The central aim of the proposed research is to determine the coordinate systems the brain uses for representing the visual environment. In particular we investigate the coordinate system of the cortical map which represents salient objects and locations in the visual environment, and the coordinate system in which predictive remapping of neural activity from LIP takes place. This will advance the development of a monkey model of the human oculomotor system and thereby lay the foundation for future development of diagnostic, prognostic, and rehabilitative strategies for dealing with stroke and other pathologies which damage it. We use saccade adaptation to dissociate the location of a visual target which induces a saccade from the endpoint of the saccade which is made (Mclaughlin 1967), and measure neural activity with single-unit recordings. We run two different experiments in order to identify the two coordinate systems described above. In the first, we place the visual target in the receptive field of a neuron so that the endpoint of the monkey's adapted saccades fall outside the neuron's receptive field. LIP will exhibit neural activity in response to target onset and to the unadapted saccade (Colby et al. 1996). If neural activity persists through saccade adaptation, then the salience map uses visual coordinates;if not it uses motor coordinates. In the second experiment, we flash a peripheral stimulus around the time of a saccade, in the future receptive field of an LIP neuron. LIP neurons exhibit a post-saccadic response to this stimulus in the normal, unadapted situation, indicating predictive remapping of neural activity (Kusunoki &Goldberg 2003). If the post-saccadic response persists after adaptation, then predictive remapping is done in motor coordinates;if not it is tied to the visual stimulus.
This project investigates the way the brain processes information about the visual world and how it updates with new information as the eyes move. Many pathologies, most prominently stroke, disable these brain functions. Since primates have very similar visual systems, understanding these functions in the monkey will facilitate the development of rehabilitative and therapeutic strategies in human patients.
| Steenrod, Sara C; Phillips, Matthew H; Goldberg, Michael E (2013) The lateral intraparietal area codes the location of saccade targets and not the dimension of the saccades that will be made to acquire them. J Neurophysiol 109:2596-605 |
