[bookshare-discuss] Re: OT Blindness and brain activity
- From: "Sharon" <mt281820@xxxxxxxxxxx>
- To: <bookshare-discuss@xxxxxxxxxxxxx>
- Date: Fri, 20 Feb 2009 07:53:54 -0500
Wow, great abstract! Yea, I do know the visual cortex is reorganized to
handle sound and tactile. I was in a recent study at Georgetown that looked
at some of this, and am really interested in hearing about what they found.
Sharon
-----Original Message-----
From: Bob [mailto:rwiley@xxxxxxxxxxxxx]
Sent: Thursday, February 19, 2009 9:06 PM
To: bookshare-discuss@xxxxxxxxxxxxx
Subject: [bookshare-discuss] Re: OT Blindness and brain activity
I love computers for research, and Lissi, I love good questions like this
one. I did have the time, so I googled ""brain activity" blindness" and
found the following article abstract. In general, I think it's saying
blindness doesn't make a big difference in either congenitally or
advanticiously blind persons. In other words, don't scare me like that
<lol>!
http://www.pnas.org/content/101/43/15500.full
Abstract
We studied whether default functionality of the human brain, as revealed by
task-independent decreases in activity occurring during goal-directed
behaviors,
is functionally reorganized by blindness. Three groups of otherwise normal
adults were studied: early blind, adventitiously blind, and normally
sighted.
They were imaged by using functional MRI during performance of a word
association task (verb generation to nouns) administered by using auditory
stimuli
in all groups and Braille reading in blind participants. In sighted people,
this task normally produces robust task-independent decreases relative to a
baseline of quiet wakefulness with eyes closed. Our functional MRI results
indicate that task-independent decreases are qualitatively similar across
all
participant groups in medial and dorsal prefrontal, lateral parietal,
anterior precuneus, and posterior cingulate cortices. Similarities in
task-independent
decreases are consistent with the hypothesis that functional reorganization
resulting from the absence of a particular sensory modality does not
qualitatively
affect default functionality as revealed by task-independent decreases. More
generally, these results support the notion that the brain largely operates
intrinsically, with sensory information modulating rather than determining
system operations.
Much previous functional brain imaging work in normally sighted (NS) adult
humans has documented activity decreases during performance of various
goal-directed
behaviors relative to a control state, such as quiet wakefulness with eyes
closed, visual fixation, or a minimally demanding task (1-3). These activity
decreases have a variable relationship to task-specific activity increases.
Some decreases appear to represent activity attenuation in sensory systems
irrelevant to the task; these task-dependent decreases can occur in sensory
cortex both within and separate from the modality engaged by the task (4-7).
Other activity decreases appear to be independent of the performed task.
With remarkable regularity, these task-independent decreases occur in medial
and
lateral parietal cortices, posterior cingulate cortex, dorsal and ventral
medial prefrontal cortex, and the amygdalae (reviewed in ref. 8). We propose
that task-independent decreases represent suppression of default brain
functionality (9) and have cited detailed circulatory and metabolic evidence
showing
that such decreases do not correspond to "activations" in the resting state,
as has been suggested (3). Rather, task-independent decreases occur in areas
that are functionally active but not physiologically "activated." Default
brain activity suggests spontaneous functions that are attenuated only when
we
reallocate resources to temporarily engage in goal-directed behaviors. Hence
our designation of "default" functions (8, 9).
Numerous studies show that blindness leads to cortical reorganization
manifesting as increased visual cortex activity during performance of tasks
involving
tactile and auditory stimuli (reviewed in refs. 10 and 11). Of interest is
whether cortical reorganization in blindness extends to default functions.
Evaluating
the functional architecture of such processes in blind people also addresses
the more general issue of sensory contributions to default functionality.
Our view is that default brain activity is largely concerned with the
maintenance of a probabilistic model of anticipated events (12-14). This
perspective
is consistent with the view that brain function is largely intrinsic, with
sensory information modulating rather than determining operations. In this
context,
then, we assessed whether default functionality, as revealed by
task-independent decreases, is reorganized in blindness.
We compared functional MRI (fMRI) responses in three groups of otherwise
normal adults: early blind (EB), late blind (LB) and NS. All participants
performed
a word association task known to produce robust task-independent decreases
in sighted adults (generating appropriate verbs/action words for common
English
nouns) (1,
3). Our results indicate that default functionality is largely independent
of visual integrity.
Th
anks,
Bob
----- Original Message -----
From: "Estelnalissi" <airadil@xxxxxxxxxxxxx>
To: <bookshare-discuss@xxxxxxxxxxxxx>
Sent: Thursday, February 19, 2009 7:39 PM
Subject: [bookshare-discuss] OT Blindness and brain activity
> Dear Booksharian Friends,
>
> I'm nearly finished proofreading and preparing a book called, The Brain
> Our Nervous System, for check in. It's an orderly, clear and brief
> description of its title and I think is designed to inform and tickle the
> curious bone of kids from about fourth to seventh grade.
>
> Some of the pictures are so organically complex, I can't imagine how to
> describe them meaningfully . For those I just wrote picture in brackets.
> Others I did my best to describe like saying something to the effect that
> the pons and medulla are shown in a shape like a two inch whole carrot
> standing on its tip. The pons is the bottom, thin part that goes down to a
> point and the medulla is the top, thicker half.
>
> The picture which grabbed my attention enough for me to write to you about
> it shows the electrical activity of the same brain with eyes open and
> closed. Red shows most activity and dark blue shows least. The pictures
> are both shaped like circles. In the brain with eyes closed, there's a
> little red at 10, 12, and 2 o'clock and lots of dark blue. In the brain
> with eyes open there's a large roughly rectangular blob of red with
> rounded corners that fills the space between 5 and 7 o'clock. The red at
> 10, 12 and 2 o'clock is much smaller in the eyes open brain and there's
> very little dark blue, although both brains are dark blue around the
> outward edges. . In general there's at least 5 times more electrical
> activity in the eyes open brain.
>
> I wonder what the pattern of electrical activity would look like in a
> blind person's brain. I know we transfer our activity to different parts
> of our brain than the visual receptors, as in touch while reading braille,
> and sound while travelling and listening to books and the environment. I
> wonder, though if the electrical activity in a blind person's brain, no
> matter how smart, ever equals that seen in a sighted person's brain, a
> person who merely has his eyes open.
>
> Yeah, I could google this, or research it, but I'm not all that curious. I
> was just wondering if any of you have ever learned about this or if you
> have comments.
>
> This is the kind of question Cindy Ro enjoys when we discuss. That's not
> why I brought it up, though. It just happened to jump out at me while
> working on this brain book. I can't wait to finish this book and get back
> to good old, easy, old, fiction, no pictures!
>
> Always with love,
>
> Lissi
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