Landmark-Centered Coding in Frontal Cortex Visual Responses

Abstract

Visual landmarks influence spatial cognition, navigation and goal-directed behavior, but their influence on visual coding for action is poorly understood. Here, we tested landmark influence on prefrontal visual responses by recording from 568 neurons in the frontal (FEF) and supplementary (SEF) eye fields of rhesus macaques. The response field (the area of visual space that modulates activity) for each neuron was tested in the presence of a landmark placed at one of four configurations. We then fit the spatially tuned response fields against a spatial coordinate continuum between gaze-and landmark-centered models. When response fields were fit separately for each target-landmark configuration, the best fits shifted (mean 37% / 40%) toward landmark-centered coding in FEF / SEF respectively, confirming a configuration-dependent intermediate coding scheme. Overall, these data show that external landmarks influence prefrontal visual responses, possibly helping to stabilize movement goals in the presence of noisy internal egocentric signals.

Gaze-Related Activity in Primate Frontal Cortex Predicts and Mitigates Spatial Uncertainty

“…7 ) and the general principle of reward/effort maximization 57,58 , we propose the following explanation for our neurophysiological data. Our previous results suggest that the FEF and SEF continue to show an eye-centered target-relative-to-eye to gaze-relative-to-eye transformation for saccades in the presence of a landmark 15,16 , but their visual signals are influenced by landmarks in a fashion that depends on target-landmark configuration 32 . Thus target-landmark configuration information is present from the start of each trial, but our new data here suggest that these interactions are influenced over time by the expectation of future probabilistic events and reward 16,61 .…”

“…Various previous studies have addressed the use of landmarks in the retrospective coding of target memory for action planning 32–35 , and other studies have considered the prospective use of cues for predictive gaze coding 2,36,37 , but here have we considered the combination of these two factors for spatial behavior involving probabilistic environmental cues. In our task, an environmental cue that would normally augment visual stability 38,39 becomes unstable.…”

Multiunit frontal eye field activity codes the visuomotor transformation, but not gaze prediction or target memory, in a delayed saccade task

“…In the case of the motor responses, all models were significantly eliminated except for gaze displacement (dG, which is very similar to Ge in this dataset). This does not mean that these populations do not code for other variables in individual cells or in more subtle ways (Schütz et al, 2023) but shows that Te and Ge provide the best overall measures of their explicit population coding scheme. These results confirm the previous SU analysis and tend to suggest that MU populations show similar results.…”

“…We first repeated the model-fitting analysis of the previous study (Bharmauria et al, 2020) on SU and MU activity populations to confirm if Te and Ge were the overall best ‘canonical’ models to represent response field activity in this task. [Note that in the recent investigation (Schütz et al, 2023) these models were called T F(e) / G F(e) to specify the Foveal coordinate origin (0,0), but this can be assumed here]. Again, these are not theoretical models, but rather models that were derived from the experimental measures described above.…”

“…1A). Although background stimuli produced various modulations (Schütz et al, 2023), the data still showed a strong T-G transformation (Bharmauria et al, 2021, 2020). Therefore, we deemed this might provide an ideal dataset to test the relative robustness of sensorimotor codes derived from SU versus MU activity.…”