Replicating the Bright-Light Therapy of Seasonal Affective Disorder through Dual-Gate Dielectric Synaptic Transistors: An Exploration of Neuromorphic Computing Approaches

We fabricate a synaptic device employing a TiO2 channel highly responsive to optical stimuli and incorporating a dual-gate dielectric, one of which facilitates charge trapping at the interface. Unlike conventional synaptic transistors responding to only a single type of stimulus such as optical or electrical stimulation, our device stands out by simulating synaptic behavior by integrating both optical and electrical stimuli. These distinctive attributes enable us to elicit excitatory postsynaptic current via optical and inhibitory postsynaptic currents through electrical stimulation. Notably, the lifetime of the optical synaptic behaviors was approximately 12 times longer than that of the electrical stimulation. Additionally, employing the paired-pulse facilitation index, distinct time constants are computed corresponding to the rapid and slow phases, mirroring a pattern akin to that observed in a bio-synapse. We establish a nonlinearity factor v = 7.21×10-4 through short-term plasticity to long-term plasticity transition, demonstrating remarkable linearity. We achieve 2048 analog states characterized by exceptional linearity. Finally, we replicate human depression, known as seasonal affective disorder, by employing electrical stimulation to emulate feelings of melancholy. Subsequently, we replicate light therapy for seasonal affective disorder by incorporating light stimulation. This outcome signifies a promising pathway for future investigations into emulating human brain activity.