Construct Validity of Material-Specific Memory Measures Following Unilateral Temporal Lobe Ablations

Material-specific memory test performance of 18 left (LTL), and 11 right (RTL), unilateral temporal lobectomy patients was assessed pre- and 1 wk postsurgery. Selective Reminding and Serial Digit Learning tests were the verbal, and Complex Figure and Form Sequence Learning tests were the nonverbal, learning measures. Following surgery, LTLs showed significant reductions on both verbal memory tests, but no significant decline was observed in RTLs on the nonverbal memory measures' summary scores. Results suggest that Selective Reminding and Serial Digit Learning tests are sensitive to left temporal lesions but that Complex Figure and Form Sequence Learning tests, and by extension other nonverbal learning tests, should be interpreted cautiously with respect to unilateral temporal lobe dysfunction. Reasons for the difficulty in finding "pure" measures of visual learning are discussed, and suggestions for future nonverbal memory test development are presented.