Hemispheric representation of the central retina of commissurotomized subjects

Sugishita, Morihiro; Hamilton, Charles R.; Sakuma, Ichiro; Hemmi, Isao

doi:10.1016/0028-3932(94)90086-8

Cited by 56 publications

(26 citation statements)

References 20 publications

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“…The visual stimulus presented to one visual hemifield was lateralized to the contralateral hemisphere through the constraint of eye movement within the fixation window, on the basis that each visual hemifield is both anatomically and functionally represented in the contralateral hemisphere, except for a stripe of 1°( that is, 0.5°from the fovea) or narrower at the vertical meridian [39][40][41] . We confirmed the restriction of visual input to one hemiarticles Fig.…”

Section: Discussionmentioning

confidence: 99%

BDNF upregulation during declarative memory formation in monkey inferior temporal cortex

et al. 2000

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In primates, visual long-term memory of objects is presumably stored in the inferior temporal (IT) cortex. Because brain-derived neurotrophic factor (BDNF) is involved in activity-dependent neural reorganization, we tested the hypothesis that BDNF would be upregulated in IT cortex during formation of visual pair-association memory. To eliminate genetic and cognitive variations between individual animals, we used split-brain monkeys for intra-animal comparison in PCR-based mRNA quantitation. The monkeys learned a pair-association (PA) task using one hemisphere and a control visual task using the other, to balance the amount of visual input. We found that BDNF was upregulated selectively in area 36 of IT cortex during PA learning, but not in areas involved in earlier stages of visual processing. In situ hybridization showed that BDNF-expressing cells were localized in a patchlike cluster. The results suggest that BDNF contributes to reorganization of neural circuits for visual long-term memory formation in the primate.

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Section: Discussionmentioning

confidence: 99%

BDNF upregulation during declarative memory formation in monkey inferior temporal cortex

et al. 2000

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“…It was found that targets in the same visual field as the reference were readily matched, but accuracy was only at chance levels for targets in the opposite field. These results were interpreted as indicating that the patient's fovea was effectively split with respect to the left and right cerebral hemispheres (see also Sugishita, Hamilton, Sakuma, & Hemmi, 1994). In a recent study with healthy observers, visual targets presented to the LVF and RVF evoked responses in the contralateral occipital (and medial parietal) areas, even when the horizontal eccentricity was 08 (Portin & Hari, 1999).…”

Section: The Cortical Representation Of the Foveamentioning

confidence: 90%

A Magnetic Stimulation Examination of Orthographic Neighborhood Effects in Visual Word Recognition

Lavidor

Walsh

2003

Journal of Cognitive Neuroscience

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Abstract& The split-fovea theory proposes that visual word recognition is mediated by the splitting of the foveal image, with letters to the left of fixation projected to the right hemisphere (RH) and letters to the right of fixation projected to the left hemisphere (LH). We applied repetitive transcranial magnetic stimulation (rTMS) over the left and right occipital cortex during a lexical decision task to investigate the extent to which word recognition processes could be accounted for according to the split-fovea theory. Unilateral rTMS significantly impaired lexical decision latencies to centrally presented words, supporting the suggestion that foveal representation of words is split between the cerebral hemispheres rather than bilateral. Behaviorally, we showed that words that have many orthographic neighbors sharing the same initial letters (''lead neighbors'') facilitated lexical decision more than words with few lead neighbors. This effect did not apply to end neighbors (orthographic neighbors sharing the same final letters). Crucially, rTMS over the RH impaired lead-, but not end-neighborhood facilitation. The results support the split-fovea theory, where the RH has primacy in representing lead neighbors of a written word. &

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“…Consequently, although the clear intention of researchers using lateralised stimuli to study hemispheric function is to ensure that participants are fixating the central point throughout each stimulus display, there is now ample evidence that, without precise control, central fixation is unlikely to occur on even the majority of trials in an experiment using lateralised stimuli (e.g., Batt, Underwood, & Bryden, 1995;Findlay & Kapoula, 1992;B. Jones & Santi, 1978;Jordan & Monteiro, 2002;Jordan, Patching, & Milner, 1998;Sugishita, Hamilton, Sakuma, & Hemmi, 1994).…”

Section: University Of Nottingham Ukmentioning

confidence: 98%

Asymmetries and Eccentricities in Studies of Lateralised Word Recognition: A Response to Nazir

Jordan

Patching

Thomas

2003

Cognitive Neuropsychology

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The anatomical arrangement of the human visual system offers considerable scope for investigating functional asymmetries in hemispheric processing. In particular, because each hemisphere receives information initially from the contralateral visual hemifield, visual stimuli presented to the left of a central fixation point can be projected directly to the right hemisphere and visual stimuli presented to the right of a central fixation point can be projected directly to the left hemisphere. Numerous studies using displays of this type suggest that, for the vast majority of individuals, written words produce different patterns of performance when presented to different hemifields and these findings have inspired considerable debate about the processes available for word recognition in each hemisphere.

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Hemispheric representation of the central retina of commissurotomized subjects

Cited by 56 publications

References 20 publications

BDNF upregulation during declarative memory formation in monkey inferior temporal cortex

BDNF upregulation during declarative memory formation in monkey inferior temporal cortex

A Magnetic Stimulation Examination of Orthographic Neighborhood Effects in Visual Word Recognition

Asymmetries and Eccentricities in Studies of Lateralised Word Recognition: A Response to Nazir

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