Research

Publications

Najenson, J. (Forthcoming). Encoding without perceiving: Can memories be implanted?. Philosophical Psychology.

The origin of memories is thought to be found in sensory perception. This conception is central to how the memory sciences characterize encoding. This paper considers how novel memory traces can be formed independently of external sensory inputs. I present a case study in which memory traces are created without sensory perception using a technique I call optogenetic memory implantation. Comparing this artificial process with normal memory encoding, I consider its implications for rethinking the causal chain that leads to remembering.

Colaço, D. & Najenson, J. (2023). Where memory resides: Is there a rivalry between molecular and synaptic models of memory?. Philosophy of Science.1-11.

Recent proposals that the substrate of memory is molecular raise questions about where this molecular model stands in relation to the dominant synaptic model of memory. In this article, we address the perceived rivalry between these models and ask whether they can be integrated. We argue that addressing rivalry or integration requires delineating the explananda of synaptic and molecular models, as well as revisiting assumptions about how these models account for their explananda. The perceived rivalry between these models exemplifies epistemic costs that arise when we try to pit explanatory models as rivals or integrate them.

Najenson, J. (2023). LTP revisited: Reconsidering the explanatory power of synaptic efficacy. Review of Philosophy and Psychology. 1-26.

Changes in synaptic strength are described as a unifying hypothesis for memory formation and storage, leading philosophers to consider the ‘synaptic efficacy hypothesis’ as a paradigmatic explanation in neuroscience. Craver’s mosaic view has been influential in understanding synaptic efficacy by presenting long-term potentiation as a multi-level mechanism nested within a multi-level structure. This paper argues that the mosaic view fails to fully capture the explanatory power of the synaptic efficacy hypothesis due to assumptions about multi-level mechanisms. I present an alternative approach that emphasizes the explanatory function of unification, accounting for the widespread consensus in neuroscience regarding synaptic efficacy by highlighting the stability of synaptic causal variables across different multi-level mechanisms.

Najenson, J. (2021). What have we learned about the engram?. Synthese, 199, 9581–9601.

The discovery of the engram, the physical substrate of memory, is a central challenge for the sciences of memory. Following the application of optogenetics to the neurobiological study of memory, scientists and philosophers claim that the engram has been found. In this paper, I evaluate the implications of applying optogenetic tools to the localization of the engram. I argue that conceptions of engram localization need to be revised to be made consistent with optogenetic studies of the engram. I distinguish between challenges to vehicle and content localization. First, I consider the silent engram hypothesis. According to this hypothesis, optogenetic studies indicate that synaptic efficacy, the traditional engram-bearing vehicle, is important merely for retrieval. I argue that this interpretation rests upon a misunderstanding of accessibility. Second, I argue that optogenetic-based strategies and findings conflict with preservationist and constructivist views on memory storage. There is an enduring trace, but stored content may change over time and experience, resulting in doubt about what constitutes a single engram. 

Najenson, J. & Fresco, N. (2021). The role of information in knowledge-how. Frontiers in Psychology, 12, 4050.

Knowledge-how is the kind of knowledge implicated in skill employment and acquisition. Intellectualists claim that knowledge-how is a special type of propositional knowledge. Anti-intellectualists claim that knowledge-how is not propositional. We argue that both views face two open challenges. The first challenge pertains to the relationship between informational states and motor variability. The second pertains to the epistemic function of practice that leads to skill (and knowledge-how). The aim of this paper is to suggest a general conceptual framework based on functional information with both intellectualist and anti-intellectualist features. Our proposal, we argue, avoids the above challenges, and can further the debate on knowledge-how and skill. 

Najenson, J. (Forthcoming). Memory systems and the mnemic character of procedural memory. British Journal for the Philosophy of Science.

According to a standard view in psychology and neuroscience, there are multiple memory systems in the brain. Philosophers and scientists of memory rely on the idea that there are multiple memory systems in the brain to infer that procedural memory is not a cognitive form of memory. As a result, memory is considered to be a disunified capacity. In this paper, I evaluate two criteria used by Michaelian to demarcate between cognitive and non-cognitive memory systems: appeal to stored content and retrieval flexibility. By considering several empirical cases I argue that the criteria offered ultimately fail to distinguish between memory systems. The procedural memory system is neither contentless nor inflexible.

Work in Progress (Drafts are available upon request)

Practice Makes Better? The Influence of Increased Practice on Task Conflict in the Stroop Task (With Rut Zaks-Ohayon, Joseph Tzelgov and Nir Fresco)

The Stroop task is widely used to study attentional control and cognitive flexibility. However, questions about its sensitivity to training and the impact of task conflict on attentional control remain open. Here, we investigated the effects of practice and task conflict on attentional control in the Stroop task, with participants completing four sessions of a Stroop task over three weeks in low and high task-conflict conditions. Our results show that the level of task conflict had an impact only in the first session, and no effect in subsequent sessions. Moreover, we found that practice reduced response times in the Stroop task, even in trials with incongruent stimuli. Nevertheless, the interference between congruent and incongruent stimuli remained consistent throughout the training sessions over the three-week period, indicating that interference is not affected by training. Our study, therefore, suggests that the level of task conflict does not improve Stroop task performance with training. These findings provide insights into the role of task conflict and practice in attentional control and cognitive flexibility.

Hierarchies and Analogies in Neurobiology

Abstract under construction.

The Causal Specificity of Memory Traces

Abstract under construction.