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Sergio Meneses Ortega, M.Sc.

The Neurophysiology of Attention

Laboratory Director: Sergio Meneses Ortega, M.A.
e-mail: smeneses@cencar.udg.mx

The main purpose of the research projects conducted in this laboratory is to determine the cerebral structures and neurophysiological mechanisms involved in attention processes. To this end, we record the electrical activity of the brains of healthy human subjects while they execute tasks designed to evaluate several aspects of attention. In addition, we have studied the way in which the level of alertness modulates the processing of auditory stimuli. In this case, we record the electrical activity in the brain generated by the presentation of auditory stimuli, during wakefulness and all sleep phases. While we have discovered that the automatic detection of infrequent stimuli is present in all phases of sleep, this effect is reflected in different components of the potentials related to events. This suggests that different brain structures may be involved in the processes of automatic stimuli detection, and that said structures are activated differentially according to the state in which the organism is found. We are currently carrying out various projects in an effort to determine whether or not these changes are present in the early components of the potentials related to events and if such variation is associated with cortisol levels that are recorded throughout the day. The parameters obtained in healthy subjects have allowed us to identify the alterations in attention that manifest themselves in patients with a variety of psychiatric or behavioral disturbances. In this regard, we have studied the performance of children diagnosed with attention deficit syndrome in tasks that evaluate diverse aspects of attention. Also, we have evaluated certain alterations of attention that occur in schizophrenic patients, both those in acute phases and those who are in remission, the cognitive deficits seen in patients with severe depression, and the effects of treatment with antidepressants. Finally, for the purpose of studying the neurochemical mechanisms involved in detecting or discriminating auditory stimuli, we developed an animal model based on procedures derived from the experimental analysis of behavior, in which water-deprived rats can obtain this liquid through a form of reinforcement if they adequately perform detection or discrimination tasks involving auditory stimuli. Once the animals develop the ability to perform the task at a high level, electrodes are implanted in different regions of their brains in order to determine the cerebral electrical activity associated with the processes of detecting and discriminating significant stimuli. Finally, we have injected GABA into the prefrontal cortex and a variety of cholinergic antagonists into the thalamic regions, and proceeded to evaluate their effect on the execution of a detection task of auditory stimuli. This model has also made it possible to evaluate the effect of lead poisoning on the processes of detecting and discriminating stimuli.