Oculomotor target selection is mediated by complex objects

Abstract

Oculomotor target selection often requires discriminating visual features, but it remains unclear how oculomotor substrates encoding saccade vectors functionally contribute to this process. One possibility is that oculomotor vector representations (observed directly as physiological activation or inferred from behavioral interference) of potential targets are continuously re-weighted by task-relevance computed elsewhere in specialized visual modules, while an alternative possibility is that oculomotor modules utilize local featural analyses to actively discriminate potential targets. Strengthening the former account, oculomotor vector representations have longer onset latencies for ventral- (i.e., color) than dorsal-stream features (i.e., luminance), suggesting that oculomotor vector representations originate from featurally-relevant specialized visual modules. Here, we extended this reasoning by behaviorally examining whether the onset latency of saccadic interference elicited by visually complex stimuli is greater than is commonly observed for simple stimuli. We measured human saccade metrics (saccade curvature, endpoint deviations, saccade frequency, error proportion) as a function of time after abrupt distractor onset. Distractors were novel, visually complex, and had to be discriminated from targets to guide saccades. The earliest saccadic interference latency was ~110 ms, considerably longer than previous experiments, suggesting that sensory representations projected into the oculomotor system are gated to allow for sufficient featural processing to satisfy task demands. Surprisingly, initial oculomotor vector representations encoded features, as we manipulated the visual similarity between targets and distractors and observed increased vector modulation response magnitude and duration when the distractor was highly similar to the target. Oculomotor vector modulation was gradually extinguished over the time course of the experiment.

The role of temporal cortex in the control of attention

“…Most of the previous studies which missed attentional control signals in the temporal cortex had used relatively simple tasks and focused on control areas that produce motor output since they are easier to compare to behavior. However, it is becoming more evident that complex object representations can guide motor systems which do not represent that complexity (see ( Kehoe et al, 2021 ) as an example from the oculomotor system). This notion supports the existence of cognitive programs in temporal cortex which are necessary to work in conjunction with oculomotor priority maps in frontal and parietal cortices to produce complex behaviors.…”

Oculomotor feature discrimination is cortically mediated

“…(C) The results across iterations of the SDOA paradigm. Saccade curvature (vector biasing) is plotted as a function of distractor processing time for all examined distractor features: static-gratings (blue), motion-gratings (red) ( Kehoe et al, 2023 ); luminance-modulated Gabors (green), color-modulated Gabors (magenta) ( Kehoe and Fallah, 2017 ); and complex pseudo-alphanumeric characters during discrimination (yellow) ( Kehoe et al, 2021 ). We highlight notable effects with text-labeled arrows: (1) for simple gratings, vector biasing onsets after just 25 ms of distractor processing time; (2) features begin to differentiate after approximately 50 ms of distractor processing time; (3) the maximum vector biasing occurs after approximately 100 ms of distractor processing time; and (4) discriminated complex objects elicit vector biasing very late, after approximately 110 ms.…”

“…In our paradigm ( Kehoe and Fallah, 2017 ; Kehoe et al, 2021 , 2023 ), human participants plan and execute a saccade to a target, and at some randomized interval after the onset of the target, we onset a peripheral distractor (see Figure 3A ). Critically, we constrain the randomized interval between target and distractor onset so to maximize the likelihood that the distractor onsets prior to the saccade.…”

“…The most compelling evidence of bottlenecked visual projections into the oculomotor system was when we examined the oculomotor encoding time course of complex, novel objects during a discrimination task ( Kehoe et al, 2021 ). On this task, participants were shown a target preview and told to discriminate this target from a distractor with a saccade to indicate their choice.…”

Identifying a Distractor Produces Object-Based Inhibition in an Allocentric Reference Frame for Saccade Planning

“…Both trajectory deviations and IOR can occur under the same conditions but do so on different timescales [21] . The complex objects used by Giuricich, and colleagues [10] required late-stage visual processing to discriminate target from distractor [22][23] . These late-stage ventral stream areas (e.g.…”