Poster F117, Tuesday, March 28, 8:00 – 10:00 am, Pacific Concourse
AudioVisual Integration and Training in Hemianopia: A Neurocomputational Study
Elisa Magosso1, Caterina Bertini1, Cristiano Cuppini1, Mauro Ursino1; 1University of Bologna, Italy
Hemianopic patients manifest a loss of conscious vision in one hemifield, generally resulting from unilateral lesion to striate cortex (V1). Behavioral data suggest that these patients may enormously benefit from multisensory audiovisual integration, both ‘online’ and ‘offline’. As to online effects, visual detection in the blind hemifield improves when the visual stimuli are concurrently presented with spatially coincident auditory stimuli. As to offline effects, visual performances ameliorate after a training with systematic congruent audiovisual stimulation in the blind hemifield. To enhance comprehension of the underlying neural mechanisms, we propose a neurocomputational model embracing the retino-striate-extrastriate (primary) visual pathway, the retino-colliculo-extrastriate (secondary) visual pathway and the auditory cortex. The Superior Colliculus integrates visual and auditory information and projects back to the cortices. Hemianopia is simulated by unilaterally lesioning V1; conscious vision is assumed to depend on extrastriate activation. The model reproduces: a) Loss of conscious vision in the blind hemifield, due to damage of primary visual pathway and weakness of the secondary one. b) The online effect of multisensory stimulation on visual detection, ascribing it to multisensory enhancement of SC activation, which triggers extrastriate activation. c) The offline effects of the multisensory training, by applying Hebbian synaptic rules. Post-training visual improvements are ascribed to synaptic reinforcement along the secondary retino-colliculo-extrastriate pathway. The model provides a coherent framework for interpretation of behavioral multisensory effects in hemianopia; moreover, by simulating different paradigms of training (audiovisual/visual, with/without top-down attention towards the blind hemifield) can predict different forms and levels of rehabilitation.
Topic Area: PERCEPTION & ACTION: Multisensory