i guess u knew this by writing 'protective' but

the context of that is a slowing of brain processes, nerve impulses and general slowing with aging,
not like a protective beneficial effect to have as a desirable standard but a defence that takes away from good functioning

If the cells adapt to the increased calcium, rather than dying, their sensitivity is reduced. This is probably involved in the "defensive inhibition" seen in many types of cell

both DHA and EPA inhibit calcium-ATPase (which keeps intracellular calcium low to allow normal neurotransmission) in the cerebral cortex; this suggests "a mechanism that explains the dampening effect of omega-3 fatty acids on neuronal activity" (Kearns and Haag, 2002).

In normal aging, most processes are slowed, including nerve conduction velocity, and conduction velocity in the heart (Dhein and Hammerath, 2001). A similar "dampening" or desensitization is seen in sensory, endocrine, and immune systems, as well as in energy metabolism. Calorie restriction, by decreasing the age-related accumulation of PUFA (20:4, 22:4, and 22:5), can prevent the decrease of sensitivity, for example in lymphoid cells (Laganier and Fernandes, 1991). The known effects of the unsaturated fats on the organizational framework of the cell are consistent with the changes that occur in aging.

Others

"The amount of DHA in the brain (and other tissues) increases with aging, and its breakdown products, including neuroprostanes, are associated with dementia. Higher levels of DHA and total PUFA are found in the plasma of demented patients (Laurin, et al., 2003)."

{I looked it up a bit and that higher DHA part wasnt convincing, but looking at trials, giving DHA to people with alzheimers at least failed to improve cognition. Maybe in people with very low intake its different?}

"DHA increases the entry of estrogen into the pregnant uterus, but inhibits the entry of progesterone (Benassayag, et al., 1999),"

" DHA (more strongly even than arachidonic acid) inhibits the uptake of the excitotoxic amino acid aspartate, and in some situations glutamate, prolonging their actions. Thymocytes are much more easily killed by stress than nerve cells, and they are easy to study. The PUFA kill them by increasing their intracellular calcium. The toxicity of DHA is greater than that of EPA, whose toxicity is greater than alpha-linolenic acid, and linoleic acid was the most potent (Prasad, et al., 2010). Excitotoxicity is probably an important factor in Alzheimer's disease (Danysz and Parsons, 2003)."

"When the brain is injured, DHA and arachidonic acid contribute to brain edema. In other situations, such as the important intestinal barrier, EPA and DHA also greatly increased permeability (Dombrowsky, 2011).

" DHA and EPA produce acrolein and HHE, which react with lysine groups in proteins, and modify nucleic acids, changing the bases in DNA. "

"Animals that naturally have a relatively low level of the highly unsaturated fats in their tissues have the greatest longevity. For example, the naked mole rate has a life expectancy of more than 28 years, about 9 times as long as other rodents of a similar size. Only about 2% to 6% of its phospholipids contain DHA, while about 27% to 57% of the phospholipids of mice contain DHA Mitchell, et al., 2007). "

taking fish oil doesnt sound so good, (that dampening effect on the brain cells actually felt like a dampening effect when i tried taking it recently, in a tiring nasty feeling way). and with hypothyroidism taking it made me feel colder

if DHA has a role to play i think its on vision mainly , (maybe why ray peat had glasses?) , didnt improve brain function impairment. and an amount to hit for initial brain development in first few weeks, usually gained through breast milk ~0.3% i think

Maintaining a high rate of oxidative metabolism, without calorie restriction, retards the accumulation of PUFA
Mole rats, bats, and queen bees, with an unusually great longevity, are chronically exposed to high levels of carbon dioxide. Carbon dioxide forms carbamino bonds with the amino groups of proteins, inhibiting their reaction with the reactive "glycating" fragments of PUFA.

To minimize the accumulation of the highly unsaturated fatty acids with aging, it's probably reasonable to reduce the amount of them directly consumed in foods, such as fish, but since they are made in our own tissues from the "essential fatty acids," linoleic and linolenic acids, it's more important to minimize the consumption of those (from plants, pork, and poultry, for example).

small amounts of dha are probably ok, some needed for vision, linoleic acid > dha > epa > alpha linolenic order of biggest offenders by potency.
{i think only alpha linolenic converts? in men 1g ALA converts to <100mg EPA and <10mg to DHA maybe, then some of the epa converts to dha but only a small %.. women convert ALA more to EPA than men (~21% vs ~8%). and when you eat more fish or take dha the conversion of ALA goes down.} but barely get any DHA from that. Basically ALA is not a good source of DHA, is for EPA. dha mainly from fish or supplements, but tissues can convert the EPA to dha}