Biology subjects

Bucklaew, A.

Publications and source records attributed to Bucklaew, A..

5 recordsLinked to original sources

bioRxiv2026

Neural subpopulations in marmoset area MT/MTC detect and discount saccade-related retinal motion

Primates rely on eye movements made 2-3 times every second to scan their visual environment. Each eye movement induces substantial retinal motion, yet observers readily suppress it to stitch together the percept of a stable world. Neurons in the middle temporal (MT) and medial superior temporal (MST) areas respond to motion, but also suppress that response during eye movements (Bremmer et al., 2009; Leopold & Logothetis, 1998; Thiele et al., 2002). This saccadic suppression could reflect the influence of corollary feedback from eye movement related brain structures (Berman et al., 2017). However, visual signals that detect wide-field motion characteristic of a saccade could also contribute to suppression, akin to visual masking (Idrees et al., 2020). We sought to disentangle the relative contributions of visual signals and corollary discharge in driving saccadic suppression in areas MT and MTC in marmoset monkeys. Marmosets freely viewed natural images, blank backgrounds, or externally moving images that simulated saccades, and also made saccades in complete darkness. We found a diversity of saccadic modulation across the population. Some neurons showed short latency excitatory responses to saccades while others showed suppression. Still others showed a bi-phasic response that began with suppression followed by an excitatory rebound. Neurons with early responses were frequently tuned for the direction of saccades on natural images and retained that same tuning for saccades on blank screens or in complete darkness, thus supporting a role for corollary feedback. However, these neurons also responded with similar directional tuning for retinal motion created by simulating saccades while the eyes were fixed, and thus also appear to integrate visual cues for saccadic motion. More so, these units were biased towards having narrow spike waveforms consistent with putative inhibitory cells, which drive suppression observed in the rest of the population. We also found a subset of neurons that responded robustly to simulated saccadic motion but had negligible response to motion from real saccades, such that they discounted saccade induced motion. Those neurons were biased to have broader spike waveforms, consistent with being putative excitatory projection neurons and could support our percept of stability during eye movements.

neuroscience↗

bioRxiv2025

Probing the limited oculomotor range of common marmosets (Callithrix jacchus)

The ability to scan visual scenes to gather information is a critical adaptive skill across primates. The common marmoset, a small-bodied New World monkey and emerging model of social and visual neuroscience, relies heavily on rapid head movements in addition to eye movements to orient (Pandey et al., 2020; Singh et al., 2025). Previous studies have found a relatively restricted oculomotor range extending out about 10 visual degrees from the central position of rest (Mitchell et al., 2014; Singh et al., 2025). However, previous studies have either used empty arenas for exploration (Singh et al., 2025), or in head-fixed animals used exploration of images potentially biased centrally with posed stimuli (Mitchell et al., 2014). This leaves open questions about whether this restricted oculomotor range is due to physical constraints or a lack of attention-drawing stimuli in the periphery. Understanding marmosets oculomotor range is important for applying modern methods that use marker-less pose tracking of the head as a proxy for gaze direction, under the assumption eye gaze is relatively restricted and can be ignored (Meisner et al., 2025). Using high-precision eye tracking and free-viewing of a natural image and video with objects of interest placed in the periphery, we quantified the oculomotor range of head-fixed marmosets. Our results show limited changes in the range reported from previous studies, even with naturalistic stimuli including moving animals that were optimized to encourage peripheral viewing.

animal behavior and cognition↗

bioRxiv2025

Projection-Specific Intersectional Optogenetics for Precise Excitation and Inhibition in the Marmoset Brain

The primate cerebral cortex relies on long-range connections to integrate information across spatially distributed and functionally specialized areas, yet tools for selectively modulating these pathways remain limited. Here, we present an optimized intersectional viral and optogenetic strategy for precisely exciting and inhibiting projection-specific neurons in the common marmoset. Building on a mouse-to-marmoset pipeline, we first validated that optogenetic activation of inhibitory neurons (via AAV9-Dlx-ChR2) enables robust local cortical inhibition. We then combined retrograde delivery of Cre-recombinase (AAVretro-Cre) with locally injected Cre-dependent vectors encoding excitatory or inhibitory opsins (AAV8-FLEx-ChR2 or Jaws) to achieve directionally selective expression in callosal and frontoparietal pathways. Dual-opsin co-expression enabled precise stimulation or suppression of projection neurons in vivo with minimal off-target labeling. These results establish a scalable framework for projection-specific optogenetic interrogation of distributed circuits in primates, expanding the experimental toolkit for causal studies of higher-order brain function with enhanced anatomical precision and functional specificity. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=71 SRC="FIGDIR/small/660378v2_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@1b88c22org.highwire.dtl.DTLVardef@f831fdorg.highwire.dtl.DTLVardef@9a1403org.highwire.dtl.DTLVardef@197d351_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2022

Post-saccadic following in the marmoset monkey as a read-out of pre-saccadic attention

Primates move their eyes 2-3 times per second to bring objects of interest to central, high-resolution vision. For moving objects, they use a combination of rapid saccadic eye movements along with smooth following movements to track targets continuously. Each saccadic eye movement produces perceptual enhancements for the target. And for saccades that are made to moving targets, or stationary apertures that contain motion, there is a smooth post-saccadic following response (PFR) of the target motion (Kwon et al, 2019). This PFR occurs involuntarily even when the motion is task irrelevant and could provide an automatic behavioral read-out of the targets motion. However, PFR movements are small, so it is unclear how reliable they would be as a trial-by-trial read-out. Here we examined PFR in marmoset monkeys performing a foraging task that requires almost no training and which has been shown to involve pre-saccadic neural enhancements of motion selective responses in visual area MT (Coop et al., 2024). We found that PFR in marmosets is highly consistent with humans and could be used to read-out the target motion. More so, we found that the motion in non-target apertures also influenced PFR but to a lesser extent than the target. The gain of PFR was distributed equally between target and non-target apertures before the saccade, and then was rapidly enhanced only for the target motion in driving the post-saccadic following. Thus, PFR provides a behavioral measure of target enhancement relative to distracters in addition to providing a read-out of the targets motion. Significance StatementUsing a saccade foraging paradigm in marmoset monkeys we measured visual motion integration and pre-saccadic enhancement based on the smooth following eye movements made after a saccade to a motion aperture. We find that marmosets exhibit post-saccadic following behaviors akin to humans, underscoring the evolutionary continuity in visual processing across primates. This following response provided an estimate of target motion that was half as accurate as explicitly trained reports but required minimal training to achieve. It also provided an estimate of the pre-saccadic enhancement for the target relative to distracters in the visual field.

neuroscience↗

bioRxiv2020

The effects of exposure to predators on personality and plasticity

Past experiences are known to affect average behavior but effects on "animal personality", and plasticity are less well studied. To determine whether experience with predators influences these aspects, we compared the behavior of Gryllodes sigillatus before and after exposure to live predators. We found that emergence from shelter and distance moved during open-field trials (activity) changed after exposure, with individuals becoming less likely to emerge from shelters but more active when deprived of shelter. We also found that plasticity in activity increased after exposure to predators and some indications that differences among individuals (i.e. "personality") in emergence from shelter and the amount of an arena investigated increased after exposure. Our results demonstrate that experience with predators affects not only the average behavior of individuals but also how individuals differ from each other--and their own prior behavior--even when all individuals have the same experiences.

animal behavior and cognition↗