the involvement of
the cerebellum in silent mental counting, which requires chronometric
counting (Decety et al. 1990
<http://jn.physiology.org/content/83/2/1079.full#ref-4>; Ryding et al.
1993 <http://jn.physiology.org/content/83/2/1079.full#ref-53>). However,
they used region-of-interest--based analysis, and further, analyzed only
the inferolateral parts of the cerebellar hemisphere. Therefore, to
summarize, our results suggest that the ipsilateral anterior cerebellum
is involved in the control of finger movements, and the anterior
cerebellum of both sides is involved in chronometric counting to achieve
accurate timing, and that these areas are more strongly activated to
control the timing of the actual movements.
It has been argued that one of the important functional roles of the
cerebellum is the control of motor timing (Thach 1996
<http://jn.physiology.org/content/83/2/1079.full#ref-58>). A finding
reported by Ivry and colleagues (1998)
<http://jn.physiology.org/content/83/2/1079.full#ref-17>, based on a
series of very robust experiments in patients and normal control
subjects, is that the lateral cerebellum participates in nonmotor
temporal processing (Ivry and Keele 1989
<http://jn.physiology.org/content/83/2/1079.full#ref-16>; Ivry et al.
1988 <http://jn.physiology.org/content/83/2/1079.full#ref-17>; Keele et
al. 1985 <http://jn.physiology.org/content/83/2/1079.full#ref-25>). In
recent neuroimaging studies, the activation of the anterior lobe of the
cerebellum of both sides was noted, when the subjects estimated time
differences by comparing a test time with a standard interval (Jueptner
et al. 1995 <http://jn.physiology.org/content/83/2/1079.full#ref-18>)
and when subjects reproduced rhythms of increasing complexity (Penhune
et al. 1998 <http://jn.physiology.org/content/83/2/1079.full#ref-39>),
indicating the involvement of the cerebellum in motor timing and
perceptual timing, respectively. Van Mier et al. (1998)
<http://jn.physiology.org/content/83/2/1079.full#ref-61>also suggested
that the anterior cerebellum might relate to movement timing at a
muscle-specific level. In this study, during the memory-timed movement
task, the subjects were instructed to reproduce accurately the timing of
the movements from their working memory.
Therefore our results, combined with the results of previous studies,
support the hypothesis that the cerebellum is a clock within the CNS,
either because of its own intrinsic circuitry (Ivry et al. 1988
<http://jn.physiology.org/content/83/2/1079.full#ref-17>) or in
combination with its extrinsic motor and premotor connections (Thach
1996 <http://jn.physiology.org/content/83/2/1079.full#ref-58>) that may
time many activities independently and in addition to actual movements.
Prefrontal cortex
An area in the left middle frontal gyrus was specifically activated
during the memory-timed movement task (Fig. 4
<http://jn.physiology.org/content/83/2/1079.full#F4> /A/). Activation of
this area, located in the dorsolateral prefrontal cortex, has also been
reported in other positron emission tomography (PET) studies of
memory-timed finger movements (Kawashima et al. 1996a
<http://jn.physiology.org/content/83/2/1079.full#ref-19>; Larsen et al.
1996 <http://jn.physiology.org/content/83/2/1079.full#ref-28>). Frith et
al. (1991) <http://jn.physiology.org/content/83/2/1079.full#ref-12>
reported the activation of an area in the vicinity of the aforementioned
area in relation to the willed component of movement. Because
memory-timed movement is a voluntary act requiring repeated decision to
move (Larsen et al. 1996
<http://jn.physiology.org/content/83/2/1079.full#ref-28>), our results
support the argument of Frith et al. (1991)
<http://jn.physiology.org/content/83/2/1079.full#ref-12> in favor of the
functional role of the dorsolateral prefrontal cortex in the generation
of self-determined finger movements. Although the generation of
memory-timed movements requires the maintenance of information regarding
movement timing in working memory, another possible explanation for the
left dorsolateral prefrontal activation is the working memory load
imposed during the performance of self-paced movement (Petrides et al.
1993 <http://jn.physiology.org/content/83/2/1079.full#ref-43>).
The left inferior frontal cortex was activated during the silent
articulation task, as well as during the memory-timed movement task in
this study (Fig. 4 <http://jn.physiology.org/content/83/2/1079.full#F4>
/B/). Our results indicate that this area may be involved in
subvocalization associated with chronometric counting. Recent
neuroimaging studies have indicated that the left inferior frontal
cortex is involved in language processing, in terms of perception,
production, and memory, in normal subjects (Demonet et al. 1993
<http://jn.physiology.org/content/83/2/1079.full#ref-7>; Kelley et al.
1998 <http://jn.physiology.org/content/83/2/1079.full#ref-26>; Petersen
et al. 1989 <http://jn.physiology.org/content/83/2/1079.full#ref-40>,
1990 <http://jn.physiology.org/content/83/2/1079.full#ref-41>; Posner
and Carr 1992
<http://jn.physiology.org/content/83/2/1079.full#ref-45>;Wagner et al.
1998 <http://jn.physiology.org/content/83/2/1079.full#ref-62>). Our
results are in agreement with results of these studies.
*Hi Ray, down here!!!*
I agree with you. I still subscribe to the theory that memory isn't even
located in the brain, that (healthy) brain merely accesses it from the
universe, and when you go for a ride in the car, it cruises above the
roof along with you.
However, I was talking about mapping physiologically the areas
performing scales would affect. But it's been done. This study, a PDF
called _/*The brain that plays music and is changed by it, */_found at
<http://www.fi.edu/learn/brain/exercise.html>http://www.google.ca/search?q=human+memory%2C+fingers%2C+connections&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a
<http://www.google.ca/search?q=human+memory%2C+fingers%2C+connections&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a>
I'm certain you'll find this interesting. I need time to read it
through, myself. Sorry I have yet to learn how to download PDFs to an email.
Natalia
On 5/18/2011 5:57 AM, Ray Harrell wrote:
In my world, there is no unrelated memory. It's about discovering
relationship in the web of memory. What do you mean by the term?
REH
-----Original Message-----
From:[email protected]
[mailto:[email protected]] On Behalf Of D and N
Sent: Wednesday, May 18, 2011 2:08 AM
To: RE-DESIGNING WORK, INCOME DISTRIBUTION, EDUCATION
Subject: Re: [Futurework] always growing brain cells
Exactly. Have you mapped the path to unrelated memory? You should, cause
it seems to work well for you.
Natalia
On 5/17/2011 10:31 PM, Ray Harrell wrote:
Yep! That's right. I practice scales hours every day as I teach
singers.
REH
-----Original Message-----
From:[email protected]
[mailto:[email protected]] On Behalf Of D and N
Sent: Wednesday, May 18, 2011 1:17 AM
To: RE-DESIGNING WORK, INCOME DISTRIBUTION, EDUCATION
Subject: [Futurework] always growing brain cells
Just caught the tail end of a CBC show on brain cells this morning. Some
guy from Vancouver's Brain Research Center said they'd recently learned
that new brain cells involved in learning continue to emerge every day
throughout old age, apparently at a rate of about 1000 per day if
focused solely on cognitive skills, and around 3000 per day when
actually doing physical exercise. Though we have about 10 billion brain
cells, each with 10's of 1000s of connections, not all areas are tied up
in learning. And specific areas can grow larger with focused skills such
as practicing piano scales, increasing the area associated with fingers
only.
Unfortunate that the athletically trained often suffer such body aches
in late life, and have to forgo those good habits.
Natalia
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