  Decoding language from neural signals holds considerable theoretical and
practical importance. Previous research has indicated the feasibility of
decoding text or speech from invasive neural signals. However, when using
non-invasive neural signals, significant challenges are encountered due to
their low quality. In this study, we proposed a data-driven approach for
decoding semantic of language from Magnetoencephalography (MEG) signals
recorded while subjects were listening to continuous speech. First, a
multi-subject decoding model was trained using contrastive learning to
reconstruct continuous word embeddings from MEG data. Subsequently, a beam
search algorithm was adopted to generate text sequences based on the
reconstructed word embeddings. Given a candidate sentence in the beam, a
language model was used to predict the subsequent words. The word embeddings of
the subsequent words were correlated with the reconstructed word embedding.
These correlations were then used as a measure of the probability for the next
word. The results showed that the proposed continuous word embedding model can
effectively leverage both subject-specific and subject-shared information.
Additionally, the decoded text exhibited significant similarity to the target
text, with an average BERTScore of 0.816, a score comparable to that in the
previous fMRI study.
