Effects of theanine on cognition

Background: Theanine is an amino acid present in green tea capable of acting on certain neurological parameters. In this perspective, the literature points to possible effects of this amino acid on cognitive function. Objectives: To investigate the effects of theanine on cognition. Methods: A literature review was conducted on PubMed using the descriptors “Theanine” and “Cognition”, as well as their variations obtained in MeSH. In addition, we selected studies carried out on humans in the last five years. In this process, 25 articles were found, of which three were chosen to compose the scope of this abstract. Results: Evidences suggested that the administration of theanine sharply reduced the reaction time to visual stimuli - one of the main components tested in the attentional assessment. In addition, another study pointed out that, since the chemical structure of theanine is similar to glutamate, it is able to act decisively as a neurotransmitter linked to memory, potentiating it in healthy adults and in elderly people with cognitive decline. Finally, the third article correlated the use of theanine with greater accuracy in tasks of rapid information processing and the reduction of mental fatigue - factors that can reinforce the ability to concentrate. Conclusions: Studies have shown that theanine acts positively on the parameters of attention, memory and concentration, contributing significantly to the improvement of cognitive function.

Direct imaging of rapid tethering of synaptic vesicles accompanying exocytosis at a fast central synapse

A high rate of synaptic vesicle (SV) release is required at cerebellar mossy fiber terminals for rapid information processing. As the number of release sites is limited, fast SV reloading is necessary to achieve sustained release. However, rapid reloading has not been observed directly. Here, we visualize SV movements near presynaptic membrane using total internal reflection fluorescence (TIRF) microscopy. Upon stimulation, SVs appeared in the TIRF-field and became tethered to the presynaptic membrane with unexpectedly rapid time course, almost as fast as SVs disappeared due to release. However, such stimulus-induced tethering was abolished by inhibiting exocytosis, suggesting that the tethering is tightly coupled to preceding exocytosis. The newly tethered vesicles became fusion competent not immediately but only 300 ms to 400 ms after tethering. Together with model simulations, we propose that rapid tethering leads to an immediate filling of vacated spaces and release sites within <100 nm of the active zone by SVs, which serve as precursors of readily releasable vesicles, thereby shortening delays during sustained activity.

Neural shutdown under stress: an evolutionary perspective on spreading depolarization

Neural function depends on maintaining cellular membrane potentials as the basis for electrical signaling. Yet, in mammals and insects, neuronal and glial membrane potentials can reversibly depolarize to zero, shutting down neural function by the process of spreading depolarization (SD) that collapses the ion gradients across membranes. SD is not evident in all metazoan taxa with centralized nervous systems. We consider the occurrence and similarities of SD in different animals and suggest that it is an emergent property of nervous systems that have evolved to control complex behaviors requiring energetically expensive, rapid information processing in a tightly regulated extracellular environment. Whether SD is beneficial or not in mammals remains an open question. However, in insects, it is associated with the response to harsh environments and may provide an energetic advantage that improves the chances of survival. The remarkable similarity of SD in diverse taxa supports a model systems approach to understanding the mechanistic underpinning of human neuropathology associated with migraine, stroke, and traumatic brain injury.

Pupil diameter differentiates expertise in dental radiography visual search

Expert behavior is characterized by rapid information processing abilities, dependent on more structured schemata in long-term memory designated for their domain-specific tasks. From this understanding, expertise can effectively reduce cognitive load on a domain-specific task. However, certain tasks could still evoke different gradations of load even for an expert, e.g., when having to detect subtle anomalies in dental radiographs. Our aim was to measure pupil diameter response to anomalies of varying levels of difficulty in expert and student dentists’ visual examination of panoramic radiographs. We found that students’ pupil diameter dilated significantly from baseline compared to experts, but anomaly difficulty had no effect on pupillary response. In contrast, experts’ pupil diameter responded to varying levels of anomaly difficulty, where more difficult anomalies evoked greater pupil dilation from baseline. Experts thus showed proportional pupillary response indicative of increasing cognitive load with increasingly difficult anomalies, whereas students showed pupillary response indicative of higher cognitive load for all anomalies when compared to experts.

Pregabalin Has Analgesic, Ventilatory, and Cognitive Effects in Combination with Remifentanil

Background Pregabalin is widely used perioperatively. The authors explored the effects of pregabalin, remifentanil, and their combination on experimental pain, ventilatory, and cognitive function. Methods In a randomized, double-blinded crossover study, 12 volunteers received (1) pregabalin + placebo, (2) placebo + remifentanil, (3) pregabalin + remifentanil, and (4) placebo + placebo. Pregabalin 150 mg/placebo was administered twice orally. After baseline, remifentanil/placebo was given as effect-site target-controlled infusion (TCI): 0.6, 1.2, and 2.4 ng/ml. Pain during cold pressor test was scored on visual analog scale (0 to 100 mm). Ventilation was measured by spirometry and cognition tested with Color-Word Interference and Rapid Information Processing tests. Results Pain intensity after placebo was (mean) 72 mm (95% CI, 62 to 83). Pregabalin reduced pain score by −10 mm (−14 to −7, P &lt; 0.001). Remifentanil had dose-dependent analgesic effect, reducing pain score by −47 mm (−54 to −39, P &lt; 0.001) on highest TCI level, whereas pregabalin + remifentanil exerted additive effect, reducing pain score by −57 mm (−64 to −50, P &lt; 0.001). Respiratory depression was potentiated by adding pregabalin to remifentanil; end-tidal carbon dioxide was 39.3 mmHg (37.2 to 41.3) with placebo, increased 1.8 mmHg (−0.9 to 4.6, P = 0.4) with pregabalin, 10.1 mmHg (4.9 to 15.4, P &lt; 0.001) with remifentanil, and 16.4 mmHg (11.3 to 21.5, P &lt; 0.001) with pregabalin + remifentanil on highest TCI level. The combination pregabalin + remifentanil, but not either drug alone, adversely affected all cognitive tests. Conclusions The combination of pregabalin and remifentanil had additive analgesic effects, pregabalin potentiated remifentanil ventilatory depression, and the combination adversely affected cognition. These results question the clinical benefit of the combination compared with higher doses of opioids.