Word Memory Test profiles in two cases with surgical removal of the left anterior hippocampus and parahippocampal gyrus.

In Press, Dec. 2012, Applied NeuropsychologyCarone, D., Green, P. and Drane, D.

Abstract
One principle underlying the use of the Word Memory Test (WMT) as an effort test is that, with good effort, recognition scores above the cut-offs will be observed. However, in order to understand the limits of effort testing, it is necessary to study people known to have severe impairment and significant neuropathology involving memory structures. Goodrich-Hunsaker and Hopkins (2009) reported that three amnesic patients with bilateral hippocampal damage had severely impaired free recall of the WMT word list but passed the recognition subtests of the WMT, which are often called effort subtests. We tested two patients with surgical resections in the left anterior temporal region to treat chronic intractable epilepsy, both of whom suffered post-operative strokes. Patient A was a 15 year-old boy and Patient B was a 58 year-old woman. Despite destruction of the left anterior hippocampus and the parahippocampal gyrus and despite impairment of Free Recall, both cases passed the easy WMT effort subtests. These data reinforce previous findings that people with severe impairment of free recall will score much higher on the verbal recognition memory subtests than on the more difficult memory subtests. Even severe memory impairment and/or removal of hippocampal areas does not necessarily lead to failure on the easy WMT recognition subtests.

Keywords: effort; word memory test; left temporal lobe epilepsy; hippocampus;

  1. Dominic A. Carone, Ph.D., ABPP-CN, Neuropsychologist and Clinical Assistant Professor (PM&R & Psychiatry), SUNY Upstate Medical University, Syracuse, NY
  2. Paul Green, Ph.D., Private Practice, Edmonton, Alberta, Canada
  3. Daniel L. Drane, Ph.D., Assistant Professor of Neurology, Emory University School of Medicine, Atlanta, Georgia

Disclaimer:  Paul Green is the author of the Word Memory Test. Neither Dominic Carone nor Daniel Drane has any financial interest in the WMT or any other products of Green’s Publishing.

COMMENT:-
Traditionally, the hippocampus has been considered essential to episodic memory and the left hippocampus is usually thought of as the basis of verbal learning and memory. Thank you Brenda Milner and many others. In this paper, we report on two cases in whom the left anterior hippocampus was removed, as well as the parahippocampal gyrus. Both cases passed the WMT recognition memory subtests (IR and DR) but had impaired Free Recall. Clearly, recognition memory of this type is a very different animal from what we usually think of as memory (e.g. free recall of information). We might ask what part of the brain has to be removed to lead to failure of the WMT in people who are motivated to do well? The paper leads us to contrast those with hippocampal damage who pass the WMT with cases of mild TBI and a compensation incentive who fail it.