scholarly journals Activity in monkey lateral intraparietal area reflects saccade direction, saccade latency, and target identification during free visual search

2005 ◽  
Vol 5 (8) ◽  
pp. 99-99
Author(s):  
A. L. Gee ◽  
A. E. Ipata ◽  
J. W. Bisley ◽  
M. E. Goldberg
Keyword(s):  
Visual Search ◽  
Target Identification ◽  
Saccade Latency ◽  
Lateral Intraparietal Area ◽  
Saccade Direction

scholarly journals Where did I come from? Where am I going? Functional influences on visual search fixation duration

2017 ◽  
Vol 10 (1) ◽  
Author(s):  
Harold H. Greene ◽  
James M. Brown
Keyword(s):  
Visual Search ◽  
Real Time ◽  
Fixation Duration ◽  
Search Behavior ◽  
Real Time Simulation ◽  
Fixation Durations ◽  
Total Fixation ◽  
Time Simulation ◽  
Saccade Direction

Real time simulation of visual search behavior can occur only if the control of fixation durations is sufficiently understood.  Visual search studies have typically confounded pre- and post-saccadic influences on fixation duration.  In the present study, pre- and post-saccadic influences on fixation durations were compared by considering saccade direction. Novel use of a gaze-contingent moving obstructer paradigm also addressed relative contributions of both influences to total fixation duration.   As a function of saccade direction, pre-saccadic fixation durations exhibited a different pattern from post-saccadic fixation durations.  Post-saccadic fixations were also more strongly influenced by peripheral obstruction than pre-saccadic fixation durations. This suggests that post-saccadic influences may contribute more to fixation durations than pre-saccadic influences. Together, the results demonstrate that it is insufficient to model the control of visual search fixation durations without consideration of pre- and post-saccadic influences. 

scholarly journals Effect of Inactivation of the Cortical Frontal Eye Field on Saccades Generated in a Choice Response Paradigm

2008 ◽  
Vol 100 (5) ◽  
pp. 2726-2737 ◽  
Author(s):  
Edward L. Keller ◽  
Kyoung-Min Lee ◽  
Se-Woong Park ◽  
Jessica A. Hill
Keyword(s):  
Alternative Interpretation ◽  
Saccade Latency ◽  
Frontal Eye Field ◽  
Choice Response ◽  
Visually Guided ◽  
Eye Field ◽  
Saccade Direction ◽  
Response Task ◽  
Bilateral Lesions

Previous studies using muscimol inactivations in the frontal eye fields (FEFs) have shown that saccades generated by recall from working memory are eliminated by these lesions, whereas visually guided saccades are relatively spared. In these experiments, we made reversible inactivations in FEFs in alert macaque monkeys and examined the effect on saccades in a choice response task. Our task required monkeys to learn arbitrary pairings between colored stimuli and saccade direction. Following inactivations, the percentage of choice errors increased as a function of the number of alternative (NA) pairings. In contrast, the percentage of dysmetric saccades (saccades that landed in the correct quadrant but were inaccurate) did not vary with NA. Saccade latency increased postlesion but did not increase with NA. We also made simultaneous inactivations in both FEFs. The results following bilateral lesions showed approximately twice as many choice errors. We conclude that the FEFs are involved in the generation of saccades in choice response tasks. The dramatic effect of NA on choice errors, but the lack of an effect of NA on motor errors or response latency, suggests that two types of processing are interrupted by FEF lesions. The first involves the formation of a saccadic intention vector from associate memory inputs, and the second, the execution of the saccade from the intention vector. An alternative interpretation of the first result is that a role of the FEFs may be to suppress incorrect responses. The doubling of choice errors following bilateral FEF lesions suggests that the effect of unilateral lesions is not caused by a general inhibition of the lesioned side by the intact side.

scholarly journals Been There, Seen That: A Neural Mechanism for Performing Efficient Visual Search

2009 ◽  
Vol 102 (6) ◽  
pp. 3481-3491 ◽  
Author(s):  
Koorosh Mirpour ◽  
Fabrice Arcizet ◽  
Wei Song Ong ◽  
James W. Bisley
Keyword(s):  
Visual Search ◽  
Neural Mechanism ◽  
Saliency Map ◽  
Lateral Intraparietal Area ◽  
Goal Selection ◽  
Reward Expectancy ◽  
Irrelevant Distractors ◽  
Saliency Map Models ◽  
Task Irrelevant ◽  
Foraging Task

In everyday life, we efficiently find objects in the world by moving our gaze from one location to another. The efficiency of this process is brought about by ignoring items that are dissimilar to the target and remembering which target-like items have already been examined. We trained two animals on a visual foraging task in which they had to find a reward-loaded target among five task-irrelevant distractors and five potential targets. We found that both animals performed the task efficiently, ignoring the distractors and rarely examining a particular target twice. We recorded the single unit activity of 54 neurons in the lateral intraparietal area (LIP) while the animals performed the task. The responses of the neurons differentiated between targets and distractors throughout the trial. Further, the responses marked off targets that had been fixated by a reduction in activity. This reduction acted like inhibition of return in saliency map models; items that had been fixated would no longer be represented by high enough activity to draw an eye movement. This reduction could also be seen as a correlate of reward expectancy; after a target had been identified as not containing the reward the activity was reduced. Within a trial, responses to the remaining targets did not increase as they became more likely to yield a result, suggesting that only activity related to an event is updated on a moment-by-moment bases. Together, our data show that all the neural activity required to guide efficient search is present in LIP. Because LIP activity is known to correlate with saccade goal selection, we propose that LIP plays a significant role in the guidance of efficient visual search.

Item-based selection is in good shape in visual compound search: A view from electrophysiology

2017 ◽  
Vol 40 ◽  
Author(s):  
Thomas Töllner ◽  
Dragan Rangelov
Keyword(s):  
Visual Search ◽  
Target Identification ◽  
Search Behaviour ◽  
Single Item ◽  
Good Shape ◽  
Unit Of Selection

AbstractWe argue that although the framework put forward by Hulleman & Olivers (H&O) can successfully explain much of visual search behaviour, it appears limited to tasks without precise target identification demands. In particular, we contend that the unit of selection may be larger than a single item in standard detection tasks, whereas the unit may mandatorily be item-based in compound tasks.

scholarly journals Perceptual and motor processing stages identified in the activity of macaque frontal eye field neurons during visual search

1996 ◽  
Vol 76 (6) ◽  
pp. 4040-4055 ◽  
Author(s):  
K. G. Thompson ◽  
D. P. Hanes ◽  
N. P. Bichot ◽  
J. D. Schall
Keyword(s):  
Visual Search ◽  
Search Display ◽  
Saccade Latency ◽  
Frontal Eye Field ◽  
Visual Response ◽  
Response Latencies ◽  
Target Discrimination ◽  
Motor Processing ◽  
Eye Field ◽  
Saccade Programming

1. The latency between the appearance of a popout search display and the eye movement to the oddball target of the display varies from trial to trial in both humans and monkeys. The source of the delay and variability of reaction time is unknown but has been attributed to as yet poorly defined decision processes. 2. We recorded neural activity in the frontal eye field (FEF), an area regarded as playing a central role in producing purposeful eye movements, of monkeys (Macaca mulatta) performing a popout visual search task. Eighty-four neurons with visually evoked activity were analyzed. Twelve of these neurons had a phasic response associated with the presentation of the visual stimulus. The remaining neurons had more tonic responses that persisted through the saccade. Many of the neurons with more tonic responses resembled visuomovement cells in that they had activity that increased before a saccade into their response field. 3. The visual response latencies of FEF neurons were determined with the use of a Poisson spike train analysis. The mean visual latency was 67 ms (minimum = 35 ms, maximum = 138 ms). The visual response latencies to the target presented alone, to the target presented with distractors, or to the distractors did not differ significantly. 4. The initial visual activation of FEF neurons does not discriminate the target from the distractors of a popout visual search stimulus array, but the activity evolves to a state that discriminates whether the target of the search display is within the receptive field. We tested the hypothesis that the source of variability of saccade latency is the time taken by neurons involved in saccade programming to select the target for the gaze shift. 5. With the use of an analysis adapted from signal detection theory, we determined when the activity of single FEF neurons can reliably indicate whether the target or distractors are present within their response fields. The time of target discrimination partitions the reaction time into a perceptual stage in which target discrimination takes place, and a motor stage in which saccade programming and generation take place. The time of target discrimination occurred most often between 120 and 150 ms after stimulus presentation. 6. We analyzed the time course of target discrimination in the activity of single cells after separating trials into short, medium, and long saccade latency groups. Saccade latency was not correlated with the duration of the perceptual stage but was correlated with the duration of the motor stage. This result is inconsistent with the hypothesis that the time taken for target discrimination, as indexed by FEF neurons, accounts for the wide variability in the time of movement initiation. 7. We conclude that the variability observed in saccade latencies during a simple visual search task is largely due to postperceptual motor processing following target discrimination. Signatures of both perceptual and postperceptual processing are evident in FEF. Procrastination in the output stage may prevent stereotypical behavior that would be maladaptive in a changing environment.

About saccade generation in reading

1999 ◽  
Vol 22 (4) ◽  
pp. 702-703 ◽  
Author(s):  
Françoise Vitu
Keyword(s):  
Eye Movement ◽  
Visual Analysis ◽  
Visual Stimulation ◽  
Word Identification ◽  
Saccade Latency ◽  
Low Level ◽  
Movement Data ◽  
Saccade Direction ◽  
High Level ◽  
Saccade Generation

In their model, Findlay & Walker propose that where and when the eyes move is determined by two relatively independent processing streams. Whereas both saccade direction and amplitude result from a low-level visual analysis of the peripheral visual stimulation, saccade latency results mainly from higher-level processes related to processing of the central information. In the present commentary, reading eye movement data are put forward as evidence against a strict autonomy of “Where” and “When” processing streams. First, saccade direction and amplitude might be modified by high-level processes related to word identification. Second, the direction of a saccade directly affects its latency.

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