The interthalamic adhesion (IA) is a structure that connects the median borders of both thalami across the third ventricle. Given that it is difficult to identify on routine neuroimaging, its anatomical variants and function remain poorly studied. The objective of this study was to clarify the role of the IA on cognition. The study comprised 42 healthy subjects and a cohort of 40 patients with isolated thalamic strokes at the chronic stage. All participants underwent 3T research T1w and FLAIR MRI as well as a neuropsychological assessment. The presence, absence, type of anatomical variant, and lesion of an IA were assessed. 76% of participants had an IA, with a higher prevalence among women (92%) than men (61%). The presence or absence of an IA did not affect the neuropsychological performance of healthy subjects nor did the type of IA variant. Across all tests, patients without an IA (n=10, BF10=10648) performed more poorly versus healthy subjects than patients with an IA (n=18, BF10=157) using a Bayesian rmANOVA (Fig. 1A, B). Those deficits were more pronounced on verbal memory or Stroop task (Fig. 1C, D). This effect was not explained by age, infarct laterality, volume, or localization of lesions. Patients with a lesioned IA (n=12) presented a similar trend to patients without an IA, which could however be explained by a greater volume of lesions. Thus, the IA does not appear to have a major role in cognition for healthy subjects but could play a compensatory role in patients with thalamic lesions.