Importaciones de minerales Industriales 2005

The d-prime value for each participant was calculated both for the one-back task and for the sentence verification task. In the last one the d-prime was calculated separately for pronouns and reflexives. In order to remove extreme values we used the Standard Deviation (SD) method, in other words we removed all results that were 2SD above or below mean accuracy and mean RT for each participant. Normality tests were performed before statistical analyses.

Do the three groups differ in processing pronouns and reflexives?

 D-Prime Analyses

To compare the d-prime (D’) across conditions and groups, a 2x3 mixed ANOVA considering Condition as a within subject factor (‘pronoun’ vs. ‘reflexive’) and Group as a between subject factor (HD vs. HE vs. Control) was conducted for all participants. Follow up tests were pursued when relevant interactions were identified. Greenhouse-Geisser corrections were applied when

the data did not meet the sphericity assumption. An alpha level for significance was set at p<0.05. A main effect of condition (F(1.60)=4.90, p=0.03) and a main effect of group (F(2.60)=62.14, p=0.000) were found. However, there was no interaction between Condition*Lesion (F(2.60)=2.33, p=0.11). Post hoc comparisons using the Tukey HSD test were pursued, and these revealed statistical significant differences between the LH and the RH (p=0.009) and between both patients groups and control group (LH: p=0.000; RH: p=0.000). A profile plot summarizes the results (Figure 5a & 5b).

Figure 5a & 5b: The first boxplot shows the

performance for the three groups in sentences with pronouns; the second plot show the performance for the three groups in sentences with reflexives.

 RT Analyses

A 2x3 mixed ANOVA considering Condition as a within subject factor (‘pronoun’ vs. ‘reflexive’) and Group as a between subject factor (HD vs. HE vs. Control) was also computed for all participants to compare the response time (RT) in both conditions. A main effect of condition (F(1.60)=22.00, p=0.000) and group (F(2.60)=12.69, p=0.000) were found. However, the patients groups did not significantly differ from each other. Just like in D’, there was no interaction between Condition*Lesion (F(2.60)=0.56, p=0.57). Post hoc comparisons using the Tukey HSD test indicated that the mean score for the LH and for the RH groups were significantly different than the control group (LH: p=0.001; RH: p=0.000), the patients groups didn’t differ from each other (p=0.526). A profile plot summarizes the results (Figure 6a & 6b; detailed information on table 5).

Table 5: Means and Standard Deviations for RT and D’ for pronouns and reflexives in each group

LH Group RH Group Control Group

D’ Pronouns 0.06±0.33 0.60±1.09 2.55±1.03 Reflexives 0.31±0.60 1.09±0.77 2.50±0.79 RT Pronouns 2129.48±1041.60 2348.65±967.34 1141.84±342.12 Reflexives 1840.46±1023.44 2169.83±962.29 951.88±331.39

Note: LH: left hemisphere, RH: right hemisphere, D’: d-prime, RT: response time

Figure 6a & 6b: The first boxplot shows the RTs for

the three groups in sentences with pronouns and the second plot show the RTs for the three groups in sentences with reflexives.

Do the three groups differ in their degree of WM impairment?

Because the distribution didn't meet the normality assumption, for d-prime we used a non-parametric test (Kruskall-Wallis). The Concerning the working memory test (one-back task), statistically significant differences in performance were found among the groups (K-W, χ2(2)=20.78, p=0.000). The LH and the control group were different (U=40.00, p=0.000) as well as RH and the control group (U=95.500, p=0.002); however we didn’t find differences when LH and RH groups were compared (U=193.500, p=0.497).1 _{Similar results were obtained} when we compared RT in one-back task across groups with the ANOVA test. A significant effect of RT at the p<0.05 level for the three groups (F(2,60)=6.65, p=0.002) was observed. Post hoc comparisons using the Tukey HSD test indicated that the mean score for the LH and for the RH groups were significantly different than the control group (LH: p=0.018; RH: p=0.003). However, the patients groups did not significantly differ from each other (p=0.814) (detailed information on table 6).

Table 6: Means and Standard Deviations for WM for pronouns and reflexives in each group

LH Group RH Group Control Group

D’ 2.64±0.84 2.89±1.16 3.95±0.54

RT 1178.24±359.21 1247.66±444.33 860.26±278.44

Note: LH: left hemisphere, RH: right hemisphere, D’: d-prime, RT: response time

Is there an overall correlation between WM and the processing of reflexives and pronouns, for any of the groups?

Next a correlation test was computed (Spearman) for d-prime and the RT, to determine the relationship between the one-back task and reflexives, and the one-back task and pronouns, for each group separately.

1 _{With the ANOVA test the results would be similar (F(2,60)=13.13, p=0.000). Post hoc comparisons}

using the Tukey HSD indicated that the LH and the control group were different (p=0.000) as well as RH and the control group (p=0.001); however we didn’t find differences when LH and RH groups were compared (p=0.640).

 D-Prime Analyses

For LH group no statistically significant correlation was found between one-back task for reflexives and neither for pronouns (D’ reflexives: rs(19)=0.42, p=0.06, and D’ pronouns: rs(19)=0.32, p=0.16). For the RH group, a statistically significant moderate positive correlation between D’ one-back task and was found for D’ reflexives (rs(19)=0.598, p=0.004) and for D’ pronouns (rs(19)=0.502, p=0.021). While for the control group, a significant correlation between D’ one-back task and D’ reflexives (rs(19)=0.465, p=0.034) and between D’ one-back task and D’ pronouns, (rs(19)=0.539, p=0.012) was found.

 RT Analyses

Just like in D’, for LH group no statistically significant correlation was found between the one-back task and reflexives or pronouns (RT reflexives: rs(19)=0.09, p=0.70, and pronouns: rs(19)=-0.01, p=0.97). When we analysed the RH group, we also did not find any correlation between both one-back task and reflexives (rs(19)=0.10, p=0.68) and one-back task and pronouns (rs(19)=0.24, p=0.29). Similarly to what happened to the LH and RH groups, no correlation was found neither between the RT in the one-back task and the RT for reflexives (rs(19)=-0.053, p=0.819), nor between the RT in one-back task and the RT for pronouns (rs(19)=-0.049, p=0.834).