Brain localization for arbitrary stimulus categories: a simple account based on Hebbian learning.

A central theme of cognitive neuroscience is that different parts of the brain perform different functions. Recent evidence from neuropsychology suggests that even the processing of arbitrary stimulus categories that are defined solely by cultural conventions (e.g., letters versus digits) can become spatially segregated in the cerebral cortex. How could the processing of stimulus categories that are not innate and that have no inherent structural differences become segregated? We propose that the temporal clustering of stimuli from a given category interacts with Hebbian learning to lead to functional localization. Neural network simulations bear out this hypothesis.

Learning about categories in the absence of memory.

A fundamental question about memory and cognition concerns how information is acquired about categories and concepts as the result of encounters with specific instances. We describe a profoundly amnesic patient (E.P.) who cannot learn and remember specific instances--i.e., he has no detectable declarative memory. Yet after inspecting a series of 40 training stimuli, he was normal at classifying novel stimuli according to whether they did or did not belong to the same category as the training stimuli. In contrast, he was unable to recognize a single stimulus after it was presented 40 times in succession. These findings demonstrate that the ability to classify novel items, after experience with other items in the same category, is a separate and parallel memory function of the brain, independent of the limbic and diencephalic structures essential for remembering individual stimulus items (declarative memory). Category-level knowledge can be acquired implicitly by cumulating information from multiple training examples in the absence of detectable conscious memory for the examples themselves.

Counter bond, 1724/5 January 22

Handwritten counter bond between Samuel Whittemore and Andrew Bordman, securing Whittemore's loan from Nathaniel Hancock and James Reade.

Counter bond, 1728 June 5

Handwritten counter bond between Francis Foxcroft and Jonathan Remington, securing Foxcroft's loan from Andrew Bordman.

Counter bond, 1731 August 4

Handwritten counter bond between Stephen Palmer and Samuel Whittemore, and Edward Hutchinson, securing Stephen Palmer and Samuel Whittemore's loan from William Brattle and Andrew Bordman.

Il cielo stellato sopra di me e la legge morale in me. Osservazioni sul sublime e sulla logica dell’irrazionale in Kant

«Duas coisas enchem o ânimo de uma admiração e veneração sempre nova e tanto mais crescente quanto mais frequente e mais demoradamente a reflexão se ocupa delas: o céu estrelado acima de mim e a lei moral em mim.” Com estas famosíssimas palavras escritas no papel e incisas em pedra, Immanuel Kant conclui a Crítica da razão prática. No presente artigo pretendo mostrar como esta frase está estreitamente ligada: 1) à doutrina kantiana do sublime e 2) à fundação da lógica do irracional na Critica do Juízo.