In many literature reviews, limitations of collective or single studies can be pointed out and “spread out” over the whole section. This helps reinforce the overall argument that there are gaps which need to be filled and to hint at the need for the present study. A summative “gap” statement can be given in the last subsection of a literature review before introducing the present study, although this is not always the case.
Here is an example from a journal article in the field of psychology. This study explores relationships between diverse characteristics of visual attention (e.g., sustained attention, divided attention, attentional orienting, and selective attention) and flying ability:
From this … review, it is clear that more research is needed to identify if and how tests of attentional ability should be used to predict flight training success and operational performance. This conclusion is further supported by the fact that although attention-related tests have been used in some aviation tests batteries, the development of these batteries remains hampered by poor prediction success with correlations between test scores and flight training success ranging between 0.2 and 0.4 (references) (Gray et al., 2016).