A Breadth-First Survey of Eye Tracking Applications <s> Attentional Neuroscience <s> Michael I. Posner, Charles R. R. Snyder, and Brian J. DavidsonUniversity of OregonSUMMARYDetection of a visual signal requires information to reach a system capable ofeliciting arbitrary responses required by the experimenter. Detection latencies arereduced when subjects receive a cue that indicates where in the visual field thesignal will occur. This shift in efficiency appears to be due to an alignment (orient-ing) of the central attentional system with the pathways to be activated by thevisual input.It would also be possible to describe these results as being due to a reducedcriterion at the expected target position. However, this description ignores impor-tant constraints about the way in which expectancy improves performance. First,when subjects are cued on each trial, they show stronger expectancy effects thanwhen a probable position is held constant for a block, indicating the active natureof the expectancy. Second, while information on spatial position improves per-formance, information on the form of the stimulus does not. Third, expectancymay lead to improvements in latency without a reduction in accuracy. Fourth,there appears to be little ability to lower the criterion at two positions that arenot spatially contiguous.A framework involving the employment of a limited-capacity attentional mech-anism seems to capture these constraints better than the more general language ofcriterion setting. Using this framework, we find that attention shifts are not closelyrelated to the saccadic eye movement system. For luminance detection the retinaappears to be equipotential with respect to attention shifts, since costs to unex-pected stimuli are similar whether foveal or peripheral. These results appear toprovide an important model system for the study of the relationship between atten-tion and the structure of the visual system.Detecting the presence of a clear signal controlling our awareness of environmentalin an otherwise noise-free environment is events. Although there are a number of em-probably the simplest perceptual act of which pirical approaches to the study of detection,the human is capable. For this reason it may most have not clearly separated between at-serve as an ideal model task for investigating tentional factors and sensory factors and arethe role of sensory and attentional factors in thus incapable of providing an analysis of therelationship between the two.The classical psychophysical approach tothe use ofUniversity of Oregon. Portions of the data were near-threshold signals (e.g., Hecht, Schlaer,adapted from Chronometrk Explorations of Mind & Pirenne, 1942). This approach has been(Posner, 1978). Parts of these experiments were concerned with such stimulus factors as in-rdllV <s> BIB001 </s> A Breadth-First Survey of Eye Tracking Applications <s> Attentional Neuroscience <s> Real-world behavior is typically more complicated than a one-to-one mapping between a stimulus and response; the same stimulus can lead to different behaviors depending on the situation, or the same behavior may be cued by different stimuli. In such cases, knowledge of the formal demands of the task at hand is required. We found that in monkeys trained to alternate between three tasks, the activity of many neurons in the prefrontal cortex was task dependent. This included changes in overall firing rate, in firing-rate profiles (shape of responses over time), and in stimulus and response selectivity. These findings support the hypothesis that a major prefrontal function is the acquisition and implementation of task context and the “rules” used to guide behavior. <s> BIB002 </s> A Breadth-First Survey of Eye Tracking Applications <s> Attentional Neuroscience <s> During normal vision, when subjects attempt to fix their gaze on a small stimulus feature, small fixational eye movements persist. We have recorded the impulse activity of single neurons in primary visual cortex (V1) of macaque monkeys while their fixational eye movements moved the receptive-field activating region (AR) over and around a stationary stimulus. Three types of eye movement activation were found. (1) Saccade cells discharged when a fixational saccade moved the AR onto the stimulus, off the stimulus, or across the stimulus. (2) Position/drift cells discharged during the intersaccadic (drift) intervals and were not activated by saccades that swept the AR across the stimulus without remaining on it. To activate these neurons, it was essential that the AR be placed on the stimulus and many of these cells were selective for the sign of contrast. They had smaller ARs than the other cell types. (3) Mixed cells fired bursts of activity immediately following saccades and continued to fire at a lower rate during intersaccadic intervals. The tendency of each neuron to fire transient bursts or sustained trains of impulses following saccades was strongly correlated with the transiency of its response to stationary flashed stimuli. For one monkey, an extraretinal influence accompanying fixational saccades was identified. During natural viewing, the different eye movement classes probably make different contributions to visual processing. Position/drift neurons are well suited for coding spatial details of the visual scene because of their small AR size and their selectivity for sign of contrast and retinal position. However, saccade neurons transmit information that is ambiguous with respect to the spatial details of the retinal image because they are activated whether the AR lands on a stimulus contour, or the AR leaves or crosses the contour and lands in another location. Saccade neurons may be involved in constructing a stable world in spite of incessant retinal image motion, as well as in suppressing potentially confusing input associated with saccades. <s> BIB003
The dissociation of the "spotlight of attention" BIB001 from ocular fixation poses a problem for eye tracking researchers. It is possible to visually fixate one location while simultaneously diverting attention to another. For example, astronomers perform this fairly regularly when looking for faint stars or star clusters with the naked eye. When examining a scanpath over a visual stimulus, we can often say that specific regions were looked at, perhaps even fixated (following analysis of eye movements), however, we can not be fully confident that these specific regions were fully perceived. There is (currently) no simple way of telling what the brain is doing during a particular visual scan of the scene. Ideally, we would have to not only record the point of one's gaze, but also of one's brain activity. Investigating neuronal activity related to fixational eye movements (saccades and intersaccadic (drift) intervals), BIB003 show that responses of a monkey's V1 neurons to fixational eye movements are specific and diverse. Some cells are activated only by saccades, others discharge during drifts, and most show a mixture of these two influences. The patterns of activity reflect the interactions between the stimulus, the receptive-field activating region, the temporal response characteristics of the neuron, and the retinal positions and image motions imparted by eye movements. The diversity of the activity patterns suggests that during natural viewing of a stationary scene some cortical neurons carry information about saccadic occurrences and directions while other neurons code details of the retinal image. Snodderly et al. argue that, theoretically, saccade neurons could participate in saccadic suppression by inhibiting other neurons that carry stimulus information (reducing signal strength) or by adding noise to the signal, thereby raising thresholds and making stimulus events undetectable at the times of saccades. The prefrontal (PF) cortex is largely thought to be central to the ability of shifting attention and choosing actions appropriate not only to the sensory information at hand but also according to the specific sensory, motor, and cognitive demands of the task (the behavioral context) in which it is encountered BIB002 . Asaad et al. report that most of the 305 neurons recorded in two monkeys displayed a task-dependent change in overall activity, particularly in the fixation interval preceding cue presentation. Results show that, for many PF neurons, activity was influenced by the task being performed. Asaad et al. suggest that formal demands of behavior are represented within PF activity and thus support the hypothesis that one PF function is the acquisition and implementation of task context and the "rules" used to guide behavior.