Our perception of the visual space remains stable despite dramatic changes of retinal images across saccades. One possible mechanism underlying this trans-saccadic visual stability is receptive-field (RF) remapping of cortical neurons around the time of saccadic onset. Specifically, some cells in lateral intraparietal (LIP) area, frontal eye fields (FEF), and other brain areas shift or expand their current, pre-saccadic RFs (cRFs) toward their future, post-saccadic RFs (fRFs), even before saccadic onset. This forward remapping have led to the Preview Theory positing that the remapping cells compare retinal images across saccades to judge trans-saccade visual stability. However, other studies show that FEF neurons shift their RFs toward the saccade target (convergent remapping) instead of toward fRFs (forward remapping) and that the convergent remapping may be responsible for attentional modulation at the target. Since different studies used different experimental and analysis protocols, it is unclear whether LIP and FEF cells have both convergent and forward shifts around the time of saccades, and whether the two areas differ in their RF dynamics. To address these questions, we recorded single units from LIP and FEF of three macaques performing a delayed saccade task, and compared RF dynamics between the two areas under matched conditions. We introduced the delay period in order to separate in time the attention/saccade plan from the target onset and the execution of impending saccade. Our preliminary data show that: 1. FEF RFs exhibit two kinds of saccadic remapping, convergent and forward remapping; 2. Convergent remapping is evoked by the presentation of the target for a visually-guided delayed saccade, even in the absence of a CD signal. Because a delayed saccade plan evokes attention in the absence of the actual saccade (Bisley and Goldberg, 2003), we suggest that this remapping resembles the shift of the RFs receptive fields of V4 neurons toward the locus of visual attention (Connor et al. 1997; Tolias et al. 2001); 3. Perisaccadic remapping adds a forward remapping component to the FEF RFs, which shifts remapping towards the forward direction; 4. On average, LIP only exhibits forward remapping (in the presence of CD), and unlike FEF and V4, has no convergent (attentional) remapping.
Mingsha Zhang is a Professor of State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, Beijing Normal University. In his lab, they focus on the understanding of neuronal basis of cognitive functions, such as visual spatial perception, spatial attention, working memory and temporal prediction, etc. They employ visual, oculomotor and manual systems of primates as behavior model to assess how cognitive functions affect the visually guided behaviors as well as the process of sensorimotor transformation. In addition to basic research, he has a keen interest to combine my experience of neuroscience and medicine for clinic research. Currently, he is working on making hemi-Parkinson monkey model to study the neural mechanisms of Parkinson disease, also studying the behavioral and neural deficits of PD patients through making collaboration with clinic physicians. They have successfully made hemi-Parkinson model in monkeys by injection of MPTP (specifically damages dopaminergic neurons in substantial nigra) through one side of internal carotid. With the hemi-Parkinson monkeys, they are able to explore the neural mechanisms of motor and non-motor impairments in Parkinson disease, and evaluate the effect of various treatments including deep brain stimulation (DBS).
Sponsored by the NYU-ECNU Institute of Brain and Cognitive Science at NYU Shanghai