Neural Anatomy of Primary Visual Cortex Limits Visual Working Memory
Despite the immense processing power of the human brain, working memory storage is severely limited, and the neuroanatomical basis of these limitations has remained elusive. Here, we show that the stable storage limits of visual working memory for over 9 s are bound by the precise gray matter volume of primary visual cortex (V1), defined by fMRI retinotopic mapping. Individuals with a bigger V1 tended to have greater visual working memory storage. This relationship was present independently for both surface size and thickness of V1 but absent in V2, V3 and for non-visual working memory measures. Additional whole-brain analyses confirmed the specificity of the relationship to V1. Our findings indicate that the size of primary visual cortex plays a critical role in limiting what we can hold in mind, acting like a gatekeeper in constraining the richness of working mental function.
The effects of very early Alzheimer’s disease on the characteristics of writing by a renowned author
Iris Murdoch (I.M.) was among the most celebrated British writers of the post-war era. Her final novel, however, received a less than enthusiastic critical response on its publication in 1995. Not long afterwards, I.M. began to show signs of insidious cognitive decline, and received a diagnosis of Alzheimer’s disease, which was confirmed histologically after her death in 1999. Anecdotal evidence, as well as the natural history of the condition, would suggest that the changes of Alzheimer’s disease were already established in I.M. while she was writing her final work. The end product was unlikely, however, to have been influenced by the compensatory use of dictionaries or thesauri, let alone by later editorial interference. These facts present a unique opportunity to examine the effects of the early stages of Alzheimer’s disease on spontaneous written output from an individual with exceptional expertise in this area. Techniques of automated textual analysis were used to obtain detailed comparisons among three of her novels: her first published work, a work written during the prime of her creative life and the final novel. Whilst there were few disparities at the levels of overall structure and syntax, measures of lexical diversity and the lexical characteristics of these three texts varied markedly and in a consistent fashion. This unique set of findings is discussed in the context of the debate as to whether syntax and semantics decline separately or in parallel in patients with Alzheimer’s disease.
"I’ve sold fish in the market for the last thirty years, because I never had the chance to go to university. Recently my daughter graduated from Makerere, which is one of the best schools in the country. When I walked through the gates to attend her graduation, I felt so happy, because I never thought I’d see the inside of a university."
I'm that one person attending a university doing that one thing persons attending universities do. I love art (mostly photography) and science (bio-medicine) and my inability to choose between the two puts me too far behind my peers.
Humour is cool. If we can laugh over anything, we can be peas in a pod.
Some things I fancy with my cup of tea: more tea, Fringe, rain, LOTR, HP, Avatar: the Last Airbender & LOK, silence, seas, lanky people, Paul Davey, lonely forests, Sigur Ros, Burberry, stormy weather, The Hold Steady, Fever Ray, humourous things, and naked people. I'm quite serious about the naked people bit, you'll most likely see your fair share of them on here.
Anything worth reading is under adventures/misadventures.