Brain-computer interface (BCI) technology aims to help individuals with disability to control assistive devices and reanimate paralyzed limbs. Our study investigated the feasibility of an electrocorticography (ECoG)-based BCI system in an individual with tetraplegia caused by C4 level spinal cord injury. ECoG signals were recorded with a high-density 32-electrode grid over the hand and arm area of the left sensorimotor cortex. The participant was able to voluntarily activate his sensorimotor cortex using attempted movements, with distinct cortical activity patterns for different segments of the upper limb. Using only brain activity, the participant achieved robust control of 3D cursor movement. The ECoG grid was explanted 28 days post-implantation with no adverse effect. This study demonstrates that ECoG signals recorded from the sensorimotor cortex can be used for real-time device control in paralyzed individuals.

Brainstem nuclei have well established roles in generating nonlearned rhythmic behaviors or as output pathways for more complex, forebrain-generated behaviors. However, the role of the brainstem in providing information to the forebrain that is used to initiate or assist in the control of complex behaviors is poorly understood. In this study, we used electrical microstimulation in select nuclei of the avian song system combined with recordings of acoustic and respiratory output to examine how forebrain and brainstem nuclei interact in the generation of learned vocal motor sequences. We found that brief stimulation in the forebrain nuclei HVC (used as a proper name) and RA (robust nucleus of the arcopallium) caused a short-latency truncation of ongoing song syllables, which ultimately led to a cessation of the ongoing motor sequence. Stimulation within the brainstem inspiratory-related nucleus paraambigualis, which receives input from RA and projects back to HVC via the thalamus, caused syllable truncations and interruptions similar to those observed in HVC and RA. In contrast, stimulation in the tracheosyringal portion of the hypoglossal nucleus, which innervates the syrinx (the avian vocal organ) but possesses no known projections back into the song system, did not cause any significant changes in the song motor pattern. These findings suggest that perturbation of premotor activity in any nucleus within the recurrent song system motor network will disrupt the ongoing song motor sequence. Given the anatomical organization of this network, our results are consistent with a model in which the brainstem respiratory nuclei form an integral part of the song motor programming network by providing timing signals to song control nuclei in the forebrain.

Electrocorticography (ECoG), used as a neural recording modality for brain-machine interfaces (BMIs), potentially allows for field potentials to be recorded from the surface of the cerebral cortex for long durations without suffering the host-tissue reaction to the extent that it is common with intracortical microelectrodes. Though the stability of signals obtained from chronically-implanted ECoG electrodes has begun receiving attention, to date little work has characterized the effects of long-term implantation of ECoG electrodes on underlying cortical tissue. We implanted a high-density ECoG electrode grid subdurally over cortical motor areas of a Rhesus macaque for 666 days. Histological analysis revealed minimal damage to the cortex underneath the implant, though the grid itself was encapsulated in collagenous tissue. We observed macrophages and foreign body giant cells at the tissue-array interface, indicative of a stereotypical foreign body response. Despite this encapsulation, cortical modulation during reaching movements was observed more than 18 months post-implantation. These results suggest that ECoG may provide a means by which stable chronic cortical recordings can be obtained with comparatively little tissue damage, facilitating the development of clinically-viable brain-machine interface systems.

Brainstem motor structures send output commands to the periphery and are dynamically modulated by telencephalic inputs. Little is known, however, about ascending brainstem control of forebrain motor structures. Here, we provide the first evidence for bottom-up activation of forebrain motor centers by the respiratory brainstem. We show that, in the avian vocal control system, activation of the brainstem inspiratory nucleus paraambigualus (PAm), a likely homolog of the mammalian rostral ventral respiratory group, can drive neural activity bilaterally in the forebrain vocal control nuclei HVC (used as a proper name) and the robust nucleus of the arcopallium (RA). Furthermore, this activation is abolished by lesions of nucleus uvaeformis (Uva), a thalamic nucleus necessary for song production. We identify a type of bursting neuron within PAm whose activity is correlated, in an Uva dependent manner, to bursting activity in RA, rather than to the respiratory rhythm, and is robustly active during the production of stimulus evoked vocalizations. Because this ascending input results in cross-hemisphere activation, our results suggest a crucial role for the respiratory brainstem in coordinating forebrain motor centers during vocal production.

The caudal dentate nucleus (DN) in lateral cerebellum is connected with two visual/oculomotor areas of the cerebrum: the frontal eye field and lateral intraparietal cortex. Many neurons in frontal eye field and lateral intraparietal cortex produce "delay activity" between stimulus and response that correlates with processes such as motor planning. Our hypothesis was that caudal DN neurons would have prominent delay activity as well. From lesion studies, we predicted that this activity would be related to self-timing, i.e., the triggering of saccades based on the internal monitoring of time. We recorded from neurons in the caudal DN of monkeys (Macaca mulatta) that made delayed saccades with or without a self-timing requirement. Most (84%) of the caudal DN neurons had delay activity. These neurons conveyed at least three types of information. First, their activity was often correlated, trial by trial, with saccade initiation. Correlations were found more frequently in a task that required self-timing of saccades (53% of neurons) than in a task that did not (27% of neurons). Second, the delay activity was often tuned for saccade direction (in 65% of neurons). This tuning emerged continuously during a trial. Third, the time course of delay activity associated with self-timed saccades differed significantly from that associated with visually guided saccades (in 71% of neurons). A minority of neurons had sensory-related activity. None had presaccadic bursts, in contrast to DN neurons recorded more rostrally. We conclude that caudal DN neurons convey saccade-related delay activity that may contribute to the motor preparation of when and where to move.