The hippocampus has long been proposed to play a critical role in novelty detection through its ability to act as a comparator between past and present experience. A recent study provided evidence for this hypothesis by characterizing hippocampal responses to sequence novelty, a type of associative novelty where familiar items appear in a new temporal order. Here, we ask whether a hippocampal m...

— The capacity of an order-d associative memory model is O(N d /logN) where N is the memory size in bit. In contrast, the capacity of the Hopfield network is limited to O(N/logN). Among higher order associative memory models (d > 1), the second order memory (d = 2) has attractive properties: a relatively small implementation cost of O(N 2), a small number of spurious states, and the presence of...

Episodic memory involves flexible retrieval processes that allow us to link together distinct episodes, make novel inferences across overlapping events, and recombine elements of past experiences when imagining future events. However, the same flexible retrieval and recombination processes that underpin these adaptive functions may also leave memory prone to error or distortion, such as source ...

I challenge the dominant understanding of what it means to say two thoughts are associated. The two views that dominate the current literature treat association as a kind of mechanism that drives sequences of thought (often implicitly so). The first, which I call reductive associationism, treats association as a kind of neural mechanism. The second treats association as a feature of the kind of...

Food avoidance learning in the mollusc Pleurobranchaea entails reduction in the responsiveness of key brain interneurons in the feeding neural circuitry, the paracerebral feeding command interneurons (PCNs), to the neurotransmitter acetylcholine (AcCho). Food stimuli applied to the oral veil of an untrained animal depolarize the PCNs and induce the feeding motor program (FMP). Atropine (a musca...

General knowledge acquisition entails the extraction of statistical regularities from the environment. At high levels of complexity, this may involve the extraction, and consolidation, of associative regularities across event memories. The underlying neural mechanisms would likely involve a hippocampo-neocortical dialog, as proposed previously for system-level consolidation. To test these hypot...

The purines, ATP and adenosine, control the rundown and termination of swimming in the Xenopus embryo. This intrinsic purinergic modulation, unavoidably present during every swimming episode, could lead to stereotyped inflexible behavior and consequently could jeopardize the survival of the embryo. To explore whether this control system can exhibit adaptability, I have used a minimal simulation...

Although a wealth of data have elucidated the structure and physiology of neuronal circuits, we still only have a very limited understanding of how behavioral learning is implemented at the network level. An emerging crucial player in this implementation is disinhibition--a transient break in the balance of excitation and inhibition. In contrast to the widely held view that the excitation/inhib...

Calculations of the desorption of hydrogen from Pt(110)-(1×2), a surface used to model nanoparticle edge sites, show the activation energy varying strongly with hydrogen coverage, from 0.8 to 0.3 eV. The predicted temperature programed desorption spectra agree well with experiments, but the formation of the hydrogen molecules occurs only at two types of sites on the surface even though three pe...