Experience-dependent modulation of the visual evoked potential: testing effect sizes, retention over time, and associations with age in 415 healthy individuals

Abstract

29Experience-dependent modulation of the visual evoked potential (VEP) is a 30 promising proxy measure of synaptic plasticity in the cerebral cortex. However, 31 existing studies are limited by small to moderate sample sizes as well as by 32 considerable variability in how VEP modulation is quantified. In the present study, we 33 used a large sample (n = 415) of healthy volunteers to compare different 34 quantifications of VEP modulation with regards to effect sizes and retention of the 35 modulation effect over time. We observed significant modulation for VEP 36 components C1 (Cohen's d = 0.53), P1 (d = 0.66), N1 (d = -0.27), N1b (d = -0.66), 37 but not P2 (p = 0.1), and in one time-frequency cluster (~30 Hz and ~70 ms post-38 stimulus; d = -0.48), 2-4 minutes after 2 Hz prolonged visual stimulation. For 39 components N1 (d = -0.21) and N1b (d = -0.38), as well for the time-frequency cluster 40 (d = -0.33), this effect was retained after 54-56 minutes. Moderate to high 41 correlations (r = [0.39, 0.69]) between modulation at different postintervention blocks 42 revealed a relatively high temporal stability in the modulation effect for each VEP 43component. However, different VEP components also showed markedly different 44 temporal retention patterns. Finally, P1 modulation correlated positively with age (t = 45 5.26), and was larger for female participants (t = 3.91), with no effects of either age or 46 sex on N1 and N1b potentiation. These results provide strong support for VEP 47 modulation, and especially N1b modulation, as a robust measure of synaptic 48 plasticity, but underscore the need to differentiate between components, and to 49 control for demographic confounders. 50

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

“…There is one study that reported a change in visual-evoked response amplitudes in older adults, but the response amplitudes increased after visual tetanization, contrasting with our results (de Gobbi Porto et al, 2015). Our finding that older adults demonstrated a smaller decrease in auditory-evoked response amplitudes than younger adults after auditory tetanization is consistent with one study finding similar age-group differences in the decrease in visual-evoked amplitudes after visual tetanization (Abuleil et al, 2019), but it is inconsistent with another study finding that age is unrelated to changes in visual-evoked response amplitudes after visual tetanization (Valstad et al, 2020). In contrast, our finding that decreases in visual-evoked response amplitudes after visual tetanization are similar for younger and older adults is inconsistent with the one study finding older adults exhibit a smaller decrease in visual-evoked response amplitudes after visual tetanization (Abuleil et al, 2019), but it is consistent with the study finding no relationship between age and visual tetanization (Valstad et al, 2020).…”

Sensory tetanisation to induce long‐term‐potentiation‐like plasticity: A review and reassessment of the approach

“…There is one study that reported a change in visual‐evoked response amplitudes in older adults, but the response amplitudes increased after visual tetanisation, contrasting with our results (de Gobbi Porto et al, 2015). Our finding that older adults demonstrated a smaller decrease in auditory ‐evoked response amplitudes than younger adults after auditory tetanisation is consistent with one study finding similar age group differences in the decrease in visual ‐evoked amplitudes after visual tetanisation (Abuleil et al, 2019), but it is inconsistent with another study finding that age is unrelated to changes in visual ‐evoked response amplitudes after visual tetanisation (Valstad et al, 2020). In contrast, our finding that decreases in visual ‐evoked response amplitudes after visual tetanisation are similar for younger and older adults is inconsistent with the one study finding older adults exhibit a smaller decrease in visual ‐evoked response amplitudes after visual tetanisation (Abuleil et al, 2019), but it is consistent with the study finding no relationship between age and visual tetanisation (Valstad et al, 2020).…”

Stability of steady-state visual evoked potential contrast response functions

“…Additionally, it is important to note along these lines that there is large variability in the sensory LTP literature. Some have questioned if sensory LTP is even a valid construct (Dias et al, 2022), and the largest studies have shown modest if any consistent effects across hundreds of participants (Valstad et al, 2020). Our finding of response stability with repeated stimulus presentation provides further support for VEP stability, but a more thorough investigation of stimulus parameters is needed to determine in what regime ssVEP stimuli do or do not generate neuroplastic effects.…”

“…Achieving stable repeated measures with sensory-evoked potentials is further complicated by the fact that at least under certain conditions repeated presentation of visual or auditory stimuli can induce neuroplasticity that resembles long-term potentiation(LTP) (Sanders et al, 2018; Sumner et al, 2020). Although previous findings are somewhat conflicting (Dias et al, n.d.; Valstad et al, 2020), several labs have demonstrated that showing 9 Hz flash stimuli for 2 minutes and 2 Hz contrast-reversing stimuli for 10 minutes can both produce an LTP-like increase in the amplitude of the visual evoked potential. Whether repeated contrast-sweep stimuli cause an LTP-like effect has not been tested to our knowledge.…”