Sensory-Induced Human LTP-Like Synaptic Plasticity – Using Visual Evoked Potentials to Explore the Relation Between LTP-Like Synaptic Plasticity and Visual Perceptual Learning

Abstract

ObjectiveStimulus-selective response modulation (SRM) of sensory evoked potentials represents a well-established non-invasive index of long-term potentiation-like (LTP-like) synaptic plasticity in the human sensory cortices. Although our understanding of the mechanisms underlying stimulus-SRM has increased over the past two decades, it remains unclear how this form of LTP-like synaptic plasticity is related to other basic learning mechanisms, such as perceptual learning. The aim of the current study was twofold; firstly, we aimed to corroborate former stimulus-SRM studies, demonstrating modulation of visual evoked potential (VEP) components following high-frequency visual stimulation. Secondly, we aimed to investigate the association between the magnitudes of LTP-like plasticity and visual perceptual learning (VPL).Methods42 healthy adults participated in the study. EEG data was recorded during a standard high-frequency stimulus-SRM paradigm. Amplitude values were measured from the peaks of visual components C1, P1, and N1. Embedded in the same experimental session, the VPL task required the participants to discriminate between a masked checkerboard pattern and a visual “noise” stimulus before, during and after the stimulus-SRM probes.ResultsWe demonstrated significant amplitude modulations of VEPs components C1 and N1 from baseline to both post-stimulation probes. In the VPL task, we observed a significant change in the average threshold levels from the first to the second round. No significant association between the magnitudes of LTP-like plasticity and performance on the VPL task was evident.ConclusionTo the extent of our knowledge, this study is the first to examine the relationship between the visual stimulus-RM phenomenon and VPL in humans. In accordance with previous studies, we demonstrated robust amplitude modulations of the C1 and N1 components of the VEP waveform. However, we did not observe any significant correlations between modulation magnitude of VEP components and VPL task performance, suggesting that these phenomena rely on separate learning mechanisms implemented by different neural mechanisms.

Long-Term Potentiation-Like Visual Synaptic Plasticity Is Negatively Associated With Self-Reported Symptoms of Depression and Stress in Healthy Adults

“…Specifically, modification of VEP amplitudes following repeated visual stimulation have shown considerable promise as a non-invasive in vivo assay of synaptic plasticity and function (e.g., Teyler et al, 2005 ). In these studies, experimental paradigms typically record a VEP baseline prior to introducing high-frequent or prolonged visual stimulation to induce modulation of visually evoked potentials post-stimulation (e.g., Spriggs et al, 2019 ; Valstad et al, 2020 ; Lengali et al, 2021 ; Rygvold et al, 2021 ). These experimental VEP paradigms are typically designed to be analogous to invasive procedures inducing synaptic plasticity in brain slices ( Normann et al, 2007 ).…”

Sensory Tetanization to Induce LTP-Like Plasticity: A Review and Reassessment of the Approach

“…While sensory SENSORY TETANIZATION TO INDUCE LTP-LIKE PLASTICITY 24 tetanization may be a valuable non-invasive approach to induce LTP-like plasticity in humans (Kirk et al, 2021;Sumner et al, 2020b), contrasting effects across studies must be considered. As previously discussed, some studies find that tetanization can increase the amplitude of event related potentials (Kleeva et al, 2022;Lei et al, 2017;Lengali et al, 2021;McNair et al, 2006;Moore et al, 2020;Moore & Loprinzi, 2021;Normann et al, 2007;Ross et al, 2008;Rygvold et al, 2020;Smallwood et al, 2015;Spriggs et al, 2017;Spriggs et al, 2018;Spriggs et al, 2019;Sumner et al, 2018;Wilson et al, 2017;Zak et al, 2018), others find no change in response amplitude following tetanization (D'Souza et al, 2018;Rygvold et al, 2020;Sumner et al, 2018), and still others, including ourselves, find that response amplitudes decrease after tetanization (Kleeva et al, 2022;Klöppel et al, 2015;Rebreikina et al, 2021;Wynn et al, 2019). These conflicting results are troubling, especially when considering that most studies use methods very similar to those initially reported by Clapp et al (2005a) and Teyler et al (2005).…”

“…The seminal studies introducing sensory tetanization as an in vivo approach to study plasticity reported an increased N1 and N1b amplitude in the sensory-evoked ERP after tetanization to auditory and visual (Teyler et al, 2005) stimuli, respectively. Subsequent studies have since replicated these results in young healthy adults, reporting increases in the N1 and N1b (and the C1, P1, P2) amplitudes of sensory-evoked ERPs after tetanization (Kleeva et al, 2022;Lei et al, 2017;Lengali et al, 2021;McNair et al, 2006;Moore et al, 2020;Moore & Loprinzi, 2021;Normann et al, 2007;Ross et al, 2008;Rygvold et al, 2020;Smallwood et al, 2015;Spriggs et al, 2017;Spriggs et al, 2018;Spriggs et al, 2019;Sumner et al, 2018;Wilson et al, 2017;Zak et al, 2018). However, despite the number of studies finding sensory ERP amplitudes increase after tetanization, several others have found no effect of tetanization on response amplitudes (D'Souza et al, 2018;Rygvold et al, 2020;Sumner et al, 2018) and several more have even found that response amplitudes decrease after tetanization (Kleeva et al, 2022;Klöppel et al, 2015;Rebreikina et al, 2021;Spriggs et al, 2018;Wynn et al, 2019).…”

“…Such variability in SENSORY TETANIZATION TO INDUCE LTP-LIKE PLASTICITY 29 amplitude change after sensory tetanization is not limited to the N1/N1b component. C1 amplitude can increase (Rygvold et al, 2020), decrease (Forsyth et al, 2015;Lengali et al, 2021;Zak et al, 2018), or not change (Elvsåshagen et al, 2012) after tetanization.…”

“…Such variability in response amplitude changes after sensory tetanization are not limited to the N1 or N1b components. C1 amplitude can increase (Rygvold et al, 2020), decrease (Forsyth et al, 2015; Lengali et al, 2021; Zak et al, 2018), or not change (Elvsåshagen et al, 2012) after tetanization. Similarly, P1 amplitude can increase (Elvsåshagen et al, 2012; Normann et al, 2007; Rygvold et al, 2020; Zak et al, 2018) or remain unchanged (Lengali et al, 2021; Teyler et al, 2005) after tetanization.…”