The Legacy of Henry Molaison (1926-2008) and the Impact of his Bilateral Mesial Surgery on the Study of Human Rimal Hanif MD; Symeon Missios MD; Anil Nanda MD, FACS Louisiana State University Health Sciences Center, Shreveport LA

Introduction Results Figure 1 Figure 3 In 1953, neurosurgeon William Prior to Molaison’s operation, human Beecher Scoville performed a bilateral memory was believed to be a global cerebral process. To the contrary, mesial temporal lobe resection on neuropsychological studies performed on Henry Molaison, who suffered from Molaison proved that human memory is . The operation was novel as a comprised of separate processes, each with treatment for epilepsy and had an its own neurological origin. For example, unexpected consequence: a severe although Molaison’s ability to form new compromise of Molaison’s anterograde was severely impaired, studies memory. In a landmark 1957 showed that his personality and cognition publication, Scoville and Brenda were normal, and he retained the ability to Milner, a cognitive neuroscientist who William Beecher Scoville, left, and Brenda acquire new motor skills. After his death in 2008, Molaison’s brain underwent detailed had previously collaborated with well- Milner, right MRI scanning and was subsequently sliced known epilepsy neurosurgeon Wilder Figure 2 into 2,401 sections. Histological evaluation Penfield, concluded that mesial of Molaison’s brain further elucidated which temporal lobe structures, particularly mesial temporal lobe structures were the hippocampi, were integral to the preserved or resected in his operation, formation of new, recent memories. shedding new light on the neuroanatomic underpinnings of short-term memory.

Methods Scoville's cross-sectional illustrations Conclusions depicting his attempted bilateal mesial A detailed literature review was Scoville regretted Molaison’s surgical temporal lobe resection (only one side performed to obtain details of outcome and spoke vigorously about the demonstrated for diagrammatic purposes) Molaison's operation and of his dangers of bilateral mesial temporal lobe surgery. Now, during the planning of a contributions to neuroscience and unilateral temporal lobectomy, . neurosurgeons ensure the integrity of the contralateral using various diagnostic studies, such as the Wada test Learning Objectives and functional MRI. This report is the first 1. Recognize that neurosurgeon historical account of Molaison’s case in the William Scoville's bilateral mesial neurosurgical literature, serving as a temporal lobe resection on Henry reminder of Molaison’s contributions and of Molaison rendered him profoundly the perils of bilateral mesial temporal lobe amnesic surgery. Henry Molaison in Hartford, CT, in 1975 2. Learn about the contributions of Henry Molaison to cognitive neuroscience through his participation in neuropsychological studies for over four decades

3. Caution neurosurgeons regarding the dangers of bilateral mesial temporal lobe injury to short-term memory formation