**3.5. Confounding effects**

baseline MFV in dark condition was higher in LMCA than R-MCA, and Paradigms 1–5 induced significantly greater attenuation of MFV in the RMCA (p < 0.05) than in the L-MCA (p < 0.001). As a result, there was left lateralization for all Paradigms 1-5 (Figure 7B). There was no difference between Paradigm 2 and Paradigm 3. In other words, in women, stimulus-specific effects did not yield lateralization of MFV. Given the observed marginal tendencies for changes between Paradigms 1-3, the *f*TCDS analysis was carried out for dark and Paradigms 1-3 effects.

The spectral density plots for each artery during all study conditions in Figures 8 A-D, in men

**Figure 8.** A-D). Shows the plots of spectral density estimates for dark, object (Paradigm 1) and facial (Paradigms 2-3) stimulation for the RMCA in men (Figure 8A), for the LMCA in men (Figure 8B); for the RMCA in women (Figure 8C)

In general, for all stimulations in both men and women there were three peaks designated as **F**-, **C**-, and **S**-peaks, representing the fundamental, cortical, and subcortical peaks, which occurred at regular frequency intervals of 0.125, 0.25, and 0.375, respectively. The spectral density peaks were analyzed for each gender separately to examine the effect of dark and stimulations at **C**- and **S**-peaks for the RMCA and LMCA, respectively. A one-way ANOVA with repeated measures for all four levels of STIMULATION (Dark, Paradigms 1-3) was used. This was followed by planned contrasts. In men, in the RMCA at C-peaks, there was a main effect of STIMULATION, F(3, 18) =4.2, MSE= 16804.3, p=0.05. Planned contrast revealed a category-specific face effect, p = 0.05, (Figure 8A). However, at the S-peaks there was only a

and LMCA in women (Figure 8D). (Source modified from: Njemanze PC. Laterality 2007, 12:31-49.).

**3.4. Gender-related asymmetry during facial processing by** *f***TCDS**

(Figure 8 A-B) and women (Figure 8 C-D), respectively.

156 Advancements and Breakthroughs in Ultrasound Imaging

The cardiovascular measures that could cause confounding effects were assessed using oneway analysis of variance (ANOVA). In men the heart rate during Paradigm 1 (71.9±10.6 bpm), Paradigm 2 (69.6±11 bpm), and Paradigm 3 (70.5±5 bpm) did not differ from resting baseline (67.5±9 bpm), (p = 0.05). Similarly, in women the heart rate during Paradigm 1 (76.9±9.8 bpm), Paradigm 2 (78.9±12 bpm), and Paradigm 3 (79.3±13.8 bpm) did not differ from resting baseline (76.9±9.6 bpm), (p = 0.05). In men the respiratory rate during Paradigm 1 (17.3±3.5 per minute), Paradigm 2 (19.9±5.7 per minute), and Paradigm 3 (16.9±3.7 per minute) did not differ from resting baseline (17.9±2.5 per minute), (p=0.05). Similarly, in women the respiratory rate during Paradigm 1 (19±4.5 per minute), Paradigm 2 (21±5 per minute), and Paradigm 3 (21±6 per minute) did not differ from resting baseline (19.3±6.4 per minute), (p > 0.05). The overall mean heart rate was 74 bpm and respiratory rate was 19 per minute. There was no significant difference between pre-test and post-test blood pressure, (p > 0.05). Similarly, there were no significant differences between the stimuli for heart rate, respiratory rate, and anxiety scores (p > 0.05). In other words, there were no changes in cardiovascular parameters and anxiety scores during the study. In post-test debriefings, participants described their initial condition as ''blank'', unaware of subtle emotional state, as they tried to focus attention on the imagery spot within the dark visual field. Women described the paradigms in greater detail than men. For example, on first prompt for description, most men described Paradigm 1 simply as a draught board or chess board, while most women described it as alternating black and white squares within a cube. For execution of Paradigm 3, both men and women reported sorting one part of the face at a time into place before proceeding to the next part, in other words, all followed a step-by-step approach. All rated themselves as not being anxious, and assessed themselves as having good performance, with no difficulty with task execution.
