Processamento consciente, pré-consciente e subliminar

Surpreendentemente, o melhor desse artigo são suas quatro Boxes:

Box 1. Why attention and consciousness are different: top-down influences on subliminal processing (Por que a atenção e a consciência são diferentes: influências top-down sobre o processamento subliminar)
Box 2. Why does some knowledge remain permanently inaccessible? A hypothetical taxonomy (Por que algum conhecimento fica permanentemente inacessível?)
Box 3. Questions for further research (Questões para futuras pesquisas)
Box 4. ‘Phenomenal consciousness’ without reportability? ('Consciência fenomênica' sem reportabilidade?)

Na Box 1, os autores thinkful wishing pressupõem que o leitor conheça o efeito N400 dos ERPs (potenciais evocados). Para suprir um possível desconhecimento, coloquei abaixo duas citações sobre.
As figuras do artigo são de excelente qualidade gráfica e de conteúdo.

Conscious, preconscious, and subliminal processing: a testable taxonomy 2006
Stanislas Dehaene, Jean-Pierre Changeux, Lionel Naccache, Jerome Sackur and Claire Sergent

Abstract. Dos muitos eventos cerebrais evocados por um estímulo visual, quais são especificamente associados à percepção consciente, e quais meramente refletem o processamento não consciente? Diversos estudos recentes de neuroimagem contrastaram o processamento visual consciente e não consciente, mas seus resultados apresentam inconsistência. Alguns sustentam uma correlação da percepção consciente com eventos occipitais iniciais, outros com atividade parietofrontal tardia. Aqui, nós tentamos fazer sentido desses resultados conflitantes. Com base na hipótese do espaço de trabalho neuronal global, nós propomos uma taxonomia que distingue entre vigilância e acesso ao registro conciente, assim como entre processamento subliminar, pré-consciente e consciente. Sugerimos que essas distinções se mapeam sobre diferentes mecanismos neurais, e que a percepção consciente está sistematicamente associada a ondas de atividade parietofrontal que causam amplificação top-down.

N400

The ERP recorded from the scalp provides a continuous measure of brain electrical
activity with millisecond temporal resolution, and so it has been widely used to study language, for which timing is critical. Two components of the ERP elicited by words reflect comprehension difficulties. A negative voltage deflection peaking at about 400 ms after stimulus onset (N400) is small when a word is easily integrated with prior semantic context, but shows graded increases in amplitude as the prior context becomes less and less useful. A word like “sugar” will elicit no N400 at the end of a sentence like “I take my coffee with cream and...”, a medium-sized N400 at the end of a sentence like “At the store, I bought a pound of...” and a large N400 in “I finally asked my boss for a ...”3. The N400 offers a rapidly changing index of the ease or difficulty of semantic processing, beginning well before a spoken word is even completely pronounced.

The N400 is a negative polarity component, with a centroparietal maximum over the scalp, that emerges at about 250 ms after the onset of word stimulation and that reaches its maximal amplitude at roughly 400 ms. There is ample evidence that the N400 is sensitive to ongoing linguistic analyses. Generally speaking, every word elicits an N400. The particular latency and amplitude characteristics of the N400 depend on the context within which the eliciting word occurs, as well as on specific properties of the word itself (such as its frequency and form class). A large number of studies have shown that the N400 is particularly sensitive to semantic information processing, both in prime–target and in sentential contexts. The standard semantic priming RT effect is mirrored in the N400, where unrelated target words elicit a larger amplitude than related targets. This amplitude difference is referred to as the N400 effect.