Biology subjects

Lee, T. G.

Publications and source records attributed to Lee, T. G..

6 recordsLinked to original sources

bioRxiv2024

Errors of attention adaptively warp spatial memory

Adaptation is the process by which we adjust internal models of the body, world, and mind in response to sensory feedback. While adaptation is studied extensively in the context of motor control, there is limited evidence that cognitive functions such as working memory are subject to the same error-driven adaptive control mechanism. To examine the possibility that internal spatial representations undergo adaptation, we had participants perform a task that interleaved a perceptual discrimination task and a spatial working memory task. Perceptual discrimination trials (85% of trials) presented an initial peripheral cue to exogenously capture attention, immediately followed by a displaced target stimulus. This sequence of events served to repeatedly induce a covert attentional allocation error. Interleaved spatial working memory trials (15% of trials) presented a stimulus at a pseudorandom peripheral location followed by a delay interval. On half of the working memory trials, the stimulus was surreptitiously presented at the same location as the initial attentional cue. We found that as attentional errors accumulated over the course of the experiment, participants spatial recall shifted to counteract the attentional error. The magnitude of this shift was proportional to the number of induced errors. Recall performance rapidly recovered following the offset of error trials. Multiple control experiments ruled out alternative explanations for these results, such as oculomotor confounds and attentional biases unrelated to error. These findings indicate that the computational mechanisms governing the adaptation of motor commands appear to similarly serve to adjust and calibrate spatial cognition.

neuroscience↗

bioRxiv2023

Dissociable causal roles of dorsolateral prefrontal cortex and primary motor cortex as a function of motor skill expertise

Established models of motor skill learning posit that early stages of learning are dominated by an attentionally demanding, effortful mode of control supported by associative corticostriatal circuits involving the dorsolateral prefrontal cortex (DLPFC). As expertise develops, automatic and "effortless" performance coincides with a transition to a reliance on sensorimotor circuits that include primary motor cortex (M1). However, the dynamics of how control evolves during the transition from novice to expert are currently unclear. This lack of clarity is due, in part, to the fact that most motor learning studies comprise a limited number of training sessions and rely on correlative techniques such as neuroimaging. Here, we train human participants on a discrete motor sequencing task over the course of six weeks, followed by an assessment of the causal roles of DLPFC and M1 at varying levels of expertise. We use repetitive transcranial magnetic stimulation to transiently disrupt activity in these regions immediately prior to performance in separate sessions. Our results confirm the dissociable importance of DLPFC and M1 as expertise develops. DLPFC stimulation leads to larger behavioral deficits for novice skills than expert skills, while M1 stimulation leads to relatively larger deficits as expertise develops. However, our results also reveal that prefrontal disruption causes performance deficits at all levels of expertise. These findings challenge existing models and indicate an evolving rather than a strictly diminishing role for DLPFC throughout learning. Significance StatementMotor skills involve the sequential chaining of individual actions. For example, playing the piano involves learning to rapidly transition to from one finger press to another. Human neuroimaging studies have shown that primary motor cortex (M1) and dorsolateral prefrontal cortex (DLPFC) support novice motor sequencing skills, but activity in both regions declines over training. This has been interpreted as increased efficiency in M1 and yet a reduction in the involvement of DLPFC as expertise develops. We causally test this assumption by using non-invasive brain stimulation to transiently disrupt cortical activity following extended skill training. Although we confirm dissociable contributions of DLPFC and M1 as expertise develops, we show that both regions are necessary for performance regardless of skill level.

neuroscience↗

bioRxiv2022

What happens after an error?

Humans tend to slow down after making an error. A longstanding account of this post-error slowing is that people are simply more cautious. However, accuracy typically does not improve following an error leading some researchers to suggest that an initial orienting response may initially impair performance immediately following error. Unfortunately, characterizing the nature of this error-based impairment remains a challenge in standard tasks that use free response times. Using a new experimental approach, we exert tight control over the timing of responses to reveal the time course of stimulus-response processing. Participants are less accurate after an error even when given ample time to make a response. A computational model of response preparation rules out the possibility that errors lead to slower cognitive processing. Instead, we find that the "efficacy" of cognitive processing in producing an intended response is impaired following errors. Participants commit more perseverative slips of action following an error. Rather than a strategic shift along a single speed-accuracy tradeoff function, post-error slowing observed in free response time tasks may be an adaptive response to impaired cognitive processing that reflects a fundamentally altered relationship between the speed and accuracy of responses.

neuroscience↗

bioRxiv2021

Reward influences the allocation but not the availability of resources in visual working memory

Visual working memory possesses strict capacity constraints which place limits on the availability of resources for encoding and maintaining information. Studies have shown that prospective rewards improve performance on visual working memory tasks, but it remains unclear whether rewards increase total resource availability or rather influence the allocation of resources without affecting availability. Participants performed a continuous report visual working memory task with oriented grating stimuli. On each trial, participants were presented with a priority cue, which signaled the item most likely to be probed, and a reward cue, which signaled the magnitude of a performance-contingent reward. We showed that rewards decreased recall error for cued items and increased recall error for non-cued items. We further demonstrated that rewards produced a tradeoff in the probability of successfully encoding a cued versus a non-cued item rather than a tradeoff in recall precision or the probability of binding errors. Lastly, we showed that rewards only affected resource allocation when participants were given the opportunity to engage proactive control prior to encoding. These findings indicate that rewards influence the flexible allocation of resources during selection and encoding in visual working memory, but do not augment total capacity.

neuroscience↗

bioRxiv2021

Testing in vitro toxicity of nanoparticles in 3D cell culture with various extracellular matrix scaffold

Nanomaterials are used in a variety of fields and toxicity assessment is paramount for their development and application. Although most toxicity assessments have been performed in 2D (2-Dimensional) cell culture, the inability to adequately replicate the in vivo environment and toxicity is a limitation. To overcome the limitation, a 3D (3-Dimensional) cell culture method has been developed to make an environment closer to an in vivo system. In this study, 20 nm SiO2 nanoparticles were dispersed in serum-containing (SC) and serum-free (SF) media to compare 2D cell culture and 3D cell culture toxicity. The cells were subjected to a 3D cell culture method in which HepG2, a human-derived liver cancer cell line, was mixed on a scaffold. We found that nanoparticles induced toxicity in 2D cell culture, but toxicity was not observed in 3D cell culture similar to in vivo environment. However, differences in toxicity were observed between the three types of scaffolds in the absence of serum as the number of cells decreased.

pharmacology and toxicology↗

bioRxiv2018

Human perception-motor decision-making is not optimal

The rationality of human behavior has been a major problem in philosophy for centuries. The pioneering work of Kahneman and Tversky provides strong evidence that people are not rational. Recent work in psychophysics argues that incentivized sensorimotor decisions (such as deciding where to reach to get a reward) maximizes expected gain, suggesting that it may be impervious to cognitive biases and heuristics. We rigorously tested this hypothesis using multiple experiments and multiple computational models. We obtained strong evidence that people deviated from the objectively rational strategy when potential losses were large. They instead appeared to follow a strategy in which they simplify the decision problem and satisfice rather than optimize. This work is consistent with the framework known as bounded rationality, according to which people behave rationally given their computational limitations.

animal behavior and cognition↗