Further, expression of the Tat protein in transgenic animal models, without the presence of the virus itself or other viral proteins, tend to mirror the neuropathology and cognitive deficits observed in HIV-1 patients with HAND (Bruce-Keller et al. 2008; Carey et al. 2012; Fitting et al. 2010; Hauser et al. 2009; Kesby et al. 2014; Kesby et al. 2015; Marks et al. 2016; Maung et al. 2014; Mediouni et al. 2015; Paris et al. 2014a; Paris et al. 2014c; Toggas et al. 1994). Here, TAT is linked to HIV-associated neurocognitive disorder.