John <johnhkm at netsprintxxxx.net.au> wrote:
: I don't know why the finding the brain cyst solved the puzzle of this case.
: Okay, in memory area, but that's not explaining anything.
: Can anyone help me with this???
A fimbria/fornix lesion acts as a functional hippocampus
lesion because it prevent colineriginc inervation from
the medial septum to reach its targets in the hippocampus.
This has consequnces for the theta and gamma osciallations
(J. Neurosci., 1999, 30, 3223-3237; Nature, 1998, 394, 186-189).
A 'cheap' way to produce hippocampal lesions in rats is
to transect the fornix, however, the effects of fornix damage
and hippocampus lesions is not 100% similar. For example,
fornix lesions affect path-integration and delayed
nonmatching-to-sample, which is unaffected by hippocampal
ablation. Hippocampal lesions affect latent inhibition,
which is unaffected by fornix lesions. Cerebral ischemia,
which produce amnesia, affects delayed nonmatching-to-sample
as well.
The article on the website says nothing about the exact
nature of the amnesia. A complete fornix lesion produce
anterograde amnesia, however, there are no indications
of this in the article. It could be a form of temporally
graded retrograde amnesia (a 'time laps'). 'Mistaking the
present for the past' is a poor behavioural diagnosis, I
don't think it makes much sence at all.
Sturla Molden
