The Effects of Galactic Cosmic Rays on the Central Nervous System: From Negative to Unexpectedly Positive Effects That Astronauts May Encounter

Abstract

Galactic cosmic rays (GCR) pose a serious threat to astronauts’ health during deep space missions. The possible functional alterations of the central nervous system (CNS) under GCR exposure can be critical for mission success. Despite the obvious negative effects of ionizing radiation, a number of neutral or even positive effects of GCR irradiation on CNS functions were revealed in ground-based experiments with rodents and primates. This review is focused on the GCR exposure effects on emotional state and cognition, emphasizing positive effects and their potential mechanisms. We integrate these data with GCR effects on adult neurogenesis and pathological protein aggregation, forming a complete picture. We conclude that GCR exposure causes multidirectional effects on cognition, which may be associated with emotional state alterations. However, the irradiation in space-related doses either has no effect or has performance enhancing effects in solving high-level cognition tasks and tasks with a high level of motivation. We suppose the model of neurotransmission changes after irradiation, although the molecular mechanisms of this phenomenon are not fully understood.

Combined Ionizing Radiation Exposure by Gamma Rays and Carbon-12 Nuclei Increases Neurotrophic Factor Content and Prevents Age-Associated Decreases in the Volume of the Sensorimotor Cortex in Rats

“…An important issue is to uncover the cellular and molecular mechanisms responsible for the preservation of sensorimotor cortex volume in irradiated rats. In line with existing literature data [1], the damage properties of IR and, in particular, HZE are undeniable. At the same time, a lesion in the neocortex induces a transient increase in the proliferation as well as neurogenesis in the subventricular zone.…”

“…Studies have shown that such low-dose low-LET pre-irradiation significantly modulates the organism's response to irradiation by HZE [68]. When choosing the HZE component, we relied on the fact that 12 C 6+ is the most common nucleus after H + and 4 He 2+ in the composition of GCR [69], while the LET value was near the median value on the GCR LET spectrum measured on the Mars surface and during the Earth-Mars cruise [1]. Based on the dosimetric study, low-LET exposure will be predominant during spaceflight Moreover, during the realization of crewed deep-space missions, more advanced shielding will be used, which will also shift the particle spectrum towards the low-LET component and may reduce the equivalent dose by up to 30% [71,72].…”

“…The advent of the era of crewed deep-space (interplanetary) missions has significantly intensified the study of medical and biological effects of ionizing radiation (IR), whose significance increases notably when a spacecraft travels beyond the Earth’s magnetic field. Studies have shown that the effect of IR, including the most dangerous component—high-energy heavy charged particles (HZE)—is ambiguous: both negative and positive effects on central nervous system (CNS) functions have been found [ 1 ].…”

“…It is noteworthy that low-dose γ-rays irradiation (63 mGy, 60 Co) stimulates exploratory activity at 18 months post-irradiation [11]. The mechanisms responsible for the stimulatory effects of IR on locomotor and exploratory activity remain undiscovered, but there is speculation that this is part of a neuroadaptive response [1].…”