Asymmetrical activation of human visual cortex demonstrated by functional MRI with monocular stimula

I have reported here a few times that I have observed that patching one
eye appears to stimulate the opposite hemisphere because verbal
responses to questions seem to reflect left/right brain differences.
(http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=8258284
and http://www.cerebromente.org.br/n14/mente/lateralization.htm)

This effect is sometimes so strong, that it was hard to believe it had
never been reported scientifically.

I found this article for monocular viewing:

http://www.ncbi.nlm.nih.gov/entrez/...ve&db=PubMed&list_uids=11506536&dopt=Abstract

Toosy AT, Werring DJ, Plant GT, Bullmore ET, Miller DH, Thompson AJ.

NMR Research Unit, Institute of Neurology, Queen Square, London WC1N
3BG, United Kingdom.

We have demonstrated asymmetric activation patterns in the visual
cortices of normal humans who have undergone functional MRI with
monocular photic stimulation. The contralateral hemisphere is activated
more strongly and to a greater spatial extent than the ipsilateral
hemisphere when either eye is stimulated. This asymmetry can be
explained by nasotemporal asymmetries which have been described in
anatomical studies of the visual system in primates and humans. In
part, the representation of the monocular crescent of the temporal
hemifield of either eye, which exists only in the crossed projection,
may explain this. In addition, within the binocular field, there is a
biased crossed projection of nasal retinal ganglion cells which drive
the contralateral ocular dominance columns in V1. Finally, the blind
spot representation in the ipsilateral visual cortex may also
contribute to the observed asymmetries. Our study may in effect provide
a functional correlate of the anatomical asymmetries that have been
observed in humans and animals.

-----------------------------------------------------

And this article for viewing either left or right sides when wearing a
bi nasal patch. (Lateral stimulation). But I just used a simple
patch.

http://www.ncbi.nlm.nih.gov/entrez/...ve&db=pubmed&dopt=Abstract&list_uids=15246450

Lateral visual field stimulation reveals extrastriate cortical
activation in the contralateral hemisphere: an fMRI study.

Schiffer F, Mottaghy FM, Pandey Vimal RL, Renshaw PF, Cowan R,
Pascual-Leone A, Teicher M, Valente E, Rohan M.

Department of Psychiatry, Harvard Medical School, and the Developmental
Biopsychiatry Research Program, McLean Hospital, 115 Mill Street,
Belmont, MA 02478, USA.

We examined whether lateral visual field stimulation (LSTM) could
activate contralateral extrastriate cortical areas as predicted by a
large experimental literature. We asked seven unscreened, control
subjects to wear glasses designed to allow vision out of either the
left (LVF) or right lateral visual field (RVF) depending upon which
side the subject looked toward. Each subject participated in a block
design functional magnetic resonance imaging (fMRI) study with
alternating 30-s epochs in which he was asked to look to one side and
then the other for a total of five epochs. On each side of the bore of
the scanner, we taped a photograph for the subject to view in the LVF
and RVF. The data were analyzed with SPM99 using a fixed effect,
box-car design with contrasts for the LVF and the RVF conditions. Both
LVF and RVF conditions produced the strongest fMRI activation in the
contralateral occipitotemporal and posterior parietal areas as well as
the contralateral dorsolateral prefrontal cortex. LSTM appears to
increase contralateral fMRI activation in striate and extrastriate
cortical areas as predicted by earlier studies reporting differential
cognitive and/or emotional effects from unilateral sensory or motor
stimulation.

 

a few more refs

http://www.ncbi.nlm.nih.gov/entrez/...ve&db=pubmed&dopt=Abstract&list_uids=11586061

Functional Magnetic Resonance Imaging of Eye Dominance at 4 Tesla


"In both the individual and group analyses, the anterior striate cortex
was consistently activated by the contralateral eye more than the
ipsilateral eye. Additionally, we found evidence that there were areas
in the bilateral LGN which were more active during the stimulation of
the contralateral eye than during the stimulation of the ipsilateral
eye. The activated areas were reproducible, and the mean ratio of the
overlapping area was 0.71 for the repeated scans. The additional
experiment revealed that the area in the anterior visual cortex could
be divided into two parts, one truly monocular and the other relatively
monocular. Our finding confirmed previous fMRI results at 1.5 tesla
showing that eye dominance was observed in the contralateral anterior
visual cortex. However, the eye dominance in the visual cortex was
found not only in the most anterior area corresponding to the monocular
temporal crescent but also in the more posterior area, presumably
showing the greater sensitivity of the temporal visual field (nasal
retina) as compared with the nasal visual field (temporal retina) in
the peripheral visual field (peripheral retina). In addition, it is
suggested that the nasotemporal asymmetry of the retina and the visual
fields is represented in the LGN as well as in the visual cortex."

-------------------------


http://www.ncbi.nlm.nih.gov/entrez/...ve&db=pubmed&dopt=Abstract&list_uids=11124303

Am J Ophthalmol. 2000 Dec;130(6):821-4. Related Articles, Links


Contralateral monocular dominance in anterior visual cortex confirmed
by functional magnetic resonance imaging.

"PURPOSE: Although it is known that the damage to anterior striate
cortex results in temporal peripheral visual field loss of the
contralateral eye in patients with cerebral visual disturbance, the
monocularity of anterior striate cortex has not been demonstrated in
normal living humans"

--------------------------

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=7741877

Am J Ophthalmol. 1995 Mar;119(3):345-9.

The missing temporal crescent.

Landau K, Wichmann W, Valavanis A.

Department of Ophthalmology, University Hospital, Zurich, Switzerland.

PURPOSE: We studied clinically the representation of the monocular
temporal crescent in the human visual cortex and noted the importance
of using the perimetric techniques best suited to detect this visual
field defect and to study patients in whom the temporal crescent is
missing. METHODS: Goldmann perimetry and high-resolution magnetic
resonance imaging were performed in two patients with vascular lesions
located in the anterior striate cortex. RESULTS: A monocular visual
field defect, the missing temporal crescent, was found on the side
contralateral to the lesion. CONCLUSIONS: The perimetric-magnetic
resonance imaging correlation is in exquisite agreement with recent
information about the representation of the visual field in the human
primary visual cortex. Reports of this specific perimetric finding are
rare, in part because of underdetection with currently used perimetric
techniques that concentrate on the central 30 degrees of the visual
field.

 

why did you post this? are you trying to show off your big brain or
something? who cares whether some casual observations that you have
made in the past happen to be the topic of some real research done by
some real investigators? are you seeking approval again Andrew?