Activity in the Lateral Intraparietal Area Predicts the Goal and Latency of Saccades in a Free-Viewing Visual Search Task (original) (raw)
Related papers
2006
Neural activity in the lateral intraparietal area (LIP) has been associated with attention to a location in visual space, and with the intention to make saccadic eye movement. In this study we show that neurons in LIP respond to recently flashed task-irrelevant stimuli and saccade targets brought into the receptive field by a saccade, although they respond much to the same stimuli when they are stable in the environment. LIP neurons respond to the appearance of a flashed distractor even when a monkey is planning a memory-guided delayed saccade elsewhere. We then show that a monkey's attention, as defined by an increase in contrast sensitivity, is pinned to the goal of a memory-guided saccade throughout the delay period, unless a distractor appears, in which case attention transiently moves to the site of the distractor and then returns to the goal of the saccade. LIP neurons respond to both the saccade goal and the distractor, and this activity correlates with the monkey's locus of attention. In particular, the activity of LIP neurons predicts when attention migrates from the distractor back to the saccade goal. We suggest that the activity in LIP provides a salience map that is interpreted by the oculomotor system as a saccade goal when a saccade is appropriate, and simultaneously is used by the visual system to determine the locus of attention.
Annals of the New York Academy of Sciences, 2002
The brain cannot monitor or react towards the entire world at a given time. Instead, using the process of attention, it selects objects in the world for further analysis. Neuronal activity in the monkey intraparietal area has the properties appropriate for a neuronal substrate of attention: instead of all objects being represented in the parietal cortex, only salient objects are. Such objects can be salient because of their physical properties (recently flashed objects or moving objects) or because they can be made important to the animal by virtue of a task. Although lateral intraparietal area (LIP) neurons respond through the delay period of a memory-guided saccade, they also respond in an enhanced manner to distractors flashed during the delay period of a memoryguided saccade being generated to a position outside the receptive field. This activity parallels the monkey's psychophysical attentional process: attention is ordinarily pinned at the goal of a memory-guided saccade, but it shifts briefly to the locus of a task-irrelevant distractor flashed briefly during the delay period and then returns to the goal. Although neurons in LIP have been implicated as being directly involved in the generation of saccadic eye movements, their activity does not predict where, when, or if a saccade will occur. The ensemble of activity in LIP, however, does accurately describe the locus of attention.
Activity in V4 Reflects the Direction, But Not the Latency, of Saccades During Visual Search
Journal of Neurophysiology, 2010
We constantly make eye movements to bring objects of interest onto the fovea for more detailed processing. Activity in area V4, a prestriate visual area, is enhanced at the location corresponding to the target of an eye movement. However, the precise role of activity in V4 in relation to these saccades and the modulation of other cortical areas in the oculomotor system remains unknown. V4 could be a source of visual feature information used to select the eye movement, or alternatively, it could reflect the locus of spatial attention. To test these hypotheses, we trained monkeys on a visual search task in which they were free to move their eyes. We found that activity in area V4 reflected the direction of the upcoming saccade but did not predict the latency of the saccade in contrast to activity in the lateral intraparietal area (LIP). We suggest that the signals in V4, unlike those in LIP, are not directly involved in the generation of the saccade itself but rather are more closely ...
Cerebral Cortex, 2004
The monkey's lateral intraparietal area (LIP) has been associated with attention and saccades. LIP neurons have visual on-responses to objects abruptly appearing in their receptive fields (RFs) and sustained activity preceding saccades to the RF. We studied the relationship between the on-responses and delay activity in LIP using a 'stable-array' task. Monkeys viewed eight distinct, continuously illuminated objects, arranged in a circle with at least one object in the RF. A cue flashed instructing the monkey to make a saccade, after a delay, to the stable object physically matching the cue. The location of the cue was fixed in trial blocks, either in or out of the RF. If the cue was outside the RF, neurons developed delay-period activity tuned for the direction of the saccade target at 190 ms after cue onset. If the cue appeared in the RF, neurons initially responded to cue onset and developed tuning for saccade direction only toward the end of the delay period, 390 ms after cue onset. The cue-and saccade-target responses coexisted throughout a significant portion of the delay period. The results show that visual-on responses and delay-period activity in LIP are functionally separable, and that, although highly selective, the salience representation in LIP can contain more than one object at a time.
Initial saccades predict manual recognition choices in the monkey
Vision research, 2006
In animals with specialized foveae, eye position has a direct influence over the acquisition of detailed visual information. At the same time, eye movements executed during natural behaviors are closely linked with motor actions. In this study, we investigated patterns of eye movements during a simple visual discrimination task. Three rhesus monkeys learned to recognize images of real world objects with no explicit constraints on eye position. Analysis of the monkeys' eye movements showed that although the endpoint of the initial saccade depended on the particular visual stimulus, the trajectory of the first saccades also reliably predicted the manual response associated with that stimulus. We thus observed that initial saccades executed in a recognition task reflect both perceptual and motor aspects of a visual task. This pattern of eye movements emerged spontaneously in all three animals tested despite the fact that saccades were never explicitly rewarded. As the average sacca...
Primates perform saccadic eye movements in order to bring the image of an interesting target onto the fovea. Compared to stationary targets, saccades toward moving targets are computationally more demanding since the oculomotor system must use speed and direction information about the target as well as knowledge about its own processing latency to program an adequate, predictive saccade vector. In monkeys, different brain regions have been implicated in the control of voluntary saccades, among them the lateral intraparietal area (LIP). Here we asked, if activity in area LIP reflects the distance between fovea and saccade target, or the amplitude of an upcoming saccade, or both. We recorded single unit activity in area LIP of two macaque monkeys. First, we determined for each neuron its preferred saccade direction. Then, monkeys performed visually guided saccades along the preferred direction toward either stationary or moving targets in pseudo-randomized order. LIP population activity allowed to decode both, the distance between fovea and saccade target as well as the size of an upcoming saccade. Previous work has shown comparable results for saccade direction (Graf and Andersen, 2014a,b). Hence, LIP population activity allows to predict any two-dimensional saccade vector. Functional equivalents of macaque area LIP have been identified in humans. Accordingly, our results provide further support for the concept of activity from area LIP as neural basis for the control of an oculomotor brain-machine interface.
Journal of neurophysiology, 1998
To determine the role of the dorsolateral prefrontal cortex (PFC) in the selection of memory-guided saccadic eye movements, we recorded the activities of PFC neurons while macaque monkeys performed an oculomotor delayed matching-to-sample task. The task was designed to dissociate motor factors from visual factors in the selection and retention of the direction of the forthcoming saccade during delay periods after the visual cue but before the GO signal was presented. While the monkey fixated on a central fixation spot (FX period, 1 s), a sample cue (1 of 4 geometric figures) and a matching cue composed of two geometric figures were presented in succession (SC and MC periods, respectively, 0.5 s) with a brief delay (D1 period, 1 or 1.5 s). After another delay (D2 period, 1.5 s), the monkey made a saccade (GO period, <0.5 s) toward one of four locations (the goal) that had been indicated by the combination of the sample and matching cues in the MC period. We recorded the activities...
Journal of neurophysiology, 2000
The aim of this study was to determine whether neuronal activity in the macaque supplementary eye field (SEF) is influenced by the rule used for saccadic target selection. Two monkeys were trained to perform a variant of the memory-guided saccade task in which any of four visible dots (rightward, upward, leftward, and downward) could be the target. On each trial, the cue identifying the target was either a spot flashed in superimposition on the target (spatial condition) or a foveally presented digitized image associated with the target (pattern condition). Trials conforming to the two conditions were interleaved randomly. On recording from 439 SEF neurons, we found that two aspects of neuronal activity were influenced by the nature of the cue. 1) Activity reflecting the direction of the impending response developed more rapidly following spatial than following pattern cues. 2) Activity throughout the delay period tended to be higher following pattern than following spatial cues. We...
Functional imaging of the intraparietal cortex during saccades to visual and memorized targets
NeuroImage, 2006
The representation of perceived space and intended actions in the primate parietal cortex has been the subject of considerable debate. To address this issue, we used the quantitative 14 C-deoxyglucose method to obtain maps of the activity pattern in the intraparietal cortex of rhesus monkeys executing saccades to visual and memorized targets. The principal effect induced by memory-guided saccades was found more caudally in the deepest part of the middle third of the lateral bank (within area LIPv) whereas that induced by visually guided saccades extended more rostrally and superficially in the anterior third of the bank (within area LIPd). The memory-saccade-related and the visualsaccade-related regions of activation overlapped only within area LIPv. Besides saccade execution, maximal activity in area LIPd required a visual stimulus. The region activated by visual fixation was located at the border of LIPv and LIPd, extending mainly within area LIPd, and occupying about one third of the neural space of the region activated for visual-saccades. We suggest that the lateral intraparietal cortex represents visual and motor space in segregated, albeit partially overlapping, regions.
Saccade Planning Evokes Topographically Specific Activity in the Dorsal and Ventral Streams
Saccade planning may invoke spatially-specific feedback signals that bias early visual activity in favor of top-down goals. We tested this hypothesis by measuring cortical activity at the early stages of the dorsal and ventral visual processing streams. Human subjects maintained saccade plans to (prosaccade) or away (antisaccade) from a spatial location over long memory-delays. Results show that cortical activity persists in early visual cortex at the retinotopic location of upcoming saccade goals. Topographically specific activity persists as early as V1, and activity increases along both dorsal (V3A/B, IPS0) and ventral (hV4, VO1) visual areas. Importantly, activity persists when saccade goals are available only via working memory and when visual targets and saccade goals are spatially disassociated. We conclude that top-down signals elicit retinotopically specific activity in visual cortex both in the dorsal and ventral streams. Such activity may underlie mechanisms that prioritize locations of task-relevant objects. for help with data collection; Shani Offen and David Heeger for helpful discussions on data analyses; Justin Gardner for help with analytic software; Jonathan Winawer for help with ventral visual mapping; Wayne Mackey for help scoring the saccade behavior; and Marisa Carrasco and Sam Ling for comments on early versions of the paper.