Biology subjects

Poppenk, J.

Publications and source records attributed to Poppenk, J..

5 recordsLinked to original sources

bioRxiv2020

Variation in error-based and reward-based human motor learning is related and associated with entorhinal volume

Error-based and reward-based processes are critical for motor learning, and are thought to be mediated via distinct neural pathways. However, recent behavioral work in humans suggests that both learning processes are supported by cognitive strategies and that these contribute to individual differences in motor learning ability. While it has been speculated that medial temporal lobe regions may support this strategic component to learning, direct evidence is lacking. Here we first show that faster and more complete learning during error-based visuomotor adaptation is associated with better learning during reward-based shaping of reaching movements. This result suggests that strategic processes, linked to faster and better learning, drive individual differences in both error-based and reward-based motor learning. We then show that right entorhinal cortex volume was larger in good learning individuals--classified across both motor learning tasks--compared to their poorer learning counterparts. This suggests that strategic processes underlying both error- and reward-based learning are linked to neuroanatomical differences in entorhinal cortex. Significance StatementWhile it is widely appreciated that humans vary greatly in their motor learning abilities, little is known about the processes and neuroanatomical bases that underlie these differences. Here, using a data-driven approach, we show that individual variability in error-based and reward-based motor learning is tightly linked, and related to the use of cognitive strategies. We further show that structural differences in entorhinal cortex predict this intersubject variability in motor learning, with larger entorhinal volumes being associated with better overall error-based and reward-based learning. Together, these findings provide support for the notion that the ability to recruit strategic processes underlies intersubject variability in both error-based and reward-based learning, which itself may be linked to structural differences in medial temporal regions.

neuroscience↗

bioRxiv2020

Structural variation in hippocampal dentations among healthy young adults

Little is known about hippocampus dentations - or "bumps" on the inferior surface of the hippocampus - and whether they hold functional significance. Empirical work on these features is beginning to emerge, but no study has yet been conducted in which their spatial positions are demarcated, and their putative role in individual differences in memory is based on a single small study. We gathered ultra-high resolution isotropic MTL scans from young-adult sample and performed such measurements. On the long axis, we found smaller and denser dentations moving towards the hippocampus posterior extent. Although other reports have distinguished the functional characteristics of anterior and posterior hippocampal dentations, we found hardly any were actually localized in the hippocampal head, with half of participants featuring no anterior dentations at all. We also observed more numerous dentations in the left hemisphere than right, and found this asymmetry tracked right-hand dominance. All dentations lay specifically within in the CA1 subfield, which was thicker at dentations - protruding below standard lower boundary of the hippocampus - as well as larger in participants with more dentations, suggesting dentations reflect CA1 growth rather than mere folding. Finally, we observed an association between dentations and visual source memory, but not recognition memory. The current report is the first to characterize the spatial properties of this intriguing neuroanatomical feature, which requires the direct spatial labeling of dentations. Further to better characterizing this intriguing neuroanatomical feature, we provide some confirmatory evidence for a link to episodic memory, although we found evidence for this link to be less overwhelming than initially reported.

neuroscience↗

bioRxiv2019

Sleep promotes relational overlapping memories for long-term generalization

Human memory for recent events is believed to undergo reactivation during sleep. This process is thought to be relevant for the consolidation of both individual episodic memories and gist extraction, the formation of generalized memory representations from multiple, related memories. Which kinds of gist are actually enhanced, however, is the subject of less consensus. To address this question, we focused our design on four types of gist: inferential gist (relations extracted across non-contiguous events), statistical learning (regularities extracted from a series), summary gist (a theme abstracted from a temporally contiguous series of items), and category gist (characterization of a stimulus at a higher level in the semantic hierarchy). Sixty-nine participants (30 men, 38 women, and 1 other) completed memory encoding tasks addressing these types of gist and corresponding retrieval tasks the same evening, the morning after, and one week later. Inferential gist was retained over a week, whereas memory for category gist, summary gist, and statistical learning decayed. Higher proportions of REM were associated with worse performance in a statistical learning task controlling for time. Our results support that REM sleep is involved in schema disintegration, which works against participants ability to identify regularities within temporal series.\n\nSIGNIFICANCE STATEMENTTo gain the most from our experiences, we extract from them the most important elements, or \"gist\", with sleep believed to facilitate this process. However, what is referred to as gist varies considerably across studies. We report categorically different mnemonic trajectories of two classes of gist. In particular, we show that gist involving synthesis across relational memories is retained over time, whereas other gists were subject to substantial decay. Moreover, our evidence supports the idea that REM works to discretize, rather than synthesize experiences. Future research should test similar constructs in different tasks to determine whether these findings are generalizable. Our research suggests that patients with reduced REM sleep may experience more interference between similar memories.

neuroscience↗

bioRxiv2019

Brain meta-state transitions demarcate spontaneous thoughts in movie-viewing and resting cognition

Using new methods to capture streams of neural meta-state transitions in single participants, we characterize the psychological meaning of these regular neural events. Similar to past group-average-based analyses, participants individual transition streams aligned to meaningful events during movie-viewing. However, our individual-based approach also afforded observation of participants idiosyncratic transition timing at rest. Across these two dramatically different task contexts, transitions featured similar trait-like frequency, concurrence with activation of regions associated with spontaneous thought, and suppression by attention regions. Based on this generalization, as well as the centrality of semantics to thought, we argue transitions serve as a general, implicit neurobiological marker of new thoughts, and that their frequency therefore approximates participants mentation rate. Finally, to contribute convergent validity and illustrate the utility of our approach for thought dynamics, we regressed resting transition rate and movie-viewing group temporal conformity against trait neuroticism, yielding a first neural confirmation of the \"mental noise\" theory.

neuroscience↗

bioRxiv2017

Parametrically scalable memory reactivation using multiple object tracking

Converging evidence supports the \"non-monotonic plasticity\" hypothesis that although complete retrieval may strengthen memories, partial retrieval weakens them. Yet, the classic experimental paradigms used to study effects of partial retrieval are not ideally suited to doing so, because they lack the parametric control needed to ensure that the memory is activated to the appropriate degree (i.e., that there is some retrieval, but not enough to cause memory strengthening). Here we present a novel procedure designed to accommodate this need. After participants learned a list of word-scene associates, they completed a cued mental visualization task that was combined with a multiple-object tracking (MOT) procedure, which we selected for its ability to interfere with mental visualization in a parametrically adjustable way (by varying the number of MOT targets). We also used fMRI data to successfully train an \"associative recall\" classifier for use in this task: this classifier revealed greater memory reactivation during trials in which associative memories were cued while participants tracked one, rather than five MOT targets. However, the classifier was insensitive to task difficulty when recall was not taking place, suggesting it had indeed tracked memory reactivation rather than task difficulty per se. Consistent with the classifier findings, participants' introspective ratings of visualization vividness were modulated by task difficulty. In addition, classifier output and slowing of responses in a post-reactivation memory test suggested that partial reactivation, induced by MOT, weakened memory. We argue that this procedure has desirable properties for future investigation of partial retrieval effects, e.g., in closed-loop experiments.

neuroscience↗