The fluent retrieval and production of movement sequences is essential for a variety of daily activities such as speech, tool-use, musical and athletic performance, but the neural mechanisms underlying sequence planning remain elusive. Here, participants learned sequences of finger presses with different timings and different finger orders, and reproduced them in a magneto-encephalography (MEG) scanner. We classified the MEG patterns immediately preceding each press in the sequence, and examined their dynamics over the production of the whole sequence. Our results confirm a role for the ‘competitive queuing’ of upcoming action representations in the production of learned motor sequences, extending previous computational and non-human primate recording studies to non-invasive measures in humans. In addition, we show that competitive queuing does not simply reflect specific motor actions, but representations of higher-level sequential order that generalise across different motor sequences. Finally, we show that the quality of competitive queuing predicts participants’ production accuracy, and originates from parahippocampal and cerebellar sources. These results suggest that the brain learns and produces multiple behavioural sequences by flexibly combining representations of specific actions with more abstract, parallel representations of sequential structure.

41Retrieval of long-term episodic memories is characterised by synchronised neural activity between 42 hippocampus and ventromedial prefrontal cortex (vmPFC), with additional evidence that vmPFC 43 activity leads that of the hippocampus. It has been proposed that the mental generation of scene 44 imagery is a crucial component of episodic memory processing. If this is the case, then a comparable 45 interaction between the two brain regions should exist during the construction of novel scene 46 imagery. To address this question, we leveraged the high temporal resolution of 47 magnetoencephalography (MEG) to investigate the construction of novel mental imagery. We 48 tasked male and female humans with imagining scenes and single isolated objects in response to 49 one-word cues. We performed source level power, coherence and causality analyses to characterise 50 the underlying inter-regional interactions. Both scene and object imagination resulted in theta 51 power changes in the anterior hippocampus. However, higher theta coherence was observed 52 between the hippocampus and vmPFC in the scene compared to the object condition. This inter-53 regional theta coherence also predicted whether or not imagined scenes were subsequently 54 remembered. Dynamic causal modelling of this interaction revealed that vmPFC drove activity in 55 hippocampus during novel scene construction. Additionally, theta power changes in the vmPFC 56 preceded those observed in the hippocampus. These results constitute the first evidence in humans 57 that episodic memory retrieval and scene imagination rely on similar vmPFC-hippocampus neural 58 dynamics. Furthermore, they provide support for theories emphasising similarities between both 59 cognitive processes, and perspectives that propose the vmPFC guides the construction of context-60 relevant representations in the hippocampus. 61 62 63

Our ability to recall past experiences, autobiographical memories (AMs), is crucial to cognition, endowing us with a sense of self and underwriting our capacity for autonomy.Traditional views assume that the hippocampus orchestrates event recall, whereas recent accounts propose that the ventromedial prefrontal cortex (vmPFC) instigates and coordinates hippocampal-dependent processes. Here we sought to characterise the dynamic interplay between hippocampus and vmPFC during AM recall to adjudicate between these perspectives.Leveraging the high temporal resolution of magnetoencephalography, we found that the hippocampus and the vmPFC showed the greatest power changes during AM retrieval.Moreover, responses in the vmPFC preceded activity in the hippocampus during initiation of AM recall, except during retrieval of the most recent AMs. The vmPFC drove hippocampal activity during recall initiation and also as AMs unfolded over subsequent seconds, and this effect was evident regardless of AM age. These results re-cast the positions of the hippocampus and the vmPFC in the AM retrieval hierarchy, with implications for theoretical accounts of memory processing and systems-level consolidation.

Our aim was to demonstrate the first use of Optically Pumped Magnetoencephalography (OP-MEG) in an epilepsy patient with unrestricted head movement. Current clinical MEG uses a traditional SQUID system for recording MEG signal, where sensors are cryogenically cooled and housed in a helmet in which the patient’s head is fixed. Here we use a different type of sensor (OPM), which operates at room temperature and can be placed directly on the patient’s scalp, permitting free head movement. We performed two 30 minute OP-MEG recording sessions in a patient with refractory focal epilepsy and compared these with clinical scalp EEG performed earlier. OP-MEG was able to identify analogous interictal activity to scalp EEG, and source localise this activity to an appropriate brain region. This is the first application of OP-MEG in human epilepsy. Future directions include simultaneous EEG/OP-MEG recording and prolonged OP-MEG telemetry.