The ancient term "sense" is one of the most important topics in psychology. The brain receives information from the outside world through the visual, auditory, olfactory, taste, and tactile sensory channels. Different senses form human cognition and experience by converting information from the real world into electrical signals that the brain can process. Sensory deprivation occurs when the amount of sensory stimuli that a person receives decreases or falls below a normal threshold, and this change becomes a risk factor for neuropsychiatric disorders such as depression. Therefore, different sensory impairments are involved in the central mechanism of depression, and appropriate stimulation based on different sensory channels and multi-sensory combined interventions may also play a significant role in its treatment. Among the effects of different sensory functions on mental health, depression has a greater proportion; however, the patient's disease type, age stage, gender difference (especially during pregnancy and postpartum period), and other factors can affect the susceptibility to depression. Yet, the sensory stimulation that the body receives is not “more is better”; excessive sensory stimulation will also lead to the imbalance of the body's sensory and emotional function, as blue light and noise over stimulation will induce depression. The appropriate sensory stimulation can be used as a "compensatory input" to effectively improve the symptoms and severity of depression.
Taking "symptoms-brain region-mechanism-treatment" as the logical thread, the author systematically reviewed the clinical symptoms of depression, the neural mechanisms of depression, and the antidepressant treatments based on sensory stimulation for the first time in persons with five major sensory disorders. The results show that different sensory dysfunctions in the neural mechanisms related to depression may represent the different pathologies of depression, involving neuronal electrical activity (firing of certain neurons and activation of neural circuits, etc.) and neural biochemical changes (neuroplasticity and neurogenesis, inflammatory immunity and HPA axis, neurohormones and neurotransmitters, etc.); these mainly occur in the limbic system (amygdala, hippocampus, hypothalamus, nucleus accumbens, cingulate gyrus, and olfactory bulb) and its adjacent brain regions (lateral habenula nucleus, nucleus of solitary tract, superior colliculus), which involve the insular lobe, temporal lobe, frontal lobe, etc. The review found that individualized visual cortex transcranial magnetic stimulation, visual art therapy, transcutaneous auricular vagus nerve stimulation, frequency conversion music therapy, olfactory-based deep brain stimulation, intranasal administration, psychological behavioral therapy based on sugar intake, massage therapy with music and fragrance, and reiki therapy had good curative effects and few side effects for the improvement of depression symptoms, and were appropriate for clinical application.
At present, the research on the relationship between sensory disorders as well as their treatment and neuropsychiatric diseases is still very immature, the research on the underlying mechanisms is still in the initial stage, and the development of relevant treatment methods is just beginning. There are still many problems that need to be clarified and solved. Future research should focus on the extraction of different sensory information, which will provide a new research perspective for the etiology and treatment of human depression. In the interdisciplinary context of physics, chemistry, psychology, biology and computer science, researchers should develop how to make reasonable assessments based on certain sensory parameters to assist the medical treatment of depression. For example, with the help of artificial intelligence technology, audio-visual sensory information will be digitized, more practical wearable devices will be invented, and virtual reality and augmented-reality technology will be accelerated to contribute to depression inquiry. In a word, the extraction of sensory information will help in the intervention and rehabilitation of mental diseases, and enable digital medicine, technological medicine, and precision medicine, to rewrite the model of traditional medical thinking, and promote humans into a new medical era.
