: studying words that fit a common schema (e.g., cold, blizzard, winter) often produces memory for a nonstudied word (e.g., snow). We propose that frontal lobe regions that contribute to complex decision-making processes by weighting various alternatives, such as ventromedial prefrontal cortex (vmPFC), may also contribute to memory processes by weighting the influence of schematic knowledge. We investigated the role of human vmPFC in false memory by combining a neuropsychological approach with the DRM task. Patients with vmPFC lesions (n ϭ 7) and healthy comparison participants (n ϭ 14) studied word lists that excluded a common associate (the critical item). Recall and recognition tests revealed expected high levels of false recall and recognition of critical items by healthy participants. In contrast, vmPFC patients showed consistently reduced false recall, with significantly fewer intrusions of critical items. False recognition was also marginally reduced among vmPFC patients. Our findings suggest that vmPFC increases the influence of schematically congruent memories, a contribution that may be related to the role of the vmPFC in decision making. These novel neuropsychological results highlight a role for the vmPFC as part of a memory network including the medial temporal lobes and hippocampus (Andrews-Hanna et al., 2010).

Schemas, as memory representations of typical contexts, allow for generalization from previous experiences while often improving memory organization and accuracy. However, these advantageous characteristics of schematic memory may come at the cost of episodespecific information. In the human brain, this tradeoff between general and specific knowledge has been linked to differential contributions of the medial temporal lobes (MTL) to episode-specific memory and the ventromedial prefrontal cortex (vmPFC) to generalized, schematic memory. Here, we used a neuropsychological approach to test whether participants with focal vmPFC damage (n ϭ 6) would show a reduced influence of schematic memory relative to healthy normal comparison participants (n ϭ 12) in a recognition task that presented schematically congruent or incongruent contexts at study. As predicted, normal comparison participants were more likely to identify items as old after studying them in congruent contexts, and this effect was reflected in increased true and false recognition. These effects of prior context on recognition were not observed in the vmPFC group, suggesting that vmPFC damage reduced the influence of schematic memory. These findings are consistent with the proposition that the vmPFC plays an important role in integrating previous experience into ongoing memory processes while acting as part of a larger memory network.

Brain retraction systems are frequently required to achieve surgical exposure of deep-seated brain lesions. Retraction, however, is associated with complications that include brain edema, vascular compromise causing ischemia, and direct damage to surrounding cortex. 27 The frequency of retraction-based injury has been estimated to be approximately 10% in skull base surgery and 5% in intracranial aneurysm operations. 4 Techniques such as intermittent retraction, 24 endonasal trajectories, 3,6,10,17 and those that use tubular retractors 1,2,7,9,[11][12][13][14][15][16][18][19][20][21][22][23]25 have been used to minimize these injuries.Previously, we reported the successful use of a METRx spinal tubular retractor system, paired with the Brainlab frameless navigation system, for resection of deep-seated intracranial lesions. 9 The advantages of this tubular retractor system include equal distribution of retraction pressure abbreviatioNs ADC = apparent diffusion coefficient; DWI = diffusion-weighted imaging; GTR = gross-total resection; NTR = near-total resection; STR = subtotal resection. obJective Brain retraction systems are frequently required to achieve surgical exposure of deep-seated brain lesions. Spatula-based systems can be associated with injury to the cortex and deep white matter, particularly adjacent to the sharp edges, which can result in uneven pressure on the parenchyma over the course of a long operation. The use of tubular retractor systems has been proposed as a method to overcome these limitations. There have been no studies assessing the degree of brain injury associated with the use of tubular retractors. methods Twenty patients were retrospectively identified at Weill Cornell Medical College who underwent resection of deep-seated brain lesions between 2005 and 2014 with the aid of a METRx tubular retractor system. Using the Brainlab software, pre- and postoperative images were analyzed to assess volume, depth, extent of resection, and change in postoperative MR FLAIR hyperintensity and restricted diffusion on diffusion-weighted imaging (DWI). results The mean preoperative tumor volume was 16.25 ± 17.6 cm 3 . Gross-total resection was achieved in 75%, near-total resection in 10%, and subtotal resection in 15% of patients. There was a small but not statistically significant increase in average FLAIR hyperintensity volume by 3.25 ± 10.51 cm 3 (p = 0.16). The average postoperative volume of DWI high signal area with restricted diffusion on apparent diffusion coefficient maps was 8.35 ± 3.05 cm 3 . Assuming that the volume of restricted diffusion on DWI around tumor was 0 preoperatively, this represented a statistically significant increase on DWI (p < 0.001). coNclusioNs Although tubular retractors do not appear to significantly increase FLAIR signal in the brain, DWI intensity around the retractors can be identified. These data indicate that although tubular retractors may minimize damage to surrounding tissues, they still cause cytotoxic edema and cellular damage. Objective comparison against o...