Memory Transfer of Random Time Patterns Across Modalities

Perception is sensitive to statistical regularities in the environment, including temporal characteristics of sensory inputs. Interestingly, temporal patterns implicitly learned within one modality can also be recognised in another modality. However, it is unclear how cross-modal learning transfer affects neural responses to sensory stimuli. Here, we recorded neural activity of human volunteers (N=24, 12 females, 12 males) using electroencephalography (EEG), while participants were exposed to brief sequences of randomly-timed auditory or visual pulses. Some trials consisted of a repetition of the temporal pattern within the sequence, and subjects were tasked with detecting these trials. Unknown to the participants, some trials reappeared throughout the experiment, inducing implicit learning. Replicating previous behavioural findings, we showed that participants benefit from temporal information learned in one modality, and that they can apply this information to stimuli presented in another modality. Furthermore, using an analysis of EEG response learning curves, we showed that learning temporal structures within modalities modulates single-trial EEG response amplitudes, and that these effects could be localised to modality-specific cortical regions. Furthermore, learning transfer across modalities was associated with modulations of single-trial EEG response amplitudes, as well as beta-band power in the right inferior frontal gyrus. The neural effects of learning transfer were similar both when temporal information learned in audition was transferred to visual stimuli and vice versa. Thus, both modality-specific mechanisms for learning of temporal information, and general mechanisms which mediate learning transfer across modalities, have distinct physiological signatures that are observable in the EEG. Significance statementTemporal patterns governing sensory stimuli can be extracted and used to optimise perceptual processing. However, it is unclear what brain mechanisms mediate the learning of temporal information within a sensory modality, and how the effects of learning can be applied to another modality. Here, we presented auditory and visual stimuli to human participants while recording their brain activity using electroencephalography (EEG). We observed behavioural benefits and neural signatures of subconscious temporal pattern learning within a sensory modality, as well as transfer of patterns from one modality to another (audition to vision and vice versa). Interestingly, the neural correlates of temporal learning within modalities relied on modality-specific brain regions, while learning transfer affected activity in frontal regions, suggesting distinct mechanisms.