INS NYC 2024 Program

Poster	Poster Session 06 Program Schedule 02/15/2024 04:00 pm - 05:15 pm Room: Shubert Complex (Posters 1-60) Poster Session 06: Aging \| MCI \| Neurodegenerative Disease - PART 2 Final Abstract #40 Features of Human Hippocampal Sharp-Wave Ripples During Sleep as Biomarkers for Long-Term Memory Processes Elizabeth Espinal, Drexel University, Philadelphia, United States Ana Gherman, Department of Neurosurgery, Hofstra Northwell School of Medicine and Feinstein Institutes for Medical Research, Manhasset, United States Akash Mishra, Department of Neurosurgery, Hofstra Northwell School of Medicine and Feinstein Institutes for Medical Research, manhasset, United States Ashesh Mehta, Department of Neurosurgery, Hofstra Northwell School of Medicine and Feinstein Institutes for Medical Research, Manhasset, United States Evangelia Chrysikou, Drexel University, Philadelphia, United States Stephan Bickel, Department of Neurosurgery, Hofstra Northwell School of Medicine and Feinstein Institutes for Medical Research, Manhasset, United States Category: Memory Functions/Amnesia Keyword 1: hippocampus Keyword 2: neurophysiology Keyword 3: sleep Objective: Damage or degradation to neural memory networks and related brain structures is devastating; episodic memory shapes what we understand to be our lives and 'world.' The hippocampus is a brain structure with a crucial and unique role in episodic memory encoding and recall. Less explored is the role of the hippocampus and hippocampal sharp-wave ripples (SWR) in overnight memory consolidation. The current study aimed to explore the effect on behavior when there are alterations to SWR, defined as differences in SWR features (rate, amplitude, duration), during a naturally occurring brain state, sleep. Participants and Methods: We employed intracranial electroencephalography (iEEG) to directly record hippocampal SWR in 12 patients, 4 with left mesial temporal sclerosis (left-MTS) and 8 with seizure onsets (SOZ) outside of the hippocampus (mixed-SOZ) during sleep. This method allows us to gain a unique temporal and spatial perspective on electrophysiological biomarkers of memory during sleep not easily accessible with other methods. The current study aimed to determine alterations in typical sleep oscillations in patients with and without structural hippocampal damage and correlate them with a neuropsychological measure believed to be sensitive to hippocampal dysfunction (Rey Auditory Verbal Learning Task (RAVLT)). Results: A mixed linear effects model examining the relationship between group, hemisphere and their intercept, and SWR duration and amplitude revealed a significant effect of duration (F(2, 13403) = 880.11, p < .001) and amplitude (F(2, 13403) = 318.13, p < .001). These findings suggest that hippocampal hemisphere and left MTS vs non-left MTS patients have significant differences in the SWR features. We examined the relationship between the RAVLT delayed recall (RAVLT-DR) trial and the correlation coefficient between the left-right hippocampal SWR rates for all participants and found a moderate positive correlation (r(10) = 0.31, r²= 0.09). There was a weak positive relationship between SWR duration and RAVLT-DR scores (r(10) = 0.23, r²= 0.05). Higher t-scores represent longer SWR duration in the left hippocampus. A correlation analysis was conducted to examine the association between SWR amplitude power t-scores and RAVLT-DR scores. There was a negligible correlation between SWR amplitude power t-scores and RAVLT-DR scores (r = -0.227, r²= 0.05). Additionally, there was a weak positive relationship between age of epilepsy onset and RAVLT-DR scores (r(10) = 0.22, r²= 0.047) and a moderate positive relationship between disease duration and RAVLT-DR scores (r(10) = 0.30, r²= 0.091). Conclusions: We demonstrated significant group differences in SWR features between the left-MTS group and mixed-SOZ group for the left hippocampus regardless of SOZ hemisphere. We provide the first evidence to suggest a link between SWR features and memory performance (RAVLT-DR) such that longer SWR duration in the left hippocampus was positively linked with memory performance, as was SWR rate synchronization in the bilateral hippocampi and memory performance. Finally, we highlight a potential link between individual disease features (i.e., disease duration) and performance. Taken together, the results of this study meaningfully contribute to the literature in examining SWR features in humans as biomarkers for long-term memory consolidation and neuroplasticity in reorganizing eloquent cortex.

Poster

02/15/2024
04:00 pm - 05:15 pm
Room: Shubert Complex (Posters 1-60)

Poster Session 06: Aging | MCI | Neurodegenerative Disease - PART 2

Final Abstract #40

Features of Human Hippocampal Sharp-Wave Ripples During Sleep as Biomarkers for Long-Term Memory Processes

Elizabeth Espinal, Drexel University, Philadelphia, United States
Ana Gherman, Department of Neurosurgery, Hofstra Northwell School of Medicine and Feinstein Institutes for Medical Research, Manhasset, United States
Akash Mishra, Department of Neurosurgery, Hofstra Northwell School of Medicine and Feinstein Institutes for Medical Research, manhasset, United States
Ashesh Mehta, Department of Neurosurgery, Hofstra Northwell School of Medicine and Feinstein Institutes for Medical Research, Manhasset, United States
Evangelia Chrysikou, Drexel University, Philadelphia, United States
Stephan Bickel, Department of Neurosurgery, Hofstra Northwell School of Medicine and Feinstein Institutes for Medical Research, Manhasset, United States

Category: Memory Functions/Amnesia

Keyword 1: hippocampus
Keyword 2: neurophysiology
Keyword 3: sleep

Objective:

Damage or degradation to neural memory networks and related brain structures is devastating; episodic memory shapes what we understand to be our lives and 'world.' The hippocampus is a brain structure with a crucial and unique role in episodic memory encoding and recall. Less explored is the role of the hippocampus and hippocampal sharp-wave ripples (SWR) in overnight memory consolidation. The current study aimed to explore the effect on behavior when there are alterations to SWR, defined as differences in SWR features (rate, amplitude, duration), during a naturally occurring brain state, sleep.

Participants and Methods:

We employed intracranial electroencephalography (iEEG) to directly record hippocampal SWR in 12 patients, 4 with left mesial temporal sclerosis (left-MTS) and 8 with seizure onsets (SOZ) outside of the hippocampus (mixed-SOZ) during sleep. This method allows us to gain a unique temporal and spatial perspective on electrophysiological biomarkers of memory during sleep not easily accessible with other methods. The current study aimed to determine alterations in typical sleep oscillations in patients with and without structural hippocampal damage and correlate them with a neuropsychological measure believed to be sensitive to hippocampal dysfunction (Rey Auditory Verbal Learning Task (RAVLT)).

Results:

A mixed linear effects model examining the relationship between group, hemisphere and their intercept, and SWR duration and amplitude revealed a significant effect of duration (F(2, 13403) = 880.11, p < .001) and amplitude (F(2, 13403) = 318.13, p < .001). These findings suggest that hippocampal hemisphere and left MTS vs non-left MTS patients have significant differences in the SWR features. We examined the relationship between the RAVLT delayed recall (RAVLT-DR) trial and the correlation coefficient between the left-right hippocampal SWR rates for all participants and found a moderate positive correlation (r(10) = 0.31, r²= 0.09). There was a weak positive relationship between SWR duration and RAVLT-DR scores (r(10) = 0.23, r²= 0.05). Higher t-scores represent longer SWR duration in the left hippocampus. A correlation analysis was conducted to examine the association between SWR amplitude power t-scores and RAVLT-DR scores. There was a negligible correlation between SWR amplitude power t-scores and RAVLT-DR scores (r = -0.227, r²= 0.05). Additionally, there was a weak positive relationship between age of epilepsy onset and RAVLT-DR scores (r(10) = 0.22, r²= 0.047) and a moderate positive relationship between disease duration and RAVLT-DR scores (r(10) = 0.30, r²= 0.091).

Conclusions:

We demonstrated significant group differences in SWR features between the left-MTS group and mixed-SOZ group for the left hippocampus regardless of SOZ hemisphere. We provide the first evidence to suggest a link between SWR features and memory performance (RAVLT-DR) such that longer SWR duration in the left hippocampus was positively linked with memory performance, as was SWR rate synchronization in the bilateral hippocampi and memory performance. Finally, we highlight a potential link between individual disease features (i.e., disease duration) and performance. Taken together, the results of this study meaningfully contribute to the literature in examining SWR features in humans as biomarkers for long-term memory consolidation and neuroplasticity in reorganizing eloquent cortex.