Investigating the Serotonergic Modulation of Orientation Tuning of Neurons in Primary Visual Cortex of Anesthetized Mice.

Serotonin is one of the well-known neuromodulators involved in many physiological functions of the brain, such as sensory processing. It can play an essential role in producing perceptual psychotic episodes following the use of psychedelic drugs. Neural mechanisms of changes in cortical processing by the serotonergic system are not elucidated enough. In this study, we showed the electrical stimulation of the dorsal raphe nucleus as the main resource for projecting serotonergic neurons to the visual cortex, causing to decrease in visual-evoked responses of neurons in the primary visual cortex without changing the spontaneous activity. This effect may lead to an imbalance between the brain's intrinsic and stimulus-evoked activity and result in various kinds of psychiatric disorders, such as visual hallucinogenic experiences in schizophrenia and autism. Accordingly, it is crucial to understand the mechanisms by which serotonin affects the rapid and long-term activity of neocortical circuits. Such studies can be helpful in the diagnosis and treatment of disorders related to the neuromodulatory roles of the serotonergic system by providing new methods for rebalancing these intricate components.