Training on multiple days results in better learning in embedded eyeblink conditioning in young human adults

Abstract

Eyeblink conditioning is mediated by similar cerebellar pathways in humans and animals and is typically investigated using delay or trace protocols. These studies show that humans can easily acquire eyeblink conditioning within a single day of training whereas animals usually require around 3-10 days of acquisition training before they consistently exhibit conditioned responses. We aimed to study how a multiple-day acquisition training, across 3 non-consecutive days of a month, with 100 trials per day affected learning in young human adults. We employed an embedded protocol in which the US is embedded within the CS duration without co-termination. Our findings show, for the first time in humans using this protocol, that learning improves substantially on days 2 and 3. Our findings encourage research into how human cerebellum mediates consolidation across several days of eyeblink conditioning as well as into the neurocognitive mechanisms of the relatively underexplored embedded eyeblink conditioning protocol.

Fig. 1. Heatplots on blink amplitude on successive training days.

a Shows the amplitude on all trials (paired and CS-alone) before, during and after the presentation of the tone and the airpuff (vertical white lines) on three training days (horizontal white lines). b Shows the blink amplitude on CS-alone trials where there was no airpuff. CRs emerged on day one (trials 0–100) and became more frequent with larger amplitudes on days two and three (trials 101–300).

Fig. 2. Average blink profiles on successive training days.

Average blink profiles on CS-alone trials on three days of training, showing marked improvement in blink amplitude by the end of day 3.

Fig. 3. CR percentage on successive training days.

Shows the CR percentage (mean + /−SEM) on successive blocks of 10 trials across the three training days.

Fig. 4. Eyeblink conditioning protocol and experimental setup.

a A CS-US paired trial using an embedded protocol. b 3-day acquisition protocol. c The experimental setup consists of custom-made glasses, attached with magnetic sensor and airpuff nozzle. The magnet is glued to the participant’s left eyelid. The CS, US, and GMR chip readings are recorded and controlled via Spike2 v9.10 and CED Micro1401 AD converter. Created in BioRender.com.