showed a greater pathology compared to those with less expression of the mutant tau. Additionally, NFTs were clearly detected by immunoelectron microscopy at 4 months but not at 2 months. However, at both 2 and 4 months, pretangle-like structures were observed suggesting the NFT formation is not complete by 4 months and will continue to progress with time. Traumatic brain injury Preliminary research indicates that iron deposits due to hemorrhaging, following traumatic brain injury (TBI), may increase tau pathology. While TBI does not routinely lead to accelerated NFT formation, further work may determine if other blood components or factors unrelated to hemorrhages are involved in this TBI-induced augmentation of tau pathology. NFTs are most commonly seen associated with repetitive mild TBI as opposed to one instance of severe traumatic brain injury. For example, the neurodegenerative disease chronic traumatic encephalopathy (CTE), previously called dementia pugilistica, is highly associated with NFTs and neuropil threads. Aluminium The idea that there is a link between aluminium exposure and the formation of neurofibrillary tangles has floated around the scientific community for some time without having been definitively proved or disregarded. Recently a study examining the hippocampal CA1 cells from individuals with and without Alzheimer's disease showed a small portion of the pyramidal cells contain cytoplasmic pools within their somas containing early NFTs. These cytoplasmic pools are aggregates of an aluminium/hyperphosphorylated tau complex similar to mature NFTs. (Walton) While a connection between aluminium and NFTs and AD is maintained, there is evidence that aluminium does not directly cause the formation of NFTs or AD. However it is claimed that chronic aluminium intake can cause Alzheimer's by disrupting the microtubules in the filaments. Pathology It has been shown that the degree of cognitive impairment in diseases such as AD is significantly correlated with the presence of neurofibrillary tangles. Harmful or protective? There has been some suggestion that the formation of NFTs does not have a causal relationship with disease. Rather that NFTs may be produced in response to a variety of conditions and may in fact be a compensatory response against oxidative stress and serves a protective function. Several points are made to argue the position that NFTs are perhaps protective instead of harmful. First there appears to be a dispute as to the impact of neurofibrillary tangles on neuronal viability because some neurons containing NFTs survive for decades. Furthermore, NFTs have been found in apparently healthy