Periodic Reporting for period 1 - Re.B.Us (Rewiring Brain Units - bridging the gap of neuronal communication by means of intelligent hybrid systems)
Período documentado: 2016-03-16 hasta 2018-03-15
People suffering for disorders of the Central Nervous System (CNS) often have to cope with every-day challenges. In spite of our strong commitment to primary prevention, CNS disorders significantly impact on the global burden of disease. Thus, restoring the physiological function of a dysfunctional brain is a primary challenge. As pharmacological treatment is not suitable to restore broken neuronal pathways, research is exploring biological and engineering approaches, but the sole exploitation of either of these strategies is technically limited by inherent pitfalls. Neural transplants benefit of the intrinsic plasticity of biological neurons, yet the interaction of the graft with the host nervous tissue is consequently poorly predictable. Silicon-based technology provides highly controllable systems, yet at the cost of limited flexibility. Re.B.Us originated from the long-term vision of repairing dysfunctional brain pathways by means of biohybrid transplants in which biological neurons establish a symbiotic interaction with an artificial (electronic) counterpart, so as to pursue a self-healing process of the diseased brain.
The ultimate goal of Re.B.Us was to provide the proof of principle of a novel hybrid exploitation strategy to overcome the limitations inherent to the sole use of biological or engineering approaches for brain repair. Specifically, the project has stepped through the following objectives:
(1) replace the compromised brain function via open-loop neuromodulation
(2) re-establish a functional dialogue between disconnected brain areas through feedback-operated electronic bridges
(3) use electronic bridges to establish a functional dialogue between specific areas of distinct brain slices, of which one would act as diseased host and the other would serve as functional graft tissue
The ultimate goal of Re.B.Us was to provide the proof of principle of a novel hybrid exploitation strategy to overcome the limitations inherent to the sole use of biological or engineering approaches for brain repair. Specifically, the project has stepped through the following objectives:
(1) replace the compromised brain function via open-loop neuromodulation
(2) re-establish a functional dialogue between disconnected brain areas through feedback-operated electronic bridges
(3) use electronic bridges to establish a functional dialogue between specific areas of distinct brain slices, of which one would act as diseased host and the other would serve as functional graft tissue
In order to achieve the proof-of-concept of the feasibility of the biohybrid approach to brain repair, Re.B.Us has combined microelectrode array (MEA) electrophysiology from brain slices with computational and engineering tools to restore the physiological function in an in vitro model of temporal lobe epilepsy (TLE). TLE is the most common partial complex epileptic syndrome and the most frequently unresponsive to pharmacological therapy. The hippocampus, a key brain area for learning and memory processes, is primarily involved in TLE and its functional impairment leads to progressive psychiatric and cognitive co-morbidities. In in vitro models of TLE, the functional interactions between the hippocampus and the parahippocampal cortex have been extensively characterized. Specifically, the CA3 hippocampal subfield plays a crucial role in controlling the propensity of the parahippocampal cortex to generate seizure activity. In epileptic tissue, the CA3 function is impaired and seizure activity generated by the cortex is unrestrained. The experimental work pursued in Re.B.Us has followed sequential logical steps based on these known network interactions in experimental TLE models. First, analysis of the CA3-driven pattern has revealed the presence of lognormal temporal dynamics and their preservation during acutely induced epileptiform behavior and in chronic epilepsy. Mimicking this pattern via open-loop lognormal electrical stimulation delivered to the subiculum (the hippocampal output gate) could successfully control seizure activity generation in the parahippocampal cortex. Further, this paradigm proved more efficient than periodic pacing, in that it delivered less electrical pulses, thereby imposing less stress to the brain tissue, while promising to improve the battery life of neuromodulators. These results anticipated the possibility of bridging the gap of communication between the hippocampus and the parahippocampal cortex to treat TLE. Thus, in the next set of experiments, the project pursued a closed-loop control strategy to functionally reconnect these two structures via electronic bridges. Specifically, three closed-paradigms were implemented: (i) unidirectional bridging within the same brain slice, (iii) unidirectional bridging between two distinct brain slices, and (ii) bidirectional bridging between two distinct brain slices. These experiments demonstrated the feasibility of bridging disconnected brain areas via a feedback loop to re-establish their physiological dialogue; specifically, they demonstrated that it is possible to exploit the intrinsic ability of CA3 to generate a sustained anti-ictogenic pattern to control cortical ictogenicity. Further, they heralded the possibility of using graft brain tissue to repair epileptic brain circuits, or, in a wider perspective, as a biological neuromodulator.
In pursuing the experimental work, Re.B.Us has developed software and hardware tools for advanced signal processing and seizure detection, stimulus pattern generation, and unidirectional and bidirectional closed-loop control, including a custom PCB purposely designed for Re.B.Us (Fig. 1) in collaboration with the company PCB Project (Lucca, Italy).
In pursuing the experimental work, Re.B.Us has developed software and hardware tools for advanced signal processing and seizure detection, stimulus pattern generation, and unidirectional and bidirectional closed-loop control, including a custom PCB purposely designed for Re.B.Us (Fig. 1) in collaboration with the company PCB Project (Lucca, Italy).
Re.B.Us has contributed significant advancement to the neurosciences, and particularly to epilepsy research and to the neurotechnology field. The project has demonstrated for the first time that it is possible to restore the compromised brain function by directly mimicking a lost brain pattern via a neuromodulation strategy that resembles the physiological working mode of the brain and outclasses the performance of current neuromodulation approaches like periodic pacing. Most importantly, the closed-loop experiments have brought new insights that are highly relevant to the design of brain prostheses and to the future implementation of biohybrid transplants to heal epilepsy. In this regard, Re.B.Us has stepped beyond the state-of-the-art in many ways. First, it has adopted for the first time ever a closed-loop bridging approach to functionally reconnect the hippocampus and the parahippocampal cortex in an in vitro model of TLE. The results so-obtained envisage the possibility of exploiting hippocampal rhythms to control seizures by means of a bridging neuroprosthesis. Second, by establishing a functional dialogue between the hippocampus of a graft brain slice and the parahippocampal cortex of a host brain slice, Re.B.Us has adopted an unprecedented paradigm that has significantly advanced the concept of biohybrid neural transplants. Specifically, the experimental observations indicate that the establishment of a functional reciprocal dialogue between the hippocampus and the parahippocampal cortex is feasible and plausible, as it can actually recover the physiological function of brain circuits that have been stricken by TLE. These concepts can be extended to other brain disorders, such as stroke and Parkinson’s disease. Re.B.Us has laid the foundation of a novel paradigm that heralds the possibility of healing brain disorders by means of biohybrid transplants that will naturally adapt to and integrate within the host brain, while not being entrained by pathological activity, thanks to the joint exploitation of the intrinsically adaptive behavior of biological brain tissue and the functional control operated by engineered implantable devices. These results have a high translational potential and represent the starting point for future investigations.