Biology subjects

Bogler, C.

Publications and source records attributed to Bogler, C..

4 recordsLinked to original sources

bioRxiv2025

Visual working memory representations of naturalistic images in early visual cortex are not sensory-like

For a long time, working memory was considered to reflect sustained activity in prefrontal and parietal areas. This has been challenged by the "sensory recruitment model" according to which sensory areas are involved in maintaining working memory representations. The main support for this comes from the finding that working memory contents can be decoded from early sensory areas during memory delay periods. However, the availability of stimulus-related information in sensory regions does not reveal whether this information is encoded in a sensory format, i.e. in the same way as sensory stimuli. Alternatively, working memory contents could be encoded in independent formats or even potentially undergo dynamic changes throughout the delay. Here, we test this question directly by requiring participants to briefly memorise naturalistic object-scenes. We directly compared the way early visual regions encoded the contents during perception and working memory maintenance. As in previous studies, we found robust stimulus-related information in early visual cortex throughout the delay. However, despite continuously robust information, the encoding of memory contents in the later delay period did not occur in the same format as during pure perception. Thus, despite the fact that sensory areas have working-memory-related information, the format of this information is not strictly sensory-like throughout the delay.

neuroscience↗

bioRxiv2024

Neural Correlates of Different Randomization Tasks

In some cases, when we are making decisions, the available choices can appear to be equivalent. When this happens, our choices appear not to be constrained by external factors and instead we can believe to be selecting "randomly". Furthermore, randomness is sometimes even explicitly required by task conditions such as in random sequence generation (RSG) tasks. This is a challenging task that involves the coordination of multiple cognitive processes, which can include the inhibition of habitual choice patterns and monitoring of the running choice sequence. It has been shown that random choices are strongly influenced by the way they are instructed. This raises the question whether the brain mechanisms underlying random selection also differ between different task instructions. To assess this, we measured brain activity while participants were engaging in three different variations of a sequence generation task: Based on previous work, participants were instructed to either (1) "generate a random sequence of choices", (2) "simulate a fair coin toss", or (3) "choose freely". Our results reveal a consistent frontoparietal activation pattern that is shared across all tasks. Specifically, increased activity was observed in bilateral inferior and right middle frontal gyrus, left pre-supplementary motor area, bilateral inferior parietal lobules and portions of anterior insular cortex in both hemispheres. Activity in the mental coin toss condition was higher in right dorsolateral prefrontal cortex, left (pre-) supplementary motor area, a portion of right inferior frontal gyrus, bilateral superior parietal lobules and bilateral anterior insula. Additionally, our multivariate analysis revealed a distinct region in the right frontal pole to be predictive of the outcome of choices, but only when randomness was explicitly instructed. These results emphasize that different randomization tasks involve both shared and unique neural mechanisms. Thus, even seemingly similar randomization behavior can be produced by different neural pathways.

neuroscience↗

bioRxiv2023

Encoding of continuous perceptual choices in human early visual cortex

Research on the neural mechanisms of perceptual decision-making has typically focused on simple categorical choices, say between two alternative motion directions. Studies on such discrete alternatives have often suggested that choices are encoded either in a motor-based or in an abstract, categorical format in regions beyond sensory cortex. However, many sensory features are graded rather than discrete, raising the question how choices are encoded when they span the full sensory continuum. Here we assessed this using motion stimuli that could vary anywhere between 0{degrees} and 360{degrees}. We employed a combination of neuroimaging and encoding models based on Gaussian Process Regression to assess how either stimuli or choices were encoded in brain responses. We found that single-voxel tuning patterns could be used to reconstruct the trial-by-trial physical direction of motion as well as the participants continuous choices. Importantly, these continuous choice signals were primarily observed in early visual areas. The tuning properties in this region generalized between choice encoding and stimulus encoding, even for reports that reflected pure guessing. We found only little information related to the decision outcome in regions beyond visual cortex, such as parietal cortex, possibly because our task did not involve differential motor preparation. This could suggest that decisions for continuous stimuli take can place already in sensory brain regions, potentially using similar mechanisms to the sensory recruitment in visual working memory.

neuroscience↗

bioRxiv2021

Confusions regarding stochastic fluctuations and accumulators in spontaneous movements

Experiments on choice-predictive brain signals have played an important role in the debate on free will. In a seminal study, Benjamin Libet and colleagues found that a negative-going EEG signal, the readiness potential (RP), can be observed over motor-related brain regions hundreds of ms before the retrospectively reported time of the conscious decision to move. If the onset of the readiness potential is taken as an indicator of the "brains decision to move" this could mean that this decision to move is made early, by unconscious brain activity, rather than later, at the time when the subject believes to have decided. However, an alternative kind of interpretation, involving ongoing stochastic fluctuations, has recently been brought to light. One such model, the stochastic decision model (SDM), takes its inspiration from accumulator models of perceptual decision making. It suggests that the RP originates from an accumulation of ongoing stochastic fluctuations. In this view the decision happens only at a much later stage when an accumulated noisy signal (plus imperative) reaches a threshold. Here we clarify a number of confusions regarding both the evidence for the stochastic decision model as well as the interpretation that it offers. We will explore several points that we feel are in need of clarification: (a) that the empirical evidence for the role of stochastic fluctuations is so far only indirect; (b) that the relevance of evidence from animal studies is unclear; (c) that a model that is deterministic during the accumulation stage can explain the data in a similar way; (d) that the primary focus in the literature has been on the role of random fluctuations whereas the deterministic aspects of the model have been largely ignored; (e) that contrary to the original interpretation the deterministic component of the model is the dominant input into the accumulator; (f) that there is confusion regarding the role of "imperative" and "evidence" in the SDM and its link to perceptual decision making; and finally (g) as with other stochastic accumulator processes the question of whether the decision happens early or late depends on the nature of the noise fluctuations, specifically, whether they reflect "absolute" or "epistemic" randomness. Our aim is not to rehabilitate the role of the RP in the free will debate. Rather we aim to address some confusions regarding the evidence for accumulators playing a role in these preparatory brain processes.

neuroscience↗