Jim Bromer wrote:
On Wed, Jul 30, 2008 at 9:50 AM, Mark Waser <[EMAIL PROTECTED]> wrote:
Wow! The civility level on this list is really bottoming out . . . . along
with any sort of scientific grounding.
Experimental (imaging) evidence shows that known words will strongly
activate some set of neurons when heard. Unknown words with recognizable
parts/features will also activate some other set of neurons when heard,
possibly allowing the individual to puzzle out the meaning even if the word
has never been heard before. Totally unknown words will not strongly
activate any neurons -- except subsequently (i.e. on a delay) some set of
HUH? neurons.
Well, your imaging evidence is part imaging and part imagining since
no one knows what the imaging is actually showing. I think it is
commonly believed that the imaging techniques show blood flow into
areas of the brain, and this is (reasonably in my view) taken as
evidence of neural activity. Ok, but what kind of thinking is actually
going on and how extensive are the links that don't have enough wow
factor for repeatable experiments researchers to issue as a press
release. So if you are going to claim that you're speculations are
superiorly grounded, I would like to see some research that shows
that unknown words will not strongly activate any neurons. Take your
time, I am only asking a question, not challenging you to fantasy
combat.
There are many such studies. It appears that activation is strong in
semantic areas when words are involved, but only in the phoneme-grapheme
mapping areas when nonwords are involved. If something in the brain is
monitoring the strength of activation in the semantic area, it would be
able to extract a "feeling of knowing" signal.
There are also studies of "feeling of knowing" in episodic memory, and
also work on being able to distinguish syntactically correct sentences
from incorrect ones.
The common thread in all of these studies is that gross differences of
processing can be found between recognition of known and unknown items,
whether those items be at the word level or higher.
And the common interpretation of these results seems to be that strong
activation occurs in the expected area when the item is known .... which
means that it would be easy for the system to conclude that the
*absence* of such strong activation can be taken to mean that the item
is not known.
I have copied one example of such a paper below (title and abstract
only). This is about the word-nonword case, but as I have said before,
the interpretation does generalize easily to higher cases such as
recognizing that you do not know the answer to a question.
Richard Loosemore
Neural Correlates of Lexical Access During Visual Word Recognition,
Binder, J.R., McKiernan, K.A., Parsons, M.E. , Westbury, C.F., Possing,
E.T., Kaufman, J.N., Buchanan, L.J., Cogn. Neurosci..2003; 15: 372-393
People can discriminate real words from nonwords even when the latter
are orthographically and phonologically word-like, presumably because
words activate specific lexical and/or semantic information. We
investigated the neural correlates of this identification process using
event-related functional magnetic resonance imaging (fMRI). Participants
performed a visual lexical decision task under conditions that
encouraged specific word identification: Nonwords were matched to words
on orthographic and phonologic characteristics, and accuracy was
emphasized over speed. To identify neural responses associated with
activation of nonsemantic lexical information, processing of words and
nonwords with many lexical neighbors was contrasted with processing of
items with no neighbors. The fMRI data showed robust differences in
activation by words and word-like nonwords, with stronger word
activation occurring in a distributed, left hemisphere network
previously associated with semantic processing, and stronger nonword
activation occurring in a posterior inferior frontal area previously
associated with grapheme-to-phoneme mapping. Contrary to lexicon-based
models of word recognition, there were no brain areas in which
activation increased with neighborhood size. For words, activation in
the left prefrontal, angular gyrus, and ventrolateral temporal areas was
stronger for items without neighbors, probably because accurate
responses to these items were more dependent on activation of semantic
information. The results show neural correlates of access to specific
word information. The absence of facilitatory lexical neighborhood
effects on activation in these brain regions argues for an
interpretation in terms of semantic access. Because subjects performed
the same task throughout, the results are unlikely to be due to
task-specific attentional, strategic, or expectancy effects.
-------------------------------------------
agi
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