Relation of cortical areas MT and MST to pursuit eye movements. II. Differentiation of retinal from extraretinal inputs

Abstract

1. We investigated cells in the middle temporal visual area (MT) and the medial superior temporal area (MST) that discharged during smooth pursuit of a dim target in an otherwise dark room. For each of these pursuit cells we determined whether the response during pursuit originated from visual stimulation of the retina by the pursuit target or from an extraretinal input related to the pursuit movement itself. We distinguished between these alternatives by removing the visual motion stimulus during pursuit either by blinking off the visual target briefly or by stabilizing the target on the retina. 2. In the foveal representation of MT (MTf), we found that pursuit cells usually decreased their rate of discharge during a blink or during stabilization of the visual target. The pursuit response of these cells depends on visual stimulation of the retina by the pursuit target. 3. In a dorsal-medial region of MST (MSTd), cells continued to respond during pursuit despite a blink or stabilization of the pursuit target. The pursuit response of these cells is dependent on an extraretinal input. 4. In a lateral-anterior region of MST (MST1), we found both types of pursuit cells; some, like those in MTf, were dependent on visual inputs whereas others, like those in MSTd, received an extraretinal input. 5. We observed a relationship between pursuit responses and passive visual responses. MST cells whose pursuit responses were attributable to extraretinal inputs tended to respond preferentially to large-field random-dot patterns. Some cells that preferred small spots also had an extraretinal input. 6. For 92% of the pursuit cells we studied, the pursuit response began after onset of the pursuit eye movement. A visual response preceding onset of the eye movement could be observed in many of these cells if the initial motion of the target occurred within the visual receptive field of the cell and in its preferred direction. In contrast to the pursuit response, however, this visual response was not dependent on execution of the pursuit movement. 7. For the remaining 8% of the pursuit cells, the pursuit discharge began before initiation of the pursuit eye movement. This occurred even though the initial motion of the target was outside the receptive field as mapped during fixation trials. Our data suggest, however, that such responses may be attributable to an expansion of the receptive field that accompanies enhanced visual responses.(ABSTRACT TRUNCATED AT 400 WORDS)

Neurons in cortical area MST remap the memory trace of visual motion across saccadic eye movements

“…These signals are found during smooth pursuit (24)(25)(26)(27) or to modulate neuronal responses in relation to eye positions (28)(29)(30)(31), but it is possible that the extraretinal signals also provide information on saccades in MST. Thus, the results of the present study suggest that visual information before the saccade is retained and localized in spatiotopic coordinates in the upstream visual area(s) and that extraretinal signals coding the saccade-vector trigger its representation as neuronal activity in MST.…”

Multimodal Representation of Space in the Posterior Parietal Cortex and Its Use in Planning Movements

“…MSTd has large receptive fields that are often selective for complex patterns of motion, such as expansion, contraction, rotation, and spiraling motions Sakata et al 1985Sakata et al , 1986Tanaka et al 1986;Graziano et al 1994). This area also receives signals related to smooth pursuit eye movements and vestibularly derived head pursuit signals (Kawano et al 1984, Sakata et al 1983, Newsome et al 1988. Because many of the patterns of motion to which MSTd neurons are selective occur with self-motion, it has been proposed that this area is important for navigation using motion cues Saito et al 1986;Sakata et al 1985;Duffy & Wurtz 1991Geesaman & Andersen 1996;Bradley et al 1996).…”

“…MSTd SIGNALS DIRECTION OF HEADING Because MST receives a pursuit eye movement signal (Sakata et al 1983, Kawano et al 1984, Newsome et al 1988, Thier & Erickson 1992 and has motion pattern-selective cells, it may be a brain center that computes direction of heading using optic flow and pursuit signals. Recently, we have examined how these two signals interact in MSTd.…”

Brain Stem Pursuit Pathways: Dissociating Visual, Vestibular, and Proprioceptive Inputs During Combined Eye-Head Gaze Tracking

“…Neurons within the medial superior temporal sulcus (MST) and frontal eye fields (FEF) have been shown to encode retinal image and/or gaze velocity signals (Fukushima et al 2000;Kawano et al 1984;Komatsu and Wurtz 1988;Newsome et al 1988;Sakata et al 1983). Accordingly, it has been proposed that these structures provide both target velocity-in-space and gaze velocity commands to downstream structures (Fukushima et al 2000;Newsome et al 1988;Tanaka and Fukushima 1998).…”