O-LIFE UnEx 6.85 (5.94) 0 24 9.70 (6.70) CogDis 11.35 (5.66) 0 22 11.60 (5.80) IntAn 4.21 (3.41) 0 16 6.20 (4.60) PDI Total 35.42 (28.13) 0 126 58.90 (48.00) Yes 3.81 (2.86) 0 13 6.70 (4.40) Dis 9.83 (8.73) 0 40 15.50 (14.10) Con 9.23 (7.93) 0 29 15.40 (14.10) Pre 12.35 (9.81) 0 45 20.40 (16.00) LSHS-R Total 24.02 (5.23) 16 36 VivTh 5.84 (1.75) 3 10 - AudHal 5.34 (1.40) 4 9 - VivDay 5.47 (2.06) 3 11 - VisHal 7.03 (1.79) 5 11 -
97 Psychometric Measures
Mean scores for the O-SPAN, O-LIFE, PDI and LSHS-R for this sample as well as normative values (where available) can be seen in Table 2. Generally, the measures obtained from this sample are in accordance with the normative values for each measure (Mason et al., 1995; Peters et al., 2004; Unsworth et al., 2005; for O-LIFE, PDI and O-SPAN respectively). Where the measures obtained here diverge from those obtained for the normative sample, the values are still in accordance with other studies using these measures (e.g. Bradbury, Stirling, Cavill, & Parker, 2009; Elward et al., 2012; Evans et al., 2007; Jones & Fernyhough, 2009; PDI, O-SPAN, O-LIFE and LSHS-R respectively).
P
RINCIPALC
ORRELATIONS BETWEENB
EHAVIOURALM
EASURES ANDS
CHIZOTYPYReaction times, discrimination values and estimates of familiarity and recollection were correlated with schizotypy measures. When discrimination values were assessed, no reliable relationships were identified. However, analysis of reaction times revealed several positive correlations with the UnEx dimension of the O-LIFE, as well as a correlation with LSHS-R Total and one which approached significance (Table 3). Focusing on reaction times to imagine targets only, further analysis of the LSHS-R subscales revealed no significant correlations. Finally, analysis of estimates of familiarity and recollection revealed a significant negative correlation between estimates of familiarity for perceive items and PDI Total (r(46)=-0.29,p=0.043).
Table 3 – Correlations between schizotypy measures and reaction times to correct responses to targets, non-targets and new items split by target designation (imagine/perceive) from Experiment One. *p<0.05, **p<0.01, † p<0.1. Correlations have not been corrected for multiple comparisons refer to Sensitivity Issues (page 192) for discussion.
O-LIFE PDI LSHS-R
Reaction Times UnEx CogDis IntAn Total Total
Imagine Target 0.44 ** 0.07 -0.05 0.22 0.33 * Non-Target 0.26 0.13 -0.07 -0.04 0.17 New 0.29.* -0.02 -0.19 0.17 0.18 Perceive Target 0.29 * 0.00 -0.04 0.17 0.28 † Non-Target 0.26 -0.13 -0.15 0.13 0.26 † New 0.15 -0.13 -0.26 0.14 0.19
98 Figure 3 – Topographic maps showing old/new effects for targets and non-targets split by target designation (imagine/perceive) from Experiment One for the 500-800ms epoch. The maps were computed from difference scores obtained by subtracting mean amplitudes for correct responses to new items from those associated with targets and non-targets respectively. ERP waveforms are from electrodes included in the left-parietal old/new effect analysis.
PERCEIVE
Target – New Non-Target – New Target – New Non-Target – New
IMAGINE
IMAGINE
PERCEIVE
Target Non-Target New Target Non-Target New99
P
RINCIPALERPR
ESULTSMean amplitudes were calculated for epochs of interest and separated according to trial type and target designation. The mean numbers of trials (range in parentheses) contributing to each condition of interest were as follows: imagine target = 40 (25-60), perceive target = 39 (18-56), imagine non-target = 43 (22-58), perceive non-target = 40 (16-57), imagine new = 43 (18-59) and perceive new = 47 (17-60).
Left-Parietal Old/New Effects
As can be seen in Figure 3 there is a positive deflection in the EEG recording reaching maximal amplitude from 500-800ms post-stimulus presentation. This effect is largest at left-parietal electrode sites and is more positive going for old items (targets and non- targets) compared to new items. An initial ANOVA with factors of target designation (two levels; imagine and perceive), response category (three levels; correct responses to target, non-target and new items), hemisphere (two levels; left and right) and site (three levels; inferior [P7/8], medial [P5/6] and superior [P3/4]) was conducted. This analysis revealed significant main effects of response category (F(2.0, 92.4)=23.49,p<0.0001,E=0.98) as well as significant interactions between response category and hemisphere (F(1.6, 73.3)=18.16,p<0.0001,E=0.78) and response category and site(F(2.2, 103.9)=4.95,p=0.007,E=0.55). The interaction with site reflects the fact that the ERP old/new effects are largest at superior locations. Planned follow-ups on the interaction between response category and hemisphere revealed that over the left hemisphere ERP amplitudes to target items were more positive going than those to non- target and new items; and non-target items were more positive going than new items (smallest t(47)=3.70,p<0.001). Over the right hemisphere planned comparisons revealed that ERP amplitudes to target items were more positive going than non-target and new items (smallest t(47)=3.99,p<0.0001), but there were no reliable differences between non-target and new items.
100 Table 4 – Mean numbers of target, non-target and new items split by target designation (imagine/perceive) free recalled in Experiment One. Standard deviation (SD) are in parentheses.
Free Recall Imagine (SD) Perceive (SD)
Target 11.52 (4.29) 11.58 (5.00)
Non-Target 10.27 (4.07) 11.50 (4.23)
New 5.69 (3.19) 4.75 (3.49)
P
RINCIPALC
ORRELATIONSB
ETWEENERPM
EASURES ANDS
CHIZOTYPYThe magnitude differences between the ERPs associated with correct responses to targets and non-targets for both the perceive and imagine target designations were calculated. These measures were averaged across the P7, P5 and P3 electrode sites within the 500-800ms epoch. Magnitude differences were calculated by subtracting the mean ERP amplitude for non-target items from the mean ERP amplitude for target items. The differences measures were then entered into correlation analyses with the schizotypy measures. No reliable relationships were identified between any of the aforementioned variables.
S
UBSIDIARYB
EHAVIOURALR
ESULTSHaving established reliable attenuations of non-target compared to target left-parietal old/new effects, free recall performance was analysed to investigate if changes in the left-parietal old/new effects influenced the subsequent memorability of the test items. The mean numbers of items recalled from each response category, split by target designation are presented in Table 4. A 3x2 repeated measures ANOVA with factors of target designation and response category revealed a significant main effect of response category only (F(1.9, 90.4)=74.30,p<0.001). Free recall of target and non-target items was significantly greater than new items, but there was no significant difference between the number of target and non-target items recalled (smallest t(47)=7.80,p<0.001).
101
Pe
rceive
Imagine
Figure 4 – Topographic maps showing old/new effects for targets and non-targets split by target designation (imagine/perceive) for Experiment One for three epochs between 900 and 1800ms. The maps were computed from difference scores obtained by subtracting mean amplitudes for correct responses to new items from those associated with targets and non-targets respectively.
102
S
UBSIDIARYERPR
ESULTSLate Posterior Negativity
As can be seen in the waveforms and scalp maps in Figure 4 and Figure 5, a late posterior
negativity emerges from approximately 900ms post-stimulus presentation and appears more negative going for imagine items. Initial ANOVAs with the factors of target designation (two levels; imagine and perceive) and response category (three levels; correct responses to target, non-target and new items) and site (three levels; P3, Pz and P4) were conducted across three epochs (900-1200ms, 1200-1500ms, 1500-1800ms). In the first two epochs there were interactions between target designation and response