Using human brain lesions to infer function: a relic from a past era in the fMRI age?

Abstract

Recent technological advances, such as functional imaging techniques, allow neuroscientists to measure and localize brain activity in healthy individuals. These techniques avoid many of the limitations of the traditional method for inferring brain function, which relies on examining patients with brain lesions. This has fueled the zeitgeist that the classical lesion method is an inferior and perhaps obsolescent technique. However, although the lesion method has important weaknesses, we argue that it complements the newer activation methods (and their weaknesses). Furthermore, recent developments can address many of the criticisms of the lesion method. Patients with brain lesions provide a unique window into brain function, and this approach will fill an important niche in future research.

Motor versus body awareness: Voxel-based lesion analysis in anosognosia for hemiplegia and somatoparaphrenia following right hemisphere stroke

“…In addition to intrinsic limitations of lesion mapping studies (Rorden, Fridriksson, & Karnath, 2009;Rorden & Karnath, 2004), part of the aforementioned differences between studies may be attributed to different sample sizes and selection criteria, including criteria for diagnosis, subtype of anosognosia, age, lesion size, perfusion patterns, white matter involvement, and the time interval since stroke for both diagnosis and neuroimaging examination (Karnath et al, 2005;Kortte et al, 2015;Vocat et al, 2010). Unfortunately, addressing all these limitations in a single study is currently unfeasible for most labs.…”

“…Taken together, the conflicting results of previous studies, as well as the frequent co-occurrence of AHP and DSO, warrant a specific examination of the relation between DSO and AHP. In the current study we used a voxelbased, lesion comparison approach (Kimberg, Coslett, & Schwartz, 2007;Rorden & Karnath, 2004;Rorden, Karnath, & Bonilha, 2007) to test the hypothesis that at least partially segregated networks are damaged in AHP and DSO, involving more cortical premotor and insular grey matter areas in the former, and subcortical white and grey matter structures (basal ganglia and white matter tracts around them) in the latter. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 Based on these assessments, patients were categorized into four different groups: 1.…”

Thresholding lesion overlap difference maps: Application to category-related naming and recognition deficits

“…Behavioral measures are treated dichotomously when the hypothesis is that a region is critical for normal function. In related work, Karnath, Rorden and colleagues (Karnath et al, 2004;Rorden and Karnath, 2004) recently demonstrated voxelwise chi-square tests for the significant association of lesion and deficit. They also developed Voxel-based Analysis of Lesions (VAL) for analyzing dichotomized behavioral and lesion measures while covarying for lesion size or other covariates with logistic regression.…”

“…The same alpha threshold was used in the logistic regression in Karnath et al (2004). It is important to acknowledge that the method proposed here does not include a suitable solution to correct for the problem of multiple comparisons that result from multiple voxel analysis.…”

“…It is important to acknowledge that the method proposed here does not include a suitable solution to correct for the problem of multiple comparisons that result from multiple voxel analysis. So far, all proposed lesion-deficit mapping methods using dichotomized lesion variables have the same limitation (Bates et al 2003;Karnath et al 2004). Future work should address the impact of multiple comparison correction methods on effective coverage.…”