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

Discussion in 'Optometry Archives' started by andrewedwardjudd, Apr 18, 2005.

  1. 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.

    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:

    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

    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
    andrewedwardjudd, Apr 18, 2005
  2. a few more refs

    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."


    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"


    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
    andrewedwardjudd, Apr 18, 2005
  3. andrewedwardjudd

    retinula Guest

    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?
    retinula, Apr 18, 2005
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