Autonomic functioning and brain activation during a categorization stimuli paradigm in moderate to severe TBI and psychophysiological correlates during social cognition performance

Abstract

Existing research has not identified the neurophysiological and psychophysiological substrates of categorization and how moderate to severe ΤΒΙ might affect the underlying psychophysiology and brain activity during high level classification activities. Similarly, research has not identified the effects of TBI on autonomic nervous system responses during the performance of Emotion Perception (EP) tasks. The present study aims to address the above two shortcomings and advance the state of the art in TBI research. Concurrently, it attempts to investigate the relationship between EP and neurocognitive performance. One of the main aims of the present research project was to compare brain activity, as measured by functional near-infrared spectroscopy (fNIRS), in people with moderate to severe TBI and age-matched control group, when performing cognitive tasks from a computerized new category learning paradigm. The second purpose of this research work was to investigate the psychophysiological reactions and more specifically the heart rate (HR) and the galvanic skin response (GSR), that were used as indicators of sustained attention, during those cognitive tasks. Α third purpose of this dissertation was to investigate sustained attention through psychophysiological indices in individuals with moderate to severe TBI and in non-injured controls during the performance of an EP battery. The relationship between EP and psychophysiological reactions, as measured by heart rate and skin galvanic response, was also explored. The last objective was to examine the relationship between EP and Neurocognitive Functions. The results of the present study showed significant differences between the two groups in cerebral blood flow during the three new rule categorization tasks, that were progressed in difficulty. The results of the present dissertation suggest that fNIRS could be a useful, safe, tolerant to human body movements and a highly portable assessment tool that can be easily used to assess brain activation and contribute to the progress of the current approaches for the identification of biomarkers that can be used to measure TBI neuropathology and progression. Among other findings, this research showed that the group of people with TBI, in addition to lower performance and longer completion times, in most EP tasks, presents significantly lower electrodermal conductivity compared to the control group. The findings of this study support that TBI survivors exhibit lower levels of electrodermal conductivity that remained at lower levels than those of the control group, a finding that reveals that the specific population is characterized by a. lower rates of stimulation of the Autonomic Nervous System, which remain relatively stable and b. they do not follow the pattern of the control group, indicating poor sustained attention, which may contribute to difficulties in performance and processing speed, and to the use of ineffective strategies in tests of EP. Furthermore, the present research findings showed that the Executive Functions and Verbal Memory are not only related to emotion recognition, but they are also predictive of emotion recognition through face and sound.