Cortical and Autonomic Stress Responses in Adults with High Versus Low Levels of Trait Anxiety: A Pilot Study.

Stress responses are mediated by complex patterns of cortical and autonomic activity. Earlier studies showed increased recruitment of the right prefrontal cortex (PFC) and parasympathetic withdrawal during a stress task; however, it remains unclear whether these responses change in relation to different levels of psychopathological symptoms, such as trait anxiety. The present study examines the effect of a mathematical task (with a control condition and a stressful/experimental condition) on the PFC and autonomic activity, using a two-channel near infrared spectroscopy (NIRS) and an ECG monitoring system. After a preliminary screening of 65 subjects, a sample of 12 individuals (6 with the highest and 6 with the lowest scores on an anxiety questionnaire, i.e. the STAI trait) was selected. The two groups were similar regarding demographic variables (age, sex, body mass index) and baseline STAI-state scores. Repeated measures ANOVAs were used to compare changes from baseline in oxyhemoglobin (oxy-Hb), heart rate (HR) and root mean square of successive differences (RMSSD) between the two groups. Individuals affected by high levels of trait anxiety showed a reduced bilateral PFC activity during the entire experimental procedure compared to those with low anxiety. No differences in NIRS channels were found between the two groups. During both conditions, RMSSD was lower among individuals affected by high levels of anxious symptoms. Finally, throughout the procedure, changes in HR were higher in the anxious group. Overall, these findings suggest a reduced PFC activity and a larger parasympathetic withdrawal during a stress task in individuals with high levels of trait anxiety compared to those with low anxiety. These results could represent a starting point for future NIRS and ECG studies on the relationship between mental disorders and acute stress responses.

Age-Related Changes in Physiological Reactivity to a Stress Task: A Near-Infrared Spectroscopy Study.

Aging is associated with changes in biological functions, such as reduced cardiovascular responses to stressful tasks. However, less is known about the influence of age on the reactivity of the prefrontal cortex (PFC) to acute stressors. Therefore, this study aimed to investigate the effects of a computerized-controlled stress task on the PFC and autonomic system activity in a sample of older and younger adults. We recruited a total of 55 healthy, right-handed persons (26 older adults with mean age 69.5, SD 5.8 years; and 29 younger adults with mean age 23.8, SD 3.3 years); groups were balanced for sex. Tasks included a control and an experimental condition: during both tasks individuals had to solve simple mental arithmetic problems. For the experimental condition, all participants were faced with a time limit that induced significant stress. Physiological indexes were collected continuously during the entire procedure using a 2-channel near infrared spectroscopy (NIRS) and an ECG monitoring system. Repeated measures ANOVA were used to assess changes in hemoglobin concentrations, and changes in both heart rate and performance outcomes. NIRS, ECG and performance data showed a significant interaction between the group and condition. Post-hoc analyses evidenced a significant increase in heart rate and Oxy-Hb concentration in the bilateral PFC between the control and experimental condition only in the younger group. Post-hoc analyses of behavioral data showed lower percentages of correct responses and higher response times in the older group. In summary, these results suggested that cardiovascular and cortical reactivity to stress tasks are a function of age. Older individuals seem to be characterized by blunted physiological reactivity, suggestive of impaired adaptive responses to acute stressors. Therefore, future studies should investigate the underlying physiological mechanisms of prefrontal and cardiovascular changes related to aging.

Effects of Positive and Negative Mood Induction on the Prefrontal Cortex Activity Measured by Near Infrared Spectroscopy.

The neurophysiological mechanism of positive versus negative emotions is insufficiently understood. In the present study, we examined the effect of event recall tasks on the prefrontal cortex (PFC) activity using near infrared spectroscopy (NIRS). Nine healthy adults were instructed to recall episodes of their life associated with positive (happiness) and negative (anger) emotion, both silently and verbally. Heart rate (HR) changes were simultaneously measured. NIRS showed an increased oxyhemoglobin (oxy-Hb) in the bilateral PFC during silent and verbal recall of both positive and negative episodes. The changes of oxy-Hb in the bilateral PFC during silent recall of negative episodes were significantly larger than those during silent recall of positive episodes (p < 0.01). There was no difference in average changes of oxy-Hb between silent and verbal recall of negative episodes (p > 0.95), while changes of oxy-Hb during verbal recall of positive episodes were larger than those during silent recall of positive episodes (p < 0.05). Both verbal and silent recall of positive and negative episodes increased HR; however, verbal recall caused larger increases of HR than silent recall (p < 0.01). The present results suggest that recall of negative episodes affect the PFC activity, which plays a key role in cognitive control of emotions, more than positive episodes.

C1 and P1 visual responses to words are enhanced by attention to orthographic vs. lexical properties.

Attention to word orthographic properties has been shown to enhance the activity of VWFA. The temporal resolution of this effect remains still uncertain. In this study the attentive processing of orthographic vs. semantic features was compared by presenting the same set of words in two different conditions: letter detection vs. lexical decision. ERPs to targets were recorded in thirty-two right-handed students from 128 scalp sites. RTs, ERPs and swLORETA source reconstruction showed the prioritized processing of word orthographic features, able to enhance the activity of left fusiform gyrus (BA19/37) and cerebellar structures as early as 70-90 ms from stimulus-onset, as reflected by the increased amplitude of mesial C1 and lateral-occipital P1 components. On the other hand, attention to word lexical properties strongly enhanced the amplitude of left occipito/temporal N170, whose neural generators seemed to include regions devoted to lexical processing (VWFA), semantic processing (left BA39), and the effortful retrieval of semantic information (left and right BA10).