Mechanisms underlying Objective Memory Deficits in Pregnancy

Three mechanisms were proposed to underlie memory deficits in pregnancy. Overall, the pattern of experimental results failed to support any of these.

Inefficient self-initiated retrieval. The present results did not support the notion of inefficient SIRP (Craik, 1986) in pregnancy. This finding assumes that the typicality manipulation used in the prospective memory task reflects changes in the demand on self-initiated retrieval, a case that was supported by the finding that performance declined with decreasing typicality. Thus, the failure to find any pregnancy-related deficits on the prospective memory task, especially the atypical condition, suggests that such processes were not disrupted during pregnancy.

This is the first study to assess SIRP and prospective memory during pregnancy. Although it finds no evidence for a deficit on one type of prospective memory task (event-based, short-term), the possibility exists that deficits might occur on long-term or time-based tasks (Morris, 1984). These and other objective tests may be more sensitive to a disruption of SIRP or a prospective memory deficit in pregnancy.

Inefficient working memory. The results failed to support the possibility of inefficient working memory in pregnancy. There was no evidence of such deficits, despite using a complex condition that taxed working memory resources. The present study suggests that pregnancy should not affect women’s ability to simultaneously process and store information in complex cognitive tasks involving working memory, particularly in comprehension. Although no other studies have reported on reading span performance in pregnant women, there is mixed evidence for a deficit on backward digit span in pregnancy (P.Casey, personal communication, October 22, 1998). Thus, despite finding no evidence for a deficit on a verbal measure of working memory', this does not rule out the possibility that a deficit might be found on non­ verbal measures. In fact, non-verbal measures may reflect different aspects of working memory, and perhaps these aspects are more sensitive to a deficit in pregnancy (see Jurden, 1995).

Content specificity effect. There was some support for a content specificity

effect in pregnancy. Evidence from the working memory test indicated that the performance of pregnant women was modified by the content of the material such that they performed marginally better on pregnancy-related material, and marginally worse on non-pregnancy material. Although this interaction effect was only significant on the total WM score, a similar pattern was found on a more traditional measure resembling reading span. However, results for the recognition test did not show a content specificity effect in pregnancy. In this task, pregnant women showed better overall memory, rather than a memory bias specific to pregnancy-related words.

The only two studies investigating content specificity in pregnancy have found inconsistent evidence for this hypothesis. It has been found on some tests (recognition test - Christensen et al., in press; working memory test - present study), but not others (dot-probe attention test - Christensen et al., in press; recognition test - present study). Furthermore, the two studies show conflicting results on similar (but not identical) recognition tests, with the present study failing to find an effect. This may have been due to the fact that differences in false alarm rates were taken into account in the present study. However, the failure to find a content specificity effect in the present study is most likely a result of a ceiling effect as performance on the pregnancy-related material was almost perfect in pregnant women. Although the notion of a content specificity effect has not been disconfirmed by these results, there does not seem to be sufficient data on the content specificity effect to draw any definite conclusions about its role in memory changes in pregnancy.

Despite the lack of evidence for content specificity, the idea that memory deficits in pregnancy may be related to selectively focussing on pregnancy-related activities is compelling. Further research could be undertaken to investigate whether a content specificity effect is present on more difficult cognitive tests, particularly ones that are not susceptible to a ceiling effect. Such studies might employ free recall tests, which are less likely to show a ceiling effect and may be more sensitive to a content specificity effect than are recognition tests. It has been noted that recognition tests may be less sensitive because there are sufficient alternative cues available that may override the use of a weaker pregnancy-related cue (Williams et al., 1988).

However, previous pregnancy-memory studies have found little evidence of an objective deficit on free recall tests involving ‘neutral’ material, although the content has not been manipulated to include pregnancy-related material (Brindle et ah, 1991; Christensen et ah, in press).

Another possibility for further research would be to study performance on divided-attention tests since these are both difficult and can detect subtle changes in performance. These tasks could also be used to investigate changes in attention that occur when pregnancy-related or -unrelated material is presented. For example, performance on a primary task (such as monitoring a stream of digits to be labelled as odd or even) may become impaired in pregnancy when a secondary task is pregnancy-related as opposed to being neutral. Pregnant women would be expected to divert their attention to the pregnancy-related task, thus interfering with their performance on the primary task.

7.3 Relationships between Memory Deficits and Depression, Anxiety, and