Biology subjects

Johansson, R.

Publications and source records attributed to Johansson, R..

3 recordsLinked to original sources

bioRxiv2025

Neural dynamics of relational memory retrieval across eye movements

Relational memory retrieval entails a dynamic interplay between eye movements and neural activity, yet the temporal coordination of these processes remains unclear. This study examines the relationship between theta and alpha EEG activity and sequential fixations during relational memory retrieval. Participants completed a two-alternative forced-choice associative memory task while their eye movements and EEG were recorded simultaneously. Results reveal a relational eye-movement effect: correctly remembered target elements were disproportionately fixated during later stages of the retrieval sequence. Time-frequency EEG analyses across the test trial show that successful retrieval was characterized by an early, transient increase in theta power and a sustained decrease in alpha power. Gaze-related analyses linked these effects to distinct retrieval processes. The theta effect emerged after the initial cue fixation and predicted retrieval success independently of whether subsequent saccades were directed to the target or distractor. In contrast, the alpha decrease predicted retrieval success only across continued target fixations. These findings connect the relational eye-movement effect to two distinct neural signatures: a nonspecific theta increase, reflecting recollection that may initiate pattern completion, and a target-selective alpha decrease, reflecting sustained reactivation of goal-relevant associations across fixations. Together, these results clarify the temporal dynamics of relational memory retrieval and underscore the role of sequential eye movements in memory-guided behavior.

neuroscience↗

bioRxiv2024

Reduction of Neuroinflammation and Seizures in a Mouse Model of CLN1 Batten Disease using the Small Molecule Enzyme Mimetic, N-Tert-Butyl Hydroxylamine.

Infantile neuronal ceroid lipofuscinosis (CLN1 Batten Disease) is a devastating pediatric lysosomal storage disease caused by pathogenic variants in the CLN1 gene, which encodes the depalmitoylation enzyme, palmitoyl-protein thioesterase 1 (PPT1). CLN1 patients present with visual deterioration, psychomotor dysfunction, and recurrent seizures until neurodegeneration results in death, typically before fifteen years of age. Histopathological features of CLN1 include aggregation of lysosomal autofluorescent storage material (AFSM), as well as profound gliosis. The current management of CLN1 is relegated to palliative care. Here, we examine the therapeutic potential of a small molecule PPT1 mimetic, N-tert-butyl hydroxylamine (NtBuHA), in a Cln1-/- mouse model. Treatment with NtBuHA reduced AFSM accumulation both in vitro and in vivo. Importantly, NtBuHA treatment in Cln1-/- mice reduced neuroinflammation, mitigated epileptic episodes, and normalized motor function. Live cell imaging of Cln1-/- primary cortical neurons treated with NtBuHA partially rescued aberrant synaptic calcium dynamics, suggesting a potential mechanism contributing to the therapeutic effects of NtBuHA in vivo. Taken together, our findings provide supporting evidence for NtBuHA as a potential treatment for CLN1 Batten Disease.

neuroscience↗

bioRxiv2022

Episodic memory formation in naturalistic viewing

The brain systems of episodic memory and oculomotor control are tightly linked, suggesting a crucial role of eye movements in memory. But little is known about the neural mechanisms of memory formation across eye movements in unrestricted viewing behavior. Here, we leverage simultaneous eye tracking and EEG recording to examine episodic memory formation in free viewing. Participants memorized multi-element events while their EEG and eye movements were concurrently recorded. Each event comprised elements from three categories (face, object, place), with two exemplars from each category, in different locations on the screen. A subsequent associative memory test assessed participants memory for the between-category associations that specified each event. We used a deconvolution approach to overcome the problem of overlapping EEG responses to sequential saccades in free viewing. Brain activity was time-locked to the fixation onsets, and we examined EEG power in the theta and alpha frequency bands, the putative oscillatory correlates of episodic encoding mechanisms. Three modulations of fixation-related EEG predicted high subsequent memory performance: 1) theta increase at fixations after between-category gaze transitions, 2) theta and alpha increase at fixations after within-element gaze transitions, 3) alpha decrease at fixations after between-exemplar gaze transitions. Thus, event encoding with unrestricted viewing behavior was characterized by three neural mechanisms, manifested in fixation-locked theta and alpha EEG activity that rapidly turned on and off during the unfolding eye movement sequences. These three distinct neural mechanisms may be the essential building blocks that subserve the buildup of coherent episodic memories during unrestricted viewing behavior.

neuroscience↗